Epithelia, Cell Division and Polarity Flashcards
What are the three types of epithelial tissue and what do they cover?
-Mesothelium - lines organs, body cavities, blood vessels and ducts
-endothelium - lines inner surface lining of blood and lymphatic vessels
-glandular epithelium - forms glands
What are the general features if epithelial tissue?
-closely packed cells with very little extra cellular matrix
-continuous sheets
-have different surfaces : apical surface, lateral surface facing adjacent cells, basal surface attached to the basal lamina
Give some features of the epithelial tissue structure and their functions
-they have cytoskeleton linked anchoring junctions, these bind epithelial cells tones higher and to the basal lamina
-gap junctions allow molecules to pass from cell to cell
-its polarised hence leak proof to create tight junctions. This allows the epithelial to form barriers to separate biological compartments and so regulate homeostasis by controlling the ion and solute transport
Give the general features of epithelial cells
-avascular
-supplied by nerves
-they have a high capacity for renewal
What epithelial tissues are an exception for the general feature of a high capacity for renewal?
Corneal endothelium and retinal pigment epithelium
What are the 6 types of epithelial tissue?
Simple:
-squamous
-cuboidal
-columnar
Stratified
-squamous
-cuboidal
-pseudo(stratified)
-columnar
Transitional: multiple layers of epithelial cells which look cuboidal when they contact and squamous when they expand
Give examples of simple squamous cells and give the functions
Examples: linings of the peritoneal, pleural and pericardial cavities, glomerulus of the kidney, alveoli of lungs and lymphatic vessels
Functions: filtration, diffusion, osmosis and secretion
Give examples and the functions of simple cuboidal
Examples: anterior surface of the crystalline lens, retinal pigment epithelium, surface of ovary, lining of kidney tubes, lining of smaller ducts of many glands such as thyroid
Function: secretion and absorption
Give examples and the functions of simple columnar
Examples: there’s
non ciliated = lining of the gastrointestinal tract, lining of ducts of many gland
ciliated = lining of upper respiratory tract, uterine tubes and uterus
Function: secretion, absorption and moving substances
Give examples and the functions of pseudostratified
Examples: the ciliated epithelium of the trachea of the upper respiratory tract, larger ducts of glands such as the pseudostratified columnar epithelium in the stereocilia of the epididymis
Functions: ciliated= secretion and movement of mucus, non ciliated= absorption and protection
Give examples and the functions of stratified squamous
Examples: epidermis (most keratin), linings of the mouth, oesophagus and vagina (medium keratin), corneal epithelium and tounge epithelium (non - keratinised)
Function: protection
Give examples and the functions of stratified columnar
Examples: parts of urethra, large excretory ducts of some glands, gland in oesophaghs, makes up the conjunctiva
Function: protection, secretion
Give examples and the functions of stratified cuboidal
Examples: ducts of sweat glands, glands in oesophagus, male urethra
Function: protection, sometimes secretion or absorption
Give examples and the functions of stratified transitional
Examples: the transitional epithelium of the urinary passages urothelium, lining of urinary bladder and portions of urethra and ureters
Function: permits distension
What are the types of glandular epithelium
- Endocrine glands: they produce hormones and secretes them into the blood
- exocrine glands: secrete sweat, oil, earwax, saliva and digestive enzymes into ducts
What is cell adhesion for?
-to organise cells into tissues to allow them to be held by cell-cell and cell-extra cellular matrix adhesions
-to spread mechanical stress across a tissue
-to allow for the cell division of mammalian cells
What are the 5 types of cell junctions
Tight junctions
Adherents junctions
Desmosomes
Gap junctions
Hemidesmosomes
What two proteins span through the extra cellular space in tight junctions?
Claudins and occludins
What proteins are bound on the inner cystosolic side of the cells in tight junctions and what is bound to those proteins
Zona occludins, actin filaments
What do tight junctions do?
They act as a diffusion barrier and block the transport of ions and different types of molecules between the cells
What surface do tight junctions connect the cells?
At the apical surface
Where are you likely to find tight junctions?
-blood brain barrier and blood retina barrier
-gastrointestinal tract
What proteins span across adherence junctions and what molecule is between the proteins?
E - Cadherins which bind with each other via the calcium ion hence cadherins are calcium dependant proteins
Which proteins is on the inner cytosolic side of a cell in adherens junctions? Give it in order going in to out
Vinculin, catenin, actin filaments
