Endocrine system

1. Endocrine system Histology a embryology Curs: Endocrine system

2. Endocrine system • one of regulatory systems • hormone (gr. horman - invite, incite) • chemical messenger produced by endocrine gland and transported to target organ by blood • proteins (polypeptide) - insuline • biogene amins - adrenalin • steroids - estrogens

3. Endocrine system • endocrine glands • diseminated endocrine cells • neuroendocrine cells

4. Endocrine glands • Pituitary gland (gl. pituitaria, hypophysis) • Thyroid gland (glandula thyroidea) • Parathyroid gland(gll. parathyroideales) • Suprarenal gland (gll. suprarenales) • Endocrine pancreas (insulae pancreaticae) • Pineal gland (gl. pinealis - epiphysis)

5. Pituitary gland - characteristic • composed of two lobes • frontal - adenohypophysis • dorsal - neurohypophysis • intimal connection with hypothalamus

6. Pituitary gland - development • Ratke‘s pouch • 3rd week - ceiling of oral cavity • evagination to the diencephalon • separation, proliferation of anterior wall • diencaphalic pouch • origin of dorsal lobe • cells diferetiate to pituicytes

7. Adenohypophysis • distal part (pars distalis) • largest (75%) • tuberal part (pars tuberalis) • cranialy • intermedial part (pars intermedia) • between adeno- and neurohypophysis

8. Distal part • cellular cords, between them capillaries • on HE staining 3 types of cells • acidophils • basophils • PAS-positive • chromophobes • without granules, undiferentiated elements

9. Acidophils in distal part • α - cells (40 - 50%) • large granules, gER • nucleus surrounded by granuleless zone = GC • growth hormone • ε - cells (15 - 20%) • usually small and rare (x gravidity, lactation) • small granules (gravidity - enlargment) • prolactin

10. Bazophils in distal part • β1 - cells • large granules by the cellular membrane • ACTH (β-MSH, Met-enkephalin, endorfin) • β2 - cells • large cells, small granules by the CM • TSH • δ - cells • large cells, medium granules • FSH, LH

11. Tuberal part • surrounds infundibulum • numerous capillaries • most of cells are δ - cells

12. Intermedial part • rudimental • cells in cords • basophils • remnants of Ratke‘s pouch lumen

13. Neurohypophysis • medial eminence (eminentia medialis) • bottom of 3rd brain ventricle • numerous unmyelinisated nerve fibers • infundibulum • unmyelinisated nerve fibers • some of them leads to capillaries • nervous part (pars nervosa)

14. Nervous part • nerve fibers • axons of hypothalamical neurons • Herring bodies - contain secretory granules • secretion of oxytocine and vasopresin • pituicytes • glial cells • capillaries

15. Pituitary gland - blood supply • superior hypophyseal artery • prim. capillary plexus in infundibulum • sec. capillary plexus in adenohypophysis • hypophyseal portal system • inferior hypophyseal artery • capillary network in neurohypophysis

16. Hypothalamus • neurosecretory cells • production of granules and their secretion to blood • paraventricular nucleus - oxytocin • supraoptical nucleus - vasopresin • other nucleuses - liberins and statins • regulation of adenohypophyseal secretion

17. Thyroid gland - characteristic • two lobes, isthmus • metabolic role • thyroxine T4, trijodtyronin T3 • calcitonin

18. Thyroid gland - development • development from 24th day • invagination of entoderm of primitive pharynx • relat. and absol. descent - ductus thyreoglossus • foramen caecum • appearence of lobes (lobus pyramidalis)

19. Thyroid gland - histogenesis • solid endodermal object • ingrowth of surrounding mesenchyme and vessels • ingrowth of ultimobranchial bodies • 10th week - cells make groups • single layer epithelium surrounds lumen • 11th week - production of colloid

20. Thyroid gland - morphology • capsule - septa • follicles (50 - 900 um) • round shape • single layer epith. from follicular cells • contain colloid - thyreoglobulin • follicular cells • parafollicular cells

21. Follicular cells • round nucleus, numerous gER (basal parts), MIT • numerous lysosomes • *thyreoglobulin, production of T4 a T3

22. 1. iodid pump use ATP and pumps iodium from blood to colloid 2. and 3. synthesis of thyroglobulin and peroxidase, stored in one secretory granule, their secretion to colloid by exocytosis 4. iodisation of thyroglobulin by peroxidase in colloid resulting in iodthyroglobulin endocytosis of iodthyroglobulin 5. fusion of primary lysosome with endocytosed vesicle proteolysis of iodthyroglobulin resulting in T3, T4 and other fragments secretion of T3 and T4 to blood circulation 6. binding to the transporting plasma protein (TBG) Synthesis of thyroid hormones

23. Parafollicular cells • C-cells • between follicles (alone or in groups) • larger, lighter • many of ER and GA, MIT • granules - round, dark • production and secretion of calcitonin

24. Parathyroid gland - characteristic • 2 pairs of small rounded bodies • role in metabolism of bones and calcium • parathormon (PTH)

25. Parathyroid gland - development • dorsal parts of 3rd and 4th branchial pouch • 5th week - proliferation of endoderm, losing of lumen • ingrowth of vessel from mesenchyme • chief cells - fetal metabolism of calcium • oxyphil cells - appearence in 7th year after birth

26. Parathyroid gland - morphology • capsule + septa • parenchyme divided on cords • chief cells - medium to large cells (4-8 um) • light cytoplasm • granules contain PTH • oxyphil cells - rare, larger • cytoplasm darker (more acidophilic), no granules, numerous MIT • unclear function

27. PTH connected to osteoblasts  * RANKL (ligand for receptor for activation of nuclear factor kappa) Monocytes reaches an area of bone remodeling (on their surface are receptors forM-CSF) Function ofparathormon PTH connected on osteoblasts  * M-CSF (monocyte collony stimulating factor) Connection of M-CSF on monocyte activates expresion of RANK receptor Connection RANK-RANKL is established (appearence of multinuclear precursor, unable to reabsorb bone) RANK-RANKL connection is inhibited by osteoprotegerin (has greater affinity to receptor, his synthesis in osteoblast in inhibited by PTH) A resting osteoclast (nonfuctional) uncouples from osteoblast. Maturation of cells is completed when the sealing zone and ruffled border appear. (The formation of sealing zone requires integrins)

28. Suprarenal gland - characteristic • „double gland“ • two special tissues - cortex and medulla • mineralocorticoids - aldosteron • glucocorticoids - cortisol, corticosteron • androgens - testosteron • catecholamins - epinephrin, norepinephrin

29. Suprarenal gland - development • cortex - from coelomic epithelium next to the mesenterium • proliferation, moving to the aorta • medulla - from the origin of celiac ganglion • sympaticoblasts, growth to cortical mass • secundar proliferation of cortex - definitive cortex

30. Suprarenal gland - cortex • capsula - septa • fibroblasts, collagenous and elastic fibres, smooth muscle cells • cortex of suprarenal gland • zona glomerulosa - (15%) • zona fascicularis - (65%) • zona reticulosa - (7%)

31. Zona glomerulosa • outer zone • rounded cords of cells • cells producing steroids • between cords are capillaries (sinusoidal) • production of aldosteron

32. Zona fasciculata • medium, widest zone • long paralel cords of cells • in cytopl. numerous lipid droplets • cells producing steroids • between cords are capillaries (again) • production of glucocorticoids and androgens

33. Zona reticulosa • inner zone of cortex • irregular anastomozing cords of cells • small cells with granules of lipofuscin • some elements have pyknotic nucleus • between cells are capillaries (of course) • production of glucocorticoids and andogens

34. Suprarenal gland - medulla • anastomozing cords of polyedric cells • large cells, large nucleus • gER, MIT, GK, granules • epinephrin, norepinephrin, chromogranins, ATP • dopamin-β-hydroxylaseu, Leu- a Met- enkefalin • between cords are capillaries (what else) • rarely - parasympatical ganglious cells

35. Suprarenal gland - blood supply • aa. suprarenales sup., mediae et inf. • subcapsular plexus • capsular, cortical and medullar arteries • in medulla arterial and also venous blood • vena suprarenalis

36. Islets of Langerhans • endocrine part of pancreas • 0,1 - 0,2 mm in size, 1 - 1,5 milions in count • various type of cells - A, B, D, PP (F) • production of: • insulin • glucagon • somatostatin • pancreatic polypeptide

37. I. of L. - development • differentiated from indiferent cells of p. • divided from tubules • first are A-cells, then B, D and PP • insular field - all types are mixed • mantle inslets - B in core, A mantle • insulin in 10th week, glucagon in 15th week

38. I. of L. - morphology • cords of epithelial cells, between them are capillaries (really) • body and tail - 70% B, 20%A, 10%D,1%PP • haed - 65% PP, 25% B, 7% D, 3% A • I. of L. - tail > body > head

39. gER, GA, granules A - cells α - granules - rounded 300 nm glucagon - hyperglycemic-glycogenolytic factor B - cells β - granules - rounded 300 nm,species specifical insulin - hypoglycemic factor I. of L. - cellular types

40. D - cells • δ - granules - rounded 250 nm • one long prominence - paracrine secretion • somatostatin • PP - cells • granules - 180nm, very light • pancreatic polypeptide - regulation of exocrine pancreas • (G - cells) • production of gastrinu

41. Pineal gland • upper dorsal end of 3rd brain ventricle • capsule from pia mater, septa • pinealocytes - main cells • nucleus with expressive nucleolus, bas.cytopl. • production of melatonin • interstitial cells - astroglial cells • rod like nucleus • spherolithi pineales - concrements of protein-like material • count of them elevates with age

42. Disseminated endocrine cells • endocrine cells of GIT • „closed“ type vs. „open“ type • contain numerous granules • many of types = many of hormones • regulation of GIT function