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
adrenal cortex - 3 zones
zona glomerulosa 15%
middle zona fasciculata 80%
innermost zona reticularis 5%
zona glomerulus - ALDOSTERONE
lacks 17
controls blood pressure - mineralocorticoid –Angiotensin II stimulated growth of zona glomerulosa and synthesis of aldosterone
it lacks enzyme 17 a hydroxylase and therefore, can’t produce corticsol or sex steriods
zona fasciculata
has 17 -
can’t produce aldosterone but have the 17 necess for glucocorticoids-cortisol and enzyme 17, s0-hydroxylase required for sex hormones
cuboidal cells - steroid producing cells arranged in longitudinal cords separated by fenestrated caps
3 components
- cholesterol is stored in a lipid droplets - foamy appaerance - called spongiocytes
- mitochondria w/ tubular cristae w/ steroidogenic enzymes
- smooth ER
aldosterone?
mainly acts on distal renal tubules, gastric mucosa, colon and salivary /sweat gladns stimulating REABSORP of sodium
glucocorticoids?
affect metabolsim of carbs - stim both production of glucose from amino acids or fatty acids (gouconeogenesis) and conversion of glucose into glycogen
cortisol - may decrease uptake of glucose by cells
affects skin, muscle, etc
also suppresses immune response by destroying circulating lymphotcytes - inhibiting mitotic activity in lymph forming organs,
DHEA?
secreted by adrenal cortex
Your body naturally produces the hormone dehydroepiandrosterone (DHEA) in the adrenal gland. In turn, DHEA helps produce other hormones, including testosterone and estrogen. Natural DHEA levels peak in early adulthood and then slowly fall as you age.
What does ACTH hormone do?
This test measures the level of adrenocorticotropic hormone (ACTH) in the blood. ACTH is a hormone made by the pituitary gland, a small gland at the base of the brain. ACTH controls the production of another hormone called cortisol.
synthesizing steroid hormones? difficult process
starts with pregenoclone
then progesterone - whichis precursor or all other steroid hormones
then testosteron
then estradiol
what part of adrenal cortex can NOT make cortiosl or sex hormones? lacking 17
glomerulosa
patients taking corticoids for long periods
should NOT stop taking suddently - ACTH is inhibited - will cause severe imbalance in sodium and potassium
disorders of adrenal cortex?
hypoadrenalism - addisons
hyPERadrenalism
lack of total function (via tuberculosis, autoimmune disorder) ADDISON’s Disease
HYPER - Cushing (gluco)
Conn’s (mineralcorticoids - aldosterone)
tumors in adrenals?
benign or malignant - exces hormones can be produced - such as hirsutism
Hirsutism
is a condition in women that results in excessive growth of dark or coarse hair in a male-like pattern — face, chest and back. With hirsutism, extra hair growth often arises from excess male hormones (androgens), primarily testosterone
adrenal medulla -
modified sympathetic post ganglionic neurons that have lost their axons and dendrites
arranged in cords or clumps
neural crest cells - (as do postganglionic neurons of sympathetic and parasympathetic )
chromaffin cells
brown color - cytoplasm has granules that contain either NE or EP - some contain both
minimal secrdtion of dopamine too
NE EP secreted into?
blood (unlike into a synapse as in postganglionic terminals - )
80% EP
20% NE
adrenal medulla innervated by?
sympathetic - ACH
what else can signal EP synthesis
high levels of cortisol
Pancreas endocrine 2%
islets of langerhans - a lot in tail
in small groups
more than 1 millions ilsets
capsulw of reticular fibers surround each islet
ilsetls arranged in cords separated by network of blood caps
4 types of cells?
B in core
others in mantle
A - glucagon 20%
B - insulin 70% in CORE of islet
D - somatostatin
F - rare ? unk
has two networks - local and systemic
venules leaving isets supply blood to adjacacent pancreatic acini (LOCAL action on exocrine pancreas)
insulin?
causes entry of glucose into cells promotes decrease in blood glucose content
glucagon (A cells)
makes energy stored in glycogen and fat availabe - increases blood glucose content
What is the target organ of somatostatin?
Specifically, somatostatin affects the pituitary gland in that it causes inhibition of secretion of growth hormone which is vital to cells in growth and metabolism. In the pancreas, somatostatin inhibits the secretion of insulin and glucagon which play an important role in glucose regulation in the body.
disorders of endocrine pancreas - insulin - diabetes - two types
type 1 - childhood loss of cells in islets - autoimmune response? THUS insulin deficiency
type 2 - adult - resistance of target cells to insulin
tumors in islets?
rare - can cause excessive secretion of one of hormones - so get hyperinsulinism, hypoglycemic, etc
how is type 1 caused - genearlly in childhood?
NO insulin - B cells destroyed -
autoimmunity, viral inf, chmical toxisn
type 2 - gentic predispo - asso with obesity
insufficient insulin secretin relative to glucose levels - defective secretion and action -
some target cells have insulin resistance -
diabetes complications?
many -
vascular atherosclerosis, arteriolosclerosis
gangrene
retinal probms - cataracts, glaucoma
glomerulosclerosis
heart attatched
stroke
thyroid - butterfly - two lobes, isthmus
two pairs of parthyroid on posterior
two types hormones from thyroid
iodine containing - T3 and T4
Calcitonin
thyroid functional unit?
each lobe many follicles
follicle - w/ central lumen - COLLOID substance rich in thyroglobulin
thyroid capsule and parathyroid separated by?
septum
C cells - neural crest cells - PALE cytoplasm
granules of calcitonin
between follicles full of colloid surrounded by epith?
in CT stroma there are blood vessels
cells change shape when active
resting low cuboidal or squamous
columnar when active
storage capacity of thyroid?
different than other organs that have limited storage capacity - prodcution of thyroid hormones depends on follicular storage of thyroglobulin in colloid
can CONCENTRATE iodide from blood and synthesize hormones thyroxine and triiodothyronine
two phases of hormone secretion
made and then secreted
exocrine - uptake of IODIDE (ATP driven pump) - synthesize THYROGLOBULIN - goes into colloid
endocrine - taken out of colloid, brought back into cell, mix with lysosome, and released as T3 and T4
both regulated by TSH
t3 is shorter half life (18 hours) vs T4 - 4 - 5 days
is MORE potent and less abundant than T4
T4 90%
T3 and T4?
exocrine phase - uptake iodid from blood, synthesize thyroglobuline, transport PENDRIN and thyroid peroxidase
Endocrine phase - endocytosis of colloid from lumen - droplets to lysosome - degrate to T3, and T4
released via fenestratated caps to blood
The thyroid gland releases triiodothyronine (T3) and thyroxine (T4). These hormones play an important role in regulation of your weight, energy levels, internal temperature, skin, hair, nail growth, and more.
What does thyroid hormone do?
simple answer: increase growth and metabolism - “change food into energy.”
more detailed - stimulate mitochondrial protein synthesis, increase absorption of cabs, regulate fat metabolim, promote cell growth
REVS up most bodily funtions -
increases heart rate, rasies body temp, increase nervous reactivity, GI motility
Parafollicular cells
Also called C cells, are neuroendocrine cells in the thyroid. The primary function of these cells is to secrete calcitonin. They are located adjacent to the thyroid follicles and reside in the connective tissue. These cells are large and have a pale stain compared with the follicular cells.
in small clumps,
pale large
Neural Crest
colloid of Thyroid?
colloid that contains the prohormone thyroglobulin. The follicular cells contain the enzymes needed to synthesize thyroglobulin, as well as the enzymes needed to release thyroid hormone from thyroglobulin
Colloid
can concentrate Iodine
What is follicular colloid?
The follicles are made up of a central cavity filled with a sticky fluid called colloid. Surrounded by a wall of epithelial follicle cells, the colloid is the center of thyroid hormone production, and that production is dependent on the hormones’ essential and unique component: iodine.
Pendrin?
is an ion exchanger found in many types of cells in the body. … In the thyroid, pendrin mediates a component of the efflux of iodide across the apical membrane of the thyrocyte, which is critical for the formation of thyroid hormone.
Disorders of Thyroid?
- tumor nodule - excessive synthesis T3, T4 w/o inactive storage phase (nodular hyperplasia)
Graves type 2 HYPERSENSITIVITY
both patterns cause “thyrotoxicosis” - goiter (enlarged thyroid), bulging eyes, tachycardia, warm skin, fine finger tremors
Graves - eyes bulge
autoimmune disorder that causes hyperthyroidism, or overactive thyroid. With this disease, your immune system attacks the thyroid and causes it to make more thyroid hormone than your body needs
Hyperthyroidism causes your metabolism to speed up.
plasma cells from sensitized T cells bind to TSH receptors and mimic effect of TSH
colloid is depleted
hyper thyrodism?
excessive production of thyroxine
Thyroxine is the main hormone secreted into the bloodstream by the thyroid gland. It is the inactive form and most of it is converted to an active form called triiodothyronine by organs such as the liver and kidneys
Is thyroxine a t3 or t4?
The major thyroid hormone secreted by the thyroid gland is thyroxine, also called T4 because it contains four iodine atoms. To exert its effects, T4 is converted to triiodothyronine (T3) by the removal of an iodine atom. This occurs mainly in the liver and in certain tissues where T3 acts, such as in the brain
hypothyroidism?
decreased metabolic rate - hypothermia, cold intolerance - decreased sweating, cutaneous vasoconstriction makes skin dry and cool - cardiac output reduced - pulse slows - can correct this
fetus - lack of thyroid hormone?
you NEED iodine - that’s why they put it in salt
cretinism - see in iodine deficient geographical areas -
resp distress, poor feeding, umbilical hernia, retarded bone growth - - untreated can lead to mental retardation
Hashimoto disease?
autoimmune = hypothyroidism - autoantibodies target thyroid peroxidate and thyroglobulin - progressive destruction of thyroid follicles leads to decrease in thyroid function
Parathyroid glands?
two pairs - posterior of thyroid -
lower ones start up higher and migrate down
arranged in cords - two cells populations -
Chief, PTH always secreting UNLESS too much serum, which binds to receptor and stop secretion
Oxyphil
Chief or Principal cells - granules with parathyroid hormone -
glycogen inclusions seen also
Ca2+ sensing receptors are on membrane -
Serum Ca2+ binding triggers suppressing secretion of PTH -
when serum decreases - secretion of PTH starts up again - increasing serum
osyphil - or acidophilic cells - lots of mitochondria - may be?
transitional chief cell
do not secrete PTH - increase in number w/ age
what does PTH do?
secreted into blood, half life of 5 minutes
activates production of active Vitamin D
PTH raises calcium levels by releasing calcium from your bones and increasing the amount of calcium absorbed from your small intestine. When blood-calcium levels are too high, the parathyroid glands produce less PTH . But sometimes one or more of these glands produce too much hormone.
Does PTH bind to osteoblasts or clasts?
BLASTS - activates RaNK to osteoclasts - - more bone resorption - calcium goes UP
Vitamin D and parathyroid?
kidney
uriniferous tubules - kidneys stimulates resorption of CA2_ and activates production of active Vitamin D
PTH acts in two main places?
bone tissue
kidney -
when calcitonin binds to Osteoclasts what magic happens?
RUFFLED border disappears
If calcium serum high?
thyroid generates calcitonin - message to BONE and INTESTINE
at intestine - say stop aborbing
If Cal low?
messages go out to parathyroid and kidney -
parathyroid talks to kidney and bone -
kidney “stop reaborobing”
bone “stop reabsorbgin:
message direct to kidney via 1.25 OH x - talks to bone and Intestine - “stop absorbing”
Disorders of parathyroid?
can over or under work -
common - over production of PTH - unresponsive to feedback telling it to stop - too much bone reaborption - hypercalcemia - osteo fibrosa cystica
bone pain - increased risk of kidney stones
“primary hyperparathyroidism”
“second hyperparathyroidism”
patients w/ kidney failure - persistent low serum calcium levels - constantly losing calcium in urine
parathyroid become enlarged - secreting excess parathormone to try to get serum calcium levels back to normal
hypoparathyroidism?
rare - usually if accidentally removed during surgery - w/in 24 hours - attacks of tetany or epilepsy occure - giving PTH hormone cures problem
Pineal gland
midline of brain - - evagination of posterior part of roof of 3rd ventricle
formed by cells w/ neurosecretory function
connected to brain via STALK - no direct nerve connections - post-ganglionic sympathetic from superior cervical ganglia supply
regulated by sympathetic nerves -
pineal - covered by ?
Pine Cone
melatonin secreting
pia mater - irregular lobules are formed - cellular cords and follicles - unmyelinated nerve fibers originate in pia and penetrate pineal tissue, along with blood vessels
pineal glands have?
calcium deposits - “corpora arenacea” brain sand - foudn in extracellular space
two cell types in pineal glands
pinealocytes
glial-like interstitial cells (astrocytes)
pinealocytes secrete?
gap junctions link adjacent pinealocytes
“ribbon synapse”
organized in cords and clusters resting on basal lamina - surrounded by CT - two or more cell processes - ending in bulbous expansion - lots of mitochondria
does pineal or anterior hypophysis have a blood-brain barrier?
No, neither -
what regulates pinealocytes?
beta adrenergic receptors -
calcification starts in early childhood - no known effect - serves as radiographic marker in brain
what does pineal gland secrete?
Melatonin - hormone of darkness
synthesis highest in complete darkness
induces sleepiness, inhibits gonadotropin and growth hormone secretions
tumors of pineal gland?
precocious puberty
androgen secretion and spermatogeneisis at boys before 9 - 10
probably caused by tumor’s effect on hypothalamus rather than direct effect of pineal tumors on sexual funciton
What makes androgens?
Androgens are synthesized from cholesterol and are produced primarily in the gonads (testicles and ovaries) and also in the adrenal glands. The testicles produce a much higher quantity than the ovaries. Conversion of testosterone to the more potent DHT occurs the prostate gland, liver, brain and skin.
The median eminence of nervosa posterior hypo?
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.
Rathke’s pouch
is an evagination at the roof of the developing mouth in front of the buccopharyngeal membrane. It gives rise to the anterior pituitary (adenohypophysis), a part of the endocrine system.
skull bones?
ectoderm - NCC
gumernaculum
a part or structure that serves as a guide especially : a fibrous cord that connects the fetal testis with the bottom of the scrotum and by failing to elongate in proportion to the rest of the fetus causes the descent of the testis.
uterus and ovaries are derivatives of gubernaculum?
