endocrine histology

Question 1

location of pituitary

Answer 1

situated in the sella turcica

Question 2

components of pituitary

Answer 2

1. The anterior pituitary, or adenohypophysis, made up of the pars distalis, pars intermedia,
   and pars tuberalis. 2. The posterior pituitary, or pars nervosa (or infundibular process), the infundibular stem or stalk, and the median eminence. 1. The anterior pituitary, or adenohypophysis, made up of the pars distalis, pars intermedia,
   and pars tuberalis. 2. The posterior pituitary, or pars nervosa (or infundibular process), the infundibular stem or stalk, and the median eminence. 1. The anterior pituitary, or adenohypophysis, made up of the pars distalis, pars intermedia,
   and pars tuberalis. 2. The posterior pituitary, or pars nervosa (or infundibular process), the infundibular stem or stalk, and the median eminence.

Question 3

embryonic origins of pituitary

Answer 3

The anterior pituitary is derived embryonically from an outgrowth of endoderm called Rathke’s pouch, while the posterior pituitary is really an extension of the brain (the hypothalamus).

Question 4

What hormones are released from anterior pituitary and what are the cells that release them

Answer 4

growth hormone (somatrotrophs), prolactin (lactotrophs), follicle stimulating hormone and luteinizing hormon (gonadrotrophs), adrenocorticotropin hormone (corticotrophs) and thyroid stimulating hormone (thyrotrophs)

Question 5

vasculature of anterior pituitary

Answer 5

Blood enters median eminence from superior hypophyseal arteries which carry regulatory peptides (releasing factors) secreted by hypothalamic neurons and then travels through the pars tuberalis. These vessels then go to the pars distalis where an extensive vascular network is located and anterior pituitary cells secrete their horomones into capillaries. Blood leaves pituitary via hypophyseal veins

Question 6

List the releasing factors secreted by hypothalamic neurons

Answer 6

TSH-releasing hormone (TRH), gonadotropin releasing hormone (GnRH), corticotropin releasing hormone (CRH), growth hormone releasing hormone (GHRH) and the inhibitory factors, somatostatin and dopamine.

Question 7

function of pars intermedia

Answer 7

Poorly developed in humans- consists of colloidal cysts. Some cells are corticotropes and produce melanocyte stimulating hormone

Question 8

staining of cells in anterior pituitary

Answer 8

Growth hormone and prolactin are associated with acidophils (reddish). TSH, ACTH, LH and FSH are associated with basophils (bluish)

Question 9

hormones of the posterior pituitary and how they are made

Answer 9

Antidiuretic hormone (ADH, vasopressin) and oxytocin, are released from the ends of axons that arise from cell bodies of neurons present in the hypothalamus. They are released as prohormones vasopressin-neurophysin and oxytocin-neurophysin which are cleaved during vesicular transport down the axon.

Question 10

structure of posterior pituitary

Answer 10

cell bodies in the hypothalamus extend unmyelinated axons through the infundibular stalk into the post. Pituitary where the axons expand into bulbous structures containing neurosecretory vesicles (herrings bodies). There are nuclei in the posterior piuitary of pituicytes- supportive astrocyte-like glial cells which don’t produce hormones.

Question 11

anterior vs posterior pituitary on staining

Answer 11

anterior pituitary will be highly vascular and have large number of clumped endocrine cells with large round nuclei. Posterior pituitary has a few nuclei (pituicytes) but mostly just the ends of axons

Question 12

structure of thyroid gland

Answer 12

multi-lobed gland with series of follicles wich each contain a single layer of epithelial cells surrounding a central chamber called the colloid. Thyroid hormone is stored in the colloid.

Question 13

What produces thyroid hormone

Answer 13

The epithelial cells produce the colloid and eventually the thyroid hormone group.

Question 14

What cells produce calcitonin and what is its function

Answer 14

scattered “C” cells of the thyroid between follicles. This hormone decreases release of calcium from bones by down regulating osteoclast activity.

Question 15

blood supply to and from the thyroid

Answer 15

Blood supply to the thyroid is via the inferior thyroid artery (from the thyrocervical trunk) and the superior thyroid artery (from the external carotid artery); drainage is from the inferior thyroid vein (to the subclavian vein) and the superior thyroid vein (to the jugular vein)

Question 16

Where is thryoglobulin synthesized

Answer 16

The thyroid epithlium secretes thyroglobulin into interior of follicle and then digests it to generate thyroid hormone

Question 17

What cofactor is required for thyroid hormone synthesis

Answer 17

iodide- Extensive vascularization around the follicles
enables iodide pumping from the blood and conversion to iodine by the epithelial cellsiodide- Extensive vascularization around the follicles
enables iodide pumping from the blood and conversion to iodine by the epithelial cells

Question 18

Function of TSH

Answer 18

Stimulates synthesis of thyroglobulin and its uptake/breakdown from the colloid with consequent release of T3 and T4

Question 19

steps of thyroid hormone production

Answer 19

epithelial cells uptake iodide > convert to iodine > secrete into central colloid > epithelial cells then make thyroglobulin and secrete it into the colloid > in colloid, thyroglobulin is iodinated >epithelial cell uptakes iodinated thyroglobulin and digests it in lysosomes to generate T3 and T4 which are secreted into blood

Question 20

Structure of parathyroid gland

Answer 20

4-8 may be present, close to the thyroid. Contain Chief cells, oxyphil cells and adipose cells

Question 21

Function of chief cells in parathyroid

Answer 21

Produce parathyroid hormone which increases osteoclast release of calcium from bone and increases Ca uptake in GI tract and by kidney. Overall increases calcium levels

Question 22

Function of oxyphil cells

Answer 22

function is unknown but contain a number of mitochondria.

Question 23

Structure of adrenal gland

Answer 23

Contains an outer cortex and an inner medulla.

Question 24

function of adrenal gland

Answer 24

cortex produces steroids and medulla produces aa derived hormones

Question 25

Blood supply to adrenal gland

Answer 25

Blood is delivered via superior, middle and inferior suprarenal arteries which form an outer subcapsular arterial plexus. Blood then passes via a netowrk of capillaries in medulla. Blood drains into the central medullary vein then into the suprarenal vein

Question 26

structure of adrenal cortex

Answer 26

Contains an outer zona glomerulosa, middle zona fasciculata and inner zona reticularis. The cells are all high in lipid content due to lipid/steroid metabolism and they are arranged in vertical columns separated by capillaries that drain to the medulla. The mitochondria of the cells have tubular cristae characteristic of steroidogenic cells

Question 27

which zone contains the largest amount of stored lipid

Answer 27

zona fasciculata

Question 28

function of zona glomerulosa

Answer 28

Produces mineralcorticoids- aldosterone is main one. Controlled by angiotensin system

Question 29

funcion of zona fasciculata

Answer 29

produces glucocorticoids such as cortisol. Controlled by ACTH

Question 30

function of zona reticularis

Answer 30

produces androgens of modest potency. Controlled by ACTH

Question 31

Function of adrenal medulla

Answer 31

Produces epinephrine and norepinephrine.

Question 32

Structure of adrenal medulla

Answer 32

Cells are arranged as clusters around venous sinusoids that drain towards central medullary vein.

Question 33

What controls release of hromones from adrenal medulla

Answer 33

sympathetic and parasympathetic control

Question 34

function of pineal

Answer 34

production of seretonin, melatonin and peptides. Involved in gonadal regulation and circadian rhythms