DEVELOPMENT OF PROSENCEPHALON

1. DEVELOPMENT OF PROSENCEPHALON

3. PROSENCEPHALON(FOREBRAIN) • Telencephalon: Rostral part of forebrain • Cerebral Hemispheres • Diencephalon: Caudal & median part • optic cup & stalk • Hypophysis/Pituitary • Thalmus • Hypothalmus • Epiphysis

4. DIENCEPHALON • Roof plate • Alar plates = 2 • Absent floor & basal plates

5. ROOF PLATE & EPIPHYSIS • Roof plate • Choroid plexus of 3rd ventricle • Most caudal part of roof plate develops into epiphysis/ pineal body

6. Pineal body • Appears as epithelial thickening in the midline, but by 7th week it begins to evaginate • Eventually it becomes a solid organ on the roof of mesencephalon • Function: Respond to light and darkness & affect the endocrine and behavioral rhythms • In adults calcium is frequently deposited in the epiphysis and then serve as land marks on radiographs of skull.

8. ALAR PLATES • Forms lateral wall of diencephalon • A groove hypothalamic sulcus divides it into: • Thalamus • Hypothalamus

9. THALAMUS • Thalamus gradually projects into the lumen of diencephalon due to proliferation of cells • Frequently the expansion is so great that two thalami fuse in mid line forming massa Intermedia or Interthalamic connexus

10. HYPOTHALMUS • Forms the lower portions of alar plate • Differentiate into number of nuclear masses that regulate visceral functions • Mammillary body forms a distinct protuberance on the ventral surface of hypothalamus on each side of midline

12. Hypophysis/Pituitary Gland-Ectodermal Develops from two sources: • An ectodermal outpocketing of the stomodeum---- Rathke’s pouch • Downward extension of diencephalon---- the infundibulum

13. Cont… • At 3 weeks Rathke’s pouch appear as evagination that grows dorsally towards infundibulum. • By the end of 2nd month it loses its connection with the oral cavity • Comes to lie in close contact with infundibulum

15. Cont… • Cells in the anterior wall rapidly proliferate and form the ---- anterior lobe/ adenohypophsis. • A small extension of the lobe is pars tuberalis that surrounds the infundibulum • The posterior wall of pouch forms the --- pars Intermedia • Infundibulum give rise to stalk & pars nervosa----posterior lobe/Neurohypophysis

16. Hypophysis/Pituitary Gland-Ectodermal

17. HYPOPHYSEAL DEFECTSCRANIOPHARYNGIOMAS Remnant of Rathke’s pouch

18. Cerebral Hemispheres • Arise by 5th week as bilateral evaginations of lateral wall of forebrain • Interventricular foramen

19. CEREBRAL HEMISPHERES • Middle of 2nd month the basal part/floor of hemispheres begins to grow & bulges into lumen of lateral ventricle & into floor of foramen of Monro • In T.S this rapidly growing region has striated appearance therefore called Corpus striatum • C.H become C-shaped • Choroid plexus develop in the region where wall of hemisphere is attached to roof of diencephalon

20. CORPUS STRIATUM • As the cerebral cortex differentiates the axons passing to & from the cortex (Internal capsule) break the nuclear masses into: dorsomedial portion caudate nucleus ventrolateral portion the lentiform nucleus • Medial wall of C.H fuse with lateral wall of diencephalon

21. CHOROID FISSURE • The Lateral ventricle become C-shaped due to growth & curvature of C.H • The caudal end of each C.H turns ventrally & then rostrally, forming the temporal lobe & in so doing it carries the ventricle (forming temporal horn) & Choroid fissure with it.

22. CHOROID PLEXUS • Choroid plexus protrude in the lateral ventricle along the choroid fissure • The thin medial wall of the C.H is invaginated along the choroid fissure by vascular pia matter to form choroid plexus of temporal horn

24. Growth of cerebral hemispheres • C.H grow in anterior, posterior & inferior directions resulting in formation of frontal, occipital & temporal lobes. • As growth in the region of corpus striatum slows the region b/w frontal & temporal lobes depressed & is called insula • This region is later overgrown by other lobes Which completely covers it at birth.

26. COMMISSURES • Anterior commissure- 1st to appear • Hippocamphal commissure • Corpus callosum- 10th week • Habenular commissure • Posterior commissure • Optic chiasma

30. Congenital anomalies

31. Cranium Bifidum

32. Holoprosecrphaly

33. Schizencephaly

34. Anencephaly

35. Hydrocephalus

36. Arnold Chiari Malformation

37. THANK YOU