Overview
This lecture covers the structure and function of the endocrine system as tested on the ATI TEAS Version 7 exam, including key glands, hormones, and their physiological roles.
Major Endocrine Glands & Locations
- The endocrine system includes glands that release hormones directly into the bloodstream.
- Main glands: hypothalamus, pineal, pituitary (brain); thyroid, parathyroid (neck); thymus (chest); adrenal (above kidneys); pancreas (near stomach); gonads—ovaries (females), testes (males).
- Some glands, like the pancreas, have both endocrine and exocrine functions.
Endocrine vs Exocrine Glands
- Endocrine glands secrete hormones into the bloodstream without ducts.
- Exocrine glands use ducts to secrete substances onto surfaces or into cavities (e.g., sweat, mammary glands).
Hormone Composition & Function
- Hormones are made from amino acids (polypeptides) or lipids (steroids).
- Hormones bind to specific cell receptors to trigger cellular actions like growth, enzyme activation, or cell division.
Major Glands and Their Hormones
Hypothalamus & Pituitary Gland
- Hypothalamus controls the pituitary and links the nervous and endocrine systems.
- Posterior pituitary releases oxytocin (uterine contractions) and ADH (kidney water reabsorption).
- Anterior pituitary produces: GH (growth), PRL (milk production), TSH (stimulates thyroid), FSH (gamete production), LH (ovulation and androgen production), ACTH (stimulates adrenal cortex).
Pineal Gland
- Secretes melatonin to regulate sleep-wake cycles (circadian rhythms).
Thyroid & Parathyroid Glands
- Thyroid produces T3 and T4 (regulate metabolism), calcitonin (reduces blood calcium).
- Parathyroid releases parathyroid hormone (PTH) to increase blood calcium.
- Calcium is essential for nerve transmission, muscle contraction, blood clotting, and enzyme/hormone activity.
Thymus Gland
- Produces thymosin, which stimulates T cell production for immune function.
Adrenal Glands
- The adrenal medulla secretes epinephrine and norepinephrine for fight-or-flight response.
- Adrenal cortex releases cortisol (increases blood glucose, stress response) and aldosterone (regulates sodium and potassium in kidneys).
Pancreas
- Produces insulin (lowers blood glucose by allowing cell uptake) and glucagon (raises blood glucose by promoting liver glucose release).
Gonads (Ovaries and Testes)
- Ovaries secrete estrogen (uterine lining, female traits) and progesterone (maintains uterine lining, pregnancy).
- Testes produce androgens, mainly testosterone (sperm production, male traits).
- Hormone concentrations and effects differ by sex.
Key Terms & Definitions
- Endocrine gland — gland that releases hormones directly into blood.
- Exocrine gland — gland that uses ducts to secrete substances.
- Hormone — chemical messenger that influences target cells.
- ADH (Antidiuretic Hormone) — hormone that promotes water reabsorption in kidneys.
- TSH (Thyroid Stimulating Hormone) — hormone that stimulates the thyroid gland.
- FSH (Follicle Stimulating Hormone) — hormone that promotes gamete formation.
- LH (Luteinizing Hormone) — hormone that triggers ovulation or androgen production.
- ACTH (Adrenocorticotropic Hormone) — hormone stimulating the adrenal cortex.
- Insulin — hormone that lowers blood sugar.
- Glucagon — hormone that raises blood sugar.
- Melatonin — hormone regulating sleep rhythms.
Action Items / Next Steps
- Review the anatomy and functions of each endocrine gland.
- Memorize major hormones and their main roles.
- Study differences between endocrine and exocrine glands for exam preparation.