L9 Flashcards
Some hypothalamic hormones are
transported to capillaries in the _________ and released into capillaries there for transport to distant tissues
posterior pituitary
Some hypothalamic hormones
(releasing factors) enter capillaries
that merge into portal veins which
branch into more capillaries in the
_________ to govern the release of trophic hormones there
anterior pituitary
hormones released by the anterior pituitary (6)
ACTH, TSH, LH, FSH, Prolactin, GH
true or false: the anterior pituitary has neurons/synapses
false — no neurons, only cells producing hormones
the anterior pituitary is also known as _______
the adenohypophysis
what is the Rathke pouch?
a structure of ectodermal origin that folds superiorly from the pharynx
during the fourth week of gestation
In the sella, Rathke pouch gives rise to the adenohypophysis anteriorly and intermediate lobe of the pituitary
gland posteriorly. In the suprasellar cistern, Rathke pouch gives rise to the pars tuberalis.
what is a Rathke cleft cyst and how does it form?
Failure of embryonic regression results in a persistent remnant of the embryologic Rathke cleft, which, over time, fills with fluid, resulting in the
formation of a Rathke cleft cyst.
typically intrasellar, intrasellar and suprasellar, or suprasellar, depending on location
Mutations in _________ have been identified in mice and in patients with hypopituitarism.
pituitary-specific transcription
factors
describe sequential appearance of pituitary cell types
sequential appearance of the
terminally differentiated cell types:
gonadotrophs, thyrotrophs, somatotrophs, lactotrophs, and corticotrophs located ventrally to dorsally, respectively
where are the target cells of ADH?
kidney tubules
where are the target cells of oxytocin (two answers)?
smooth muscle in uterus and mammary glands
where are the target cells of ACTH?
adrenal cortex
where are the target cells of prolactin?
mammary glands
where are the target cells of growth hormone (2 answers)?
bones, tissue
where are the target cells of gonadotropic hormones (2 answers)?
ovaries, testes
negative inhibitor of prolactin released by hypothalamus
dopamine
negative inhibitor of GHRH
somatostatin
Five cell types in the adenohypophysis by immunostaining
1- LACTOTROPHS (Mammotrophs): Prolactin (Prl) - acidophils.
2- SOMATOTROPHS: growth hormone (GH) - acidophils.
3- CORTICOTROPHS: proopiomelanocortin (POMC) precursor for ACTH, melanocyte stimulating hormone
(MSH), beta-endorphin, and beta-lipotropin - basophils.
4- THYROTROPHS: thyroid stimulating hormone (TSH) - basophils.
5.GONADOTROPHS: FSH/LH - basophils.
most common cause of excess/inappropriate production of anterior pituitary hormones
an adenoma of the anterior lobe
Adenomas may be nonfunctional
and cause _______ by compressing adjacent normal parenchyma
hypopituitarism
Most pituitary adenomas are ______ in origin
monoclonal
what is a pituitary adenoma?
a non-cancerous (benign) tumor that grows in the pituitary gland, located at the base of the brain
most are small and asymptomatic. larger ones can press on surrounding tissues and lead to headaches and vision loss
non-functioning pituitary tumor vs pituitary adenoma
a non-functioning pituitary tumor is a type of pituitary adenoma that does not produce excess hormones, meaning it doesn’t cause hormonal imbalances in the bod
why do non-functioning pituitary tumors cause symptoms and what are those symptoms?
they cause symptoms due to space occupation
- headache
- visual field defects
- nerve palsies
- interfere with rest of pituitary function - deficiency of hormones
treatment of non-functioning pituitary tumor
surgery (transsphenoidal approach) and radiotherapy
describe negative feedback in the vasopressin pathway
increased blood osmolarity or decreased blood volume are sensed in the brain or thorax, respectively, and increase vasopressin secretion
what are some hormones POMC is a precursor polypeptide for?
ACTH, MSH, endorphins and enkephalins
situations where ACTH are abnormally high (e.g., _______) will tend to result in ______
adrenal insufficiency
release of all POMC peptides, with physiologic consequences (i.e., increased skin pigment)
ACTH stimulates ______, _______, and ______
adrenal cortex (except zona glomerulosa); adrenocortical hormones (except aldosterol); melanocytes
ACTH feedback mechanisms for control
increased cortisol –> decreased corticotropin releasing factor –> decreased ACTH
decreased cortisol –> increased CRF –> increased ACTH
ACTH neural control mechanisms
emotion/excitement/pain/fear –> increased corticotropin releasinf factor (CRF) –> increased ACTH
when are ACTH levels highest
early morning (diurnal pattern)
three glycoprotein hormones
TSH, FSH, LH
roles of FSH/LH in ovaries
FSH stimulates growth of follicles and estrogen secretion
LH stimulates ovulation of follicle, formation of corpus luteum which produces progesterone
roles of FSH/LH in testes
FSH –> sertoli cells –> maturation of sperm (spermatogenesis)
LH –> interstitial cells of Leydig –> synthesize and secrete testosterone
TSH is secreted by _____ in response to _____
thyrotrophs; TRH
what does TSH stimulate?
secretion of T4, T3, and growth of thyroid gland
TSH is inhibited by ______
thyroid hormone via short feedback loop
high concentrations of _____ stimulate secretion of LH and FSH. this is known as ______
estrogen; ovulatory surge
three things FSH stimulates
growth of ovarian follicles, sperm production, inhibin secretion
LH in males is also known as ____
interstitial cell stimulating hormone (ICSH)
describe hypothalamic control of prolactin secretion
prolactin inhibiting factor (dopamine and GABA)
prolactin release factor (PRF) - thyrotropin releasing factor (TRF) and VIP
how does thyroxin control prolactin secretion?
decreased thyroxin –> increased TRF secretion –> increased prolactin
how does estrogen control prolactin secretion?
increased estrogen –> increased TRF receptors on lactotrophs –> increased prolactin secretion
growth hormone stimulates production of ____ and ____
IGF-1 (insulin-like growth factor) and somatostatin
excess of cortisol can cause ____
Cushing’s disease
the posterior pituitary is also known as ______
the neurohypophysis
contrast morphogenetic origin of the anterior and posterior pituitary
anterior pituitary - Rathke’s pouch, an ectodermal outpocketing from the roof of the primitive oral cavity.
posterior pituitary - the infundibulum, the stalk connecting the posterior pituitary to the hypothalamus.
