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Embryonic development


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Embryonic development

  2. 2.  : : ( on . . 1/1)- ( . 3)So is a process of the descent of various components of the body. This process involves the following factors without which a healthy can’t be obtained. It includes spermatogenesis, oogenesis, formation of embryo and its complete growth and
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  7. 7.  In charaka shareera it is mentioned that the fetus gets its nourishment in different ways at different stages of growth. Either in the initial stages or before differentation of various organs it get its nourishment from ahara rasa of the mother through upa sneha and upa sweda (diffusion and osmosis ). After the body parts are formed it gets its nutrition through upasneha and nabhi nadi or umbilical cord. The nabhi nadi is attached to the rasa vaha nadi of the mother and this carries ahara rasa veerya from the mother to the fetus. The fetus grows by the indirect supply of nutrition.
  8. 8.  -- . -- -- -- . . . -- -- ... . -- . .
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  11. 11. . / – - - –In cha sa 2/ 12 , atreya answer to sishyas regarding the .
  13. 13. FERTILIZATION It is the process by which male and female gamates fuse to form zygote, it occurs in the ampullary region of uterine tube.
  14. 14. RESULTS OFFERTILIZATION Sex determination. Starting of cleavege.
  15. 15. Two days after fertilization, embryo is at 2celledstage.Three days after fertilization embryo . becomes morula.Fourth day -- Blastocyst has formed.
  16. 16. Late implantation/Uteroplacental circulationBilaminar disk, amniotic cavity and primary yolk sacExtra-embryonic mesoderm and coelomFormation of the chorion and definitive yolk sac
  17. 17. Trophoblast Bilaminar embryonic disccytotrophoblast Epiblast Syncytiotrophoblast HypoblastCavities Amnionic Blastocoel
  18. 18. EARLY 2ND WEEK Fibrincoagulum Lacunar stage Exocoelomic memb Primary yolk sac
  19. 19. 11th 12th day Uteroplacental Sinusoids circulation. Trophoblast have lacunar space in the form of inter communicating network.More evident at embryonic pole. The cells of synciotropoblast continue penetrating deep and erode endometrial lining of meternal capillaries. Lacunae continue with the sinusoids.
  20. 20. Extra-embryonicmesoderm / Extra-embryonic coelomCells derived from the primitive ectoderm fill the space between the trophoblast and two cavities This loose connective tissue, the extraembryonic mesoderm, completely surrounds the amnion and primary yolk sac Fluid-filled spaces appear in the mesenchyme, pushing aside the mesenchyme to form a coelom These spaces fuse to form a fluid-filled cavity completely surrounding the amnion and yolk sac, except at the connecting stalk
  21. 21.  Extra embryonic coelom / Chorionic cavity. When EEC enlarges EEM will be restricted to lining. Extra embryonic somato pleuric mesoderm Extra embryonic splanchno pleuric mesoderm
  22. 22. Primary villi. Secondary yolk sac Exocoelomic cyst Connecting stalk13th day
  23. 23. Gastrulation: Primitive Streak and Cell MigrationsResults of Gastrulation: Fate of the Germ LayersNotochord: the Primary InducerNeurulation: Neural Tube FormationNeural Crest Cells and their Derivatives
  24. 24. GASTRULATION Its the process that establishes all 3 germ layers. It begins with formation of Primitive Streak on surface of epiblast. Cephalic end- primitive node. Cells of epiblast migrate towards primitive streak and it become flask shape. It then detach from epiblast and slip beneath it. INVAGINATION. Once cells invaginated, some displace hypoblast and form- embryonic ENDODERM. Some lie in b/w epiblast and new embryonic endoderm to form MESODERM. Remaining cells form embryonic ECTODERM. Thus epiblast is source of all 3 layers.
  25. 25. NOTOCHORD The pre notochordal cells invaginating in the primitive streak, move forward cranially, untill they reach prechordal plate. These cells intercalate in endoderm as notochordal plate. By further development, the plate detaches from endoderm and a solid cord is formed. This will serve as basis of axial skeleton.
  26. 26. NEURULATION. At beginning of 3rd week ectodermal germ layer is of disc shape. The overlying ectoderm thickens and form NEURAL PLATE. Cells of the plate make up neuroectoderm. Once induction begin the neural plate expands towards primitive streak. By end of 3rd week,lateral edge of neural plate expands to form NEURAL FOLD. And mid region – NEURAL GROOVE. Gradually Neural folds approaches each other and fuse in middle ,and continues upward and downwards. NEURAL TUBE. CRANIAL NEUROPORE & CAUDAL NEUROPORE.
  27. 27.  Vasculogenesis- EEM – angioblasts- angiogenic clustor of cells- endothelial cells – this fuse with each side to form small blood vessels. Hematopoiesis- occur in EEVM – angioblasts in angiogenic cell clusters give rise to primitive blood cells. At 5th week it is taken over by organs.
  28. 28. Somite developmentIntraembryonic coelom & body cavitiesHead-tail foldingLateral folding
  29. 29.  In week 4, the embryo undergoes major morphological changes as it changes from a trilaminar disc-shaped embryo to a cylindrical embryo. This is also an important week in terms of determining placement of future organs. Following median and horizontal folding, many organs and body cavities will begin to form or will be repositioned. Embryo begin to fold.
  30. 30. Head-Tail Folding Due to the rapid growth in the median plane of the brain, amniotic cavity, and somites, the embryo elongates, with its head and tail ends folding under. At the cranial end, the head will be folded under, with a very prominent forebrain. On the ventral side, the newly positioned primitive heart, pericardial cavity, septum transversum, and bucco-pharyngeal membrane
  31. 31.  At the same time that head-tail folding is occurring, lateral folding is also occurring to form a cylindrical embryo
  32. 32.  22nd – 23rd day – Fusion of neural fold . Neoropores widly opened. Heart tube begin to fold.24th -25 th day – Cephalocaudal folding. Cranial neuropore closing. Optic vesicles appear. Otic placcodes appear. 26th-27th day – Caudal neuropore closing. Upper limbs buds appear. 3 pairs of visceral arches.
  33. 33. EMBRYO AT 4TH WEEK.
  34. 34. Somite Development The paraxial mesoderm will develop into paired cuboidal bodies, or somites (soma, body). These will eventually develop into the bones (Sclerotome), Muscles (Myotome), and Dermis (Dermatome) of and surrounding the axial skeleton Somites appear as bumps on the dorsal surface of the embryo. At the end of week 3, 4-12 somites are present (visible on the dorsal surface of the embryo). By the end of week 5, 42-44 can be counted. The most appear between days 20-30, giving this period the title of the somite period of development. Somites appear cranially to caudally, beginning at the occipital end. They can be counted and are used to roughly estimate the age of the embryo
  35. 35. FATE OF GERM LAYERS ECTODERM This layer gives rise to: the central nervous system; the peripheral nervous system; the sensory epithelium of the ear, nose and eye; the epidermis, hair and nails; and the subcutaneous, mammary and pituitary gland; · the enamel of teeth.
  36. 36. MESODERMAL SHEATH Intermediate Paraxial mesoderm mesoderm Lateral plate Nephrotomes- cranially Nephrogenic somatic (parietal Somites ( 42-44) cells-caudallyThe epithelial cells forming the somites lose their epithelial shape and migrate in the splanchnic direction of the notochord and the spinal cord to form the sclerotome (future (visceral vertebral column). The dorsal wall of the somite differentiate into the myotome (furute muscles) and thedermatome (future dermis). , both developing into the excretory units of kidneys, gonads, ducts and accessory glands
  37. 37.  ENDODERMit provide epithelial lining of gastro- intestinal tract, respiratory tract, urinary tract, urinary bladder, also paranchyma of thyroid, parathyroids, liver, pancreas.
  38. 38. 5TH WEEK 28th- 30th day-Fourth visceral arch will be formed. Hind limb bud appear. Otic vesicle and lence placode become clear. 31st-35th day- forelimb paddle shaped. Nasal pit formed. Embryo C shaped. By the time embryos tiny heart begin to beat. Neural tube enlarges into 3 parts , soon to become a very complex brain.
  39. 39. 6TH WEEK In this week growth is fast. 36th-42nd day- Digital rays in the hand and foot plate appear. Brain vesicles prominent. - External auricle , formed from auricular hillock - Umbilical herniation initiated. Eyes ears limbs toes become identifiable.
  40. 40. 7TH WEEK 43rd-49th day – Pigmentation of retina vissible - Digitals separating. - Nipples and eyes formed. - Maxillary swelling fuse with medial nasal swelling and upper lip is formed. - prominent umbilical herniation. Major muscle system is developed. The child has its own blood type from mothers.
  41. 41. 8TH WEEK Limbs long and bend at elbows, knees, fingers,toes free. Face more human like. Tail disppears. Umbilical herniation persist end of 3rd week. By eighth week all organs develop, and embryo is now called foetus. Foetus is about half inch long. It is protected by amnionic sac, filled with fluid.