The Endocrine System: Glands, Hormones, and Their Vital Functions
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The Endocrine System
The endocrine system is comprised of glands that produce protein substances called hormones. These hormones act as chemical messengers, speeding up or slowing down various activities within the body's cells.
Types of Glands
Exocrine Glands
Exocrine glands release substances through ducts to specific locations. These substances include enzymes, oil, and sweat. Examples include:
- Salivary glands
- Sweat glands
- Oil glands
- Gastric glands
- Intestinal glands
Endocrine Glands
Endocrine glands produce and secrete hormones directly into the bloodstream, acting on target cells throughout the body. Examples include:
- Pituitary gland
- Thyroid gland
- Adrenal glands
- Ovaries
- Testes
Hormones: Action and Functions
Hormones act on specific target cells by binding to receptors. These receptors can be found on the cell membrane, within the nucleus, or in the cytoplasm.
Key Functions of Hormones
- Regulate vital physiological processes
- Regulate growth, development, and behavior
- Regulate reproduction
- Regulate homeostasis and metabolism
- Regulate water and mineral balances
- Regulate stress response
Major Endocrine Glands
- Hypophysis (Pituitary gland)
- Pancreas
- Pineal gland
- Thymus
- Thyroid gland
- Parathyroid glands
- Adrenal glands
- Gonads (Ovaries and Testes)
Types of Hormones
- Amino Acid-Based Hormones: Water-soluble hormones made of amino acid proteins.
- Steroid Hormones: Lipid-based hormones, derived from cholesterol, and fat-soluble.
- Prostaglandins: Lipid compounds that act as local chemical messengers, often associated with pain and inflammation when cells are disturbed.
Specific Gland Functions and Hormones
- Hypothalamus: Coordinates activities of the nervous system and endocrine system by controlling the pituitary gland (often called the "master gland").
- Thyroid: Produces Thyroxine, which regulates metabolism.
- Pancreas: Produces Insulin, which controls glucose levels in the blood.
- Parathyroid Glands: Produce Parathyroid Hormone (PTH), which regulates calcium levels in the blood.
- Ovary: Produces Progesterone, which prepares the uterus for pregnancy.
- Adrenal Medulla: Produces Epinephrine (adrenaline), which increases during stressful situations.
- Pituitary: Produces FSH (Follicle-Stimulating Hormone), which stimulates ovulation.
- Testes: Produce Testosterone, which develops male sexual characteristics.
- Pineal: Produces Melatonin, which regulates sleep patterns.
Note: Mature T-cells (white blood cells) are part of the immune system, though their function can be influenced by endocrine hormones.