TOPIC 3 - Skin

Question 1

What is the function of the endocrine gland: The thyroid gland?

Answer 1

• is essential for growth, development and metabolism.
• Requires Iodine.
• Hormones T3 and T4 are produced by folicular cells are stored in colloid.
• Regulates transcription of proteins via nuclear receptors.

Question 2

Explain the function of the Parathyroid gland.

Answer 2

• synthesises and secreted parathyroid hormone (a peptide hormone).
• regulates plasma levels of calcium and phosphate

Question 3

What is the function of the adrenal gland? (cortex and medulla)

Answer 3

Adrenal cortex = releases steroid hormones

• Glucocorticoid e.g cortisol
• Mineralolcorticoid e.g aldosterone

Adrenal medulla = releases catecholamines: adrenaline and noradrenaline

• chromaffin cells release adrenaline.

Question 4

What is the role of the ovaries?

Answer 4

cells within the developing follicles of the ovary produce oestrogen (cell proliferation of the endometrium) and progesterone (seceretion and maturation of tissues).

Question 5

What is the role of the testes?

Answer 5

• Leydig cells in the testes produce testosterone

- protein synthesis

Question 6

What is the function of the endocrine pancreas?

Answer 6

Has islets of langerhans where…

B cells release insulin
a - alpha cells produce glucagon

Question 7

what is the function of the hypothalamus?

Answer 7

Links neural activity to whole body function.

Question 8

What 2 organs make up the pituitary gland?

Answer 8

• the anterior and posterior lobe

Adenohypothesis - anterior pituitary lobe: troph cells stimulated from releasing hormones from small diameter neurons of the hypothalamus

Neurohypothesis - posterior lobe of pituitary: releases hormones from large diamter neurons directly into systemic circulation.

Question 9

What is epithelia?

Answer 9

tissues at the ‘boundaries’ of our body which seperate internal from external environment.

Question 10

What germ layers do epithelia develop from?

Answer 10

ALL germ layers - endoderm, ectoderm and mesoderm

Question 11

What are the 4 properties of epithelial cells?

Answer 11

1. Polarity - determines specialisations
2. Basement membrane :
   - basal lamina
   - reticular lamina - fires anchoring BL to connective tissue (collagen/ elastin)
3. Cell adhesion and communication:
   - is lateral communication through gap junctions
4. Cell replacement - there is continual cell replacement from stem cells. (underlying matrix can be replaced)

Question 12

How do epithelial-mesenchymal interactions regulate epithelial fate?

Answer 12

Epithelial cells can disassemble and migrate away so mesenchymal cells can be induced to form an epithelium.

Mesenchymal tissues control cell-fate.

Question 13

what are the 4 types of basic epithelia?

Answer 13

1. simple - one layer of cell (e.g in lung)
2. statified - many layers of cells (in skin)
3. Pseudo-stratified (in upper respiratory tract)
4. transitional (urothelium)

Question 14

What is the diffrence between endocine and exocrine?

Answer 14

endocine = ductless secretion

exocrine = seceretion with ducts

Question 15

What are the 3 layers of the skin?

Answer 15

top to bottom:

epidermis
dermis
hypodermis

Question 16

what is the role of the Dermis?

Answer 16

dermis the connective tissue beneath epidermis:

• dermis is thicker than the epidermis
• mainly collagen with elastic and reticular fibres
• has papillary layer - loose connective tissue
• has reticular layer - dense irregular connective tissue

Question 17

What is the structure of the epidermis?

Answer 17

a keratinised stratified squamous epithelium

Question 18

What are the 4 types of stratified skin?

Answer 18

1. stratum basale
2. stratum spinosum
3. stratum granulosum
4. stratum corneum

(stratum lucidum - only in thick skin)

BSGC

Question 19

what is the role of Stem cells in skin?

Answer 19

Stem cells are undifferentiated cells that can undergo mitosis.

They are in contact with the basement so maintain their ability to replicate.

ONLY cells in contact with the basement membrane can maintain their ability to replicate.

Question 20

What is the role of melanocytes?

Answer 20

they synthesise the pigment melanin which give skin its colour.

• Pheomelanin - red soluble pigment (lips)
• Eumelanin - brown/black insoluble pigment.

Question 21

Why does skin have a barrier function?

Answer 21

Protects against water loss, physical injury and infection by microbes.

Physical barrier - cross linked keratin layer on kertinocytes scaffold.

Biochemical barrier

Question 22

Why does skin play a major role in thermoregulation?

Answer 22

There are thermoreceptors in epidermis.

• Postganglionic sympathetic fibres release norepinephrine, causing vasoconstriction.
• Preganglionic sympathetic fibres release Ach and cause vasodilation