Flashcards in Chapter 4 - Tissue Level Deck (160)
What is a tissue?
A group of cells that function together to carry out specialized activities
What is the science that deals with the study of tissues?
What is a pathologist?
A physician who specializes in laboratory studies of cells and tissues to help other physicians make accurate diagnoses
What are the 4 different kinds of tissues?
1. Epithelial tissue
2. Connective tissue
3. Muscular tissue
4. Nervous tissue
Describe epithelial cells.
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
Describe connective tissue.
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
Describe muscle tissue.
Composed of cells specialized for contraction and generation of force
Generates heat that warms the body
Describe nervous tissue.
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
What is a biopsy?
The removal of a sample of living tissue for microscopic examination
What are cell junctions?
Contact points between the plasma membranes of tissue cells
What are the 5 different types of cell junctions?
1. Tight junctions
2. Adherens junctions
5. Gap junctions
Which type of cell junction functions in communication between adjacent cells?
Gap junctions allow cellular communications via passage of electrical and chemical signals between adjacent cells
What are tight junctions?
Consist of weblike strands of transmembrane proteins that fuse together the outer surfaces of adjacent plasma membranes to seal off passageways between adjacent cells
Where do tight junctions mainly occur?
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
What are adherens junctions?
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
What is an adhesion belt?
Adherens junctions often form an adhesion belt b/c they encircle the cell
What are desmosomes?
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
Where are desmosome junctions common?
Among the cells the make up the epidermis and among cardiac cells of the heart
What are hemidesmosome junctions?
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
What are gap junctions?
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
What is the function of connexons in gap junctions?
Ions and small molecules can diffuse from the cytosol of one cell to another
What are some special functions of gap junctions?
Allow cells in a tissue to communicate
Enable nerve and muscle impulses to spread rapidly among cells
What the main differences between epithelial tissue and connective tissue?
1. 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
2. Epithelial tissue has no blood vessels. Connective tissue has a significant network of blood vessels.
3. 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
What does epithelial tissue consist of?
Cells arranged in continuous sheets, in either single or multiple layers
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
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
What is the lateral surface?
Face adjacent cells on either side
May contain tight junctions, adherens junctions, desmosomes and/or gap junctions
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
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