Endocrine Histology

Question 1

What is the anatomical location of the pituitary gland?

Answer 1

sits in the sella turcica of the sphenoid bone

Question 2

What are the embryonic origins of pituitary gland?

Answer 2

• anterior: upgrowth of the oral ectoderm
• posterior: downgrowth of the future diencephalon

Question 3

Does the posterior or anterior pituitary gland stain darker?

Answer 3

anterior

Question 4

What are the three regions of the anterior pituitary and their structural components?

Answer 4

• Pars Distalis: hormone synthesis, cells in cords wrapped in CT, fenestrated capillaries
• Pars Intermedia: colloid cysts, functionally unimportant
• Pars Tuberalis: scaffold of capillaries for hypophyseal portal system

Question 5

What cells are found in the Pars Distalis?

Answer 5

• chromophils (acidophils, basophils)
• chromophobes

Question 6

What do basophils synthesize?

Answer 6

• FSH
• LH
• ACTH (from precursor POMC)
• TSH

Question 7

What do acidophils synthesize?

Answer 7

• PRL
• GH

Question 8

What is the pathway of releasing hormones from hypothalamus to the pars distalis?

Answer 8

neurons of the hypothalamus –> capillary beds in pars tuberalis –> hypophyseal portal vein –> capillary beds of the pars distalis

Question 9

What is the regulation and feedback pathways of GH?

Answer 9

GHRH –> hypophyseal portal system –> anterior pituitary –> acidophil receptors –> release of GH –> bloodstream –> liver cells –> release IGF –> various tissues –> HIGH levels of IGF inhibit GH and GHRH synthesis

Question 10

What are the two regions of the posterior pituitary and their structural components?

Answer 10

• Pars Nervosa: neurosecretory bodies that store hormones
• infundibular stalk: hypothalamic neurons run through stalk and terminate in nervosa

Question 11

What is another name for neurosecretory bodies?

Answer 11

herring bodies

Question 12

What are the cells of the posterior pituitary?

Answer 12

• Pituicytes: support cells
• Herring bodies: store oxytocin ADH

Question 13

What does diminished ADH production lead to?

Answer 13

diabetes insipidus –> production of large quantities of dilute urine (polyuria), dehydration and extreme thirst (polydipsia)

Question 14

What does oxytocin stimulate?

Answer 14

smooth muscle contractions of the uterus during labor and menstruation and myoepithelial cells of the mammary glands to eject milk

Question 15

What is the regulation and feedback pathways of Oxytocin?

Answer 15

suckling –> neurons of PVN stimulated –> oxytocin release –> blood stream –> mammary glands –> continued suckling –> more oxytocin

Question 16

What occurs with a pituitary adenoma that contains overactive acidophils?

Answer 16

giantism (children)
acromegaly (adults)

Question 17

What is the thyroid and what does it synthesize?

Answer 17

• encapsulated gland of the anterior neck inferior to the larynx, abutting the trachea
• synthesizes Thyroid Hormone (T3 and T4) and Calcitonin

Question 18

What is the histological component of the thyroid?

Answer 18

Follicles - colloid spaces surrounded by follicular epithelium containing parafollicular cells and follicular cells

Question 19

What are the functions thyroid follicular cells and what are they stimulated by?

Answer 19

• synthesize thyroglobulin and store it in colloids iodine
• cleave iodinated thyroglobulin into T3 and T4
• stimulated by TSH

Question 20

What does chronic Iodine deficiency lead to?

Answer 20

inhibits T3 and T4 production (thyroglobulin is still made)

Question 21

What are the functions of T3 and T4?

Answer 21

• development: brain and bones
• metabolism regulation: O2, heat, lipid/carb metabolism
• amplifies SNS response

Question 22

What is the regulation and feedback pathways of Thyroid Hormone?

Answer 22

stimulus –> TRH from hypothalamus –> thyrotropic cells of AP release TSH –> TH release –> increase metabolic activities –> increased body temp inhibits TRH, increase in TH decreases TRH receptors in AP

Question 23

What are Parafollicular cells (C Cells) and what is their function?

Answer 23

cells that synthesize calcitonin to decrease blood Ca2+
- stimulate osteoblasts
- inhibit osteoclasts

Question 24

What are Parathyroid Glands and what is their function?

Answer 24

4 seed-sized glands attached to the posterior surface of the thyroid that increase blood Ca2+ levels through PTH

Question 25

What are the cells of the Parathyroid Glands and what are their functions?

Answer 25

- Chief cells: synthesize parathyroid hormone - Oxyphils: no known function

Question 26

What does Hypoparathyroidism cause?

Answer 26

diminished PTH causes abnormal muscle contractions and more mineralized bones

Question 27

What is Calcitriol and what is its function?

Answer 27

active vitamin D activated by PTH - stimulated the intestines to absorb calcium from digested foods

Question 28

What are the adrenal glands and what are their function?

Answer 28

encapsulated triangular glands on the superior aspect of the kidneys that contains an outer cortex and inner medulla - cortex --> produces steroid hormes - medulla --> produces EN and NE

Question 29

What are the zones of the Adrenal Cortex and their components?

Answer 29

- Zona Glomerulosa: cells arranged in balls beneath the capsule - Zona Fasciculata: middle layer containing columns of cells with CT and capillaries - Zona Reticularis: zone closest to medulla with looser arrangements of cells

Question 30

What cells are located in the Zona Glomerulosa and what is their role?

Answer 30

foamy cytoplasm cells with large amounts of lipids that produce aldosterone

Question 31

Where does aldosterone act and what is its role?

Answer 31

molecule acts on kidneys --> distal tubules and collecting ducts to - increases reabsorption of sodium (Na⁺) via Na⁺/K⁺ ATPase pumps - increases blood volume & pressure → water follows Na⁺ osmotically - secretion of Potassium (K⁺) into urine in exchange for reabsorbed sodium

Question 32

What is the pathway of the Renin-Angiotensin-Aldosterone System (RAAS)?

Answer 32

Drop in BP/volume → Kidney releases renin → liver produced angiotensinogen is converted to angiotensin I by renin → ACE from the lungs converts angiotensin I → angiotensin II --> vasoconstriction and aldosterone release

Question 33

What cells are located in the Zona Glomerulosa and what is their role?

Answer 33

- cells similar to ZG but they primarily make Cortisol to stimulate gluconeogenesis, lipolysis and sympathetic (stress) response ** simulated by ACTH

Question 34

What cells are located in the Zona Glomerulosa and what is their role?

Answer 34

cells have fewer lipids and make dehydroepiandrosterone (DHEA), a precursor to androgens such as testosterone and estrogen ** simulated by ACTH

Question 35

What are the symptoms of adrenal insufficiency based on each of the three layers affected?

Answer 35

- ZG: low aldosterone → hyponatremia and hypovolemia → dizziness, fatigue and salty food cravings - ZF: low cortisol → increase in POMC, low blood glucose during stress → hyperpigmentation, weakness, fatigue, disorientation - ZR: low DHEA → loss of armpit hair, pubic hair and decreased sex drive in women

Question 36

What is the Adrenal Medulla and what are the cells?

Answer 36

internal portion of the adrenal gland that contains large veins and Chromaffin cells

Question 37

What are Chromaffin Cells and what stimulates them?

Answer 37

cells that make NE and EN that are stimuklated by axons of preganglionic sympathetic neurons whose cell bodies are in the intermediate horn of the spinal cord