T1: Anatomy, Development, Histology of Endocrine Gland

difference between exocrine & endocrine glands (give their def)

exocrine glands = pour their products onto epithelial surface directly or thru ducts or tubes

endocrine glands = no ducts or tubes, secrete their products into CT → enter bloodstream to reach target cells

product of endocrine glands is called

hormones

development of glands: exocrine gland

1. exocrine gland develops as a …. from ….. into ……

2. soon it …. , undergoes …… & displays …… & …….

3. …… part forms …… & is …… with epithelium

1. exocrine gland develops as a solid bud from epithelium into underlying CT

2. soon it elongates, undergoes canalisation & displays secretory & conducting portion

3. conducting part forms duct & is continuous with epithelium

development of glands: endocrine gland

1. how does it development differ from exocrine gland

2. it appears as a ……. → then becomes …… by ……

1. initially develops in a similar manner: solid bud from epithelium into underlying CT but w/ further development → it breaks continuity with overlying epithelium

2. appears as a clump of cells → then this clump of cells gets surrounded by blood vessels → secretion of endocrine glands gets poured into these blood vessels

name the 4 types of hormones

1. amino acid acid derivatives

2. small peptides

3. proteins

4. steroids

give 3 examples of AA derivatives

epinephrine, norepinephrine, thyroxine

give 2 examples of small peptides

vasopressin (ADH), thyroid releasing hormone (TRH)

give 2 examples of protein hormones

insulin, thyroid stimulating hormone (TSH)

give 4 examples of steroid hormones

progesterone, estrogen, testosterone, cortisol

pituitary gland other name

hypophysis

pituitary gland location

lies below ….. on ….. bone

lies below brain in a small cavity on sphenoid bone

pituitary gland located between which sinus

cavernous sinus

pituitary gland function

1. produces & secretes hormones itself + cause hormones in hypothalamus to be release → to target organs

2. master gland of endocrine system

name the 2 main divisions of pituitary gland & state its other name

1. anterior pituitary = adenohypophysis

2. posterior pituitary = neurohypophysis

adenohypophysis & neurohypophysis derived from what

adenohypophysis = oral ectoderm

neurohypophysis = neural ectoderm

name the 3 subdivisions of adenohypophysis/ant. pituitary

1. pars distalis (anterior lobe)

2. pars tuberalis

3. pars intermedia (intermediate lobe)

name the 3 subdivisions of neurohypophysis

1. pars nervosa (posterior lobe)

2. infundibular stalk

3. median eminence

*median eminence + infudibular stalk = infundibulum

development of pituitary gland

1. ant PG:

   • derived from what

   • another name for this developmental structure

   • developmental process

   • final fate

1. ant. pituitary is derived from evagination of oral ectoderm towards brain → called ‘rathke’s pouch’

2. final fate = rathke’s pounch pinches off/ connecting stem attached to rathke’s pouch dissapears

3. rathke’s pouch develops into 3 regions:

   • ant. surface = pars distalis

   • post. surface = pars intermedia

   • superior extension = pars tuberalis

development of pituitary gland

1. post. PG:

   • derived from what

   • developmental process

   • final fate

• derived from neuroectoderm of diencephalon

• developmental process: downward extension of neuroectoderm from floor of 3rd ventricle in brain → when connecting stem attached to rathke’s pouch disappears, connecting stem of neurohypophysis still remains → becomes post. pituitary

adenohypophysis made of what epithelium

glandular epithelium

describe appearance of pars tuberalis

thin collar of tissue surrounding infundibular stalk

histology of pars distalis (ant. lobe)

name the 3 components of pars distalis

1. glandular epithelial cells (endocrine cells) → cells yuu chid2 gun/เรียงกัน = forms cord

2. fenestrated capillaries (or sinusoids)

3. supporting reticular CT

2 major types of glandular epithelial cells (endocrine cells)

1. chromophils → acidophils & basophils

2. chromophobes

what are chromophils, state the 2 types of chromophils - where is each type prevalent, percentage of each type, stains w what

chromophil =

• parenchymal cells that stain intensely bcuz of their hormone-containing secretory granules

• synthesize store n release several hormones

(parenchymal cells = functional cells of organ/tissue, performs specific tasks that define organ’s role)

2 types:

1. acidophils = 40% → prevalent at sides of gland

   • stain w/ acidic dye

2. basophils = 10% → predominant in middle of gland

   • stain w/ basic dye

chromophobes are (in terms of hormone content & affinity)

cells that have depleted their hormone content & lost staining affinity

describe appearance of basophils, acidophils, chromophobes on H&E stain

basophil = blue-purple due to glycoproteins in cytoplasm

acidophil = light pink

chromophobe = very light pink cytoplasm, almost looks clear

name the 2 types of acidophils

1. somatotrophs

2. mammotrophs/lactotrophs

somatotrophs

1. releases what hormone

2. function of that hormone (2)

1. release somatotropin or growth hormone

2. function =

   • increases metabolism in most cells

   • indirectly stimulates epiphyseal plate, growth of long bones

lactotrophs/mammotrophs

1. releases what hormone

2. function of that hormone (2)

1. releases prolactin

2. function: development of mammary gland during pregnancy, milk synthesis during lactation

name the 3 types of basophils

1. corticotrophs

2. gonadotrophs

3. thyrotrophs

corticotrophs

1. releases what hormone, state hormone’s by-products (3)

2. function of hormone’s by-products

1. releases POMC (pre-hormone polypeptide) → by-products: ACTH, MSH, lipotropin

2. • ACTH = stimulates glucocorticoid secretion by zona fasciculata cells of adrenal cortex

   • MSH = stimulates melanocytes to produce melanin

   • lipotropin = also stimulates melanocytes to produce melanin

what hormones do gonadotrophs secrete

FSH, LH

what hormone does thyrotroph secrete & state function

secretes TSH → stimulates synthesis & release of T3, T4 by follicular cells

1. which organ controls the release of hormones from pituitary gland (regulatory production)

2. what hormones does hypothalamus secrete

3. state name of neuron in hypothalamus that produces releasing & inhibiting hormones

1. hypothalamus

2. hypothalmus produces regulatory hormones: releasing & inhibiting hormones → controls production of hormones from ant. pituitary

3. neuron = hypothalamic hypophysiotropic nuclei

histology of pars intermedia

• name the 3 things it contains

1. colloid-containing cysts (rathke cysts) lined by cuboidal cells

2. basophils

3. chromophobes

pars intermedia

• what hormone does basophil secrete & what other hormones is it cleaved to form

prohormone POMC → cleaved to form ACTH, lipotropin, MSH

(same as corticoptrophs of pars distalis)

histology of pars tuberalis

• what cells is found here, these cells are located along what

cuboidal basophilic cells found here, cells are arranged in cords along capillary network

neurohypophysis (post. pituitary)

• name its 3 histologic components

  1. name & derived from where (hint: pen korng cell arai, where)

  2. name & appearance, function

  3. name & function

1. unmyelinated axons - korng neuroendocrine cells of hypothalamus (paraventricular & supraoptic nuclei)

2. pitiucytes - astrocyte-like glial cells → provides support to axons

3. fenestrated capillaries → permits diffusion of hormones into circulation

<neurohypophysis (post. pituitary)>

neuroendocrine cells (that extend their axons into post. pituitary) come from which types of nuclei (2) & where are these nuclei located

paraventricular nucleus & supraoptic nucleus

→ located in hypothalamus

paraventricular nucleus (PVN) produce what hormone

oxytocin

supraoptic nucleus produce what hormone

ADH

<neurohypophysis (post. pituitary)>

herring bodies are … seen at ….

contains ….

bulging intermittent segments/terminals of axons, seen at axon terminal or along the way of unmyelinated axons

contains secretory granules, neurophysin (carrier protein), associated hormones

<neurohypophysis (post. pituitary)>

pituicytes located where & function

• surrounds axons of neuroendocrine cells

• its axon contacts basal lamina of fenestrated capillaries → function = when pituicytes retract their processes → herring body discharges hormone into circulation

blood supply of pituitary gland

• name the 2 sets of vessels

superior hypophyseal arteries & inferior hypophyseal arteries

1. name the 3 structures the superior hypophyseal arteries supply (3)

2. where does the vessels arise from (2)

1. pars tuberalis

2. median eminence

3. infundibulum

• vessels arise from internal carotid arteries & post. communicating arteries (of circle of willis)

1. name the 3 structures the inferior hypophyseal arteries supply (1)

2. where does the vessels arise from (1)

1. primarily supplies pars nervosa

2. internal carotid arteries

what part of pituitary gland has no direct arterial supply

anterior lobe of adenohypophysis = pars distalis

hypothalamohypophyseal system is

an intergrated neuroendocrine network formed by hypothalamus & hypophysis (pituitary gland)

hypothalamic adenohypophyseal system connects the …. to …..

connects hypothalamus to ant. hypophysis

hypothalamic neurohypophyseal system connects … to …

hypothalamus to post. hypophysis

what does not have direct connection with hypothalamus

adenohypophysis → connects by veins only

explain pathway of how hormones are secreted into blood from the hypothalamic-hypophyseal tract

1. hormones ADH & oxytocin are synthesized in the supraoptic and paraventricular nuclei respectively

2. hormones are transported along the unmyelinated axons of the nuclei forming hypothalamic hypophyseal tract

3. hormones are released at axon terminals → enters fenestrated capillaries derived from inferior hypophyseal artery

explain pathway of how hormones are secreted into blood from the hypothalamic-adenohypophyseal system

superior hypophyseal artery enters median eminence & receives releasing & inhibitory hormones from hypothalamohypophysio-tropic nuclei → hormones are sent to primary capillary plexus in upper infundibulum → portal veins → these hormones enter secondary capillary plexus in pars distalis where another set of hormones are produced

clinical correlation

pituitary adenoma:

1. histologic cause =

2. adenomas involving ….. cells → cause <clinical feature> in children or <clinical feature> in adults

pituitary adenoma

• histologic cause = excessive numbers of functional acidophils & basophils

• if adenoma involves SOMATOTROPIC CELLS (produces growth hormones) → GIGANTISM in children (before closure of long bones’ epiphyseal plates) or ACROMEGALY in adults

what is giagantism

excessive linear growth → abnormally tall structure

what is acromegaly

enlargement of acral (distal extremities) plates & soft tissues → enlarged hands & feet

Pineal Gland/epiphysis appearance & location

small organ located inside brain

name the 2 types of cells found in pineal gland

pinealocytes & neuroglial cells

apart from pinealocytes & neuroglial cells, what else does pineal gland contain (characteristic feature)

brain sand or copora arenacea

state function of pineal gland

regulate the body’s circadian rhythm (sleep-wake cycle) by secreting the hormone melatonin

pineal gland develops from what

posterior diencephalic roof in midline of 3rd ventricle

state appearance of pinealocytes

secretory cells, round or ovoid nuclei w/ cytoplasm containing granules filled w/ melatonin

melatonin content is highest during …

nighttime with complete darkness

thryoid gland location & appearance

consists of 2 lobes, located below thyroid cartilage

how many parathyroid glands are there

4, 2 pairs of superior PTH gland & 2 pairs of inferior PTH gland

thyroid gland develops from where (which level, from where)

develops at the level of 1st & 2nd pharyngeal pouches as a median outgrowth from floor of pharynx

parathyroid gland develops from which level

3rd & 4th pharyngeal pouches

describe histology of thyroid gland

….. filled w/ …….

variable-sized follicles filled w/ acidophilic colloid

1 thyroid follicle consists of (2)

1. colloid

2. simple cuboidal epithelium of thyroid follicular cells or thyrocytes

which part of follicular cell is in contact w/ colloid

apical surface

state the 2 types of cells found in follicular epithelium

1. thyroid follicular cell (thyrocytes)

2. parafollicular cells (C cells)

function of thyroid follicular cells

contains vesicles at apical surface → involved in production, transport & release of thyroglobulin (precursor of thyroid hormone) & enzymes into colloid

difference btwn thyroid follicular cells located in active glands & hypoactive glands

active glands = more follicular cells of low columnar epithelium

hypoactive glands = mostly squamous follicular cells

parafollicular cells (C cells)

1. how does it differ from follicular cells in terms of appearance

2. derived from …

3. function

1. larger & paler than follicular cells

2. dervied from neural crest

3. produce calcitonin → decreases blood Ca2+

state the mechanism for synthesis & release of T3 & T4 follicular cells of thyroid gland

1. exocrine phase (4 steps)

2. endocrine phase (2 steps)

1. exocrine phase

   1. synthesis of thyroglobulin (precursor of thyroid hormone) (contains 140 tyrosyl residues)

   2. uptake of inorganic iodide from blood

   3. iodine is incorporated into tyrosyl residues of thyroglobulin → forms MIT (1 iodine) & DIT (2 iodines)

   4. MIT + DIT = pre-T3, DIT + DIT = pre-T4

      → pre-T3 & pre-T4 forms - still part of colloidal thyroglobulin

2. endocrine phase

   5. pre-T3 & pre-T4 is endocytose by thyrocytes & degraded by lysosomal proteins

   6. T3 & T4 (active form) is secreted into blood

TSH effect on T3 & T4 synthesis

1. stimulates uptake of inorganic iodide

2. endocytosis of iodinated thyroglobulin or pre-T3, pre-T4

T3 & T4 effect = (4)

1. increase basal metabolic rate

2. promotes cell growth

3. increase heart rate

4. raise body-temp

5. enhance energy-requiring cell functions

calcitonin function

lowers blood Ca2+ lvls

graves disease

• condition =

• cause =

• typical clinical feature (1) =

• condition = hyperthyroidism

• cause = excessive amounts of thyroid hormones secreted by follicular cells

• typical clinical feature (1) = exophthalmos (bulging of the eyes)

name the 2 types of cells found in parathyroid glands

1. chief cells

2. oxyphil cells

chief cell - function & appearance

• dominant cell type in parathyroid gland

• secretes large amounts of PTH

• hv large round nucleus w/ small cytoplasm

oxyphil cells - function & appearance

• do not secrete PTH!!!!!!!

• hv large amount of cytoplasm

• arranged in clusters, individual oxyphil cells can also be found scattered among chief cells

PTH function

increase blood Ca2+ lvl

hyperparathyroidism

• cause

• consequence

• what can be observed in blood test (1)

• overactivity of parathyroid glands → excess secretion of PTH

• consequence: bone resorption

• blood = high Ca2+

name the 2 parts of adrenal gland

1. cortex

2. medulla

adrenal cortex - derived from where & produces what hormone

derived from mesoderm

produces steroid hormones

adrenal medulla derived from where & produces what hormone

derived from neural crest cells, produces catecholamines

name the 3 zones of adrenal cortex & state percentage composition

1. outermost layer =

2. middle layer =

3. innermost layer =

1. outermost layer = zona glomerulosa (10-15%)

2. middle layer = zona fasciculata (75%)

3. innermost layer = zona reticularis (5-10%)

zona fasciculata histology

• what types of cells found there, describe cell arrangement

• name the special type of cells found there & describe it

• cuboidal cells, arranged in longitudinal cords seperated by fenestrated capillaries or sinusoids

• contain spongiocytes: lipid droplets, so vacuolated

adrenal cortex → produces steroid hormones

parenchymal cells of zona glomerulosa produce what hormone

mineralocorticoids: aldosterone

adrenal cortex → produces steroid hormones

parenchymal cells of zona fasciculata produce what hormone

glucocorticoids: corticosteroid & cortisol

adrenal cortex → produces steroid hormones

parenchymal cells of zona reticularis produce what hormone

gonadocorticoids: adrenal androgrens - DHEA

(induce development of axillary & pubic hair at puberty in women)

name the 2 types of cells found in adrenal medulla

1. chromaffin cells (or medullary cells)

2. sympathetic ganglion cells

chromaffin cells

• arise from what

• innervated by what

• neural crest cells

• innervated by preganglionic sympathetic fibres

function of chromaffin cells

synthesize, store & secrete catecholamines - epinephrine (80% of cells) & norepinephrine (20%)

epinephrine & norepinephrine function

stimulates glycogen breakdown → increase blood glucose lvl

fight or flight response

blood supply to adrenal glands - name the 3 arteries of adrenal gland

superior, middle, inferior adrenal artery

superior adrenal artery arise from which artery

inferior phrenic artery

middle adrenal artery arise from which artery

abdominal aorta

inferior adrenal artery arise from which artery

renal arteries