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Endocrine System

Endocrine System. Objectives. 1. Identify organs belonging to the endocrine system. 2. Describe the categories of hormones and the probable mechanism of operation of each type. Objectives.

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Endocrine System

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  1. Endocrine System

  2. Objectives • 1. Identify organs belonging to the endocrine system. • 2. Describe the categories of hormones and the probable mechanism of operation of each type.

  3. Objectives • 3. Identify hormones, their organ of secretion, the type of molecule their structure represents, their primary target organ, the effect of the hormone on the body, and any pathologies associated with the deficiency or excess of the hormone.

  4. Objectives • 4. Describe the location, histology and products associated with: the pituitary (review), pancreas (review), adrenal, thyroid, parathyroid, pineal and thymus. • 5. Define and use the correct terminology associated with the endocrine system.

  5. Endocrine System

  6. Hormone Types • Amino acid • Steroid

  7. Amino Acid • Includes amines, catecholamines, peptides and proteins • Receptors on cell membrane

  8. Amino Acid • Superficial hormone-receptor molecule stimulates intracellular enzyme activity influencing cellular metabolism • Examples • thyroid, all pituitary hormones, norepinephrine, calcitonin, parathormone, insulin, glucagon

  9. Steroid • Receptors in cytoplasm • Structurally related to cholesterol

  10. Steroid • Cytoplasmic or nuclear hormone-receptor complex interacts with DNA stimulating mRNA activity and protein synthesis within the cytoplasm • Examples • estrogen, testosterone, progesterone, gonadocorticoids, cortisol, aldosterone

  11. Endocrine Organs • Pituitary (see unit 10) • Pineal (see unit 10) • Pancreas (see unit 7) • Gonads (see unit 13) • Adrenal • Thyroid • Parathyroid • Other

  12. Adrenal • 4-5 grams • 4cm x 2.5 cm x 1 cm • Surrounded by fibrous capsule • Two regions • Medulla • Cortex

  13. Adrenal Gland

  14. Adrenal Medulla • Derived from ectoderm. • Contains chromaffin cells (pheochromocytes)

  15. Adrenal Medulla • Innervated by sympathetic n.s. • Produces epinephrine & norepinephrine (catecholamines). • Pathology. • pheochromocytoma - 8 blood pressure, BMR, sympathetic response. • neuroblastoma - malignant tumor metastasizing to bone.

  16. Pheochromocytoma

  17. Adrenal Cortex • Derived from mesoderm • 80% of adrenal gland • Three subdivisions (deep to superficial) • Zona reticularis • Zona fasciculata • Zona glomerulosa

  18. Adrenal Histology

  19. Zona Reticularis • Produces gonadocorticoids/androgens

  20. Zona Fasiculata • Thickest region • Specific target of ACTH • Produces glucocorticoids- cortisone, cortisol, corticosterone • Stimulates gluconeogenesis, mobilizing fats, liver glycogen and increasing blood glucose

  21. Zona Glomerulosa • Outermost • Produces mineralcorticoids – aldosterone • Stimulates Na+ reabsorption, K+ secretion by kidney affecting urine concentration and volume 8Aldosterone 8Na+ secretion 8 H2O reabsorption9 urine volume

  22. Adrenal Cortical Pathologies • Addison’s disease - hyposecretion of glucocorticoids due to lack of response to ACTH; symptoms include weight loss, weakness, hypoglycemia, skin bronzing due to increased activity of melanocytes

  23. Addison’s Disease

  24. Adrenal Cortical Pathologies • Cushing’s syndrome - hypersecretion of glucocorticoids, suppressed glucose metabolism; caused by hypersecretion of ACTH or tumor, immunosuppressive drugs in transplant; symptoms include fat redistribution (pendulous abdomen, puffy face, humpback), reduced muscle mass, strength

  25. Cushing’s Syndrome

  26. Adrenal Cortical Pathologies • Aldosteronism - Na+ retention, K+ depletion; symptoms include edema, abnormal cardiac, kidney and neural function due to ion imbalance • Hypoaldosteronism - excessive Na+ and H2O loss; symptoms include low BP, abnormal neural and muscular functions • Adrenogenital syndrome- hypersecretion of gonadocorticoids; symptoms include virilism in females & children, gynecomastia in males

  27. Thyroid • ~25 g, size and shape variable • Two lobes connected via isthmus • Located anterior to thyroid cartilage of larynx

  28. Thyroid Gland

  29. Thyroid • Two types of cells • Follicular • Parafollicular

  30. Thyroid Histology

  31. Thyroid Follicular Cells • Follicular - forming follicles • Produce thyroglobin protein suspended in colloid of follicles • Thyroglobin converted into thyroid hormones • thyroxine /TX/T4/tetraiodothyronine • T3/triiodothyronine

  32. Follicular & Parafollicular Cells

  33. Thyroid • Parafollicular cells/C cells • Outside of follicles • Produce thyrocalcitonin • Regulates Ca+ concentration by 9 bone reabsorption of Ca+, stimulating osteoblasts, 9 Ca+ reabsorption by gut and 8 Ca+ excretion by kidney

  34. Thyroid Pathology • Hypothyroidism • Adult • myxedema • Child • cretinism

  35. Myxedema • Symptoms/signs • facial swelling, • fatigue, • sensitivity to cold, • skin dehydration, • hair loss, • lethargy, • && more frequently affected than %%

  36. Cretinism • Symptoms/signs • poor CNS development • retardation • poor skeletal development • delayed puberty

  37. Cretinism

  38. Thyroid Pathology • Goiter - enlargement of thyroid gland. • simple due to low iodine, enlargement an attempt to increase thyroxine output.

  39. Goiter

  40. Thyroid Pathology • Hyperthyroidism/thyrotoxicosis. • BMR BP and heart rate increase, • Flushing. • fatigue. • Graves disease includes above plus. • Goiter. • bulging eyes (exophthalmos). • && more frequently affected than %%.

  41. Parathyroids • 4 small spherical masses embedded in posterior thyroid gland • Chief cells produce PTH/parathormone/parathyroid hormone

  42. Parathyroids

  43. Parathyroids • Works in conjunction with thyroid gland parafollicular cells - thyrocalcitonin to regulate blood calcium

  44. Parathyroid/Thyroid • Calcitonin (from parafollicular thyroid) • blood calcium decrease • bone reabsorption decrease • PTH • blood calcium increase, • bone reabsorption increase, • blood phosphate decrease

  45. Parathyroid Pathology • Hypoparathyroidism • low blood Ca+ concentrations • hypocalcemic tetany • convulsions • hyperexcitable CNS

  46. Parathyroid Pathology • Hyperparathyroidism • increased bone reabsorption • elevated blood calcium • calcification of soft tissues • kidney stones • pathological fractures

  47. Other Endocrine Tissues • Gut (see unit 7) • gastrin, cholecystokinin, secretin, enterocrinin • Kidneys • erythropoietin - stimulates RBC production • renin - regulates blood pressure • Placenta • estrogen and progesterone

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