General Embryology 2

This presentation includes the events occurring during third & fourth week of pregnancy and human development (formation of chorionic villi , trilaminar embryonic disc , notochord , and organogenesis

Transcript

1. Third Week of Pregnancy
2. 3rd Week of Pregnancy 1- Changes in the chorion: Formation of chorionic villi. 2- Changes in the embryonic disc: Formation of trilaminar embryonic disc (Gastrulation).
3. A-Changes in the Chorion (Formation of Chorionic Villi)
4. Chorionic Villi They are projections from the chorion. Chorion: Wall of chorionic vesicle. Layers of chorion: Syncytiotrophoblast, Cytotrophoblast and somatic mesoderm. Time of villi formation: From end of the 2nd week to the end of 3rd week. Types: 1) Primary villi 2) Secondary villi 3) Tertiary villi
5. Primary Chorionic Villi
6. Syncytiotrophoblast Cytotrophoblast Primary chorionic villi
7. Secondary Chorionic Villi
8. Secondary chorionic villi Intervillous spaces Syncytiotropholast Cytotrophoblast Somatic mesoderm Dr. Sherif Fahmy
9. Tertiary Chorionic Villi
10. Structure of Tertiary Villous 1- Syncytiotrophoblast. 2- Cytotrophoblast. 3- Somatic extra-embryonic mesoderm. 4- Fetal blood vessels.
11. Tertiary chorionic villi Intervillous space Syncytiotrophoblast Cytotrophoblast Somatic mesoderm Fetal blood vessels Transverse section in the villous Dr. Sherif Fahmy
12. Fetal blood vessels Intervillous space Syncytiotrophoblast Cytotrophoblast Tertiary villous Somatic mesoderm
13. Cytotrophoblastic Shell
14. Secondary chorionic villi Tertiary chorionic villi
15. Cytotrophoblastic shell Tertiary villi Intervillous space Apices of the villi
16. Intervillous space Cytotrophoblastic shell Tertiary villous
17. Parts of the Tertiary villi 1- Stem (anchoring) villous. 2- Floating (absorbing or free) villi.
18. Floating, free or absorbing villous Parts of Tertiary Villous
19. Parts of Chorion (Wall of Chorionic Vesicle): Chorion is divided into 2 parts according to the fate of tertiary villi that arise from it: 1- Chorion frondosum (chorionic plate) It is the part of chorion in contact with decidua basalis (decidual plate). This part persists as part of placenta. 2- Chorion leave It is the part of chorion which is covered with decidua capsularis. This part fuse with other parts of decidua and degenerate.
20. Chorion frondosum (Chorionic plate) Chorion leave Decidua basalis (Decidual Plate) Decidua capsularis
21. Fate of Chorion
22. Chorion frondosum (Chorionic plate) Chorion leave Decidua basalis (Decidual plate) Decidua capsularis Placenta Fuse and degenerate and leave uterus with placenta after delivery + +
23. Gastrulation It is the transformation of bilaminar disc into trilaminar disc. It begins by formation of: 1- Primitive streak. 2- Primitive node. 3- Invagination. 4- Bucco-pharyngeal membrane. 5- Cloacal membrane.
24. Amniotic cavity Yolk sac Bilaminar embryonic disc Primitive streak & groove Primitive node & pit Cloacal membrane Bucco-pharyngeal membrane Epiblast Hypoblast Amniotic cavity Cranial end Caudal end
25. Invagination
26. Primitive groove Epiblast Hypoblast Flask cells Endodermal cells Invagination Intra-embryonic mesoderm Primitive pit Transverse section of embryonic disc during invagination
27. Bucco- pharyngeal membrane Cloacal membrane Primitive streak Primitive node Epiblast cells that invaginate through primitive groove Notochord Intra-embryonic mesoderm Epiblast cells
28. Change of Shape of Embryonic Disc
29. Changes of the shape of Embryonic disc Oval Pear-shaped Dr. Sherif Fahmy
30. Notochord It is the temporary axial skeleton of the embryonic disc.
31. Amniotic cavity Embryonic disc Secondary yolk sac Amniotic cavity Buccopharyngeal membrane Primitive pit Cloacal membrane Connecting stalk Connecting stalk Notochord under ectoderm Primitive streak LS
32. 1- Pre-Notochordal process
33. Amniotic cavity Ectoderm 1-Pre-notochordal process Primitive pit Primitive streak Connecting stalk Secondary yolk sac Endoderm Bucco-pharyngeal membrane LS Cloacal membrane Dr. Sherif Fahmy
34. Pre-notochordal process Extension of primitive pit cavity into prenotochordal process Primitive streak LS Dr. Sherif Fahmy
35. 2- Notochondral Canal
36. 2-Notochordal canal Allantois LS Roof Floor Ectoderm Endoderm Dr. Sherif Fahmy
37. Notochordal canal TS
38. 3- Neurenteric Canal
39. Amniotic cavity Yolk sac Degeneration of the fused median region of endoderm and floor of notochordal canal Roof of notochordal canal LS Dr. Sherif Fahmy
40. 3-Neurenteric canal LS Dr. Sherif Fahmy
41. 4-Notochordal plate Notochordal plate (roof of the canal) which fuses to endodermal layer. TS Dr. Sherif Fahmy
42. 4- Definitive Notochord
43. TS
44. 5-Definitive Notochord TS Dr. Sherif Fahmy
45. Notochord Ectoderm Intraembryonic mesoderm Endoderm Neural tube Dr. Sherif Fahmy
46. Importance of Notochord 1-It is a temporary axial skeleton of the embryonic disc. 2-During folding, its firmness limits head fold. 3-Vertebral column is formed around it.
47. Fate of Notochord •It is the primitive axial skeleton around which the vertebral column is formed. •It remains in intervertebral disc as nucleus pulposus.
48. Annulus fibrosus Nucleus pulposus Parts of Intervertebral disc
49. Organogenesis (4th to 8th Week) Fate of embryonic disc: 1- Fate of Ectoderm. 2- Fate of Endoderm. 3- Fate of Mesoderm.
50. Fate of Ectoderm
51. Ectodermal layer of embryonic disc is divided into: ➢Neural plate. ➢Neural crest. ➢Surface ectoderm.
52. Neural plate Bucco-pharyngeal membrane Primitive node Neural crest Surface ectoderm Ectodermal Layer
53. (A) Formation of Central Nervous System (Neurulation)
54. Neural groove Neural folds Surface ectoderm Ectodermal Layer
55. 20 days 19 days Dr. Sherif Fahmy
56. 22 days 23 days
57. Transverse section in the region of neurulation Neural fold Neural crest Surface ectoderm Notochord Dr. Sherif Fahmy
58. Dr. Sherif Fahmy
59. Fate of the neural tube •The part of the tube in the vertebral canal forms the spinal cord. •The part of the tube in the skull forms the brain.
60. Forebrain Midbrain Hindbrain Spinal cord
61. Fate of neural crest •Ganglia: Sensory, sympathetic and parasympathetic. •Cells: Chromaffin cells of supra-renal medulla, Schwann cells, glial cells, pigmented epithelium of iris and melanoblasts. •Others: Pia mater, arachnoid mater, enamel of teeth, septa of the heart (between ascending aorta and pulmonary trunk) and some bones of the skull.
62. Derivatives of surface ectoderm -Epidermis layer of skin. -Otic placodes form internal ear. -Lens placodes form lens of the eye. -Peripheral nerves. -Sensory epithelium in ear, nose, eye. -Pituitary gland. -Anterior part of oral cavity and lower ½ of anal canal.