Once fertilization is complete, a zygote migrates over the next 8 to 10 days toward the body of the uterus.

During implantation the inner cell mass (embryoblast cells) is the portion of the structure that will form the embryo.

Implantation point is usually low in the uterus, on the lower surface

Occasionally, a small amount of vaginal spotting appears on the day of implantation.

A fertilized ovum has 46 chromosomes

A proteolytic enzyme that released by the spermatozoa that dissolves the layer of cells protecting the ovum.

An ovum is capable of fertilization for only 24 hours.

A spermatozoon is capable of fertilization for about 48 hours, possibly as long as 72 hours.

Sexual relations must occur for fertilization to be successful is about 72 hours (48 hours before ovulation plus 24 hours afterward).

Umbilical artery carries oxygenated blood to the placenta

Foramen ovale allows movement of blood from the right atrium to the left atrium.

Ductus arteriosus is the adaptation that allows blood to flow from the pulmonary artery to the aorta in the fetal circulation.

In fetal circulation there is an increased resistance in the pulmonary artery.

It is said that there is a lot of pressure on the right side of the heart in the fetal circulation.