25. If an embryo failed to form the mesoderm germ layer what would not develop?

Question

25. If an embryo failed to form the mesoderm germ layer what would not develop?

26. Where do ectopic pregnancies most often occur?

27. What forms the lens of the eye?

28. What portion of the blastocyst will give rise to the embryo?

29. A sacrococcygeal teratoma is a tumor that arises from remnants of what?

30. The amniotic cavity appears on the eighth day as a slit-like space between the trophoblast and the what?

31. Where does fertilization usually occur:

32. What is the acrosome reaction?

33. Know the female menstrual cycle:

34. The normal implantation site is where?

35. Be familiar with somite development.

36. The most distinctive characteristic of a primary chorionic villus is its what?

37. Diagram the correct developmental path of the male gamete:

Explanation / Answer

25) Mesoderm gem layer gives rise to umbillical blood vessels, muscle tissues and bones in body. A human embryo that did not develop mesoderm during gastrulation would result in early termination of pregnancy.

26) Majority of ectopic pregnancies are tubal pregnancies that occur in fallopian tube. However, they can occur in other locations such as the ovary, cervix and abdominal cavity.

27) The lens is composed of transparent, flexible tissue and is located directly behind the iris and the pupil. It is made primarily of a protein called collagen, which is very tough and strong. During embryonic devcelopment, surface ectoderm is responsible for formation of lens of eye.

28) A blastocyst is a large cluster of cells with a fluid-filled cavity. It consists of two parts: one that develops into the embryo and one that gives rise to part of the placenta. It possesses an inner cell mass (ICM) which subsequently forms the embryo. The outer layer of the blastocyst consists of cells collectively called the trophoblast. This layer surrounds the inner cell mass and a fluid-filled cavity known as the blastocoele. The trophoblast gives rise to the placenta.

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