Chapter 4: Tissues Flashcards
Where are epithelial tissues located?
Covers body surfaces
Lines body cavities
Hollow organs and ducts
Forms glands
What does connective tissue do?
This protects and supports the body and its organs
Binds organs together
Stores energy reserves as fat
Provides immunity
What does muscular tissue do?
This generates physical force needed to make body structures move
What does nervous tissue do?
This detects changes inside and outside the body and initiates and transmits nerve impulses that coordinate body activities to help maintain homeostasis
What are cell junctions?
These are the points of contact between most epithelial cells and some muscle and nerve cells, tightly joining them into functional units
What are the two main types of epithelial tissue?
Surface epithelium (aka covering and lining epithelium)
Glandular epithelium
Where is surface epithelium located?
Outer covering of the skin and some internal organs
Lines body cavities, blood vessels, ducts, and interiors of the respiratory, digestive, urinary, and reproductive systems
Makes up parts of the organs for hearing, vision, and touch.
Where is glandular epithelium located?
Makes up secreting portion of glands like sweat, thyroid, adrenal, and digestive glands
What are the general features of epithelium?
Mostly or entirely made up of closely packed cells with little extracellular material between them
Arranged in continuous sheets
Have an apical (free) surface, lateral surface, and basal surface
Avascular
Has a nerve supply
High capacity for renewal by cell division
What is the apical surface of epithelium?
This is the surface exposed to a body cavity, lining of an internal organ, or the exterior of the body.
For epithelia with multiple layers, this is the most superficial layer
What is the lateral surface of epithelium?
This is the surface that faces adjacent cells
What is the basal surface of epithelium?
This is the surface that attaches to a basement membrane. For epithelia with multiple layers, this is the deepest layer
What is a basement membrane?
This is a thin extracellular structure made mostly of protein fibers. It acts as an anchor between epithelial tissue and its underlying connective tissue
How are basement membranes affected in diabetes mellitus?
In untreated cases, basement membranes of capillaries can thicken especially in the eyes and kidneys, leading to blindness and kidney failure
What are the 3 different arrangements of epithelial cells layers?
Simple
Pseudostratified
Stratified
What are simple epithelium layers, and what are they for?
These are a single layer of cells
They are for diffusion & osmosis, filtration, secretion, and absorption
What are pseudostratified epithelium, and what are they for?
These appear to have multiple layers because the cell nuclei lie at different levels, and not all cells reach the apical surface. These are actually a type of simple epithelium since all of the cells rest on the basement membrane.
Cells that reach the apical surface may contain cilia and others can secrete mucous
Which pseudostratified epithelium secretes mucous?
Goblet cells
What are stratified epithelium, and what is it for?
This is a type of epithelium that is made up of two or more layers of cells.
It protects underlying tissues in locations with wear and tear
What are the 4 cell shapes of epithelia?
Squamous cells
Cuboidal cells
Columnar cells
Transitional cells
What are squamous cells and what are they for?
These are thin epithelial cells and allow for rapid passage of substances through them
What are cuboidal cells and what are they for?
These are equivalently tall and wide epithelial cells shaped like cubes or hexagons. They may have microvilli at their apical surface and function in either secretion or absorption
What are columnar cells and what are they for?
These are tall epithelial cells like columns that protect underlying tissues. Their apical surfaces may have cilia or microvilli, and usually specialize in secretion and absorption
What are transitional cells and what are they for?
These change shape from flat to cuboidal and back in organs that stretch to a larger size and then collapse to a smaller size like in the urinary bladder
Describe the appearance of simple squamous epithelium
Single layer of flat cells resembling a tiled floor when looking from the apical view
Centrally located oval- or spherically-shaped flattened nucleus
Where are simple squamous epithelia located?
Lines:
Heart
Blood vessels
Lymphatic vessels
Air sacs of lungs
Glomerular (Bowman’s) capsule of kidneys
Inner surface of the tympanic membrane Peritoneum
Describe the function of simple squamous epithelium
Filtration
Diffusion
Osmosis
Secretion in serous membranes
Endothelium is an example of what type of tissue, and where is it located?
This is a type of simple squamous epithelium that lines the heart, blood vessels, and lymphatic vessels
Mesothelium is an example of what type of tissue, and where is it located?
This is a type of simple squamous epithelium that lines serous membranes like the peritoneum, pleura, or pericardium
Describe the appearance of simple cuboidal epithelium
Single layer of cube-shaped cells. Easily recognized from the side view
Round, centrally located nucleus.
Where are simple cuboidal epithelia located?
Lines kidney tubules and smaller ducts of many glands
Makes up the secreting portion of the thyroid gland
Covers surface of ovary
Lines anterior surface of the eye lens capsule, and forms the pigmented epithelium at the posterior surface of the eye.
Describe the function of simple cuboidal epithelium
Secretion and absorption
Describe the appearance of non-ciliated simple columnar epithelium
Single layer of non-ciliated columnar cells with nuclei near bases of cells
Includes cells with microvilli and goblet cells.
Describe microvilli
They are microscopic fingerlike projections which increase the surface area of the plasma membrane, increasing the rate of absorption by the cell
Describe goblet cells
They are modified columnar cells that secrete mucus at their apical surfaces. Before release, mucus accumulates in upper portion of cell, causing it to bulge and making the whole cell resemble a goblet or wine glass.
Where are non-ciliated simple columnar epithelia located?
They line most of the GIT (from stomach to anus), ducts of many glands, and gallbladder
Describe the function of non-ciliated simple columnar epithelia
These are for secretion and absorption. Secretion of mucous lines the digestive, respiratory, and reproductive tracts completely, and most of the urinary tract.
The appearance of ciliated simple columnar epithelia
Single layer of ciliated column‐like cells with nuclei near bases
Includes goblet cells in some locations.
Where are ciliated simple columnar epithelia located?
Lines some portions of the upper respiratory tract, uterine (fallopian) tubes, uterus, some paranasal sinuses, and central canal of spinal cord
Describe the function of ciliated simple columnar epithelia
Mucus secreted by goblet cells forms a film over respiratory surface that traps inhaled foreign particles.
Cilia wave in unison to move mucus and foreign particles toward throat to be coughed up and swallowed/spit out Cilia also help move oocytes expelled by the ovaries through uterine tubes into uterus
Describe the appearance of non-ciliated pseudostratified columnar epithelia
Looks like several layers because the nuclei of the cells are at various levels.
All cells are attached to the basement membrane in a single layer but some cells do not extend to the apical surface. When viewed from the side, these features give the false impression of a multilayered tissue.
Includes cells without cilia and also lacks goblet cells.
Where are non-ciliated pseudostratified columnar epithelia found?
Lines epididymis, larger ducts of many glands like the parotid, and parts of male urethra.
What are non-ciliated pseudostratified columnar epithelia for?
Absorption and secretion
Describe the appearance of ciliated pseudostratified columnar epithelia
Looks like several layers because the nuclei of the cells are at various levels.
All the cells are attached to the basement membrane in a single layer but some do not extend to the apical surface. When viewed from the side, these features give the false impression of a multilayered tissue
Contains cells that extend to the surface and either contain cilia or secrete mucus (goblet cells).
Where are ciliated pseudostratified columnar epithelia located?
Lining of most of the upper respiratory tract
What are stratified columnar epithelia for
Secretes mucus that traps foreign particles, and the cilia sweep away the mucus for eventual elimination from the body.
Describe the appearance of stratified squamous epithelia
Two or more layers of cells
Upper cells are squamous while those in the deep layers vary in shape from cuboidal to columnar.
Basal cells continually undergo cell division. As new cells grow, cells of basal layer are pushed upward toward surface and become dehydrated, shrunken, and harder because they are farther from the blood supply in the underlying connective tissue.
At apical layer, cells lose their cell junctions and are sloughed off, but are replaced as new cells continually emerge from basal cells
What are the two types of stratified squamous epithelium
Keratinized and non-keratinized
What is keratinized stratified squamous epithelium?
This is stratified squamous epithelium that has a tough layer of keratin in apical layer and several layers deep to it to help protect the skin and underlying tissues from microbes, heat, and chemicals
What is non-keratinized stratified squamous epithelium?
Nonkeratinized stratified squamous epithelium does not contain keratin in the apical layer or several layers deep and remains moist.
Where is keratinized stratified squamous epithelium found?
Superficial layers of the skin
Where is non-keratinized stratified squamous epithelium found?
Lines wet surfaces such as the mouth, esophagus, part of the epiglottis, part of the pharynx, vagina, and the tongue
What is the function of stratified squamous epithelia?
Protection - it is the first line of defense against microbes
Describe the appearance of stratified cuboidal epithelia
Two or more layers of cells, with the apical layer being cube‐shaped; fairly rare type.