1. Introduction to the Endocrine System
- The endocrine system consists of glands that produce and release hormones into the bloodstream.
- It regulates metabolism, growth, reproduction, and homeostasis.
- Endocrine glands are ductless and secrete hormones directly into the blood.
- Major endocrine glands include the pituitary, thyroid, adrenal, pancreas, and gonads.
2. Pituitary Gland - The Master Gland
- Located at the base of the brain and controls other endocrine glands.
- Divided into anterior and posterior lobes.
- Hormones secreted by the anterior pituitary:
- Growth Hormone (GH): Stimulates body growth.
- Thyroid-Stimulating Hormone (TSH): Regulates the thyroid gland.
- Adrenocorticotropic Hormone (ACTH): Stimulates adrenal glands.
- Follicle-Stimulating Hormone (FSH): Promotes sperm and egg production.
- Luteinizing Hormone (LH): Stimulates ovulation and testosterone production.
- Prolactin (PRL): Stimulates milk production in females.
- Hormones secreted by the posterior pituitary:
- Oxytocin: Induces labor contractions and milk ejection.
- Antidiuretic Hormone (ADH): Regulates water balance in the body.
3. Thyroid Gland
- Located in the neck and regulates metabolism.
- Secretes:
- Thyroxine (T4) & Triiodothyronine (T3): Regulate metabolism and energy production.
- Calcitonin: Lowers blood calcium levels.
- Hypothyroidism causes weight gain and lethargy.
- Hyperthyroidism causes weight loss and increased heart rate.
4. Parathyroid Glands
- Four small glands behind the thyroid.
- Secretes Parathyroid Hormone (PTH), which increases blood calcium levels.
5. Adrenal Glands
- Located on top of the kidneys.
- Divided into:
- Adrenal Cortex: Secretes:
- Cortisol: Regulates metabolism and stress response.
- Aldosterone: Controls sodium and potassium balance.
- Adrenal Medulla: Secretes:
- Adrenaline (Epinephrine): Increases heart rate and prepares for "fight or flight".
- Norepinephrine: Maintains blood pressure.
- Adrenal Cortex: Secretes:
6. Pancreas - Dual Function Gland
- Acts as both an endocrine and exocrine gland.
- Secretes:
- Insulin: Lowers blood sugar levels.
- Glucagon: Increases blood sugar levels.
- Diabetes Mellitus results from insulin deficiency.
7. Pineal Gland
- Located in the brain.
- Secretes Melatonin, which regulates the sleep-wake cycle.
8. Gonads - Sex Glands
- Testes (Males): Secrete testosterone, responsible for male secondary sexual characteristics.
- Ovaries (Females): Secrete:
- Estrogen: Develops female secondary sexual characteristics.
- Progesterone: Supports pregnancy.
9. Thymus Gland
- Located in the chest, important for immune function.
- Secretes Thymosin, which aids in T-cell development.
10. Summary of Major Endocrine Glands and Their Hormones
| Gland | Hormones | Function |
|---|---|---|
| Pituitary | GH, TSH, ACTH, FSH, LH, PRL, ADH, Oxytocin | Controls growth, metabolism, reproduction, and water balance. |
| Thyroid | T3, T4, Calcitonin | Regulates metabolism and calcium levels. |
| Adrenal | Cortisol, Aldosterone, Adrenaline | Controls stress response, blood pressure, and metabolism. |
| Pancreas | Insulin, Glucagon | Regulates blood sugar levels. |
| Gonads | Testosterone, Estrogen, Progesterone | Regulates sexual development and reproduction. |
| Pineal | Melatonin | Regulates sleep cycle. |
11. Conclusion
- The endocrine system plays a vital role in body regulation.
- Hormones maintain homeostasis, metabolism, and reproduction.
- Disorders like diabetes, thyroid dysfunction, and adrenal diseases affect normal functions.