LAB 6.1 Male reproductive system
Side view of reproductive system of the bull.
1. Seminal vesicle
3. Cavernosus muscles
4. Sigmoid flexure
5. Vas deferens
The video shows the above diagram, followed by the reproductive systems
of the bull and boar.
The video also describes how the boar's bulbourethral glands are
related to 'boar taint' caused by androstenone.
Androstenone is a pheromone (a hormone transmitted from the boar to the
- The paired testes of male farm mammals are located in a
bag called the scrotum where they can be maintained several
below body temperature for the efficient production of spermatozoa
or sperm. Here are two
boar testes, the one on
the left sliced open.
- Each testis can be raised by the cremaster externus
of cremaster muscles may appear in carcasses of sows and gilts and so
be used to identify male carcasses!}.
- The connective tissue round the testis is called the tunica
it is white with a good blood supply.
- Spermatozoa are produced in seminiferous tubules tightly
into the oval shape of the testis. The
above shows one tubule under the microscope. The higher power image
shows part of the tubule (lumen downwards) with meiotic divisions
leading to the formation of spermatozoa, whose tails can be seen
at the bottom of the image.
- The many seminiferous tubules in each testis open into a
labyrinth of tubes
called the rete testis. Immature spermatozoa from the rete
pass in a number of efferent ducts to a further tubular system, the epididymis,
located on the surface of the testis,
as shown in the image below.
- Spermatozoa mature during storage in the epididymis and are
the urethra during mating by peristalsis of the vas deferens.
- The urethra is located ventrally in the penis.
- Seminal fluid to carry the spermatozoa is produced by the
vesicles, by the prostate gland, and by the paired bulbo-urethral
glands (= Cowper's glands). The glands are located along the
near to the bladder. The image below shows the seminal vesicles
of a boar.
- The penis has a sigmoid flexure or S-shaped bend
length. The sigmoid flexure is straightened out when the penis is
for mating. This occurs when a pair of muscles, the ischio-cavernosus
compress the veins which drain the blood from the penis. Arterial blood
pressure then expands the volume of vascular tissue in the penis.
- The ischio-cavernosus muscles are attached to the ischium
trimmed stump of the muscle may be seen on dressed sides of beef as a pizzle
eye. The pizzle eye is poorly developed in steer carcasses and is
and darker in bull carcasses.
- During the embryonic development of both mammals and birds, the
are formed from tissue located near to the kidneys. In male mammals,
testes normally move to the scrotum outside the body cavity, and they
through the body wall in the inguinal canal. The testes are
to the inside of the scrotum by the gubernaculum which is
in fetal animals and is responsible for pulling the testis through the
- The layers of connective tissue that cover each testis are the
vaginalis communis and (2) the inner layer formed by the tunica
vaginalis propria. Both layers are derived from modified layers of
peritoneum gathered by the testes during their migration. The inner
supports the blood vessels and nerves to the testis.
- In cryptorchid pigs or ridgelings, movement of the testes
the inguinal canal is incomplete and they do not reach the scrotum.
abnormality causes infertility, but an older cryptorchid pig may still
develop boar taint like a normal boar. The cause of the
is not fully known but the normal mechanism of testicular movement
to involve the action of testosterone on the genito-femoral nerve which
then produces a peptide that activates the gubernaculum.