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Day 1
Stage 1 in fertilization, the zygote is being formed following the process of fertilization. -
Day 2
Stage 2, the morula is formed which is a solid mass of cells. -
Days 3-4
Stage 3, The blastocyst formed on day 3 hatches and is now able to implant to the uterine wall on day 4. The zona pellucida is now lost -
Days 7-12
Stage 5, the implantation process is completed and the embryo adheres to the uterus wall -
Day 16
Gastrulation occurs, Mesoderm lies between the ectoderm and endoderm as a continuous sheet. The notochord is formed and is key to embryonic folding and regulation of ectoderm and mesoderm differentiation -
Days 22-23
Stage 10, The heart begins to beat which makes it the first functioning embryonic organ formed. Neural folds in region of developing brain -
Day 31
Upper and lower limb buds start growing. Heart, liver, umbilical cord, mesonephric ridge are visible externally as bulges -
Day 33
Stage 15 starts. Vascular development occurs. Development of the middle cerebral artery is first identified as small buds originating proximal to the anterior cerebral artery on the anterior division of the primitive internal carotid artery. -
Day 37
Stage 16, Abdominal Wall muscle cell migration, the lateral plate mesoderm has become more condensed and thicker in the area around the myoblasts. Upper lip and eyelid development begin and semilunar valves form at the heart. -
Day 44
Stage 18, Abdominal wall is formed and thickens. The liver is almost fully developed, and vision begins to develop as well. The anal membrane is defined as well as testes(male), or ovaries and uterus(female) are developed. -
Days 50-53
Stage 20 and 21, cerebellum cell layer (future Purkinje cells) develops. Upper and lower limbs rotate, Abdominal Wall Myoblasts have reached the ventral midline and myotubes were present and oriented uniformly within all muscle groups. Finger and toe limbs lengthen. -
Days 55-56
Stage 22-23, Head nose, eye, external acoustic meatus, eyelids, external ears, rounded head,straightening of trunk, umbilical cord, intestines herniated at umbilicus limb. Upper limbs longer and bent at elbow, hands and feet turned inward, foot with separated digits, wrist, hand with separated digits. Extraembryonic Coelom chorionic cavity is now lost by fusion with the expanding amniotic cavity
