![]() ![]() In 24 to 48 hours, the zona pellucida breaches. The presence of the blastocyst means that two types of cells are forming, an inner-cell mass growing on the interior of the blastocele and cells growing on the exterior of it. This new structure with a cavity in the center and the developing cells around it is known as a blastocyst. ![]() Cells grow increasingly smaller to fit in. Then, a flat layer cell forms on the exterior of this cavity, and the zona pellucida, the blastocyst's barrier, remains the same size as before. ![]() At this time, the embryo usually consists of 50 cells.ĭevelopment 14 fetuses showing stages of embryo development in the African elephant After implantation Ī blastocele is a small cavity on the center of the embryo, and the developing embryonary cells will grow around it. After fertilization, the newly formed zygote then begins to divide through mitosis, forming an embryo, which implants in the female's endometrium. Sometimes, a zygote can be created by humans outside of the animal's body in the artificial process of in-vitro fertilization. The spermatozoon fertilizes an ovum or various ova in the uterus or fallopian tubes, and this results in one or multiple zygotes. It begins when a fertilized zygote implants in the female's uterus, and ends once it leaves the uterus.ĭuring copulation, the male inseminates the female. In mammals, pregnancy is the period of reproduction during which a female carries one or more live offspring from implantation in the uterus through gestation. JSTOR ( March 2012) ( Learn how and when to remove this template message).Unsourced material may be challenged and removed.įind sources: "Pregnancy" mammals – news Please help improve this article by adding citations to reliable sources. This article needs additional citations for verification. ![]()
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