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)
Pineal body
Synchronized endocrine and non-endocrine activity patterns (ex. birds building nest)
- secretes melatonin
- both stimulate sympathetic responses in the body
Adrenal medulla
adrenal gland (central tissue of mammals)
- differes in structure and function from adrenal cortex
- developed from neural crest cells
- consists of chromaffin cells
- secretes epinephrine (stress response) and norepinephrine (relax)
- both stimulate sympathetic responses in the body
Mesodermal origin
Secrete steroids (modified lipids)
- Adrenals (i.e. adrenal cortex, secrete adrenocorticosteroids)
- Gonads (i.e. ovaries - secrete estrogens, and testes (secrete androgens)
Adrenal Cortex
Interrenal tissue in fishes
- Secretes adrenocorticosteroids
- Cortisone, cortisol, and corticosterone (affects metabolism of carbohydrates breakdown to glucose)
- Deoxycorticosterone (affects metabolism of salt and water)
- Aldosterone (affects metabolism of sodium and potassium)
- Adrenosterone (affects stress response)
Cortisone, cortisol, and corticosterone
(affects metabolism of carbohydrates breakdown to glucose)
Deoxycorticosterone
(affects metabolism of salt and water)
Aldosterone
(affects metabolism of sodium and potassium)
Adrenosterone
(affects stress response)
Ovaries
Secrete estrogens from ovarian follicles
- estradiol and estrone (imp for growth/dev of female genital system and secondary sex characteristics)
Ovulation: ovarian follicle: corpus luteum
- progesterone (maintaining pregnancy and preparing uterine wall)
- relaxin (mammary glands and prepares the pubic area for birth)
Testes
Secrete androgens
- testosterone : produced in interstitial cells (important for growth/dev. of male genital system and secondary sex characteristics)
Endodermal origin
Comes from lining of pharyngeal pouches
- Endocrine pancreas (lowers blood sugar)
- Thyroid gland (from 2nd pharyngeal pouch)
- Parathyroid (3rd/4th pharyngeal pouches)
- Ultimobranchial bodies (post. pair of pharyngeal pouches)
estradiol and estrone
imp for growth/dev of female genital system and secondary sex characteristics
progesterone
maintaining pregnancy and preparing uterine wall
relaxin
mammary glands and prepares the pubic area for birth
Endocrine pancreas
Islands of langerhans in pancreus secrete insulin and glucagon
insulin (converts glucose to glycogen in liver/skeletal muscle to lower blood sugar)
glucagon (converts glycogen to glucose to raise blood sugar)
insulin
(converts glucose to glycogen in liver/skeletal muscle to lower blood sugar)
glucagon
(converts glycogen to glucose to raise blood sugar)
Thyroid Gland
Develops from evagination of 2nd pharyngeal pouch
- highly vascular
- located close to larynx/trachea
- follicular structure (extracellular storage of secretion)
- imp during cell differentiation, metamorphosis, sex. development, molting, feather dev. and shape, and thermoreg.
Coroid has thyroglobulin (iodine rich protein) = precursor of hormones
- hydrolysis = thyroxine (T4) and triodotryonine
Thyroid Gland Diversity
- Homologoys to endostyle of protochordates
- thyroids are paired in amphibians, lizards, and birds
- thyroid is single in lungfish/mammals, but bilobed
- thyroid is single in chondricythys and most reptiles
Parathyroid
From the epithelium of 3rd and 4th pharyngeal pouches
- produces parathormone/parathyroid hormone (imp. in regulating Ca and phosphorous levels in bloodstream aka for muscle function)
Parathyroid diversity
Present only in tetrapods (i.e. fishes and agnathans don’t have it)
Paure, either 2 or 4
Ultimobranchial bodies
Single or paired, develop from post. part of pharyngeal pouches
- Produces calcitonin (regulates calcium levels, blocks removal of calcium from bones)
Ultimobranchial bodies diversity
- Absent in agnathan, primitively present in gnathostomes
- Mammals lacking: cells of last pharyngeal pouch captured into thyroid and in mammals calcitonin produced by parafollicular cells within the thyroid
Transitory hormones
When mammals (placenta / Eutherian mammals)
- estrogen, progesterone, and prolactin are produced
