Understanding Human Endocrine Glands and Hormones
The Endocrine System: Glands and Functions
Endocrine glands are ductless glands that produce hormones, which are released directly into the bloodstream and distributed throughout the body. Key endocrine glands include:
- Pituitary Gland: A small, round gland located below the brain, attached by the pituitary stalk.
- Thyroid Gland: Located in front of the thyroid cartilage of the larynx.
- Parathyroid Glands: Four small glands situated on the dorsal region of the thyroid.
- Adrenal Glands: Two pyramid-shaped glands located on top of the kidneys.
- Pancreas: A digestive organ containing endocrine tissue known as the islets of Langerhans.
- Gonads: Reproductive organs that produce sex cells; testes (male) produce sperm, and ovaries (female) produce eggs.
Pituitary Hormones
The anterior pituitary produces seven hormones as a result of hypothalamic releasing factors:
- Growth hormone
- Thyroid-stimulating hormone
- Adrenocorticotropic hormone
- Follicle-stimulating hormone
- Luteinizing hormone (LH)
- Melanocyte-stimulating hormone
- Prolactin
Thyroid Hormones
Stimulated by pituitary hormones, thyroid follicular cells secrete:
- Thyroxine: Involved in many biochemical processes and activates metabolism.
- Calcitonin: Decreases calcium reabsorption in the kidneys and promotes its elimination in urine.
Parathyroid Hormone
This hormone performs actions antagonistic to calcitonin: it increases calcium reabsorption in the kidneys and gut, increases phosphate excretion in urine, and stimulates bone resorption.
Adrenal Gland Hormones
Secreted under the control of adrenocorticotropic hormone, these include:
- Glucocorticoids (e.g., Cortisone): Regulate carbohydrate, protein, and lipid metabolism.
- Mineralocorticoids: Regulate mineral metabolism.
- Androgens: Male sex hormones.
- Estrogens: Female sex hormones.
- Epinephrine: The primary catecholamine hormone produced in the adrenal medulla.
Pancreatic Hormones
Insulin and glucagon are produced in the islets of Langerhans.