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Endocrine System

Endocrine System. ENDOCRINE GLANDS • Secrete hormones directly into bloodstream • Ductless EXOCRINE GLANDS secrete substances through a duct (sweat, salivary, lacrimal and pancreas). Function of the Endocrine System

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Endocrine System

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  1. Endocrine System

  2. ENDOCRINE GLANDS • • Secrete hormones directly into bloodstream • • Ductless • EXOCRINE GLANDS • secrete substances through a duct (sweat, salivary, lacrimal and pancreas)

  3. Function of the Endocrine System • – to secrete hormones – chemical messengers that coordinate and direct target cells and organs.

  4. Hormonal Control • NEGATIVE FEEDBACK • • Drop in hormone level triggers a chain • reaction to increase secretion, for example • 1. Blood level of hormone falls • 2. Brain gets message and sends out • hormone to stimulate gland • 3. Gland stimulates more hormone • 4. When blood levels of hormone increase, • the brain hormones stop

  5. Nervous Control – in some cases, sympathetic • nervous system causes direct release of hormone • from gland (for example, when stress causes the • adrenal medulla to secrete adrenalin)

  6. Hormone Transport in Blood • Water-soluble hormones are transported dissolved in blood plasma. • Others circulate in blood, bound to plasma proteins. • The free hormone diffuses across capillary walls to encounter its target cells.

  7. The Endocrine System • Consists of several glands located in various parts of the body • Specific Glands • Hypothalamus • Pituitary • Thyroid • Parathyroid • Adrenal • Kidneys • Pancreatic Islets • Ovaries • Testes

  8. Hypothalamus • Produces several releasing and inhibiting factors that stimulate or inhibit anterior pituitary’s secretion of hormones. • Produces hormones that are stored in and released from posterior pituitary.

  9. Hypothalamus • Also responsible for: • Regulation of water balance • Esophageal swallowing • Body temperature regulation (shivering) • Food/water intake (appetite) • Sleep-wake cycle • Autonomic functions

  10. PITUITARY GLAND • • Tiny structure the size of a grape • • Located at the base of the brain • • Connected to the hypothalamus • • Divided into anterior and posterior lobes • • The “Master Gland”

  11. Pituitary Gland • Two areas • Anterior Pituitary • Posterior Pituitary • Structurally, functionally different

  12. Anterior Pituitary Lobe • • GROWTH HORMONE –GH(SOMATOTROPIN) - responsible for growth and development • • PROLACTIN – develops breast tissue, • stimulates production of milk after childbirth • • THYROID-STIMULATING HORMONE – TSH - • stimulates thyroxine • • ADRENOCORTICOTROPIC HORMONE (ACTH) – stimulates adrenal cortex

  13. Anterior Pituitary Lobe (cont) • • FOLLICLE-STIMULATING HORMONE (FSH) - • stimulates growth of graafian follicle andproduction of estrogen in females, sperm in males • • LUTEINIZING HORMONE – LH – stimulates • ovulation and formation of corpus luteum, which produces progesterone in females

  14. Posterior Pituitary Lobe • • VASOPRESSIN – converts to ADH • (antidiuretic hormone) in the bloodstream, acts on kidney to concentrate urine and preserve H2O in the body • • OXYTOCIN – released during childbirth • causing contractions of the uterus

  15. THYROID GLAND • • Butterfly-shaped mass of tissue • • On either side of larynx, over trachea • • H-shaped

  16. Thyroid Hormones • • Main hormone – THYROXINE – is controlled • by the secretion of TSH • • Thyroxine controls the rate of metabolism • • CALCITONIN – controls calcium ion concentration in the body, prevents hypercalcemia

  17. PARATHYROID GLANDS • • Four glands, each the size of a grain of rice • • Attached to posterior thyroid • • Produce PARATHORMONE which helps • control blood calcium level, prevents • hypocalcemia

  18. THYMUS • • Endocrine gland and lymphatic organ • • Located behind the sternum, above and in • front of the heart • • Begins to disappear at puberty

  19. ADRENAL GLANDS • • Located on top of each kidney • • Adrenal cortex secretes hormones known at • corticoids – they are anti-inflammatory • • They are: mineralcorticoids, glucocorticoids, • and sex hormones

  20. Adrenal Hormones • • ANDROGENS are male sex hormones • • Adrenal medulla secretes epinephrine • (adrenalin) and norepinephrine • • ADRENALIN is a powerful cardiac stimulent – “fight or flight” hormones that prepare the body for an emergency situation

  21. GONADS • • Ovary in female • • Testes in male • • Estrogen – development of female reproductive organs, secondary sex characteristics • • Progesterone – plays a part in the menstrual • cycle • • Testosterone – male reproductive organs and • secondary sex characteristics

  22. PANCREAS • • Located behind the stomach • • Endocrine and exocrine functions • • Involved in production of INSULIN by ISLETS • OF LANGERHANS • • Insulin – promotes utilization of glucose by the • cells, fatty acid and amino acid transport, and • facilitates protein synthesis

  23. Other Hormones • PROSTAGLANDINS – tissue hormones, can • cause constriction of blood vessels, muscle • contractions. Can be used to induce labor.

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