Adrenal Gland Histology

Question 1

anatomy of the suprarenal glands

Answer 1

a. Suprarenal glands—AKA adrenal glands
i. Pair of triangular shaped glands, each about 2 inches long and 1 inch wide, superior to the kidney
ii. High vascularized

Question 2

2 parts of the adrenal gland and their embryological origins

Answer 2

a. 2 parts of the adrenal gland (cortex and medulla) develop from 2 different origins—on posterior abdominal wall from the urogenital ridge
i. cortex—mesodermal
1. develops from the celomic epithelium o fthe posterior abdominal wall
ii. medulla—ectodermal
1. develops from the neural crest cells

Question 3

fetal cortex of adrenal gland

Answer 3

a. by the 8th week of fetal development, these cortical elements have differentiated into a thin outer definitive cortex and a thick inner fetal cortex
i. fetal cortex actively produces fetal steroids during gestation, but involutes rapidly after birth

Question 4

accessory adrenocortical nodules

Answer 4

a. accessory adrenocortical nodules—ectopic adrenal tissue, accessory cortical tissue, hamartoma, accessory adrenal gland, supernumary adrenal, and adrenocortical rest
i. frequently located in contact with the capsule at one pole of the adrenal but can occur completely separated from the adrenal gland in the retroperitoneal fat

Question 5

adrenocortical rests

Answer 5

a. occur in up to 50% of newborn infants, but tend to atrophy and disappear in the postpartum period
i. the can be detected anywhere along the path of embryonic migration of adrenal cortex

Question 6

development of adrenal zones of adrenal gland

Answer 6

a. the development of the adrenal zones occurs slowly after birth, in parallel with regression of the fetal cortex, and is not completed until late in the first year of life

Question 7

functional adrenal cortex

Answer 7

a. definitive cortex persists and develops into the functional adrenal cortex, with distinct zonae glomerulosa and fasciculatae present at birth
i. zona reticularis develops during first year of life

Question 8

3 developmental events that require glucocorticoids?

Answer 8

a. During the early stage of gestation, the adrenal cortex synthesizes dehydroepiandrosterone (DHEA)—precursor of the synthesis of estrogen of the placenta
b. Lack of 3beta-hydroxysteroid dehydrogenase (3beta-HSD) activity prevents the synthesis of progesterone, glucocorticoids, and androstenedience
c. Interaction b/w the fetal adrenal cortex and placenta—fetoplacental unit

Question 9

congenital adrenal hyperplasia (CAH)

Answer 9

i. 3 beta hydroxysteroid dehydrogenase II deficient congenital adrenal hyperplasia (3-beta HSD CAH)
ii. results from a mutation in the gene for 3beta-HSD type II
iii. wide spectrum of clinical presentations
1. milder forms—result from incomplete loss of 3beta-HSD type II fcn
a. can produce virilization of genetically female infants
b. undervirilization of genetically male infants
i. only form of hypoadrenalism is the only form of CAH that can cause ambiguous genitalia in both sexes

Question 10

glucocorticoids

Answer 10

i. either of maternal origin or synthesized from placental progesterone by the fetus and are essential for 3 events:
1. production of surfactant by type II alveolar cells after the 8th month of fetal life
2. development of functional hypothalamopituitary axis
3. induction of thymic involution

Question 11

zona glomerulosa

Answer 11

a. outermost of cortex of adrenal gland
i. makes mineralocorticoids—aldosterone
1. produced in response to ACTH and angiotensin II
ii. lies under the capsule and is 10-15% of cortex
iii. cells aggregate into a glomerulus like arrangement and have a moderate amount of lipid droplets in the cytoplasm
iv. lacks the enzyme 17alpha hydroxylase—so cannot produce cortisol or sex steroids
v. aldosterone is made here and stimulates retention of Na in kidneys, retention of water, and renal secretion of K and H

Question 12

zona fasiculata

Answer 12

i. 75% of cortex
ii. secretes glucocorticoids and androgens
iii. cells contain many lipid droplets of cholesterol (steroid precursor) in cytoplasm
iv. cells appear vacuolated—foamy appearance
1. so, cells are called spongiocytes
v. contains cuboid cells—with the structural features of steroid producing cell arranged in longitudinal cords separated by cortical fenestrated capillaries

Question 13

zona reticularis

Answer 13

a. innermost of cortex of adrenal gland
i. innermost that is 5-10% of cortex
ii. cells in irregular cords that form anastomosing network
iii. secrete glucocorticoids and androgens
iv. although cells of ZF can synthesize androgens, the primary site of adrenal sex H production is the ZR
DHEA and androstenedione are the predominant androgens produced by cortex of adrenal gland
1. although DHEA and androstenedione are weak androgens, they can be converted to testosterone and even to estrogen in peripheral tissues

Question 14

what characteristics are shared by ZF and ZR?

Answer 14

1. Contain 17alpha hydroxylase to make glucocorticoids (cortisol) and 17, 20 hydroxylase to make sex Hs
2. Cortisol is not stored in cells and new synthesis, stimulated by ACTH, is required for achieving a hormonal increase in blood circulation
   a. Cortisol is converted in hepatocytes to cortisone
   b. Can be used synthetically as anti-inflammatory and anti-allergy
   c. Effects of cortisol:
   i. Metabolic—stimulates gluconeogenesis to increase the conc of glc in blood
   ii. Anti inflammatory—suppresses tissue responses to injury and dec cellular and humoral immunity
3. Although the ZF is odten associated with glucocorticoid production—mainly cortisol—the ZR with androgen production, the distinctions are not precise
4. Both layers stimulated by corticotropin (ACTH)

Question 15

adrenal medulla

Answer 15

neuroectodermic

makes catecholamines

Question 16

adrenal glands in women

Answer 16

major course of androgens in women—androgens stimulate growth of pubic and axillary hair during puberty

Question 17

chromaffin cells

Answer 17

i. composed of polyhedral cells arranged in cords or clumps
ii. regarded as modified sympathetic postganglionic neurons without postganglionic axons
iii. derived from neural crest
iv. lost axons and dendrites during embryonic development and have become secretory cells
v. secretory granules of epinephrine and norepinephrine
vi. adrenal medulla is innervated by sympathetic preganglionic fibers that release acetylcholine

Question 18

catecholamines

Answer 18

i. secreted into the blood instead of being secreted into a synapse, as in postganglionic terminals
ii. secreted in response to intense emotional rxns
iii. defensive rxn ot stress
iv. inc HR
v. dilates blood vessels of cardiac and skeletal M
vi. bronchiole dilation
vii. vasoconstriction of blood vessels supplying GI, kidneys, skin

Question 19

3 sources of blood supply of adrenal gland

Answer 19

i. inferior phrenic A give rise to superior adrenal A
ii. aorta from with the middle adrenal A branches
iii. renal A which gives rise to inferior adrenal A

Question 20

arterial plexus

Answer 20

a. all 3 sources enter the adrenal capsule and form an arterial plexus
i. 3 sets of branches from plexus
1. subcapsular plexus—one set supplies the capsule
2. short cortical A—second set enters the cortex forming the straight fenestrated capillaries/sinusoids, percolating b/w the ZG and ZF, and forming a capillary network in the ZR before entering the medulla
3. long cortical A—third set generates medullary As travel w/o branching and supplying blood only to the medulla

Question 21

tumor in the zona glomerulosa*

Answer 21

a. ZG: tumor localized in the ZG can cause excessive secretion of aldosterone
i. Primary aldosteronism—Conn’s syndrome
ii. A more common cause of hyperaldosteronism is an increase in renin secretion—secondary hyperaldosteronism

Question 22

tumor in the zona fasiculata*

Answer 22

a. ZF: increase in aldosterone, cortisol, and adrenal androgen production—secondary to ACTH production—occurs in Cushing’s Disease
i. Caused by an ACTH producing tumor of the anterior hypophysis
ii. Cushing’s syndrome—functional tumor of the adrenal cortex can also result in overproduction of cortisol, as well as of aldosterone and adrenal androgens

Question 23

causes of Cushing’s Syndrome

Answer 23

a. Endogenous—overproduction of cortisol caused by:
i. Pituitary tumor— Cushing’s Dz
ii. Adrenal tumor
iii. Other causes
b. Exogenous—taking meds containing glucocorticoids, such as hydrocortisone

Question 24

Addison’s Disease*

Answer 24

i. Chronic destruction of the adrenal cortex by an autoimmune process or TB
ii. ACTH secretion increases b/c of the cortisol deficiency
1. ACTH can cause skin pigmentation, in particular in the skin folds and gums
iii. Loss of mineralocorticoids leads to hypotension and circulatory shock
iv. Deficiency in cortisol causes muscle weakness
v. Symptoms:
1. Fatigue, lassitude, malaise, weakness, anorexia
2. Postural dizziness, syncope
3. GI symptoms: nausea, vomiting, abdominal pain, diarrhea, constipation
4. Myalgia, arthralgias
5. decreased libido, amenorrhea
vi. signs:
1. weight loss
2. hyperpigmentation
3. hypotension
4. thinning of axillary and pubic hair
5. vitiligo

Question 25

pheochromocytoma*

Answer 25

i. benign tumor of the chromaffin cells
ii. episodic secretion of epinephrine and NE
iii. signs/symptoms are those of SNS hyperactivity: elevated HR, BP, palpitations, diaphoresis, anxiety, headaches, nausea, pallor
iv. b/c of excessive catecholamine secretion, pheochromocytomas may precipitate life threatening hypertension or cardiac arrhythmias
v. up to 25% of pheochromocytomas are familial