Unit 18: Endocrine System Flashcards
(13 cards)
Overview of the endocrine system
- includes ductless glands and endocrine tissues w/in other organs
- secrete chemical signals called hormones which travel in the circulation and bind to receptors on/within target cells to initiate a change in the cell (a response)
- target cell = cell w/ receptor specific for that hormone
What are the 3 hormone classes?
1) Steroids
- synthesized (made) from cholesterol
- testosterone, estrogen, vitamin D
2) Hormones derived from amino acids (e.g. formed from
tyrosine)
a) thyroxine/T4 = thyroid hormone that controls cellular
metabolism, growth, and development
b) epinephrine and norepinephrine (adrenaline and
noradrenaline) = secreted by adrenal medulla as part of
fight/flight stress response and sexual climax (orgasm)
3) Peptide and protein hormones
- chains of amino acids held together by peptide bonds
- e.g. oxytocin, antidiuretic hormone (ADH), growth hormone (GH), insulin
What are the 4 types of endocrine glands?
Pituitary, thyroid, parathyroid, and adrenal
General info on pituitary gland
= suspended from hypothalamus
- in sella turcica of sphenoid bone
- 2 lobes = anterior pituitary and posterior pituitary
Info about anterior pituitary lobe of pituitary gland
Glandular epithelial tissue - anterior pituitary hormone secretion regulated by hormones released by the hypothalamus. Secretes the following hormones:
i. Growth Hormone (GH) - affects growth and metabolism
ii. Thyroid Stimulating Hormone (TSH) - stimulates secretions
by the thyroid gland
iii. Adrenocorticotropic Hormone (ACTH) - stimulates
secretion of steroid hormones from the adrenal gland
iv. Gonadotropins = reproductive hormones:
a) Luteinizing Hormone (LH) - stimulates ovulation and
formation of corpus luteum in the ovary; stimulates
testosterone production by interstitial endocrine (Leydig)
cells in the testes
b) Follicle Stimulating Hormone (FSH) - stimulates
sustentocytes and follicle cells
v. Prolactin (PRL) - stimulates milk production by mammary
glands
Info on thyroid gland
Butterfly shaped gland on anterior surface of the superior part of the trachea (inferior to larynx). Thyroid histology:
a) Follicles
- walls of the follicles are composed of epithelial (follicular)
cells that secrete the hormone thyroxine (T4)
- thyroxine is converted to its active form (T3) in target cells
b) Parafollicular cells
- btw. follicles and secretes calcitonin (increase Ca++
uptake into bone [bone formation] which lowers blood
Ca++)
Info about parathyroid glands
- 4 (usually) glands embedded in posterior thyroid
- secrete parathyroid hormone (PTH), which acts on bone
and kidneys to increase blood calcium levels
Info about adrenal glands
Located on superior surface of each kidney. Parts:
a) adrenal cortex (outer)
- epithelial tissue forming glands
- secretes only steroids
- 3 layers (a single class of hormones is secreted by each
layer):
i. Zona glomerulosa
- mainly secretes aldosterone, which acts on nephrons to
regulate salt balance
ii. Zona fasciculata
- secretes mainly cortisol, which regulates many body
processes during long-term stress
iii. Zona reticularis
- secretes androgens (sex hormones), which converted to
testosterone or estrogens in other tissues
b) adrenal medulla (inner)
- modified nervous tissue
- synthesizes hormones that regulate “fight or flight”
response
- Epinephrine (80%) = majority
- Norepinephrine (20%) = minority
What are the 3 main endocrine tissues?
Hormone secreting cells or tissues located in organs that have other functions (i.e. are not strictly glands that secrete hormones): Pancreatic Islets of Langerhans in Pancreas, hypothalamus (part of the brain), and the gonads
Info about the Pancreatic Islets of Langerhans in Pancreas
Includes:
- a(lpha)-cells = secrete glucagon, which increases blood glucose concentration
- b(eta)-cells = secrete insulin, which decreases blood glucose concentration
Info about hypothalamus (part of brain)
Produces and secretes hormones that stimulate or inhibit the secretion of hormones from the anterior pituitary:
a) GHRH (Growth Hormone Releasing Hormone)
b) GHIH (Growth Hormone Inhibiting Hormone; aka somatostatin)
c) GnRH (Gonadotropin Releasing Hormone) - for FSH and LH secretion
Produces hormones that are stored and secreted by the posterior pituitary.
Info about the gonads
a) testes = interstitial endocrine (Leydig) cells - secrete testosterone
b) ovaries = granulosa cells of secondary and vesicular follicles secrete estrogen
- corpus luteum secretes estrogen and progesterone
What are some other organs that are endocrine-secreting tissues?
- duodenum = stimulates secretin; cholecystokinin (CCK)
- kidney = renin, erythropoietin (EPO)
- skin = vitamin D
- heart = atrial natriuretic peptide (ANP)
- etc.
