(2) Semen. Semen (seminal fluid) is the fluid discharged at ejaculation by a
male. This fluid is made up of sperm in the secretions of the seminal vesicles, the
prostate gland, and the bulbourethral glands.
h. Urethra. The urethra is the final duct of the reproductive system. This duct
acts as a passageway for sperm or urine. The urethra is about 20 cm (8 inches) long.
The ejaculatory ducts pass sperm into the urethra which passes through the prostate
gland and through the penis to be ejaculated.
PATHWAY OF SPERM CELLS
The preceding paragraphs have described the manner in which sperm are
produced. Now look at the entire pathway a sperm must travel to fertilize an ovum.
a. With each ejaculation, the testes release up to 400 million sperm. The goal is
for one sperm cell to meet and fertilize one ovum.
b. When a male ejaculates, sperm are ejected from the pocket of the testes
through a series of ducts (the epididymis ducts, the ductus deferens, and the ejaculatory
c. Seminal fluid, pouring into the ducts from the prostate gland and the
bulbourethral glands, flushes the sperm through the urethra and out of the tip of the
d. Before fertilization can take place, the sperm must be deposited in the vaginal
vault, pass through the tiny opening of the cervix, swim through the uterus, and reach
the fallopian tubes.
(1) Only the strongest sperm cells survive. Most sperm are destroyed
immediately by the acidic fluids that cleanse the vagina. Only a few thousand sperm
reach the cervix, and fewer still reach the fallopian tubes.
(2) Normally, the cervix is blocked by a hard wall of mucus which prevents
bacteria from entering the uterus. For a few days each month (near the time of
ovulation), this thick cervical mucus changes into a fluid stream that sperm can
(3) Those sperm that pass through the cervix have about 48 hours in which
to reach and fertilize an ovum before they (the sperm) die. Sperm cells can travel this
distance in a few minutes.
e. The difficulty of this journey helps ensure that only the most healthy sperm
cells reach the fertilization point. Sometimes a poor quality sperm and ovum do unite.
Most of these fertilized ova stop developing and are lost spontaneously. The woman
losing such an ovum does not even realize that she has been pregnant.