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Day 1
Day one marks the first day of stage one of pregnancy which is the secretory phase. On day one, the sperm fertilizes the egg and forms a zygote. The zygote is the first diploid cell that forms by fusion of the oocyte and the spermatozoon. -
Day 1
Day one of marks the beginning of stage one of pregnancy, the secretory phase. On day one, the sperm cell fertilizes the egg to form a zygote. A zygote is the first diploid cell that forms from the fusion of the oocyte and the spermatozoon -
Day 2
Day two marks the beginning of stage two of pregnancy. The zygote goes through cleavage which is cell division without growth. The cells will divide to become a morula, which is just a solid ball of cells. The cells are incaged in an outer lining called the zona pellucida. The cells are now called a blastocyst -
Day 6
Day 6 is when the blastocyst begins the implantation process. The blastocyst over the next week will implant itself into the uterine wall. If the blastocyst implantation is not successful by the time of the next menstrual cycle, the pregnancy will be lost. Because at this point the zona pellucida is gone, the outermost layer of cells, the trophoblasts, are rapidly multiplying. During this stage, the extraembryonic cavity will begin to form. -
Day 16
At this time the cell is developing three layers of cells in a process called gastrulation. The three layers are called the endoderm, the mesoderm, and the ectoderm. The ectoderm is the outermost layer which consists of superficial cells that did not migrate into interior of the inner cell mass. The mesoderm is the middle layer which consists of a poorly organized layer of migrating cells. The endoderm is the inner layer which consists of cells facing the blastocoele. -
Day 20
After day 18, where the neural grove has formed, the embryo begins musculoskeletal system development. The mesoderm begins forms connective tissue such as cartilage, bone, and muscle. The neural plate brain region in the ectoderm continues to expand. The endoderm, along with the yolk sac begins to form "blood islands" which will later become a part of the circulatory system. -
Day 28
At this time may of the baby's body, muscles, bones, and organs systems are beginning to form. The spinal cord begins to develop. Neural-Vascular development begins which is how the brain receives blood from arteries that connect to the carotid artery. The liver begins to form. Nasal plates begin to form, as well as optic nerves, the diaphragm, the pituitary gland, lungs, hearing, and the heart continues its formation. -
Day 44
Limb bones begin to form where the cartilage once was. The nasal plates have advanced to a point where the brain can now detect a smell. Bile ducts are formed continues between the liver cells and the gut. Dura matter which contains many blood vessels begins to appear around the spinal cord. In females, a uterine opening in the paramesonephric duct is forming. Lastly, the abdominal wall thickens. -
Day 56
Day 56 ends the organogenesis stage. Heart prominence continues. Facial features are close to done with development. Legs and arms are bent at the elbows, and fingers and toes separate. The vertebral column is now visible. Abdominal wall rectus muscles and oblique muscles form.
