34.2 Reproductive Processes TEKS 6G, 10A The student is expected to: 6G recognize the significance of meiosis to sexual reproduction and 10A describe the interactions that occur among systems that perform the functions of regulation, nutrient absorption, reproduction, and defense from injury or illness in animals

34.2 Reproductive Processes TEKS 6G, 10A KEY CONCEPT Human reproductive processes depend on cycles of hormones.

34.2 Reproductive Processes TEKS 6G, 10A Eggs mature and are released according to hormonal cycles. 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 potential egg first polar body second polar body ovum (egg) Meiosis I Completed Meiosis II Completed only after sperm enters

34.2 Reproductive Processes TEKS 6G, 10A 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

34.2 Reproductive Processes TEKS 6G, 10A 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 TEKS 6G, 10A 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 TEKS 6G, 10A 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

34.2 Reproductive Processes TEKS 6G, 10A acrosome head midpiece tail mitochondria nucleus with 23 chromosomes Sperm cells fully mature in the epididymis. –head contains acrosome –midpiece contains ATP –tail allows mobility

34.2 Reproductive Processes TEKS 6G, 10A 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 TEKS 6G, 10A 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 TEKS 6G, 10A 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 TEKS 6G, 10A 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. Bacterial STDs can be treated, and in many cases, cured with antibiotics