Endocrine Glands Flashcards
Anterior pituitary
- aka
- made up of
aka adenohypohysis
pars distalis
pars intermedia
pars tuberalis
Posterior pituitary
- aka
- made up of
aka pars nervosa
aka infundibular process
the infundibular stem or stalk
the median eminence
The anterior pituitary is derived embryonically from ________________, while the posterior pituitary is really __________ (the hypothalamus).
outgrowth of endoderm called Rathke’s pouch,
Extension of the brain (hypothalamus)
Pars distalis
- fxn
synthesize and release:
- GH
- PRL (prolactin)
- ACTH (adrenocorticotropin)
- TSH
- FSH
- LH
5 types of cells in pars distalis
- what they make
- Somatotrophs (GH)
- Lactotrophs (PRL)
- Gonadotrophs (FSH, LH)
- Corticotrophs (ACTH)
- Thyrotrophs (TSH)
They synthesize, store, and release respective hormones in granules
What is the vasculature of the pars distalis like?
Extensive vasculature of small vessels/capillaries/sinusoids w/in it.
Hormone secreting cells (5) are arranged in rows around capillary endothelial cells THAT ARE FENESTRATED
- allows rapid passage of hormones out from endocrine cells AND
enable diffusion towards cells of releasing factors transported via the hypophyseal portal system
*rapid hormonal response by fast passage into/out of the capillary sinusoids of the anterior pituitary
Pars tuberalis
Collar of cells surrounding the infundibular stalk that contains blood vessels/capillaries coming from the median eminence and leads to pars distalis.
- (blood entering median eminence comes from superior hypophyseal arteries)
Hypophyseal Portal system delivers regulatory peptides (releasing factors) secreted by hypothalamic neurons to cells in anterior pituitary.
- TSH-RH, GNRH, CRH, GHRH, somatostatin, DA
Hypophyseal Portal system
delivers regulatory peptides (releasing factors) secreted by hypothalamic neurons to cells in anterior pituitary.
- TSH-RH, GNRH, CRH, GHRH, somatostatin, DA
Blood vessels/capillaries lead from median eminence to pars distalis.
Blood then leaves the anterior and posterior pituitary via small hypophyseal veins.
Pars intermedia
part of the anterior pituitary that is poorly developed.
Some cells are positive for corticotrophic hormones such as melanocyte stimulating hormone (MSH)
What hormones are released from the posterior pituitary (pars nervosa)?
ADH/Vasopressin
Oxytocin
*released from ends of axons that arise from cell bodies of neurons present in hypothalamus
Pituicytes
supportive astrocyte like glial cells, whose nuclei are seen in the posterior pituitary
Herring’s bodies
terminal ends of axons from the hypothalamus.
temporary storage for hormones (ADH, Oxytocin) and secreted as neurosecretory vesicles
Thyroid gland
Multilobed gland comprised of series of follicles
- Each follicle has a single layer of epithelial cells that surrounds a colloid (central chamber)
- Scattered cells btwn follicles produce calcitonin
Blood supply to and from the thyroid gland
- why the need for such extensive vascularization around the follicles?
To:
Superior thyroid artery (fr ext carotic a)
Inferior thyroid artery (fr thyrocervical trunk)
From:
Superior thyroid vein (to jugular vein)
Inferior thyroid vein (to subclavian vein)
- extensive vascularization allows IODIDE pumping form blood and conversion to IODINE by epithelial cells and release of THYROID H into the blood
Importance of thyroid epithelium
- Producers of colloid
- Convert Iodide to Iodine
- Synthesizes and secretes thyroglobulin into follicle and takes up and digests thyroglobulin to generate thyroid hormone.
Thyroglobulin
large protein rich in Tyr residues sites of iodination and mod. to generate TH
TSH
stimulates synthesis of thyroglobulin and its uptake and breakdown from the colloid with consequent release of T3+T4 into the blood
Colloid
serves as a reservoir of materials for TH production (and actual hormones themselves)
Made by Thyroid epithelium
Calcitonin
decreases release of Ca2+ from bones
Downregulates osteoclastic activity
*opp of PTH
PTH
increase blood calcium levels
Upregulates osteoclastic activity
Parathyroid glands
- how many present in indiv.
- contains which 3 cell types
4-8 present in any indiv.
- Chief cells
- Oxyphil cells
- Adipose cells
Chief cells
Cell type in parathyroid gland
Produce PTH
- increase osteoclast release of Ca2+ from bone
- increase Ca2+ uptake in the GI tract and by the kidney
Oxyphil cells
Adipose cells
Cell type in parathyroid gland
Oxyphil cells contain mitochondria,
Adipose cells contain blood vessels
sig unknown
Adrenal gland
dual organ gland (like pituitary)
Cortex: produces steroids
Medulla: produces and release aa derived hormones
- epi, NE, enkephalins
How does blood travel in the adrenal gland
Blood is delivered via the superior, middle and inferior suprarenal arteries
They branch and enter the capsule via short CORTICAL arteries (into cortex) –>
into the subcapsular arterial plexus –>
anastamosing network of capillaries into medullary region
or
Blood can pass via long CORTICAL arteries more directly to medullary region –>
small capillaries/sinusoids –>
central medullary vein –>
Suprarenal vein
Adrenal cortex 3 layers
- Fxn?
outer to inner
GFR
- Zona glomerulosa
- Zona fasciculata
- Zona reticularis
These cells are all involved in lipid/steroid metabolism
- are all high in relative lipid content
What hormones do these secrete? 1. Zona glomerulosa
- Zona fasciculata
- Zona reticularis
- Zona glomerulosa
- mineralcorticoids (aldosterone) - Zona fasciculata
- glucocorticoids (cortisol) - Zona reticularis
(androgens)
The Zona fasciculata and reticularis are regulated by _______, whereas the glomerulosa is regulated through ______
ACTH
(fasciculata +reticularis)
angiotensin system
(glomerulosa)
Adrenal medulla has cells that make what hormones? What are the cells controlled by?
epinephrine (adrenalin)
norepinephrine (noradrenalin)
Enkephalins
Chromogranins
Under sympathetic and parasympathetic control
