The endocrine system consists of glands that secrete hormones directly into the bloodstream, which then travel to target organs. The pituitary gland is located near the hypothalamus and is divided into the anterior and posterior lobes. The anterior lobe secretes trophic hormones that stimulate other glands, while the posterior lobe secretes ADH and oxytocin. Other glands discussed include the thyroid, adrenal glands, pancreas, and pineal gland. The lab will examine the structures and functions of these glands.
3. Endocrine Glands and Hormones
Endocrine glands produce hormones and secrete them
into the bloodstream.
Ductless glands
Hormones then travel through the bloodstream until they
reach their target organ, which they affect in a highly
specific manner.
Hormones only affect the organ(s) that contain a specific
receptor for that hormone; resulting in this highly specific
response once a hormone binds to its target tissue.
6. Pituitary Gland
Attached to the
hypothalamus by the
infundibulum
Divided into two lobes:
Anterior Lobe
Glandular tissue
Posterior Lobe
Neural tissue
7. Anterior Pituitary
1 Hypothalamic neurons secrete
releasing and inhibiting hormones
into primary capillary plexus.
2 Hypothalamic hormones travel
though hypophyseal portal veins to
the anterior pituitary; where they
stimulate or inhibit release of
hormones from the anterior
pituitary.
3 Anterior pituitary hormones are
secreted into secondary
capillaries.
12. Posterior Pituitary Hormones
Anti-diuretic Hormone (ADH)
Also known as vasopressin
Acts upon kidney to promote water re-absorption
Urine volume is decreased
Oxytocin
Stimulates smooth muscle contraction, especially during
parturition (birthing process)
Promotes milk let-down (milk ejection reflex) in females.
13. Adrenal Gland
Adrenal Cortex
Regulated by hormones
Release hormones called corticosteroids
Zona glomerulosa – secretes mineralcorticoids
Regulate Na+ and K+ balance
Aldosterone: Sodium and water retention; while excreting
potassium
Zona fasciculata – secretes glucocorticoids
Regulate glucose metabolism and that of other organic
molecules.
Cortisol: stimulate glucose formation and inhibit utilization of
glucose.
Zona reticularis – secrete sex steroids
Weak androgens like Dehydropepiandrosterone (DHEA)
Adrenal medulla
Regulated by neural innervation
Secretes epinephrine and
norepinepherine
Cause sympathetic-like response
Activate by stress (fight or flight response)
“Girls From Russia Make Good Soup”
16. Pancreas
The pancreas is both an
endocrine and an exocrine
gland.
Endocrine cells are located
in islets of Langerhans.
Alpha cells secrete glucagon
Beta cells secrete insulin
20. Diabetes Mellitus
Type I Diabetes Mellitus [insulin-dependent]
“adolescent-onset diabetes”
Caused by destruction of the beta cells.
Lack of insulin secretion leads to extracellular hyperglycemia and increased
lipolysis
Ketonemia
Diabetic ketoacidosis: a condition of insulin deficiency causing increased hepatic
ketogenesis; occurs in Type I diabetes only.
10% of diabetic population
Type II Diabetes Mellitus [non insulin-dependent]
“maturity-onset diabetes”
Insulin resistance (target cells do not respond normally)
Normal or elevated [insulin] initially; relative insulin deficiency
Most patients obese
90% of diabetic population