Epithelial Tissue - Classification by Function

Question 1

Simply name the functions which can be used to classify epithelial tissues

Answer 1

. Secretion
. Absorption
. Protection/ barrier function - mechanical & chemical protection: radiation, dessiccation, toxins, invasion by pathogens, physical trauma

Question 2

Explain for microvilli:
- the location where they are found
- their function

Answer 2

• Microvilli is on columnar epithelium of gut
• Increases surface area- called brush border
• Microfilament (actin) core
• Allows cells to change shape

Question 3

Explain for cilia on the pseudostratified columnar epithelium
- the location where they are found
- their function

Answer 3

. Respiratory tract
Used to propel mucus upwards and out- mucociliary escalator

Question 4

. Stem cells & differentiated cells in epithelial tissues - fill in the blans
Epithelial cells are constantly renewed by ….
Epidermis is renewed at the …… - then cells …. to the surface
skin is …. to form ….cytes - this process takes a …
Some epithelial tissues are only …. when damaged, for example, the ….

Answer 4

. mitosis
. basal layer
. migrate, kertainised to form keratinocytes, month
. renewed, kidneys

Question 5

Polarity: Apical & basolateral surfaces
2 domains (apical and basolateral) which have distinct morphological, biochemical, functional differences
The structure of these domains is related to function
. How is the polarity of domains maintained?
. State the roles of 2 domains

Answer 5

. - By preventing the lateral diffusion of integral membrane proteins between the 2 domains
. Role of 2 domains:
Apical: rich in ion channels and protein carriers, for: protection, secretion, absorption, regulation of nutrient and water uptake
Basolateral: has junctional specialisations, for: cell contact, adhesion, communication, ion channels, receptors, basal infoldings

Question 6

Basement membrane:

Sheets of specialised ECM with GAGs for epithelial anchorage

Acts as a mechanical barrier, boundary between epithelium and connective tissues

A diffusion barrier, can be a molecular sieve or permeability barrier depending on pore size as determined by GAG arrangement (like in kidneys)

Forms 2 sheets:

Basal lamina is synthesised by epithelial cells and contains anchoring fibrils of type 4 collagen which extend into the reticular lamina

Reticular lamina is produced by the connective tissue and contains fibres and collagen bundles on which fibrils loop