1. Reproductive Strategies + Male Reproductive System

2. Reproductive Strategies
In order for fertilization and development to occur, the gametes and developing organism require a high moisture environment
There are two main reproductive strategies determined by this necessity:
External Fertilization
Internal Fertilization

3. Not only is fertilization case by case, but so is development.
Examples:
Vertebrate Fertilization Development
Fish External External
Amphibians External External
Reptiles Internal External
Birds Internal External 
Mammals Internal Internal

4. External Fertilization
occurs outside the female’s body.
many eggs are necessary.
because of the low rate of fertilization success.
The eggs and sperm are both released into the environment, where fertilization occurs
The eggs are exposed to the environment and also predators.
occurs mainly in aquatic animals like fish and amphibians.

6. Internal Fertilization
occurs inside the female’s body.
many fewer eggs are needed. 
much higher rate of fertilization success.
requires a special delivery organ to deposit the sperm (penis)
used mainly by land animals (terrestrial) like reptiles, birds, and mammals in environments where moisture is low

8. Human Reproductive Systems

9. The Reproductive System
The main function of the reproductive system is to produce sex cells (sperm and egg).
Gonads – primary sex organs
Testes in males
Ovaries in females
Gonads produce gametes (sex cells) and secrete hormones
Sperm – male gametes
Ova (eggs) – female gametes

10. Male Reproductive System
Testes
Duct system
Epididymis
Vas deferens
Urethra
Accessory organs
Seminal vesicle
Prostate gland
Bulbourethral gland
External genitalia
Penis
Scrotum

11. Male Reproductive System

12. Testes Production of sperm cells in males divided it into lobules
Each lobule contains one to four seminiferous tubules
Tightly coiled structures
Function as sperm-forming factories- site of spermatogenesis
Empty sperm into the rete testis
Sperm travels through the rete testis to the epididymis
Tubes that store the sperm
Epididymis stores and matures sperm for up to 20 days
Interstitial cells in the testes produce androgens such as testosterone

13. Major Components
Vas Deferens- Carries sperm from the epididymis to the ejaculatory duct.
Vasectomy – cutting of the ductus deferens at the level of the testes to prevent transportation of sperm.
Urethra- extends from the base of the urinary bladder to the tip of the penis
Carries both urine and sperm
Sperm enters from the Vas Deferens

14. Male Reproductive System

15. Semen Mixture of sperm and accessory gland secretions
Advantages of accessory gland secretions
Fructose provides energy for sperm cells
Alkalinity of semen helps neutralize the acidic environment of vagina
Semen inhibits bacterial multiplication
Elements of semen enhance sperm motility

16. Seminal Vesicles
Seminal Vesicles- glands located at the base of the bladder
Produces a thick, yellowish secretion (60% of semen)
Fructose (sugar)
Vitamin C
Prostaglandins
Other substances that nourish and activate sperm

17. Male Reproductive System

18. Prostate Gland Encircles the upper part of the urethra
Secretes a milky fluid
Helps to activate sperm
Enters the urethra through several small ducts

19. Bulbourethral Glands Pea-sized gland inferior to the prostate
Produces a thick, clear mucus
Cleanses the urethra of acidic urine
Serves as a lubricant during sexual intercourse
Secreted into the penile urethra

20. Male Reproductive System

21. External Genitalia Scrotum Penis
Divided sac of skin outside the abdomen
Maintains testes at 3°C lower than normal body temperature to protect sperm viability
Penis
Delivers sperm into the female reproductive tract

22. Anatomy of a Mature Sperm Cell
The only human flagellated cell
DNA is found in the head
The acrosome region helps to dissolve the outer layer of the egg, so the sperm can enter.
Figure 16.5b

23. Hormones in Males Testosterone:
The most important hormone of the testes
Produced in interstitial cells
Functions of testosterone
Stimulates reproductive organ development
Underlies sex drive
Causes secondary sex characteristics
Deepening of voice
Increased hair growth
Enlargement of skeletal muscles
Thickening of bones
Follicle Stimulating Hormone (FSH), Luteinizing Hormone:
Stimulate the production of testosterone and sperm cells