Basic Principles - Epithelium

Question 1

Define the term tissue

Answer 1

A tissue is an aggregation of cells organised to perform one or more specific functions

Question 2

What are the 4 types of tissue

Answer 2

Nervous - fast communication, brain
Connective - support, dermis of skin
Muscle - movement
Epithelium - lining

Question 3

What are the 2 types of epithelium?

Answer 3

Lining epithelium - endothelium lines cardiovascular system, mesothelium lines internal cavities
Glandular epithelium - classified as connective tissue

Question 4

What are the 2 types of glandular epithelium?

Answer 4

Endocrine - secrete product into bloodstream and has no ducts
Exocrine - secrete product onto a surface via ducts

Question 5

What are the 3 mechanisms of secretion in glandular epithelium?

Answer 5

Merocrine - secretion occurs via exocytosis, where the substance is released from the cell without significant loss of cellular material
Holocrine - whole cell ruptures during release of product (sebaceous glands)
Apocrine - secretion involves the loss of a portion of the cell cytoplasm along with the substance being secreted

Question 6

What are the 4 types of lateral specialisations?

Answer 6

Tight junctions
Intermediate junctions
Desmosomes
Gap junctions

Question 7

How do you classify lining epithelium?

Answer 7

Number of layers - simple or stratified
Shape of cells - cuboidal, squamous or columnar
Presence of surface specialisations - keratin, cilia

Question 8

How do you classify exocrine glands?

Answer 8

Duct type;
* simple - unbranched ducts
* compound - branched ducts
Composition of secretion;
* serous glands - watery, enzyme-rich fluid
* mucous glands - Secrete a thick, viscous fluid rich in glycoproteins called mucins, which form mucus when hydrated
* mixed glands - both
Mode of secretion - apocrine, merocrine, holocrine
Structure;
* unicellular - Composed of single cells dispersed among other cell types
* multicellular - Consist of clusters of glandular cells that work together to produce and secrete substances.

Question 9

What are the morphological features of lining epithelium?

Answer 9

All cells in epithelial sheet are continuous so no intracellular substance between cells
Epithelial cells are polarised - have different surface regions apical and basal which carry out different functions
Avascular
Epithelial cells lie on a basement membrane
Apical membranes face is a free surface