endocrine histo Flashcards
water soluble vs fat hormones?
water - second messenger - eg growth hormone, FSH
lipid - enter cell - eg testosterone, estrogen
water soluble
cell needs receptor - hormone binds, 2nd messenger creates effect
lipid -
enters cell - creates change via nucleas
6 endocrine organs
pituitary adrenals endocrine pancreas thyroid parathyoids pineal
endocrine tissues - 3 tissue types
A - gland is separate entity - eg thyroid
B - scattered mass within exocrine gland - eg leydig in testis, langerhands
c - isolated in another system - eg gastrin cells in pyloris
pituitary
spennoid, turkish saddle - two distinct embyological tissues
adenohypophysis GLAND anterior
neurohypophysis (posterior) NEURAL
anterior - adenohypophysis
3 parts - pars distalis (anterior lobe) main part
pars tuberalis envelopes stem - together making pituitary stalk
pars intermedia - separating anterior, posterior
neurohypophyis - 2 parts
pars nervosa
infundibulum (funnel shape in neck))
two parts - infundibular process and median eminence (funnel)
embryology
anterior comes from below - they meet and bind - anterior form most of the neck
anterior - pouch of Rathke - ECTODERM ORAL cavity
posterior - neurohypophysis - downgrowth from diencephalon - connecting stem reamins as core of infundibular stem or stalk
blood supply - superior hypophysial artery
- from internal carotid - forms first sinusoidal capillary plexus (primary cap plexus) - receives secreteion of neuroendocrine cells of hypothalamus
- caps from primary cap plexus project down - into infundibulum
and pars tuberalis to form portal veins
caps from portal veins form secondary capillary plexus - supplying anterior hypophysis - and received secretions from endocrine cells of anterior hypophysis
is there a direct arterial blood supply to anterior?hypo?
no
portal system allows?
- trasnport of hormones (releasing and inhibiting) from primary cap to hormone producing cells of anterior hyp
- secretions of hormones from anterio hypo into secondary cap plexus and general circulation
- functional integrations of hypo with anterior hypo -
3rd cap plexus?
inferior hypo artery - branch of cavernous carotid art.
from inferior hypophysial arter - supplies nuerohypophysis - collects secretions from neuroendocrine cells - vASO PRESSIN and OXYTOCIN are transported along axons into neruohypo
are superior and inferior arteries connected?
yes, via trabecular artery - this bypasse portal system
pars distalis vs pars nervosa
nervosa is the nervous part - posterior - vasopressin - ANTI dieuretic and oxytocin vs ANTERIOR distalis
pars distalis (anterior) - 3 components
cords of epith cells
CT stronma
fenestrated caps (or sinusoids) which are part of secondary cap plexus
is there a blood-brain barrier in anterio hypo?
no
epith cells are in cords around fenestrated caps carrying blood from hypothalamus. Secretory hormones difffuse into network of capillaries - which drin into hypo veins and from there into venous sinuses
anterior hype - 3 types of cells
acidophils (pink) sides of gland
baso - darker - middle
chromophobes - cells lack staining - have depleted their hormone content losing staining affinity
acidophils secrete 2 things?
growth hormone and prolactin
GROWTH HORMONE (long bones via somatomedins in liver) aka somatotropes - and PROLACTIN (milk secretion, mammary size aka lactotropes or mammotropes
basophiles - B FLAT
FSH, LH, ACTH, TSH
B Flat
FSH, LH
ACTH - corticotropes - secretion of adrenal cortex hormones
TSH - Thyroid - thyrotopin - stim thyroid hormone synthesis - storage and liberation - T3, T4
feedback mechanism between pars distalis and thyroid
pars distalies TSH
thyroid creates T3, and T4 - goes to target tissues AND can give negative feedback to pars distalis and/or hypthalamus
what does hypothalamus send to pars distalis to stim TSH in pars?
TRH
The median eminence
is the structure where secretions of the hypothalamus (releasing and inhibiting regulatory hormones, known as “hypophysiotropic hormones”) collect before entering the portal system emptying into the general circulation.
Where is the median eminence?
The median eminence is the structure at the base of the hypothalamus where hypothalamic-releasing and –inhibiting hormones converge onto the portal capillary system that vascularizes the anterior pituitary gland.
pars tuberalis - funnel posterior stalk
secretes gonadotropins FSH and LH or ACTH - arranged in CORDS along blood vessels
pars intermedia - betw two
melanocyte stimulating hormone may be produced here - also in basophils of pars distalis
Growth hormone ? from acidophils?
Gigantism -
adenoma - benign tumor formed from glandular structures in epithelial tissue.
acidophil generates growth hormone that goes to liver
liver generates IGF1 - which grows long bones
induces growth thru insulin-like growth factor IGF1 prodcudes by hepatocytes
GHRH stis release of growth hormone from acidophils
Somatostatin and high blood gluce inhibit release of growth hormone
IGF 2 stims growth of long bones by stim hypertorphy of chondrocytes at epiphyseal plates
excess growth hormone - gigantism in kids, acromegaly in adults -
usually adenoma of anterior hypo is responsbiel for growth hormone hypersecretion
What stimulates prolactin secretion?
suckling - DOPAMINE is main inhibitor
T3 vs T4 lots MORE T4 - but T3 is much stronger - briefer half life
Circulating levels of T4 are much greater than T3 levels, but T3 is biologically the most metabolically active hormone (3-4 times more potent than T4) although its effect is briefer due to its shorter half-life compared to T4.
T3 more active, and has negative feedback on TSH
ACTH - cortisol - supradrenals
controls two zomes of adrenal cortex -
zona fasciculata and zona reticularis
zona globerulos is regulated by ANGIOTENIS II dervied from liver and renin and lungs -
ACTH stims
synthesis or cortisol - low levels of cortisol in blood, stress, and vasopressin (antidiuretic hormone ADH stim ACTH secretion from basolphils by stim relesae via postitive feedback
ACTH increase pigmentation in skin - darkened skin in ADDison’s and Cushings is not detemrined by melanocyte stim hormone MSH - which is not normally present in human serum
neurohypo - posterior - c3 components
looks like ADH and oxytocin may be made in hypothalamus and brought on axons to posterior pituitary where they are further transported via cap plexus onward -
- pituicytes - resembling astrocytes - structure to axons - surround axons, and retract to enable release into blood of secretory granules stored in axon terminals
- unmyelinated axons - from supraoptic and paraventricular nuclei of hypothalamus
axons bulge HERRING BODIES contain secreotry products
supraoptic produce mainly ADH and paraventricular primarily oxytocyn
- Fenestrated caps are derived from inferior hypophysial artery
where is ADH made? this is VASOpressin - antidiuretic -
ADH is a hormone that is produced in a part of the brain called the hypothalamus. It is then stored and released from the pituitary, a small gland at the base of the brain. ADH acts on the kidneys to control the amount of water excreted in the urine
Where is oxytocin produced?
What is oxytocin? Oxytocin is produced in the hypothalamus and is secreted into the bloodstream by the posterior pituitary gland. Secretion depends on electrical activity of neurons in the hypothalamus – it is released into the blood when these cells are excited.
What does vasopressin do? Raises BP
AVP has two principle sites of action: the kidney and blood vessels. The primary function of AVP in the body is to regulate extracellular fluid volume by regulating renal handling of water, although it is also a vasoconstrictor and pressor agent (hence, the name “vasopressin”).
What stimulates the release of vasopressin?
The main physiological stimulus to vasopressin secretion is rising plasma osmolality, though significant reductions in arterial blood pressure and blood volume can also stimulate vasopressin secretion, by unloading of arterial baroreceptors.
IF not enough ADH - disease - Nuerogenic Diabetes Insipidus
aos occurs in some renal diseases or genetic defects
can excrete up to 2O liters of urine in 24 hours - head injury or invasive tumor damaging hypothalamic hypophysial system
pituitary disorders
most common - pituitary adenoma - benign tumor because do not invade adjacent tissue - however they cause damage and may kill
excessive continuous productino of a hormone or uncontrolled feedback mechanism
Cushings Disease?
tumor causing excess ACTH secretion
Giantism -
tumors of somatotrophs causing excess growth hormone - acromegaly in adults
some tumors produce no hormones but grow upwards out of sella turcica compressing
optic chiasma and nerve - vision disturbance and ~blindness
rare cases where pituitary blood supply is cut off
disease blocks arterieal supply - pituitary cells necrose - and no hormones produced
Adrenal glands
capsule - yellowish outer cortex 85% of gland, reddish inner medulla
cortex vs medulla
can be considered two organs - arise from diff germ layers
cortex mesodern
medulla neural crest that migrate into developing gland
cortex similar to gonads - secretes variety of steroid hormones - all related to their common precursor - cholestterol
adrenal medulla - similar to sympathetic nervous system
produces catecholamines - NE EP
blood supply to adrensas - a LOT
tall drainage system - from top to bottom -
superior, middle and inferior suprarenal arteries -
supplying to capsule, cortical, medulla
medulla - dual blood supply?
arterial blood from medullary arteries and venous blood from cotical capillaries -
venules that aris fromthese drian in adrenomedullary collecting veins -
no veins or lymphatics in adrenal cortex
blood supply ?
arteries supply capsula - then drain to cortical
cortical also has supply and then drain into fenestrated medullary caps
meduallary - has arteries from corte that transverse but arrive directly in medulla and venous blood arriving from cotical capillaries - hence dual blood supply
cells of adrenal cortex secrete steroids?
do not store their secretions - they synthesize and secrete on demand - they can diffuse through plamsa membrane - and do not require exocytosis