Chapter 4 - Tissue Level Flashcards
What is the science that deals with the study of tissues?
Histology
What is a tissue?
A group of cells that function together to carry out specialized activities
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?
- Epithelial tissue
- Connective tissue
- Muscular tissue
- 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?
- Tight junctions
- Adherens junctions
- Desmosomes
- Hemidesmosomes
- 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?
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
What is an adhesion belt?
Adherens junctions often form an adhesion belt b/c they encircle the cell
What are desmosomes?
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
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?
- 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
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?
- Selective barriers that limit or aid the transfer of substances into and out of the body
- Secretory surfaces that release products produced by the cells onto their free surfaces
- 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
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
What is found between epithelial tissues and connective tissues?
Basement membrane
What is the basement membrane?
A thin extracellular layer that commonly consists of two layers, the basal lamina and reticular lamina
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
What is the reticular lamina?
Closer to the underlying connective tissue
Contains proteins such as collagen called fibroblasts
Do epithelial tissues have a high or low rate of cell division?
High - allows them to constantly renew, and repair themselves
What are the two types of epithelial tissues?
- Covering and lining epithelium
2. Glandular epithelium
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
What are glandular epithelium?
Makes up the secreting portion of glands such as the thyroid, adrenal and sweat glands
What cell shape is best adapted for the rapid movement of substances from one cell to another?
Squamous cells
What two characteristics define epithelial tissues?
- Arrangement of cells into layers, depending on function
2. The shapes of the cells, depending on their function
What are the three different kinds of arrangement of layers of cells?
- Simple
- Pseudostratified
- Stratified
What are the four different kinds of cell shapes?
- Squamous
- Cuboidal
- Columnar
- Transitional
Describe simple epithelium and its functions.
Single layer of cells
Functions in diffusion, osmosis, filtration, secretion, or aborption
What is secretion?
The production and release of substances such as mucus, sweat or enzymes
What is absorption?
The intake of fluids or other substances such as digested food from the intestinal tract
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
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
Describe squamous cells and their function
Thin, which allow for the rapid passage of substances through them
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
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
Describe transitional cells and their function
Can change shape
From squamous to cuboidal and back
Organs such as the urinary bladder stretch
What are the 4 different kinds of simple epithelium?
- Simple squamous
- Simple cuboidal
- Simple columnar
- Pseudostratified columnar
What are the 4 different kinds of stratified epithelium?
- Stratified squamous
- Stratified cuboidal
- Stratified columnar
- Transitional epithelium
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
What are goblet cells?
Are modified columnar epithelial cells that secrete mucus at their apical surfaces
What is keratin?
A tough, fibrous intracellular protein that helps protect skin and underlying tissues from heat, microbes and chemicals
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
What is a gland?
A single cell or group of cells that secrete substances into ducts (tubes), onto a surface or into the blood
How are glands classified?
As either endocrine or exocrine
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
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
How are exocrine glands classified structurally?
Unicellular or multicellular
What are unicellular glands?
Single celled glands
Goblet cells
What are multicellular glands?
Composed of many cells that form a distinctive microscopic or macroscopic organ (sweat, oil or salivary glands)