Embryology 6 PDF

Development of the extra- embryonic mesoderm Slide 4 Development of the extra- embryonic mesoderm Slide 5 Development of the extra-embryonic mesoderm New cells appear between the yolk sac and the cytotroph...

Development of the extra- embryonic mesoderm Slide 4 Development of the extra- embryonic mesoderm Slide 5 Development of the extra-embryonic mesoderm New cells appear between the yolk sac and the cytotrophoblast They form a layer of loose connective tissue: extraembryonic mesoderm. Slide 6  Development of the extra- embryonic mesoderm Cavities or spaces appear in the extra-embryonic mesoderm Slide 7  Development of the extra- embryonic mesoderm The cavities form a new space- the chorionic cavity Slide 8 Development of the extra-embryonic mesoderm Slide 9 Development of the extra-embryonic mesoderm The primitive yolk sac is pinched off- a secondary is formed The cavity divides the extraembryonic mesoderm into the 1. Extraembryonic somatic mesoderm- lining trophoblast and amnion 2. Extraembryonic splanchnic mesoderm- lines the yolk sac Slide 10 Slide 11  Chorion The chorion is formed by 1. Extraembryonic somatic mesoderm 2. Cytotrophoblast 3. Syncytiotropho-blast The chorion forms the wall of the chorionic cavity- the amniotic cavity and yolk sac are suspended in the chorionic cavity by the connecting stalk. Slide 12 Slide 13 Slide 14 Slide 15 So, it is considered as the fourth primary germ layer Neural crest derivatives Which one is the derevative of the ectoderm ? Primordial heart. Epidermis of skin. Dermis of skin. Liver. The notochord induces the development of : The respiratory system. The cardiovascular system. The central nervous system. The urogenital system. Which one of following is a derivative of the neural crest ? Spinal cord. Spinal ganglia. Lens of eye. Blood cells.  Results of folding 1-yolk sac is enclosed inside the embryo to form the primitive gut 2-A part of the yolk sac remains outside the embryo. This is called definitive yolk sac  Differentiation of the intraembryonic mesoderm Paraxial lies parallel to mesoderm the notochord Intermediated Lies lateral to mesoderm paraxial Lateral plate The most lateral mesoderm  18 ▪As development proceeds 2 longitudinal grooves appear in IEM  on either side of the www.studyblue.co notochord dividing the m mesoderm into 3 parts: 23 1.Paraxial mesoderm 1 2.Intermediate mesoderm 3.Lateral plate mesoderm Keith L. Moore: Before we are born, 7th edition  Formation of somites notochord paraxial lateral plate mesoderm mesoderm Jack Stern 2003  Formation of somites 20 days somites Jack Stern 2003  Formation of somites - At the beginning of the 3rd week somites (or somitomeres) appear both side of the notochord and developing neural tube - Somites appear first cranially (around the 20th day), than develop caudally (3 pair/day). Formation of somites 4 OCC 7 CERV 12 THOR 5 LUMB 5 SACR 8-10 COCC ▪Dermomyotome divides into: i. Lateral part called dermatome: Spreads undercover of the ectoderm dermis of skin ii. Medial part called myotome  Will form the skeletal muscles of the trunk, shoulder girdle & Notochord pelvic girdle. 8 Which of the following structures is derived from the ectoderm? A) Liver B) Heart C) Skin D) Kidneys Which germ layer gives rise to the muscles? A) Ectoderm B) Endoderm C) Mesoderm D) All of the above The lining of the gastrointestinal tract is derived from: A) Ectoderm B) Mesoderm C) Endoderm D) Both A and B the germ layer responsible for the development of bones is: A) Ectoderm B) Mesoderm C) Endoderm D) All three germ layers The germ layer that forms the retina of the eye is: A) Mesoderm B) Ectoderm C) Endoderm D) None of the above Which of the following tissues is NOT derived from the ectoderm? A) Hair B) Nails C) Liver D) Brain Blood vessels and blood cells originate from: A) Mesoderm B) Ectoderm C) Endoderm D) None of the above