Male reproductive system

Question 1

Describe primary sex characteristics:

Answer 1

Structures that play a direct role in reproduction

Question 2

Describe secondary sex characteristics:

Answer 2

Characteristics that are unique to males or females but do not play a direct role in reproduction

Question 3

Describe the primary sex characteristics of males:

Answer 3

Testes (male gonads), scrotum, epididymis, ductus deferens, penis, seminal vesicles, prostate gland, Cowper’s gland

Question 4

Describe the secondary sex characteristics of males:

Answer 4

Facial hair, body hair, deep voice, narrow hips, muscle development

Question 5

What are testes?

Answer 5

• Organs where sperm are produced
• Scrotum contains the testes and helps regulate temperature – when cold outside, the scrotum pulls the testes closer; when warm, the testes hang lower – away from the body

Question 6

What are the parts of the testes?

Answer 6

• Ducts (Vas) deferens
• Epididymis
• Septum
• Seminiferous tubules
• Lobule
• Testis

Question 7

Describe the penis:

Answer 7

• Male organ for intercourse
• Transfers sperm to female reproductive tract

Question 8

What are the parts of the penis?

Answer 8

• Glans penis – enlarged tip
• Shaft – main component
• Foreskin – surrounds and protects the glans penis
• Both sperm and urine exit the body via a tube in the penis called the urethra

Question 9

Describe an erection:

Answer 9

• Flow of blood to spongy tissue of penis during sexual arousal
• Erectile tissue expands
• Veins carrying blood away from penis are compressed - more blood is trapped

Question 10

What is sperm?

Answer 10

• Sperm production is called “spermatogenesis”
• Each testis can produce 100 million sperm/day
• Tadpole-shaped structure 0.06 mm long

Question 11

What are the parts of sperm?

Answer 11

• Head – contains nucleus with 23 chromosomes
  
  • Acrosome – cap of head – contains enzymes to penetrate egg
  • Mid-piece (body) – contains mitochondria
  • Tail – propels sperm forward

Question 12

Describe spermatogenesis

Answer 12

• Sperm develop from specialized cells (spermatogonium) in the testes
• Meiosis I forms two haploid secondary spermatocytes
• Meiosis II forms four spermatids (haploid)
• Developing sperm cells are nourished by Sertoli cells in the seminiferous tubules
• Immature sperm are transferred to the epididymis (a duct on the testes)
• Sperm mature and become motile in the epididymis

Question 13

Describe sperm release?

Answer 13

• When ejaculation occurs, sperm travels from the epididymis to the ductus deferens (vas deferens), which carries sperm to the penis
• Sperm travels out of the penis via the urethra
• Muscle contractions help to expel the semen
• Sperm is carried in a supportive fluid called seminal fluid

Question 14

What is seminal fluid?

Answer 14

• A mixture of fluids from the following glands that help to carry and nourish the sperm
• Seminal vesicle – produces mucous-like fluid containing fructose (helps to give the sperm energy)
• Prostate gland and Cowper’s (bulbourethral) gland – secrete mucous-like fluids that contain alkaline materials (neutralizes acids in the vagina)

Question 15

Describe how sex determination works:

Answer 15

• Androgens (male sex hormones) are triggered for release in an XY fetus
• A gene on the Y chromosome causes embryonic glands to develop as testes and secrete testosterone
• Testosterone causes pre-natal development of male genitalia and both sperm production and development of male secondary sex characteristics during puberty
• Male babies are born with a penis and testes (testes descend from abdomen shortly after birth) but cannot fertilize eggs until puberty

Question 16

Describe male puberty:

Answer 16

• Puberty begins at age 10-13 for males
• Hypothalamus increases production of gonadotropic releasing hormone (GnRH)
• GnRH causes anterior pituitary to release follicle stimulation hormone (FSH) and luteinizing hormone (LH)
  FSH and LH stimulate sperm production and testosterone release from testes
• Testosterone stimulates development of sex organs and secondary sex characteristics

Question 17

Describe regulation in the adult male - sperm production:

Answer 17

• GnRH triggers release of FSH and LH from anterior pituitary
• FSH causes cells in testes to produce sperm, also causes seminiferous tubules to release inhibin
• Inhibin acts on anterior pituitary to inhibit FSH
• A decrease in FSH means less inhibin will be released
• Negative feedback cycle continues to make sure sperm production is constant over time

Question 18

Describe regulation in the adult male - secondary sex characteristics:

Answer 18

• GnRH stimulates release of LH from anterior pituitary
• LH stimulates testes to release testosterone
• Testosterone promotes secondary sex characteristics (eg. Muscle development)
• Testosterone also inhibits LH release
• Negative feedback cycle keeps testosterone levels constant

Question 19

What is andropause?

Answer 19

• A decrease in testosterone beginning around age 40
• Can cause fatigue, depression, muscle and bone loss, drop in sperm production