Endocrine Glands

Endocrine System: System of ductless glands that secrete hormones directly into bloodstream.

Hormones: Chemical messengers. Produced in small quantities. Transported by blood. Act on target organs.

Difference from Nervous System: Nervous system - fast, electrical impulses; Endocrine system - slow, chemical messengers.

Exocrine vs Endocrine: Exocrine glands have ducts (salivary glands), Endocrine glands are ductless (thyroid, pituitary).

Functions: (1) Regulation of metabolism, (2) Growth and development, (3) Reproduction, (4) Homeostasis, (5) Stress response.

Diagram Importance: Diagram showing location of endocrine glands in human body is essential for ICSE.

Pituitary Gland: Small pea-sized gland. Located at base of brain in sella turcica.

Structure: Two lobes - Anterior (adenohypophysis) and Posterior (neurohypophysis).

Anterior Pituitary Hormones: (1) Growth Hormone (GH) - promotes growth, (2) TSH - stimulates thyroid, (3) ACTH - stimulates adrenal cortex, (4) FSH - follicle development, (5) LH - ovulation and testosterone production, (6) Prolactin - milk production.

Posterior Pituitary Hormones: (1) ADH (vasopressin) - water reabsorption, (2) Oxytocin - uterine contraction and milk ejection.

Disorders: (1) Gigantism (excess GH in childhood), (2) Dwarfism (GH deficiency), (3) Diabetes insipidus (ADH deficiency).

Regulation: Controlled by hypothalamus via releasing hormones.

Thyroid Gland: Butterfly-shaped gland. Located in neck, in front of trachea.

Hormones: (1) Thyroxine (T4) - regulates metabolism, (2) Triiodothyronine (T3) - active form of T4, (3) Calcitonin - lowers blood calcium.

Functions: (1) Controls metabolic rate, (2) Growth and development, (3) Calcium homeostasis.

Iodine: Essential for thyroid hormone synthesis. Deficiency causes goiter.

Disorders: (1) Hypothyroidism (cretinism in children, myxedema in adults), (2) Hyperthyroidism (Graves' disease, exophthalmia).

Diagram Importance: Labeled diagram of thyroid gland showing follicles is important.

Parathyroid Glands: Four small glands. Located behind thyroid gland.

Hormone: Parathyroid hormone (PTH) - increases blood calcium.

Functions: (1) Increases calcium absorption from intestines, (2) Releases calcium from bones, (3) Reduces calcium excretion by kidneys.

Regulation: Works with calcitonin from thyroid to maintain calcium balance.

Disorders: (1) Hypoparathyroidism - low calcium, tetany, (2) Hyperparathyroidism - high calcium, kidney stones.

Adrenal Glands: Two glands. Located on top of kidneys.

Structure: Outer cortex and inner medulla.

Adrenal Cortex Hormones: (1) Mineralocorticoids (aldosterone) - sodium and water balance, (2) Glucocorticoids (cortisol) - stress response, metabolism, (3) Sex hormones (androgens).

Adrenal Medulla Hormones: (1) Adrenaline (epinephrine) - fight or flight response, (2) Noradrenaline (norepinephrine) - increases heart rate and blood pressure.

Functions: Stress response, blood pressure regulation, metabolism.

Disorders: (1) Addison's disease (cortisol deficiency), (2) Cushing's syndrome (cortisol excess).

Pancreas: Mixed gland. Located behind stomach. Has exocrine (digestive enzymes) and endocrine (hormones) functions.

Islets of Langerhans: Endocrine part. Alpha cells and beta cells.

Hormones: (1) Insulin (beta cells) - lowers blood glucose, (2) Glucagon (alpha cells) - raises blood glucose.

Functions: Regulates blood sugar levels. Insulin promotes glucose uptake by cells.

Diabetes Mellitus: (1) Type 1 - insulin deficiency, (2) Type 2 - insulin resistance.

Regulation: Maintains glucose homeostasis.

Testes: Produce testosterone - male secondary sexual characteristics, spermatogenesis.

Ovaries: Produce estrogen and progesterone - female secondary sexual characteristics, menstrual cycle.

Pineal Gland: Produces melatonin - regulates sleep-wake cycle.

Thymus Gland: Produces thymosin - immune system development (active in childhood).

Hypothalamus: Produces releasing hormones that control pituitary gland.

Negative Feedback: Hormone secretion stops when level reaches optimum. Example: TSH secretion decreases when thyroid hormone increases.

Positive Feedback: Hormone secretion continues until process completes. Example: Oxytocin during childbirth.

Importance: Maintains hormone balance and homeostasis.

Diagram Importance: Diagram showing feedback mechanism in hormone regulation is crucial.

Diabetes Mellitus: High blood sugar. Type 1 (autoimmune), Type 2 (lifestyle). Symptoms: frequent urination, thirst, weight loss.

Goiter: Thyroid enlargement due to iodine deficiency. Prevented by iodized salt.

Gigantism and Acromegaly: Excess GH. Gigantism in children, acromegaly in adults.

Dwarfism: GH deficiency in childhood. Short stature but normal intelligence.

Addison's Disease: Adrenal insufficiency. Symptoms: fatigue, low blood pressure.

Cushing's Syndrome: Excess cortisol. Symptoms: moon face, buffalo hump.

Prevention: Balanced diet, regular exercise, stress management.