ECR L26
MALE REPRODUCTIVE TRACT
13/01/2000
PROF FRASER

During the first 6 weeks of development, you can not distinguish between the sexes, they just have an indifferent and bipotential gonad. It depends on which genes are switched on - only one is required: SRY.

SRY: the sex determining gene on the Y chromosome. It dictates the growth, causing tested to be developed. It is the earliest to be switched on - before the female sex determining genes are. Therefore, if there is no SRY, the gonad develops into an ovary.

Phenotypically - bipotential gonads.

bipotential gonads and the routes they can take

The set of ducts which aren’t used then become vestigial. Look in Moore and Persaud’s textbook for further details on development.

The genital ridges, where development starts - are situated on the dorsal wall of the embryo.

TDF - testis determining factor. The gene is SRY.

The testis has: medulla, cortex and tunica albuginia.

No SRY - other genes switch on and medullary and cortical regions develop into ovaries.

Females usually stop developing eggs because of a lack of hormones etc. Therefore there are more ways available to treat female infertility than there is for male.

The epididymis is derived from the Woolfian duct. During maturation the sperm become motile and start wiggling. Seminal vesicles supply the main component of seminal fluid of the ejaculate.

During ejaculation shunts block off the bladder. If the shunts are not working properly, it goes into the bladder, and you have retrograde ejaculation.

Prostate also contributes to the seminal fluid (along with a couple of other minor glands). It is a continuous duct system, so stuff can’t get "lost"! 150 million sperm are produced every day between the ages of 12 and 60.

Ledig cells get a signal to produce testosterojne from lutenising hormone (LH). The tubules themselves do not have a direct vascular supply.

Seminiferous tubules:
- Sertoli cells ("nurse" cells)
- Somatic cells - direct spermatogenesis.

Tight junctions are used to help protect against an attack on the "non-self" sperm cells that are being produced, as they have half the normal number of chromosomes.

The epididymis has a stereocilia epithelium. They are not real cilia because they do not beat. They are involved in fluid resorption. The vas deferens has a muscular coating.

A normal man has an intact system, but certain categories of men can produce no sperm because of a flaw in the reproductive tract. Now we can use a fine needle to remove sperm to use in reproduction.

The testes descend into the scrotal sac because they need to be maintained at a temperature of around 33-4 degrees Celsius. There are a lot of sweat glands and the blood vessels provide a good way of keeping it cool - the pampiniform plexus (arterial and venous). The venous supply coils around the artery, supplying a counter-current heat distribution system. This system is poor in wheelchair users and fighter pilots (and those wearing tight trousers).