Chapter 39 - Human Reproduction

Human reproductive system

• male reproductive system

  • parts [Figs. 39.12, 39.13, Table 39.1]

    1. testes

       • site of sperm production

       • development of sperm starts at puberty

       • located in the scrotum

       • contains seminiferous tubules - contains the cells that go through meiosis>sperm [Fig. 39.14]

       • sperm structure

       • produces sex hormone, testosterone

    2. epididymis

    3. vas deferens

    4. urethra

    5. seminal vesicles - add fructose to semen

    6. bulbourethral glands - add mucus to semen

    7. prostate gland - adds acid neutralizers to semen

• millions of sperm are produced every day

• female reproductive system

  • parts [Fig. 39.16, Table 39.2]

    1. ovaries

       • site of egg production

       • development of eggs starts in the fetus

       • follicle = immature egg + its nourishing cells

       • each month, 12 follicles resume maturation, but only 1 matures into an egg [Fig. 39.17]

    2. fallopian tube

       • site of fertilization

    3. uterus

       • inner lining rich in blood vessels (endometrium)

       • outer muscular wall (myometrium)

    4. cervix

    5. vagina

  • menstrual cycle is  controlled by complex hormonal interactions [Fig. 39.19]

    • brain produces hormone that triggers a follicle to grow

    • follicle produces estrogen > make thick uterine lining

    • corpus luteum (former nourishing cells) produces estogen and progesterone > thicken uterine lining more

    • if fertilization occurs: embryo > keep corpus luteum

    • if no fertilization: corpus luteum breaks down > uterine lining is shed (menstruation)

Sexual intercourse and conception

• Sexual intercourse

  • purpose: depositing of sperm in the vagina

  • erection is the result of increased blood flow to the penis

  • ejaculation results from muscular contractions around the epididymus, vas deferens, and urethra

  • 3 - 4 ml of semen with 300-400 million sperm

  • females also have increased blood flow to parts of the reproductive tract

  • orgasm is not required for fertilization

• Fertilization

  • egg lives for 1 day and sperm live 1-2 days

  • fertilization occurs in the fallopian tube

  • egg has chemical sperm attractant

  • egg has 2 barriers around it: layer of cells and layer of jelly

  • sperm tip contains enzymes to break through these barriers

  • only 1 sperm will fertilize an egg

  • fusion causes completion of meiosis [Fig. 39.20]

  • egg + sperm = zygote

• Beginning of development [Fig. 39.21]

  • cell divisions occur while zygote is moving to uterus

  • zygote becomes a hollow ball of cells

    • outer part interacts with uterine wall > placenta

    • inner part > embryo

Contraception

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Sexually Transmitted Disease (STDs)

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© Carol L. Wymer, 2003