34.2 Reproductive Processes
KEY CONCEPT
Human reproductive processes depend on cycles of hormones.

34.2 Reproductive Processes
Eggs mature and are released according to hormonal cycles.
potential egg
• Follicle-stimulating hormone
(FSH) and lutenizing hormone
(LH) regulate egg production.
– meiosis produces eggs and polar bodies
– each egg has 23 chromosomes
– meiosis is completed at fertilization
Meiosis I
Completed
Meiosis II
Completed only after sperm enters first polar body ovum (egg) second polar body

34.2 Reproductive Processes
• FSH, LH, and estrogen stimulate the release of eggs.
– follicle ruptures at ovulation
– egg travels into fallopian tube
– ruptured follicle becomes corpus luteum fallopian tube uterus
5 to 7 days to uterus follicle ovary egg cell egg released uterine wall corpus luteum

34.2 Reproductive Processes
Eggs mature and are released according to hormonal cycles.
• The menstrual cycle has three phases.
– flow phase: endometrium sheds
– follicular phase: ovulation occurs
– luteal phase: corpus luteum forms

34.2 Reproductive Processes
• The menstrual cycle stops at menopause.
– cycle continues until a woman’s mid-40’s or 50’s
– decline in hormone levels make cycles irregular
– eventually, cycle stops altogether

34.2 Reproductive Processes
Sperm production in the testes is controlled by hormones.
• Testosterone, FSH, and LH stimulate sperm production.
– one sex cell divides into four sperm potential sperm
– each sperm has 23 chromosomes
Meiosis I
Meiosis II
4 sperm cells

34.2 Reproductive Processes
• Sperm cells fully mature in the epididymis.
– head contains acrosome
– midpiece contains ATP
– tail allows mobility acrosome head nucleus with 23 chromosomes mitochondria midpiece tail

34.2 Reproductive Processes
Fertilization occurs when a sperm cell joins an egg cell.
• Sperm penetrates an egg.
– membrane keeps out other sperm
– nucleus of sperm joins with egg
– zygote formed

34.2 Reproductive Processes
• Multiple zygotes can result from fertilization.
– identical twins from the same egg
– fraternal twins from two separate eggs
• Infertility makes reproduction difficult or impossible.

34.2 Reproductive Processes
Sexually transmitted diseases affect fertility and overall health.
• Sexually transmitted diseases (STDs) are passed from one person to another during sexual contact.
– bacterial STDs include chlamydia, syphilis, gonorrhea
– viral STDs include hepatitis B, genital herpes, human papillomavirus, and HIV
HIV

34.2 Reproductive Processes
• Bacterial STDs can be treated, and in many cases, cured with antibiotics
• Viral STDs can be treated, but there is no cure for these diseases.
• STDs attack reproductive organs.
– can cause infertility
– untreated, some can be fatal
• STDs can be avoided by abstinence or by using a condom.
A parasite causes trichomoniasis, which can affect fertility.