Endocrine tissues - lecture 8

Question 1

Explain how the majority of ductless glands are derivatives of epithelial tissues.

Question 2

Define ‘hormones’.

Answer 2

Signalling molecules that leave the tissue/organ altogether and enter the blood where they can travel to distant sites where they exert their activities.

Question 3

Where is the pituitary gland (hypophysis) and what does it secrete?

Answer 3

Base of the brain.

Anterior (front):
- Thyroid-stimulating hormone (TSH)
- ACTH
- Gonadotrophins - FSH and LH
- Growth hormone (GH)
- Prolactin (PRL)
- MSH

Posterior (nerve part):
- Vasopressin (ADH)
- Oxytocin (OXT)

Question 4

Where is the thyroid gland and what does it secrete?

Answer 4

Two lobes which are anterior to the trachea.

Thyroxine (T4) and triiodothyronine (T3), calcitonin (regulates calcium).

Question 5

Where is the parathyroid gland and what does it secrete?

Answer 5

On the dorsal surface of the thyroid gland. 4 glands in 2 pairs.

Parathyroid hormone (PTH).

Question 6

Where are the adrenal glands and what do they secrete?

Answer 6

Top of the superior poles of kidneys.

Medulla (middle):
- Catecholamines - adrenaline, noradrenaline and dopamine.

Cortex (outside):
- Corticosteroids.
- Glucocorticoid (cortisol and cortisone)
- Mineralocorticoids (aldosterone)
- Androgenic steroid hormone precursors (androstenedione and dihydroepiandrosterone (DHEA).

Question 7

Which hormones are examples of glycoproteins and peptide hormones?

Answer 7

Insulin
Glucagon
Prolactin
ACTH
ATH
Gastrin.

Question 8

Which hormones are examples of steroid hormones?

Answer 8

Oestrogens
Androgens
Progesterone
Cortisol
Glucocorticoids

Question 9

Which hormones are examples of amino acid derived catecholamines hormones?

Answer 9

Adrenaline
Noradrenaline
Dopamine

Question 10

Which hormones are examples of amino acid derived thyroid hormones?

Answer 10

Thyroxine (T4)
Triiodothyronine (T3)

Question 11

Which hormones are examples of lipid hormones?

Answer 11

Thromboxanes
Prostglandins
Endocannabinoids

Question 12

What is the portal circulatory route?

Answer 12

Blood travels through one set of capillaries, then collects in a portal which branches off into another set of capillaries before entering veins which lead to the heart.

One example if the hypothalamo-hypophyseal portal system.

Question 13

What are parafollicular cells?

Answer 13

• Cells that make calcitonin.
• They are neuroendocrine cells that migrate to the thyroid during thyroid development in the embryo.
• Monitor plasma concs and decrease Ca2+ levels.
• Inhibits osteoclast activity (breaking down bone to increase Ca2+ levels).
  Inhibits renal calcium and phosphate reabsorption in the tubular cells, so more calcium and phosphate is excreted.

Question 14

Describe the exocrine function of the pancreas.

Answer 14

This constitutes the acinar and duct cells.
It produces:
- Trypsinogen (converted to trypsin)
- Chymotrypsinogen (converted to chymotrypsin)
- Lipase
- Amylase
- Ribonuclease
- Deoxyribonuclease
- Gelatinase
- Elastase

Question 15

Describe the endocrine function of the pancreas.

Answer 15

Islet of Langerhans are the endocrine cells.
Producing:

Alpha cell - GLUCAGON (catabolises glycogen to glucose

Beta cell - INSULIN (uptake and storage of glucose)

Delta cell - SOMATOSTATIN (inhibits insulin and glucagon secretion)

PP cell - PANCREATIC POLYPEPTIDE (inhibits bile, pancreatic enzyme and bicarbonate secretion)

D-1 cell - VASOACTIVE INTESTINAL PEPTIDE (similar to glucagon, stimulates enzymatic secretion and gut motility)

EC cell - SECRETIN (stimulates bicarbonate production), MOTILIN (increases gastric and intestinal motility), SUBSTANCE P (pain relief (analgesia)

E cell - GHRELIN (increases feeding behaviour)

G cells - GASTRIN (stimulates HCl production by stomach)