Test 2: Endocrine Lecture Flashcards
endocrine system definition
Ductless glands that produce hormones that regulate metabolism, growth, development, tissue function, reproduction, sleep, mood, etc.
Regulates homeostasis in collaboration with the nervous system
key features of endocrine system
–cells often arranged in clusters or cords
–release hormones into intercellular or perivascular connective tissue spaces
–associated with dense capillary beds and wide thin-walled vessels called sinusoids
endocrine system is associated with dense capillary beds and wide thin-walled vessels called ___
sinusoids- very leaky, large pores
single cells that have endocrine functions
neural crest cell
Stomach: G cells: gastrin
Small intestine: I cells: cholecystokinin and S cells: secretin
endocrine cell groups/clusters
Endocrine cell groups/clusters in “non-endocrine” organs
•hypothalamic neurosecretory neurons
-various, regulate pituitary function
•pancreatic islets
-insulin, glucagon, others
•atrial cardiac myocytes
-atrial natriuretic factor
•theca interna of ovarian follicles
-androgens, progesterone
•interstitial cells of testes (aka Leydig cells)
-testosterone
hypothalamic neurosecretory neurons
endocrine cell group
that regulates pituitary function
pancreatic islet cells make what?
insulin, glucagon and others
type of endocrine cell group/cluster
atrial cardiac myocytes produce what
atrial natriuretic factor
type of endocrine cell group/cluster found in a non endocrine organ
theca interna of ovarian follicle produce what
androgens, progesterone
type of endocrine cell groups/clusters in “non-endocrine” organs
Leydig cells produce what
testosterone in the testes
type of endocrine cell groups/clusters in “non-endocrine” organs
types of endocrine organs
Hypophysis (pituitary)
Thyroid gland
Parathyroid gland
Adrenal glands
Pineal gland (not covered)
what is a common feature of endocrine organs
all have dense capillary beds and wide thin-walled vessels called sinusoids
another name for pituitary gland
hypophysis
two parts of pituitary gland
Adenohypophysis –anterior pituitary–glandular portion
Neurohypophysis –posterior pituitary- where secretion of things made in the hypothalamus
There is an intimate neural and vascular relationship between the hypothalamus and ___
hypophysis/ pituitary gland
Pituitary functions are tightly controlled by the ___
hypothalamus
__ is the anterior glandular portion of the hypophysis
Adenohypophysis
___ is the posterior part of the hypophysis where hormones made by the hypothalamus are secreted
Neurohypophysis
development of the hypophysis
___ is a funnel like structure that is residual from the formation of the pituitary gland and is found in the ___
infundibular recess
neurohypophysis (posterior part)
___ is a small residual lumen in the ___ part of the pituitary that acts as a landmark
residual lumen of rathke’s pouch
adenohypophysis (anterior part)
Three parts of the Adenohypophysis
pars distalis
pars intermedia (cells that secrete melanocyte stimulating hormone)
pars tuberalis (collar of the stock- portal venules go through here)
Three parts of the neurohypopysis
pars nervosa (infundibular process)
infundibular stalk
median eminence (where primary capillary reside)
Pars distalis
anterior lobe, major part of the adenohypophysis
dense fibrous capsule of collagenous tissue w/ stromal fibers
–parenchyma organized as cords and clusters of cells- polarized make hormones go in one direction
–closely associated with a dense network of sinusoidal capillaries
Cells of the pars distalis
Chromophobes- do not stain well
Chromophils- stain well and can be Acidophils or Basophils
Cells are classified by their staining properties but can also be immunochemically distinguished based on the hormones they produce.
Chromophobes
50% cells of pars distalis which is part of the adenohypophysis
–small round cells w/ very little cytoplasm and no detectable granules (do not stain well) (by light microscopy)
–usually present in clusters and may form the centers of cell cords
–may be degranulated chromophils or chromophil precursors
Chromophils
type of cell in the pars distalis which is part of the pituitary/adenohypophysis
−contain secretory granules
larger then chromophobes
−arranged in cords or clusters of cells
−polarize toward sinusoidal capillaries (apical secretion)
basophilic 10% (purple) or acidophilic 40%(orange)
types of acidophils
–Acidophils (~40%)
Somatotropes
Lactotropes (mammotropes)
Chromophils type of cell of the pars distalis which is part of the adenohypophysis
types of hormone basophils
Basophils (~10%)
Thyrotropes, Gonadotropes, Corticotropes
Chromophils type of cell of the pars distalis which is part of the adenohypophysis
somatotropes produce ___ and lactotropes produce __. These are __ types of cells
somatotropin (STH)= growth hormones (GH)
prolactin
Acidophil Chromophils cell of the pars distalis
Thyrotropes produce ___ , gonadotropes produce ___ and corticotropes produce ___. These are ___ types of cells from the ___
Thyrotropin- thyroid stimulating hormone (TSH)
gonadotropin= follicle stimulating hormone (FSH) luteinizing hormone (LH) or interstitial cell stimulating hormone (ICSH)
corticotropin- adrenocorticotropin ACTH
Basophils Chromophils cell of the pars distalis
Acidophils of the Pars Distalis are ___ than chromophobes. Contain granular ___cytoplasm and are often___.
larger
acidophilic
polarized
Somatotropes produce
–somatotropin (STH; aka growth hormone, GH)
type of acidophil chromophils of the pars distalis
Lactotropes (mammotropes) produce ___
prolactin (PRL)
type of acidophil chromophils of the pars distalis
Basophils of the Pars Distalis have granular ___ cytoplasm. Contain numerous ___ granules and are often ___
basophilic
PAS-positive
polarized
Thyrotropes produced ___
Thyrotropin (TSH)
type of basophil chromophils of the pars distalis
Gonadotropes produce ___
follicle-stimulating hormone (FSH)
luteinizing hormone (LH); also called interstitial cell-stimulating hormone (ICSH)
type of basophil chromophils of the pars distalis
corticotropes produce ___
adrenocorticotropin (ACTH)
most common basophil
type of basophil chromophils of the pars distalis
POMC (proopiomelanocortin) is a precursor for ___
adrenocorticotropin (ACTH)
melanocyte stimulating hormone (MSH)
b-lipotropic hormone (b-LPH)
b-endorphin
Melanotropes reside in the ___
pars intermedia
pars distalis
Note:
cell clusters and cords
sinusoids- big gaps orange dots inside are red blood cells
chromophobes
acidophils (orange)- cluster/group together
basophils (purple)
pars distalis of the adenohypophysis of the hypophyseal
orange cells= acidophils= chromophils
purple= basophils= chromophils
clear/ no stain uptake= chromophobes
pars distalis of the adenohypophysis of the hypophyseal
very pink= acidophils= chromophils
purple/pink= basophils= chromophils
clear/ no stain uptake= chromophobes
Pars Tuberalis
Part of the adenohypophysis
Sleeve around the neural stalk/median eminence
Transversed by numerous portal venules that receive tributaries from the capillary plexus of the median eminence
outer→ pars tuberalis (little wholes- pituitary portal system)
inner grey → infundibular stalk
center whole→ infundibular recess
slice of the hypophyseal at the level of the pituitary stalk
Cells of the pars tuberalis
Weakly basophilic cuboidal cells
–organized as cords
–some clusters or follicles (function not established)
Some gonadotropes, thyrotropes (basophils)
Subject to seasonal variations
–High density of melatonin receptors
–May play a role in establishing seasonal reproductive cycles
Pars intermedia
Part of the adenohypophysis adjacent to the neural lobe
–separated by a thin sheet of connective tissue and the residual lumen of Rathke’s pouch
Well developed in domestic animals
(not prominent in humans)
Cell of the pars intermedia
Melanotropes
–basophil
–present in cords, clusters
–some follicles w/ colloid (variable w/ species)
–secrete melanocyte-stimulating hormone (MSH; aka melanotropin)→ Stimulates melanocyte melanin production & release
Others cells variable w/ species–include those abundant in pars distalis (i.e. corticotropes)
little balls- follicles
found in cat pars intermedia of the adenohypophysis of pituitary gland
Hypothalamic control of the pars distalis
Neuro-endocrine cells of the basal hypothalamus produce “releasing factors” or inhibitory hormones
Transported axonally to the external zone of median eminence
Released into hypophysial portal system
Transported to cells of pars distalis
HPA axis
(hypothalamyl-pituitary-adrenal)
Hormone production stimulated by:
–neural mechanisms
–physical/psychological stress (starvation, etc)
–diurnal fluctuations
HPT axis
hypothalamyl-pituitary-thyroid
Regulation of MSH production in the pars intermedia
–Melanotropes are modulated by hypothalamic axons that penetrate the pars intermedia
–MIH (also known as Melanostatin), produced by hypothalamus, is associated with neurons that reach into the pars intermedia
–melanotropes are not regulated via the hypophysial portal system
Neurohypophysis
Derivative of the ventral hypothalamus
(divided into the pars nervosa, infundibular stalk and median eminence)
made of neurosecretory neurons and pituicytes
Connected morphologically & functionally to hypothalamus
unmyelinated neural fibers with cell bodies in the hypothalamus
neurohypophysis
neurosecretory neurons
–originate in supraoptic and para-ventricular regions of the hypothalamus
–unmyelinated nerve fibers connect the hypothalamus to the pars nervosa (aka Hypothalamo-hypophyseal tract )
–transport neurosecretory products along axons
–product accumulates near axon terminals (called Herring bodies)
___ originate in supraoptic and para-ventricular regions of the hypothalamus
neurosecretory neurons
neurosectetory neurons are unmyelinated nerve fibers connect the hypothalamus to the ___ (aka Hypothalamo-hypophyseal tract )
pars nervosa
neurosecretory neurons
product accumulates near axon terminals (called ___)
Herring bodies
Pituicytes (neuroglial cells)
part of neurohypophysis (pituitary gland)
–modified astrocytes
–function not well understood
»may regulate hormone secretion
»assist w/ axon growth and regrowth
»remove damaged axons
uNeurosecretory neurons of hypothalamus produce___
oxytocin
antidiuretic hormone (ADH= vasopressin)
neurophysins (Carrier proteins)
Neurosecretory neurons of the hypothalamus have axon terminals abut perivascular spaces of ___ in pars nervosa
sinusoid capillaries
pituitary gland
herring bodies
hormones stored terminals pars nervosa of the neurohypophysis of the hypophysis (pituitary gland)
herring bodies: hormones stored terminals pars nervosa of the neurohypophysis of the hypophysis (pituitary gland)
pituicyte nuclei
TSH is made by ___ and does
ACTH is made by ___ and does ___
FSH is made by ___ and does __-
LH is made by ___ and does ___
GH is made by ___ and does ___
Prolactin is made by ___ and does ___
MSH in made by ___ and does ___
`
Oxytocin is made by ___ and does ___
ADH is made by ___ and does ___
Thyroid gland
Thyroid hormone T3,T4
calcitonin
parafollicular cells (C Cells)
follicular cells filled by colloid
follicle help increase iodine concentration which is an important precursor to thyroid hormones
Follicles of thyroid gland are filled with ___ also called ___
colloid
thyroglobulin
Thyroid follicular cells
principal cells
acidophilic
polar cell morphology
make Thyroglobulin and Thyroperoxidase
Follicular cells produce colloid which is made of ___ and ___
thyroglobulin
Thyroperoxidase
Thyroglobulin is made of ___ and is made by the ___and secreted via secretory vesicles into ___
glycoprotein
ER/Golgi complex
follicle lumen
Thyroperoxidase is synthesized and secreted into the ___
follicle lumen
thyroperoxidase Iodinates thyroglobulin on ___
tyrosines
Iodine deficiency can cause a ___ to form.
goitre
explain how follicular cells secrete T4 and T3
–thyroglobulin is taken up from follicular lumen resulting in colloid droplets
–droplets merge with lysosomes (phagolysosomes)
–thyroglobulin is broken down into thyroxine (T4) and triiodothyronine (T3)
–T3 and T4 diffuse out cellular base
___ is a pro-hormone; converted to T3 by target cells
Thyroxine (T4)
___ accelerates metabolic rate of body
Triiodothyronine (T3)
three things Triiodothyronine (T3) can do
–accelerates metabolic rate of body
–Increase cell metabolism, growth, differentiation, development
–increases protein, carbohydrate and fat metabolism
hypothyroidism leads to weight loss true or false?
false, they gain weight due to lack of thyroid hormones
TRH from hypothalamus stimulates ___ to release TSH
adenohypophysis
TSH stimulates ___, ___ and ___ of thyroid follicular cells
–synthesis, iodination and follicular storage of thyroglobulin
TSH stimulated the follicular storage of ___ by follicular cells
thyroglobulin
TSH stimulates thyroid follicular cells to release thyroid hormones (___ and __ ) into general circulation
T3 and T4
parafollicular cells are derived from ___
neural crest cells
where can parafollicular cells be found
in the thyroid
in small clusters within the basal lamina of follicles
or
outside of the follicle (dogs)
parafollicular cells
found in thyroid→ C cells
pale staining cytoplasm
clusters or single cells
Little ER, abundant Golgi, many small secretory granules, mitochondria
Secrete calcitonin
parafollicular cells secrete ___
calcitonin, seratonin and somatostatin
8 parafollicular cells
5: follicular cells in transcut
Calcitonin
produced by parafollicular cells of the Thyroid
–Lowers blood calcium levels
–Reduces number and activity of osteoclasts in bones
–production is not controlled by pituitary functions
–Stimulated by high blood Ca++ levels
Parathyroid is found ___
in the thyroid, usually 4 in mammals
___ is separated from thyroid by thin capsule of dense irregular connective tissue
parathyroid
Parathyroid have cells that are arranged in cords or clusters, with many blood vessels and ___colloid filled follicles.
rare
Parathyroid produces __ when __ is low
PTH
calcium
Parathyroid produces parathormone (PTH) which regulates blood ion levels- especially ___
calcium
What will happen is parathyroid is damaged?
If removed/ablated, all muscles will undergo rigid spasms as blood calcium level falls
parathyroid
thyroid
two types of parathyroid cells
chief cells (principal cells)
- produce parathyroid hormone (PTH parathormone)
not regulated by hypophysis (pituitary glands)
oxyphil cells (unknown function)
Chief cells produce ___ and are not regulated by the ___
parathyroid hormone (PTH, parathormone)
hypophysis
PTH production is regulated by __ levels
blood calcium
___ is the antagonist to thyroid calcitonin
parathyroid hormone (PTH)
PTH increases blood calcium
calcitonin decreases blood calcium
explain how calcium levels effect PTH
increases calcium levels
–triggers increased Vit D3 production in kidney (necessary for Ca++ absorption in gut)
–stimulates Ca++ absorption by distil convoluted tubules
–raises Ca++ levels by stimulating osteoclast activity and proliferation (indirectly via osteoblasts)
deficiencies in PTH lead to
Decreased blood calcium
–Fibrillary twitching in muscles
–Spasms of limb muscles
–Rigid spasms
–Death
Parathyroid Oxyphil Cells
Unknown function
Large (27 um), single or in clusters
Abundant in horses and ruminants
Rare in other domestic mammals
Very rich in mitochondria
Scarce in Golgi, rER, granules (inactive secretion)
Parathyroid Oxyphil Cells
adrenal gland
3 parts of adrenal gland
capsule
cortex
zona glomerulosa
zone fasciculata
cona reticularis
medulla
adrenal gland is surrounded by a ___ made of ___, ___ and ___
capsule
–dense irregular connective tissue
–occasional smooth muscle fibers
–clusters of undiffentiated cells»precusers to zona glomerulosa
The cortex of the adrenal gland has a __ origin
mesodermal
The medulla of the adrenal gland has a ___ origin
neuroectodermal
the zona glomerulosa produces ___ and is found in the ___
mineralcorticoids (aldosterone)
cortex of the adrenal gland
The zona fasciculata produces __ and is found in the __
glucocorticoids (cortisol, cortisone)
cortex of the adrenal gland
The zona reticularis makes ___ and is found in the ___
Glucocorticoids (cortisol) Sex hormones (DHEA)
cortex of the adrenal glands
The medulla of the adrenal gland makes ___
catecholamines (epinephrine, norepinephrine)
Zona glomerulosa
layer directly under capsule of adrenal gland
Cell chords:
– irregular spherical clusters -Glomeruli (most domestic animals, ruminants)
– arcs or loops of tall columnar -Zona arcuata (horses, some carnivores, pigs)
– surrounded by sinusoidal capillaries
Cell features:
– Abundant sER, mitochondria, Golgi, lipid droplets
– Secrete mineralocorticoids
Zona fasciculat
2nd zone (in between zona glomerulosa and zone reticularis)
Radially arranged cords of cuboidal or
columnar cells separated by sinusoidal
capillary network
Cells of zona fasciculata
–contain numerous lipid droplets, which are
not well preserved in standard tissue preps
– Spongy appearance (spongiocytes)
– Produce glucocorticoids (GCs)
produces glucocorticoids
zona reticularis
deepest part of cortex of adrenal gland
Irregular network of cell cords
Polyhedral cells
fewer lipid droplets than cells of zona fasciculata produce glucocorticoids, and sex hormones
aldosterone
a mineralocorticoid
– Produced in zona glomerulosa (top layer of adrenal gland cortex)
» NOT regulated by hypophysis
– Increases sodium reabsorption from glomerular filtrate in kidney
– Increases potassium excretion
– Increases fluid volume
– Restores electrolyte balance
– Raises blood pressure
Glucocorticoids
cortisol, cortisone
Produced in zona fasciculata and zona reticularis (middle and bottom layer of cortex of adrenal gland)
– Regulate blood sugar levels
– Regulate protein, fat, carbohydrate metabolism
– Suppress inflammatory response
– Regulated by ACTH from adenohypophysis (HPA axis)
aldosterone increases ___ reabsorption from glomerular filtrate in the kindey
sodium
aldosterone ___ potassium excretion, increases ___ volume, restores ___ balance and ___ blood pressure
increases
fluid
electrolyte
raises
Glucocorticoids regulate blood sugar levels, regulate protein, ___ and ___ metabolism
fat, carbohydrate
glucocorticoids ___ inflammatory response
suppress
glucocorticoids are regulated by ___ from the ___
ACTH from adenohypophysis (HPA axis)
sex hormones such as ___ are made in the ___
dihydroepiandrosterone-DHEA
zona reticularis
cortisol = ___ hormone
pleiotropic
what are some things cortisol does
hyperadrenocortism
cushings
hair growth issues
HPA axis
adrenal medualla cells are called ___
chromaffin cells
adrenal medulla cells are
Modified post-ganglionic sympathetic neurons
– Basophilic polyhedral cells arranged as irregular cords and clusters
– Regulated by preganglionic sympathetic innervation (not by hypophysis/pituitary)
Separated by dense sinusoidal capillaries
- *make Catecholamines (epinephrine,**
- *norepinephrine) (fight or flight)**
fight or flight is stimulated by
adrenal medulla function
Catecholamines (epinephrine, norepinephrine)
Catecholamines production is regulated by ___ via sympathetic nervous system in response to ___
(epinephrine, norepinephrine)
hypothalamus
fear or acute stress
epinephrine, norepinephrine which are ___ produced by the ___ will ___ heart rate and cardiac output and blood flow and will also ___ blood glucose from the liver
catecholamines
adrenal medulla
increase
induce a surge of
overview of thyroid
Follicle cells: T3, T4 → increase metabolism
Parafollicular cells: Calcitonin → decrease blood Ca++
overview of parathyroid
Chief cells: Parathormone → increase blood Ca++
Oxyphil cells: unknown function
overview of adrenal cortex
Mineralocorticoids (aldosterone) →electrolyte balance. made in zone glomerulosa
Glucocorticoids (cortisol, cortisone)→ blood sugar levels during stress, etc, made in zone fasciculate and zona retucularis
Sex hormones (DHEA) (probably insignificant), made in zone reticularis
adrenal medulla overview
Catecholamines (epinephrine, norepinephrine) → “fight or flight” response
basophils in pituitary gland effect what?
acidophils in pituitary gland effect what?
MSH produced in the pituitary gland effect what?
Hypothalamic control of pituitary hormone release
