Histo, hypothalamus, pituitary Flashcards
What are the parts of the anterior pituitary
pars distalis
pars intermedia
pars tuberalis
What are the parts of the posterior pituitary
pars nervosa
The posterior pituitary is an extension of what
hypothalamus
median eminence and infundibulum
What is the pituitary derived from
oral ectoderm and floor of 3rd ventricle
What does the oral ectoderm turn into
Rathke’s pouch, from oral epithelium
What part forms the pars nervosa or posterior pituitary
infundibulum
What hormones are released from pituitary
growth hormone, ACTH, Thyroid stim hormone, gonadotropic hormones
melanocyte sitmulating hormone
prolactin, oxytocin, ADH
How does blood get to pituitary
blood enters median eminence and splits into superior and inferior hypophyseal aa and a 2nd capillary bed
what is supplied by superior hypophyseal aa
1st capillary bed in hypothalamus
What is supplied by inferior hypophyseal aa
capillaries in neurohypophysis
What is supplied by the second capillary bed
becomes pars distalis,
supplies anterior pituitary
what drains the 2nd capillary bed, or pars distalis
hypophyseal veins
What are the cell types in adenohypophysis (anteiror pituitary)
chromophobes, chromophils
What are the two types of chromophils
acidophils and basophils
What is another name for chromophobes
follicular cells
Describe the chromophobes of anteiror pituitary
stellate shaped, phagocytic maybe
few secretion granules
usually result in immature chromophils
What are the types of acidophils in the chromophils
somatotropes
mammotropes
What is the role of somatotropes
secrete growth hormone
stimulatesd growth of epiphyseal cartilage
stiulates somatomedin production
What is the role of somatomedin and where are its effects
in liver and kidney
What happens in hyper or hypo secretion in ant pituitary, specifically from somatotropes
hypersecretion leads to gigantism, acromegaly and GH diabetes
hyposecretion leads to hypopituitary dwarfism
What factors stimulate growth hormone
decreased glucose [ ] decreased FA concentration arginine fasting or starvation estrogen/testosterone exercise/stress stage III IV sleep alpha adrenergic agonists
What factors inhibit growth hormone
increased glucose [ ] increased FA [ ] obesity senescence somatostatin somatomedins growth hormone beta adrenergic agonists pregnancy
What is gigantism
excessive GH from anterior pituitary in childhood
prior to epiphyseal plate closure
What is acromegaly
excessive growth hormone in adults
what is the role of mammotropes
secrete prolactin
regulate glucose sensitivity os islet beta cells
role in immune function
What is the function of prolactin
stimulates mammary gland development
preparatory to lactation and milk ejection
cells enlarge during pregnancy
influenced by estrogen
What factors stimulate prolactin
pregnancy (estrogen) breast feeding sleep stress TRH dopamine antagonists
What factors inhibit prolactin
dopamine
bromocripline (dopamine agonist)
somatostatin
prolactin (neg feedback)
What cells are found in basophils of the ant pituitary
corticotrophes
thyrotrophs
gonadotrophs
What do corticotrophs secrete
pro-opiomelanocortin (POMC)
ACTH (adrenocorticotropic hormone)
MSH (melanocyte stimulating hormone)
lipotropin
What is POMC
precursor to secretory products of cotricotropes
what is the role of ACTH
sitmulates adrenal corticosteroid secretion
most important
What is the function of MSH
not fully known
large doses do lead to hyperpigmentation
and primarily made in pars intermedia
What is the function of liptropin
mobilizes fat in some species, not clearly demonstrated in humans
Beta LPH and gamma LPH
What do gonadotropes secrete
FSH and LH
describe FSH
follicle stimulating hormone
female: follicular development
male: gametogenesis
describe LH
luteinizing hormone or interstitial cell secreting hormone (ICSH)
female: maturation of graadian follicle, development of corpus luteum, progesterone secreiton
male: stimulates androgen secretion by testicular interstitial cells
Why is it important to have a pulsatile secretion of GnRH
continuous infusion results in downregulation of LH and FSH secretion
What do thyrotropes secrete
thyroid stimulating hormone
what is the function of thyroid hormone
stimulates thyroid gland to synthesis and secretion of thyroid hormones
How are regulatory hormones transported to ant pituitary
hypothalamic-hypophyseal portal system
What are the regulatroy hormones that are released from median eminence
GHRH GHIH PIH PRH TRH CRH FSHRH/LHRH (GnRH)
What are the types of feedback that the regulatory hromones in ant pituitary have
positive/negative
direct and indirect
What part of the brain is the post pituitary an extension of
hypothalamus
What tracts control hypothalamus
CNS, PNS
what nuclei are in post pituitary
supraoptic and PVN
What tract makes up the post pituitary
hypothalamic-hypophyseal
Where do nerve terminals end and what do they have
abut on capillaries and store hormones
Most cells in the post pituitary are what
pituicytes or glial cells
Describe pituicytes
specialized neurons secrete into capillaries
have large dilatations called Herring Bodies
What are herring bodies of post pituitary
have secretion granules and multilaminated membrane structure with a major store of secretory material
What type of substances are in the secretion granules of pituicytes of post pituitary
oxytocin, neurophysin I
vasopressin and neurophysin II
What two hormones are released in pars nervosa
vasopressin ADH
oxytocin
Where is ADH from
supra-optic nucleus in hypothalamus
Where is oxytocin from
PVN in hypothalamus
how are ADH and oxytocin structurally different
different aa in two locations
What are the names for carrier proteins released by post pituitary that carry the hormones
neurophysins
Do neurophysins have a biological function
no
In large doses what are the affects of ADH
in physiologic doese?
large- contract vasc sm muscle
raise BP
in physiological- regulate water retention/excretion
low ADH results in what condition
diabetes insipidus
what happens in diabetes insipidus
distal tubule is impermeable to water
What regulates release of ADH
osmoreceptors in the brain
What is the affect of oxytocin release
uterine wall contraction (childbirth)
myoepithelial cells of mammary epithelium
What is the epiphysis
pineal gland
Where is the pinneal gland located
posterior part of third ventricle
What covers pinneal gland and what connects it
covered by pia mater and connected by short stalk
What is structure within the pinneal gland
lamellar structures “corpora arenacea” brain sand
What are the two cell types in pineal gland
pinealocytes and glial cells
Describe pinealocytes
basophilic cytoplasm
large irregular lobate nuclei with defined nucleoli and produce melatonin and other peptides
Describe glial cells of the pineal gland
astrocytes with elongated nuclei and long cytoplasmic processes
they are found around vessels and between pinealocytes
What are the general affects on body from pineal gland secretions
circadian and seasonal biorhythms
What stimulates release of melatonin
absence of light, photstimuli relayed by SAN and secretion increases in darkness
The effects of melatonin release cause changes in secretion of what organs
gonads and other organs
Where is the thyroid gland located
two lobes connected by isthmus anterior and inferior to thyroid cartilage
what type of inn goes to thyroid gland
ANS
how does the thyroid gland develop
median evagination of endoderm from base of tongue
thyroglossal duct attaches to tongue thru foramen cecum
What forms thyroglossal cysts
the patency of the thyroglossal duct
the proliferating mass of the thyroid in development breaks into what
cords of cells that develop lumen upon formation of colloid
What is unique about hormone storage in thyroid gland
stored extracellulary
What are the endocrine cell types in thyroid cells
thyroid follicular cells
parafollicular cells
describe thyroid follicular cells
enclose colloid
produce large glycoprotein– thyroglobulin
What form of thyroglobulin is in the follicular cell of thyroid gland
T4 thyroxine. T3 is the active form
What do the parafollicular cells secrete
calcitonin
What is the function of calcitonin
lower blood Ca
inhibits bone resorption by directly inhibiting osteoclasts
Describe the histo of parafollicular cells of thyroid gland
large ovoid cells with poorly stained cytoplasm
dense core with secretion granules
How do blood plasma Ca levels effect calcitonin release
increase in plasma Ca increase calcitonin
Describe histo of thyroid follicular cells
continuouse layer cuboidal epithelium with central mass of colloid which is mainly thryoglobulin
how does follicular diameter change constanly
less active follicles– flattneed shape with increased colloid
more active follicles- tall columnar follicular cells with reduced colloid
Describe steps in thyroid hormone synthesis
make thyroglobulin and exocytose into lumen transport I- into cell against gradients oxidse I via thryoid peroxidase change iodine into MIT and DIT couple DIT + DIT= T4 and DIT + MTI=T3 endocytosis of TG proteolysis of iodinated thyroglobulin releases T3 and T4 deiodination and recycling
What inhibits the thyroid hormone synthesis
propylthiouracil
How do T4 and T3 circulate in blood
bound to thyroid-binding globulin and sometimes to albumin and transthyretin
What is more bound in blood T4 or T3
T4
What is the more active thyroid hormone and why
T3 because highger affinity for Receptro
Majority of thyroid hormone is in what form
T4
How does majoirty of T4 get convereted to T3
many tissues have deiodinases
What stimulate thyroid hormone
TSH
thyroid stimulating Igs
increased TBG levels (pregnancy)
What factors inhibit thyroid hormone
I- deficiency deiodinase deficiency excessive I- intake percholate: thiocyanate Propylthiouracil decreased TBG levels
Describe what lack of iodine or deficiency can lead to
hyperplasia of follicular cells with decreased colloid
goiter
What is Hashimotos autoimmune thyroiditis
causes autoimmune destruction of follicular cells
leads to myxedema in adults
cretinism in children
What is the most common hyperthyroidism disease
Graves
autoimmune circulating IgG bind follicular cell and mimic TSH
constant, unregulated stimulation of gland
