Pituitary, Pineal, Islets of Langerhans Flashcards
characteristics of endovrine organs
- ductless glands
- usually secrete hormones into bloodstream via fenestrated caps
- generally have systemic effects
protein hormones
- prolactin, growth hormone
- bind surface receptors
peptide hormones
- ADH, oxytocin
- bind to cell surface receptors and activate 2nd messangers
cholesterol derived hormones
- steroid hormones, estrogen, glucocorticoids
- diffuse into cell and directly effect transcription
eicosinoid derived
- prostaglanidins
- diffuse into the cell and directly effect transcripition
monoamine hormones
-derived from single amino acids such as phe, tyr, tryp
posterior lobe of the pit components
- aka neurophysis
- pars nervosa
- infindibulum
anterior lobe components
- aka adenohypophysis
- pars distalis
- pars intermedia
- pars tuberalis
pituitary development
- anterior pituitary is derived from the oropharynx ectoderm and originally has a Rathke’s pouch which later partially closes
- posterior pit is derived from neuroectoderm (from floor of 3rd ventricle)
- eventually the pit will be surrounded by the sphenoid bone
cells of the pars distalis
- chromophobes
- basophils
- fenestrated caps
- acidophils
- endothelium
acidophiles
- somatotropes: growth hormone
- lactotropes/mammotropes: prolactin
growth hormone
- growth of muscle
- cartilage
- bone
- liver
- pancreas
- immune system devel
prolactin
- mammary gland development
- milk production
- modulates spermatogenesis
- surfactant synthesis in fetal lung
basophils
- corticotropes: ACTH
- thyrotropes: TSH
- gonadotropes: FSH and LH
tropic hormones
-act on other endocrine organs to realease their product
chromophobes
- not quite sure what these do
- degranulated acidophils/basophils
- folliculostellate cells
folliculostellate cells
- devoid of granules, occupry 10% of the ant pit
- form cell clusters (follicles)
- dendritic morphology
- possess gap junctions that extend to other follicular cells and acidophils/basophils/chromophobes
- functions: paracrine regulation, neuro/immune regulation of inflammation, stem cells maybe
pars intermedia
- part of the anterior lobe
- consists mostly of basophils (corticotrophs)
- synthesizes proopiomelanocortin which is cleaved to form: MSH, beta-endorphin, and ACTH
- contains colloid filled cysts
pituitary portal system
- hypothalamic-hypophyseal portal system
- TRH-thyrotropin releasing hormone
- CRH: corticotropin releasing hormone
- GnRH: gonadotropin releasing hormone
- GHRH: growth hormone releasing hormone
- there is a negative feedback loop once the final hormone is released from the target organ which inhibits both the pit and hypothalamus
posterior lobe
- contains pars nervosa and infundibulum
- neurosecretory organ
- storage and release of ADH and oxytocin
- contains unmyelinated axons, pituicytes (glia)
neurosecretion of the posterior pit
- hormones are stored in herring bodies
- axons terminate near blood vessels
- hormones are coupled to neurophysin (N) 1 and 2
- calcium release stimulates exocytosis
oxytocin
- smooth muscle contraction of the uterus
- myoepithelial cell contraction in the mammary glands
- emotional trust and calmness
ADH (vasopressin)
- increase collecting duct permeability
- vasoconstriction (minor role)
pineal gland
- neuroendocrine gland
- the retina is stimulated by light, nerve impulses are sent to the hypothalamus, norepinephrine is then sent to inhibit the pineal gland
- divided into lobule
- contains pinealocytes and interstitial cells (glial)
- contains calcifications
pnealocyte
- what does is make and when
- what does this product do?
- tryptophan is used to make melatonin
- this pathway is active in darkness
- melatonin participates in circadian rhythms, puberty, and is a powerful antioxidant
two types of calcifications in pineal glands
- corpora arenacea: large, mulberry-like concentrations; hydroxyapetite, protein, glycoprotein; increases with age
- myeloconia: small crystals, calcite, glycoprotein; similar to otoliths of inner ear
composition of islets
-surrounded by exocrine acini
then first inside is the alpha cells then beta cellls are throughout the inside of the organ
beta cells
-produce insulin
delta cells
-somatostatin
gamma cells
pancreatic polypeptide
epsillon cells
-ghrelin
insulin
- synthesized by beta cells in the islets
- released in reasponse to elevated blood glucose
- promotes glucose absorption in muscle and adipose tissue
glucagon
- synthesized by alpha cells in islets
- released in response to low blood sugar
- promotes glycogen conversion to glucose, gluconeogensis
somatostatin
- synthesized by the gama cells in islets
- inhibitory actions: pituitary, GI hormones, endocrine and exocrine pancreas
