Fertilization begins when sperm binds to the corona radiata of the egg. Once the sperm enters the cytoplasm, a cortical reaction occurs which prevents other sperm from entering the oocyte. The oocyte then undergoes an important reaction. What is the next reaction that is necessary for fertilization to continue?
AThe second meiotic division
BDegeneration of the sperm tail
CRelease of a polar body
DFormation of the spindle apparatus
EAcrosome reaction
A 22-year-old woman comes to the physician to discuss the prescription of an oral contraceptive. She has no history of major medical illness and takes no medications. She does not smoke cigarettes. She is sexually active with her boyfriend and has been using condoms for contraception. Physical examination shows no abnormalities. She is prescribed combined levonorgestrel and ethinylestradiol tablets. Which of the following is the most important mechanism of action of this drug in the prevention of pregnancy?
AInhibition of rise in luteinizing hormone
BSuppression of ovarian folliculogenesis
CThickening of cervical mucus
DPrevention of endometrial proliferation
EIncrease of sex-hormone binding globulin
A 36-year-old woman comes to the physician because she has not had her menstrual period for the past 4 months. During this period, she has had frequent headaches, difficulty sleeping, and increased sweating. She has not had any weight changes. Over the past year, menses occurred at irregular 30- to 45-day intervals with light flow. The patient underwent two successful cesarean sections at the ages of 28 and 32. She has two healthy children. She is sexually active with her husband and does not use condoms. Her vital signs are within normal limits. Physical examination shows no abnormalities. Laboratory studies show: Estradiol 8 pg/mL (mid-follicular phase: N=27–123 pg/mL) Follicle-stimulating hormone 200 mIU/mL Luteinizing hormone 180 mIU/mL Prolactin 16 ng/mL Which of the following is the most likely diagnosis?
APregnancy
BPrimary hypothyroidism
CPremature ovarian failure
DMajor depressive disorder
EPolycystic ovary syndrome
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