The Endocrine System

1. The Endocrine System Michael Hall PhD University of California Los Angeles

2. Modes of secretion and action of chemical messengers (hormones) autocrine paracrine endocrine synaptic Chemical messenger target cell receptors target cell

3. Classes of Chemical Messengers • Amino acid derivatives (eg thyroxine, adrenaline) • Small peptides (eg vasopressin, thyroid releasing • hormone) • 3. Proteins (eg insulin, growth hormone) • 4. Steroids (eg cortisol, testosterone, progesterone)

4. Positive and negative feedback control of hormone production

5. Sensory neuronal stimulation Higher brain centers Higher brain centers neurotransmitters neurotransmitters Hypothalamus Hypothalamus CRH TRH Anterior Pituitary Anterior Pituitary TSH ACTH Adrenal cortex Thyroid follicular cells T3/T4 Cortisol Various tissues Adrenal medulla Epinephrine Various tissues

6. Diffuse NeuroEndocrine System The DNES involves a number of isolated cells, or small groups of cells, that are situated throughout the body, but particularly in the digestive, respiratory and urinary systems. These cells, called APUD cells, secrete chemical messengers that generally act in a paracrine manner.

7. The Endocrine Glands Most organs have some endocrine function. The next lectures will deal with organs whose only functions are to secrete hormones: Pituitary Thyroid Parathyroid Adrenal Pancreas* *Pancreas has both endocrine and exocrine functions

8. Pituitary Gland

9. Pituitary hormones and their target organs

10. Development of the pituitary gland hypothalamus median eminence infundibulum (stalk) pars nervosa

12. hypothalamus median eminence pars tuberalis infundibulum (stalk) pars nervosa pars distalis pars intermedia Hypothalamus and Pituitary posterior anterior

13. Hormone production and release by the neurohypophysis (oxytocin) (ADH) (pars nervosa) (pars distalis)

14. Herring body in neurohypophysis Pituicytes (glial cells) Herring body

15. Herring Bodies along a Capillary Secretory granule Axon terminal Capillary

16. hypothalamus median eminence pars tuberalis infundibulum (stalk) pars nervosa pars distalis pars intermedia Hypothalamus and Pituitary posterior anterior

17. Development of the pituitary gland hypothalamus median eminence infundibulum (stalk) pars nervosa

18. Chromophils and Chromophobes in the Adenohypophysis Chromophobes Acidophils Chromophils capillary Basophils

19. hypothalamus median eminence pars tuberalis infundibulum (stalk) pars nervosa pars distalis pars intermedia Hypothalamus and Pituitary posterior anterior

20. Portal veins Pituitary Pars tuberalis and portal veins Pars tuberalis Infundibulum

21. hypothalamus median eminence pars tuberalis infundibulum pars nervosa pars distalis pars intermedia Hypothalamus and Pituitary posterior anterior

23. 1 2 3 4 Hypophyseal portal system

24. Hypophyseal portal veins Pituitary Pars tuberalis and portal veins Pars tuberalis Infundibulum

25. Pituitary hormones and their target organs

26. Thyroid Gland

27. Thyroid and parathyroid glands Parafollicular cell Follicular cell Colloid Thyroid gland Oxyphil cell Chief cell Parathyroid gland

28. Two thyroid lobules separated by CT septum CT F lobule

29. Thyroid Follicles Follicular cells thyroglobulin capillaries Basement membrane

30. Synthesis and iodination of thyroglobulin Release of thyroxine (T3 and T4) A B

31. Iodine deficiency goiter hypothalamus hypothalamus TRH TRH Excess TSH TSH Negative feedback Low Negative feedback Iodine Iodine T3/T4 Low T4

32. Iodine deficiency goiter

33. Parafollicular cells in the thyroid

34. Action of calcitonin and PTH in blood calcium homeostasis Inhibits osteoclasts stimulates osteoclasts

35. Parathyroids are situated on the posterior surface of the thyroid gland Thyroid Parathyroid

36. Parathyroid and thyroid glands Parathyroid

37. Cells of the parathyroid Chief cells Oxyphil cells

38. Interaction of calcitonin and PTH in blood calcium homeostasis Inhibits osteoclasts stimulates osteoclasts

39. Adrenal Gland

40. Adrenal Z. glomerulosa Cortex Z. fasciculata Z. reticularis Medulla Capsule

41. Hormones Mineralocorticoids (e.g. aldosterone) Capsule Z. glomerulosa Glucocorticoids e.g. cortisol Sex hormones e.g. DHEA Z. fasciculata Adrenaline Z. reticularis Preganglionic sympathetic terminal cap Noradrenaline Medulla

42. Adrenal Z. glomerulosa Cortex Z. fasciculata Z. reticularis Medulla Capsule

43. Hormones Mineralocorticoids (eg. aldosterone) Capsule Z. glomerulosa Glucocorticoids (eg cortisone) Sex hormones (eg DHEA) Z. fasciculata Adrenaline Z. reticularis Preganglionic sympathetic neuron cap Noradrenaline Medulla

44. Cells of the adrenal medulla Chromaffin cells Postganglionic parasympathetic neurons

45. Adrenal Blood Supply Subcapsular arterial plexus Capsule Z. glomerulosa. Medullary artery Z. fasciculata. Fenestrated sinusoids Z. reticularis. Medulla. Medullary vein

46. Arterial and Venous blood in Adrenal

47. Pancreas

49. Islet of Langerhans in Pancreas Acinar cells Islet

50. Cells and hormones of the pancreatic islets • b-cells secrete insulin (causes decrease in blood glucose) • a-cells secrete glucagon (causes breakdown of glycogen • and increase of blood sugar) • 3. d-cells secrete somatostatin (has both paracrine [inhibits • release of insulin and glucagon] and endocrine effects • [reduces motility of smooth muscle of gut]) • 4. G-cells secrete gastrin (stimulates release of HCl from • parietal cells of stomach • 5. PP-cells secrete pancreatic polypeptide (inhibits exocrine • secretion of pancreatic enzymes)