Chapter 4 - Tissue Level Flashcards
(160 cards)
0
Q
What is the science that deals with the study of tissues?
A
Histology
1
Q
What is a tissue?
A
A group of cells that function together to carry out specialized activities
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Q
What is a pathologist?
A
A physician who specializes in laboratory studies of cells and tissues to help other physicians make accurate diagnoses
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Q
What are the 4 different kinds of tissues?
A
- Epithelial tissue
- Connective tissue
- Muscular tissue
- Nervous tissue
4
Q
Describe epithelial cells.
A
Cover body surfaces and line hollow organs, body cavities, and ducts, also form glands
Allows the body to interact with its internal and external environments
5
Q
Describe connective tissue.
A
Protects and supports the body and its organs
Helps bind organs together, store energy reserves as fat, and help provide the body with immunity to disease causing organisms
6
Q
Describe muscle tissue.
A
Composed of cells specialized for contraction and generation of force
Generates heat that warms the body
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Q
Describe nervous tissue.
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Detects changes in a variety of conditions inside and outside the body and responds by generating electrical signals called nerve action potentials that activate muscular contraction and glandular secretions
8
Q
What is a biopsy?
A
The removal of a sample of living tissue for microscopic examination
9
Q
What are cell junctions?
A
Contact points between the plasma membranes of tissue cells
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Q
What are the 5 different types of cell junctions?
A
- Tight junctions
- Adherens junctions
- Desmosomes
- Hemidesmosomes
- Gap junctions
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Q
Which type of cell junction functions in communication between adjacent cells?
A
Gap junctions allow cellular communications via passage of electrical and chemical signals between adjacent cells
12
Q
What are tight junctions?
A
Consist of weblike strands of transmembrane proteins that fuse together the outer surfaces of adjacent plasma membranes to seal off passageways between adjacent cells
13
Q
Where do tight junctions mainly occur?
A
Stomach, intestines, bladder
Inhibit the passage of substances between cells and prevent the contents of these organs from leaking into the blood and surrounding tissues
14
Q
What are adherens junctions?
A
Contains plaque
A dense layer of proteins on the inside of the plasma membrane that attaches both to membrane proteins and to microfilaments of the cytoskeleton
Transmembrane glycoproteins called cadherins join the cells
Each cadherin inserts into the plaque from the opposite side of the plasma membrane
15
Q
What is an adhesion belt?
A
Adherens junctions often form an adhesion belt b/c they encircle the cell
16
Q
What are desmosomes?
A
Contains plaque
Have transmembrane glycoproteins that extend into the intercellular space between adjacent cell membranes and attach cells to one another
Plaque does NOT attach to microfilaments
Plaque attaches to elements of the cytoskeleton known as intermediate filaments
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Q
Where are desmosome junctions common?
A
Among the cells the make up the epidermis and among cardiac cells of the heart
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Q
What are hemidesmosome junctions?
A
Resemble desmosomes but they do not link adjacent cells
The transmembrane glycoproteins in hemidesmosomes are integrins rather than cadherins
Anchor cells not to each other but to the basement membrane
19
Q
What are gap junctions?
A
Membrane proteins called connexins form tiny fluid filled tunnels called connexons that connect neighbouring cells
Plasma membranes of gap junctions are not fused together but are separated by a small gap
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Q
What is the function of connexons in gap junctions?
A
Ions and small molecules can diffuse from the cytosol of one cell to another
21
Q
What are some special functions of gap junctions?
A
Allow cells in a tissue to communicate
Enable nerve and muscle impulses to spread rapidly among cells
22
Q
What the main differences between epithelial tissue and connective tissue?
A
- Epithelial tissue many cells are packed tightly together, little or no extracellular matrix. Connective tissue has a lot of extracellular material separates cells, cells are widely scattered
- Epithelial tissue has no blood vessels. Connective tissue has a significant network of blood vessels.
- Epithelial tissue almost always form surface layers and are not covered by another tissue
* epithelial tissues is almost always found adjacent to blood vessel rich connective tissue
23
Q
What does epithelial tissue consist of?
A
Cells arranged in continuous sheets, in either single or multiple layers
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What are the three major functions of epithelial tissue?
1. Selective barriers that limit or aid the transfer of substances into and out of the body
2. Secretory surfaces that release products produced by the cells onto their free surfaces
3. Protective surfaces that resist the abrasive influences of the environment
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What is the apical (free) surface?
Faces the body surface, a body cavity,
the lumen (interior space) of an internal organ, or a tubular duct the receives cell secretions
* may contain cilia or microvilli
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What is the lateral surface?
Face adjacent cells on either side
| May contain tight junctions, adherens junctions, desmosomes and/or gap junctions
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What is the basal surface?
Opposite side of the apical surface
Adhere to extracellular materials such as the basement membrane
Hemidesmosomes anchor the basal surface to the basement membrane
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What relationship between epithelial tissues and connective tissues is important for the survival and function of epithelial tissues?
Epithelial tissues are avascular, they depend on the blood vessels in connective tissues for oxygen, nutrients, and waste disposal
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What are the functions of the basement membrane?
Provides physical support for the epithelium and plays a part in growth and wound healing, restriction of molecule movement between tissues and flood filtration in the kidneys
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What is found between epithelial tissues and connective tissues?
Basement membrane
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What is the basement membrane?
A thin extracellular layer that commonly consists of two layers, the basal lamina and reticular lamina
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What is the basal lamina?
Is closer to and secreted by, the epithelial cells
Contains proteins such as laminin and collagen
Attach epithelial cells to the basement membrane
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What is the reticular lamina?
Closer to the underlying connective tissue
| Contains proteins such as collagen called fibroblasts
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Do epithelial tissues have a high or low rate of cell division?
High - allows them to constantly renew, and repair themselves
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What are the two types of epithelial tissues?
1. Covering and lining epithelium
| 2. Glandular epithelium
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What are covering and lining epithelium?
Forms the outer covering of the skin and internal organs
Forms the inner lining of blood vessels, ducts, body cavities
Interior of respiratory, disgusting, urinary and reproductive systems
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What are glandular epithelium?
Makes up the secreting portion of glands such as the thyroid, adrenal and sweat glands
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What cell shape is best adapted for the rapid movement of substances from one cell to another?
Squamous cells
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What two characteristics define epithelial tissues?
1. Arrangement of cells into layers, depending on function
| 2. The shapes of the cells, depending on their function
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What are the three different kinds of arrangement of layers of cells?
1. Simple
2. Pseudostratified
3. Stratified
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What are the four different kinds of cell shapes?
1. Squamous
2. Cuboidal
3. Columnar
4. Transitional
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Describe simple epithelium and its functions.
Single layer of cells
| Functions in diffusion, osmosis, filtration, secretion, or aborption
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What is secretion?
The production and release of substances such as mucus, sweat or enzymes
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What is absorption?
The intake of fluids or other substances such as digested food from the intestinal tract
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Describe pseudostratified epithelium and its function.
Appears to have multiple layers b/c cell nuclei lie at different levels
Not all cells each the apical surface
All cells rest on the basement membrane
Cells that do extend to the apical surface may contain cilia, other (goblet cells) secrete mucus
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Describe stratified epithelium and its function
Consists of two or more layers of cells that protect underlying tissues in locations where there is considerable wear and tear
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Describe squamous cells and their function
Thin, which allow for the rapid passage of substances through them
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Describe cuboidal cells and their function
Are as tall as they are wide, like a square
May have microvilli at their apical surface
Function in either secretion or absorption
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Describe columnar cells and their function
Much taller than they are wide
Protect underlying tissues
May have microvilli or cilia at their apical surface
Function in either secretion or absorption
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Describe transitional cells and their function
Can change shape
From squamous to cuboidal and back
Organs such as the urinary bladder stretch
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What are the 4 different kinds of simple epithelium?
1. Simple squamous
2. Simple cuboidal
3. Simple columnar
4. Pseudostratified columnar
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What are the 4 different kinds of stratified epithelium?
1. Stratified squamous
2. Stratified cuboidal
3. Stratified columnar
4. Transitional epithelium
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What is a Pap test or Pap smear?
Collection and microscopic examination of epithelial cells that have been scraped off the apical layer of tissue
Often from the vagina to test for cancer
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What are goblet cells?
Are modified columnar epithelial cells that secrete mucus at their apical surfaces
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What is keratin?
A tough, fibrous intracellular protein that helps protect skin and underlying tissues from heat, microbes and chemicals
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What is the function of glandular epithelium?
Secretion, which is accomplished by glandular cells that often lie in clusters deep to the covering and lining epithelium
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What is a gland?
A single cell or group of cells that secrete substances into ducts (tubes), onto a surface or into the blood
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How are glands classified?
As either endocrine or exocrine
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What are endocrine glands?
Hormone secretions
Enter interstitial fluid and diffuse directly into bloodstreams without flowing through a duct
Have far-reaching effects because they are distributed throughout the whole body
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What are exocrine glands?
Secrete their products into ducts that empty into the surface of a covering and lining epithelium (such as skin surface)
Have limited effects
Some would be harmful if they entered the bloodstream
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How are exocrine glands classified structurally?
Unicellular or multicellular
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What are unicellular glands?
Single celled glands
| Goblet cells
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What are multicellular glands?
Composed of many cells that form a distinctive microscopic or macroscopic organ (sweat, oil or salivary glands)
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What are goblet cells?
Unicellular exocrine glands that secrete mucus directly onto the apical surface of a lining epithelium
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How are multicellular glands categorized?
1. Whether their ducts are branched or unbranched
| 2. The shape of the secretory portions of the gland
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What is a simple gland?
If the duct of a gland does not branch
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What is a compound gland?
If it has branches
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What are tubular glands?
Have tubular secretory parts
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What are acinar glands?
Glands with rounded secretory portions
| Also called alveolar glands
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What are tubuloacinar glands?
Have both tubular and more rounded secretory parts
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What are the 5 combinations of simple multicellular exocrine glands?
1. Simple tubular
2. Simple branched tubular
3. Simple coiled tubular
4. Simple acinar
5. Simple branched acinar
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What are the 3 combinations of compound multicellular exocrine glands?
1. Compound tubular
2. Compound acinar
3. Compound tubuloacinar
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How are exocrine glands classified functionally?
1. Merocrine glands
2. Apocrine glands
3. Holocrine glands
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What are merocrine glands?
Secretions are synthesized on ribosomes attached to the rough ER, processed, sorted and packaged by the Golgi complex and released from the cell by exocytosis
(Salivary and pancreas)
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What are apocrine glands?
Accumulate their secretory product on their apical surface of the secreting cell. Then, that portion of the cell pinches off by exocytosis from the rest of the cell to release the secretion
(Mammary glands)
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What are holocrine glands?
Accumulate a secretory product in their cytosol. As the secretory cell matures, it ruptures and becomes the secretory product
Secretion contains a large amount of lipids
(Sebaceous glands in the skin)
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Describe the general features of connective tissue.
They bind together, support, and strengthen other body tissues; protect and insulate internal organs; compartmentalize structures such as skeletal muscles; serve as major transport system within the body; primary location of stored energy reserves and are the main source of immune responses
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What two basic elements are connective tissues composed of?
1. Extracellular matrix
| 2. Cells
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What is extracellular matrix?
The material located between its widely spaced cells
| Consists mainly of protein fibres and ground substance (material between cells and protein fibres)
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What kind of cell gives rise to connective tissues?
Embryonic cells called mesenchymal cells
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What are the characteristics of "blast" cells?
Retain the capacity for cell division and secrete the extracellular matrix
Immature cells
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What are the different types of cells of connective tissue?
1. Fibroblasts
2. Macrophages
3. Plasma cells
4. Mast cells
5. Adipocytes
6. White blood cells
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Describe fibroblasts.
Large, flat cells with breaching processes.
Present in all connective tissue, usually the most numerous
Secrete fibres and certain components of the ground substance of the extracellular matrix
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Describe macrophages.
Develop from monocytes, a type of white blood cell
| Are capable of engulfing bacteria and cellular debris by phagocytosis
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What is the difference between fixed and wandering macrophages?
Fixed - reside in a particular tissue
| Wandering - have the ability to move throughout the tissue and gather at sites of infection
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Describe plasma cells.
```
Small cells that develop from a type of white blood cell called a B lymphocyte
Secrete antibodies (proteins that attack and neutralized foreign substances)
Important in immune response
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Describe mast cells.
Abundant alongside blood vessels that supply connective tissue
Produce histamine, a chemical that dilates small blood vessels as part of the inflammatory response
Can bind to and ingest and kill bacteria
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Describe adipocytes.
Also called fat cells or adipose cells
Store triglycerides
Found deep to the skin and around organs such as the heart and kidneys
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Describe white blood cells.
In response to certain conditions, they migrate from the blood into connective tissues
Neutrophils gather at sites of infection
Eosinophils gather at sites of parasitic invasions and allergic responses
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What are the two major components of the extracellular matrix?
1. Ground substance
| 2. Fibers
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What is the ground substance?
Component of connective tissue between the cells and fibers
| May be fluid, semi-fluid, gelatinous, or calcified
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What are the functions of ground substance?
- supports cells
- binds cells together
- stores water
- provides a medium for exchange of substances between the blood and cells
- active role in how tissues develop, migrate, proliferate and change shape and how they carry out their metabolic functions
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What are glycosaminoglycans? (GAGs)
The polysaccharides in ground substance: hyaluronic acid, chondroitin sulfate, dermatan sulfate, keratan sulfate
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What is the most important function of GAGs?
They trap water, making the ground substance more jellylike
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What is hyaluronic acid?
A viscous, slippery substance that binds cells together, lubricates joints and helps maintain the shape of the eyeballs
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What is hyaluroinase?
An enzyme that breaks apart hyaluronic acid
Causes the ground substance to become more liquid
Helps white blood cells move through tissue more easily
Helps sperm cells penetrate an oocyte
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What is chondroitin sulfate?
Provides support and adhesiveness in cartilage, bone, skin, and blood vessels
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What contains dermatan sulfate?
Skin, tendons, blood vessels, heart valves
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What contains keratan sulfate?
Bone, cartilage, cornea of the eye
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What is fibronectin?
The main adhesion protein in connective tissue
| Binds to both collagen fibers and ground substance, linking them together
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What are the three types of fibers found in the extracellular matrix?
1. Collagen fibers
2. Elastic fibers
3. Reticular fibers
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What are collagen fibers?
Very strong and resist pulling forces but they are not stiff
Allows tissue flexibility
Found in most types of connective tissues (bone, cartilage, tendons and ligaments)
Consist of collagen
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What are elastic fibers?
Smaller in diameter than collagen fibers
Form a fibrous network within a connective tissue
Are strong but can be stretched up to 150% of their relaxed length without breaking
Found in skin, blood vessel walls, lung tissue
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What are reticular fibers?
Much thinner than collagen fibers and form branching networks
Provide support and strength
Help form the basement membrane
Consist of collagen arranged in fine bundles with a coating of glycoprotein
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What are the two main classifications of connective tissue?
1. Embryonic connective tissue
| 2. Mature connective tissue
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What are the two different kinds of embryonic connective tissue?
A. Mesenchyme - forms almost all other types of connective tissue, under the skin and along developing bone
B. Mucous connective tissue - in the umbilical cord, provides support
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What are the five different kinds of mature connective tissue?
A. Loose connective tissue - loosely packed
B. Dense connective tissue - more densely packed, contain more fibers
C. Cartilage - can endure more stress than loose or dense tissue
D. Bone
E. Liquid connective tissue
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What are the three different kinds of loose connective tissue?
1. Areolar connective tissue - "packing material of the body", strength, elasticity, support
2. Adipose tissue - reduces heat loss, energy reserve, supports and protects organs
3. Reticular connective tissue - forms stroma of organs, binds smooth muscle tissue, filters and removes worn-out blood cells in spleen
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What are the three different kinds of dense connective tissue?
1. Dense regular connective tissue - provides strong attachment between muscle to bone or muscle to muscle, withstands pulling (tension) along the long axis of fibers. Forms tendons
2. Dense irregular connective tissue - provides tensile strength in many directions
3. Elastic connective tissue - allows stretching of various organs, strong and can recoil, lung tissues and arteries
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What are the three different kinds of cartilage?
1. Hyaline cartilage - provides smooth surfaces for movement at joints, flexibility and support. Weakest type of cartilage
2. Fibrocartilage - support and joining structures together, strongest type. Intervertebral discs
3. Elastic cartilage - provides strength and elasticity, epiglottis, external ear, maintains shape of certain structures
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What are the two different kinds of liquid connective tissue?
1. Blood tissue
| 2. Lymph
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What gives cartilage its strength? Its resilience?
Strength is due to collagen fibers
| Resilience is due to chondroitin sulfate
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How does cartilage differ from other connective tissues? How is it similar?
Similar b/c it has few cells and large quantities of extracellular matrix
Differs b/c it does not have nerves or blood vessels in its extracellular matrix
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Why does cartilage not have a blood supply?
It secretes an antiangiogensis factor that prevents blood vessel growth
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Why does a fat person have a higher blood pressure than a lean person?
With weight gain, the amount of adipose tissues increases, and new blood vessels form. Thus an obese person has many more blood vessels than would a lean person, causing blood pressure to rise b/c the heart has to work harder to service those new/extra blood vessels
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What are the cells of mature cartilage called?
Chondrocytes - occur singly or in groups within spaces called lacunae n the extracellular matrix
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What is the name of the covering of dense irregular connective tissue?
Perichondrium - surrounds the surface of most cartilage and contains blood vessels and nerves and is the source of new cartilage cells
CARTILAGE HAS NO BLOOD SUPPLY
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Why is cartilage repair so slow?
B/c it is avascular
Relatively inactive tissue
Substances needed for repair must diffuse or migrate into the cartilage
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What is interstitial growth?
Growth from within
The cartilage increases rapidly in size due to the division of existing chondrocytes and the continuous deposition of increasing amounts of extracellular matrix by the chondrocytes
Occurs during childhood and adolescence
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What is appositional growth?
Growth on the outer surface
Cells in the inner cellular layer of the perichondrium differentiate into chondroblasts. As differentiation continues, the chondroblasts surround themselves with extracellular matrix and become chondrocytes. As a result, matrix accumulates beneath the perichondrium on the outer surface, causing it to growth in width
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What makes up the skeletal system?
Cartilage, joints and bone
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What is bone tissue called?
Osseous tissue
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What are the 4 parts of an osteon?
1. Lamellae - concentric rings, gives bone strength & hardness
2. Lacunae - small spaces that contain osteocytes (mature bone cells)
3. Canaliculi - networks that project from the lacunae, routes for nutrients
4. Central (haversian) canal - contains blood vessels and nerves
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What is blood tissue?
BLOOD!
A connective tissue with a liquid extracellular matrix and formed elements
Extracellular matrix = blood plasma
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What is blood plasma?
A pale yellow fluid that consists mostly of water with a wide variety of dissolved substances:
- nutrients, wastes, enzymes, plasma proteins, hormones, respiratory gases, and ions
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What are formed elements?
Red blood cells, white blood cells, and platelets
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What do red blood cells do?
Transport oxygen to body cells and remove carbon dioxide from them
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What do white blood cells do?
Involved in phagocytosis, immunity, and allergic reactions
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What do platelets do?
Participate in blood clotting
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What is lymph?
The extracellular fluid that flows in lymphatic vessels
A connective tissue
Consists of several types of cells in a clear liquid extracellular matrix that is similar to blood plasma but with less proteins
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What is a membrane?
A flat sheet of pliable tissue that covers or lines a part of the body
Majority of membranes consist of an epithelial layer and an underlying connective tissue layer and are called epithelial membranes
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What are the principle epithelial membranes ?
1. Mucous membranes
2. Serous membranes
3. Cutaneous membranes
* 4. Synovial membrane - lines joints and contains connective tissue but no epithelium
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What is a mucous membrane?
Lines a body cavity that opens directly to the exterior
Consist of a lining layer of epithelium and an underlying layer of connective tissue
Important defence mechanism
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What is the lamina propria?
The connective tissue layer of a mucous membrane is areolar connective tissue
Supports the epithelium, binds it to the underlying structures, allows some flexibility, affords some protection
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What is a serous membrane?
Lines a body cavity that does NOT open directly to the exterior (thoracic or abdominal cavities)
Covers the organs within the cavities
Consist of areolar connective tissue covered by mesothelium
Two layers: parietal layer & visceral layer
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What is the parietal layer?
Layer attached to and lining the cavity wall
| Is a serous membrane
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What is the visceral layer?
Layer that covers and adheres to the organs within the cavity
Serous membrane
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What is the serous fluid?
A watery lubricant that allows organs to glide easily over one another or to slide against the walls of cavities
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What is the pleura?
Serous membrane lining the thoracic cavity and covering the lungs
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What is the pericardium?
Serous membrane lining the heart cavity and covering the heart
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What is the cutaneous membrane?
Skin that covers the entire surface of the body and consists of a superficial portion called the epidermis and a deeper portion called the dermis
142
What are synovial membranes?
Lines the cavities of freely movable joints
Line structures that do not open to the exterior
LACK an epithelium and are therefore NOT epithelial membranes
Composed of a discontinuous layer of cells called synoviocytes
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What does synovial fluid do?
Lubricates and nourishes the cartilage covering the bones at movable joints and contains macrophages that remove microbes and debris from the joint cavity
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What do muscular tissues do?
Produce body movements, maintain posture, generate heat
| Provide protection
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What are the three types of muscular tissue?
1. Skeletal
2. Cardiac
3. Smooth
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What classifies muscle tissue?
Elongated cells that can use ATP to generate force
147
Describe skeletal muscle tissue.
Attached to bones by tendons
Long, cylindrical striated fibers
Multi-nucleated cell with nuclei at periphery
VOLUNTARY!
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Describe cardiac muscle tissue.
Branched striated fibers with usually only one centrally located nucleus
Contain desmosomes and Gap junctions
Located in the heart wall
149
Describe smooth muscle tissue.
Fibers usually involuntary, non-striated, small spindle shaped cell thickest in the middle, tapering to each end
Gap junctions connect many individual fibers
In blood vessels, airways to lungs, stomach intestines, gallbladder, urinary bladder, uterus
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What are the two principle nervous tissues?
Neurons and neuroglia
151
What are neurons?
Nerve cells
Sensitive to various stimuli
Convert stimuli into electrical signals called nerve action potentials
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What are the three basic parts of a neuron?
1. Cell body - nucleus and other organelles
2. Axon - single, thin cylindrical process that may be very long, output portion of the neuron
3. Dendrite - highly branched, tapering, usually short cell processes. Major receiving (input portion of the neuron)
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What are excitable cells?
Neurons and muscle fibers
They exhibit electrical excitability
The ability to respond to certain stimuli
154
What is tissue repair?
The replacement of worn-out, damaged or dead cells
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What are stem cells?
Immature, undifferentiated cells, can divide to replace lost or damaged cells
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What causes a scar to form?
If fibroblasts of the stroma are active in the repair of a damaged tissue, the replacement tissue will be a new connective tissue. The fibroblasts synthesize collagen and other extracellular matrix materials that aggregate to form scar tissue.
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What three factors affect tissue repair?
1. Nutrition
2. Blood circulation
3. Age
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What is wound dehiscence?
The partial or complete separation of the outer layers of a sutured incision
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What is granulation tissue?
New tissues forms across a wound to provide a framework that supports the epithelial cells that migrate into the open area and fill it
