Epithelial Tissues

Question 0

Explain the position, structure and function of the basement membrane

Answer 0

Thin, flexible, acellular layer that lies between epithelial cells and the subtending connective tissues
Consists of basal lamina
Thickness augmented by variably thick layer of reticular fibrils (type III collagen), elaborated by subtending connective tissue
Strong flexible layer to which cells adhere
Serves as a cellular and molecular filter

Question 1

Define epithelia

Answer 1

Sheets of continuous cells, of varied embryonic origin, that coder the external surface of the body and line internal surfaces

Question 2

Describe the ways in which epithelia are classified, explaining what is meant by the classification terminology: simple, stratified, pseudostratified, squamous, cuboidal, columnar

Answer 2

Simple - one layer of cells
Stratified - more than one layer of cells
Pseudostratified - looks like more than one layer but all cells are attached to basement membrane
Squamous - flattened shape
Cuboidal - square shape
Columnar - higher than wide

Question 3

Explain the reasons for different rates of renewal of each type of epithelium

Answer 3

Depends of location and function
Timeframe remains constant unless injury leads to acceleration
Epidermis - 28 days
Small intestine - 4-6 days

Question 4

Recognise the different types of surface specialisation found on epithelial cells (microvilli, stereocilia, cilia) and describe how their structure is related to their function

Answer 4

Microvilli - apical extensions which greatly increase surface area for selective absorption and secretion
Stereocilia - extended cilia characterised by length, lack of motility, contain actin filaments
Cilia - elongated, motile, move material along cell surface, arises from a centriole

Question 5

Define metaplasia and neoplasia

Answer 5

Metaplasia - reversible conversion from one differentiated epithelia to another to better cope with conditions
Neoplasia - change resulting from disease e.g. tumour