Topic 7 - Epithelial tissues: definition and classification

Question 1

Definition:

Answer 1

-cover or line external and inernal body surfaces, cavities and tubes.

Question 2

Function:

Answer 2

-as interfaces between different biological comounds

For: diffusion, absorption, secretion, sensory function and physical protection

Question 3

Origin:

Answer 3

Ectoderm (corneal epithelium, epidermis of skin, glands)
Entoderm (alimentary tract, intestinal glands, liver pancreas)
Mesoderm(Kidey, reproductive system, endothelium, mesothelium)

Question 4

Blood supply

Answer 4

Normaly avascular, except the pharyngeal epithelium of frogs, or in urinary bladder of rabits.

Question 5

Nerve supply

Answer 5

Innervated tissue, contains nerve endings (free or associated to specialized sensory cells)

Question 6

Tissue components:

Answer 6

Cells are closeley packed (squamos, cuboidal, columnar) and intracellular matrix is reduced to the glycocayx of adjacent cells.

Question 7

Functional basis

Answer 7

Surface epithelia, glandular epithelia, absorptive epithelia, pigment epithelia and sensory epithelia.

Question 8

Classification

Answer 8

Based on shape of cells and nr. of layers:

• Simple (one layer): squamous, cuboidal and columnar
• Stratified (several layers): - - -
• Pseudostratified
• Transitory