7 - Epithelia Flashcards
Two broad types of epithelia (divided by function)
1) Surface epithelia (line surfaces and lumena)
2) Glandular epithelia (involved in secretion)
How are glandular epithelia formed?
Invaginations of secreting cells
Epithelial cell functions 1) 2) 3) 4) 5)
1) Protection
2) Barrier, selective diffusion
3) Absorption
4) Secretion
5) Receptors e.g. smell, taste
Characteristics of epithelial cells 1) 2) 3) 4)
1) Exhibit polarity: apical, lateral and basal domains 2) Connected by cell junctions 3) Supported by a basement membrane 4) Avascular
Examples of simple squamous epithelium
Mesothelium, endothelium, lining of alveoli, glomeruli
Examples of simple cuboidal epithelium
Thyroid follicles, renal tubules
Examples of simple columnar epithelium
1) Non-ciliated e.g. stomach, small and large intestines,
gallbladder and bile ducts, endocervix
2) Ciliated: Fallopian tubes, bronchioles
Difference between stratified and simple epithelia
Simple epithelial cells all have contact with basement membrane.
Stratified epithelial cell basal layer only has contact with basement membrane
What are pseudostratified epithelial cells?
Epithelial cells that have nuclei in different places, and can appear stratified, but all all cells have contact with basement membrane
Examples of pseudostratified columnar epithelial cells
Respiratory tract (ciliated)
Examples of stratified squamous epithelial cells
Keratinising: skin
Non-keratinising: Oral cavity, oesophagus, anal cavity, vagina
Example of stratified epithelium where one cell type lies over a different cell type
Breast, sweat glands, salivary glands: Surface columnar layer overlying myoepithelial layer
Where does surface epithelium get nutrients?
From diffusion of blood vessels underlying basement membrane. Epithelial layers are avascular
Brush border
When there are lots of microvili on an epithelial layer.
Length of microvili
0.5 - 1μm in length
How much can microvili increase surface area by?
A factor of 20
Length of cilia
2 - 10 μm long
Can cilia move?
Yes. Have a core of microtubules