Tissues Flashcards
Functions of Epithelium tissue
Filtration
Absorption
Protection
Secretion
Special characteristics of Epithelium
- they have no blood supply of their own. Depend on diffusion of capillaries in underlying connective tissue for food and oxygen.
- regenerate themselves
- cells fit closely together to form sheets
- always have one unattached surface or edge. Apical surface is exposed to body’s exterior or the vacating of an internal organ.
- lower surface rests on a basement membrane
Tissues
Groups of cells that are similar in structure and function.
There are 4 primary tissue types.
What are the 4 primary tissue types?
Epithelium (covering)
Connective (support)
Muscle (movement)
Nervous (control)
Classifications of Epithelium
Simple Stratified Squamous Cuboidal Columnar
What is simple epithelium?
Absorption. Secretion, and filtration.
Very thin. NOT good at protection
- single layer of cells
- squamous or flat
- cuboidal or square
- columnar or rectangular
- pseudostratified columnar
Squamous simple epithelium
Single layer of thin squamous cells resting on a basement membrane. Fit closely together (floor tiles) and usually form membranes where filtration or exchange of substances by rapid diffusion occurs (air sacs of the lungs).
Also forms the serous membranes (the slick membranes that line the ventral body cavity and cover organs in that cavity)
Cuboidal or square simple epithelium
One layer of cuboidal cells resting on a basement membrane. Common in glands and their ducts (salivary gland, pancreas) and forms walls of the kidney tubules and covers the surface of the ovaries.
What is a basement membrane?
A structure less material secreted by the cells
Columnar or rectangular simple epithelium
Made of single layer of tall cells that fit closely together.
Goblet cells (produce lubricating mucus) often seen in this type of epithelium.
Lines the entire length of the digestive tract from stomach to anus.
What are mucosae or mucus membranes?
Epithelium membranes that line body cavities open to the body exterior
Pseudostratified Columnar simple Epithelium
All of the cells rest on a basement membrane but some are shorter than others and their nuclei appear at different heights above the basement membrane. As a result, this epithelium gives a false impression that it is stratified.
Mainly functions in absorption and secretion like simple columnar epithelium.
A ciliated variety lines most of the respiratory tract. The mucus produced by goblet cells in the epithelium traps dust and debris and the cilia propel the mucus upward and away from the lungs.
Stratified epithelium
- forms 2 or more layers
- more durable than the simple epithelia
- primarily to protect
- squamous or flat
Most common epithelium in the body. Consists of several layers.
Stratified Squamous epithelium
Stratified epithelium cells consist of many layers of cells. The cells at the free edge are the squamous cells.
Stratified squamous epithelium cells are found in sites that receive a good deal of abuse or friction such as the esophagus, mouth, and outer portion of the skin.
Stratified Cuboidal Epithelium
Usually has just 2 cell layers with the surface being cuboidal (square) in shape.
Found mainly in the ducts of large glands
Fairly rare in the body
Stratified Columnar Epithelium
The surface cells of stratified columnar epithelium are columnar cells but it’s basal cells vary in size and shape.
Fairly rare in the body, being found mainly in the ducts of large glands.
Psuedostratified Columnar or Transitional Epithelium
Highly modified, stratified squamous epithelium that forms the lining of only a few organ (urinary bladder, ureters, part of urethra -all part of urinary system and subject to stretching).
When the organ is distended with urine, the epithelium thins and cells flatten and become squamous like to allow more urine to be stored.
Epithelium tissue
The lining, covering, and glandular tissue of the body.
One type forms the outer layer of the skin, others dip into the body to line it’s cavities
Forms the boundaries that separate us from the outside world