Histology: Hypothalamus & Hypophysis
what are the releasing factors/hormones secreted by the arcuate nucleus of the hypothalamus?
- GHRH growth hormone releasing hormone -GHIH growth hormone inhibiting hormone - PRH prolactin releasing hormone - PIH prolactin inhibiting hormone - GnRH gonadotropic releasing hormone - CRH corticotropic releasing hormone - TRH thyrotropic releasing hormon
how does the pituitary gland form?
Rathke's pouch, a hypophyseal pouch that has bud off from area near the stomodeum (mouth opening) and will go into the hypophyseal fossa to become future adenohypophysis neurohypophyseal bud (from infundibulum) will form the neurohypophysis in the hypophyseal fossa
what are the cells of adenohypophysis mainly in pars distalis?
acidophils - eosin loving stain pink basophils chromophobes - colorless
what are the conditions associated with hypo/hyper pituitary and growth hormones before and after puberty?
before puberty: dwarfism with hypopituitary secretions and gigantism with hyperpituitary secretions after: acromegaly: increased bone deposition, apositional growth
what is the blood supply to the pituitary gland and through which veins do the hormones get secreted?
blood supply: superior and inferior hypophyseal arteries veins: hypophyseal veins to the cavernous sinus --> sup. and inf. petrosal sinuses --> sigmoid sinus --> internal jugular --> heart
what are the cells of the neurohypophysis that store vasopressin and oxytocin
bublous sacs called varicocytes or neurosecretory bodies or herring bodies and store either oxytocin from paraventricular nucleus and vasopressin from supraoptic nucleus
the arcuate/tuberal nucleus of the hypothalamus is connected to the adenohypophysis through what?
hypothalamo-hypophyseal portal system
which part of the brain is the center for controlling emotions, autonomic functions, and hormone production?
hypothalamus
what was the diencephalon derived from?
neuro-ectoderm, so neurons
what is the protein bound to the hormones stored in herring bodies?
neurophysin, to prevent from degradation
the hypothalamus consists of four main nuclei what are they? what are their functions?
paraventricular nucleus: mostly produces oxytocin (some ADH) supraoptic nucleus: mostly produces ADH (some oxytocin) suprachiasmatic: stimulates pineal gland to secrete melatonin tuberal/arcuate nucleus: stimulates the adenohypophysis via releasing factors to secrete specific hormones
what are the subdivisions of the adenohypophysis?
pars tuberalis: surrounding infundibulum pars intermedia: in between the two lobes pars distalis:
what are the resident cell types in the pars nervosa?
pituicytes, glial-like support cells that express glial fibrillary acidic protein (GFAP)
which part of the brain is the center for relay and processing for sensory information?
thalamus
the hypophysis consists of two lobes what are they? what are tissue types existing in each lobe?
the adenohypophysis (ant. lobe): adeno (gland) so epithelial tissue the neurohypophysis (post. lobe): neural tissue just like the infundibulum
what are the thalamus, hypothalamus, and epithalamus derived from embryologically?
the diencephalon
where does the pituitary or hypophysis sit in? what is it covered by?
the hypophyseal fossa in sella turcica of sphenoid bone covered by the sellar diaphragm
what is the hypothalamus connected to the neurohypophysis by?
the hypothalamo-hypophyseal tract connecting the paraventricular and supraoptic nuclei to the neurohypophysis
what is the connection between the hypothalamus and the hypophysis called?
the infundibulum or connecting stalk
which part of the pituitary stains light/dark?
the pars nervosa (and infundibulum) of the neurohypophysis stains lighter due to neural tissue whereas pars distalis stains dark
what are the basophils secreting?
they are corticotrophs, gonadotrophs, and thyrotrophs so they secrete adrenocorticotrophic hormone (ACTH), FSH and LH, and thyroid stimulating hormone (TSH)
what are the acidophils producing?
they are somatotrophs and lactotrophs so they secrete growth hormones and prolactin hormone
which hormone from the hypothalamus can stimulate the production and secretion of prolactin, and thyroid stimulating hormone (TSH)?
thyrotropic releasing hormone (TRH) from the arcuate nucleus of the hypothalamus it's very similar to PRH
what is the co-factor that assists growth hormone to produce the environment needs for cells to undergo growth? where is it produced?
IGF-1, insulin-like growth factor-1, produced by hepatocytes the factor induces the entry of glucose into the cells which lowers the blood conc. and therefore the glucose blood conc. does not inhibit GHRH
