Histology of Endocrine Organs Flashcards
How does the endocrine sys vary from the nervous sys?
nervous = needs membrane depolarization; quick and short-lived
endocrine = distributed throughout body, bind to spec receptors; slower but longer
*some neurons secrete hormones*
What are the 3 classes of hormones?
peptide/proteins: largest class (GH, PTH)
biogenic amines: produced by altering specific AAs (Thyroid hormone, epinephrine)
steroid hormones: lipids derived from cholesterol (estrogen, testosterone)
What are teh 3 stimuli controlling hormone release?
humoral = release controlled by monitoring levels of ions and nutrients
neuronal = release stimulated by nerve signals
hormonal = release caused by hormone by another endocrine organ or cell
What embryonic tissue are endocrine glands derived from?
ectoderm
How are endocrine glands generally organized?
epitheliod cells arranged as cords/follicles and some as isolated individual cells
*well vascularized
Where is the hypothalamus located?
below thalamus
behind optic chiasma
surrounding the 3rd ventricle
Upon which bone does the pituitary gland sit?
hypophyseal fossa of the sphenoid bone
How is the pituitary gland attached to the hypothalamus?
by thin stalk = infundibulum
How are the hypothalamus and the posterior pituitary connected?
hypothalamus produces oxytocin and ADH –> stored and released by the post pit
What are the direct targets of hypothalamic hormones?
releasing and inhibiting hormones –> ant pit
oxytocin and ADH –> post pit –> kidney and uterus
sympathetic innervation –> adrenal medulla
What are the 5 main organs indirectly influenced by the hypothalamus?
thyroid
adrenal cortex
mammary gland
gonads
bone
What is the basic embryologic origin of the pituitary?
ectodermal placode –> rathke’s pouch at 3 weeks –> near final location by 8 weeks
infundibulum forms post pit and infundibular stalk
rathke’s pouch forms rest of pituitary
What types of cells make up the posterior pituitary?
axons from hypothalamus and support/glial cells
(axons carry ADH and oxytocin)
What is the pars distalis?
Pars nervosa?
pars distalis = anterior pituitary
pars nervosa = posterior pituitary
What are the major cell types in the anterior pituitary?
somatotrophic (GH)
thyrotropic (TSH)
corticotropic (ACTH and MSH)
gonadotropic (FSH and LH)
mammotropic (prolactin)
What cells are acidophils in the ant pit?
somatotrophs
mammotrophs
What cells are basophils (stain dark purple) in the ant pit?
corticotrophs
thyrotrophs
gonadotrophs
What is the pars intermedia?
btw pars distalis and pars nervosa
function unknown
small basophils and colloid-filled follicles lined by cuboidal epithelium
What cell types are found in the pars nervosa?
unmyelinated axons
herring bodies in axons = expanded nerve terminals storing ADH/oxytocin
pituicytes (glial-like)
fenestrated capillaries
What are the 2 parts of the infundibulum?
neural portion = connecting pars nervosa and hypothalamus; unmyelinated axons
adenohypophysis = surrounding pars tuberalis enveloping infundibular stalk; cuboidal cells arranged in cords
What makes up the hypophyseal portal system?
superior hypophyseal artery –> goes to stalk –> capillary bed to pick up hormones from hypothalamus –> hypophyseal portal vs –> secondary capillary plexus in ant pit to get hormones from ant pit
What is the blood supply like in the posterior pituitary?
inferior hypophyseal artery goes in –> ADH and oxytocin go into fenestrated capillaries (single capillary bed) –> blood goes out through single vein
What is gigantism?
excess production of GH due to tumor
if before growth plates close –> can grow to 8 feet tall
if after plates close –> enlargement of extremities and organs
What are pituitary dwarfs?
hyposecretion of GH –> normal body proportion, but rarely exceed 4 feet tall
