SOLUTIONS TO EXERCISES, LESSON 9
Sex hormones belong to a chemical group called steroids. Sex hormones are
formed primarily by the gonads and the adrenal cortex. The sex hormones of the
female are called estrogens and progesterone. The sex hormones of the male are
Whether an individual will be male or female is determined at the moment the
egg is fertilized by the sperm. This is determined by the new genetic combination.
Substances that later influence the production of sexual organs and characteristics are
The two kinds of sex chromosomes are X and Y.
Within the gonads, there is a special type of cell division known as meiosis. The
gametes, formed with this type of cell division, have a (single) set of chromosomes.
The production of a new individual is based upon the union of two gametes, that
is, a spermatozoon and an ovum. This process is called fertilization. This produces a
zygote with a double set of chromosomes. If the zygote has two X chromosomes (XX),
the individual will be a female. If the zygote has one X and one Y chromosome (XY),
During development, the testes "migrate" out of the body cavity, through the
inguinal canal of the abdominal wall, and into the scrotum. The testes are generally
cooler than the body cavity to ensure production of mature sperm. If undescended
testes remain uncorrected, the male will be sterile.
Produced within each testis are millions of spermatozoa and androgens.
The secondary sex organs of the male are responsible for the transport and care
of the spermatozoa.
As the spermatozoa pass along the length of the epididymis, they are nurtured by
the secretions of the epididymal wall.
The seminal vesicle produces a nutrient fluid that helps to maintain the
In the male, the combination of secretions and spermatozoa is known as the
The penis is capable of erection. The most favorable position in the vagina for
the deposit of semen is the upper recess of the vagina, opposite the opening of the