3.The answer is d.(Alberts, pp 1151–1152. Junqueira, pp 435, 439–440, 443.)
The secondary oocyte enters the second meiotic division just before ovulation
and arrests at metaphase. Fertilization by a spermatozoon provides the stimu-
lation for the division of chromatin to the haploid number. By the time the fer-
tilized ovum reaches the uterus, the progesterone (answer a)produced by the
corpus luteum has initiated the secretory phase in the endometrium. Once
implantation occurs and the chorion develops, human chorionic gonadotropin
(hCG) is synthesized and the corpus luteum is maintained (answer e).Expul-
sion from the follicle (answer b)and the environment of the oviduct and
uterus(answer c)donotinduce the second meiotic division.
4.The answer is e.(Junqueira, p 443. Moore and Persaud, Developing, pp
31–33. Gilbert, pp 194–195. Sadler, p 35.)Capacitation, the acrosome reaction
and penetration are required for the hamster sperm penetration assay (SPA).
Capacitation prepares the sperm for fertilization and requires an increase in
fluidity of the sperm plasma membrane. Sperm must reside in the female
reproductive tract or under appropriate in vitro conditions for about 1 hour for
capacitation to occur. During capacitation there is a loss of decapacitation fac-
tors that have been added to the sperm by epididymal cells and accessory
male reproductive organs. Cholesterol is removed (not added, answer b)
from the sperm plasma membrane during this period, which results in the
increased fluidity (not a decrease, answer c) of this membrane that is required
for the fusion of the acrosomal membrane with the sperm plasma membrane.
Next, there is release of the acrosomal enzymes (not sequestration, answer d),
which are required for the breakdown of the corona radiata and the zona pel-
lucida of the oocyte to facilitate sperm penetration. Sperm formation and mat-
uration occur in the testis and epididymis (answer a)and thus are not directly
tested in a hamster egg penetration assay.
5.The answer is e.(Sadler, pp 22–25. Ross and Pawlina, p 774.)Primary
oocytes have developed by the time of birth. From puberty to menopause,
these germ cells remain suspended in meiotic prophase I (diplotene or dictyate
stage). A midcycle surge of LH triggers the resumption of meiosis and causes
the FSH-primed follicle to rupture and discharge the ovum. Under the influ-
ence of LH, the ruptured follicle is transformed into a corpus luteum, which
produces progesterone. FSH and LH produced in the adenohypophysis result
in growth and maturation of the ovarian follicle. Under FSH stimulation, the
theca cells proliferate, hypertrophy, and begin to produce estrogen.
82 Anatomy, Histology, and Cell Biology