Epithelium Flashcards
What are tissues?
A group of closely associated cells that perform related functions and are similar in structure.
-Between cells: non living extracellular material
What are the 4 basic types of tissue?
- epithelium -covering
- connective tissue- support
- muscle tissue - movement
- nervous tissue - control
What is epithelium?
Sheet of cells that covers a body surface or lines a body cavity; also form most of the body’s glands
What are the roles and functions of epithelia?
Roles: as interfaces and as boundaries
Functions:
- protection
- sensory reception
- secretion
- absorption
- ion transport
- filtration
- formation of slippery surfaces for movement.
What are the special characteristics of epithelia?
- cellularity
- specialized contacts cell junctions
- polarity
- free upper (apical) surface
- Lower (basal) surface contributing basal lamina to basement membrane
-support by connective tissue
- Avascular but innervates
- without vessels
- with nerve endings
-regeneration
How can epithelia be classified according to shape?
Squamous- wider than tall (flattened appearance)
Cuboidal- as tall as wide
Columnar- taller than wide
How can epithelia be classified according to thickness?
Simple- one cell layer
Stratified- more than one layer of cells (which are named according to the shape of the cells in the apical layer)
Which epithelial cell classification is important for diffusion?
Squamous
Which epithelial classification is important for secretion and absorption ? Why ?
Cuboidal and columnar
Larger cells because of machinery of production, packaging, and energy requirements
What are the 6 type of epithelial tissue?
- simple squamous epithelium
- simple cuboidal epithelium
- simple columnar epithelium
- pseudostratified epithelium
- stratified squamous epithelium
- transitional epithelium
Where would simple squamous epithelium be located?
Simple squamous epithelium may be located at sites of rapid diffusion, such as:
- lining of the lung alveoli
- lining of blood vessels
- in the lining of major body cavities
What is endothelium?
A simple squamous epithelium that lines the interior of the circulatory vessels and the heart
What is the mesothelium?
Simple squamous epithelium that lines the peritoneal, pleural and pericardial cavities and covers the viscera
Which body parts require for simple cuboidal epithelium?
Ducts of glands
- small ducts - simple cuboidal epithelium
- large ducts - stratified cuboid
- N.B. deeper cells may also be cuboidal
Pigmented layer of retina
Surface of Ovary
Follicular cells of thyroid
Which body parts use simple columnar epithelium?
Some usual locations
- gall bladder
- epithelium of digestive system
- epithelium of uterus
- uterine glands
What is pseudostratified epithelium?
Appears stratified, typically with nuclei located in at least two more-or-less distinct levels. But in fact every cell rests on the basement membrane, so the epithelium is technically “simple”, in spite of appearances