Week 3- Epithelial Cells and Tissues

Question 1

Describe the structure of simple squamous epithelial cells and where they could be found

Answer 1

Single layer of flattened cells, found on alveoli and endothelium (lining major blood vessels). Thin, allows exchange to occur

Question 2

Describe the structure of simple cuboidal epithelial cells and where they could be found

Answer 2

Single layer of cube shaped cells, mainly found on duct linings eg kidney collecting ducts

Question 3

Describe the structure of simple columnar epithelial cells and where they could be found

Answer 3

Single layer of column shaped cells, found in absorbative surfaces eg enterocytes or gut

Question 4

Describe the structure of stratified squamous epithelial cells and where they could be found

Answer 4

Multiple layers of flattened cells, there are 2 types:

1. Keratinising- die and turn into keratin for support eg epidermis of skin
2. Non keratinisng- eg vagina and mouth

Question 5

Describe the structure of pseudo stratified epithelial cells and where they could be found

Answer 5

Looks like there are multiple layers but one is in contact with basal lamina eg airways, urinary/reproductive tracts

Question 6

What are the 4 different types of junctions in epithelia and their functions?

Answer 6

Tight junction- seals gaps between cells
Adherans junctions- organizes formation of all other junctions
Desmosomes- for structural support (helps protect against stress and shocks)
Gap junctions- channels allow communication, exchange etc

Question 7

What is an apical domain?

Answer 7

The luminal/open surface

Question 8

What is a basolateral domain?

Answer 8

Opposite to the apical domain, in contact with the extra cellular matrix

Question 9

What is a lateral membrane?

Answer 9

The membrane between 2 adjacent cells

Question 10

How does polarity work in epithelial cells and why is it important?

Answer 10

Polarity is different regions of the cell being discreetly different to each other. This is required as most epithelial cells have directional functions eg secretion, fluid transport etc

Question 11

Describe the structure of transporting epithelia and how this helps the cells function

Answer 11

Infoldings on basal membrane to increase surface area
Large no of ion transporters in the membrane (only on basal surface to ensure directionality)
Large no of mitochondria near infoldings to supply ATP for active transport

Question 12

Describe the structure of absorbative epithelia and how this helps the cells function

Answer 12

Often folded to increase surface are eg small intestine

Large no of active transporters

Question 13

Describe the structure of secretory epithelia and how this helps the cells function

Answer 13

Have distinctly arranged organelles eg endocrine and exocrine cells of pancreas (endocrine secrete onto basal aspect)
Often arranged in tubules and glands
Can be classed into constitutive (secretory vesicles fuse directly with the membrane and release contents) and stimulated (vesicles are stored in the cytoplasm and secrete contents only when stimulated)

Question 14

What are the 2 types of secretory epithelia

Answer 14

Constitutive and secretory

Question 15

How are epithelial cells replaced?

Answer 15

Via proliferation from stem cells

Question 16

Describe epithelial cell turnover in the small intestine

Answer 16

New cells come from crypts on the surface of villi, chemotherapy can stop them being able to replace cells causing gastrointestinal problems etc

Question 17

Describe epithelial cell turnover in the epidermis

Answer 17

Cells come the basal layer and as they migrate upwards they flatten and keratinise. Constant pressure can cause hyper proliferation (too many cells) creating warts and corns etc