1. Outlines of d evelopment of endocrine glands the central nervous system the eye the ear and skin and skin appendages

2. D evelopment of endocrine glands Endocrine system includes: - endocrine glands - hypophysis, pineal, thyroid, parathyroid, adrenal , and islets of Langerhans - endocrine component s of glands with exocrine or other function s - pancreas, gonads, placenta, and kidneys - cells with endocrine function that are scattered in nonglandular organs (as a gut, stomach, trachea, etc.) - e.g. GEP cells

3. Hypophysis

4. Epiphysis

5. Thyroid gland

7. Parathyroid gland

9. Adrenal gland

10. Development of suprarenal glands! The cortex and medulla of the suprarenal glands have different origin. The cortex develops from mesoderm and the medulla from neural crest cells. 6 th week aggregation of mesenchymal cells on each side. The cells that form the fetal cortex are derived from the mesothelial cells lining the posterior abdominal wall. The cells that form the medulla are derived from the adjacent symphatetic ganglion. The cells lie first of the medial side of the cortex and as they become surrounded they start to develop into secretory cells of the suprarenal medulla. Later more mesenchymal cells from the mesothelium enclose the cortex and they become the permanent cortex. Zona reticularis develops in the end of 3 rd year!!

11. Development of the pancreas

14. Endocrine glands- summary hypophysis: adenohypophysis - ectoderm of the stomodeum neurohypophysis - neuroectoderm of the diencephalon (base) epiphysis - neuroectoderm of the diencephalon (roof) thyroid gland - endoderm of the primitive pharynx parathyroid glands - endoderm of pharyngeal pouches (3rd, 4th) adrenal gland: cortex - coelomic mesoderm medulla - neural crest (crista neuralis) Langerhans islets - endoderm of the foregut (duodenum)

15. D evelopment the central nervous system Development of neural tube H istogenesis of neural tube Overwiev of development of the brain and spinal cord Development of cavitis in CNS

16. Development of the neural tube CNS develops from a thickened area of the embryonic ectoderm - neural plate it occurs very early on the dorsal aspect of the embryonic disc cranially to the primitive knob reaching to the oropharyngeal membrane over the notochord on about day 18, the neural plate begins to invaginate along the cranio-caudal axis and forms neural groove limited with neural folds on each side by the end of the third week, the neural folds become to move together and fuse into a neural tube the neural tube separates from the ectoderm and is then located between it and notochord

17. . a t the time when the neural folds fuse, some neuroectodermal cells separate from them and form along the dorsal aspect of the tube single cord - called the neural crest ; it soon divides in the left and right parts that migrate to the dorsolateral aspect of the neural tube n eural crest cells give rise to cells of the spinal ganglia and cells of the autonomic ganglia

18. f rom the beginning, the proximal segment of the neural tube is broadened and correspond s to future brain the narrower caudal one develop s in the spinal cord

19. Histogenesis of the neural tube t he wall of the neural tube is initially composed of a thick pseudostratified columnar epithelium , cells then rapidly proliferate in entire thickness of the wall - but later mitotic activity is reduced only on cells situated near the luminal aspect of the neural tube ; a s a result of this process, the wall of neural tube differentiates into 2 zones: the inner germinative and the outer marginal ones i n the germinative zone the cells continue in their mitotic activity and migrate peripherally finally , the wall of neural tube shows 3-layered structure: - the ependymal layer = ependyma, - the intermediate or mantle layer= gray matter - cells of mantle layer soon differentiate into primitive neurons - neuroblasts and spongioblasts (glioblasts), - the marginal layer = white matter (contains no cells)

20. DEVELOPMENT OF THE SPINAL CORD it develops from the caudal portion of the neural tube in contrast with lateral walls of the neural tube, where cells rapidly proliferate, the dorsal and ventral aspects remain thin l ongitudinal groove - sulcus limitans - divides both lateral walls in the dorsal part - alar plate and ventral part - basal plate cells of mantle layer rapidly proliferate and differentiate in the gray matter Remember: The alar plate - give s rise to dorsal horn, the basal plate - to ventral horn

22. Positional changes of the spinal cord Initially, the spinal cord extends the entire length of the vertebra l canal d uring further development, the vertebra l canal grows more rapidly than spinal cord and its caudal end gradually comes to lie at relatively higher levels i n adults, it usually terminates at the inferior border of the first lumbar vertebra

23. DEVELOPMENT OF THE BRAIN t he brain develops from the cranial part of the neural tube at the fourth week , three primary brain vesicles differentiate : - the forebrain - prosencephalon - the midbrain - mesencephalon - the hindbrain - rhombencephalon During the fifth week, the forebrain and hindbrain divides so that 5 secondary vesicles arise: TELENCEPHALON VENTRICULI LAT.CEREBRI PROSENCEPHALON DIENCEPHALON VENTRICULUS TERTIUS MESENCEPHALON MESENCEPHALON AQUAEDUCTUS CEREBRI METENCEPHALON RHOMBENCEPHALON V ENTRICULUS QUARTUS MYELENCEPHALON

29. D evelopment the eye Development of the retina Development of the external and middle layer of the eye Development of the lens

37. D evelopment the ear Development of the external ear Development of the middle ear Development of the external ear

42. t he otocyst serves a primordium of future membranous labyrinth

43. two divisions are early recognizable: a dorsal or utricular portion , differentiating into the utricle, semicircular ducts and endolymphatic duct and sac and a ventral or saccular portion that gives rise to the saccule and cochlear duct

47. D evelopment the skin and skin appendages Development of epidermis and dermis Development of eccrine sweet glands Development of hairs Development of nails

48. Epidermis i nitially, a single layer of ectodermal cells covers the embryo s tarting from the 2nd month, the ectodermal cells divide and form a superficial protective layer of flattened cells, the periderm or epitrichium at the end of 4th month, the epidermis acquires its definitive arrangement a nd 4 layers are distinguished: basal, spinous, granular and horny layer ; a ll layers of the epidermis -at birth

49. Cells that have been exfoliated during fetal life form part of the vernix caseosa , a white, cheese-like, protective substance that covers the fetal skin During the early fetal period, melanoblasts migrate from the neural crest to the dermoepidermal junction, where they differentiate into melanocytes

51. Eccrine sweat glands develop as solid epidermal downgrowths that extend into the underlying dermis a s buds elongate, their ends become coiled, forming the primordia of future secretory portions of glands

57. a pocrine sweat glands (axilla, pubic region, anal region, areolae) develop from the hair follicle similar as sebaceous glands

58. Development of mammary gland