Embronic development for f.yPresentation Transcript
EMBRYONICDEVELOPMENT Ravi Ranjan & Gunjan Mehta Dept. of Biotechnology
1st Week of DevelopmentFertilizationCleavageBlastocyst FormationImplantation
Implantation of the Blastocyst
SPONTANEOUS ABORTION (Miscarriage)• Can occur for many reasons:• 1. Implantation did not occur (woman never knows she’s pregnant)• 2. Not enough hCG (menses occurs)• 3. Developmental problem in fetus death in utero• 4. Not enough progesterone lining breaks down• 5. Improper implantation• 6. Improper placenta
Summary• Cleavage is a series of mitotic divisions that results in an increase in cells, blastomeres,which become smaller with each division. After three divisions, blastomeres undergo compaction to become a tightly grouped ball of cells with inner and outer layers. Compacted blastomeres divide to forma 16-cell morula.• As the morula enters the uterus on the third or fourth day after fertilization, a cavity begins to appear, and the blastocyst forms. The inner cell mass, which is formed at the time of compaction and will develop into the embryo proper, is at one pole of the blastocyst. The outer cell mass, which surrounds the inner cells and the blastocyst cavity, will form the trophoblast.
Summary• The uterus at the time of implantation is in the secretory phase, and the blastocyst implants in the endometrium along the anterior or posterior wall. If fertilization does not occur, then the menstrual phase begins and the spongy and compact endometrial layers are shed. The basal layer remains to regenerate the other layers during the next cycle.
2nd Week of DevelopmentDevelopment of TrophoblastDevelopment of Bilaminar Embryonic discDevelopment of AmnionDevelopment of Yolk sacDevelopment of SinusoidsDevelopment of Extra embryonic mesodermDevelopment of Chorions
Bilaminar layer, Exocoelomic membrane & Amnion
Endometrium capillaries around the developingembro becomes dialted and reffered as MaternalSinusoids. Maternal sinusoid
3rd Week of DevelopmentGastrulationNeurulationDevelopment of Chorionic VilliDevelopment of Placenta
3rd Week of DevelopmentGastrulationPrimitive Stalk formationPrimitive Node formationTrilaminar Disk formationNotochordal processNotochordOropharangeal & Cloacal membrane
Trilaminar Disk formation
Differentiation of Primary Germ Layers (from the gastrula) Ectoderm Mesoderm EndodermNervous system Skeleton Digestive tractEpidermis of skin Muscles, Dermis Respiratory of skin system, BladderEar, lens, cornea Circulatory system Liver, pancreasSalivary & Pituitary Gonads Epithelial lining ofgland Cowper’s, parathyroid glands, pancreas
SurfaceEctoderm Caudal (posterior)
3rd Week of DevelopmentNeurulationEctodermal cell Notochord Neural plateMesodermal cell Notochord Vertebral bodiesNeural plate, fold, groove, tube.Development of somitesMyotome- Skeletal muscle of neck, limbDermatome- Connective tissue, Skin dermisSclerotome- VertebrateDevelopment of Intraembryonic CoelomDevelopment of Cardiovasular System
3rd Week of DevelopmentDevelopment of Chorionic VilliDevelopment of Placenta
Gestation period• During first trimester individual starts out as a zygote, then morula, blastocyst, and after implantation, is called an embryo.• Embryonic phase of development lasts from fertilization until the 8th week of gestation, when it becomes a fetus.• By day 35 the heart is beating, and eye and limb buds are present.• By the end of the third month the placenta is functioning.• By month four, the rudiments of all organ systems are formed and functioning, and from then on, fetal development is primarily a matter of growth.
Functions of the placenta:1 Transfer gasses2 Transport nutrients3 Excretion of wastes4 Hormone production – temporary endocrine organ – estrogen and progesterone5 Formation of a barrier – incomplete, nonselective – alcohol, steroids, narcotics, anesthetics, some antibiotics and some organisms can cross
Development of the Placenta
4th Week of DevelopmentOrganogenesisEmbryonic foldingMedian plane- fold- Head fold, tail fold & Horizontal foldLateral fold- Fore gut, Mid gut, Hind gutOtic placode- Internal EarLens placode- EyesPharangeal arch- Head & Neck Embryonic Period 1st to 4th week, 5th to 8th week Fetal Period