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First week, conception takes place where a woman’s ovum is penetrated by a man’s sperm during fertilization. Ovum and sperm forms a fertilized egg, or zygote. -
By the end of week 1, the zygote becomes the morula which than it is form into the blastocyst. The blastocyst stops traveling and undergoes implantation. Embedded in endometrium, the innermost lining of the uterus back wall. -
Blastocyst grows by increased proliferation of embryonic cells, with differentiation also occurring. Resulting a cellular morphogenesis. This increased number of embryonic cells creates the embryonic cell layers within the blastocyst. A bilaminar embryonic disc is develop from the blastocyst. The bilaminar disc have a superior layer, epiblast, and a inferior layer, hypoblast layer. -
The primitive streak forms within the bilaminar embryonic disc. Bilaminar embryonic disc is thickened into the trilaminar embryonic disc having three layers, ectoderm, mesoderm, and the endoderm. -
CNS begins to develop in the embryo forming the spinal cord and the brain. The neural crest cells, develop from the neuroectoderm, migrate from the crests of the of the neural folds and join the mesoderm to form mesenchyme. Mesenchyme develops many face and neck structures such as pharyngeal or branchial arches. -
Week 4, embryonic disc undergoes embryonic folding. Face and neck begin to develop, with the primitive eyes, ears, nose, oral cavity, & jaws. From week 5 and 8, the spinal cord, brain, heart and the rest of the organs begin to form. Processes start fusing together to form facial and cervical structures of the human body. -
Even though the embryo has been breathing since the third week of prenatal development, by the end of the fourth month the fetal heartbeat and fetal movements are also present. Reproductive organs form, tooth buds appear, and brain develops rapidly. -
Most of the fetus organs are develop and maturating. Fetus is ready to be delivered.