1. If an embryo has a Y chromosome, its gonad responds to theplacental hormone called _______________ and begins to secrete testosterone.

2. The labia majora of a female and scrotum of a male are _______________ becausethey both arise from the same structure, the labioscrotal folds of the embryo.

3. The descending fetal testes are guided through the inguinal canalinto the _______________ by a cord called the_______________.

4. The external genitals and anal orifice occupy a diamond-shapedspace between the thighs called the _______________.

5. Sperm are produced in tiny ducts in the testes called the _______________.

6. After they are produced, sperm are stored in an organ called the _______________ on theposterior surface of the testis.

7. The spermatic cord contains the _______________ plexus of blood vessels, which behaves as a _______________ exchanger to prevent the incoming blood from overheating thetestes.

8. A short passage, the _______________, conveys both sperm and seminal vesicle fluid to theprostatic urethra.

9. Semen is sticky because, like clotted blood, it contains _______________.

10. Erection of the penis results from the swelling of tiny cavitiescalled _______________ with blood.

11. The testes do not secrete testosterone unless they arestimulated by a pituitary hormone called _______________.

12. The hormone _______________is responsible for stimulating the sex drive, or _______________, in both sexes.

13. The chromosomes we pass on to our children are not the same asthose we inherit from our parents because they exchange DNA with each other during aprocess called _______________ in meiosis.

14. A spermatozoon has a lysosome at its tip called the _______________, which ituses to penetrate an egg.

15. Semen is expelled from the penis by rhythmic contractions of the_______________ muscle that ensheaths its root.

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