Endocrine Organ Flashcards
Parenchyma
Cords/clumps of hormone-producing cells
Common feature sof endocrine organs
-
Parenchyma secretes hormones:
- Peptides
- Aa derivatives
- Steroids
- Fenestrated capillaries
- Ductless glands (unlike exocrine)
-
Stroma: reticular connective tissue
- Fibroblasts, nerves, immune cells, etc
Neuroendocrine cells
Morphology & function of a neuron, but ends on a blood vessel.
Secretes neurohormones
Hormone over production
- Increased # of cells (Graves’ disease)
- Increased hormone synthesis/release (genetic changes)
Ex) Pituitary adenoma - benign proliferation of the pituitary
Hormone udnerproduction
-
Disease or autoimmunity destroys an endocrine organ
- Ex) Tuberculosis, Hasimoto’s
-
Genetic abnormalities
- Ex) Hypogonadism
-
Abnormal hormone synthesis
- Ex) GH gene deletion
-
Abnormal secretion
- Ex) Thyroidectomy
Tumors of endocrine glands can cause…
Hormone over production
OR
Compress/destroy othe rorgans
Altered tissue responses to hormones are the result of
receptor mutations (TSH, LH, PTH, and steroid receptors)
Other than the glands, where else do you see endocrine tissue?
Digestive tract
Kidneys
Gonads
Placenta
Hypophysis (pituitary gland) divisions, tissue type, embryologic origin
-
Adenohypophysis (anterior lobe)
- glandular tissue
- ectoderm from roof of mouth
- Pars distalis, Pars tuberalis, Pars intermedia
-
Neurophypophysis (posterior lobe)
- neural secretory tissue
- ectoderm from floor of brain
- Median eminence, Infundibulum, Pars Nervosa
What do the arrows point at?
Rathke’s pouch
Which belongs to the neurohypophysis?
Pars Nervosa
Pars distalis vs Pars nervosa histological difference
Pars distalis is glandular tissue, so there are a lot of epithelial-derived cuboidal cells –> way more nuclei
What cells do you see in the hypothalamus vs the pars distalis vs the pars nervosa?
Hypothalamus - neuroendocrine cells’ cell body
Pars distalis - endocrine cells
Pars nervosa - no hormone-producing cells; just the axons of the neuroendocrine cells of the hypothalamus
What are the 4 regions of the hypothalamus?
Paraventricular nucleus
Supraoptic nucleus
Medial preoptic nucleus
Arcuate nucleus
Describe the cells of the pars distalis
-
Chromophils - secreting secretory granules of hormones into those fenestrated capillaries (pictured)
- Acidophils (pink in h&e; orange in pas-orange)
- Basophis (blue in h&e; purple in pas-orange)
- Chromophobes
- Folliculostellate cells - unknown function
This is a PAS-orange G stain of the pars distalis. What are the purple cells? What are the orange cells?
What do acidophils of the pars distalis release?
Somatotrophs - growth hormone
Mammotrophs/lactotrophs- prolactin
What do basophils of the pars distalis release?
Thyrotrophs - TSH
Gonadotrophs - FSH & LH
Corticotrophs - ACTH
What nucleus of the hypothalamus is the only oen that DOESN’T release hypothalamic releasing or inhibiting factors?
Supraoptic.
What are the hypothalamic releasing & inhibiting factors/hormones for TSH, prolactin, FSH&LH, ACTH, and GH?
-
TSH
- TRH +
- Somatostatin -
-
Prolactin
- TRH +
- Dopamine -
-
FSH & LH
- GnRH +
-
ACTH
- CRH +
-
GH
- GHRH +
- Somatostatin+
Hypothalamohypophyseal Portal system
Concentrates & directs hypothalamic hormones directly to the pituitary before entering general circulation; keeps these hormones (whcih are effective in miniscular amts) localized
- Hormones released into the superior hypophyseal arteryperfuses the hypothalamus, which opens into theprimary capillary plexus
- Shunted to the pars distalis via the hypophyseal portal veins
- Enters the secondary capillary plexus
- Drained by hypophyseal veins
Pars intermedia
- Cuboidal cells and colloid containing cysts (remnant of Rathke’s pouch) between the pars distalis & pars nervosa
- Secretes MSH (melanocyte stimulating hormone)
- Function in humans isn’t understood; stimulates melanin production in lower animals
Which nuclei of the hypothalamus release hormones to the pars nervosa?
What hormones are they releasing?
Paraventricular & Supraoptic
-
Oxytocin & ADH
- synthesized by separate neuroendocrine cells whose cell bodies are located in both the PVN & SON
- sent directly down an unmyelinated axon into the pars nervosa
- Note: no releasing or inhibiting factors like in the pars distalis
Features of neurohypophysis/pars nervosa
- Herring bodies - neurosecretory vesicles at nerve endings
- Pituicytes - supporting cells; NOT hormone-producing
- Capillaries
What is this a slide of?
Neurohypophysis / pars nervosa
You could find ADH in the ___ of the hypothalamus and in the ___ of the neurohypophysis.
PVN of hypothalamus
Herring bodies of neurohypophysis
Pineal gland structure/stroma
- Connective tissue capsule & septae divides gland into lobules
- Fenestrated capillaries
- Corpora arenacea (“brain sand”): calcified concretions
What is the dark area?
brain sand
main cells of the pineal gland
Pinealocytes (90%) - arranged in clumps; produces melatonin during dark periods
Interstitial cells: glial like cells; supportive
Melatonin is secreted during dark periods
Other than its maintenance of circadian rhythms, what else does it do?
-
Antigonadal effects
- Tumors that destroy the pineal –> precocious puberty in children
- Contraceptive properties in humans
- Antiproliferative effects on breast & prostate cancers
Regulation of melatonin secretion
Light in the eyes innervates postganglionic sympathetics from superior cervical ganglion -> axons synapse on the pinealocytes and control melatonin production
Thyroid gland structure
- Bilobed with isthmus
- Fibroelastic connective tissue capsule and septae
- Stroma: reticular cells & reticular fibers
- Fenestrated capillaries
- Has 4 parathyroids on top of it.
2 main cells of the thyroid and what they secrete
Follicular cells: thyroid hormones
Parafollicular cells (0.1%): calcitonin
Colloid
gel-like mass containing thyroglobulin (Storage form of thyroid hormone)
Surrounded by follicular cells
What is going on in this slide?
Identify what the arrows are pointing to
Identify the white bubbles
Follicular cells (cuboidal epithelial cells) makign T3/T4 hormone are also releasing thyroglobulin (white bubbles) into the colloid
Arrows = capillaries
What is this? Where are the receptors? Whats the basal and apical side?
Follicular cell releasing into colloid
Basal side faces the capillary lumen; Apical side faces the colloid
Receptors for hormones are on the basal side!
Where are parafollicular cells?
Between follicular cells
Is this a parafollicular or a follicular cell?
parafollicular because lots granules
