Tissues 2 (Epithelial Tissues)

Question 1

What are the 5 types of epithelial cells with examples?

Answer 1

• simple squamous (endothelial, lung alveolar, mesothelium)
• stratified squamous (keratinising - epidermis, non-keratinising - linings of mouth, anus, cervix, vagina)
• simple cuboidal (lines kidney duct)
• pseudo-stratified cuboidal (lines upper airway - bronchi)
• simple columnar (enterocytes)

Question 2

What is key to epithelial polarity?

Answer 2

• membrane polarity

- tight junctions

Question 3

What are the 2 biochemically and functionally distinct domains in epithelial cells?

Answer 3

• apical (luminal surface)

- basolateral (in contact with ECM)

Question 4

Is secretion, transport and absorption uni- or multi-directional?

Answer 4

unidirectional

Question 5

What are the features of epithelial transport?

Answer 5

• plasma membranes have high ion transporter concentration
• mitochondria closely associated with basal membrane infoldings
• infoldings increase amount of membrane available to pump ions and water

Question 6

What are the features of epithelial absorption?

Answer 6

• secretory cells interspersed throughout absorptive cells
• surface area of membrane increased
• found on brush-border membranes

Question 7

What are the features of epithelial secretion?

Answer 7

• exocrine cells (into lumen)
• endocrine cells (into bloodstream)
• secretory epithelia organised into glands

Question 8

What is the difference between constitutive and stimulated secretory vesicles?

Answer 8

• constitutive: moves directly towards membrane and release contents
• stimulated: stored in cytoplasm and fuse with membrane to release contents after signal received

Question 9

What are the features of epithelial protection?

Answer 9

• usually stratified squamous
• keratinising cells (hardened and dead)
• non-keratinising cells (alive, visible nuclei)
• protects from heat, cold, solvents and abrasion

Question 10

When is cell turnover consistent?

Answer 10

cell loss = cell proliferation

Question 11

What are the differences in shape between squamous, cuboidal and columnar cells?

Answer 11

• squamous: wider than they are tall (plate shaped)
• cuboidal: as wide as they are long
• columnar: taller than they are wide

Question 12

What are the two types of layering you find in epithelia?

Answer 12

• simple: one layer

- stratified: several layers

Question 13

How do the epithelial layers establish epithelial polarity?

Answer 13

block paracellular pathways so molecules that want to pass across epithelia must pass through cells

Question 14

Describe cell division in the villus

Answer 14

• intestinal stem cells in crypt
• new cells shunted up the villus as other new cells form
• cells lost from the tip.

Question 15

What is Epidermolysis bullosa an example of?

Answer 15

disorder of cytokeratin and desmosomes