MALE REPRODUCTION

1. MALE REPRODUCTION Ryan Greene, Aaron Zeiler, Keiah Townsend

2. Anatomy

3. The role of testosterone in males. The role of the testosterone is needed primarily in 3 different ways. • The development of the male genitalia ( specifically during embryonic development in week 7). • The development of secondary sexual characteristics during puberty such as facial hair, vocal cords, muscle mass, and height. • The initiation and maintenance of sperm and the male sex drive.

4. Testis Each testis is made of tubular structures (seminiferous tubules) from these tubules sperm is produced. The Seminiferous Tubules then go on to produce sperm cells throughout the male life. A basement membrane surrounds these tubules. Between the seminiferous tubules are groups of cells called interstitial or Leydig cells that produce the male sex hormone, testosterone.

7. Spermatogenesis. Process in which sperm cells undergo meiosis. It is the male version of gametogenesis. This occurs in the testes, in the seminiferous tubules. In the process, the spermatogonium go through mitosis produce a number of cells called 2 daughter cells in which one stays a spermatogonium and the other becomes a primary spermatocytes which divides by meiosis into a secondary spermatocyte which then is divided again to form spermatids which differentiate into sperm cells which will grow to be mature spermatozoa (sperm cells). http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter28/animation__spermatogenesis__quiz_1_.html

9. Spermatogenesis Spermatogoniumare found at or near the basement membrane. They have a high rate of cell division by mitosis to produce spermatogonia. The spermatogonium grow to form Primary Spermatocytes which have completed S-phase. The Primary spermatocytes separate the homologous pairs of chromosomes in meiosis I(reduction division) to form the haploid Secondary Spermatocytes. The spermatids are formed from the separation of the sister chromatids in meiosis II. The spermatids are found in association with the sertoli cells which nourish the spermatids as they differentiate into spermatozoa. The rate of spermatozoa is high and continuous throughout the life on the sexually mature male.

10. Role of reproductive organs The causes of the 2 stages of meiosis in spermatogenesis is due to 2 hormones secreted by the anterior pituitary (FSH (Follicle-stimulating hormone) and LH(Luteinizing hormone)). FSH stimulates the primary Spermatocytes which carry out meiosis I to separate homologous pairs of chromosomes and produce secondary spermatocytes. LH stimulates the interstitial cells to produce testosterone. Testosterone stimulates the maturation of secondary spermatocytes through meiosis and differentiation to spermatozoa.

12. Mature Sperm

13. Mature Sperm The acrosome vesicle contains the enzymes required to digest its way though the ovum wall. Haploid nuclei contains the paternal chromosome set The tail of the sperm contains mitochondria which synthesis ATP to provide the energy for the movement of the tails structure. Protein fibres add longitudinal rigidity and provide a mechanism of propulsion.

14. Hormones in Spermatogenesis • FSH stimulates primary spermatocytes to undergo the first division of meiosis to form secondary spermatocytes • Testosterone stimulates the development of secondary spermatocytes into mature sperm • LH stimulates the secretion of testosterone by the testis

15. Production of semen Epididymis: testicle fluids are removed and the sperm concentrated sperm mature here and develop the ability to swim Seminal vesicles: adds nutrients that include fructose sugar for respiration mucus to protect sperm in the cell Prostate: adds fluids that neutralise the vaginal acids and minerals ions mineral ions During periods of sexual arousal, the penis becomes erect as blood fills its spongelike tissues. The sperm cells are mixed with secretions from the prostate gland, seminal vesicles, and Cowper's glands. These secretions and the sperm cells constitute the semen.

16. Semen in the Female Reproductive Tract • A man usually ejaculates 2-5 mL of semen and each milliliter may contain 50-130 million sperm. Once in the female reproductive tract prostaglandins in the semen cause thinning of the mucus at the opening of the uterus and stimulate contraction of the uterine muscles which help move the semen up the uterus. • The alkalinity of the semen helps neutralize the acidic environment of the vagina, protecting the sperm and increasing their motility. When first ejaculated, the semen coagulates, making it easier for uterine contractions to move it along; then anticoagulants liquefy the semen, and the sperm begin swimming through the female tract.

18. Gametogenesis • Both start with proliferation of cells by mitosis. • Both involve the cell growth before meiosis. • Both involve the two divisions of meiosis.

19. Spermatogenesis Millions produced daily Released during ejaculation Sperm formation starts during puberty in boys Sperm production continues throughout the adult life of men Four sperm are produced per meiosis Oogenesis One produced every 28 days Released on about day 14 of menstrual cycle by ovulation The early stages of egg production happen during fetal development in females Egg production becomes irregular and then stops at the menopause in women Only one egg is produced by meiosis Gametogenesis