Chapter 18

Fertilization a. typically occurs in the uterus. b. often involves more than one sperm uniting with an egg. c. is the process by which the zygote becomes embedded in the uterine lining. d. typically occurs in an oviduct.

The yolk sac a. is a primary source of nourishment for human embryos. b. is the embryo's major contribution to the placenta. c. contains primordial germ cells. d. encloses the embryo in a fluid-filled sac.

Which of the following statements regarding childbirth is true? a. Most babies are born feet first. b. Delivery of the baby follows delivery of the placenta. c. Full-term babies are those born at 32 weeks' gestation. d. Infants born prematurely with very low birth weight require intensive care after birth.

Which of the following statements regarding development of the reproductive system is true? a. Testosterone directs development of male and female reproductive organs. b. In females, but not in males, the urogenital groove closes. c. The glans penis in males and clitoris in females form from the same embryonic structure. d. Male and female reproductive structures have formed by 6 weeks after fertilization.

Soon after fertilization, the zygote undergoes a series of rapid mitotic divisions called a. gastrulation. b. neurulation. c. cleavage. d. cell differentiation.

Which of the following statements about the notochord is \(f\) alse? a. The notochord forms from mesoderm. b. The notochord is part of the nervous system. c. The notochord provides rigidity and defines the long axis of the embryo. d. The vertebral column replaces the notochord, which degenerates, leaving remnants in intervertebral disks.

Which hormone stimulates milk cjection? a. prolactin b. human chorionic gonadotropin c. progesterone d. oxytocin

Highly reactive molecules, produced by normal cellular metabolism, that damage DNA are called a. antioxidants. b. telomeres. c. collagen. d. free radicals.