Endocrine System Flashcards
Describe endocrine glands.
-ductless glands
-secrete hormones into bloodstream to distant target organs
*exocrine secrete onto epithelial cells
Describe the 3 types of signaling molecules.
hormones
1. Autocrine = stimulate/inhibit self
2. Paracrine = stimulate/inhibit adjacent cell
3. Endocrine = stimulate distant target cell
Describe how endocrine hormones travel via the blood stream to target cells.
- hormones = bind to receptors on target cell ‘feedback loop’
>hypothalamus (releasing hormones) -> pituitary (paracrine cytokines & GFs) -> target gland (stimulating hormones) - steroids = pass through PM of target cell to bind to nucleus
Describe the 5 primary endocrine glands.
- Pituitary gland (hypophysis)
- Pineal gland (epiphysis)
- Thyroid gland
- Parathyroid gland
- Adrenal gland
What are the functions of the major endocrine organs?
-regulate internal environment
-energy production, storage, utilization
-growth & development
-reproduction
endocrine diseases result in excess/insufficient production of hormones
List the secondary endocrine organs.
Pancreas
Testes
Ovaries
Kidneys
Stomach
Intestines
Thymus
Heart
Placenta
Adipose tissue
Describe the hypothalamus.
-integrates NS & endocrine system = ‘neurosecretory neurons’ (paraventricular & supraoptic nuclei)
-homeostasis
-signals from the CNS
-BBB absent
-ventral part of brain below thalamus
Describe the flow from the hypothalamus to the pituitary gland.
Hypothalamus -> releasing hormones (GnRH, GHRH, TRH, CRH, PRF) -> anterior pituitary (ACTH, TSH, FSH, LH, GH, PRL) -> stimulating hormones from posterior pituitary (ADH & Oxytocin)
Describe the pituitary gland.
‘Hypophysis cerebri’
-ventral to hypothalamus (H), near optic chiasm (O)
-lies in hypophyseal fossa of sella turcica (ST) bone
-pituitary gland (P) = 2 parts
1. Anterior (infront) = adenohypophysis (AP)
2. Posterior (back) = neurohypophysis (PP)
Describe adenohypohysis VS neurohypohysis.
- Adneohypophysis
-anterior pituitary
-Rathkes pouch
-epithelial (roof of pharynx) ectoderm - Neuroectodermal
-posterior pituitary
-from diencephalon
Describe the anterior pituitary.
- Pars distalis
- Pars tuberalis
- Pars intermedia
-between neurohypophysis & pars distalis
hypophyseal cavity = remnant of rathkes pouch
Adenohypophysis: pars distalis (H&E)
-chromophils (stimulating hormones0
>acidophils (A) = GH, PRL pink
>basophils (B) = ACTH, TSH, FSH, LH purple
-chromophobes (C)
-sinusoids (S)
Adenohypophysis: pars distalis (LH stain)
immunohistochemical stain = antibodies & secondary stain
Adenohypophysis: pars intermedia
-between pars nervosa & pars distalis
-large pale cells
-produce POMC (proopiopmelanocortin)
-POMC cleaved into endorphins, melanotropins, lipotrophins
Picture of interglandular cleft.
-remnant of rathkes pouch = hypophyseal cavity
Describe neurohypophysis.
- Pars nervosa
- Infundibulum
-stores hormones made in hypothalamus
>ADH
>Oxytocin
Describe neurohypophysis: pars nervosa
-unmyelinated nerve fibers (neurosecretory)
>herring bodies (H) = store ADH & oxytocin
-pituicytes
>support
Describe the hypothalamo-pituitary axis & portal system.
Portal system = 2 capillary beds
-anterior = into portal system
-posterior = on plexus into collecting vein
Describe the hypothalamus neurosecretory neurons.
Describe the hypothalamo-pituitary-peripheral target organ axis.
Neurohypophysis = posterior pituitary
1. vasopressin (ADH) -> kidney
2. oxytocin -> mammary gland & uterus
Adenohypophysis = anterior pituitary
1. ACTH -> adrenal cortex
2. TSH -> thyroid gland
3. GH -> liver, muscle, bone
4 & 5. LH/FSH -> gonads
6. PRL -> mammary gland (corpus luteum)
Describe the pineal gland.
‘Epiphysis cerebri’
-pinealocytes secrete melatonin (stimulated by darkness)
>blood vessels
>neuroglial supporting cells
-stimuli detected in retina
-regulates rhythms of body activity
>circadian rhythm
-seasonal reproduction
Describe the thyroid gland.
regulated TSH secretion
1. follicles (F)
>cuboidal follicular cells secrete ‘thyroglobulin’
—convert colloid to active ‘thyroxine’ -> increases basal metabolic rate, thermogenesis, gluconeogenesis
>stored in follicle lumen ‘colloid’ & combined w iodine
2. Parafollicular ‘C’ cells (C)
-lg, pale, round
-secrete calcitonin (in response to increased plasma calcium)
>decreases plasma calcium
>decrease osteoclast activity (Ca stored in bones)
>increased renal excretion
Describe active vs less active thyroid follicles.
-Less active on left & more active on right
-parafollicular cells in between
Describe parathyroid glands.
-adjacent to thyroid gland (1 internal & 1 external)
-Chief cells = secret parathormone (PTH) in response to decreased plasma Ca
>PTH increases plasma Ca
>stimulates osteoclasts (bone reabsorption & Ca release)
>increases intestinal uptake
>increases renal reabsorption
Describe the adrenal gland.
-near kidney
-cortex = mesoderm
>3 zones
-medulla = neural crest
>modified neurons & secrete catathecolamines
Describe the adrenal cortex zones.
‘Salt, Sugar, Sex’ = GFR
1. Zona glomerulosa
-mineralocorticoid (aldosterone -> Na/H2O reabsorption & K secretion = increase BP
2. Zona fasciculata
-glucocorticoid (cortisol -> liver, skeletal muscle, adipose, immune cells)
3. Zona reticularis
-sex steroids (weak androgens) -> male characteristics
Stimulus VS effect.
Stimulus / effect
1. Low BP (angiotensin II) / Na/K ATPase (increases BP)
2. Stress received by hypothalamus (ACTH) / cortisol release (gluconeogenesis in liver, decrease glucose use by muscle & fat, skeletal muscle break down, immunosuppression)
3. Sympathetic NS / fight or flight
Describe the adrenal medulla.
-sympathetic ganglia
-vascular sinusoids
-chromaffin (phaeochromocytes) = secrete EPI & NE
>pale, foamy
-adrenaline & noradrenaline
Describe the endocrine pancreas.
-secondary endocrine organ
-2% endocrine = islets of langerhans
-98% exocrine = digestive enzymes
Describe pancreatic islets of langerhan.
- Alpha cells
-glucagon - Beta cells
-insulin
Describe enteroendocrine cells.
-hormone producing cells in digestive system
>gastrin
>cholecystokinin (CCK) for gall bladder contraction
>secretin & gastric inhibitory polypeptides
Describe the heart as a secondary endocrine organ.
-atrial myocardial cells secrete ANP
>ANP promotes Na, water loss, decreases BP
Describe the kidney & endocrine system.
Kidneys produce 2 hormones:
1. Renin
-made by juxta cells
-RAAS
-control BP
2. Erythropoietin
-controls RBC production
-cytokine for RBC precursors
