21) Which of the following results from endodermal contributions?

A) all cardiovascular components

B) brain and spinal cord

C) dermis and hypodermis

D) stem cells that produce gametes

E) nephrons

22) Which process, one that occurs during the first trimester, is characterized by the zygote becoming a “pre-embryo”?

A) placentation

B) embryogenesis

C) implantation

D) fertilization

E) cleavage

23) Which process begins as the surface of the blastocyst next to the inner cell mass adheres to the uterine lining?

A) oocyte activation

B) placentation

C) embryogenesis

D) implantation

E) blastocyst formation

24) During implantation,

A) the syncytial trophoblast erodes a path through the uterine epithelium.

B) the inner cell mass begins to form the placenta.

C) maternal blood vessels in the endometrium are walled off from the blastocyst.

D) the entire trophoblast becomes syncytial.

E) the inner cell mass is temporarily deprived of nutrients.

25) Separation of the inner cell mass from the trophoblast forms the

A) blastocoele.

B) lacunae.

C) amniotic cavity.

D) chorion.

E) allantois.

26) Which extraembryonic structure is created as migrating mesodermal cells form a layer beneath the trophoblast, separating it from the blastocoele?

A) amnion

B) placenta

C) allantois

D) yolk sac

E) chorion

27) Which of the following is a hormone secreted by both the placenta and the corpus luteum during pregnancy, and functions in suppressing the release of oxytocin?

A) progesterone

B) human chorionic gonadotropin

C) relaxin

D) placental prolactin

E) estrogen

28) The chorionic villi

A) form the yolk stalk.

B) are present in the umbilical stalk.

C) form the umbilical artery.

D) provide the surface area for gaseous exchange between fetal and maternal bloodstreams.

E) are present in the umbilical vein.

29) The presence of ________ in blood or urine is a reliable indication of pregnancy.

A) estrogen

B) progesterone

C) human placental lactogen

D) human chorionic gonadotropin

E) relaxin

30) By week three of development, the mesoderm extends along trophoblast structures, forming the ________.

A) yolk sac

B) chorionic villi

C) placenta

D) endometrium

E) allantois