ANAT - Endocrine Glands

Question 1

embryological origin of anterior vs posterior pituitary

Answer 1

• anterior (adenohypophysis): Rathke’s pouch (oral ectoderm) - invagination of pharynx
• posterior (neurohypophysis): arises from neural extension of hypothalamus

Question 2

where is the pituitary gland located

Answer 2

• base of the sphenoid bone, just below the hypothalamus

Question 3

structure of the anterior vs posterior pituitary

Answer 3

• anterior is glandular (secretes own hormones) and no longer in contact with the brain
• posterior is non-glandular (hormones secreted in hypothalamus and travel via axons into posterior pituitary) and still in contact with the brain via pituitary stalk (infundibulum)

Question 4

3 sections of the anterior pituitary

Answer 4

• pars distalis - hormone production
• pars intermedia - b/n A/P pituitary
• pars tuberalis - tubular sheath that extends from pars distalis and winds around pituitary stalk

Question 5

contents of the infundibulum

Answer 5

• axons which connect SVN and SON (hypothalamus) to posterior pituitary via hypothalamo-hypophyseal tract (junction between hypothalamus and PP = median eminence)
• hypophyseal portal vessels: carry hypophysiotropic hormones from hypothalamus to anterior pituitary, small blood flow prevents dilution in general circulation

Question 6

which cells of the anterior pituitary secrete:
- GH
- TSH
- ACTH
- prolactin
- FSH and LH

Answer 6

• GH: somatotrophs
• TSH: thyrotrophs
• ACTH: corticotrophs
• prolactin: lactotrophs
• FSH and LSH: gonadotrophs

Question 7

2 main nuclei in the hypothalamus and where do they lead to?

Answer 7

• supraoptic (SON): produces ADH
• paraventricular (PVN): contains magnocellular neurons which produce oxytocin, and parvocellular neurons which produce other hormones e.g. GnRH, GHRH, CRH etc
• both travel to posterior pituitary via axons in pituitary stalk

Question 8

difference in staining of anterior vs posterior pituitary

Answer 8

• anterior stains a darker pink and can see many glandular cells with vesicles filled with hormones
• posterior stains lighter pink b/c nervous tissue

Question 9

describe the staining of acidophils, basophils, chromophobes of the anterior pituitary

Answer 9

• acidophils: light pink stain
• basophils: bright pink stain
• chromophobes: don’t stain very well b/c no granules

Question 10

layers + structure of the adrenal glands

Answer 10

ADRENAL CORTEX: epithelial cells
- zona glomerulosa: outermost layer, oval-shaped cells (secretes aldosterone)
- zona fasciculata: columnar cells - abundant SER, mitochondria and lipid droplets to secrete cortisol = foamy appearance
- zona reticularis: innermost later (secretes weak androgens e.g. DHEA, androstenedione)
ADRENAL MEDULLA: modified neurons - ANS (chromaffin cells) - secrete adrenaline (80%) + noradrenaline (20%)

Question 11

thyroid gland appearance + how does it synthesise and secrete hormones?

Answer 11

• follicles lined by simple epithelium and surrounded by rich capillary network (squamous or cuboidal) - functional unit
• parafollicular (C) cells between follicles make calcitonin - inhibits bone resorption
• epithelial cells secrete thyroglobulin into the lumen of the follicles, which combine it with iodine to form T3 and T4
• when required, epithelial cells extend processes into the follicles, engulf the hormone (pinocytosis) and release it back into circulation

Question 12

structure of the thyroid gland

Answer 12

• 2 lobes, isthmus in the middle
• attached to thyroid cartilage, anterior to tracheal rings 2-6

Question 13

is the thyroid larger in women or men?

Answer 13

• women (+ enlarges further during puberty, pregnancy, lactation, luteal phase of menstrual cycle)