Anatomy Flashcards

Question

Abdominal Cavity

Answer 1

The abdominal cavity contains all the organs of the reproductive and urinary systems, as well as the stomach and intestinal tract.

Answer 2

Lines the abdominal cavity and it's organs. This peritoneum has two layers with a theoretical space much like the thoracic cavity.

Answer 3

Order Artiodactyla—Includes the even-toed hoofed mammals, like pigs, cows, sheep, and goats (two hooves per limb)

Answer 4

Order Perissodactyla—Includes the odd-toed hoofed mammals, like horses (one hoof per limb)

Answer 5

Canis familiaris

Answer 6

Felis domesticus

Answer 7

Equus caballus

Answer 8

Epithelial, connective, nervous, Muscle

Answer 9

Imaginary vertical or horizontal lines drawn through a body to describe a structure's location and body movements

Answer 10

the physiological processes that keep a body in equilibrium

Answer 11

near the shoulder, dorsal, where the horn of a saddle is

Answer 12

The trunk, formed by rib cage and abdomen

Answer 13

lateral surface of the abdomen between the last rib and the hind legs

Answer 14

At the base of the neck, between the front legs that covers the cranial end of the sternum

Answer 15

top of the head between the ears

Answer 16

upper and lower part of jaws

Answer 17

upper arm, area of thoracic limb, between the elbow and shoulder

Answer 18

joint between the femur and tibia, in back leg (in humans, the knee)

Answer 19

along the tibia

Answer 20

tarsus (hind limb, "ankle")

Answer 21

front leg, metacarpal/metatarsal bone of hoofed animals

Answer 22

joint between cannon bone and proximal phalanx of hoofed animals

Answer 23

are of proximal phalanx of hoofed animals (distal of fetlock)

Answer 24

joint composed of the carpal bones. referred to as the knee of the horse and wrist of humans

Answer 25

``` major structures • digestive organs • urinary organs •reproductive organs ```

Answer 26

inflammation of the thoracic cavity

Answer 27

inflammation of abdominal cavity

Answer 28

the result when structures or functions of the body become abnormal

Answer 29

a state of normal anatomy and | physiology

Answer 30

tissue made up of cells and extracellular substances that connect and support cells and other tissues

Answer 31

first step in healing process when body is injured. "clean up" of damaged area

Answer 32

striated, voluntary muscle that enables movement, moves bones and under conscious control

Answer 33

dorsal part of base of tail

Answer 34

last, most caudal sternebra

Answer 35

complex carbohydrates with many sugar monomers that form chains or branches. Examples include glycogen, starch, and cellulose.

Answer 36

are short chains of sugar monomers covalently bonded together. If they contain only two sugar monomers, they're known as disaccharides. Examples of disaccharides are lactose (milk sugar) and sucrose (table sugar).

Answer 37

are simple sugars composed of only one monomer. Examples are glucose, fructose, and ribose.

Answer 38

carbohydrates

Answer 39

occurs when there's a weak attraction between a slightly negative atom in a polar covalent bond and a slightly positive hydrogen atom involved in a second polar covalent bond.

Answer 40

are important in many biochemical processes. Examples are sodium chloride and calcium phosphate

Answer 41

minerals that carry an electric charge. They are salts

Answer 42

When dissolved in water, acids release hydrogen ions, contain ionic bonds and are electrolytes

Answer 43

bases release hydroxyl ions. contain ionic bonds and are electrolytes

Answer 44

occurs when atoms either donate or accept electrons from another atom. The atom that donates an electron becomes positively charged, while the atom that gains an electron becomes negatively charged. The two atoms, which now have opposite electrical charges, are attracted to each other and stay together as a result.

Answer 45

atoms that participate in ionic bond are referred to as ions. When ionic bonds form between mineral compounds, the resulting compounds are salts.

Answer 46

Negatively charged ions are called anions

Answer 47

An ion that has a positive charge

Answer 48

when atoms either donate or accept electrons from another atom.

Answer 49

Occurs when two atoms each have an unpaired electron in their outer orbitals. Each atom exerts a force on the unpaired electron of the other, pulling them together. The unpaired electrons are then shared between the two atoms. This sharing of electrons may be equal between the two atoms, producing what's called a nonpolar bond. It may also be unequal, causing one end of the molecule to have a slight positive charge and the other end to have a slight negative charge.

Answer 50

Unequal electron sharing produces a polar covalent bond. The bonds that hold the atoms of a water molecule together are polar covalent bonds

Answer 51

form enzymes and hormones and control all metabolic and biochemical reactions and processes in cells. Proteins are composed of chains of amino acids joined by peptide bonds.

Answer 52

A protein. There are 20 different amino acids in the body, all of which contain a carbon atom bound to an amino group, a carboxyl group, and a side chain (designated R)

Answer 53

1) highly specific sequence of amino acids in each type of protein 2) formed by hydrogen bonds at intervals along the length of the amino acid chain that cause it to coil or bend. 3) Bonding of certain amino acids causes further bending and looping of the protein 4) when hydrogen bonds or bonds between R groups join two or more polypeptide chains together

Answer 54

DNA provides a template for the manufacture proteins. Cells differ, depending on which proteins are made by that particular cell. The genes within the DNA molecule control synthesis of proteins. The process of transcribing and translating the genetic message into a protein requires the molecule ribonucleic acid (RNA).

Answer 55

known as triglycerides, are the most abundant lipids in the body and provide more than twice the energy of complex carbohydrates when they're broken down. Triglycerides are made up of three fatty acids (a combination of saturated and unsaturated) and glycerol. Saturated fatty acids are found in butter and lard. Unsaturated fatty acids are derived from plants, such as corn oil and olive oil.

Answer 56

made up of two fatty acids, glycerol and a phosphate group. Phospholipids are made up of both hydrophobic and hydrophilic ends which shapes them into two layers, called a lipid bilayer, when surrounded by water.

Answer 57

A type of hydrophobic lipid. Examples of steroids include cortisone, estrogen, progesterone, and testosterone.

Answer 58

made up of 20 fatty acids in a ring structure. These help to mediate complex chemical processes in the body.

Answer 59

The phosphate bonds of ATP contain energy that's released when enzymes break off ATP's outer phosphate group and attach it to another molecule

Answer 60

Small organic compounds that contain one or more phosphate groups and a five-carbon sugar attached to a nitrogenous base

Answer 61

either single (as in RNA) or double (as in DNA) strands of covalently bonded nucleotides.

Answer 62

Atoms that contain different neutrons (atomic mass) from the protons (atomic number)

Answer 63

smallest particle of a substance, composed of 2 or more atoms, that retains properties of the substance

Answer 64

A component that is present in the greatest amount in a mixture

Answer 65

Tiny particles in a mixture that do not settle or scatter light (mineral water)

Answer 66

Solute particles in a mixture that are larger and scatter light, but do not settle out (jello)

Answer 67

Solute particles in a mixture that are very large and settle out and may scatter light (red blood cells)

Answer 68

weak bonds that unite hydrogen with oxygen or nitrogen

Answer 69

constructive processes

Answer 70

destructive processes

Answer 71

synthesis, decomposition, exchange

Answer 72

Contain carbon covalent bonds (CC or CH) and are large and complex

Answer 73

Don't contain CC or CH bonds, tend to be ionic and are small

Answer 74

specific groups of atoms within molecules that are responsible for the chemical reactions of those molecules

Answer 75

Water is a universal solvent. Water is an idea transport medium. Water has a high heat capacity and high heat vaporization. Water is used for lubrication.

Answer 76

. A peptide is a molecule consisting of two or more amino acids in which the carboxyl group of one acid is linked to the amino group of the other.

Answer 77

essential nutrient for all life functions. Is a sugar. Quick source of energy and may be stored as glycogen. consist of carbon, hydrogen, and oxygen in a 1:2:1 ratio

Answer 78

Lipids are used in the body for energy and are stored in fat for future energy needs. Lipids also serve as chemical messengers in the form of some hormones. Essential nutrient for life. They're composed of fatty acids attached to glycerol.

Answer 79

Enzymes speed up or catalyze chemical reactions without being destroyed or altered. Enzymes are specific to the reaction they catalyze and the substrates (the substances they act upon) they use.

Answer 80

Also called plasma membrane or plasmalemma. All cells have this.

Answer 81

Has cytosol a colloid protoplasm that is highly structured and composed of proteins, electrolytes and metobolites, a flexible cytoskeleton and organelles

Answer 82

complex structures in cells that work collaboratively to carry out metabolic functions of cells.

Answer 83

responsible for cell membrane function

Answer 84

occur within the entire width bilayer of the cell membrane, they all select substances to enter and leave the cell. Some act as pores letting water pass through

Answer 85

bound to the inside or outside surfaces of cell membranes they may act as enzymes to catalyze specific chemical reactions and changing cell shape

Answer 86

sugar coating found on outside of cell, formed by sugar groups attaching to proteins and lipids on the outer surface of the cell membrane

Answer 87

Glycoproteins that cover the surface of almost all mammal cells, they all cells to bond to extracellular molecules and each other

Answer 88

small invaginations of the plasma membrane often pinch off and migrate inside the cell to form tiny vesicles.

Answer 89

Where cilia and flagella originate, formed from a pair of centrioles

Answer 90

hollow cylinder inside the cell, composed of protein subunits and responsible for breaking down mislabeled or abnormal protein molecules

Answer 91

membrane bound vesicle containing enzymes, produced by fission, which detoxifies various molecules such as alcohol and formaldehyde

Answer 92

Cytosol is the protoplasm of the cell. It is a viscous, semitransparent liquid composed of dissolved electrolytes, amino acids, and simple sugars. Proteins are also suspended in the cytosol and give it its thick, jellylike consistency.

Answer 93

The mitochondrion produces 95% of the energy that fuels cellular activity. The energy is predominantly stored in the terminal phosphate bond of adenosine triphosphate (ATP) molecules. The ATP is derived from an array of biochemical processes using oxygen and nutrient molecules. Oxygen enters the body via respiration, and nutrient molecules are provided from food sources. Remarkably, mitochondria contain their own DNA, which includes the instructions for making the enzymes used to make ATP.

Answer 94

The ribosome is the site of protein synthesis. Soluble protein intended for intracellular use is manufactured on free-floating ribosomes found throughout the cytosol, whereas protein intended for export outside the cell is synthesized on fixed ribosomes found on the rough endoplasmic reticulum (RER). Newly manufactured molecules of protein are moved internally into passageways in the RER known as cisternae, Latin for “reservoirs.” Here the proteins are modified before being moved on to the Golgi apparatus for further modification and packaging. The membrane of the RER is an extension of the outer nuclear membrane, so that RER is often found near the nucleus.

Answer 95

Smooth ER, which is connected to rough ER, is active in the synthesis and storage of lipids, particularly phospholipids and steroids, and is therefore seen in large quantities in gland cells. In liver cells smooth ER may also function to eliminate drugs and break down glycogen into glucose.

Answer 96

The Golgi apparatus acts as a modification, packaging, and distribution center for molecules destined for either secretion or intracellular use. It also functions in polysaccharide synthesis and in the coupling of polysaccharides to proteins (glycoproteins) on the cell surface.

Answer 97

The lysosome’s principal responsibilities are the breakdown of nutrient molecules into usable smaller units and the digestion of intracellular debris. Lysosomes may also release their enzymes outside the cell to assist with the breakdown of extracellular material. In addition, lysosomal digestion is responsible for decreasing the size of body tissues (for example, shrinkage of the uterus after parturition and atrophy of muscles in paralyzed animals).

Answer 98

Peroxisomes are commonly found in liver and kidney cells and are important in the detoxification of various molecules. Peroxisomes contain enzymes that use oxygen to detoxify a number of harmful substances, including alcohol and formaldehyde. They also assist in the removal of free radicals, which are normal products of cellular metabolism that can be harmful to the cell in large quantities because they interfere with the structures of proteins, lipids, and nucleic acids.

Answer 99

Proteasomes are minute structures that consume individual, often misfolded proteins and digest them. They are found throughout the cytosol.

Answer 100

Vaults are tiny, hollow transport complexes that are thought to attach to fibers in the cytoskeleton that enable rapid movement from one part of the cell to another. Vaults are able to open up and may lock into nuclear pore complexes on the nucleus, where they may pick up and drop off molecules.

Answer 101

. Fluid compartments in the body include: intracellular, interstitial, and intravascular.

Answer 102

The diffusion of molecules across the cell membrane with help from carrier proteins. It requires ATP and can't be done through simple diffusion

Answer 103

Force of water moving from on side of a membrane to the other

Answer 104

Difference between osmotic pressure of blood and osmotic pressure of interstitial fluid or lymph

Answer 105

the force that pushes a liquid (blood pressure)

Answer 106

An electrolyte is a charged particle (an anion or a cation) capable of conducting an electric current in solution.

Answer 107

Measurement of solute concentration in fluids

Answer 108

. Molecular size: Very small molecules, such as water (H2O), may pass through cellular membrane pores (approximately 0.8 nm in diameter), but larger molecules, such as glucose, cannot. 2. Lipid solubility: Lipid-soluble molecules (e.g., alcohol and steroids) and dissolved gases (e.g., oxygen [O2] and carbon dioxide [CO2]) can pass through the lipid bilayer with ease, whereas other molecules may not. 3. Molecular charge: Ions are small, but their charge prevents easy passage through the membrane pores. Specialized pores called channels selectively allow certain ions to pass through but not others.

Answer 109

. Epithelial cells are polar: that is, they have a sense of direction relative to surrounding structures. Each epithelial cell has an apical surface and a basal surface, which are quite different from each other. The apical surface is the side of the cell that faces the lumen or body cavity, and the basal surface is the side of the cell that faces the underlying connective tissue. 2. Epithelial cells have lateral surfaces that are connected to neighboring cells by junctional complexes. These junctions bring the cells into close apposition to one another, leaving little room for extracellular matrix. The matrix that surrounds epithelia therefore exists in very small quantities, if at all. 3. All epithelial cells lack blood vessels or capillaries. They are avascular and rely on underlying connective tissue to provide oxygen and nutrients. 4. Although some epithelia lack nerves (for example, those in the stomach, intestines, and cervix), most epithelial cells are innervated and provide valuable sensory input.

Answer 110

Tight junction: formed by the fusion of the outermost layers of the plasma membranes of adjoining cells. The matrix-filled space between cells is lost at the site of a tight junction. For centrally placed cells, the fusion occurs as a strip that wraps around the entire circumference of the cell like a belt. In this way, an impenetrable barrier is formed that prevents the passage of substances from the luminal end to the basal end of the cell and vice versa. Only by passing through the body of the cell can substances pass through the epithelial layer. Tight junctions are found in tissues in which there can be no leaks—for example, in the urinary bladder, where urine is held, or in the digestive tract, where tight junctions play a critical role in preventing the leakage of digestive enzymes into the bloodstream. 2. Desmosome: strong, welded plaque that connects the plasma membranes of adjacent cells. The bond is a mechanical coupling formed by filaments that interlock with one another, just as plastic fibers do in Velcro. Tonofilaments, or intermediate filaments, may also extend from the desmosomic plaque into the cytoplasm of each cell like anchors, forming stabilizing bases for the membrane junction. In this way, desmosomes form tough bonds between cells and therefore are found most commonly in tissues that undergo repeated episodes of tension and stretching, such as the skin, heart, and uterus. 3. Hemidesmosome: junctions that look like half-desmosomes and link epithelial cells to the basement membrane. 4. Gap junction: made of tubular channel proteins called connexons and extends from the cytoplasm of one cell to the cytoplasm of another. These transmembrane proteins allow the exchange and passage of ions and nutrients (e.g., nucleotides, sugars, and amino acids) from one cell to another. Gap junctions are most commonly found in intestinal epithelial cells, the heart, and smooth muscle tissue. The function of gap junctions in epithelial cells is not yet fully understood, but their ability to quickly transport electrical signals from one cell to another explains their presence in cardiac and smooth muscle cells, where they help coordinate contraction.

Answer 111

Simple squamous epithelium can be found in the inner lining of the lung and in the filtration membranes of kidneys

Answer 112

Simple cuboidal epithelium can be found on the surface of ovaries; in the secretory portions of glands, such as the thyroid; and in the lining of the ducts of the liver, pancreas, kidney, and salivary gland.

Answer 113

Simple columnar epithelium is found lining the length of the gastrointestinal tract from the stomach to the rectum.

Answer 114

Stratified squamous epithelium is found lining the mouth, esophagus, vagina, and rectum.

Answer 115

Pseudostratified columnar epithelium is found in the respiratory tract and in portions of the male reproductive tract.

Answer 116

• Transitional epithelium is found in portions of the urinary tract where great changes in volume occur (urinary bladder, ureters, urethra, and calyxes of the kidney).

Answer 117

Endocrine glands do not have ducts or tubules, and their secretions are distributed throughout the body. They produce and secrete regulatory chemicals known as hormones into the bloodstream or the lymphatic system, where they are carried to many regions of the body. The pituitary gland in the brain and the adrenal gland near the kidney are examples of endocrine glands.

Answer 118

Exocrine glands possess ducts. They are more common than endocrine glands and act by discharging secretions through their ducts directly into local areas, where they may cover cell surfaces or empty into body cavities. The secretions of exocrine glands act locally and do not normally enter the circulation. Examples include hepatoid, musk, sweat, and salivary glands. Exocrine glands in the liver secrete bile. The pancreas has both endocrine and exocrine glands

Answer 119

The goblet cell is a modified columnar epithelial cell found interspersed among the columnar cells of the respiratory and digestive tracts and in the conjunctiva of the eye. Goblet cells secrete mucin, a thick, sticky mixture of glycoproteins and proteoglycans. When combined with water, mucin becomes mucus.

Answer 120

Extracellular fibers, ground substance, and cells

Answer 121

1. Forms metabolic and structural connections between other tissues. 2. Forms a protective sheath around organs. 3. Helps insulate the body. 4. Acts as a reserve for energy. 5. Provides the frame that supports the body. 6. Composes the medium that transports substances from one region of the body to another. 7. Plays a vital role in the healing process and in the control of invading microorganisms

Answer 122

(GAGs) are the ground substance in soft connective tissue. They are made of unbranched chains of glycoproteins. Animals with joint injuries are sometimes given GAGs because they may help with joint healing. Joints contain hyaluronic acid, which is the most commonly found GAG in connective tissue. GAGs are large molecules that help to orient the formation of fibers within the tissue during healing.

Answer 123

Three types of dense connective tissue are cartilage, bone, and blood. Cartilage is similar to connective tissue proper in that it is composed of cells, fibers, and matrix. It is different in that it is more rigid than dense connective tissue. Bone is similar to connective tissue proper in that it is also composed of cells, fibers, and matrix; however, bone is much more dense. In fact, it is the hardest, most rigid type of connective tissue. Blood is similar in that it has a matrix, plasma, a fibrous component that is visible when blood clots, and cells. It is different in that it is almost always fluid but can clot when necessary.

Answer 124

1. Hyaline cartilage: Hyaline cartilage is the most common type of cartilage in the body. It is composed of closely packed collagen fibers that make it tough but more flexible than bone. Macroscopically, hyaline cartilage resembles a blue-white, frosted ground glass. It is found in the growth plates of long bones, where it supports continued bone development and the extension of bone length. Hyaline cartilage is the most rigid type of cartilage and is enclosed within a perichondrium. 2. Elastic cartilage: Elastic cartilage is similar to hyaline cartilage but contains an abundance of elastic fibers, which form dense branching bundles that appear black microscopically. Elastic cartilage is found in the epiglottis of the larynx and in the pinnae (external ears) of animals. 3. Fibrocartilage: Fibrocartilage usually is found merged with hyaline cartilage and dense connective tissue. Like hyaline cartilage, it contains thick bundles of collagen fibers, but it has fewer chondrocytes and lacks a perichondrium. Fibrocartilage is found in the spaces between vertebrae of the spine, between bones in the pelvic girdle, and in the knee joint.

Answer 125

Skeletal muscle cells are striated, or striped, because histologically they have alternating bands of light and dark. Unlike cardiac and smooth muscle, skeletal muscle is usually controlled through conscious effort and therefore is called voluntary muscle. (In other words, the animal can control its movement through conscious thought.) Thus skeletal muscle is striated voluntary muscle. Smooth muscle is composed of small, spindle-shaped cells that lack striations or bands and therefore appear “smooth.” Like skeletal muscle, smooth muscle may be stimulated to contract by the action of nerves, but unlike skeletal muscle, the contractions cannot be consciously controlled. Smooth muscle is therefore nonstriated involuntary muscle. Cardiac muscle exists only in the heart and possesses the remarkable ability to contract even when neural input has been altered. Specialized pacemaker cells within the heart muscle supply the signal for the heart to contract at regular intervals. This input is entirely involuntary and is responsible for initiating the pumping force that propels blood through blood vessels. Cardiac muscle is striated involuntary muscle

Answer 126

Two basic types of neural tissue are neurons and supporting neuroglial cells.

Answer 127

The periople itself can be seen as the thin membrane that grows from the outer edge of the coronary band and down the hoof wall.

Answer 128

Fiber-like protein that gives skin flexibility

Answer 129

Skin layer where fat is stored

Answer 130

``` stratum basale. The stratum spinosum The stratum granulosum The stratum lucidum The stratum corneum ```

Answer 131

These layers are the stratum basale, stratum spinosum, and stratum corneum.

Answer 132

Anagen is the active phase of the hair. The cells in the root of the hair are dividing rapidly. A new hair is formed and pushes the club hair (a hair that has stopped growing or is no longer in the anagen phase) up the follicle and eventually out.

Answer 133

The catagen phase is a transitional stage and about 3% of all hairs are in this phase at any time. This phase lasts for about two to three weeks. Growth stops and the outer root sheath shrinks and attaches to the root of the hair. This is the formation of what is known as a club hair.

Answer 134

Telogen is the resting phase and usually accounts for 6% to 8% of all hairs. This phase lasts for about 100 days for hairs on the scalp and longer for hairs on the eyebrow, eyelash, arm, and leg. During this phase, the hair follicle is completely at rest and the club hair is completely formed

Answer 135

Blood flow to the area is increased, which in turn causes the clinical signs of heat and redness. Blood flow also increases the supplies of oxygen and nutrients to the active cells of the damaged tissue. Plasma fluid, composed of enzymes, antibodies, and proteins, pours into the affected area, causing swelling of the soft tissue structures. This swelling irritates delicate nerve endings and causes pain and tenderness in the affected area. Clot formation begins to take place, which slows bleeding. The clot also helps isolate the wound from the invasion of pathogens and helps prevent bacteria and toxins from spreading to surrounding soft tissue structures. A clot first forms when platelets become sticky and clump together. Fibrinogen, found in rich quantities in the swollen tissue, is converted to an insoluble protein called fibrin. Fibrin is woven into a netlike structure that surrounds the platelets and provides support and stability to the newly formed clot. It also forms a framework to support the movement of cells throughout the site. Clots that form on the skin eventually dry and become known as scabs. Large cells, such as macrophages and neutrophils (types of white blood cells), move through blood vessels and can squeeze through dilated capillaries to assist in the removal of debris and microinvaders. The phagocytic cells are short lived, however, and can function for only a few hours before dying. Pus, which is an accumulation of dead and degenerated neutrophils and macrophages, may therefore collect in the injured area. With increased blood flow, histamine and heparin are dispersed, and their levels drop in the affected area. The decrease in these molecules causes the return of normal capillary size and permeability. When capillaries return to normal size, blood flow and fluid leakage into the affected area abate. Swelling, heat, and redness begin to subside. To sum up the sources of the clinical signs accompanying inflammation: Heat and redness are caused by increased blood flow to the area. Swelling is caused by fluid from plasma, composed of enzymes, antibodies, and proteins, pouring into the affected area. This swelling irritates delicate nerve endings and causes pain and tenderness in the affected area.

Answer 136

Granulation tissue is a bright pink tissue that forms as macrophages work to clear debris from beneath the overlying blood clot or scab. Composed of a layer of collagen fibers manufactured by fibroblasts, granulation tissue is richly infiltrated with small permeable capillaries that have branched off existing capillaries in the deeper layers of the damaged tissue. These new tiny vessels push up into the bed of collagen fibers and provide rich supplies of nutrients and oxygen to hard-working cells such as fibroblasts, macrophages, and neutrophils. Macroscopically, the capillaries appear to be minute granules and are therefore called “granulation tissue.” Granulation tissue keproduces bacteria-inhibiting substances, making it highly resistant to infection.

Answer 137

As older cells travel from the basal to the superficial layers, they undergo profound changes: they fill with keratohyalin granules; lose their nuclei, cytosol, and organelles; and ultimately become lifeless sheets of keratin

Answer 138

These layers are the stratum basale, stratum spinosum, and stratum corneum.

Answer 139

Soft, horny covering at the proximal end of the hoof wall

Answer 140

Type of sweat gland - unlike eccrine sweat glands, apocrine glands empty into hair follicles rather than onto the surface of the skin. In the dog, apocrine glands are located in the external ear canal.

Answer 141

Skin layer where fat is stored

Answer 142

Fiber-like protein that gives skin flexibility

Answer 143

Skin layer with collagen

Answer 144

The wall, sole and frog

Answer 145

anagen, catagen, and telogen.

Answer 146

It covers and contains body parts It protects against excessively humid or dry conditions. It protects against environmental chemicals. It protects against infectious organisms, such as bacteria, viruses, fungi, and parasites. It helps regulate body temperature.

Answer 147

The deepest layer of the epidermis is the basal layer, called the stratum basale. This layer consists of a single layer of columnar to cuboidal cells. These cells are actively dividing, giving birth to the cells that are pushed upward to form the upper layers of the epidermis. Three types of cells exist in the stratum basale. The most common cell is the keratinocyte, which produces keratin. The second cell type is the melanocyte, a cell that makes melanin. Melanocytes are less common, and the number of melanocytes varies depending on the color of that area of skin. Dark skin contains more melanocytes than light skin. The Merkel cell is associated with nerve endings. Merkel cells with nerve endings make up the Merkel disc. This disc is what allows for the sensation of touch.

Answer 148

Second deepest layer - The stratum spinosum (the prickle-cell layer). The stratum spinosum (spiny layer) is so named because when the cells of this epidermal layer are fixed for histologic exam, they contract into speculated masses that resemble sea urchins. It contains several layers of cells that are held together by desmosomes.

Answer 149

The stratum granulosum (granular layer) is the middle layer of skin. Composed of two to four layers of flattened, diamond-shaped keratinocytes, the stratum granulosum is the highest level of the epidermis where living cells can be found. The cytoplasm of these cells begins to fill with keratohyalin and lamellated granules, which in turn leads to the dramatic degeneration of the nucleus and other organelles. Without these vital parts, the cell quickly dies. The lamellar granules contain waterproofing glycolipids and are transported to the periphery of the cell, where their contents are discharged into the extracellular space. These glycolipids play an important role in waterproofing the skin and slowing water loss across the epidermis.

Answer 150

The second layer from the surface is the clear layer, called the stratum lucidum. Cells in the stratum lucidum are also dead and completely keratinized. These cells lack a nucleus and other cell organelles. Because these cells look very similar to the cells of the stratum corneum, you would have difficulty seeing this as a distinct layer, except in the skin of the nose and footpads.

Answer 151

The outermost layer of the epidermis is the horny layer, called the stratum corneum. This layer consists of dead, flattened, fully keratinized cells. The stratum corneum may be several layers thick. It's the first line of defense against attack by the environment or infectious organisms. This is the layer that constantly sheds cells into the environment. When the skin continuously sheds cells, bacteria, other infectious agents, and parasites are shed along with the cells. This process makes it difficult for bacteria to gain a foothold on the skin. The tight connections between the cells in this layer prevent bacteria and chemicals from slipping between the cells and gaining access to the deeper layers of skin.

Answer 152

The surface of the epidermis in hairy animals is covered in scale-like folds and contains knoblike elevations; these tactile elevations are also called epidermal papillae.

Answer 153

The dermis provides both structural and nutritional support to the epidermis. If you look at areas of skin with different thicknesses, you'll find that areas of thick skin have a thick dermis, while areas of thin skin have a thin dermis. The dermis isn't as highly organized as the epidermis and has only two layers, the thin superficial papillary layer, and the thick, deeper reticular layer. The dermal components consist of fibers, hair follicles, nerve endings, glands, smooth-muscle blood vessels, lymphatics, fibroblasts, adipocytes, and macrophages all jumbled together in a hodgepodge fashion

Answer 154

The fibers found in the dermis consists of collagen, elastin, and reticular fibers. Collagen is made of several protein strands braided together, much like a person's hair. The braiding increases the strength of the collagen fibers. Reticular fibers are a type of collagen that forms a loose net of thin, delicate fibers. Elastin fibers are almost the opposite of collagen fibers. Whereas collagen fibers help hold the skin together by being tough and rigid, elastin fibers stretch like rubber bands, giving the skin flexibility

Answer 155

Underneath all of the epidermal and dermal structures that make up the skin is the hypodermis, or subcutaneous layer. The thickness of the hypodermis depends on the area of the body, as well as the animal's species and weight. The hypodermis is composed primarily of fat, but it also contains blood and lymphatic vessels, nerves, and connective tissue. The hypodermis stores fat, helps regulate body temperature, and supports the layers above it—the dermis and epidermis—both structurally and nutritionally. Regulation of body temperature is achieved partly through control of the blood flow through blood vessels and partly through the amount of fat (which acts like insulation) present in the hypodermis.

Answer 156

The top of the nose in dogs, cats, sheep, and pigs is referred to as the planum nasale; in horses and cattle, it's referred to as the planum nasolabial. The top of the nose is thick, usually pigmented, and made up of only three of the five layers of skin—the stratum basale, stratum spinosum, and stratum corneum. The epidermal surface contains deep grooves. In sheep, pigs, and cattle, the planum nasale contains glands.

Answer 157

Found on horses. If you look at the medial aspect of the horse's front leg between the carpus (the equivalent of your wrist) and the elbow, or at the medial aspect of the hind leg below the hock (the equivalent of your ankle), you'll find a soft, horny structure called the chestnut.

Answer 158

If you examine the posterior aspect of the fetlock joint (the joint just proximal to the hoof) on horses, you'll find a soft, horny structure called the ergot. The ergot may be the remnant of the second and fourth toes, which gradually shrank with time.

Answer 159

t. The hair shaft is the free portion that rises above the skin surface. It's formed from three components layered over one another. The cuticle is a single layer of keratinized cells arranged like shingles on the outside of the shaft. The core of the shaft is the medulla, a layer that may not be present in all hairs. Between the cuticle and the medulla is the cortex, which makes up the bulk of most hairs and is composed of many keratinized cells packed together.

Answer 160

The hair root is the portion of the hair beneath the surface of the skin. If you pluck a hair from your skin, you may see a pale, slightly widened or knoblike area at its end. This area is the hair bulb, which attaches the hair to the dermis at a slight upward bump in the dermis called the papilla. Each hair root lies in and arises from a hair follicle, a shaft that's continuous with the skin's surface. Part of the hair follicle, the outer root sheath, grows down from the epidermis, while the other part, the inner root sheath, grows upward from the dermal papilla. Hairs originate from division of keratinocytes in the dermal papilla and hair bulb. Melanocytes are also present in the hair bulb and outer root sheath and are partly responsible for the color of the hair shaft.

Answer 161

Sweat glands

Answer 162

Preen gland in birds

Answer 163

Contour feathers—These are the most visible feathers and include the flight feathers of the wings and tail. Semiplume feathers—These are usually found under contour feathers and provide insulation and aid with buoyancy in water birds. Down feathers—These soft, fluffy feathers are located close to the skin and function primarily in insulation. Filoplume feathers—These barbless feathers are located on the nape and upper back and play a role in controlling feather movement. Bristles—These feathers may be found around the eyes, nostrils, mouth, or toes and play a role in the sense of touch. Powder down feathers—These constantly growing feathers create a waxy powder that spreads throughout the rest of the plumage to clean it and provide waterproofing.

Answer 164

The newly emerged feather is covered by an epidermal covering called the periderm.

Answer 165

Some reptiles have structures within the dermis called osteoderms that provide protection.

Answer 166

Shedding of the skin in reptiles

Answer 167

``` Support the body Protect the body Leverage - points of attachment Storage- minerals, especially calcium Blood Cell Formation ```

Answer 168

Metabolic functions are processes that deal with the buildup or breakdown of living cells for the purposes of providing energy and facilitating growth.

Answer 169

Cancellous bone, also called spongy bone, is a somewhat irregularly arranged group of bony material plates called trabeculae found in the bone marrow cavity. The cancellous bone provides a framework upon which the bone marrow material can perform its function. Cancellous bone also includes spine-like pieces of bony material called spicules. The spicules and trabeculae are arranged along lines of stress and force. Cancellous bone provides strength. In addition, the arrangement of the trabeculae and spicules is loose enough to be somewhat compressible, so cancellous bone acts as a shock-absorbing tissue.

Answer 170

Compact bone is a more highly structured series of bone layers found in the outer portions of the bone. Compact bone is composed of a series of tube-like structures arranged so that the tube shafts are parallel to the bone shaft. In the center of each tube is a space called the Haversian canal. This is the route through which blood vessels, lymphatic vessels, and nerves travel through compact bone. Several layers of bone are arranged in concentric circles around the Haversian canal.

Answer 171

Interspersed between the lamellae (bone layers) at random intervals are small spaces called lacunae, where osteocytes reside. The lacunae extend as fine channels called canaliculi that reach to nearby lacunae and the Haversian canal.

Answer 172

Other channels called Volkmann's canals extend from the Haversian canals at right angles and connect one Haversian canal to another. Volkmann's canals are like Haversian canals in that they carry nerves, blood vessels, and lymphatic vessels.

Answer 173

Collectively, the Haversian canal, lamellae, lacunae, and Volkmann's canal are called a Haversian system. Many Haversian systems are arranged side-by-side within the compact bone. A series of tubes arranged in this fashion provides strength without excessive weight. The arrangement of canals and canaliculi allows for movement of blood, nutrients, and nerve signals to the osteocytes in the most efficient manner possible. The structure of compact bone maximizes strength while minimizing weight and allowing for some flexibility.

Answer 174

At the outer surface of the bone, a membrane called the periosteum covers the bone (except for joint surfaces). The periosteum is made up of fibrous tissue and osteoblasts.

Answer 175

. The inner surface of bone is also lined with a membrane called the endosteum, which also contains osteoblasts.

Answer 176

Three types of cells are present in bone: osteoblasts, osteocytes, and osteoclasts.

Answer 177

are responsible for secreting the material that forms bone. As osteoblasts age, they become osteocytes, the primary cells of mature bone. However, under the proper conditions, osteocytes can revert to osteoblasts and begin forming bone again. This occurs when a bone is damaged (that is, broken).

Answer 178

Osteoclast cells are actually destructive, dissolving bone around them when needed. This comes in handy when there's bone growth that shouldn't be there or if the body needs calcium. Think of osteoclasts as the bone's demolition team and the osteoblasts as the construction workers who reconstruct the bone.

Answer 179

Mature bone. Located in spaces in the ossified matrix called lacunae

Answer 180

occurs in the facial bones of the skull and the bones of the jaw, when bone material is deposited into a membrane-like mesoderm tissue called the mesenchyme.

Answer 181

occurs in the bones of the legs, ribs, spine, and pelvis, as well as certain bones at the base of the skull. In endochondral ossification, connective tissue called cartilage develops and is gradually replaced by bone tissue. At each end of a long bone, the cartilage expands and ossifies. Two layers of cartilage remain on the bone's surface at each end of the long bone. Primary growth occurs in the diaphysis, whereas secondary growth forms at the epiphysis

Answer 182

As you grow and hormones are released in your body, your growth plates eventually stop growing and become calcified. This fuses the diaphysis and epiphyses and results in an increase in the bone's length.

Answer 183

vascular spaces in the bone marrow that contain bone marrow

Answer 184

The chief extracellular material within bone marrow is reticulin, a type of collagen that forms a very fine network of fibers in which the stem cells are interspersed.

Answer 185

forms a joint and contacts or articulates with another bone. Articular surfaces are covered with hyaline cartilage called articular cartilage. The cartilage, along with the smooth surface of the bone, helps to reduce wear and friction in joints.

Answer 186

rounded end of a bone that articulates with another bone. Condyles are found on the humerus, femur, and occipital bone of the skull.

Answer 187

refers to the rounded articular surface on the proximal end of a long bone. The head is attached to the main part of the bone by the neck. Heads are found on the humerus, femur, and ribs.

Answer 188

made up of small bones within soft tissue that don't connect directly to other bones. Although each of the visceral skeletal bones serves a specific function, they're relatively few in number. Some animals have no visceral bones. Examples of visceral bones include the os cordis, in cattle and sheep, and the os penis, in dogs. The os cordis is located within the heart of cattle and sheep and supports the heart valves. T

Answer 189

bands of tough, fibrous connective tissue that connect bones at joints,

Answer 190

bands of tough, fibrous connective tissue material that attach muscles to bones.

Answer 191

are the various projections and bumps found on bones. They have a variety of names depending on their location. A process on a vertebra is simply called a spinous process, while on the femur it's called a trochanter. The processes on the humerus are called tubercles, and the ischium process is termed the tuberosity.

Answer 192

s a natural opening or passageway through a bone. Often, blood vessels and nerves are present within the foramen of a bone.

Answer 193

a concave depression in a bone. Muscles are usually found in these areas.

Answer 194

``` Skull Hyoid bone Spine Ribs Sternum ```

Answer 195

Protects the brain Forms the nasal passages and eye sockets Creates jawbones for biting and chewing

Answer 196

The cranial cavity, where the brain is located The facial bones, which make up the nose, jaw, and eye sockets The ear bones

Answer 197

a single unpaired bone of the caudal skull that has a large opening called the foramen magnum. The foramen magnum is the opening into the cranial cavity where the spinal cord passes through to connect with the brain. The two occipital condyles (large, rounded articular surfaces) of the skull articulate with the atlas (first cervical vertebra).

Answer 198

On the lateral aspect of the cranial cavity is the temporal bone, which also forms a bony cavity called the tympanic bulla, where the structures of the middle ear are located.

Answer 199

In a living animal, the tympanic membrane (eardrum) extends across the external acoustic meatus, and the cartilage of the external ear canal attaches around it. The temporal bone also contains channels through which the nerves for hearing and balance pass on the way to the brain.

Answer 200

he parietal bone (caudally) and the frontal bone (rostrally). The frontal bone contains a projection that forms another part of the zygomatic arch. The frontal bone is also the bone to which the horns of cows, rams, and goats attach.

Answer 201

A single unpaired bone called the ethmoid bone forms the rostral wall of the cranial cavity and has a cribriform plate for passage of the olfactory (smell) nerves

Answer 202

Within the nasal cavity lies a complex arrangement of coiled and folded sheets of thin bone covered in a moist mucous membrane. The conchae warm and humidify the air as it's inhaled, help filter out debris from the air, and increase the surface area for the sense of smell.

Answer 203

forms the medial surface of the eye socket.

Answer 204

forms the upper jawbone and most of the hard palate, which is the bony roof of the mouth. The maxilla contains the sockets for the upper canine teeth and cheek teeth.

Answer 205

Where the two halves that come together in the Mandible meet

Answer 206

the shaft and the ramus of the mandible. The shaft of the mandible is the horizontal portion where the teeth are located. The ramus of the mandible is the vertical part that articulates with the skull. The condyle of the mandible is the part of the ramus that forms the hinge joint with the temporal bone. Medial and dorsal to the condyle is the coronoid process, a large plate of bone where some of the chewing muscles attach.

Answer 207

The bird eye socket is also protected by a ring of bony plates

Answer 208

are classified as either anapsid skulls or diapsid skulls, depending on the presence of temporal fossa

Answer 209

Closely associated with the bones of the skull is the hyoid bone, which is a structure made of bone and cartilage that forms a sling to support the larynx, pharynx, and tongue. The hyoid bone assists in the processes of swallowing.

Answer 210

In most vertebrae, the largest process is the spinous process, which rises vertically from the dorsal surface of the arch.

Answer 211

``` Cervical, or neck, vertebrae Thoracic, or chest, vertebrae Lumbar, or lower-back, vertebrae Sacral, or pelvic-area, vertebrae Coccygeal, or tail, vertebrae ```

Answer 212

All mammals (even giraffes!) have seven cervical vertebrae. The most cranial vertebra (C1) is called the atlas. This vertebra is named after Atlas, the Greek mythological figure who held up the heavens, because this bone supports the head. Unlike other vertebrae, the atlas is wide and flattened, lacks a spinous process, and includes large, transverse processes called wings.

Answer 213

The second cervical vertebra (C2) is the longest and is called the axis, because it's the major pivot point on which the head rotates. A cranial projection called the dens extends from the body of the axis to articulate with the atlas. In some dogs, the dens doesn't form well or becomes fractured, causing excessive motion at the joint between the atlas and axis, which can lead to pressure on the spinal cord and resultant pain.

Answer 214

The bodies of the thoracic vertebrae are short, with large spinous processes. The bodies of the thoracic vertebrae articulate with the head of the ribs, whereas the transverse processes of the thoracic vertebrae articulate with the tubercles of the ribs. Carnivores, cows, and sheep have 13 thoracic vertebrae, whereas horses have 18 and pigs have 14 or 15.

Answer 215

Lumbar vertebrae are dorsal to the abdomen. They have long transverse processes for attachment of the powerful lumbar muscles. The number of lumbar vertebrae varies among, and even within, species. Horses and cows usually have six lumbar vertebrae. Cats and dogs usually have seven. Goats, pigs, and sheep may have either six or seven.

Answer 216

The sacrum appears to be one bone but is in fact formed from the fusion of several vertebrae—three in dogs and cats; four in pigs and sheep; five in goats, cows, and horses. Within the sacrum, there are numerous foramina through which nerves and blood vessels travel out from the vertebral canal. The sacrum attaches firmly to the right and left ilium of the pelvis in what's called the sacroiliac joint.

Answer 217

The caudal, or coccygeal, vertebrae make up the animal's tail. They vary in number depending on the size of the tail and the species being looked at. For example, Manx cats have a very short or absent tail and thus have few—if any—caudal vertebrae.

Answer 218

is divided into three regions—presacral, sacral, and caudal—rather than the five regions seen in mammals.

Answer 219

Transverse process is a small bony projection off the right and left side of each vertebrae. The two transverse processes of each vertebrae function as the site of attachment for muscles and ligaments of the spine as well as the point of articulation of the ribs (in the thoracic spine

Answer 220

The more cranial ribs (such as the first nine pair in dogs) attach ventrally to bars of hyaline cartilage called costal cartilage, which attach to the sternum, or breastbone, in what's termed the costochondral junction (see Figure 7-23 on page 193 of your textbook). The costal cartilages of the more caudal ribs don't attach directly to the sternum but overlap each other to form the costal arch

Answer 221

The sternum helps protect the contents of the chest and aids in the breathing process. The cranial bone of the sternum is called the manubrium; the caudal bone is called the xiphoid. The caudal end of the sternum ends in a cartilaginous structure called the xiphoid process

Answer 222

support the front end of the body and aren't connected to the axial skeleton by bone, only by ligaments and tendons. Primates used for gasping, sea mammals used for swimming Bones- scapula, humerus, radius, ulna, carpal bones, metacarpal bones, and phalanges.

Answer 223

The scapula's lateral surface is divided into two grooves by the spine of the scapula. The cranial (and slightly dorsal) groove is called the supraspinous fossa (supra = "above"), whereas the caudal (and slightly ventral) groove is the infraspinous fossa (infra = "below").

Answer 224

Just distal to the humerus are two bones lying side by side called the radius and ulna. These bones form part of the thoracic limb known as the forearm In humans and some animals (dogs, cats, and pigs, for example), the radius and ulna are distinct and separate bones. However, in other animals, like ruminants, the bones are partially fused together. In the horse, they're completely fused.

Answer 225

The most proximal part of the ulna is the olecranon process, which is a very large tuberosity that serves as a point of attachment for the muscles that extend the elbow joint and thereby straighten the leg. The olecranon process is the bony prominence you can feel at your elbow. Just distal to the olecranon is the trochlear notch, the curved surface that articulates with the humerus.

Answer 226

small, somewhat cuboidal, bones that form much of the carpus, or wrist, in people. In animals, the carpus isn't called a wrist, and in fact, in horses, it's referred to as the "knee." The carpus is where the front leg bends to push the foot upward and backward. There are generally eight carpal bones arranged in two rows of four bones each. However, in some species, or even in individual animals within a species, some of the carpal bones may be fused together to form one bone, or some of these carpal bones may be missing.

Answer 227

The metacarpal bones are long bones lying side by side. In humans, these bones compose most of the palm of the hand. In animals, there's quite a bit of variation among species in the metacarpal bones The numbering of the toes or digits is based on the evolutionary development of the metacarpals. Take the horse, for example. Even though only one metacarpal is fully developed in each limb, the one that's most developed is called the third metacarpal because the other metacarpals (those associated with digits 1, 2, 4, and 5) were lost or greatly reduced during evolution.

Answer 228

Horses completely lack the first and fifth metacarpal bones. The second and fourth metacarpal bones, commonly called the splint bones, are vestigial and very small, compared with the large third metacarpal bone, cannon bone

Answer 229

he third metacarpal is the main metacarpal that bears the animal's weight. The second and fourth metacarpal bones in the horse lie medial and lateral (respectively) to the cannon bone and somewhat caudal to it.

Answer 230

The bones of each digit are called phalanges (singular, phalanx). Each digit except the first is composed of three phalanges—proximal, intermediate, and distal. The first digit is composed of two phalanges. The digit ends distally with a horny claw, nail, or hoof that's associated with the distal phalanx.

Answer 231

Horses have only one digit—the third—that bears all of the weight for the thoracic limb. The common name for the equine proximal phalanx is the long pastern bone. The second phalanx is called the short pastern bone, and the distal phalanx is called the coffin bone.

Answer 232

The pelvic limbs are directly connected to the axial skeleton by way of the sacroiliac joint, a meeting of the ilium of the pelvis and sacrum of the spinal column. This direct connection means there aren't a lot of tendons and ligaments holding the pelvic limb to the axial skeleton.

Answer 233

pelvic bones (ilium, ischium, and pubis), femur, patella, tibia, fibula, tarsal bone, metatarsal bones, and phalanges.

Answer 234

The pelvis is comprised of right and left halves, each of which is called an os coxae (os = "bone," coxa = "hip"). Each large os coxae forms during development from the fusion of three separate bones: the ilium, ischium, and pubis.

Answer 235

The wing of the ilium widens near the cranial border like the base of a triangle. This area is called the iliac crest. The medial angle of the iliac crest is called the tuber sacrale, and the lateral angle is the tuber coxae, also called the point of the hip. The dorsal border of the body of the ilium is called the greater ischiatic notch. This area is important because the sciatic nerve, one of the major nerves of the pelvic limb, travels over it.

Answer 236

Caudal and ventral to the ilium lies the ischium, which is also a mostly flat bone. The ischium's position is somewhat horizontal, whereas the ilium is positioned more vertically. The caudal and lateral angles of the ischium are known as the ischiatic tuberosities. The ischiatic tuberosities form a prominent angle of bone that you can palpate (examine by touch) on either side of a dog's tail. The ischium also serves as a point of attachment for several muscles of the hip, pelvic limb, and tail.

Answer 237

The pubis bone lies cranial to the ischium on both sides of the pelvis. Like the right and left ischium, the right and left pubic bones fuse with each other along the median plane on the ventral side of the pelvis.

Answer 238

At the junction of the ilium, ischium, and pubis is a deeply concave joint surface called the acetabulum. This surface is where the femur articulates with the pelvis in a ball-and-socket joint that forms the hip.

Answer 239

The head of the femur is very round in species that have a lot of mobility in the hip joint, and flatter in species with less ability to rotate the hip and move it laterally. Just distal to the head, the femur narrows in an area known as the neck of the femur. This connects to the femur's body (or shaft). At the proximal end of the shaft are several projections called trochanters that serve as sites of attachment for various muscles, including the gluteals. The largest of these projections is the greater trochanter, which is located on the lateral side. The lesser trochanter lies on the medial side. At the distal end of the femur are two curved surfaces that articulate with the tibia. These are called the medial condyle and the lateral condyle. Cranial and just proximal to the condyles lies a curved surface called the trochlea, where the patella (or kneecap) articulates.

Answer 240

The patella is the kneecap. It's the largest of the sesamoid bones in the body and is roughly oval-shaped, with a slight point on the distal end. The patella isn't directly connected to the femur. Instead, it's embedded in muscle tendons that straighten the knee joint, and it slides in the trochlea of the femur (the groove on the cranial and distal aspect of the femur) as these muscles contract and relax. The patella allows the tendons of the muscles of the leg's cranial surface to slide easily over the distal femur and improves the strength and leverage of the muscles that work across the stifle joint.

Answer 241

The tibia articulates with the femur to form the stifle joint. The tibia also attaches the muscles that bend the tarsal joint distally. The tibia is much larger than the fibula. If you cut the tibia in half perpendicular to its axis (in other words, a transverse section of the bone), it looks roughly triangular.

Answer 242

Connected to the tibia on its lateral side is a smaller bone, the fibula, which is long and thin. The fibula is a completely separate bone in dogs and cats, but in horses, cows, sheep, and goats, the fibula is greatly reduced and is partially fused with the tibia, so there's no distinct body. In horses, the lateral malleolus is part of the tibia.

Answer 243

connects the tibia and fibula at the proximal end to the metatarsal bones at the distal end. In humans, the tarsal bones make up the ankle, but in most animals, these bones are off the ground when they're in a standing position. The tarsus is commonly referred to as the hock joint in animals.

Answer 244

Fibrous, Cartilaginous, synovial

Answer 245

Fibrous joints are found in the skulls and in the splint bones of horses. These joints are immovable because they're united by fibrous tissue.

Answer 246

Cartilaginous joints are somewhat movable. They move in a rocking-type motion only and are found in the vertebrae, pelvis, and mandible.

Answer 247

Synovial joints are freely movable joints. Synovial joints are the most commonly thought of joints, as they're found in most movable areas of the body. They all have a joint capsule that surrounds a fluid-filled joint cavity, and they have articular cartilage that covers the articular surface found on the bone. The joint capsule has two layers, an outer fibrous layer and an inner membrane known as the synovial membrane. The synovial membrane produces synovial fluid, which is the fluid responsible for lubricating the joint surfaces. Depending on whether the joint has condyle bones it's attaching, there also may be a meniscus present. The meniscus is a fibrocartilagenous structure that helps to absorb shock. Synovial joints move in many different ways, including flexion, (hinge joint) extension (hinge joint), adduction, (gliding joint) abduction (gliding joint), rotation (pivot joints), and circumduction (ball and socket)

Answer 248

Smooth (involuntary), skeletal, cardiac

Answer 249

Moves the bones. Also called striated or voluntary. most have a thick, central portion and two or more attachment sites, which join them to whatever they move when they contract. Muscles are usually attached to bones via tendons. Tendons are fibrous bands of connective tissue.

Answer 250

A few muscles are attached to bones or other muscles via sheets of fibrous connective tissue . The linea alba that attaches the abdominal muscles together in the ventral midline is an example of an aponeurosis.

Answer 251

. Muscle attachment sites are referred to as either the origin or the insertion. The site that exhibits the greatest motion when the muscle contracts is the insertion, while the more stable site is the origin.

Answer 252

The group of muscles that directly produces a desired movement

Answer 253

The group of muscles that directly opposes the action of an agonist. The group of muscles that directly produces a desired movement is termed an agonis

Answer 254

contracts at the same time as an agonist and therefore helps to carry out the action desired by the agonist.

Answer 255

Muscle that help to stabilize joints, allowing other movements to happen

Answer 256

Masseter muscle—Used for chewing Splenius muscle—Raises the head and neck Trapezius muscle—Raises the head and neck Sternocephalicus muscle—Lowers the head and neck Brachiocephalicus muscle—Raises the head and neck and extends the front leg forward

Answer 257

External abdominal oblique Internal abdominal oblique Rectus abdominus Transverse abdominis

Answer 258

Latissimus dorsi—Flexes the shoulder and moves an animal forward Pectoral muscle (superficial and deep)—Moves the leg inward, or adducts the leg Deltoid muscle—Moves the leg outward, or abducts the leg, and flexes the shoulder joint Biceps brachii—Flexes the elbow, extends the shoulder Triceps brachii—Extends the elbow

Answer 259

Gluteal muscle—Extends and abducts the hip joint (moves the leg backward), thereby moving an animal forward Biceps femoris—Extends the hip joint, stifle joint, and tarsal joint Semimembranosus muscle—Extends the hip joint, flexes the stifle joint, and extends the tarsal joint Semitendinosus muscle—Extends the hip joint Quadriceps femoris—Extends the stifle joint Gastrocnemius muscle—Extends the tarsal joint and flexes the digits

Answer 260

Between the ribs are intercostal muscles that aid in breathing, as do the muscles that connect the ribs to the spine. The external intercostal muscles are used in inspiration, along with the diaphragm. The diaphragm also works with the internal intercostal muscles, but in expiration.

Answer 261

Cell membrane of a muscle cell

Answer 262

cytoplasm of a muscle cell

Answer 263

ER of muscle cell

Answer 264

Mitochondria of a muscle cell

Answer 265

The myofibrils contain thick filaments, composed of a protein molecule called myosin, and thin filaments, composed of a protein molecule called actin. These filaments are highly organized within the myofibril, and the visible difference in the regions of thick filaments, thin filaments, and areas of overlap between the two creates the striations visible in skeletal muscle under the microscope. The tubules of the sarcoplasmic reticulum encircle each myofibril like a sleeve with holes in it.

Answer 266

The thick myosin filaments are arranged in bundles in muscles like a stack of toothpicks with a little space between each

Answer 267

The thin actin filaments are arranged in bundles in muscles like a stack of toothpicks with a little space between each

Answer 268

The Z line contains specialized proteins and provides the site where the actin filaments attach. The area from one Z line to the next Z line is called a sarcomere and is the basic contracting unit of skeletal muscle. Each myofibril is made up of many sarcomeres lined up end-to-end.

Answer 269

The muscle cell membrane, the sarcolemma, folds inward in several locations, giving rise to a network of communication tubules called the T-tubules. The T-tubules intertwine with the myofibrils throughout the cell and enable the muscle cell to transmit the contraction signal to all of the myofibrils in the cell at the same time.

Answer 270

pieces of protein that stick out from the core of the filament and reach toward the actin molecules. These cross bridges are important because they link the thick myosin filaments to active sites on the thin actin filaments when the muscle contracts.

Answer 271

A synapse resulting from contact betweem a muscle fiber and motor neuron

Answer 272

nerve fiber and the muscle fibers with which it interacts

Answer 273

The neuromuscular junction is actually a small space that exists between a nerve fiber and the sarcolemma of the muscle fibers

Answer 274

The neurotransmitter chemical, acetylcholine, diffuses across this space from the nerve fiber and attaches to receptors on the sarcolemma. This initiates a series of events that lead to contraction of the muscle. The nervous system controls the timing of this impulse generation as well as the number of motor units that are stimulated.

Answer 275

Binding of acetylcholine to these receptors generates an electrical impulse along the sarcolemma. The excitatory signal is carried inside the muscle cell by the T-tubule system, which contacts all of the myofibrils in the cell. Electrical changes in the T-tubules reach the sarcoplasmic reticulum and cause it to release its stored calcium ions (Ca2+). This Ca2+ diffuses into the myofibrils. The presence of an increased concentration of calcium causes the cross bridges on the myosin filaments to slide back and forth. That motion causes the actin filaments to be pulled toward the center of the myosin filaments and results in the shortening of the sarcomere. The muscle contracts when all of the sarcomeres in a muscle fiber have shortened. These movements require substantial amounts of ATP. ATP must bind to the myosin head before the contraction begins. The myosin head splits the ATP into ADP and phosphate.

Answer 276

Removes acetylcholine from muscles

Answer 277

Within muscle fibers. resulting in the formation of creatinine. The reaction requires the enzyme creatine kinase and results in the "donation" of a phosphate group to an ADP molecule, forming ATP

Answer 278

Cardiac muscles contain only one nucleus (sometimes two) per muscle cell. The nucleus is centrally located. Cardiac muscle has a greater concentration of sarcosomes (mitochondria) than skeletal muscle, because it has a greater need for energy on a continuous basis than does skeletal muscle.

Answer 279

connect adjacent cardiac muscle cells and have a low resistance to electrical current. Intercalated disks help transmit electrical impulses for contractions from cell to cell.

Answer 280

located in the wall of the right atrium, where each heartbeat begins

Answer 281

serve as the conduction system of the heart.

Answer 282

vital to muscle junction. Abnormally low or high levels of calcium can interfere with normal muscle contraction, which is especially serious in the heart.

Answer 283

These three ions control the electrical charge present on the muscle cell membrane, both when the muscle is at rest and during the excitation process. The movement of these ions across the sarcolemma can affect the speed, duration, and strength of the muscle contraction. Again, a deficiency or excess of these ions can halt the normal excitation-contraction process.

Answer 284

it provides the energy for contraction. Anything interfering with the synthesis of ATP in the sarcosomes leads to paralysis, because no energy will be available for contraction.

Answer 285

the contraction mechanism is composed of proteins. Although all tissue in the body has some degree of protein, muscle tissue has the highest protein concentration of all body tissues

Answer 286

The central nervous system (CNS), which consists of the brain and spinal cord and their associated structures. Contains upper motor neurons

Answer 287

The peripheral nervous system (PNS), which comprises the nerves traveling from the brain or spinal cord to the target organs and back. Contains lower motor neurons

Answer 288

carries out conscious activities, such as walking, eating, and so on, as well as activities that are somewhat unconscious, like posture

Answer 289

performs functions that don't require conscious thought, such as breathing, blood pressure, and heart rate

Answer 290

considered the sensory nerve fibers, as they conduct sensations from the sensory receptors of the body to the CNS. These locations can be either inside or outside of the body.

Answer 291

considered the motor nerve fibers, as they conduct impulses from the CNS to the organs and muscles of the body. Motor responses involve movements of the body, such as secretion from a gland or movement of a muscle

Answer 292

Nerves which are both sensory and motor

Answer 293

Support and protect neurons. Don't transmit signals

Answer 294

receive stimuli and conduct it to the cell body

Answer 295

conduct nerve impulses away from the vell body

Answer 296

Carries signals between neurons

Answer 297

Central part of the cell body which includes the nucleus

Answer 298

The cytoplasm within a cell

Answer 299

At the end of the axon are one or more small branches that end in a slightly disk-shaped. lies adjacent to the cell membrane of the next cell in the pathway

Answer 300

Packages of chemicals within the synaptic knob are synaptic vesicles. responsible for passing the signal from one neuron to the next.

Answer 301

The membrane covering the end of the synaptic knob

Answer 302

The surface of the adjacent dendrite or muscle cell membrane. The two membranes are separated by a gap called the synaptic cleft. The postsynaptic membrane serves as the receptor for the nerve impulse traveling across the synaptic cleft.

Answer 303

Surrounding the axons of many peripheral neurons they provide structural and metabolic support to the neurons. The Schwann cells make up a protective covering over the axon called the myelin sheath, which consists of layers of Schwann cell cytoplasm and a cell membrane These neurons are said to be myelinated. Myelinated nerve fibers are wrapped up in many layers of the cytoplasm of the Schwann cell, which spirals around the axon to envelop

Answer 304

The myelin sheath thins between Schwann cells, exposing some of the axon to the extracellular environment

Answer 305

Specialized molecules in the neuron's cell membrane pump sodium ions from the inside to the outside and pump potassium ions from the outside to the inside.

Answer 306

Electrical signals travel along myelinated axons. In this process, the electrical impulse "jumps" from one node of Ranvier to the next without depolarization and repolarization taking place along the entire length of the axon cell membrane.

Answer 307

secreted in various areas of the central nervous system. In the peripheral nervous system, it's secreted by somatic motor neurons controlling skeletal muscle fibers and by neurons of the parasympathetic nervous system. The effect of acetylcholine is usually excitatory.

Answer 308

secreted in several areas of the brain. In the peripheral nervous system, it's secreted only by neurons of the sympathetic nervous system. Norepinephrine may be excitatory or inhibitory.

Answer 309

composed of aggregates of brain neuron cell bodies, while white matter is composed of the axons and dendrites of these neurons. These two types of nervous tissue are visibly separate. In the brain, the outer layer is gray matter, while the inner layer is white matter. Oddly enough, in the spinal cord, the opposite is true—the white matter is on the outside, while the gray matter constitutes the core of the spinal cord.

Answer 310

composed of aggregates of brain neuron cell bodies, while white matter is composed of the axons and dendrites of these neurons. These two types of nervous tissue are visibly separate. In the brain, the outer layer is gray matter, while the inner layer is white matter. Oddly enough, in the spinal cord, the opposite is true—the white matter is on the outside, while the gray matter constitutes the core of the spinal cord.

Answer 311

The central nervous system has very little connective tissue except in the external coverings known as the meninges. Covering the surface of the brain or spinal cord tissue is a layer called the pia mater. The middle layer is the arachnoid, and the outermost layer of meninges is the dura mater The arachnoid and the dura mater aren't directly connected. A very thin space called the subdural space lies between them

Answer 312

Divides the cerebellum in half along the central plane

Answer 313

Indentation in the cerebrum

Answer 314

Raised area between the sulcus in the cerebrum

Answer 315

Sensory nerve dendrites travel through the dorsal root and end in the dorsal root ganglion, a cluster of sensory neuron cell bodies that lies next to the spinal cord

Answer 316

The motor nerve axon branches away from the sensory nerve dendrites at the muscle level and terminates at the neuromuscular junction.

Answer 317

The axillary nerve supplies the muscles that flex the shoulder and the skin over the cranial surface of the elbow. The radial nerve is the largest brachial plexus nerve. It supplies the lateral surface of the humerus and the cranial-lateral surface of the foreleg and foot. The median nerve supplies the medial surface of the foreleg and the palmar surface of the foot. The ulnar nerve supplies the caudal surface of the foreleg and palmar surface of the foot (overlapping with the median nerve).

Answer 318

The brachial plexus is found medial to the scapula on each side of the body. It's formed from the fusion of the ventral branches of several spinal nerves and is involved with controlling the thoracic limbs.

Answer 319

Nerve supply to the pelvic limbs. The three major nerves coming from the lumbosacral plexus are the femoral nerve, the obturator nerve, and the ischiatic (also called the sciatic) nerve. The femoral nerve supplies the cranial muscles of the femur and sensory nerves to the medial surface of the thigh and foreleg. The obturator nerve supplies primarily the muscles of the medial thigh. The biggest lumbosacral plexus nerve is the ischiatic, which passes over the hip joint and travels down the caudal-lateral surface of the thigh, supplying the caudal thigh muscles.

Answer 320

a synonym for the parasympathetic division.

Answer 321

third, seventh, ninth, and tenth cranial nerves. All of these travel to areas of the head—

Answer 322

Three different adrenergic receptor subtypes are present in the sympathetic nervous system. They're designated alpha, beta-1, and beta-2. Norepinephrine primarily stimulates alpha receptors, while epinephrine stimulates all receptor types equally well.

Answer 323

found in the target organs of the parasympathetic nervous system and in the target organs of the cholinergic postganglionic neurons of the sympathetic nervous system.

Answer 324

found in the synapse between the preganglionic and postganglionic neurons of both the parasympathetic and sympathetic nervous systems, as well as at the neuromuscular junctions in skeletal muscles.

Answer 325

When the sensory neuron stimulates the motor neuron, the motor neuron stimulates the muscle to carry out its specific activity, without any input or interaction with the brain. This is nerve-to-nerve interaction

Answer 326

The dendrites of the sensory neurons travel via the dorsal root of the spinal nerve, stopping at the dorsal root ganglion, where the cell body is located. The axon then enters the spinal cord via the remaining portion of the dorsal root. Once in the spinal cord, the neuron synapses with other neurons that either travel up the spinal cord to the brain, or travel within the spinal cord to synapse with yet other neurons.

Answer 327

the stretch reflex, the withdrawal reflex, the crossed extensor reflex, the palpebral reflex, and the pupillary light reflex (PLR).

Answer 328

Hunger, thirst, and the feeling of fullness in hollow organs, such as the urinary bladder and stomach,

Answer 329

located within the hypothalamus of the brain and monitor the body's internal temperature.`

Answer 330

pain receptor

Answer 331

The first is transduction, where a painful stimulus is converted to a nerve impulse. The second is transmission, where the stimulus is relayed to the spinal cord. The third process is called modulation and occurs in the spinal cord; at this point, the pain becomes either more or less severe. The fourth process is perception of the pain impulse by the brain.

Answer 332

On the dorsal surface of the tongue, taste buds line the sides of small, raised bumps

Answer 333

The pinna is shaped like a cone

Answer 334

The eardrum vibrates when sound hits it via this process

Answer 335

. The malleus is the outermost of the three bones—and the only one that contacts the eardrum. It's also called the hammer, because it hits upon the next bone, the incus, commonly called the anvil. The third bone in line is the stapes, which is also called the stirrup because its shape resembles a stirrup used in horseback riding.

Answer 336

also called the vestibular window). The oval window is an opening in the temporal bone of the skull at the medial side of the middle ear that leads into the inner ear.

Answer 337

The malleus also has a tiny muscle attached to it. This muscle can adjust the tension of the eardrum and therefore soften the transmission of loud vibrations (such as those found at music concerts) to the inner ear.

Answer 338

The stapes also attaches to a muscle, the stapedius, which can restrict the movement of the stapes in response to loud sounds.

Answer 339

also called the cochlear window, lies between the oval window and the auditory tube. This window serves as another opening in the temporal bone leading into the inner ear

Answer 340

The ventral part of the middle ear below the tympanic membrane and auditory canal is called the tympanic bulla (plural: bullae), a round, normally hollow cavity surrounded by a thin layer of bone. The entire surface of the middle ear is lined with ciliated columnar epithelium.

Answer 341

The inner ear consists of a membranous system of saclike structures and a mazelike system of ducts in the bone filled with a fluid called perilymph.

Answer 342

The ducts and saclike structures are organized into three basic structures: the cochlea, which is responsible for detection of sound; the semicircular canals; and the vestibule. The latter two are involved in maintaining balance.

Answer 343

The cochlea is spiral-shaped, gradually decreasing in size until finally coming to a dead end at the apex, or cupula.

Answer 344

a hollow core containing the cochlear nerve

Answer 345

fluid in the cochlear duct

Answer 346

The organ of Corti consists of supporting epithelial cells, a tectorial membrane, and hair cells that are the receptor cells of hearing.

Answer 347

a hollow, oval organ that communicates with the cochlea rostrally and with the semicircular canals caudally. On the lateral surface of the vestibule is the vestibular window, which is sealed by the base of the stapes. The bony portion of the vestibule is filled with perilymph. Within the perilymph lie membranous structures known as the utricle and saccule. Both are involved with the sense of balance.

Answer 348

roughly spherical, connects with the cochlear duct, and is filled with endolymph. The utricle and the saccule each contain a sensory organ called a macula (plural: maculae). Each macula is a focal, thickened area of epithelium containing supporting cells and ciliated hair cells much like those of the organ of Corti in the cochlea. The specialized cilia of these cells are embedded in a gelatinous covering called the otolithic membrane, on the surface of which are small crystals called otoliths. The structures of the maculae are designed to detect the head's motion and position. Movement of the head causes the otoliths to pull against the hairs, which sends signals to the brain.

Answer 349

lie on the opposite side of the vestibule from the cochlea. Each semicircular canal is a tube with two openings into the vestibule and is positioned at nearly a right angle to the other two canals. One of the canals lies horizontally, while the other two lie vertically. The membranous portion of each semicircular canal is the semicircular duct, which is filled with endolymph and is surrounded by perilymph. Each semicircular canal is continuous with the utricle at each end, but one end of each canal is dilated into a structure called the ampulla (plural: ampullae). On one side of the wall of the duct in the ampulla is a crest of thickened connective tissue called the crista ampullaris. The surface of this crest is lined with a layer of hair cells, similar to those in the utricle and saccule, covered with a gelatinous mass called the cupula. The cupula is similar to the otolithic membrane in a macula. These structures aid in perception of balance.

Answer 350

Sound is funneled by the pinna into the external ear canal, where the tympanic membrane vibrates in response to the vibrations in the air. These vibrations are transmitted in turn to the three ossicles of the middle ear—first the malleus, then the incus, and finally the stapes. The base of the stapes fills the oval window in the vestibule. As the stapes vibrates, the vibrations are transmitted to the perilymph, then to the endolymph of the cochlear duct, and finally to the organ of Corti. The tectorial membrane vibrates over the cilia of the hair cells. This vibration initiates a change in the cell membrane that creates an electrical impulse in the cochlear nerves. This impulse is then transmitted to the central nervous system. Varying stimulation in different areas of the cochlea is interpreted by the brain as sounds of different pitch. Low frequencies stimulate the apex of the cochlea more, while high frequencies stimulate the base of the cochlea more. Vibrations in the temporal bone can also create vibrations in the perilymph and organ of Corti, leading to auditory signals.

Answer 351

Outermost layer of eye, a transparent layer of tissue that allows light to enter the eye

Answer 352

Outermost layer of eye, which is seen as the opaque, white part of the eye surrounding the cornea and pupil. External muscles controlling the eye movements attach to the sclera, which constitutes the bulk of this outer layer.

Answer 353

junction between the sclera and the cornea is called the limbus and is slightly depressed.

Answer 354

Outermost layer of eye (cornea and sclera) and contains no blood vessels but does contain a large number of nerve fibers

Answer 355

Middle layer of the eye, contains large numbers of blood vessels and therefore is also called the vascular layer. The uvea contains three parts: the ciliary body, the choroid, and the iris.

Answer 356

encircles the outer edge of the lens and is attached to the lens via the suspensory ligament. This structure adjusts the shape of the lens to allow for near and far vision.

Answer 357

Middle layer, contains a highly reflective area called the tapetum that aids in night vision

Answer 358

Middle layer, Is made up of a muscular diaphragm that controls the amount of light that enters the eyeball. The iris also has pigments that give eyes their color. The center of the iris is called the pupil, which is also made up of muscle fibers. These muscle fibers are arranged both radially and circularly to help the pupil constrict or dilate as the need arises.

Answer 359

also called the nervous layer, which contains the neurons responsible for detection of light stimuli. The retina lines the interior of the eye everywhere except near the ciliary body. There's no retina lining the back of the lens, the ciliary body, the suspensory ligament, or the cornea. Axons of the neurons in the retina gather together at a single spot on the retina, the optic disk, which forms the optic nerve that exits the eye at a point on the caudal and slightly ventral surface of the eye.

Answer 360

the smaller anterior chamber, Aqueous fluid in the anterior portion of the eye is a watery fluid somewhat similar in composition to cerebrospinal fluid. It's secreted by the ciliary processes of the ciliary body and supplies nutrients to the corneal cells.

Answer 361

, the larger posterior chamber of the eye, The iris lies just in front of the lens and divides the aqueous chamber into anterior and posterior chambers. The vitreous chamber is filled with the vitreous body, a mass of gelatinous material called vitreous humor. The vitreous body helps support the retina, lens, and ciliary body from within.

Answer 362

Aqueous fluid is reabsorbed by the canal of Schlemm, a duct located at the angle of the cornea and the iris.

Answer 363

A balance between production and absorption of aqueous fluid exists such that a constant pressure is maintained within the aqueous chamber. This pressure is called intraocular pressure and helps support the cornea from within. Glaucoma is a disease of the eye in which the drainage of aqueous humor is obstructed or decreased, causing increased intraocular pressure and pain. If glaucoma becomes severe, the retina may be damaged, and blindness may ensue

Answer 364

he orbit is supported in a socket formed by the bones of the skull and is surrounded by fatty connective tissue. Eyelids protect the eye. The skin of the outer surface of the eyelid turns inward toward the eye and becomes the conjunctiva, a layer of epithelium that secretes mucus and lines both the inner surface of the eyelids and the cranial surface of the sclera

Answer 365

secretes tears that moisten the eye and help wash away debris. Tears drain into the nasal cavity via a tiny tube called the nasolacrimal duct, found near the medial corner of the eye, where the upper and lower eyelids meet.

Answer 366

The lens is composed of multiple layers of long, thin epithelial cells, called lens fibers, arranged to be transparent. Lens fibers lack nuclei but aren't dead. Their cell membranes are fused, so there's little or no extracellular material.

Answer 367

The retina is a highly complex tissue designed for receiving light and converting it into neurological signals. The retina is composed of multiple layers. These layers consist either of neuron cell bodies or of the dendrites and axons of these neurons. The arrangement of the retinal cells may seem a little backward to you at first.

Answer 368

The outermost layer, the pigment layer, consists of pigmented cells lying next to the choroid. The next layer of cells, the photoreceptor layer, is composed of receptor neurons called rods or cones, which sense light stimuli and are named by the rod and cone shape of the receptor dendrites. Both rods and cones have dendrites with multiple, overlapping, and stacked layers of cell membranes at the tip. These membranes contain a light-absorbing pigment called rhodopsin in the rod cells. In the cone cells, there's a pigment called iodopsin that's sensitive to various colors.

Answer 369

The cell bodies and their axons project in toward the eye's center, where the axons synapse with the next layer of cells, the nerve fiber layer—in the retina, the integrating neurons. The integrating neurons carry the signal from the rod or cone cells to the innermost layer of cells, the ganglion cell layer.

Answer 370

axons that travel parallel to the inner surface of the retina until they reach the optic disk, where they form the fibers of the optic nerve that travel from the eye to the brain.

Answer 371

unique in being both an endocrine gland and an exocrine gland. The endocrine function is the secretion of substances such as insulin, which metabolizes sugar. The exocrine function involves the secretion of digestive enzymes into the duodenum.

Answer 372

All endocrine glands secrete hormones in the form of proteins that travel via the blood to the target organ for that particular hormone. The hormone causes changes in the activity, and in some cases the structure, of the target organ. Hormones collectively coordinate the physiology of nearly all activities in the body. In this way, the endocrine system is related to the nervous system. Hormones can be divided into three main groups: peptide hormones, steroid hormones, and monoamine hormones. The peptide hormones are hydrophilic, which means they're able to travel through blood very easily. Most hormones fall in the peptide hormone class. The steroid hormones are made from cholesterol and are therefore hydrophobic. These hormones have a difficult time traveling through blood and must have a hydrophilic transport. The monoamine hormones are made from amino acids and can be either hydrophilic or hydrophobic, depending on the specific hormone.

Answer 373

Many endocrine glands are self-regulating via a process called feedback. Hormone secretion raises the blood level of that hormone or affects the level of specific substances in the blood. The endocrine cells detect the altered levels of the hormone or substance that they monitor and decrease the secretion of their hormone (negative feedback) or increase it (positive feedback). Breakdown in this self-regulation can lead to disorders of endocrine secretion.

Answer 374

works to control appetite, body temperature, and wake-sleep cycles; it also links higher and lower brain centers with the endocrine system. The linking of the brain centers with the endocrine system happens due to the control the hypothalamus has over the pituitary gland.

Answer 375

(also called the hypophysis) has a multitude of functions, many of which involve control of other endocrine glands. The pituitary gland consists of two parts: the anterior pituitary and the posterior pituitary. Each contains different types of cells that secrete different substances. The posterior pituitary, also called the neurohypophysis, is an outgrowth of nervous tissue from the hypothalamus in the brain. The epithelial tissue that comprises the anterior pituitary wraps around the posterior pituitary gland and communicates with the hypothalamus via the portal system, a system of blood vessels.

Answer 376

produces hormones that help release or inhibit anterior pituitary hormones. The hypothalamus also produces two hormones, antidiuretic hormone (ADH) and oxytocin, that are then stored in the posterior pituitary gland. The hormones' release is stimulated by nerve impulses traveling from the hypothalamus.

Answer 377

antidiuretic hormone (ADH) , produced by the hypothalamus, acts to improve water uptake in the renal collecting duct by increasing its permeability to water. This ensures that the body doesn't excrete too much water and become dehydrated. ADH also causes some smooth-muscle contraction that can lead to blood vessel constriction and a resulting increase in blood pressure.

Answer 378

stimulates contractions of the uterus during labor and mating. During mating, the oxytocin helps spermatozoa get to the oviducts. During labor, the contractions of the uterus help to expel the fetus and placenta. Oxytocin also stimulates milk production in what's termed milk letdown. The offspring nursing or the mother being milked stimulates the release of the oxytocin into the bloodstream. This, in turn, causes the milk to go into the lower parts of the mammary gland, giving the offspring the much-desired milk. Oxytocin may also play some role in mother-offspring bonding.

Answer 379

synthesizes the hormones it secretes, including a group of hormones that stimulate growth and secretion of other endocrine cells. It also secretes hormones that act directly on tissues to produce their effects.

Answer 380

``` Thyroid-stimulating hormone (TSH), which stimulates thyroid gland growth and secretion of hormones Adrenocorticotrophic hormone (ACTH), which stimulates adrenal gland cortex growth and secretion of various hormones Follicle-stimulating hormone (FSH), which is involved in the growth and development of follicles found in the female ovaries and encourages secretion of estrogens from the follicle. In the male animal, FSH stimulates spermatogenesis in the testes. Luteinizing hormone (LH), which finishes the development of the follicle, leading to ovulation and development of the corpus luteum. The corpus luteum then produces progesterone. In the male animal, LH stimulates interstitial cells to develop and produce testosterone. ```

Answer 381

Growth hormone (GH), which is very important in the mature development of a person or animal and regulating metabolism of lipids, carbohydrates, and proteins in the cells of the body Prolactin, which stimulates development and secretion of the mammary glands Melanocyte-stimulating hormone (MSH), which stimulates production of melanin in the skin by special cells called melanocytes

Answer 382

Two small glands located in the neck, one on each side of and just ventral to the trachea, are known as the thyroid glands. Thyroid glands secrete thyroid hormone and calcitonin. Calcitonin helps regulate blood calcium levels. Thyroid hormone controls cell metabolism and stimulates nervous tissue growth in young animals. It also stimulates production of proteins and helps maintain blood glucose levels. The term "thyroid hormone" actually refers to two distinct molecules: Thyroxine, also known as T4, contains four iodine molecules. Triiodothyronine, also known as T3, incorporates three iodine molecules. TSH produced by the pituitary gland stimulates secretion of thyroid hormone from the thyroid glands. Calcitonin regulates the level of blood calcium (prevents it from getting too high, which is known as hypercalcemia) by inhibiting the release of calcium from bone. It also stimulates calcium deposition in bone by increasing the activity of osteoblasts. Calcitonin secretion is regulated by the level of blood calcium and is independent of thyroid hormone secretion.

Answer 383

Immediately adjacent and just caudal to the thyroid glands is a pair of very small glands called the parathyroid glands. The parathyroid glands secrete a hormone called parathyroid hormone (PTH), which is also called parathormone. Parathormone causes the blood calcium level to rise. Phosphorus levels decline in the face of parathormone because the renal reabsorption of phosphorus is inhibited and excretion is increased. Regulation of phosphorus in conjunction with calcium is important. If calcium and phosphorus levels are above a certain level, crystals of calcium and phosphorus are deposited in tissues, causing tissue damage. Secretion of parathyroid hormone is regulated by the level of blood calcium detected by the parathyroid cells. As blood calcium decreases, the secretion of parathyroid hormone increases, and vice versa.

Answer 384

Cranial to each kidney in the abdominal cavity is an adrenal gland. The adrenal gland is a small, oval-shaped, somewhat flattened gland. The adrenal glands have two sections—an outer layer of tissue called the adrenal cortex and an inner core of tissue called the adrenal medulla. The adrenal medulla secretes epinephrine and norepinephrine. The adrenal cortex secretes mineralocorticoids, including aldosterone; a group of hormones known as glucocorticoids; and some sex hormones, particularly androgen and estrogen.

Answer 385

stimulates the uptake of sodium and water as well as the excretion of potassium in the renal tubules. Remember that sodium and potassium have important roles in maintaining the body's homeostasis. The body usually has a fairly high amount of sodium present in the bloodstream, while potassium remains very low. With the reabsorption of sodium, water is also reabsorbed.

Answer 386

a type of steroid that cause many metabolic effects throughout the body—most importantly, a hyperglycemic effect. The levels of glucose in the body rise with the release of these hormones by way of gluconeogenesis, a process that occurs in the liver. Glucocorticoid hormones also help maintain blood pressure and help the body in times of stress.

Answer 387

derived from nervous tissue. It's controlled by the sympathetic nervous system. Epinephrine and norepinephrine work to stimulate the body in response to a threat, so the animal can fight and overcome the threat or flee and escape it (the fight-or-flight response). The heart and lungs are stimulated to work faster, so the muscles have plenty of oxygen supply. Digestion is halted temporarily so that blood and oxygen can be diverted to the muscles—after all, digestion won't be needed anymore if the animal is eaten by a lion.

Answer 388

The pancreas is also an endocrine organ, secreting several hormones into the blood. Scattered among the exocrine pancreatic cells, and located near blood vessels, are clumps of cells called the islets of Langerhans. The primary hormones secreted by the pancreatic islet cells are insulin, glucagon, and somatostatin.

Answer 389

enables cells—especially liver, muscle, and fat cells—to take glucose, amino acids, and fatty acids from the blood and use them for generating energy for cellular functions. This removal of glucose from the bloodstream causes the level of glucose in the blood to be decreased. Glucagon opposes many of the effects of insulin by decreasing uptake of glucose by cells, thereby increasing it in the bloodstream. Glucagon also stimulates the synthesis of glucose from glycogen and gluconeogenesis (in which fat and protein convert to glucose) in the liver.

Answer 390

This hormone has many effects, but it primarily inhibits secretion of insulin, glucagon, and growth hormone and decreases the activity of the gastrointestinal tract.

Answer 391

The most common disorder of the endocrine pancreatic function. Diabetes mellitus is a deficiency of insulin secretion or, in some cases, a lack of responsiveness to the presence of insulin. The cause of diabetes mellitus, in most cases, is damage to the beta cells in the islets of Langerhans. Lack of insulin results in cellular inability to take in glucose and leads to hyperglycemia (excessive levels of glucose in the blood). Weight gain or weight loss, increased appetite, and increased thirst and urination are all signs of diabetes mellitus.

Answer 392

One of the many functions of the reproductive organs, the testes and ovaries, is production and secretion of sex hormones. Within the testes, hormones from the anterior pituitary stimulate the continuous production of androgens by clumps of specialized cells. Androgens are a group of hormones involved in the development of male secondary sex characteristics. Cells in the ovaries produce the female sex hormones on a cyclical timetable when stimulated by the hormones FSH and LH from the anterior pituitary. The ovaries actually produce two groups of hormones, the estrogens and the progestins. The estrogens function to prepare the female for breeding. The primary progestin, progesterone, is involved in preparing the uterus for pregnancy. Interstitial cells in the testes produce the male sex hormone testosterone. Testosterone is stimulated by the LH hormone from the anterior pituitary and is the primary hormone responsible for the development of the male secondary sex characteristics, development of the male accessory sex glands, spermatozoa production, and penile growth. The secondary sex characteristics include muscle development and libido.

Answer 393

These compounds are organized into nine groups, designated by the letters A through I, and act within the area where they're produced.

Answer 394

Cells in the kidneys secrete the hormone erythropoietin. This hormone is released in response to tissue hypoxia and results in stimulation of the bone marrow to produce red blood cells. Once red blood cell production has increased enough, the increase of the blood's oxygen level tells the kidneys to slow the production of erythropoietin. This is an example of a feedback mechanism.

Answer 395

Cells in the stomach produce the hormone gastrin, which acts to stimulate the production of digestive enzymes in the stomach and the secretion of hydrochloric acid. It also helps with stomach wall muscle contractions.

Answer 396

The small intestine contains cells that secrete the hormones secretin and cholecystokinin (CCK). These hormones stimulate gallbladder contraction, the release of other digestive enzymes from the pancreas, and the slowing of gut motility to allow for better digestion. The hormones also inhibit stomach gland secretions.

Answer 397

The placenta encloses the fetus during pregnancy and forms the interface between the fetal and maternal circulations. It secretes the hormone chorionic gonadotropin, which functions in the maintenance of pregnancy. Small amounts of sex hormones are also produced in placental tissue to help maintain and support pregnancy.

Answer 398

The thymus gland is active in infancy and secretes the hormones thymosin and thymopoietin. These hormones act to stimulate the development of T-lymphocytes and strengthen the immune system.

Answer 399

seated within a fluid-filled space in the third ventricle of the brain. The cells in the pineal body secrete the hormone melatonin. The function of melatonin isn't well understood, but it appears to play a role in regulating sleep and wakefulness, as well as seasonal estrous cycles in some species. Secretion of melatonin may be influenced in part by the amount and duration of sunlight in the environment

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