Male Reproductive Male Reproductive SystemSystem

Biology 12Biology 12

Testosterone Testosterone

a male sex a male sex hormone hormone produced by the produced by the interstitial cells of interstitial cells of the testes. the testes.

SpermatogenesisSpermatogenesis

the process by which the process by which spermatogonia (immature sperm spermatogonia (immature sperm cells) divide and differentiate into cells) divide and differentiate into mature sperm cells.mature sperm cells.

Gonadotrophic Gonadotrophic hormoneshormones hormones hormones

produced by the produced by the pituitary gland pituitary gland that regulate the that regulate the functions of the functions of the testes in males testes in males and the ovaries and the ovaries in females. in females.

Follicle stimulating Follicle stimulating hormonehormone

FSH in males is a FSH in males is a hormone that hormone that increases sperm increases sperm production.production.

Luteinizing hormoneLuteinizing hormone

LH in males is a LH in males is a hormone that hormone that regulates the regulates the production of production of testosterone.testosterone.

Gonadotropin-releasing Gonadotropin-releasing hormonehormone

GnRH is a GnRH is a hormone hormone released by the released by the hypothalamus hypothalamus that stimulates that stimulates the secretion of the secretion of LH and FSH from LH and FSH from the pituitary the pituitary gland. gland.

1. What happens to animals when they are 1. What happens to animals when they are castrated?castrated?

Castration involves the removal of the Castration involves the removal of the testes from the male species.testes from the male species.

This removes the source of This removes the source of testosterone for the animal.testosterone for the animal.

It is a common practice when animals It is a common practice when animals are being bred for meat because it are being bred for meat because it makes the meat more tender and tasty. makes the meat more tender and tasty.

It also removes aggressive behavior, It also removes aggressive behavior, sex drive and the animal is sterile. sex drive and the animal is sterile.

2. Fully explain the role of testosterone in 2. Fully explain the role of testosterone in males. males.

Testosterone is a male sex hormone that Testosterone is a male sex hormone that is produced in the testes and it is the is produced in the testes and it is the most potent and abundant male hormone.most potent and abundant male hormone.

1. Testosterone is responsible for 1. Testosterone is responsible for spermatogensis, the process of producing spermatogensis, the process of producing mature sperm cells in the interstitial cells mature sperm cells in the interstitial cells of the testes. of the testes.

2. Testosterone is responsible for the 2. Testosterone is responsible for the development of secondary sex development of secondary sex characteristics that develop during characteristics that develop during puberty. Changes include:puberty. Changes include:

maturation of the testis and penis maturation of the testis and penis an increase in sex drivean increase in sex drive development of facial and body hairdevelopment of facial and body hair growth of larynx (voice box) causing growth of larynx (voice box) causing

deepening of the voicedeepening of the voice Strengthening of the musclesStrengthening of the muscles Increase in secretion of sebum (oil) Increase in secretion of sebum (oil)

leading to skin problems.leading to skin problems.

3. Explain how the negative feedback system 3. Explain how the negative feedback system controls the maintenance of sperm cells and controls the maintenance of sperm cells and testosterone levels. testosterone levels.

The negative feedback loop ensures that The negative feedback loop ensures that adequate numbers of sperm cells and adequate numbers of sperm cells and testosterone levels are maintained.testosterone levels are maintained.

The production of sperm and The production of sperm and testosterone in the testes is controlled testosterone in the testes is controlled by the hypothalamus and the pituitary.by the hypothalamus and the pituitary.

The hypothalamus releases GnRH which The hypothalamus releases GnRH which stimulates the release of LH and FSH stimulates the release of LH and FSH from the pituitary gland.from the pituitary gland.

LH promotes the production of LH promotes the production of testosterone in the interstitial cells.testosterone in the interstitial cells.

FSH targets the seminiferous tubules FSH targets the seminiferous tubules and stimulates the production of sperm. and stimulates the production of sperm.

Once the levels of testosterone reach a Once the levels of testosterone reach a high level the hypothalamus receives high level the hypothalamus receives the message that there is enough the message that there is enough testosterone and this activates the testosterone and this activates the negative feedback loop.negative feedback loop.

The hypothalamus releases less GnRH The hypothalamus releases less GnRH which then inhibits release of LH from which then inhibits release of LH from the pituitary. the pituitary.

4. What do we know about the feedback 4. What do we know about the feedback loop for production of sperm? loop for production of sperm?

We do not have a good understanding We do not have a good understanding at present of how the feedback loop at present of how the feedback loop functions for the production of sperm.functions for the production of sperm.

Scientists believe that FSH acts on the Scientists believe that FSH acts on the Sertoli cells that produce a peptide Sertoli cells that produce a peptide hormone called inhibin that sends a hormone called inhibin that sends a message via the feedback loop to the message via the feedback loop to the pituitary gland where it inhibits the pituitary gland where it inhibits the production of FSH.production of FSH.