1. Lecture 7 General medicine_3rd semester MICROSCOPIC STRUCTURE, HISTOPHYSIOLOGY AND DEVELOPMENT OF ENDOCRINE GLANDS Hormones – classification Components of the endocrine system Principles of humoral regulation

5. Blood supply: direct arterial supply has only neurohypophysis (from two sets of vessels - superior hypophyseal arteries and inferior hypophyseal arteries ). The adenohypophysis is drained by hypophyseal portal veins , which arise from the primary capillary plexus in the region of the median eminence and infundibular stem

6. Pars distalis is made up of cords of glandular cells among them are blood sinusoids Cells of the pars distalis: - chromophobic cells -10-15% - chromophilic cells – acidophilic cells - 50 % – basophilic cells

9. Acidophils somatotropic cells lactotropic cells by immunohistochemistry: Basophils adrenocorticotropic cells thyrotropic cells gonadotropicFSH cells gonadotropic LH cells

10. Pars intermedia consists of small cystic cavities (residua of Rathke´s pouch that are limited by basophilic and chromophobic cells ; basophils produce MSH - melanocyte-stimulating hormone (in amphibians) - in the human its function is unclear

12. Pars nervosa

13. Infundibular stem: cca 100 000 neurites of nerve cells hypothalamic nuclei (tr. hypothalamohypophysealis) ncl. supraopticus a ncl. paraventricularis (large neurons) ncl. tuberales (nc.hypothalamicus ventromedialis et dorsomedialis, ncl. infundibularis) - small neurons axoterminals end near capillaries of the primary capillary plexus hypothalamic regulatory factors (inhibins and liberins) are transported via vv. portae hypophysis to the pars distalis

14. Development of the hypophysis

15. Epi physis - pineal gland ( corpus pineale ) 0.1 – 0.2 g is of cone-shaped form, 5-8 x 5-5 mm enveloped by a thin capsule with delicate septae dividing the parenchyma into lobules They consist of two cell types: - pinealocytes - They produce and secrete melatonin . They are also in majority and arranged in clumps or clusters; the cells are characterized by lobulated nucleus, prominent nucleoli, and membrane-bound granules in the cytoplasm - interstitial cells - about 5 % (modified astrocytes of fibrilar type) and - non-myelinized nerve fibres and blood capillary plexus Pineal gland of adults contains the calcified concretions called as brain sand or acervulus cerebri (corpora arenacea). The concretions differ from their surrounding by deep staining and concentric appearance Hormone: melatonin - inhibits steroidogenic activity of endocrine cells in gonads + r egulating the circadian rhythms of several biological functions

18. Development of the pineal gland

20. Follicles follicular cells

23. parafollicular cells

25. Development of the thyroid gland The thyroid gland is the first of the endocrine glands to develop in the embryo. 24 days after fertilization. It is derived from the ventral wall of the embryonic pharanx at the site just caudal to the future tounge bud. Here a small thickening early occurs, thyroid primordium (solid mass of endodermal cells.). As the tounge grows the thyroid diverticulum descends down in the neck and is later provided with a lumen; the thyroglossal duct . It becomes solid and the blind end then divides into 2 lobules (right and left) which are connected by an isthmus. By 7th week thyroid gland reaches its final state + definitive position in the neck. and thyroglossal duct normally dissapears except for the proximal part – foramen Caecum and caudal part – from which the pyramidal lobe develops (in about 50 procent of the cases)

27. Development of the thyroid gland

29. chief cells

30. oxyphil cells

31. Development of parathyroid bodies Parathyroide glands derive from the endoderm of third (inferior) and fourth (superior) pharyngeal pouches.

32. Development of parathyroid bodies

33. G landula suprarenalis (suprarenal gland, adrenal gland) paired gland situated at upper pole of each kidney the right is triangular the left semilunar weight of 5 – 7 g capsule cortex – 80 % medulla

34. A schema of the adrenal gland

35. The adrenal cortex: is composed of cord of glandular cells separated by blood sinusoids according to the arrangement of cells in cords - 3 layers of the cortex are distinguished zona glomerulosa zona fasciculata zona reticularis

37. Zona glomerulosa: Is located immediatly under the capsule ; glandular cords are arranged in rounded clusters and curved columns. The cells are supposed to secrete MINERALOCORTICOIDS, from which aldosterone is the most potent..........15% Zona fasiculata: Constitute the middle layer of the cortex in which the glandular cords are parallel to each other but perpendicular to the capsule. The zona fasiculata cells produce GLUCOCORTOCOIDS, which influence the on the carbohydrate metabolism. Hydrocortisone is the mot famous one and important substance of them. Zona reticularis: It is situated cloesest to the medulla and is composed of rounded cells arranged into branching and anastomosing cords or columns. Cells of the zona reticularis secrete small amounts of sex steroids .

39. Blood supply of the adrenal gland

40. Development of the adrenal gland