The Reproductive System Male Reproductive System
Male Reproductive System
The Scrotum Sac of skin that hangs outside the abdominopelvic cavity at the root of the penis Contains paired testicles separated by a midline septum Its external positioning keeps the testes 3C lower than core body temperature (needed for sperm production) When external temperature is very cold, the scrotum becomes wrinkled as it is pulled closer to the warmth of the body wall
The Testes Each testis is divided into 250-300 lobules, each containing 1-4 seminiferous tubules Seminiferous tubules produce the sperm - stimulated by FSH released by pituitary Interstitial cells around the tubules produce androgens (testosterone) – stimulated by LH released by pituitary Once the sperm are made, they continue to the epididymis
The Testes
The Epididymis First part of male duct system Provides a temporary storage site for the immature sperm cells Trip through takes about 20 days Sperm learn how to swim here! When a male is sexually stimulated, the walls of the epididymis contract to propel sperm into the ductus deferens
Ductus Deferens and Ejaculatory Duct Propels sperm from the epididymis up into the pelvis, and back down to join up with the urethra Also called the vas deferens During an ejaculation, smooth muscles around the duct contract to create peristaltic waves that squeeze the sperm forward Vasectomy – cutting and ligating the ductus deferens, which is a nearly 100% effective form of birth control
Ductus Deferens and Ejaculatory Duct
Vasectomy
The Penis A copulatory organ designed to deliver sperm into the female reproductive tract Consists of an attached root and a free shaft that ends in the glans penis Prepuce, or foreskin – cuff of skin covering the distal end of the penis Circumcision – surgical removal of the foreskin after birth
The uncircumcised penis. The penis immediately after circumcision. The appearance of the circumcised penis after healing is complete.
The Penis Internal penis includes the urethra (which carries both semen and urine) and three cylindrical bodies of erectile tissue Erectile tissue – spongy network of connective tissue and smooth muscle riddled with vascular spaces; assists with erection and ejaculation Erection – during sexual excitement, the erectile tissue fills with blood causing the penis to enlarge and become rigid (which makes penetration easier)
The Penis
Accessory Glands: Seminal Vesicles Lie on the posterior wall of the bladder and secretes 60% of the volume of semen Join the ductus deferens to form the ejaculatory duct Sperm and seminal fluid mix in the ejaculatory duct and enter the urethra during ejaculation
Accessory Glands: Seminal Vesicles
Accessory Glands: Prostate Gland Doughnut-shaped gland that encircles part of the urethra inferior to the bladder Its milky fluid, which contains citrate (Vitamin C), enzymes, and prostate-specific antigen (PSA), accounts for one-third of the semen volume Fluid helps to activate sperm Fluid made enters the urethra during ejaculation
Accessory Glands: Prostate Gland
Accessory Glands: Bulbourethral Glands (Cowper’s Glands) Pea-sized glands inferior to the prostate Produce thick, clear mucus prior to ejaculation that neutralizes traces of acidic urine in the urethra
Accessory Glands: Bulbourethral Glands (Cowper’s Glands)
Semen Milky white, sticky mixture of sperm and accessory gland secretions Provides a transport medium and nutrients (fructose), protects and activates sperm, and facilitates their movement Prostaglandins in semen: Decrease the viscosity of mucus in the cervix Stimulate reverse peristalsis in the uterus Facilitate the movement of sperm through the female reproductive tract
Semen Sperm are most active at neutral pH, and can even die off at pH of 4 and below! However, vaginal pH is normally 3.5-3.9! Seminal fluid and prostate gland fluid has a pH of 7.2- 7.6, which will help to neutralize out the vagina… but this doesn’t last forever! pH in vagina will drop back down to 4.0 within 8 hours – so the lifetime of sperm in the vaginal canal is 8 hours max; lifetime in the uterus and fallopian tubes is about 48 hours Only 2-5 mL of semen are ejaculated, but it contains 50-130 million sperm per mL
Sperm Sperm have three major regions Head – contains DNA and has a helmetlike acrosome containing hydrolytic enzymes that allow the sperm to penetrate and enter the egg Midpiece – contains mitochondria spiraled around the tail filaments Tail – a typical flagellum produced by a centriole
Spermiogenesis: Spermatids to Sperm
Secondary Male Characteristics Deeper voice due to enlarged larynx Increased hair growth over body, especially in axillary and pubic regions, as well as on face Enlargement of skeletal muscles Increased heaviness of bones Long, narrow pelvis All are due to testosterone levels