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16.1 Male Reproductive SystemMale Reproductive System

Male Reproductive System

Male Reproductive System

TestesMale gonads that produce sperm.

During the last two months of fetal development, the testes descend into the scrotum through a canal.A membrane forms over the canal so that the testes cannot re-enter the abdomen.

Scrotum

Sperm will not develop at body temperature.Sac that contains the testes.A bit cooler than the abdominal cavity. This is important because

Vas deferens Tubes that carry sperm from testes to the urethra.

VasectomyA surgical procedure that involves cutting the vas deferens.

The vasa deferentia, the tubes which connect the testes to the prostate, are cut and closed. This prevents sperm produced in the testes to be in the ejaculated semen fluid (which is mostly produced in the prostate and the seminal vesicles).

Infertility results.

Tubal LigationDone to females.

The Fallopian tubes, which allow the sperm to fertilize the ovum and would carry the fertilized ovum to the uterus, are closed. This is sometimes referred to as getting one's "tubes tied."

UrethraChannel for urine & semen.

Seminal Fluid (Semen)Fluid secreted by three glands & the sperm that travels along the vas deferens and the ejaculatory duct to the urethra.Strong contractions force the semen into the urethra and out of the penis.

1) Seminal Vesicle-Fluids contain fructose & prostaglandins

Seminal Vesicle- The fructose provides the sperm with a source of energy.- The prostaglandins act as chemical messengers in the female system by triggering the rhythmic contraction of smooth muscle along the reproductive tract. (this assists the movement of sperm towards the egg)

2) Prostate Gland- Secretes an alkaline substance that protects sperm cells against the acidic environment of the vagina.

3) Cowpers Gland (Bulbourethral)- Secretes an alkaline mucous that counteracts possible acidity left in the urethra of the penis.

Sperm cells can exist for many weeks in the epididymis, but there life span is reduced when they come into contact with the various fluids in the semen.At body temperature, sperm cells will live only for 24-72 hours.When stored at -100oC, sperm cells have been known to remain viable for many years. Did You Know?Semen is:

60% secretions from the seminal vesicle30% secretions from the prostate10% secretions from the Cowpers gland

The ejaculatory duct regulates the movement of semen into the urethra. The urethra also serves as a pathway for urine. A sphincter regulates the voiding of urine from the bladder. At any given time, the urethra conducts either semen or urine, but never both. Erection is achieved as a result of blood flow into erectile tissue of the penis. Stimulation of the parasympathetic nervous system causes the arteries leading to the penis to dilate, therefore increasing blood flow. Veins that carry blood away from the penis become compressed. Ejaculation of semen is caused by stimulation of the sympathetic nervous system.

16.1 The Male Reproductive System Part 2

The Sperm Cell

23 chromosomes in the nucleus (head)b. Acrosome - enzyme filled cap on the head. Filled with digestive enzymes that dissolve the outer coating of the egg.c. Reduced cytoplasm since it is streamlined.d. Stored sugars and numerous mitochondria in the midsection.e. Flagellum

Spermatogenesis- Sperm production occurs in the testes, which maturation occurs in the epididymis. - The inside of each testis is filled with twisting tubules called seminiferous tubules.- These tubules are lined with sperm producing cells called spermatogonia. Contain 46 chromosomes. They divide via the process of meiosis to form spermatocytes. Now contain 23 chromosomes.Spermatocytes then differentiate into spermatids, which are immature sperm cells. - Within 9-10 weeks the spermatocytes differentiate into spermatids and then into sperm cells. - The sperm cells mature in the epididymus the coiled tube attached to the outer edge of the testes.

Sertoli cells are support cells that nourish the sperm.

Cortical Reaction:- Series of changes in outer layer of egg. Release of Ca2+ causes swelling. This swelling forms fertilization membrane which resists entry of additional sperm (polyspermy). Acrosomal Reaction:As soon as one sperm binds this causes depolarization of the egg membrane. This prevents polyspermy.

Hormonal Control of the Male Reproductive SystemTestosterone is produced in the interstitial cells of the testes. (These are the cells found between the seminiferous tubules). Testosterone has two main functions: 1) Stimulates spermatogenesis - the process by which spermatogonia divide and differentiate into mature sperm cells. 2) Influences the development of secondary sex characteristics at puberty. Secondary Sex Characteristics: Stimulates maturation of testes, penis, seminal vesicles & prostate gland. Promotes development of facial & body hair, growth of larynx (lowering of voice), strengthening of muscles. Increases the secretion of body oils (linked to development of acne). Associated with male sex drive.

Testosterone is used in the production of anabolic steroids. The production of sperm & testosterone in the testes is controlled by a negative feedback system:

Hormonal control of spermatogenesis:Once high levels of testosterone are detected by the hypothalamus a negative feedback system is activated. The hormone Inhibin inhibits further production of FSHHigh levels of testosterone increases sperm production. Positive Feedback.