40. The corpus luteum prevents loss of the implanted embryo through menstruation by secreting ________.        

22. Which of the choices below is NOT a function of the vagina?  

34. A pregnant woman urinates more often than usual because the uterus compresses the bladder, her metabolic rate and blood volume are increased, and she must also dispose of fetal metabolic wastes.

8. Male testicular functions are regulated by FSH and LH.

5. Which blood vessels lack elastic tissue?        

35. Which is NOT a vessel that brings blood directly into the right atrium?        

46. Muscle tissue is formed by the ________.        

25. The receiving chambers of the heart include the ________.        

31. Implantation begins six to seven days after ovulation.

19. Which of the following provides the greatest surface area for gas exchange?