BIOL 2P93 Lecture Notes - Growth Hormone, Aldosterone, Cortisol

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Histology—Endocrine Glands
I. Pituitary Gland
a. Adenohypophysis
i. Pars tuberalis—“collar” of cells around neural stalk
ii. Pars Intermedia—cells surround colloid-filled follicles
iii. Pars Distalis (Anterior Lobe)—major part of pituitary
b. Neurohypophysis (Posterior Lobe)—derived from base of brain
i. pars nervosa (infundibular process)
ii. infundibulum (neural stalk)
iii. composed mainly of ~100,000 unmyelinated nerve fibers whose cell
bodies reside in hypothalamus
iv. secretes ADH & oxytocin, which are synthesized by the cell bodies w/in
the brain & travel down the axon (via neurophysins) to neurohypophysis
for storage
v. Herring bodies—thickened terminals at end of axons where hormones
(neurosecretory material) is stored
c. Vasculature
i. all capillaries are fenestrated (blood brain barrier doesn’t exist in pituitary)
ii. contains a portal system = hypophyseoportal system (allows hormones
from neurohypophysis to affect adenohypophysis)
d. Cells of Adenohypophysis
i. Chromophils
1. Acidophils—small w/ distinct dark nucleus; EM: largest granules
a. Somatotrophs—secrete GH or somatotropin
b. Mammotrophs (Lactotrophs)—secrete prolactin (PRL)
2. Basophils—larger & can usually see golgi apparatus
a. Thyrotrophs—secrete TSH
b. Gonadotrophs—secrete LH & FSH
c. Corticotrophs—secrete ACTH
ii. Chromophobes—little affinity for common stains
II. Adrenal Glands
a. Cortex—synthesis & secretion of androgens, glucocorticoids &
i. Origin—mesoderm (along w/ gonads & kidneys)
ii. Composed of 3 different layers
1. Zona glomerulosa—makes aldosterone (mineralocorticoid); cells
are grouped into small irregular clusters
2. Zona fasciculata—makes glucocorticoids (cortisol); cells
arranged in fairly straignt cords w/ capillaries between them
3. Zona reticularis—makes sex steriods (androgens); cells in cords
run in various directions
b. Medulla—synthesis & secretion of catecholamines (epi & norepi)
i. Origin—NCC’s (ectoderm)
ii. Catecholamines
1. 90% of secreted hormone from medulla is Epinephrine
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