Biology 2 Flashcards
(270 cards)
1
Q
What is the purpose of the integumentary?
A
Provides a physical barrier to prevent the entrance of pathogens into the body
2
Q
What consists of the integumentary in humans and animals?
A
In humans: hair, skin and nails
In animals: fur, hooves, scales, feathers, shell
3
Q
What is the purpose of the skin?
A
Nonspecific defense mechanism that protects against pathogenic invasion
4
Q
What is the pH of the skin?
A
4-6 in humans, decreases bacterial growth
5
Q
What are some functions of sweat?
A
Evaporative cooling, has enzymes that help destroy bacterial cell walls
6
Q
What are the layers of the skin and what connects them?
A
Two layers: Dermis and epidermis which are connected by the basement membrane
7
Q
What does the dermis do?
A
Has the blood supply to the skin and most of the specialized cells
8
Q
What does the epidermis do?
A
Has keratinocytes which differentiate into corneocytes which are protective, waterproof cells that don’t undergo any further replication and are routinely sloughed off and replaced
9
Q
What is the purpose of hair?
A
Can direct sweat and waste away from the skin, help with evaporative cooling when body is hot or trap heat when body is cold, sensory organ and can detect nearby motion
10
Q
What is the purpose of nails?
A
Protect tips of fingers and toes from injury and can be used as tools
11
Q
What are the 2 major types of immunity?
A
Innate and adaptive
12
Q
What is innate immunity?
A
The bodys intial, generalized defenses against pathogens
13
Q
What are some non specific defense mechanisms?
A
inflammatory response, physiologic response (temperature and pH change), phagocytes cells (neutrophils and macrophages)
14
Q
What occurs during inflammation?
A
During inflammation, injured cells release chemicals like histamine that dilate and increase the permeability of blood vessels, which increases white blood cell and immune cell to affected area
15
Q
What is the purpose of a fever?
A
Fever increases the ability to fight infections by killing temperature dependent pathogens and speed up healing process
16
Q
What do granulocytes do?
A
They are attracted to the site of injury where they phagocytize antigens and antigenic material
17
Q
What are the types of granulocytes?
A
- Neutrophils are the most common type, first responders to sites of inflammation, attracted to cytokines, attract additional WBC to site, main component of pus, adapted to attack bacteria
- Eosinophils are less common, responsible for immune responses (e.g allergy or asthma)
- Basophils and mast cells are involved in allergic responses and parasite infections, often responsible for release of histamine
18
Q
What are monocytes?
A
Immune cells that can differentiate into macrophages and dendritic cells
19
Q
What do macrophages do?
A
Phagocytize dead cells and pathogens
20
Q
What do dendritic cells do and where are they found?
A
Found in areas of body where contact with external environment is more common (skin, intestine etc) and focus on processing antigens and presenting them to other immune cells
21
Q
What are antigen presenting cells (APC’s) and what are some examples?
A
Macrophages, dendritic cells and b lymphocytes; present antigens for recognition to mediate cell immune response
22
Q
What are the types of adaptive immunity?
A
Cell mediated which is mediated by T lymphocytes or humoral which involves antibody production by b lymphocytes
23
Q
How and where do T lymphocytes develop and mature?
A
T lymphocytes begin to develop in the bone marrow where there precursor cells are formed, then they travel through bloodstream to the thymus where they mature and once maturation is complete the T cells are released into the lymph to perform their immune function
24
Q
True or False: Each T cell becomes reactive to only one specific antigen
A
True
25
What is the function of the major histocompatibility protein complex (MHC)?
The antigen from the pathogen will be presented by a major histocompatibility protein complex (MHC) on surface of the APC indicating that corresponding T cell should perform its function
26
What are the 2 major types of MHC?
Two major types of histocompatibility proteins are MHC 1 and MHC 2
27
What do cytotoxic T cells do?
Cytotoxic T cells (CD8+ T cells) recognize and respond to antigens presented by the MHC 1 complexes and signal the T cells to destroy the cells involved in viruses or developing tumors
28
What do T helper cells do?
T helper cells (CD4 + T cells) recognize and respond to antigens presented by the MHC 2 complexes and release cytokines to stimulate the immune response, causing white blood cells to mature and attack
29
What are memory T cells?
Memory T cells (once reaction has occurred) reactive to the same antigens are formed to allow a quicker and more targeted response
30
What are natural killer T cells?
Natural killer T cells behave similar to the other two types of T cells but respond to antigens presented by other types of cells
31
Where do B lymphocyte develop?
- B lymphocytes begin their development in bone marrow and is completed there
- When B cells are stimulated they create antibodies (immunoglobulins) that have a high affinity for antigens
32
What is the structure of immunoglobulin?
Immunoglobulin structure resembles a Y with antigen binding sites at either end of the top of the Y, each side of the Y has a light chain and a heavy chain which is held together with disulfide bonds, variable portion of structure is the antigen binding region
33
What is active immunity and what is passive immunity?
- Humoral immunity includes both active and passive immunity:
- Active immunity occurs as a result of an immune response (from exposure or vaccination)
- Passive immunity is acquired by the transfer of antibodies from one individual to another (can occur during pregnancy etc.), once antibodies are no longer circulating in immune system the effect of immunity is lost
34
What do immunosuppressive drugs do?
Immunosuppressive drugs are used to lower the immune response to transplant and decrease likelihood of rejection but makes patient immunocompromised since immune system is not functioning at full capacity
35
What is the lymphatic system?
The lymphatic system is a part of the immune system found in the extravascular space of most tissues
36
Where does lymph flow through?
Lymph flows through lymphatic vessels from lymph node to node; lymph nodes and spleen are reservoirs of white blood cells and filters for lymph, removing APC cells and foreign matter and activating immune system when necessary
37
What is the function of the nervous system and what is it composed of?
- Nervous system enable organisms to receive and respond to stimuli from their external and internal environments
- Composed of neurons (specialized nervous tissue) and neuroglia (cells that support and protect neurons)
38
What are the 2 divisions of the nervous system?
Two divisions: Central nervous system and peripheral nervous system
39
What is the primary function of the neuron?
Primary function to convert stimuli into electrochemical signals and conduct these signals throughout the body
40
What is the neuron composed of?
Has dendrites, a cell body and an axon
41
What are dendrites?
Dendrites are cytoplasmic extensions that receive information and transmit it toward the cell body
42
What is the function of the cell body of the neuron?
Cell body (soma) contains the nucleus and controls metabolic activity
43
What is the axon?
Axon is a long cellular process that transmits impulses (action potentials) away from cell body
44
What is the axon hillock?
Between axon and cell body is axon hillock where incoming signals from dendrites are summed
45
What is the function of myelin and what are nodes of ranvier?
- Myelin prevents leakage of signal from axons and allows for faster conduction of impulses
- Gaps between segments of myelin are nodes of ranvier, saltatory (hopping) conduction
46
What is myelin made by?
Myelin is produced by glial cells called oligodendrocytes in the CNS and by schwann cells in the PNS
47
What is resting membrane potential?
Potential difference at rest between the extracellular space and the intracellular space is resting potential and is typically -70 mv (inside of neuron more negative than the outside)
48
What does the Na/K pump pump?
Na+/K+ pump pumps 3 Na out of cell for every 2 K it pumps into cell; cell membrane more permeable to K+ (can flow out and make inside even more negative)
49
What is the threshold potential?
If membrane potential reaches the threshold potential of -55 mV, then voltage-gated Na+ channels open, triggering the action potential
50
What are the 3 phases of action potential?
3 phases of action potential: depolarization, repolarization, hyperpolarization
51
What occurs during action potential?
Depolarization occurs when a cell reaches threshold potential and voltage gated Na+ channels open to allow Na+ into the neuron, cell membrane potential reaches 35 mV and cell is depolarized, then voltage-gated K+ channels open and repolarization occurs, the opening and closing of K+ is slow process which causes hyperpolarization which results in a refractory period (period of time after action potential which new action potentials are difficult to initiate), and then resting potential reestablished
52
What is the purpose of refractory periods?
Refractory periods make the backward travel of action potentials impossible
53
How can nerve impulses travel faster?
The greater the diameter of the axon and the greater its myelination, the faster the impulses travel; larger diameter have greater cross sectional area and have less resistance to diffusion of ions and myelin increases conduction velocity by insulating segments of the acon so the membrane is permeable to ions only in nodes of ranvier
54
What is the synapse?
The synapse is the gap between the axon terminal of one neuron (the presynaptic neuron) and the dendrites of the next neuron (post synaptic neuron)
55
What does the axon terminal have?
Axon terminal has thousands of membrane bound vesicles filled with neurotransmitters (chemical messengers)
56
How are neurotransmitters reused or degraded?
Neurotransmitter can be taken back up into the nerve terminal ( via protein called uptake carrier) where it can be reused or degraded, or it can be degraded by enzymes in the synapse or it can diffuse out of the synapse
57
What are afferent neurons?
Neurons that carry sensory information about the internal or external environment to the brain or spinal cord are called afferent neurons
58
What are efferent neurons?
Neurons that carry motor commands from the brain or spinal cord to various parts of the body are called efferent neurons
59
What are interneurons?
Interneurons participate in local circuits linking sensory and motor neurons in the brain and spinal cord
60
What are nerves?\
Nerves are bundles of axons covered with connective tissue
61
What is a plexus?
Network of nerve fibres is called a plexus
62
What are clustered neuronal cell bodies called in the PNS and in the CNS
Clustered neuronal cell bodies are called ganglia in the PNS and nuclei in the CNS
63
What do neuroglia do and what are the types in the CNS and PNS?
Neuroglia support and protect specialized neuronal cells: 4types in CNS and 2 in PNS SEE WRITTEN NOTES FOR FUNCTION
CNS: Astrocytes, oligodendrocytes, microglia and ependymal cells
PNS: Satellite cells and Schwann cells
64
What does the CNS consist of?
Brain and spinal cord
65
What is the brain?
Brain is a mass of neurons and interprets sensory information, forms motor plans and cognitive function (thinking)
66
What part of the brain is gray and white matter?
Brain has outer portion of cell bodies called gray matter and inner portion of myelinated axons called white matter
67
What are the 3 parts of the brain?
Forebrain (prosencephalon), midbrain (mesencephalon), and hindbrain (rhombencephalon)
68
What does the forebrain consist of?
Forebrain (prosencephalon): consists of the telencephalon and diencephalon, major component of telencephalon is the cerebral cortex which processes and integrates sensory input and motor response (important for memory and creative thought) made of grey matter, telencephalon also has olfactory bulb which is important for smell, diencephalon has thalamus and hypothalamus, thalamus is a relay center for spinal cord and cerebral cortex, hypothalamus controls visceral functions like hunger, thirst sex drive etc. and controls temeprature, blood pressure and endocrine system
69
What does the cerebral cortex do?
cerebral cortex which processes and integrates sensory input and motor response (important for memory and creative thought)
70
What does the thalamus do?
thalamus is a relay center for spinal cord and cerebral cortex,
71
What does the hypothalamus do?
hypothalamus controls visceral functions like hunger, thirst sex drive etc. and controls temperature, blood pressure and endocrine system
72
What does the midbrain do?
Midbrain (mesencephalon): relay center for visual and auditory impulses, also plays a role in motor control
73
What is the hindbrain consisted of?
Hindbrain (rhombencephalon): consists of cerebellum, the pons and the medulla
74
What is the function of the cerebellum?
cerebellum important in maintaining balance, hand-eye coordination etc.
75
What is the function of the pons?
the pons is a relay center for communication between cortex and cerebellum,
76
What does the medulla oblongata do?
the medulla oblongata controls vital functions like heart rate, and breathing
77
What makes up the brain stem?
Midbrain, pons and medulla makeup the brain stem
78
Where is the white and grey matter in the spinal cord?
Outer white matter area with axons and inner gray matter area with nerve cell bodies
79
Where does sensory information enter and motor information leave the spinal cord?
Sensory information enters spinal cord through dorsal horn
| All motor information exits the spinal cord through the ventral horn
80
What are the 2 divisions of the PNS?
Somatic and autonomic
81
What does the somatic nervous system do?
Somatic nervous system innervates skeletal muscles and is responsible for voluntary movement and reflex arcs
82
What does the autonomic nervous system do?
The autonomic nervous system regulates the body’s internal environment without the aid of conscious control, innervates smooth and cardiac muscle
83
What are the subdivisions of the autonomic nervous system and what do they do?
ANS has 2 subdivisions: Sympathetic and parasympathetic
- Sympathetic: increases blood pressure and heart rate, increases blood flow to skeletal muscles, dilates bronchioles to increase gas exchange, uses norepinephrine as primary neurotransmitter
- Parasympathetic: acts to conserve energy and restore the body to resting activity levels, lowers heart rate and increases gut motility, innervates the vagus nerve (thoracic and abdominal viscera), uses acetylcholine as its primary neurotransmitter
84
What does the eye do?
Detects light energy (photons) and transmit information about intensity, color, and shape to the brain
85
What is the sclera?
Eyeball is covered by a thick, opaque layer called sclera (white part of eye)
86
What is the choroid layer and what is the choroid?
- Under the sclera is the choroid layer which helps supply the retina with blood
- Choroid is dark pigmented area that reduces reflection in the eye
87
What is the retina?
Innermost layer of the eye is the retina which contains photoreceptors that sense light
88
What does the transparent cornea do?
Transparent cornea at the front of the eye bends and focuses light rays
89
What does the pupil and iris do?
Light rays travel through opening called the pupil whose diameter is controlled by the iris
90
What does the ciliary muscles do?
The lens, the shape and focal length of which is controlled by the ciliary muscles, focuses the image onto the retina
91
What dos the vitreous humor do?
Vitreous humor is jelly material to help maintain eye shape and optical properties
92
What is the aqueous humor?
Aqueous humor is more watery substance that fills the space between the lens and the cornea
93
What are the 2 main types of photoreceptors and what do they respond to?
- The two main types of photoreceptors are cones and rods
- Cones respond to high intensity illumination and are sensitive to color while rods detect low-intensity illumination and are important in night vision
- Cones have 3 different pigments that absorb red, green and blue wavelengths while rod pigment rhodopsin only absorbs a single wavelength
- There are more rods than cones in the human eye
94
What is the macula and fovea?
Central section of the retina is the macula, has a high concentration of cones, center point of macula is called fovea and only has cones
95
How do photoreceptor cells generate action potentials?
Photoreceptor cells generate an action potential in response to light stimuli, the cells synapse onto bipolar cells which in turn synapse onto ganglion cells which group together to form optic nerve which takes information to the brain
96
What do amacrine and horizontal cells do?
Amacrine and horizontal cells also receive stimuli information from photoreceptors and process the information
97
What is myopia?
Myopia (nearsightedness) occurs when the image is focused in front of the retina
98
What is hyperopia?
Hyperopia (farsightedness) occurs when the image is focused behind the retina
99
What is astigmatism?
Astigmatism is caused by an irregularly shaped cornea
100
What are cataracts?
Cataracts develop when the lens becomes opaque, light can’t enter the eye and blindness results
101
What is glaucoma?
Glaucoma is an increase of pressure in the eye because of blocking of the outflow of aqueous humor, which results in optic nerve damage
102
What are the parts of the ear?
Divided into 3 parts: the outer, middle and inner ear
103
How does sound travel through the ear?
Sound wave first reaches the cartinalegenous pinna (sometimes called auricle) then sound is channeled into the external auditory canal which focuses the soundwave toward the tympanic membrane (eardrum) and the tympanic membrane vibrates with magnitude and frequency of incoming soundwave
104
What are the bones in the middle ear?
Middle ear contains 3 bones: malleus (hammer), incus (anvil), and stapes (stirrup); these bones collectively called ossicles
105
What do the ossicles do?
Ossicles vibrate with same frequency of tympanic membrane and transfer energy to oval window which is smaller and amplifies the vibration
106
What does the inner eat contain and what does it do?
- The inner ear begins after the oval window contains the cochlea and vestibule
- Vibration of oval window pushed against fluid called perilymph resulting in pressure waves that travel through fluid-filled cochlea, pressure waves detected by hair cells which transform mechanical stimuli into action potentials that travel down the auditory nerve and follows auditory pathway until it reaches the auditory cortex which processes auditory information
- Inner ear contains vestibule which is fluid filled and responsible for balance and acceleration detection of the organism
107
What is the function of the skeletal and muscular system?
The skeletal system provides physical support and locomotion while the muscular system generates force
108
What are the major components of the skeleton?
Two major components of the skeleton: cartilage and bone
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What is cartilage?
Cartilage is a type of connective tissue that is softer and more flexible than bone
110
What are chrondrocytes?
Chrondrocytes are cells responsible for making cartilage
111
What are the basic types of bone and what are their structures?
- Two basic types of bone: Compact bone and spongy bone
- Compact bone is dense, makes up 80% of the skeleton, structural units called osteons which have channel called Haversian canal surrounded by circles of bony matrix called lamellae
- Spongy bone is found at ends of long bones, in pelvic bones and skull and vertebrae, is less dense and has interconnecting bony spicules lattice, the cavities in between spicules are filled with yellow or red bone marrow
112
What is red and yellow marrow?
Yellow marrow is inactive and infiltrated by adipose tissue, red marrow is involved in blood cell formation
113
What do osteoblasts do?
Osteoblasts synthesize and secrete the organic constituents of bone matrix, once surrounded by their matrix they mature into osteocytes
114
What do osteoclasts do?
Osteoclasts are large, multinucleated cells involved in bone reabsorption where bone is broken down and calcium (and other minerals) released into blood
115
What are the types of bone formation and how do they occur?
- Bone formation occurs by either endochondral ossification or intramembranous ossification:
- Endochondral ossification: existing cartilage is replaced by bone, usually occurs in long bone formation
- Intramembranous ossification: mesenchymal (undifferentiated or embryonic) connective tissue is transformed into and replaced by bone
116
What does the axial skeleton consist of?
Axial skeleton: Consists of skull, vertebral column, and rib cage
117
What does the appendicular skeleton consist of?
Appendicular skeleton: bones of appendages (limbs) and the pectoral and pelvic girdles
118
What are sutures/immovable joints?
Sutures or immovable joints hold bones of the skull together
119
What do ligaments and tendons connect?
- Ligaments are bone to bone connectors
| - Tendons attach skeletal muscle to bones and bend skeleton at movable joints
120
What is origin and insertion?
Point of attachment of a muscle to a stationary bone is the origin, point of attachment of a muscle to the bone that moves is the insertion
121
What are the types of muscles?
3 types of muscles: smooth, cardiac and skeletal
122
What is the pyramidal system and extrapyramidal system?
- Pyramidal system is able to provide rapid commands to skeletal muscles and various other organs
- Extrapyramidal system can issue somatic motor commands from processing at the unconscious involuntary level
123
What is skeletal muscle responsible for?
Skeletal muscle is responsible for voluntary movements and is innervated by the somatic nervous system
124
In skeletal muscles, what is myofibrils and sarcomeres and the sarcoplasmic reticulum?
- Embedded in fibers are filaments called myofibrils which are further divided into contractile units called sarcomeres
- Myofibrils are enveloped by sarcoplasmic reticulum which stores calcium ions
125
What is the sarcoplasm and the sarcolemma?
- The cytoplasm of a muscle fiber is called sarcoplasm and the cell membrane is called the sarcolemma
- Sarcolemma is capable of propagating action potential and is connected to system of transverse tubules which provides channels for ion flow and can also propagate an action potential
126
What is the structure of skeletal muscle?
- Each fiber is a multi nucleated cell
| - Striated wit light and dark lines
127
What is the structure of sarcomeres?
- Composed of thin filaments (actin) and thick filaments (myosin)
- Has Z lines to define the boundaries of a single sarcomere and anchor thin filaments
- The M line runs down the center of the sarcomere
- The I band is the region containing thin filaments only
- The H zone is the region containing thick filaments only
- The A band spans the entire length of thick filaments and any overlapping portions of the thin filaments
128
What happens to sarcomeres when muscles contract?
When muscles contract, the Z lines move toward each other and the H zone and I band are reduced in size while the A band remains the same
129
What is the neuromuscular junction?
The link between the nerve terminal and the sarcolemma of the muscle fiber is called the neuromuscular junction
130
What are the steps of contraction in muscles?
- Neurotransmitters diffuse across the synaptic cleft and bind to special receptor sites on the sarcolemma and if enough receptors are stimulated, the permeability of the sarcolemma is altered and the action potential is generated
- Once action potential is generated-> conducted along the sarcolemma and T system and into the interior of the muscle fiber causing the sarcoplasmic reticulum to release calcium ions into the sarcoplasm, calcium ions bind to troponin C on the actin filaments where myosin heads can now bind these sites as well, and a power stroke occurs pulling the Z bands closer together and the actin and myosin slide past each other and the sarcomere contracts
131
What is rigor mortis?
Rigor Mortis: muscles contract and become rigid without action potentials (absence of ATP)
132
How can strength of contraction be increased?
Strength of contraction of the muscle can be increased by recruiting more muscle fibers
133
What are the phases of a simple twitch?
A simple twitch is the response of a single muscle fiber to a brief stimulus at or above the threshold stimulus and consists of a latent period, a contraction period, and a relaxation period
134
What is absolute refractory period?
Absolute Refractory Period: period which the muscle is unresponsive to a stimulus, brief relaxation period after contraction
135
What is temporal summation?
Temporal summation: When fibers of a muscle are exposed to very frequent stimuli and the muscle cannot fully relax (tetanus), then the contractions begin to combine becoming stronger and more prolonged
136
What is tonus?
Tonus is a state of partial contraction because muscles are never completely relaxed
137
What is smooth muscle’s structure and function and where is it found?
- Responsible for involuntary actions and is innervated by the autonomic nervous system
- Found in digestive tract, bladder, uterus etc
- Have one centrally located nucleus
- No striations
138
What is the structure and function of cardiac muscle?
- Muscle tissue of the heart
- Myosin and actin arranged in sarcomeres-> striated appearance
- Have one or two centrally located nuclei
139
What is myoglobin?
Myoglobin is a hemoglobin like protein found in muscle tissue that maintains the oxygen supply in muscles by tightly binding oxygen
140
What is the primary source of energy for muscle contraction?
ATP
141
What is creatine phosphate?
In vertebrates: Energy can be temporarily stored in a high energy compound called creatine phosphate
142
How many chambers are in the human heart?
4
143
What is the difference of structure of atria compared to ventricles?
Atria are thin walled while ventricles are muscular
144
What is systemic and pulmonary circulation?
- Right side pumps deoxygenated blood into pulmonary circulation (towards the lungs)
- Left side pumps oxygenated blood into systemic circulation (throughout the body)
145
What is the path of blood returning from the heart?
Blood returning from the body flows through the superior and inferior vena cava into the right atrium, then through the tricuspid valve into the right ventricle, and finally through the pulmonary semilunar valve into the pulmonary arteries to continue to the lungs. Blood returning from the lungs flows through the pulmonary veins into the left atrium, then through the bicuspid/mitral valve into the left ventricle, and finally out through the aortic semilunar values into the systemic circulation through the aorta
146
What are the atrioventricular valves and what is their function?
- AV Valves prevent the back flow of blood into atria
| - Tricuspid and bicuspid valves
147
What are the semilunar valves?
The aortic and pulmonic valves
148
What is the heartbeat composed of?
2 alternating phases of hearts pumping cycle-> systole and diastole
149
What is systole and what is diastole?
Systole: Period when ventricles contract, forcing blood out of the heart into the pulmonary and systemic circulation
Diastole: Period of cardiac muscle relaxation where blood drains into all 4 chambers
150
What is cardiac output and how is it calculated?
Total volume of blood the left ventricle pumps out per minute
Cardiac output = heart rate (bpm) x stroke volume (volume pumped out of left ventricle per contraction)
151
How does the impulse of the heart rate travel and how is it normally regulated?
- Ordinary cardiac contraction originates in and is regulated by the sinoatrial (SA) node located in the wall of the right atrium
- Travel of Impulse: SA node -> AV node -> bundle of His -> Purkinje fibers
152
What are some alternate mechanisms that heart rate is controlled?
-Autonomic nervous system: modifies the rate of heart contraction
—Sympathetic: innervates heart via cervical and upper thoracic ganglia causing an increase in heart rate
—Parasympathetic: Innervates heart via vagus nerve causing a decrease in heart rate
-Hormonal control: Adrenal medulla secretes epinephrine (adrenaline) which increases heart rate
153
What are the types of blood vessels?
Arteries, veins and capillaries
154
What are characteristics of arteries?
Thick walls, muscular, elastic, transport oxygenated blood away from the heart except for pulmonary arteries that take deoxygenated blood from the heart to the lungs
155
What are characteristics of veins?
Thin walls, inelastic, take deoxygenated blood to the heart except for pulmonary veins that take oxygenated blood from the lungs to the heart, flow depends on compression by skeletal muscles, have valves to prevent back flow
156
What are characteristics of capillaries?
Thin walls with single layer of endothelial cells, gases, nutrients, waste and enzymes can readily diffuse, smallest diameter
157
What are lymph vessels and what do they transport?
- Secondary circulatory system
| - Transports excess interstitial fluid (lymph) to cardiovascular system
158
What are lacteals?
Small lymphatic vessels that collect fats in the form of chylomicrons and deliver them into the blood stream
159
What are lymph nodes?
A lymph nodes are swellings on lymph vessels containing lymphocytes that filter the lymph and destroy foreign pathogens
160
What volume of blood do humans have?
4-6 liters
161
What is the composition of blood and what are the components of blood?
- 55% liquid components and 45% cellular components
- Plasma is the aqueous, non-cellular portion of blood, made of a mixture of nutrients, salts, respiratory gases, wastes, hormones and blood proteins
- cellular components of blood: erythrocytes, leukocytes and platelets
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What is plasma?
-Plasma is the aqueous, non-cellular portion of blood, made of a mixture of nutrients, salts, respiratory gases, wastes, hormones and blood proteins
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What are the cellular components of blood?
Erythrocytes, leukocytes and platelets
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What are leukocytes and what is their function?
White blood cells, protective functions, larger than erythrocytes
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What are platelets and what is their function?
Cell fragments that lack nuclei and are involved in clot formation
166
What are erythrocytes and what is their function?
Red blood cells, carry oxygen, has hemoglobin which can bind 4 molecules of oxygen, hemoglobin can also bind carbon dioxide, increased surface area (shape) for gas exchange and greater flexibility, erythrocytes formed from stem cells in bone marrow
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BLOOD TYPES
IN NOTES PAGE 26 REVIEW
168
What are functions of the circulatory system?
- Erythrocytes transport O2 throughout the circulatory system
- Amino acids and simple sugars are absorbed into the blood stream at the intestinal capillaries
- Metabolic waste products diffuse into capillaries to travel to be excreted
169
How does blood clotting occur?
- When platelets see exposed collagen of a damaged vessel, they release a chemical that causes neighboring platelets to adhere forming a platelet plug
- They release thromboplastin (cofactors calcium and vitamin K) which converts plasma protein prothrombin to thrombin (active)
- Thrombin converts fibrinogen to fibrin which traps blood cells to form a clot to prevent blood loss while vessel heals itself
170
What is serum?
The fluid left after blood clotting
171
What is warfarin?
Anticoagulant that inhibits recycling of Vitamin K (inhibits clotting cycle)
172
Where does gas exchange occur in the respiratory system?
Gas exchange between lungs and circulatory system occurs across the thin walls of the alveoli
173
What is the path of travel in the respiratory system?
Nose -> pharynx (throat) -> larynx -> trachea -> bronchi-bronchioles -> alveoli
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What are functions of the respiratory system?
Large area for gas exchange, protect from infection and dehydration, moves air over vocal cord, assists in the regulation of body pH by regulating the rate of CO2 removal from the blood
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What does ventilation mean?
Take in oxygen from atmosphere and eliminate carbon dioxide from the body
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What occurs during inhalation and exhalation?
During inhalation, the diaphragm contracts and flattens, and the external intercostal muscles contract, pushing the rib cage and chest wall up and out. The phrenic nerve innervates the diaphragm and causes it to contract and flatten. These actions cause the thoracic cavity to increase in volume. This volume increase reduces the pressure, causing the lungs to expand and fill with air.
Exhalation is generally a passive process. The lungs and chest wall are highly elastic and tend to recoil to their original positions after inhalation. The diaphragm and external intercostal muscles relax and the chest wall pushes inward. The consequent decrease in thoracic cavity volume causes the pressure to increase which forces air out of the alveoli causing the lungs to deflate
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What is surfactant?
Protein complex secreted by cells in the lung’s, keeps lungs from collapsing by decreasing the surface tension in the alveoli
178
What is ventilation regulated by?
Ventilation is regulated by neurons located in the medulla oblongata and is affected by levels of hydrogen, carbon dioxide and oxygen
179
How does gas exchange in the lungs occur?
- Pulmonary capillaries surround the alveoli where gas exchange occurs
- Gas travel from regions of high partial pressure to regions of low partial pressure
- Oxygen diffuses from alveolar air into the blood while CO2 diffuses from the blood into the lungs
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What is total lung capacity refer to?
Max volume of air the lungs can hold
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What does tidal volume refer to? What does residual volume refer to? What does vital capacity refer to? What does exploratory reserve volume refer to? What does inspiratory reserve volume refer to?
Tidal Volume: Volume of air moved during normal resting breath
Residual Volume: Air in lungs to keep alveoli patent
Expiratory Reserve Volume: Volume of air left in lungs at end of normal resting exhalation
Inspiratory Reserve Volume: Volume of air of a deep breath in
Vital Capacity: Volume of air moved during a max inhalation followed by a max exhalation
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What are the main steps of the digestive system?
Ingestion -> Digestion -> Absorption -> Secretion
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What is intracellular digestion and what is extracellular digestion?
Intracellular digestion: Occurs within cell (usually in membrane bound vehicles)
Extracellular digestion: Occurs outside of cell within a lumen/tract
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What makes up the human digestive tract?
Oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, anus
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What are the accessory glands of the digestive system?
Salivary glands, pancreas, liver, and gall bladder
186
What is the function of saliva?
- Lubricates and begins digestion of food
| - Contains salivary amylase (ptyalin) to hydrolyze starch to maltose
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What does the esophagus do? And what is the cardiac/lower esophageal sphincter?
- Muscular tube that transports bolus from oral cavity to stomach via peristalsis
- Has lower esophageal (cardiac) sphincter to protect esophagus from acidic stomach
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What is the stomach’s function and structure?
- Large muscular organ that stores and digests food
- Has pyloric sphincter
- Chemical digestion via gastric mucosa and gastric pits and glands
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What are mucous cells, chief cells, and parietal cells?
Mucous cells: in gastric pits secrete mucous to protect stomach lining from acidity
Chief Cells: In gastric glands make pepsinogen which is converted to pepsin and breaks down proteins
Parietal Cells: In gastric glands, makes HCl which kills bacteria and produces intrinsic factor which is needed for absorption of vitamin B12
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What occurs in the small intestine, what is contained in it and what is it’s structure?
- Chemical digestion
- 3 sections: duodenum, jejunum, and ileum
- Pancreatic secretions give high/basic pH in small intestine
- Enzymes: Lipases, aminopeptidases and disaccharidases
- Vili increases surface area and where most absorption occurs
- Has passive and active absorption
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What is the structure and function of the liver?
- Produces bile that is stored in the gall bladder before being released into the small intestine
- Bile emulsifies (reduces size) of fats by increasing the fats surface area so it can be digested by enzymes
- Detoxifies blood before general circulation
- Stores glycogen, converts ammonia to urea, synthesizes proteins and cholesterol metabolism
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What is the function of the pancreas?
- Releases amylase, lipase and trypsinogen
- Trypsinogen activated by enterokinase to become trypsin
- Trypsin enters small intestine to cleave and activate other enzyme precursors
- Secretes bicarbonate juice to neutralize chyme
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What is the function of the large intestine and rectum?
- Absorbs salt and water
- Has gut flora -> symbiotic bacteria that produce vitamins and digest nutrients that host cannot
- Has rectum for storage of feces
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What are all the digestive hormones and what is the function?
Gastrin: Produced in G cells of duodenum, stimulate histamine and pepsinogen secretion, increases gastric blood flow
Intrinsic factor: Secreted by parietal cells of stomach that absorb vitamin B12
Cholecystokinin (CKK): produced and stored in I cells of duodenum and jejunum mucosa, stimulates pancreatic enzyme and somatostatin secretion and acts as a hunger suppressant
Secretin: Made and stored in S cells of upper intestine, stimulates secretion of bicarbonate substances from pancreas and inhibits gastric acid production
Ghrelin: Made in brain and gut, Hunger hormone
Leptin: Made in adipose tissue to reduce hunger
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What is excretion?
Removal of metabolic wastes produced in the body
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What is elimination?
Removal of indigestible material like dietary fiber
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What are the principal organs of excretion?
Lungs, liver, skin, and kidneys
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What is the function of the kidneys and what are they made of?
- Function: Regulate the concentration of salt and water in the blood through formation and excretion of urine
- Made of million of functional units called nephrons
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What are the 3 regions of the kidney?
Outer cortex, inner medulla and renal pelvis
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What are the main steps of urine formation? Describe them.
Filtration: Passive process (hydrostatic pressure of blood), blood pressure forces blood plasma to enter glomerulus and is now called filtrate
Secretion: Nephron secretes waste (acid, ions and other metabolites) from interstitial fluid into filtrate by both passive and active transport
Reabsorption: Essential substances (glucose, salts and amino acids) and water are reabsorbed from the filtrate and returned to blood, occurs mostly in proximal convulated tubule and is active but water movement is passive and follows solute movements
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What is the path of urine out of the body?
Urine-> Ureter -> Urinary Bladder -> Urethra
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What is the function of the glomerulus?
Site of filtration, plasma and blood solutes are filtered and become filtrate, based on size exclusion (no cells/proteins entering)
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What is the function of the Proximal Convuluted tube?
Amino acids, glucose, water soluble vitamins and a majority of salts are reabsorbed along with water, also site of secretion for waste products like hydrogen and K ions, ammonia and urea (HUNK), reabsorbed solutes re-enter circulation via peritubular capillaries which are part of the vasa recta (capillaries that surround the nephron)
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What is the function of the Loop of Henle?
Descending limb is only permeable to water which leaves filtrate (osmosis), ascending limb is only permeable to salts which are removed from filtrate, thick ascending limb (diluting segment) has increased amount of mitochondria for ATP production to pump out Na+ and Cl- from the filtrate
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What is the function of the distal convuluted tubule?
Responsible for reabsorption and secretion, responds to aldosterone which promotes sodium reabsorption and therefore water reabsorption
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What is the function of the collecting duct?
Responsive to aldosterone and antidiuretic hormone (ADH)
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What is the osmolarity gradient in the urinary system?
- Osmolarity gradient from the cortex to the inner medulla
| - Greater the osmolarity gradient, the more concentrated the urine
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How do the kidneys play a role in homeostasis?
Kidney is able to regulate blood osmolarity, blood volume, blood pH and excrete waste products via hormonal control
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How do hormones affect the urinary system?
- Aldosterone regulates the active transport of sodium and potassium, causes reabsorption of water (osmosis)
- Antidiuretic Hormone (ADH) opens aquaporins affecting water reabsorption
- Both ADH and aldosterone cause a decrease in urine output and increase in blood pressure (compensate for dehydration or low blood pressure)
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How does urine affect blood pH?
The more H+ secreted into urine, the more basic the blood pH
| The more HCO3 excreted, the more acidic the blood
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What do endocrine glands do?
Make and secrete hormones directly into the circulatory system
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What do exocrine glands do?
Secrete substances transported by ducts
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What are glands/organs that make/secrete hormones?
Pituitary, hypothalamus, thyroid, parathyroid, adrenals, pancreas, testes, ovaries, kidneys, pineal glands, GI glands, heart, thymus
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What is the function of the hypothalamus?
- Regulatory center of endocrine system
- Part of forebrain located above the pituitary gland
- Recieves transmission from brain and peripheral nerves
- Hypothalmic hormones regulate pituitary gland secretions via a negative feedback loop
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What is Gonadotropin Releasing Hormone (GnRH)?
Stimulates the anterior pituitary to release FSH (follicle stimulating hormone) and LH (Luteinizing hormone)
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What is Corticotropin-releasing factor/hormone (CRF/ CRH)?
Signals the pituitary glands to release ACTH
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What is thyrotropin releasing hormone (TRH)?
Stimulates the anterior pituitary to release thyroid hormones T3 and T4
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What is the growth hormone releasing hormone (GHRH)?
Stimulates the anterior pituitary to release growth hormone
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What is the structure and location of the pituitary gland?
Trilobed gland at the base of the brain, below hypothalamus and connected to it by a cord called the infundibulum
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What types of hormones does the anterior pituitary make?
Makes direct hormones that directly act on target organs and tropic hormones that stimulate other endocrine glands to release hormones
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What are the tropic hormones of the anterior pituitary and what do they do?
Follicle Stimulating Hormone (FSH): in women causes the maturation of ovarian follicles (secretes estrogen) and in males stimulates the maturation of seminiferous tubules and sperm production
Luteinizing hormone (LH): in women stimulates ovulation and maintenance of corpus Luteum and regulating progesterone secretion, in males it stimulates the interstitial cells of testes to make testosterone
Adrenocorticotropic hormone (ACTH): stimulates the adrenal cortex to make and secrete glucocorticoids and is regulated by the CRF
Thyroid Stimulating Hormone (TSH): stimulates the thyroid gland to make and release thyroid hormones thyroxine (T4) and triiodothyronine (T3)
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What are the direct hormones of the anterior pituitary and what do they do?
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Prolactin: stimulates milk production in female mammary glands
Endorphins: Neurotransmitters with pain relieving properties
Growth Hormone (GH): Promotes bone and muscle growth, also promotes protein synthesis and lipid mobilization and catabolism
Melanocyte-Stimulating Hormone (MSH): Secrete by intermediate lobe, in mammals it plays role in tanning (sun-induced darkening) but in amphibians in dark environments it is released to cause darker skin for better camouflage
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What does the posterior pituitary do?
- does not synthesize hormones
- Stores and secretes the peptide hormones oxytocin and antidiuretic hormone which is produced by the neurosecretory cells of the hypothalamus
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What is the function of oxytocin?
-Secreted during childbirth and increases the strength and
frequency of uterine muscle contractions through positive feedback loops, oxytocin secretion is also induced by suckling because Oxytocin stimulates milk secretion in the mammary glands
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What is the function of the antidiuretic hormone (ADH)?
- increases water permeability in the collecting duct of the nephron which promotes water reabsorption and increasing blood volume (increases blood pressure and decreases blood osmolarity), regulated by negative feedback loops
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Where are the adrenal glands located and what do they consist of?
Above the kidneys, consist of adrenal cortex and adrenal medulla
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What does the adrenal cortex do?
In response to stress, ACTH (produced by anterior pituiatary) stimulates adrenal cortex to produce steroid hormones (adrenocortical steroids/ corticosterioids), steroids bind to transport proteins called transcortins in blood stream and they affect which genes are transcribed in target cells and at what rate
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What are the 3 major classes of coricosteroids?
Glucocorticoids: Such as cortisone and cortisol, involved in glucose regulation and protein metabolism, raise blood glucose levels by promoting protein breakdown and decreasing protein synthesis, promote peripheral use of lipids and have anti-inflammatory effects
Mineralocorticoids: Aldosterone, regulate plasma levels of Na and K, causes reabsorption of Na (and water passively via osmosis) into nephron (increase blood volume and pressure), stimulated by angiotensin 2 (regulated by lungs and kidneys) and inhibited by AND (atrial nartriuretic peptide made by heart)
Androgens: Male sex hormones, secreted in small quantities in both men and women, in men -> most androgens produced by testes
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What does the adrenal medulla do and release?
- Produces epinephrine (adrenaline) and norepinephrine (noradrenaline) (both are in class of catecholamines)
- Both hormones are neurotransmitters
- Epinephrine increases the conversion of glycogen to glucose in the liver and muscle tissue -> increase blood glucose level and basal metabolic rate
- fight or flight response
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What is the structure and the function of the thyroid:
- Controlled by TSH (from anterior pituitary) which is stimulated by TRH (hypothalamus)
- Located in front of trachea
- 2 major function: Metabolism regulation through release of T3 and T4 and regulation of blood calcium levels through release of calcitonin
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What are the thyroid hormones?
Thyroxine (T4) and Triiodothyronine (T3) made from the
glycoprotein thyroglobulin which is made in thyroid cells
↳ 3 and 4 is # of iodine atoms attached to hormone
↳ T3 is more potent then T4, they are both transported via plasma proteins (once unbound can enter cell to elicit response), T4 is made and Secreted by thyroid gland
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What is hypothyroidism?
Thyroid hormones are under secreted or not secreted at all, results in low metabolism levels, treated with supplementation of thyroid hormones
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What is Hyperthyroidism?
Thyroid is overstimulated and over secretion of thyroid hormones, results in high metabolism levels, treated with anti-thyroid medication or ablation of thyroid with radiation
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What is calcitonin do?
- Decreases plasma Ca2+ concentration by inhibiting the release of Ca2+ from bone (promotes storage of Ca2+ in bones)
- Secretion is regulated by plasma Ca2+ levels
- Antagonistic to parathyroid hormone
- Not affected by hypothalamus or pituitary gland
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What does GnRH do?
- Gonadotropin releasing hormone from the hypothalamus acts on the anterior pituitary to release gonadotropins (LH and FSH)
- In men LH and FSH acts on testes to produce testosterone and maturation of sperm
- In women; LH and FSH cause secretion of estrogen and progesterone
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What does the parathyroid glands do?
↳ embedded in posterior surface of the thyroid
↳ glands make and secrete parathyroid hormone (PTH) which
regulates plasma Ca2+ concentration
↳ PTH raises Ca2+ concentration in the blood by stimulating release of Ca2+ from the bone and decreasing Ca excretion in kidneys
↳ done in response to low Ca levels in blood
→ Calcium in bone is bonded to phosphate therefore PTH compensates
by stimulating excretion of phosphate by the kidneys
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What is the structure/function of the pancreas?
- Both an exocrine and endocrine organ
- Small glandular structures called the islets of Langerhans made of alpha and beta cells
- Alpha cells make and secrete glucagon while beta cells make and secrete insulin
- Endocrine hormones regulated via negative feedback
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What is glucagon do?
Released when blood glucose levels are low and stimulates conversion of glycogen to glucose and gluconeogenesis to increase blood glucose levels
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What does insulin do?
Released in response to high blood glucose levels, results in uptake of glucose (e.g. stimulates synthesis of fats from glucose) to lower blood glucose levels
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How do kidneys regulate blood volume and pressure?
The kidneys play a crucial role in the renin-angiotensin aldosterone (RAA) system, which heavily regulates both blood volume and blood pressure. When blood volume falls, the kidneys produce renin- an enzyme that converts the plasma protein angiotensinogen to angiotensin 1. Angiotensin 1 (produced by the liver) is converted to angiotensin 2, which stimulates the adrenal cortex to secrete aldosterone. Aldosterone helps restore blood volume by increasing sodium reabsorption by the kidneys, leading to an increase in fluid retention. Kidneys also make erythropoietin (EPO) which is a glycoproteins that stimulates red blood cell production
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What are the different gastrointestinal hormones?
- Gastrin is released after ingesting food, is carried to the gastric glands and stimulates them to secrete HCl
- Secretion of pancreatic juice is under hormonal control
- Secretin is released by small intestine when chyme enters from stomach and stimulates secretion of bicarbonate solution from pancreas to neutralize the chyme
- Cholecystokinin is released by small intestine in response to the presence of fats and cause contraction of gall bladder and release of bile into small intestine
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What is the pineal gland structure/function?
- At the base of the brain
- Secretes the hormone melatonin-> believed to play a role in regulation of circadian rhythms
- Melatonin secretion is regulated by light/dark cycles in environment
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What are the 2 major groups of hormones?
Peptide or steroid hormones
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What are peptide hormones?
- Act as first messengers
- Second messenger relays message from extracellular peptide hormone to cytoplasmic enzymes and initiate a series of reactions in the cell
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What are steroid hormones?
- Belong to a class of cholesterol derived molecules with characteristic ring structure
- Lipid soluble and cross phospholipid bilayer and enter target cells directly and bind specific receptor proteins in cytoplasm
- Receptor hormone complex enters nucleus and activates expression of specific genes (change in transcription and protein synthesis)
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What is sexual production?
Genetic material of 2 organisms combine and results in a genetically unique offspring, fusion of 2 gametes
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What does sexual reproduction require?
1. Production of functional sex cells/gametes
2. Union of these cells (fertilization or conjugation) to form a zygote
3. Development of the zygote into another adult
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What is gametogenesis and where does it occur?
- Production of gametes
- Occurs in specialized organs called gonads
- Male gonads-> testes -> produce sperm (spermatogenesis)
- Female gonads -> ovaries -> produce oocytes (eggs) (oogenesis)
- Hermaphrodites-> Have both functional male and female gonads
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What is fertilization?
Union of egg and sperm nuclei to form zygote with a diploid number of chromosomes
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What is the pathway of sperm through the male reproductive system?
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Seminiferous tubules
Epididymis
Vas Deferens
Ejaculatory duct
Next
Urethra
Penis
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What are the male sex hormones?
FSH: Acts on Sertoli cells (in seminiferous tubules) to support development of maturing sperm
LH: Acts on Leydig cells to stimulate testosterone production in the testes
Testosterone: Made in testes, induces male sexual differentiation
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What is the process of spermatogenesis?
↳ diploid cells called spermatogonia differentiate into diploid
cells called primary spermatocytes, which undergo meiotic
division to yield 2 haploid secondary spermatocytes and 2nd
meiotic division produces 4 haploid spermatids that mature to create spermatozoa
↳ mature sperm has acrosome which is cap-like structure
w/ enzymes needed to penetrate covering of ovum
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How does oogenesis occur?
- Production of female gametes, occurs in ovarian follicles
- At birth, most of the immature ova, known as primary oocyte, that a female will produce during her lifetime have already formed. Primary oocytes are diploid cells that form by mitosis in the ovary. One primary oocyte per month completes meiosis 1, yielding 2 daughter cells of unequal size, a secondary oocyte and a small cell known as a polar body. The secondary oocyte is expelled from the follicle during ovulation, while the polar body gets reabsorbed. Meiosis 2 does not occur until fertilization. The oocyte cell membrane is surrounded by 2 layers of cells, the inner zone pellucida layer and the outer corona radiata layer. Meiosis 2 is triggered when these layers are penetrated by a sperm cells, yielding 2 haploid cells - a mature ovum and another polar body.
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What are the female sex hormones?
- Secretion of estrogen and progesterone regulated by LH and FSH which is regulated by GnRH
- Estrogen: Steroid hormone, needed for female maturation and responsible for thickening endometrium, secreted by corpus luteum and ovarian follicles
- Progesterone: Steroid hormone secreted by corpus luteum during luteal phase of menstrual cycle, stimulates development and maintenance of endometrium in preparation for implantation
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What are the phases of the menstrual cycle?
↳ Follicular phase: cessation of menstruation from previous cycle,
decrease in progesterone, FSH stimulates follicle growth, estrogen levels increase
↳ Ovulation: Mature ovarian follicle bursts and releases ovum into fallopian
tube, Surge in LH and peak in estrogen levels, follicle exterior transforms
into the corpus luteum, after ovulation estrogen and progesterone levels
decline
↳ Luteal Phase: LH levels start to drop through interaction w/ corpus luteum,
degradation of corpus luteum triggers menstruation
→ Menstruation: If ovum is not fertilized → the corpus luteum atrophies due
to decrease in LH, resulting drop in progesterone and estrogen levels cause
the endometrium to shed (menstrual flow), if fertilization occurs →
menstruation avoided and resulting zygote and developing placenta produce
hCG (human chorionic gonadotropin)
256
What occurs during fertilization?
↳ egg can be fertilized 12-24 hours after ovulation, and often
occurs in widest portion of fallopian tube
↳ first sperm must penetrate Corona radiata (sperm uses enzymes it secretes to penetrate it), acrosome is responsible for penetrating the Zona pellucida (releases enzymes that digest this layer and allow sperm
to come in direct contact w/ ovum cell membrane), forms acrosomal process when in contact and the sperm nucleus can now enter the ovums cytoplasm, cortical reaction in ovum occurs causing Ca ions to be released into cytoplasm resulting in formation of fertilization membrane which prevents multiple fertilization
257
What occurs during monozygotic twins and dizygotic twins?
↳ Monozygotic (Identical) Twins: Single zygote splits into 2 embryos, identical
↳ Dizygotic (fraternal) twins: 2 ova are released in 1 ovarian cycle and fertilized by 2 different sperm, develop their own Stuff, nonidentical
258
What is embryology?
The study of the development of a unicellular zygote into a complete, multicellular organism
259
What are the early development stages?
Fertilization: Occurs within 12-24 hours after ovulation
Cleavage: Rapid mitosis divisions, causes increase in cell number with increased ratio of nuclei to cytoplasm, also increases surface area to volume ratio of cell improving gas and nutrient exchange, solid ball of embryonic cells called morula forms, blastulation begins when the morula develops a fluid filled cavity called the blastocoel, which by 4th day becomes a hollow sphere of cells called the blastula
Implantation: Outer layer of cells of the blastula called the trophoblast plays a role in implantation of blastula in the uterus and provides nutrients to embryo and develops into part of the placenta
Placenta Development: Placenta and umbilical cord develop in first few weeks after fertilization
260
What is the amnion?
A thin tough membrane containing a watery fluid called amniotic fluid which acts as a shock absorber of external pressure during gestation and localized pressure from uterine contractions during labor
261
What forms the placenta?
Begins with the chorion which is a membrane that completely surrounds the amnion, the chorion assists with transfer of nutrients from the mother to the fetus. The allantois develops as an outpocketing of the gut and the blood vessels of the allantoic wall enlarge and become the umbilical vessels, which will connect the fetus to the developing placenta. The yolk sac, the site of early development of blood vessels, becomes associated with the umbilical vessels
262
What is the gastrulation?
After week 2, the embryo is fully implanted in uterus and blastula transforms into 3 layer structure called gastrula
263
What is the ectoderm, mesoderm and endoderm form?
Ectoderm: (outer layer), integumentary system, lens of eye, retina, and nervous system
Mesoderm: (middle layer) muscoskeletal system, circulatory system, excretory system, gonads, connective tissue etc.
Endoderm: (inner layer), epithelial lining of digestive and respiratory tracts and parts of liver, pancreas, thyroid and bladder lining
264
What is neuralation?
-Starts before week 3, regions of germ layers begin to develop into a rudimentary nervous system
265
What are the final steps of development?
Organogenesis: Body organs begin to form, cells interact, differentiate, change physical shape, proliferate and migrate
Growth: Organs increase in size, continual process
Gametogenesis: Eggs develop in women and sperm develop in men which permits reproduction to occur
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What occurs in the trimesters of gestation for a human?
First Trimester: Major organs begin to develop, heart beats after 22 days, after 8 weeks embryo now called fetus
Second Trimester: Fetus grows, moves in amniotic fluid, face appears and toes and fingers elongate
Third Trimester: Rapid growth and brain development, antibodies selectively transported from mother to fetus
267
What occurs during birth labor?
1. Cervix thins and dilates and amniotic sac ruptures releasing fluids
2. Rapid contractions and birth of baby
3. Uterus contracts and expels placenta and umbilical cord
268
What are congenital disorders? What is teratogens and vertical transmission?
- Errors occur during fetal development often because of deleterious genes or problems with gestation environment
- Teratogens: Chemical and biological agents that cause these disorders
- Vertical transmission: mother passes infection directly to her developing offspring
269
What occurs in plant fertilization?
In angiosperms (flowering plants), double fertilization occurs-> one sperm cells fertilizes the egg cell, and the other fuses to form the endosperm, which provides nutrients to the developing embryo in the seed. In contrast, gymnosperms, such as conifers, have “naked seeds”; they do not have endosperm. Some plants can produce seeds without fertilization or reproduce without the production of seeds by asexual reproduction, which gives rise to individuals genetically identical to the parent.
In the alternation of generations life cycle, plants can fluctuate between asexual diploid and sexual haploid stages, known as the sporophyte and gametophyte generations respectively. The diploid sporophyte produces haploid spores via meiosis, which matures into a haploid gametophyte. This gametophyte goes on to produce gametes via mitosis. The gametes fuse to produce a zygote
270
What are the parts of plant embryo?
Epicotyl: Precursor of the upper stem and leaves
