10 general embryology & musculoskeletal system 13:05
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general embryology development of musculoskeletal system
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10 general embryology & musculoskeletal system 13:05
- 1. DEVELOPMENT OF MUSCULOSKELETAL SYSTEM WITH GENERAL EMBRYOLOGY DR KIRTI S SOLANKE
- 2. stages • 23 stages-first 8 weeks after ovulation • Streeter(1942) and O'Rahilly & Müller (1987). • Comparing with other embryos
- 4. Primordial germ cell formation • Gamets –PGC-formed in epiblast during 2nd wk of dev move to wall of yolk sac • 4th wk migrate from yolk sac-arrive in dev gonad at 5th wk • For preparation of fertilization ,has to undergo gametogenesis-meiosis-to reduse chromosome no cytodifferentiation-to complete maturation
- 5. THE PHASES OF FERTILIZATION INCLUDE • Phase 1- penetration of the corona radiata by sperm • Phase 2- penetration of the zona pellucida by sperm • Phase 3- fusion of the oocyte and sperm cell Membranes • Capacitated sperm pass freely through corona cells
- 6. FERTILIZATION • CAPACITATION-modifications of membrane sterols or surface protins so that spems traverse cumulus oophorus and corona radiata & bind to specific glycoprotein receptors on zona pellucida ZP3 & ZP2
- 7. • Acrosomal reaction-interaction of ZP3 with spem head ,fusion of membranes on sperm head releases enzymes ,acrosin ,digest zona around sperm head so enter into perivitelline space • As sperm enter inside and touches oocyte second meiotic division completes and form female pronuclei • At same time cortical secretary granules are realesed from plasma membrane of oocyte act on ZP3 to prevent entry of other sperms – zona reaction
- 10. uncompacted compacted eight-cell mouse embryos
- 11. Day 5
- 12. Day 6
- 13. implantation • Posterior wall of uterus,nearer to fundus,may be median plane or to side • Placenta previa-near internal os
- 14. DAY 8
- 15. DAY 9
- 16. DAY 11- 12
- 17. DAY -13
- 18. 3RD WEEK • Grastrulation • Primitive streak • Formation of notochord
- 28. • 20th day of development –1st somite appear in occipital region • new somites appear in craniocaudal sequence at a rate of approximately three pairs per until, • There are 4 occipital, 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 8 to 10 coccygeal pairs. • The first occipital and the last five to seven coccygeal somites later disappear, while the remaining somites form the axial skeleton
- 29. SOMITE DIFFERENTIATION • as a ball of mesoderm -then undergo a process of epithelization – • arrange themselves in a donut shape around a small lumen- • cells in the ventral and medial walls of the somite lose their epithelial characteristics, become mesenchymal again- surround the neural tube and notochord(sclerotome)-VC & rib.
- 31. MYOTOME • Cells in the dermomyotome ultimately form dermis for the skin of the back and muscles for the back, body wall (intercostal muscles), and some limb muscles • cells from the ventrolateral edge migrate into the parietal layer of lateral plate mesoderm to form most of the musculature for the body wall (external and internal oblique and transverses abdominis muscles) and most of the limb muscles
- 32. FORMATION OF VERTEBRAL COLUMN
- 33. RIBA & STERNUM • Bony potion of rib-sclerotome-grow out from costal processess of thorasic vertebra • Costal cartilage-sclerotome cells that migrate out into parietal layer of lateral plate mesoderm • Sternum-parietal layer of lateral plate mesodem • Cleft sternum
- 34. SKULL • Neurocranium • Viscerocranium • Neurocranium-1.membranous-flat part 2.cartilagenous—base of skull • Membranous-from neural crest cell and paraaxial mesoderm-mesenchyme- intramembranous ossification-bone spicules- radiate from I centre-apposition growth
- 35. • Cartilagenous-rostral to notochord from NCC- prechordal chondrocranium • From occipital sclerotome-chordal chondrocranoum • VISCEROCRANIUM-1st 2 pharyngeal arches— maxillalary process,mandibular process
- 37. MUSCLE • Skeletal-paraaxial mesoderm • Smooth-splanchnopleuric mesoderm surrounding gut tube • Cardiac --splanchnopleuric mesoderm surrounding heart tube • Head muscle-7 somitomeres • Somitimeres-partially segmented whorls of mesenchymal cells from paraaxial mesoderm
- 39. LIMB DEVELOPMENT • End of fourth week , limb buds - as outpocketings from the ventrolateral wall • a mesenchymal core derived from the parietal (somatic) layer of lateral plate mesoderm -form the bones and connective tissues of the limb, covered by a layer of cuboidal ectoderm(apical ectodermal ridge (AER)
- 41. Thank you
- 42. • Scoliosis-two sucessive vertebrae fuse asymmetrically • Klippel –feil syndrome • Cleft vertebra(spina bifida)
Editor's Notes
- Much of this conditioning during capacitation occurs in the uterine tube and involves epithelial interactions between the sperm and the mucosal surface of the tube. During this time, a glycoprotein coat and seminal plasma proteins are removed from the plasma membrane that overlies the acrosomal region of the spermatozoa.Only capacitated sperm can pass through the corona cells and undergo the acrosome reaction
- Spermatozoa are not ableto fertilize the oocyte immediately upon arrivalin the female genital tract but must undergo(1) capacitation and (2) the acrosome reactionto acquire this capability.Capacitation is a period of conditioning inthe female reproductive tract that in the humanlasts approximately 7 hours
- After fertilization clevage –first divisionTill 8 cell stage cells are loosely arrangedCompaction-inner cell mass-embryo outer cell mass –trophoblast16 cell stage morula day 3,day 4-enters uterine cavity,cavity appears inside morulaEmbyonic pole
- Cavity-primary yolk sac ,primary umbilical vesocleAs secondary yolk sac is forming diverticulum of visceral hypoblast, an allantois,extend into extraembryonicmesoblast.Exrtraembryonicmesoblast-do not contribute to future body directlyCovers amnion ,II yolk sac ,internal wall of mural trophoblast,form connecting stalk
- by apposition of newlayers on the outer surface and by simultaneousosteoclasticresorption from the inside.
- The base of the skull is formed whenthese cartilages fuse and ossify by endochondralossification (Figs. 10.3 and 10.6).
- Skull ,sternum,vertcolum,ribs
- The bone-forming capacity of mesenchymeis not restricted to cells of the sclerotome,but occurs also in the parietal layer ofthe lateral plate mesoderm of the body wall.
- lateral plate mesoderm of the body wall.This layer of mesoderm forms bones of thepelvic and shoulder girdles, limbs, and sternum
- Resegmentation occurs when the caudal halfof each sclerotome grows into and fuses withthe cephalic half of each subjacent sclerotome
- wall (rectus abdominus, internal and externaloblique, and transversusabdominus), and limbmuscles. The remaining cells in the myotomeform muscles of the back, shoulder girdle,and intercostal muscles