T1 histology of endocrine gland

exocrine glands

pour product onto epithelial surface or through ducts / tubes

endocrine glands

secrete products into connective tissue to enter blood stream

hormones

product of endocrine glands

exocrine gland - development

solid bud from epithelium into underlying connective tissue → secretory & conducting portion

endocrine gland - development

breaks continuity with overlying epithelium → group of cells surround by blood vessels

pituitary gland - location

sella turnica

sella turnica

bony cavity of sphenoid bone beneath the brain

pituitary gland - aka

master gland → controls function of several other endocrine glands

pituitary gland - division

anterior (adenohypophysis) & posterior (neurohypophysis)

anterior pituitary - embryological origin

oral ectoderm

rathke’s pouch

evagination from root of oropharynx of anterior pituitary

anterior pituitary - histology

darker stained → high number of hormone producing cells

anterior pituitary - main components

pars distalis, pars tuberalis, pars intermedia

pars distalis

anterior surface → largest & most important

paras tuberalis

superior extension → wraps around infundibulum

pars intermedia

posterior surface → thin layer between anterior and posterior pituitary

posterior pituitary - embryological origin

neuroectoderm

posterior pituitary - neuroectoderm

downgrowth from floor of third ventricle

posterior pituitary - histology

paler stained → made of nerve fibers & glial cells

posterior pituitary - connected to brain via

infundibulum

posterior pituitary - main components

pars nervosa, infundibular stalk, median eminence

pituitary gland - anterior lobe

pars distalis

pituitary gland - intermediate lobe

pars intermedia

pituitary gland - posterior lobe

pars nervosa

pars distalis - components

endocrine cells, fenestrated capillaries (sinusoids), supporting reticular connective tissue

pars distalis - cell types

acidophils, basophils, chromophobes

acidophils

pink stain, peripheral

basophils

purple/blue, central

chromophobes

pale/unstained

acidophilic cells

somatotrophs & mammotrophs (lactotrophs)

somatotrophs - hormone

somatotropin (growth hormone)

somatotropin - function

increase metabolism, growth of long bones

mammotrophs (lactotrophs) - hormone

prolactin

prolactin - function

milk synthesis, development of mammary gland

basophilic cells

corticotrophs, gonadotrophs, thyrotrophs

corticotrophs - hormones

POMC w byproduct: ACTH, MSH, lipotropin

MSH - function

manufacture melanin

gonadotrophs - hormones

FSH & LH

thyrotrophs - hormone

TSH

TSH - function

stimulate synthesis and release of T3 T4 by follicular cells

hypothalamic hypophysiotropic nuclei

release releasing and inhibiting hormones to act on anterior pituitary cells

pars intermedia - contains

colloid-filled cysts (rathke’s cyst), basophils, chromophobes

rathke’s cyst - epithelium

cuboidal

pars tuberalis - characteristics

highly vascularized

pars tuberalis - cell type

cuboidal basophilic cells

posterior pituitary - characteristics

not produce hormones → stores & release hormones made in hypothalamus

posterior pituitary - components

unmyelinated axons, pituicytes, fenestrated capillaries

posterior pituitary - unmyelinated axons - origin

neuroendocrine cells of paraventricular and supraoptic nuclei of hypothalamus

posterior pituitary - fenestrated capillaries

specialized blood vessels with small pores → efficient diffusion of hormones

posterior pituitary - pituicytes

glial cells

posterior pituitary - pituicytes - function

support axons of neuroendocrine cells, contact basal lamina of fenestrated capillaries, retract processes during hormone release from herring bodies

paraventricular nucleus - hormone

oxytocin

oxytocin - function

stimulate uterine smooth muscle contraction & milk ejection

supraoptic nucleus - hormone

ADH

ADH - function

increase water reabsorption in kidney collecting duct

herring bodies - what is it

bulging swellings along unmyelinated axons

herring bodies - contain

secretory granules filled with oxytocin / ADH & neurophysin

neurophysin

carrier protein that binds hormone during axonal transport

blood supply of pituitary gland

superior hypophyseal artery & inferior hypophyseal artery

superior hypophyseal artery - supply

pars tuberalis, median eminence, infundibulum

inferior hypophyseal artery - supply

pars nervosa

hypothalamic-adenohypophyseal system

connect hypothalamus to anterior pituitary

hypothalamic-adenohypophyseal system - deliver hormones

portal blood vessels

hypothalamic-neurohypophyseal system

connect hypothalamus to posterior pituitary

hypothalamic-neurohypophyseal system - deliver hormones

unmyelinated axons from hypothalamic nuclei

pituitary adenoma

produce excessive numbers of functional acidophils basophils, can cause gigantism

sheehan syndrome

necrosis of anterior pituitary gland due to sudden reduction in blood pressure in newborn

pineal gland - function

regulate circadian rhythm by producing melatonin

pineal gland - histological components

pinealocytes & interstitial cells

pinealocytes - function

secrete melatonin

pinealocytes - appearance

round oval nuclei, cytoplasm contains secretory granules

interstitial cells - appearance

dark staining, elongated nuclei

interstitial cells - function

stromal support to pinealocytes

brain sand / corpora arenacea

calcified deposits within pineal gland → gritty basophilic structures

isthmus

connects 2 lobes of thyroid gland

thyroid follicles - epithelium

simple cuboidal of thyroid follicular cells

colloid

acidophilic material rich in thyroglobulin inside thyroid follicle

thyroglobulin

precursor of thyroid hormone

thyroid follicular cells - active

low columnar

thyroid follicular cells - inactive

squamous

thyroid follicular cells - cytoplasm

contains apical vesicles → secretion of thyroglobulin

thyroid follicular cells - respond to

TSH from anterior pituitary

parafollicular cells (C cells) - location

between follicular cells but do not contact colloid

parafollicular cells (C cells) - appearance

large, pale staining

parafollicular cells (C cells) - contains

secretory granules with calcitonin

calcitonin - secrete when?

in response to high blood Ca2+

thyroid hormone synthesis - phases

exocrine & endocrine

thyroid hormone synthesis - exocrine

synthesis of thyroglobulin → iodide uptake → iodination of tyrosyl residues in thyroglobulin → formation of preT3 T4

thyroid hormone synthesis - endocrine

endocytosis of iodinated thyroglobulin into thyrocytes → proteolysis in lysosome release T3 T4 into bloodstream

TSH stimulates…

iodide uptake & endocytosis of colloid

effects of T3 T4

increase: basal metabolic rate, body temp, heart rate, growth & development, energy usage

calcitonin - function

lowers Ca2+ by inhibit osteoclast-mediated bone resorption

graves disease

hyperthyroidism

parathyroid glands - how many? & names

2, superior & inferior

parathyroid glands - cells

chief (principal) & oxyphil

chief (principal) cells - appearance

pale, slightly acidophilic cytoplasm, round nucleus, arranged in cords surrounded by fenestrated capillaries

chief (principal) cells - function

secrete PTH

PTH - function

increase blood Ca2+ by stimulating bone resorption, increase intestinal absorption and enhance renal reabsorption

oxyphil cells - appearance

large, acidophilic pink cytoplasm, small nucleus, scattered among chief cells