Endocrine System

Question 1

HORMONES

Answer 1

Hormones are chemical messengers synthesized by cells and released into tissue spaces
around blood and lymph capillaries to act on target tissues.
All endocrine glands have:
(1) a rich blood supply
(2) no ducts
(3) cells arranged in blocks, islets, plates, or cords.

Question 2

PITUITARY GLAND cells

Answer 2

1. Acidophils: synthesize GH (somatotropin) and prolactin. Granules in the cytoplasm stain reddish as a result of an acidophilic dye.
2. Basophils: synthesize FSH, LH, TSH, and ACTH. Granules in the cytoplasm stain poorly with H&E as a result of a basophilic dye.
3. Chromophobes: can differentiate into acidophils or basophils and do not have an affinity preference.

Question 3

ADRENAL GLAND (SUPRARENAL)

Answer 3

3 zones:
Zona Glomerulosa: secrete mineralocorticoids e.g. aldosterone to maintain fluid and electrolyte balances.
Zona Fasciculata: middle area- has large, fat droplets filling the cells.
Zona Reticularis: inner zone- consists of branching network cords of cells amongst sinusoids.

Question 4

THYROID GLAND

Answer 4

This gland consists of 2 lobes below the larynx with an isthmus connecting the lobes.
- responsible for the synthesis of the hormones thyroxin (T4) and (triiodothyronine (T3). A smaller number of cells are the parafollicular or C cells which occur in clusters between the follicles producing the hormone calcitonin.

• Thyroid hormones accelerate metabolic processes of the body, which increases the basal metabolic rate (BMR).
• reduce the concentration of calcium salts in the blood by the inhibition of bone resorption.

Question 5

PARATHYROID GLAND

Answer 5

These are 4 small glands behind the thyroid, embedded in the thyroid capsule.
A lowering of blood calcium causes the release of the parathyroid hormone into the blood. The hormone stimulates the rate of activity of osteoclasts to absorb the calcified bone matrix. The osteolytic activity of the osteoclasts increases the blood calcium to normal
levels.