The blastocyst is composed of the outer cell layer called as the trophoblast and the inner cell mass. The inner cell mass will form all the tissues of the embryo and differentiate into embryo proper. The trophoblast will form the placental structures. Both the morula and blastocyst refer to the earliest stages of an embryo. After 3–4 days of the egg being inseminated the embryo cells assume a spherical shape. This transition is known as the morula. After 4–5 days, a cavity forms within the embryo cells. This stage is known as the blastocyst . Further, cells within the blastocyst are known as the inner cell mass and is the initial stage in giving rise to the head and body of the developing fetus. Implantation is one of the stage of pregnancy. During this stage, the blastocyst attaches to the wall of the uterus on uterine endometrium. The developing embryo receives oxygen and nutrients from the mother from this attachement. Implantation is controlled by trophoblast and occurs by decidual cell reaction. Identify the human development stage shown, as well as the related right place of its occurrence in a normal pregnant women and select the right option for the two together. Development stage - blastula; Site of occurence - end part of fallopian tube Development stage - blastocyst ; Site of occurrence - uterine wall Development stage - 8-celled morula; Site of occurrence - starting point of fallopian tube Development stage - late morula; Site of occurrence - middle part of fallopian tube
