PROCESS DIAGRAM
P a t h o f s p e r m t h r o u g h t h e r e p r o d u c t i v e t r a c t • F i g u r e 1 6 . 4
Sperm mature in the
epididymis for 10-14 days.
Penis
External urethral orifice
Anus
I Sperm go through the ejaculatory
duct into the urethra, along with
secretions from the seminal
vesicles and prostate.
Urinary bladder
Prostate
Bulbourethral gland
During ejaculation, sperm
and fluids (semen) pass
through the urethra of the
penis and out of the body.
Seminal vesicle
Coccyx
Rectum
The vas deferens stores
sperm, which can remain
viable for several months,
and propels sperm from the
epididymis into the urethra
during sexual arousal.
Scrotum
Sperm are made in the testes
by spermatogenesis (65-75
days from first cell division to
release into lumen of the
seminiferous tubule).
We can now trace the path of sperm through the male
reproductive tract (Figure 16.4). Sperm are made in the
testes and released into the lumen of the seminiferous
tubule. They mature in the epididymis for 10 to 14 days.
Sperm are stored in the vas deferens and can remain vi-
able for months. The vas deferens also propels sperm from
the epididymis into the urethra during sexual arousal.
Upon ejaculation, sperm go through the ejaculatory duct
into the urethra and mix with secretions from the seminal
vesicles, prostate, and bulbourethral glands to form se-
men, as we saw earlier.
The volume of semen in a typical ejaculation is 2.5 to
5 milliliters, with 50 to 150 million sperm per milliliter.
When the number falls below 20 million sperm per milli-
liter, the male is likely to be infertile. A very large number
of sperm is required for fertilization because only a tiny
fraction ever reaches the secondary oocyte (egg).
Semen has a slightly alkaline pH of 7.2 to 7.7, a milky
white color, and a sticky texture. Semen also contains an
antibiotic that can destroy certain bacteria and may help
control naturally occurring bacteria in the semen and in
the lower female reproductive tract.
474 CHAPTER 16
The Reproductive Systems
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