Male reproduction



Drawing of the cross section of the male reproductive tract


Outline of the male reproductive tract

The rear of the male pig

The male reproductive tract dissected and labeled.

The male sex glands

Detail of the medial view of the left testes

Detail of the medial view of the left testes

Cut surface of the testes


Detail of a cross-section of the vas deferens


The preputial os

The preputial diverticulum opened on the ventral surface

Collection of the boar

Detail of the boar penis

Anatomy of the sperm

Sperm Morphology


Down the microscope the sperm should be seen to be active with forward motion.  In very good samples wave motion is seen

In contaminated samples agglutination of sperm can be seen.  This can also occur with chilling











37.4 μm


The normal sperm with a tail central to the head.  The tail is straight without any kinks.  The head is a smooth even head.


On the right we see proximal and distal cytoplasmic droplets.  This may have little significant impact on fertility.  The are more common in immature sperm.  The droplet comes from the acrosome/head cover which uncovers at ejaculation and then runs down the tail

Head abnormalities are not common.  The photographs illustrate a range of abnormalities.  Detached heads can be common in certain boars.  If the head is abnormal attachment in the oviduct and to the egg will be impaired.


Tail abnormalities are common with the variety of bent and coiled tails.  Deformities of the tail interferes with the sperms ability to swim in the oviduct and through the zona pellucida

Poor semen collection techniques will result in increased contamination of the sample.  This may be recognised by the clear presence of bacteria in the sample

Review collection routines. Note preputial fluid will kill semen.  The semen sample may also smell


Using stains such as Eosin/Nigrosin stain the sperm may be clearer.  Some of the stains also allow an assessment of whether the sperm were alive or dead.


The sample on the left contain a dead sperm in the middle, one detached head, one bent tail and  two normal sperm

What are the abnormalities you can see in the sample on the right?



While semen morphology is interesting, please note that only in extreme cases can fertility be affected by abnormal sperm cells.  Second samples should be examined if more than 30% of the sperms  cells examined are abnormal.

 Also note that a single examination may be almost meaningless.  The identification of a sub-fertile boar takes several serial semen samples and record analysis

The female filters out many of the abnormal sperm as they enter the oviduct.  It has been shown that in the horse, despite being inseminated with semen samples with 85% abnormal sperms, this resulted in 90% normal sperm in the oviduct.


Remember you are examining the population of sperm not the individual