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Human Reproductive System Review Sexual Development • After birth, the gonads produce small amounts of sex hormones that continue to develop the reproductive organs • Neither testes nor ovaries are capable of producing active reproductive cells until puberty • Puberty = period of rapid growth and sexual maturation beginning between ages 9-15 when the hypothalamus signals the pituitary gland to produce increased levels of folliclestimulating hormone (FSH) and Male Reproductive System • The release of FSH and LH stimulates the testes to produce testosterone, a steroid that stimulates target cells all over the body producing secondary sex characteristics (facial and body hair, body growth, deeper voice) • FSH and testosterone stimulate Male Reproductive System Sperm Formation • • • • • MEIOSIS forms sperm in gametes Sperm forms in testes Scrotum keeps cooler than rest Semen is sperm plus protecting fluid Semen leaves testes through the vas deferens (sperm ducts) to the urethra before it exits. Secondary Sexual Characteristics - Male • Produced by testosterone – Deeper voice – Chest and facial hair – Lengthen bones – Increased size of testes for sperm production Female Reproductive System • The structures of the female reproductive system produce eggs as well as prepares the female’s body to nourish a developing embryo – Ovaries – produce ova (eggs) from follicles – Fallopian tubes (oviduct) – carry eggs from ovaries to Female Reproductive System Mrs. Degl Ovum Formation • MEIOSIS forms the eggs (ova) • Eggs are formed before birth • 1 egg per month is matured and released from ovaries, most of the time • Eggs travel through the fallopian tube where they may become fertilized Secondary Sexual Characteristics - Female • Induced by increased LH, FSH, estrogen, and progesterone hormone levels – Pubic hair – Widen pelvis – Enlarge mammary tissue (breasts) – Begin menstrual cycles The Menstrual Cycle Section 39-3 Fertilization • • • • Occurs in upper 1/3 of Fallopian tube Only 1 sperm can fertilize an egg Fertilized egg = zygote An average woman is pregnant (gestational period) for 9 whole months. That is 40 weeks. Babies can survive if they are born earlier, but they may have complications due to being premature. Implantation • Fertilized eggs are implanted into thick walls of uterus • Chorion membranes dig into uterus to form placenta • Zygote grows into an embryo • Embryo gets air and nutrients through the umbilical cord • Once pregnant, progesterone levels stay high in mom • Mom’s uterus grows with the baby BLASTULA TO GASTRULA BLASTOCYST GASTRULA THREE LAYERS OF CELLS ARE FORMED. THIS IS CALLED Animations: DIFFERENTIATION http://learningobjects.wesleyan.edu/gastrulation/animations.php?a ni=3D http://www.hhmi.org/biointeractive/media/human_emb_devlg.mov CELLS PINCH INWARD A.K.A. INVAGINATION 1st Trimester = 1st 12 weeks • • • • Placenta forms Heart develops first Neural tube develops All body systems appear by Week 8 – Now a Fetus Fertilization and Implantaton Section 39-4 Fallopian tube Day 2 Day 3 Day 1 Day 4 4 cells Morula Day 7 Blastocyst 2 cells Fertilization Zygote Day 0 Implantation of blastocyst Uterine wall Ovary Egg released by ovary Figure 39–20 The Placenta Section 39-4 Amniotic sac Placenta Umbilical cord Fetal portion of placenta Maternal portion of placenta Villus in chorion Amnion Uterus Amnion Umbilical cord Maternal artery Umbilical arteries Umbilical vein Maternal vein 2nd Trimester = up to 24 weeks • Most growth • Looks more like a baby • Some preemies survive at this stage 3rd Trimester = Up to 40 weeks • • • • • More growth Kicking, rolling, stretching Eyes open – Week 32 Lungs mature Rotates to head-down position, unless baby is breech Birth • Labor – Uterine contractions begin – Cervix dilates to 10 cm. • Birth – Uterus pushes baby through vaginal canal – Placenta delivered after baby – Cesarean Section (c-section) is a surgery that cuts through the uterus to deliver the baby if it cannot be born vaginally Multiple Births? • Fraternal twins = when 2 eggs are released and fertilized by 2 sperm during the same cycle – Not identical because different eggs fertilized by different sperm • Identical twins = when 1 zygote splits producing 2 embryos – Identical because contain genetic information from same egg and same sperm