Module 11 endocrine glands

endocrine system

-major communicating system in the body

-produces slow acting, but long term responses

-uses chemical messengers called hormones

functions of the endocrine system

-involved in a diverse array of processes but major processes include

=reproduction

=growth and development

=chemical homeostasis

=cellular metabolism

=mobilization of body defenses

glands

exocrine and endocrine

exocrine gland

carry substances to body surface using ducts

endocrine gland

-lack ducts and release hormones into the surrounding ECF to be taken up by the blood stream

=hypothalamus

=pancreas

=gonads and placenta

=pituitary gland

=thyroid gland

=parathyroid gland

=adrenal gland

glandular secretion

autocrine, paracrine, hormones

autocrine

exerts effects on the same cells they are secreted by

paracrine

act locally but within the same tissue

hormones

long distance chemical messengers through bloodstream

hormone classifications

amino acid based

steroids

eicosanoids

amino acid based hormones

includes most hormones, variable in size usually as peptides, water soluble and cannot pass lipid bilayer

steroids

synthesized from cholesterol, includes gonadal and adrenocortical hormones, lipid soluble and can pass lipid bilayer

eicosanoids

lipid based that act as paracrine and autocrine

hormone action

-hormones must have a receptor (can be intra or extracellular)

-hormones can act on a cell in a variety of ways

=alter plasma membrane permeability

=stimulate synthesis of enzymes or proteins

=activate or deactivate enzymes

=induce secretory activity

=stimulate mitosis

ultimobrachial body

-paired cell masses in non-mammalian vertebrates (except cyclostomes)

-secrete calcitonin

-is incorporated into thyroid gland (parafollicular) in mammals

thyroid gland

-subpharyngeal gland in amphioxus

-secretes thyroxine (T4) and triiodothyronine (T3) which are iodine based hormones

-secretes calcitonin from parafollicular cells outside of the follicle (inhibits osteoclast activity; lowers blood Ca2+ levels)

-permissive hormones: allow cells to respond more readily to other hormones

-functions include:

=elevation of oxygen consumption (endotherms);only at certain temps in ectotherms

=increased basal metabolic rate

=regulates tissue growth and development

=metamorphosis

=maintains blood pressure

=molting

=reproductive maturity

=

parathyroid gland

-in close association with thyroid

-Chief cells: parahormone (parathyroid hormone; raises blood Ca2+ levels)

-Oxyphil cells (mammals only): unknown function

adrenal gland

-on top of kideny

-two separate sources

=adrenocortical tissue: corticosteroid hormones

=chromaffin tissue: catecholamines (norepinephrine and epinephrine)

-teleost's: chromaffin tissue remains separate; corpuscles of Stannius release stanniocalcin (lower blood calcium levels)

adrenal gland layers

capsule > zona glomerulosa > zona fasciculata > zona reticulata > adrenal medulla

zona glomerulosa

superficial layer that produces mineralocorticoids (mineral balance; aldosterone; retention of sodium and water)

zona fasciculata

medial layer that produces metabolic corticoids called glucocorticoids (cortisol; stimulates gluconeogenesis and glycogen breakdown)

zona reticularis

produces gonadocorticoids (progestogens and androgens)

adrenal gland development

hypothalmus

-close interaction with pituitary

-anterior pituitary control

=hypothalamic hormones

-posterior pituitary control

=action potentials generated in hypothalmus

pituitary gland

-4 main parts

pars tuberalis

-outgrowth of pars distalis

-unknown function

pars distalis

-anterior pituitary

-composed of glandular tissue

-releases a variety of hormones

=growth hormones

=prolactin

=follicle stimulating hormones

=luteinizing hormones

=thyroid stimulating hormones

=adrenocorticotropin

-vascular connection via capillary plexus and hypophyseal portal veins

pars intermedia

-region adjacent to pars nervosa

-produces intermedin (MSH) in chondrichthyans, amphibians and reptiles

-poorly developed in primates and absent in birds and some mammals

pars nervosa

-mostly neural tissue

-releases neurohormones

-releases vasopressin (ADH) and oxytocin

pancreatic islets

-Brockmann bodies in fishes (isolated masses along GI accessory organs)

-tetrapod's inlets distributed evenly throughout pancreas

=beta cells: produce insulin (lowers blood glucose)

=alpha cells: produces glucagon (raises blood glucose)

=delta cells: produces somatostatin (inhibits secretion of insulin and glucagon)

=pancreatic polypeptide cells (PP cells): produce pancreatic polypeptides: (promotes flow of gastric juices)

pineal gland

-considered a vestige of median eye

-produces melatonin

Gi tract

-enteroendocrine cells release paracrines

=gastrin

=secretin

=enterogastrone

=cholecystokinin

=enterocrinin

kidneys

-juxtaglomerular cells release renin

-initiates the renin-angiotensin cycle

gonads

-ovary

=ovaries produce estrogen (granulosa cells) and progesterone (CL)

-testes

=testes produce testosterone (leydig cells)

adipose tissue

-releases leptin

heart

-cardiac muscle cells secrete ANP (atrial natriuetic peptide)

-reduces aldosterone secretion

-increases sodium excretion in kidneys

skin

-produces cholecalciferol which is converted to vitamin D3

-necessary for calcium absorption

thymus

-produces thymulin, thymopoitins, and thymosins which upregulate T-lymphocyte production

growth hormones

-adenohypophysis

-para distalis

prolactin adenohypophysis

-para distalis

thyrotropin

-adenohypophysis

-para distalis

follicle stimulating hormone

-adenohypophysis

-para distalis

luteninzing hormone

-adenohypophysis

-para distalis

corticotropin

-adenohypophysis

-para distalis

melanotropin

-adenohypophysis

-para intermedia

vasopressin

-neurons projecting to neurohypophysis from paraventricular and supraoptic nuclei of hypothalamus

oxytocin

-neurons projecting to neurohypophysis from paraventricular and supraoptic nuclei of hypothalamus

parathyroid hormone

-parathyroid

-chief cells

thyroxine

-thyroid

-principle cells

triiodothyronine

-thyroid

-principle cells

calcitonin

-thyroid

-parafollicular cells

aldosterone

-adrenal cortex

-zona glomerulosa

glucocorticoids

-adrenal cortex

-zona fasciculata, zona reticularis

androgens

-adrenal cortex

-zona reticularis

noreepinephrine

-adrenal medulla

-chromaffin cells

epinephrine

-adrenal medulla

-chromaffin cells

insulin

-pancreatic islets

-beta cells

glucagon

-pancreatic islets

-alpha cells

somatostatin

-pancreatic islets

-delta cells

pancreatic polypeptide

-pancreatic islets

-PP cells

cholecytokinin

-duodenum

-intestinal mucosa

secretin

-duodenum

-intestinal mucosa

testosterone

-testis

-interstitial cells

estradiol ovary

-ovary

theca interna, interstitial cells, granulosa cells possibly

progesterone

-ovary

-CL, theca interna

other follicular estragenic steroids in smaller amonds

-ovary

chorinic gonadotropin

-placenta

-syntrophoblast

estradiol

-placenta

-syntrophoblast

estriol

-placenta

-syntrophoblast

adrenal corticoids

-placenta

-syntrophoblast

placental lactogen

-placenta

-syntrophoblast

prolactin

-placenta

-syntrophoblast

ACTH- like substances

-placenta

-syntrophoblast