Epithelial tissues

Question 1

Types of epithelium

Answer 1

Covering (lines cavities and other surfaces) and glandular (secretory epithelial cells).

Question 2

Layers of the basement membrane

Answer 2

Basal lamina (lamina lucida + lamina densa) and reticular lamina.

Question 3

3 factors of epithelium nomenclature

Answer 3

1) Number of layers- simple vs stratified/ compound
2) Shape of cells- cuboidal, columnar, squamous
3) Specialisation- cilia, microvilli, keratinisation

Question 4

Exceptions to classifications

Answer 4

Pseudostratified- all cells connected to BM, but with appearance of stratification.
Transitional- found excl. in bladder and ureters

Question 5

Functions of epithelia

Answer 5

1) Forming a protective barrier
2) Regulation of the exchange of molecules between compartments
3) Synthesis and secretion of glandular products

Question 6

Structure of epithelial tissues

Answer 6

Epithelial cells form continuous sheets comprising one or more layers of cells. They are bound by cell junctions, and are supported by a basement membrane.

Question 7

Polarisation of epithelial tissues

Answer 7

Epithelial cells have an apical surface, a basal surface, and lateral (side) surfaces.

Question 8

Glandular epithelia

Answer 8

Epithelial tissue that is involved in secretion may be arranged into structures called glands. These may be exocrine glands, which secrete onto the epithelial surface via a branching system of ducts, or endocrine glands, which secrete directly into the bloodstream.

Question 9

Simple epithelia

Answer 9

Surface epithelia comprised of a single layer of cells. Often involved in selective diffusion, absorption and/or secretion. Provides little protection against abrasion.

Question 10

Stratified epithelia

Answer 10

Epithelia consisting of two or more layers of cells. Protects against mechanical stress. Poorly suited for diffusion or absorption due to thickness.

Question 11

Apical specialisations

Answer 11

Cilia- composed of microtubules, motile, found in respiratory/reproductive tract.
Microvilli- composed of actin filaments, less motile but more widespread, found in absorptive tissues ie. kidney/digestive tract.
Keratin- cytoskeletal protein forms a strong but flexible impermeable protective barrier.

Question 12

Function of the basement membrane

Answer 12

Provides structural support for the epithelia, facilitates the passage of materials with supporting tissues, allows cells to receive innervation.

Question 13

Function of cell junctions

Answer 13

Allows cells to form a continuous, cohesive layer. Operate as communication channels governing functions such as growth and cell division.

Question 14

Types of cell junction

Answer 14

TJ= tight junctions (zonula occludens)
ZA= zona adherens (adherens junctions)
CJ= communicating junctions (gap junctions)
D= desmosomes (macula adherens)
HD= hemidesmosomes