Epithelium

Question 1

what are the functions of epithelium? (6)

Answer 1

a) Protects- covers and lines surfaces (e.g. skin)
b) Absorption-have surface specializations to increase absorptive area (e.g. intestines)
c) Secretion-form glands (e.g. goblet cells)
d) Transcellular transport – carries molecules and regulates movement between body compartments through mechanism of selective permeability (e.g. kidney)
e) Sensation- specialized epithelia (taste buds and inner ear)
f) Contractility- myoepithelial cells are specialized epithelial cells that help to “squeeze” secretory products from glands (e.g. basket cells)
etymology: “epi= above” and “thelia=nipple”

think “ skin, secretion/glands, and sensation

Question 2

what is the structure of epithelia?

Answer 2

a) Basal lamina (BL) is always between the epithelial cells and connective tissue (CT)
b) Epithelia cells either line surfaces, including vascular structures, or make glands
c) Vasculature usually does not penetrate the basal lamina as it is epithelial itself, nerves can penetrate through

Question 3

what are the functions of basil lamina? what is it?

Answer 3

a) Basal lamina (BL) is always between the epithelial cells and connective tissue (CT)
1. Determines polarity of cells that rest on it
2. Tissue boundaries- restricts epithelial cells from entering CT (anti metastatic)
3. Participates in attaching epithelia to CT

Question 4

what are the contents of basal lamina

Answer 4

laminin and type IV collagen which is secreted by the basal pole of epithelia cells

Reticular fibers: type III collagen secreted by the CT cells

Question 5

what is the difference btwn basal lamina and basement membrane?

Answer 5

• BM has:

1 Basal Lamina- made by epithelia
2 Hemidesmosomes- made by epithelia
3 Underlying reticular fibers- made by underlying connective tissue

also:
BM can be seen with light microscopy but BL requires TEM
-BM found in renal glomeruli are composed of two BL

Question 6

basic characteristics of epithelia?

Answer 6

□ Avascular- get nutrients from vessels in underlying CT
□ Tightly packed- very little extracellular space, close juxtaposition gives polyhedral shape
□ Cells have a range of shapes from high columnar, equal-sized cuboidal, and low, flat squamous
□ Cells rest on CT, between which is a basal lamina
□ Lamina propria of the digestive, respiratory, and urinary systems
□ Cells are polarized into three regions: apical, basal, and lateral poles
□ Continuous renewal with variable turnover rate in various epithelia (cancer susceptibility