KEY CONCEPT Human reproductive processes depend on cycles of hormones.
Eggs mature and are released according to hormonal cycles. potential egg first polar body second polar ovum (egg) Meiosis I Completed Meiosis II only after sperm enters 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
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 egg cell egg released corpus luteum uterine wall ovary follicle uterus 5 to 7 days to uterus
Eggs mature and are released according to hormonal cycles. The menstrual cycle has three phases. follicular phase: ovulation occurs luteal phase: corpus luteum forms flow phase: endometrium sheds
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
Sperm production in the testes is controlled by hormones. Testosterone, FSH, and LH stimulate sperm production. one sex cell divides into four sperm each sperm has 23 chromosomes potential sperm 4 sperm cells Meiosis I Meiosis II
Sperm cells fully mature in the epididymis. head contains acrosome midpiece contains ATP tail allows mobility acrosome head midpiece tail mitochondria nucleus with 23 chromosomes
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
Multiple zygotes can result from fertilization. identical twins from the same egg fraternal twins from two separate eggs Infertility makes reproduction difficult or impossible.
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
Viral STDs can be treated, but there is no cure for these diseases. Bacterial STDs can be treated, and in many cases, cured with antibiotics A parasite causes trichomoniasis, which can affect fertility. 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.