Presentation 17: Endocrine System Flashcards
What are the Functions of the endocrine system
- integrates body functions
- slower than the nervous system, but more sustained
What types of arrangements can endocrine glands be?
GENERAL:
Ductless glands (no opening to outside), usually small and highly vascular that secrete hormones into the circulatory system
Split into Cordal vs Follicular arrangements
- cordal = usually associated w/ blood vessels, include parotid and salivar
- follicular = has cavity (colloid) surrounded by circulatory cells and epithelium made up of parafollicular and follicle cells, ex. thyroid gland
Cordal arrangement
usually associated w/ blood vessels, include parotid and salivar
Follicular arrangement
has inner cavity (colloid) surrounded by circulatory cells and epithelium made up of parafollicular and follicle cells
- ex. thyroid gland
Neurosecretory tissues
Specialized neurons that synthesize and secrete hormones
- extend from hypothalamus to postierior pituitary
- secrete neurohormones
Neurohormones
released by axons of specialized neurosecretory cells into surrounding blood capillaries (i.e. sinusoids)
How do we categorize the Endocrine System?
Embryonic origin!
1. ectodermal origin (i.e. pituitary gland, pineal body, adrenal medulla) = secretes peptides/proteins = amino acid derivatives
2. mesodermal origin (i.e. gonads and adrenal cortex) = secretes steroids = modified lipids
3. Endodermal origin - from pharyngeal pouches (i.e. thyroid, endocrine pancreas, parathyroid, and ultimobranchial bodies)
Ectodermal origin
Secretes peptides or proteins (amino acid derivatives)
- Pituitary gland (hypophysis)
- Pineal body (melatonin)
- Adrenal medulla (stress responses)
Pituitary gland/hypohysis
Divided into Neurohypophysis (post. pituitary) which is an evagination of the infundibulum in the diencephalon, and the Adenohypophysis which is from Rathke’s pouch which is an outgrowth of the mouth cavity
- suspended from diencephalon via the sella turcica (turcic chair) of skull
Neurohypophysis
Posterior pituitary: evagination of infundibulum
- Made up of median eminence (top) and Pars nervosa (post. lobe)
- median eminence absent in lungfish
Secretes:
- arginine-vasotocin (found in all craniates, helps reabsorb water in kidney)
- Vasotocin and vasopresin (thermoregulation)
- oxytocin (milk production and contraction of uterus in mammals)
arginine-vasotocin
(found in all craniates, helps reabsorb water in kidney)
- Vasotocin and vasopresin
(thermoregulation)
oxytocin
(milk production and contraction of uterus in mammals)
Adenohypohysis
From Rathke’s pouch (an outgrowth of the mouth cavity)
- Split into pars intermedia, pars tuberalis, and pars distalis
- pars distalis is most secretory part and controlled by hypothalamus
Secretes:
- Thyrotropin (regulates thyroid gland)
- Adrenocorticotropin (regulates function of adrenal cortex (part of adrenal gland in assoc. w/ kidneys)
- FSH (follical-stimulationg hormone, stimulates growth of ovarian follicle)
- Leutinizing hormone (LH = ovulation and formation of corpus luteum, ICSH = androgen synthesis in testes)
- Somatotropin (growth hormone and imp. for breakdown of fats)
- Prolactin (lactation in mammals)
What is the diversity of the pituitary gland from protochordates to mammals/birds
Protochordates = no homology w/ pituitary gland
Agnathans
- adenohypohysis = not compact but scattered tissue around diff. organs
- neurohypohysis = relatively flat (pars nervosa = absent)
Fishes
- neurohypo = flat + pars nervosa = absent
- adreno + neurohypo = indistinguishable
Lungfishes
- much larger development
- pars nervosa becomes more distinguished
Reptiles
- largest pars intermedia
Mammals
- very small pars intermedia
Birds
- Pars intermedia = absent (func. taken over by pars distalis)