The Glands of the Endocrine System Endocrine Glands

The Glands of the Endocrine System

Endocrine Glands • Hypothalamus • Pituitary – Anterior – Posterior • Thyroid Gland • Parathyroid glands • Adrenal Glands – Cortex – Medulla • Pancreas – Islets of Langerhans • Gonads – Ovaries or – Testes • Pineal gland • Thymus

Hypothalamus • Part of brain – Regulates ANS, sex drive, hunger, thirst, body temperature, etc. – Hormones related to these functions • “Releasing hormones” • Axonal transport to posterior lobe

Anterior Pituitary – TSH (thryoid stimulating hormone) – ACTH (adrenocorticotropic hormone) – – FSH (gonadotropin) LH (gonadotropin) GH (growth hormone) Prolactin-releasing hormone

Anterior Pituitary Imbalances Growth hormone (GH or h. GH) – Promotes mitosis, cell division – Elongation of long bones, etc. – Healing of wounds, lack of h. GH slows growth – Hypersecretion in childhood results in giantism – Hyposecretion in childhood results in dwarfism – Hypersecretion in adult produces acromegaly

Pituitary—Posterior lobe • Oxytocin – Stimulates smooth muscle contraction of uterus & mammary glands, feels of attachment. • ADH – Stimulates water reabsorption in collecting ducts. – Stimulates vasoconstriction (vasopressin) – Lack diabetes insipidus

Posterior Pituitary Imbalances ADH – Hyposecretion produces diabetes insipidus “tasteless” – Excessive thirst and urination Diabetes Insipidus Foundation, Inc.

Thyroid Gland • Located in neck • Composed of follicles that produce: • Thyroxin (T 4) • Triiodothyronine (T 3) – Both “thyroid hormones”, are the body’s major metabolic hormone • Parafollicular cells produce: • Calcitonin – Decreases blood Ca 2+ by depositing it in bones

Thyroid imbalances • Hypothyroidism results in: – Myxedema – Goiter - low levels of iodine – Cretinism • Hyperthyroidism results in: – Graves disease

Parathyroid Glands • Four small glands embedded in posterior of thyroid – Parathyroid hormone (PTH) – Stimulates osteoclasts to release Ca 2+ from bone – Stimulates Ca 2+ uptake from intestine & kidney

Parathyroid Imbalances • Severe hyperparathyroidism causes massive bone destruction • If blood Ca 2+ fall too low, neurons become overactive, resulting in tetany

Adrenal Glands Located on top of each kidney • Cortex – Corticosteroids • Medulla • Epinephrine • Norepinephrine

Adrenal Cortex • Cortex – Mineral corticoids • Aldosterone regulate salt and water balance – Glucocorticoids • Cortisol regulate glucose metabolism and the immune . – Gonadocorticoids system • Androgens • Estrogens

Adrenal Cortex Imbalances • Hypersecretion leads to Cushing’s disease • Hyposecretion leads to Addison’s Disease

Adrenal Medulla • Medulla – The adrenal medulla mediates short–term responses. – Cells are modified neurons (lack axons) • Epinephrine (adrenaline) • Norepinephrine (noreadrenaline) – enable a rapid ( fight-orflight ) response to stress by increasing blood glucose and blood pressure and directing blood to the heart, brain and skeletal muscles.

Pancreas • Consists of two major types of secretory tissues which reflects its dual function – Exocrine gland • secretes digestive juice • localized in the acinar cells – Endocrine gland • releases hormones • localized in the islet cells (islets of Langerhans)

Pancreatic Islets • Approximately a million within the pancreas • Control centers for blood glucose – Insulin from beta cells – Glucagon from alpha cells

Pancreas Imbalances Diabetes Mellitus

Gonads • Ovaries – Estrogen – Progesterone • Testes – Testosterone • Reproductive functions when we study reproductive system.

Pineal gland • Melatonin – Day/night cycles • Timing of sleep, body temperature, appetite • Secretion of melatonin begins with darkness – Participates in setting the body’s clock • Melatonin is a potent antioxidant • Melatonin is high when young and is reduced as we age

Thymus • Thymopoietins, thymic factor, thymosins – Influence development of T lymphocytes

Non-Endocrine Gland Hormones • Stomach (gastrin) • Small intestine (duodenum intestinal gastrin, secretin, cholecystokinin) • Heart (atrial natriuretic peptide) • Kidneys (erythropoietin, active vitamin D 3) • Adipose tissue (leptid, resistin, estrogenlike prostaglandins) • Placenta (human chorionic gonadotropin (h. CG), human placental lactogen, relaxin)

Functions regulated by the Endocrine System • • Growth & Development Healing Water balance Blood Pressure Calcium Metabolism Energy Metabolism Stress Responses Secondary Sex Characteristics

Growth Hormones • Growth hormone-releasing hormone • Human growth hormone (h. GH) • Thyrotropin (TSH) • Thyroxine & triiodothyronine • Calcitonin • Somatostatin (GHIH)

Healing Hormones • Growth hormone-releasing hormone • Human growth hormone (h. GH) • Thyrotropin (TSH) • Thyroxine & triiodothyronine • Calcitonin • Glucagon, Insulin • Erythropoietin

Water Balance & Blood Pressure Hormones • • • ADH Aldosterone Angiotensin II Atrial natriuretic Hormone Epinephrine

Calcium Metabolism Hormones • Calcitonin • Parathyroid Hormone (PTH) • Estrogens/androgens • Growth hormone

Energy Metabolism Hormones • Thyroxine & triiodothyronine • Thyroid-stimulating H. (thyrotropin, TSH) • Epinephrine & norepinephrine • Insulin • Glucagon • Adrenocorticotropic Hormone (ACTH) • Cortisol

Stress Hormones • • Epinephrine & norepinephrine T 4 &T 3 ACTH Cortisol