ER Flashcards
Endocrine Organs HISTO
reticular fibers
fenestrated capillaries
secrete hormones
hypothalamo-hypophyseal portal system
carries hormones from hypothalmus to pituitary
development of pituitary
anterior- roof of oropharynx (rathkes pouch)
posterior- floor of diencephalon
pars intermedia- remnants of Rathkes puch
parts of anterior pituitary
(adenohypophysis)
pars distalis
pars intermedia
pars tuberalis
Pars distalis
-part of anterior pituitary
-contains chromophobes
and chromophils ( Acidophils, Basophils )
Acidophils
Somatotropes
Mammotropes/ lactotropes
Somatotropes
Growth Hormone,
inhibited by somatostatin
Mammotropes/ lactotropes
prolactin
inhibited by dopamine produced by hypothalamus
Basophils
Gonadotropes
Corticotropes
Thyrotropes
Gonadotropes
Follicle Stimulating Hormone
Luteinizing Hormone
Corticotropes
ACTH - adrenocorticotropin
POMC- proopiomelanocortin
Thyrotropes
Thyroid Stimulating Hormone
Pars Intermedia
part of anterior pituitary
associated with cells producing MSH ( a- melanocyte stimulating hormone)
Posterior Pituitary
(Neurohypophysis)
- Median eminence
- Infundibulum
- Pars Nervosa
Supraoptic Nucleus
ADH
Paraventricular nucleus
Oxytocin
Adrenal Glands
2 in number, Superior pole of kidney
cortex of gland develops from mesoderm
medulla from NCC
Adrenal Cortex
Zona Glomerulosa ( Aldosterone, regulated by angiotensin 2) Zona fasiculata Zona reticularis ( cortisol & androgens, regulated by ACTH)
Adrenal Medulla cells
Chromaffin cells (modified pot - ganglionic sympathetic neurons) Ganglion Cells
Pancreas- “islets of Langerhans”
central core of the islets contain B cells- with a cells distributed around outer rim.
- Alpha cells- secrete glucagon
- Beta cells- secrete insulin
- delta cells- gastrin & somatostatin
Thyroid
Parafollicular cells- secrete calcitonin ( lowers blood calcium) by directly suppressing osteoclast activity
Parathyroid Gland
4 small glands embedding in the posterior part of the thyroid
- Parathyroid Hormone: stimulates osteoclasts to free Ca from bone, stimulates Ca uptake from intestine & kidney
Cell Types of Parathyroid Gland
Chief Cells- parathyroid hormone ( increases Ca, lowers phosphate)
Oxyphil cells-
Pineal Gland
consists of melatonin secreting pinealocytes
Growth Hormone
secreted by somatotrophs in AP
stimulated by GHRH
* also stimulated by Ghrenlin (hypoglycemia)
inhibited by somatostatin ( GHIH)
mechanism- tyrosine Kinase
overall effect is to increase blood glucose
mechanism of GHRH
increase cAMP- increase Ca
Actions of GH
liver - (increase blood glucose and IGF)
Adipose tissue - ( increase lipid breakdown, decrease glucose uptake)
Muscle- ( increase protein synthesis, decrease glucose uptake)
** increase in blood glucose— increase in insulin
IGFs
somatomedins
important for growth - promoting effects of GH
Alodosterone
- primary effect on kidney tubules and stimulates ion re-uptake and potassium secretion. water follows sodium ions causing an increase in ECF that will raise BP.
- released by Adrenal Cortex (Zona Glomerulosa)
- stimulated by Angiotensin 2
Cortisol
- secreted in response to ACTH
- released from Adrenal Cortex ( Zona Fasciculata/ Reticularis)
- Adipose Cells: increase lipolysis
- Liver: increase glucose, glycogen
- muscle: increase protein breakdown
- transport: corticosteroid binding glubulin
Androgens
- synthesis is stimulated by ACTH.
- released from adrenal gland ( Zona fasciculata/ Reticularis)
- weak androgens ( dehyrdoepiandrosterone (DHEA) and androstenedione are released into blood and can be converted into testosterone or estrogens)
Steroid Hormone Synthesis
- ACTH leads via protein kinase A to activation of both cholesteryll esterase and stAR
- the generated free cholesterol is transported into the mitochondrial matrix
- pregnenolone (21C) is formed from cholesterol inside mitochondria by desmolase (P450 or CYP 11A)
Prolactin
produced in anterior pituitary breast development & milk production inhibited by Dopamine Stimulated by TRH mechanism: Tyrosine Kinase
Antidiuretic hormone
- ADH, AVP, Vasopressin
- synthesized from neuro-hypophysins (posterior pituitary hormone)
- stimulated by increase in ECF osmolarity, decrease in ECF volume
- @ kidney- V2 R – increase cAMP @ principal cells
- @ blood vessels - V1 R— increase IP3 & DAG — increase Ca—- contraction
Oxytocin
released by posterior pituitary ( neurohypophysins)
stimulated by nursing a baby, pressure against cervix
-mechanism: increase IP3 & DAG
Thyroid Releasing Hormone
- synthesized in PVN
- mechanism: increase in IP3 & DAG
Thyroid Stimulating Hormone
- synthesized in thyrotrophs of AP
- promotes growth of thyroid gland
- mechanism: increase cAMP
What is synthesized at thyroid gland?
- Thyroxine (T4)
- Triiodothyronine (T3)
Iodine
synthesis of thyroid hormone requires..
is ingested in idodide (I-) or iodate (IO3)
Thyroglobulin
synthesis and storage of TH remains here
made in epithelial cells- ( synthesized in ribosomes, transport to Golgi, discharged into follicle lumen)
Corticotropin Releasing Hormone
released by PVN cells in the hypothalamus
stimulates ACtH synthesis and release from AP
mechanism: increase cAMP
ACTH
-derived from proopiomelanocortin (POMC)
stimulates Adrenal Cortex ( Zona Glomerulosa)
-conversion of cholesterol to pregnenolone
-mechanism : increase cAMP @ adrenal gland
Steroid hormones
precursor for all hormones is cholesterol
stored as lipid droplets
Angiotensin 2
- stimulates release of Aldosterone @ zona glomerulosa cell of adrenal cortex
- mechanism: increase DAG
Adrenal Medulla
secretes 80% epinephrine, 20% norepinephrine
regulated by Sympathetic control
triggers: stress, exercise, exposure to cold, hypoglycemia
Insulin
B cells of pancreas
stimulated from high glucose
inhibited by catecholamines & somatostatin
mechanism of action: TK
inhibits glucagon release from alpha cells
Glucagon
alpha cells of pancreas
main target is liver
stimulated by : high AA, stress, hypoglycemia
mechanism: increase cAMP
Somatostatin
actions: decrease insulin and glucagon secretion, decrease GIT motility, decrease secretions and absorption by GIT
Parathyroid Hormone
Released by parathyroid gland
stimulated by a decrease in Ca
mechanism: increase in IP3 & cAMP
increase Ca, decrease phosphate
Calcitonin
secreted by C cells of thyroid gland
Gonadotropin Releasing Hormone
released in the median eminence of hypothalamus
mechanism: IP3 and DAG
act on anterior pituitary to release
LH (Leydig/ Thecal cell) and FSH (Sertoli/ Granulosa Cell)
LH and FSh
mechanism: cAMP
Progesterone
secreted in large amounts by the corpus luteum during luteal phase or placenta
