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Summary Human Reproduction: Life Sciences
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Grade 12 Life Sciences Notes
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Human ReproductionHumans are unisexual – they either have male or female
reproductive organs and show internal fertilization)
The advantages of sexual reproduction outweigh its cost
in time/energy, and mammals have developed highly
effective reproductive systems that ensure its success.
1. Male reproductive system
Consists of the following:
1.1 Testes
1.2 Tubules for the transport of sperm
1.3 Accessory glands
1.4 Penis
1.1 Testes
Oval-shaped glandular gonads
Hang outside abdominal cavity); enclosed in scrotum (double layered pouch)
Internally divided into lobules
In the lobules are convoluted seminiferous tubules (approximately 1000 in each testis):
1. Lined with germinal epithelium
2. Divide to form haploid spermatozoa
3. Surrounded by Cells of Leydig
Note: The total length of the tubules is over 500m,enabling the tubules to produce between
200-500 million sperm for each ejaculation
Some of the germinal epithelium develops into Cells of Sertoli
Large columnar cells which provide food for sperm
Cells of Leydig – lie between the seminiferous tubules
connective tissue containing groups of interstitial cells that produce testosterone
1
, Scrotum
pouch-like structure containing testes
male foetus: testes develop inside abdominal cavity & descend into scrotum at time of birth
temperature in scrotum is slightly lower than body temperature (this favours sperm
production – sperm develop most efficiently at 34 ⁰C)
1.2 Tubules for transport of sperm
Note: Spermatic cord
vas deferens, blood vessels and nerves of testes are wrapped in a covering muscle,
forming spermatic cord
vas deferens begins at end of epididymis, runs up into spermatic cord and enters
urethra (just after urethra leaves bladder)
Tubule Description Function
a. Epididymis long convoluted tubule store’s sperm (sperm matures
(± 5cm) situated at back here)
of testes membrane secretes mucous
lined with mucous to facilitate sperm movement
membrane (together with peristaltic
seminiferous tubules join movements of tubules)
and lead into epididymis
b. Vas Deferens continuation of transports sperm (by means of
epididymis peristaltic movements) from
passes through epididymis to urethra
abdominal cavity; opens
into urethra
ampulla (swelling)
formed directly before
vas deferens joins
urethra
c. Ejaculatory Duct muscular tubule smooth muscle fibers contract;
forcing semen along the
urethra to the exterior (known
as ejaculation)
d. Urethra 2 ejaculatory ducts join Transports urine & semen to
to form urethra the exterior (never at the same
time)
1.3 Accessory Glands
These glands add secretions to the sperm, forming semen.
Gland Description Function
a. Seminal vesicles 2 glandular Secretes a thick, clear fluid,
structures lined with stimulating movement of sperm
a mucous Secretion contains fructose (supplies
membrane nutrients for energy to sperm)
Situated before Mucus in fluid aids in lubrication
each vas deferens
2
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