PItuitary Physiology I Flashcards
Describe the embryogenesis of the pituitary gland: when is it first recognizable? When is it maure?
begins at 4-5 wks gestation
mature at 20 wks
Where does the anterior pituitary come brome? What about the posterior pituitary?
anterior comes from Rathke’s pouch: ectodermal evagination of the oropharynx
Posterior (neurohypophysis) is neuarl- comes from the ventral hypothalamus and the 3rd ventricle
Important parts of the neurohypophysis
pars nervosa- bulk of the posterior pituitary
median emminence: upper section of the pituitary, above the pars tuberalis
infundibular stalk: stem that connects the pars nervosa to the base of the brain
rathke cyst may persist at the boundaries of the neurohypophysis
What signaling factors are important for anterior pituitary growth and differentiation?
extrinsic paracrine signals from the diencephalon (dorsally) and the oral ectoderm (ventrolateral)
diencephalon makes BMPs, Wnt5a, and FGF10
oral ectoderm makes sonic hedgehog
What happens if you knock out FGF10? What makes FGF10?
diencephalon makes it.
knock-out mice: Rathke’s pouch fails to proliferate- undergoes apoptosis instead
What is the role of BMP? What makes it?
required for cell division of rathke’s pouch. If inhibited, not invagination of the pouch into the brain occurs
What is the role of sonic hedgehog? What makes it?
oral ectoderm. is expressed throughout oral ectoderm except in regions destined to become rathke’s pouch.
What is the ultimate goal of BMC, FGF, and sonic hedgehog in formation of the pituitary?
o induce the expression of the transcription factor Lhx3. Critical factor for specifying these cells as precursors of the endocrine cell types
What is the anatomy around the pituitary? What are nearby important structures?
attached to the hypothalamus via the infundibulum.
lies on the sella turcica
surround by dura
roof made by the diaphragm sella- dura attached to clinoid porcess
optic chiasm is just above the diaphragm sella
on the sides like many cranial nerves- III, IV, V, VI
How does communication between the hypothalamus and the anterior pituitary occur?
chemicals produced by the hypothalamus and delivered to the anterior pit via blood vessels in the infundibulum
they are released to a capillary network called the primary plexus and transported through the hypophyseal portal veins to a second capillary network called the secondary plexus, which supplies the anterior pituitary.
What is the relationship of the nuerohypohysis to the hypothalamus?
it lies below the hypothalamus
communication occurs via neurosecretory cells that span the distance btw the hypothalamus and the posterior pituitary. hormones are stored in the axon terminals of the neurosecretory cells, which extend to the posterior pituitary. These signals are released when the neurosecretory cells get an action potential, and the signals go to a capillary network within the posterior pituitary
What are the parts of the neurohypophysis/hypothalamus communication
- supraoptic and paraventricular nuclei of the hypothalamus
- supraoptico-hypophyseal tract (contains axons of those neurons)
3 posterior pituitary- axons terminate on capillaries of the inferior hypophyseal artery
What hormones are released by the anterior pituitary?
TSH, prolactin, ACTH (adrenocorticotrophic hormone), GH (growht hormone), FSH, LH
What are the inhibitory hypothalamic influences on the antierior pituitary?
prolactin inhibitory factor, aka dopamine
growth hormone inhibitory factor, aka somatostatin
What are the stimulatory hypothalamic influences on the anterior pituitary?
TRH for TSH
CRH for ACTH
GHRH for GH
GnRH for FSH and LH
