Endocrine System PDF

Endocrine system Dr. Tawfiq Omer The Endocrine System Introduction to the Endocrine System The endocrine system works alongside the nervous system. It is a network of glands across the body that secrete chemical messages called hormones. Instead of using nerves (sensory...

Endocrine system Dr. Tawfiq Omer The Endocrine System Introduction to the Endocrine System The endocrine system works alongside the nervous system. It is a network of glands across the body that secrete chemical messages called hormones. Instead of using nerves (sensory and motor neurons) to transmit information, this system uses blood vessels. Different hormones produce different effects (behaviors). Function: Maintains homeostasis, regulates growth, metabolism, reproduction, and response to stress. Difference from the nervous system: Slower but longer-lasting effects.  Structure of the Endocrine System Glands and Organs: Hypothalamus, pituitary, thyroid, parathyroids, adrenal glands, pancreas, gonads, pineal gland, thymus. Hormones: Definition: Chemical messengers secreted into the bloodstream. Mechanism: Act on specific receptors on target cells.  Hypothalamus Location: Brain, below the thalamus. Role: Controls the pituitary gland and links nervous and endocrine systems. Hormones: Releasing hormones: TRH (thyrotropin-releasing hormone), CRH (corticotropin-releasing hormone). Inhibiting hormones: Somatostatin, dopamine. The Pituitary Gland: The Master Gland Location and Structure: Found at the base of the brain, within the sella turcica of the sphenoid bone. Connected to the hypothalamus by the pituitary stalk (infundibulum). Divided into two lobes: Anterior Pituitary Posterior Pituitary  Anterior Pituitary : Comprises glandular tissue and regulates other endocrine glands through its hormones. Major Hormones: Growth Hormone (GH): Stimulates growth, cell reproduction, and repair. Disorders: Gigantism (excess GH in childhood), Acromegaly (excess GH in adults), and Dwarfism (deficiency). Thyroid-Stimulating Hormone (TSH): Stimulates the thyroid gland to produce T3 and T4. Regulates metabolism and energy levels. Adrenocorticotropic Hormone (ACTH): Stimulates the adrenal cortex to release cortisol. Key in stress response and metabolism. Prolactin (PRL): Promotes milk production in lactating women. Plays a role in reproductive health. Follicle-Stimulating Hormone (FSH): Stimulates egg maturation in ovaries and sperm production in testes. Luteinizing Hormone (LH): Triggers ovulation in females and testosterone production in males.  Posterior Pituitary: Comprises nervous tissue and acts as a storage site for hypothalamic hormones. Major Hormones: Oxytocin: Stimulates uterine contractions during childbirth. Promotes milk ejection during breastfeeding. Plays a role in bonding and social behaviors. Antidiuretic Hormone (ADH, also called Vasopressin): Regulates water balance by acting on the kidneys to conserve water. Disorders: Diabetes insipidus (deficiency leads to excessive urination and thirst).  Thyroid Gland Location and Structure: Butterfly-shaped gland located in the front of the neck, below the larynx and around the trachea. Composed of two lobes connected by an isthmus. Made up of follicular cells (secrete thyroid hormones) and parafollicular cells (secrete calcitonin) Hormones: T3 (Triiodothyronine), T4 (Thyroxine): Regulate metabolism. Calcitonin: Lowers blood calcium levels. Disorders: Hyperthyroidism (Graves’ disease), hypothyroidism (Hashimoto’s thyroiditis).  Parathyroid Glands Location: Behind the thyroid gland. Hormone: Parathyroid Hormone (PTH). Function: Increases blood calcium by stimulating bone resorption and increasing calcium absorption in the gut and kidneys. Disorder: Hyperparathyroidism (high calcium) or hypoparathyroidism (low calcium).  Adrenal Glands Adrenal Cortex: Hormones: Cortisol: Stress hormone, regulates metabolism and immune response. Aldosterone: Controls blood pressure by managing sodium and potassium. Androgens: Secondary sexual characteristics. Adrenal Medulla: Hormones: Epinephrine and norepinephrine. Role: Fight-or-flight response. Disorders: Addison’s disease, Cushing’s syndrome  Gonads: Testes and Ovaries Testes: Hormone: Testosterone. Role: Male characteristics, sperm production. Ovaries: Hormones: Estrogen and progesterone. Role: Female characteristics, menstrual cycle, and pregnancy. Pancreas Location and Structure: Located in the abdominal cavity, behind the stomach. Functions as both an endocrine and exocrine gland. Endocrine portion: Islets of Langerhans.  Hormones Produced: Insulin (by Beta Cells): Lowers blood glucose by promoting its uptake into cells. Disorders: Type 1 Diabetes (autoimmune destruction of beta cells), Type 2 Diabetes (insulin resistance). Glucagon (by Alpha Cells): Raises blood glucose by stimulating glycogen breakdown in the liver. Somatostatin (by Delta Cells): Inhibits secretion of insulin and glucagon. Functions: Regulates blood glucose levels. Maintains energy balance between meals. Pineal Gland Location and Structure: Small gland in the brain, located between the two hemispheres in a groove near the thalamus. Hormone Produced: Melatonin: Regulates sleep-wake cycles. Secreted in response to darkness, suppressed by light. THANK YOU