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The male reproductive system

The male reproductive system. Humans have 2 types of gametes: Males have sperm – small, motile, many Females have eggs – large, non-motile, few Male and female reproductive systems are designed to maximize chance of fertilization.

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The male reproductive system

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  1. The male reproductive system

  2. Humans have 2 types of gametes: • Males have sperm – small, motile, many • Females have eggs – large, non-motile, few • Male and female reproductive systems are designed to maximize chance of fertilization

  3. Sperm production and maturation:Testes (spermatogenesis and testosterone) • Inside scrotum • Begin development inside abdomen, only descending into scrotum in the last 2 months of gestation • Contain seminiferous tubules – sperm cells are made here (spermatogenesis) • Sertoli cells nourish sperm cells

  4. Acrosome contains enzymes that allow sperm to penetrate egg • Head has DNA and nucleus • The tail is also called a flagellum (for swimming)

  5. Interstitial cells: lie between seminiferous tubules • Produce androgens (male hormones) (mainly testosterone) • Testosterone involved in spermatogenesis, and maturation of testes and penis at puberty

  6. Brain break • Why does it take 300 million sperm to fertilize one egg?

  7. Because they won't stop to ask directions.

  8. Epididymis • Where sperm mature • Tightly coiled tubule (about 20 ft long) • Just outside each testis • Believed that some defective cells are destroyed here by the immune system

  9. Transport: ductus deferens (vas deferens) • Joined to epididymis • Goes from testes, through inguinal canal and into abdomen to the urethra • What they cut in a vasectomy to sterilize a man • A hernia is what happens when inguinal canal gets stretched and a bit of intestine squishes through. Can get painful and sometimes strangulated (circulation cut off)

  10. Seminal fluids • Three glands contribute to seminal fluid for sperm to swim in • Seminal fluid + sperm = semen • 1: Prostate gland: alkaline fluid to protect sperm while in the female • 2: seminal vesicles: sugar solution for energy • Prostoglandins: cause contractions of female reproductive muscles • 3: Cowper’s glands: lubricating fluid

  11. Penis • Copulatory organ • Has enlarged end (glans penis) covered in foreskin at birth (gets “smegma” if you don’t clean under it) • Can be removed by circumcision • Contains urethra, which is path taken by sperm during intercourse • During erection, sphincter from bladder closed off so no entry of urine • Penis fills with blood (in blood sinuses) and becomes erect • Impotency: inability to get an errection (sometimes psychological, sometimes hormone imbalance) • Deposits 150 – 300 million sperm outside cervix of female

  12. Ejaculation • Process by which semen leaves a man’s body via the penis • Path of sperm: • Epididymis  vas deferens  (seminal fluid comes form the 3 glands)  urethra  vagina

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