Briefly explain implantation.

Explanation

About 24 hours after fertilization zygote begins rapid and orderly pattern of divisions. as a result of cleavage an embryo having a spherical mass of 32 cells is formed. This stage is called morula. It reaches the uterus due to peristalsis and ciliary action of fallopian tube. Morula which is bathed in nutritive fluid secreted by the uterine glands, gets converted into blastula of 58 cell stage. Within the next five days it attaches to the wall of the uterus. This process is called implantation. During this process, the cells of the trophoblast secrete proteolytic enzymes which dissolve a small area in the uterine wall. This creates a depression to accommodate the blastocyst.