Histology of Endocrine Organs Flashcards
Endocrine Vs. Nervous system?
both have the ability to influence physiological functions of organs but go about it differently
mechanism is different –>
nervous system is quick and through a membrane depolarization. it’s short lived
endocrine system –> involves hormones that are distributed throughout the cardiovascular system so takes awhile for the effect to occur! MUCH LONGER LASTING.
important to note about neurons and hormones?
neurons can secrete hormones, so don’t think it’s only endocrine
What are the three classes of hormones and examples of each?
Peptide (chains of AAs)
- largest group of hormones
- GH, PTH
Biogenic Amines (molecules that are altered by changing one amino acid) -TH and EPI (both came from tyrosine)
Steroid hormones (lipids derived from cholesterol) - Estrogen, Testosterone, Cortisol
What are the three ways that hormones are released?
Humoral Stimuli –> release controlled by monitoring levels of ions and nutrients in blood and body fluids.. (release of PTH stimulated by low serum calcium levels)
Neuronal stimuli –> the release is because of the stimulation of nerves. (adrenal medulla is receiving signals from the Sympathetics to release epinephrine)
Hormonal Stimuli –> a release of a hormone is stimulated by the release of another hormone
What are endocrine glands composed of?
how are they arranged?
what makes them different than other cells?
What’s to note about their vasculature?
epithelioid cells (lacking free surface) –> derived from epithelium
they’re arranged in cords and follicles
what’s different is they do NOT have an apical free luminal surface.
super well vascularized (vessels have fenestrated endothelium)
What is the hypothalamus?
where is it located? (Posterior to what, superior to what, part of what (2 things)?
primary site that controls the endocrine function via the pituitary.
it’s located inferior to the thalamus portion of the CNS. It’s located posterior to the optic chiasm, but above the pituitary gland. it’s a part of the 3rd ventricle of the brain, and it’s part of the diencephalon..
What is another name for the pituitary gland?
what part of the skull is it part of?
what is it divided into and what is its other name?
Hypophysis
connected to the hypothalamus by an “infundibulum”
in the sphenoid portion of the skull –> Sella Turcica
Anterior (adenohypophhysis) and posterior (neurohypophysis) portions
What does the hypothalamus directly signal?
it directly influence the anterior pituitary gland by sending out releasing and inhibiting factors.
it directly targets the kidney and uterus through the posterior pituitary because it sends hypothalamic axons down into the posterior pituitary and release ADH and Oxytocin which directly go to the kidney and uterus.
Through sympathetic innervation from the hypothalamus and ANS to go to the adrenal medulla
What does the hypothalamus indirectly signal?
what is this kind of signaling hormone is it called in this case if its indirect?
the hypothalamus releases hormones that stimulate or inhibit the release of OTHER hormones from the anterior pituitary.. these hormones then act on OTHER STUFF
Tropic hormones!
Explain the origin of the pituitary gland?
The anterior and posterior pituitary glands are from ECTODERM
Posterior Pituitary: there’s a little diverticulum that forms within the diencephalon of the brain. and that is the posterior pituitary
anterior to the oropharyngeal membrane is a little ectoderm placode (Rathke’s pouch) that shows up and pinches off to make Rathke’s pouch.. this moves towards the infundibulum and joins with the diverticulum forming from the diencephalon of the neural tube.
the Infundibulum forms the posterior pituitary and infundibular stalk.
Rathke’s pouch forms the rest of the pituitary
What’s between the anterior pituitary and the posterior pituitary?
the lumen of rathke’s pouch as cysts in the adult pituitary gland in the center.
What does Rathke’s Pouch become (pars structures)?
what about the diencephalon?
Pars distills, pars Intermedia, and a portion that wraps around the infundibulum called the Pars tuberalis –> all is the anterior pituitary
it’s the Pars Nervosa –> majority of the posterior pituitary
When does Rathke’s pouch become the anterior pituitary endocrine wise?
as early as 7 weeks (ACTH is formed)
what can happen if Rathke’s pouch is trying to migrate to the infundibulum?
what pathology is it called?
you could have some ectopic pituitary tissue found in other regions like the Pharynx.
“craniopharyngeomas” –> 2-4% of all brain tumors and people think this stray tissue is responsible for those tumors.
what is the part of the hypothalamus that becomes the infundibular stalk?
median eminence
What is the anterior pituitary cellularly composed of?
posterior?
glandular epithelial cells controlled by neurohormones from the hypothalamus
unmyelinated axons from the hypothalamus and supporting cells (glial cells)
What are you going to see in the Pars Distalis as compared to Pars Nervosa?
it’ll be more basophilic.. nervosa is super light staining.
What are the major cell types of the Anterior Pituitary?
Somatotropic Thyrotropic Corticotropic Gonadotropic Mammotropic
What do Somatotropic cells do?
Thyrotropic?
Corticotropic?
gonadotropic
mammotropic?
Secrete GH (in response to a signal from GHRF)
secrete TSH to regulate thyroid gland secretion
secrete ACTH (targeting adrenal gland to release cortisol and glucocorticoids) and MSH (mediate melanin production and helping mediating appetite, arousal, mood)
target the gonads –> FSH and LH
secrete prolactin that stimulates milk production
Of the cells of the anterior pituitary (Pars Distalis), which ones are acidophils, Basophils, Chromophobes,
what else are you going to find in this?
Somatotrophs, Mammotrophs (take up eosin –> acidophils
Corticotrophs, Thyrotrophs, Gonadotrophs (like hemotoxin) –> basophils
Chromophobes –> no one knows but they don’t stain to either
Sinusoidal capillaries (FENESTRATED!)
What are you going to see in the pars intermedia?
where is this located?
between the pars distills and pars nervosa
most of the cells here are basophilic!
there are cysts that are remnant of the interluminal space of rathke’s spouch, lined by simple cuboidal cells.
What are you going to see in the Pars Nervosa?
You’re going to see Hypothalamic unmyelinated axons –> these are accumulating at the axon terminals at large aggregates called “Herring bodies”
any nuclei that’s stained with H&E is going to be glial like cells called PITUICYTES
What do herring bodies do?
they store ADH/Oxytocin..
when the hypothalamus says we need ADH/Oxytocin, they send it to the blood stream through the sinusoidal capillaries and it does its job
What does the infundibulum look like under the microscope?
the middle of it is the neurohypophysis portion (neuro stalk) –> part connecting the pars nervosa and median eminence of the hypothalamus.
On the outskirts you’ll see the adenohypophysis portion (pars tuberalis) which envelopes it! (these are cuboidal cells arranged in cords)
What is the blood supply to the Hypophysis (pituitary gland)
how does it work?
Hypothalamus-Hypophyseal portal system (2 capillary beds!)
1) stimulated –> neurons from the hypothalamus secrete releasing or inhibiting hormones into the primary capillary plexus
2) these hormones travel through portal veins to the Ant Pity where they stimulate or inhibit hormone release in the ant pity
3) in response to releasing hormones, ant pity secretes hormones to secondary capillary plexus.
4) empties into the general circulation via a inferior hypophyseal vein to go through the body.
How does the Posterior Pituitary gland work?
Nerve impulses travel down the axons of hypothalamic neurons, causing hormone release from their axon terminals in the posterior pituitary
What is released from the posterior pituitary and what does each do?
ADH –> targets kidney; regulates sodium and water retention
Oxytocin –> Targets uterine smooth muscle and stimulates lactation; induces birth. may be involved in arousal and social bonding
