Male Reproductive Anatomy Functions of male Reproductive System: produce gametes deliver gametes protect and support gametes

Function #1: Production of Sperm Spermatogenesis occurs in the testes after puberty. From the testes they are deposited into the epididymas where they are stored. and then vas deferens to begin swimming and prepare to be deposited into the female. Sperm cells are haploid and are produced in the tubules within the testes.

Spermatogenesis occurs in the seminiferous tubules Spermatogenesis occurs in the seminiferous tubules. Here spermatogonia cells (diploid) start to undergo meiosis. Sertoli cells nourish the developing sperm. Interstitial cells outside the tubules produce the hormone testosterone.

A microscopic image shows the Seminiferous Tubules. Identify the structures that are shown here. A. Spermatogonia B. Sperm C. Interstitial cells D. Center of seminiferous tubules E. Sertoli cells C A E D B

Sperm Millions of sperm are produced in an average male every day. If they are not ejaculated, they are reabsorbed after a couple of weeks by the body and recycled. Sperm are very stream-lined for what they do. They don’t have any extraneous “gear.” No food for the trip and no proteins on their surface. Just DNA with a tail. How did evolution select for this in sperm? Flagellum: propulsion Mitochondria: power Nucleus:DNA Acrosome: a way into the egg… (digestive enzymes)

Function #2: Delivery of the Sperm In order to deliver the gametes into the females’ reproductive tract and to the females’ gametes, the penis must become erect. Blood flows into the erectile tissue and the build up of blood pressure causes the penis to become rigid. Further stimulation of the nerves on the penis triggers a series of smooth muscle contractions that propel the sperm out of the penis. The sensation of orgasm occurs when the control of the body rapidly switches from one nervous center (the parasympathetic) to another (the sympathetic).

Protection of the Sperm Function #3: Protection of the Sperm Of the millions of sperm cells ejaculated into a female, only a few will survive to meet the egg a couple of days later. This is because the environment into which the sperm will enter is very harsh and the vast majority die: no energy source very acidic The male body provides these things to the sperm cell to aid it on its journey to find the female gamete (the egg): sugar a basic solution to neutralize the acid Why is the environment so harsh? What does evolution say?

So once sperm are formed and then sped on their way out of the vas deferens by muscular contractions, they are mixed with three solutions on their way, and then ejaculated into the female reproductive tract. Seminal Vesicles: fructose-rich fluid: energy for mitochondria protaglandins: initiate female muscle contractions Prostrate Gland: alkaline (basic) fluid: neutralize the acids in the vagina Bulbourethral Gland: lubrication for penis to enter vagina and for sperm to move more easily through the urethra The resulting mixture is called Semen. an ejaculation releases about 3 mL of semen

At puberty the hypothalamus releases gonadotropin-releasing hormone (GnRH). GnRH stimulates the pituitary to produce luteinizing hormone (LH) and follicle stimulating hormone (FSH) LH causes the interstitial cells to produce testosterone. LH and FSH stimulate spermatogonia in the testes. To much testosterone or INHIBIN triggers a negative feedback loop which stops production of GnRH If FSH was suppressed, but LH continued a man would be infertile but not impotent.

Secondary Sexual Characteristics Sperm production starts in boys at puberty. The production of testosterone also triggers other secondary characteristics. Voice deepens Start to grow body hair Muscles start to develop height increases Testes drop

So to review...