Lecture 36: Endocrine Flashcards
difference in formation of endocrine vs exocrine glands
both invaginate into the connective tissue but exocrine remains in a duct that secretes into the lumen, endocrine is separated and duct cells dissapear
two types of endocrine cells
cord/cluster and follicle (these are both surrounded by capillaries)
hormones
chemical substances synthesized by endocrine cells and secreted
where do hormones get secreted
into bloodstream(distant target cells), into tissue space (adjacent or nearby target cells), onto own cell surface (own target cells)
three signaling mechanisms
- endocrine
- paracrine
- autocrine
endocrine signaling
secreted into the blood
paracrine signaling
secreted into extracellular space (eg somatostatin inhibits insulin secretion in islets of langerhan)
autocrine secretion
secreted on own cell surface (eg insulin, TGF beta)
what are the three types of hormones chemically speaking
- peptides and glycoproteins (pit hormones, parathyroid, islets of langerhan and GI tract)
- steroids (hormones of adrenal cortex, ovary and testis)
- amino acids (tyrosine) eg hormones of thyroid and adrenal medulla
on an EM what is noticeable about peptide/glycoprotein hormones
contain granules which store the hormones
steroid hormone producing cells on EM
hormones not stored in cells
Endocrine glands whose sole functions are hormone production
PPPAT Pituitary Pineal Thyroid Parathyroid Adrenal
endocrine tissues found in association with organs which have other functions
pancrease, ovary, testis, kidney, liver
diffuse endocrine system
single hormone producing cells diffusely scatted in the digestive and respiratory systems
where is the pituitary located
beneath the floor of the third ventricle, connected to the hypothalamus
other word for pituitary
hypophysis
where does the pituitary lie
in the hypophyseal fossa, a bony depression of the sella turcia of the sphenoid bone
other word for anterior pituitary
adenohypophysis / pars distalis
parts of anterior pituitary
pars tuberalis
pars intermedia
parts of posterior pituitary
infundibulum (pituitary stalk) and median eminence (hypothalamus)
other word for posterior pituitary
neurohypophysis / pars nervosa
where do the neurohypophysis (posterior pit) and adenohypohysis (anterior pit) originate from
neuro = nervous tissue of the hypothalamus
adeno = ectoderm of the roof of the mouth
DIFFERENT EMBRYO SOURCES
how many hormones and cell types in the pituitary
6 hormones
1) GH
2) Prolactin
3) Corticotropin (ACTH)
4) FSH
5) LH
6) Thyrotropin (TSH)
5 cell types because FSH and LH are from the same cell type
where are anterior pituitary hormones stored
in the granules
endocrine cell types of anterior pituitary/pars distalis
Acidophils 1. Somatotrophs (50%) GH 2. Mammotrophs (20%) prolactin Basophiles 3. Corticotrophs (20%) Corticotropin (ACTH) 4. Thyrotrophs (5%) Thyrotropin (TSH) 5. Gonadotrophs (5%) FSH and LH Chromophobes: degranulated acidophils or basophils
FSH and LH target
the ovary and testis
ACTH target
adrenal cortex
GH target
skeleton (bone growth), adipose tissue, and muscle
Prolactin target
mammary gland
what is secretion in the pars distalis/ant pit controlled by
hypothalamic releasing or inhibiting hormones
what controls hypothalamic releasing or inhibiting hormones
hypophyseal (pituitary) portal system which provides anatomical-functional link between hypothalamus and pars distalis of ant pit
what is the blood supply to the pituitary
hypophyseal portal system
map of control of pars distalis
- hypothalamus releases neurosecretory cells (neurons) with releasing or inhibiting hormones
- these go through the hypophyseal portal system and act on ant pit hormones
- these then act on target organs
hypothalamic hormones and their function
- GH releasing hormone
- Corticotropin releasing hormone
- TSH releasing hormone
- Gonadotropin releasing hormon
- Dopamine (inhibits prolactin release)
- Somatostatin (inhibits GH release)
where is the pars intermedia
in between ant pit and post pit
what does pars intermedia release
2 types of MSH (melanocyte stimulating)
1. beta MSH for skin pigmentation 2. alpha msh for anti appetite
what are MSHs a product of
pro-opiomelanocortin (POMC)
what are the cells (granules) of the pars intermedia similar to
those of corticotrophs which secrete ACTH
what do cells/granules of pars intermedia and corticotrophs synthesize
pro-opiomelanocortin which splits into
- ACTH (lipotropins for lipid metabolism) 2. Endorphines (endogenous opioids)
- MSHs (beta and alpha) for skin pigmentation and anti appetite
hormones secreted by pars nervosa of of post pit
Antidiuretic hormone (ADH, vasopressin) and oxytocin
what are ADH and oxytocin bound by and where are they released from
a carrier protein and secreted by pars nervosa of post pit
herring bodies
sites of accumulation of hormones combined with neurophysin in the terminal portion of an axon
what controls hormone release in herring bodies
nerve impulses passing down axons from hypothalamus
what is the pineal gland
diverticulum of posterior diencephalon and located at posterior end of third ventricle
corpora arenacea
extracellular calcified bodies containing CaPO4 and MgPO4 and carbonate in an organic matrix. INCREASE WITH AGE!
what secretes melatonin
pinealocytes
what regulates synthesis of melatonin
incuded by darkness and supressed by light, thought to regulate diurnal rythyms of body
what is melatonin synthesized from
amino acid tryptophan via serotonin
side effect of melatonin
antireproductive effects because decreases gonadotropin release
