1. The Reproductive System
Male Reproductive System

2. Male Reproductive System

3. 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 3C 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

4. The Testes
Each testis is divided into 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

5. The Testes

6. 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

7. 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

8. Ductus Deferens and Ejaculatory Duct

9. Vasectomy

10. 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

11. The uncircumcised penis.
The penis immediately after circumcision.
The appearance of the circumcised penis after healing is complete.

12. 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)

13. The Penis

14. 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

15. Accessory Glands: Seminal Vesicles

16. 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

17. Accessory Glands: Prostate Gland

18. 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

19. Accessory Glands: Bulbourethral Glands (Cowper’s Glands)

20. 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

21. Semen
Sperm are most active at neutral pH, and can even die off at pH of 4 and below!
However, vaginal pH is normally !
Seminal fluid and prostate gland fluid has a pH of , 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 million sperm per mL

22. 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

23. Spermiogenesis: Spermatids to Sperm

25. 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