Page 71 - 86 human physiology part-2

Chapter 15

Leydig in the testicles.

Branch of the abdominal aorta. It is
Testicular arteries a paired artery. Each passes Supplies blood to the testes.
(Gonadal arteries) obliquely downward and laterally
behind the peritoneum.
Tubular structure that receives urine from
Connects bladder to outside body,
Urethra bladder and carries it to outside of the body.
about 8 inches long.
Also passage for sperm.
During ejaculation the smooth muscle in the
Muscular tubes connecting the left vas deferens wall contracts, propelling sperm
and right epididymis to the
Vas deferens forward. Sperm are transferred from the vas
ejaculatory ducts to move sperm. deferens into the urethra, collecting fluids from
Each tube is about 30 cm long.
accessory sex glands en route

Composition of human semen

The components of semen come from two sources: sperm, and "seminal plasma". Seminal plasma,
in turn, is produced by contributions from the seminal vesicle, prostate, and bulbourethral glands.

Seminal plasma of humans contains a complex range of organic and inorganic constituents.

The seminal plasma provides a nutritive and protective medium for the spermatozoa during their
journey through the female reproductive tract. The normal environment of the vagina is a hostile one
for sperm cells, as it is very acidic (from the native microflora producing lactic acid), viscous, and
patrolled by immune cells. The components in the seminal plasma attempt to compensate for this
hostile environment. Basic amines such as putrescine, spermine, spermidine and cadaverine are
responsible for the smell and flavor of semen. These alkaline bases counteract the acidic environment
of the vaginal canal, and protect DNA inside the sperm from acidic denaturation.

The components and contributions of semen are as follows:

APPROXIMATE
GLAND DESCRIPTION
%
Approximately 200- to 500-million spermatozoa (also called sperm
testes 2-5% or spermatozoans), produced in the testes, are released per
ejaculation
amino acids, citrate, enzymes, flavins, fructose (the main energy
source of sperm cells, which rely entirely on sugars from the
seminal 65-75% seminal plasma for energy), phosphorylcholine, prostaglandins
vesicle
(involved in suppressing an immune response by the female
against the foreign semen), proteins, vitamin C
acid phosphatase, citric acid, fibrinolysin, prostate specific antigen,
proteolytic enzymes, zinc (serves to help to stabilize the DNA-
prostate 25-30% containing chromatin in the sperm cells. A zinc deficiency may
result in lowered fertility because of increased sperm fragility.
Zinc deficiency can also adversely affect spermatogenesis.)
bulbourethral < 1% galactose, mucus (serve to increase the mobility of sperm cells in
glands the vagina and cervix by creating a less viscous channel for the

286 | Human Physiology