Epithelia, Cell Division and Polarity

Question 1

What are the three types of epithelial tissue and what do they cover?

Answer 1

-Mesothelium - lines organs, body cavities, blood vessels and ducts
-endothelium - lines inner surface lining of blood and lymphatic vessels
-glandular epithelium - forms glands

Question 2

What are the general features if epithelial tissue?

Answer 2

-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

Question 3

Give some features of the epithelial tissue structure and their functions

Answer 3

-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

Question 4

Give the general features of epithelial cells

Answer 4

-avascular
-supplied by nerves
-they have a high capacity for renewal

Question 5

What epithelial tissues are an exception for the general feature of a high capacity for renewal?

Answer 5

Corneal endothelium and retinal pigment epithelium

Question 6

What are the 6 types of epithelial tissue?

Answer 6

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

Question 7

Give examples of simple squamous cells and give the functions

Answer 7

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

Question 8

Give examples and the functions of simple cuboidal

Answer 8

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

Question 9

Give examples and the functions of simple columnar

Answer 9

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

Question 10

Give examples and the functions of pseudostratified

Answer 10

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

Question 11

Give examples and the functions of stratified squamous

Answer 11

Examples: epidermis (most keratin), linings of the mouth, oesophagus and vagina (medium keratin), corneal epithelium and tounge epithelium (non - keratinised)

Function: protection

Question 12

Give examples and the functions of stratified columnar

Answer 12

Examples: parts of urethra, large excretory ducts of some glands, gland in oesophaghs, makes up the conjunctiva

Function: protection, secretion

Question 13

Give examples and the functions of stratified cuboidal

Answer 13

Examples: ducts of sweat glands, glands in oesophagus, male urethra
Function: protection, sometimes secretion or absorption

Question 14

Give examples and the functions of stratified transitional

Answer 14

Examples: the transitional epithelium of the urinary passages urothelium, lining of urinary bladder and portions of urethra and ureters

Function: permits distension

Question 15

What are the types of glandular epithelium

Answer 15

• Endocrine glands: they produce hormones and secretes them into the blood
• exocrine glands: secrete sweat, oil, earwax, saliva and digestive enzymes into ducts

Question 16

What is cell adhesion for?

Answer 16

-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

Question 17

What are the 5 types of cell junctions

Answer 17

Tight junctions
Adherents junctions
Desmosomes
Gap junctions
Hemidesmosomes

Question 18

What two proteins span through the extra cellular space in tight junctions?

Answer 18

Claudins and occludins

Question 19

What proteins are bound on the inner cystosolic side of the cells in tight junctions and what is bound to those proteins

Answer 19

Zona occludins, actin filaments

Question 20

What do tight junctions do?

Answer 20

They act as a diffusion barrier and block the transport of ions and different types of molecules between the cells

Question 21

What surface do tight junctions connect the cells?

Answer 21

At the apical surface

Question 22

Where are you likely to find tight junctions?

Answer 22

-blood brain barrier and blood retina barrier
-gastrointestinal tract

Question 23

What proteins span across adherence junctions and what molecule is between the proteins?

Answer 23

E - Cadherins which bind with each other via the calcium ion hence cadherins are calcium dependant proteins

Question 24

Which proteins is on the inner cytosolic side of a cell in adherens junctions? Give it in order going in to out

Answer 24

Vinculin, catenin, actin filaments

Question 25

What is the function of adherence junctions?

Answer 25

They withstand shearing and abrasive forces to allow for stretch

Question 26

What surface of cells do adherence junctions connect to in comparison to tight junctions

Answer 26

They’re are more basal than the tight junctions

Question 27

Give examples where adherence junctions are found

Answer 27

-urinary tract
-respiratory tract
-blood vessels
-the skin

Question 28

What are desmosomes made out of

Answer 28

Cadherins being desmoglein and desmocolin with calcium between them, Desmoplakin bound to the cytosolic part of the membrane and then intermediate filaments on the most cytosolic side that contain keratin

Question 29

What are desmosomes for?

Answer 29

High tensile stress

Question 30

Give examples where you might find desmosomes

Answer 30

Cardiac tissue- cells are held by intercollated disks which consist of the desmosomes and gap junctions
Skin- to bind the epidermal cells to each other

Question 31

What are hemidesmosomes?

Answer 31

They are the connection of the cell to the basal lamina

Question 32

What does the basal lamina consist of?

Answer 32

Fibronectin, laminin and collagen

Question 33

What is the protein that spans through the cell and connects it to the basal lamina?

Answer 33

The integrin and this has intermediate filaments mainly made of keratin attached to it

Question 34

What do hemidesmosomes do?

Answer 34

They form the basement membrane via the connection between the basal lamina and the epithelium above it

Question 35

Where are hemidesmosomes found? Give an example

Answer 35

In epithelial tissue for example the skin

Question 36

What’s a good video to watch on cell junctions?

Answer 36

YouTube, cell junctions by ninja nerds

Question 37

What proteins make up gap junctions?

Answer 37

2 Connexons. Each connexon is made up of 6 connincs

Question 38

What do gap junctions do?

Answer 38

Allow for cell-cell communications by allowing for ion transfer such as Na+ and Ca2+ as well as transfer molecules such as cAMP- useful in cells that get excited

Question 39

Where are gap junctions most useful in?

Answer 39

Cardiac tissue’s intercollated disks
Smooth muscle tissue such as the GIT
Neurons

Question 40

Which intercellular junctions provide cells with ability to transfer small signalling molecules from one cell to another?

Answer 40

gap junctions

Question 41

which intercellular junctions are the closest to the apical surface of epithelial cells?

Answer 41

occluding junctions

Question 42

which of the following proteins serve as transmembrane linker proteins in adhering junctions?

Answer 42

cadherins and integrins

Question 43

in which adhering intercellular junctions are the intermediate filaments of the cytoskeleton linked with the transmembrane linker protein via the intracellular attachment proteins?

Answer 43

spot desmosomes

Question 44

give 4 things that happen as a result of depletion of extracellular calcium

Answer 44

-intercellular binding through zonula adherens and macula adherens is broken
-calcium dissociates from cadherins molecules
-binding between cadherin dimers is disrupted
-intercellular binding via belt desmosomes is disrupted

Question 45

which intercellular junctions are responsible for providing blood-retina barrier?

Answer 45

zonula occludens

Question 46

how many helical subunits does a connexin have?

Answer 46

4