Epithelial Flashcards
What are epithelia?
Cells that line/cover all the body surfaces, tubes and cavities
What connects epithelial cells together?
Tight junctions
What separates the epithelium from the underlying tissues?
Basement membrane
What 2 layers form the basement membrane?
Basil lamena, connective tissue (collagen and other protein fibres)
Why do epithelia have to undergo rapid division?
Cells are continually lost from the surface so new cells are needed to replace them
What are tumours that develop from epithelia called?
Carcinomas
Name the 3 types of epithelia
- Columnar
- Cuboidal
- Squamous
2 types of classification by no. Of layers of cells-
- Simple
2. Stratified
What type of epithelia is found where diffusion, absorption or secretion takes place (simple or stratified)
Simple
Where is stratified epithelia found?
Where there is a need for protection
Eg skin, lining urethra, respiratory tract
Where do u find transitional epithelia?
Bladder
Where do u find stratified cuboidal?
Reproductive system eg lining urethra
What type of epithelia found in blood vessels and why?
Simple squamous- short diffusion pathway for exchange of chemicals
What are the basal cells in stratified epithelia?
Cells in contact with basal lamena
Cells in contact with lumen in stratified epithelia
Apical
What type of epithelia is found in skin
Stratified squamous
Why simple squamous good for exchange?
Pores between cells allow easy passage of molecules
Why cuboidal/ columnar good for transport through?
Tight junctions limit movement between cells so not good for exchange. But these cells have more organelles eg ribosomes and rer to produce transport proteins and mitochondria for atp for at.
Cilia vs microvilli
Cilia have wave like movements which allow them to move substances along whereas microvilli don’t move, they just increase SA of cell membrane
5 functions of epithelia
Protective, secretory, ciliated, transport, exchange
What does the mesothelium line?
Pleura, pericardium and peritoneum. Has a secretory role- secretes a watery fluid that lubricates and prevents walls stickjnv
Role of epithelia in small intestine and what type
Simple columnar
Increase SA for absorption (microvilli on apical surface and basal invaginations)
Mucus secretion to lubricate gut contents- goblet cells
How to increase SA of small intestine
Large folds of wall, villi, microvilli
What type of cells secrete mucus into linen of small intestine ?
Goblet
Where do u find pseudo stratified epithelia?
Respiratory system eg bronchus
Describe pseudo stratified
All cells attached to basement membrane but different sizes and shapes so looks stratified (multiple rows of nuclei)
What type of epithelia in oesophagus?
Stratified squamous
Term for cells that are worn off and shed from the surface of epithelia
Desquamation
Name where u find stratified squamous keratinised epithelium
Skin
Advantage of keratinised epithelium in skin
Prevents water loss- survival in dry environments
What does a melanocyte do?
Give pigment to skin
What is a tight junction?
Point of adherence between epithelial cells
Name the 2 domains formed when epithelial cells join together by tight junctions
Apical membrane, baso-lateral membrane (and then the basal membrane=between and BM)
What are hemidesmosomes involved in?
Allow string attachment of epithelial cells to basal lamena
Function of desmosome
Hold cells together
What is paraceular movement?
Movement across tight junctions
Major tight junction proteins
Claudins, occludins
3 roles of tight junctions
Barrier, fence, gate
Explain how tight junctions work as barriers
They prevent some molecules moving from one compartment to another eg in bladder
Explain how tight junctions work as gates
They function as selective gates ie only open for some molecules/ ions eg let Na+ and H2O through but don’t let Cl- through
Explain how tight junctions function as gates
Once 2 domains are formed there can be different transport proteins on each of the 2 surfaces (apical and bask-lateral) is cell can take up a specific nutrient but not secrete it and vice versa
