The Male Reproductive System Chapter 48

Testes (singular: testis) Seminiferous tubules – coils of hollow tubes inside each Testes develop within the body cavity during embryological development but should descend into the scrotum about 2 months before birth Sperm are produced in the seminiferous tubules and then pass into the epididymis to finish maturation During ejaculation the sperm travel into the ejaculatory duct, then to the vas deferens and into the body cavity Then sperm travel through the prostate gland and out of the body through the urethra

Spermatogenesis Undifferentiated cells – spermatogonia (diploid) Mitosis  produce additional spermatogonia Some spermatogonia enlarge and become primary spermatocytes Primary spermatocytes undergo meiosis 1st meiotic division  2 secondary spermatocytes (haploid) 2nd meiotic division  4 spermatids Spermatids  develop into mature sperm Sperm: Head Nucleus covered by the acrosome – contains enzymes which will help it penetrate the egg plasma membrane Midpiece Contains mitochondria to provide energy for the flagellum Tail Flagellum

Accessory glands produce semen Seminal vesicles – paired Secrete a nutritive fluid rich in fructose (energy for the sperm) and prostaglandins (stimulate contractions in the uterus to help the sperm move up the female reproductive tract) Prostate gland – single An alkaline liquid that helps to neutralize the acidic environment of the vagina Bulbourethral glands – paired Release a mucous secretion to lubricate the urethra as well as the vagina

From male to female The penis Tip is the glans – covered by the foreskin which is removed during circumcision The shaft of the penis has 3 parallel columns of erectile tissue which contain numerous blood vessels Sexual stimulation dilates arteries and compresses veins, increasing blood flow in and preventing blood flow out, thereby causing erection Ejaculation releases semen

Regulatory hormones: Testosterone Produced by the interstitial cells between the seminiferous tubules in the testes Controls the male primary sex characteristics – the growth of the reproductive organs and spermatogenesis It also stimulates the development during puberty of the secondary sex characteristics – facial and body hair, muscle development, deepening of voice

Additional hormones needed Gonadotropin-releasing hormone Produced by the hypothalamus Causes the anterior pituitary to make its sex hormones: follicle-stimulating hormone and luteinizing hormone These are needed for spermatogenesis and testosterone production