Reproduction Flashcards
What is the male reproductive tract?
The male reproductive tract is external and consists of a penis and a pair of testes enclosed within the scrotum.
What are the testes?
The testes are gonads i.e. the structures responsible for the production of sperm - a process called spermatogenesis.
They are also the primary source of the male sex hormones known collectively as androgens.
The best known example of an androgen is testosterone.
The testes are composed of a series of coiled tubes called what?
Seminiferous tubules
What are the 2 important cell types in the seminiferous tubules?
- Sertoli cells which are responsible for sperm production
- Leydig cells which are responsible for testosterone production and release
Leydig cells are sometimes called interstitial cells.
Where do individual seminiferous tubules drain into?
Structures called the rete testes
What do the rete testes drain into?
The rete testes drain into a highly coiled tube called the epididymis, which in turn drains into the vas deferens.
The vas deferens from each testicle dilates and forms a structure called the ampulla of the vas deferens.
The ampulla merges with the outflow from the seminal vesicle to form a structure called the ejaculatory duct.
What is the general organisation of the male reproductive tract?
Figure 9.1 PG 133
What is the cross section through a testicle?
Figure 9.2 PG 134
What is the process of ejaculation?
The ejaculatory ducts enter the prostate gland, merge together, and enter the urethra which allows sperm and the secretions of various glands to be released from the penis.
What is ejaculated from the penis?
Whilst sperm are produced in the testes and mature as they move through to the epididymis, it is semen which is ejaculated.
What is semen?
Semen is a mixture of sperm and secretions of the seminal vesicle and prostate gland.
These secretions provide nutrients for the sperm cells, are alkaline ( to buffer the acidic secretions of the female reproductive tract) and contain anticoagulants.
What is a typical ejaculatory volume?
2 - 5 ml, 80% of which is made up from glandular secretions.
What is the production of functional sperm known as?
It is known as spermatogenesis.
This begins at puberty and continues, although at a reduced efficiency, until death
Once spermatogenesis is initiated how much sperm does a male produce each day?
Once spermatogenesis is initiated a male may produce 200 -250 million sperm a day.
What is the first step of spermatogenesis?
It is the production from diploid germ cells of cells called spermatogonia.
Diploid means that the cells have a full complement of chromosomes, i.e. 23 pairs comprising 22 pairs of autosomes and one each of the X and Y chromosomes (the so called sex chromosomes)
What does haploid mean?
Haploid
A cell that contains a single set of chromosomes. For example, human egg and sperm cells are haploid, containing 23 chromosomes.
What does diploid mean?
Diploid
A cell that contains two complete sets of chromosomes. For example, most cells in humans are diploid, containing 46 chromosomes in total.
How are primary and secondary spermatocytes formed?
Spermatogonia undertake 2 further mitotic cell divisions to form primary spermatocytes which are still diploid.
They then begin to undergo meiotic cell divisions to form structures called secondary spermatocytes.
How are spermatids formed?
Secondary spermatocytes undergo a further meiotic cell division to form spermatids. These are now haploid cells.
They contain one of each pair of autosomes and one of the sex chromosomes - making 23 chromosomes in total
What are autosomes?
any chromosome that is not a sex chromosome.
What is the final stage in the production of sperm?
Maturation and formation of sperm cells from the spermatids - a process called spermiogenesis
What is the cross section through a seminiferous tubule?
Figure 9.3 PG 135
What happens as the development from spermatogonia to sperm occurs?
As the development from spermatogonia to sperm occurs, the cells move through the Sertoli cells towards the lumen of the seminiferous tubules.
How long does it take to produce sperm cells from spermatagonia?
about 70 days