The Reproductive System 16 The Reproductive System

Oogenesis and the Ovarian Cycle total eggs present at birth Egg release at puberty Menopause– no more eggs Oocytes mature, then ovulated Have 23 chromosomes Large cells Oocyte

Oocyte Figure 16.11

Hormone Production by the Ovaries Estrogens Cause secondary sex characteristics Progesterone Helps maintain pregnancy Prepare breasts for milk production

Mammary Glands Modified sweat glands Function: Adipose tissue Lactiferous duct Nipple Lobule containing alveoli

Mammography X-ray examination that detects breast cancers Recommended: every 2 years for 40-49 years > 49 = yearly Malignancy (a) Mammogram procedure (b) Film of normal breast (c) Film of breast with tumor

III. Determination of Sex/Gender Embryo: Sex Chromosomes determine development of Gonads Embryonic Testes produce Testosterone: Other male sex organs develop & brain is masculinized No or little Testosterone triggers female sex organs to develop and feminization of brain B. Puberty Hypothalamus/Pituitary Gland: in control Testosterone in Males & Estrogen in Females: a. Reproductive organs mature b. Sex drive develops c. Secondary Sex Characteristics develop d. Production of Sperm & Eggs begins

C. Human Life Cycle Sperm (23) with Egg (23) creates Zygote (46) = 1st Cell

Accomplishing Fertilization Oocyte lives 12 to 24 hr Sperm lives 24 to 48 hr Sperm must get to uterine tube For fertilization: 2 days before ovulation 3 days 24 hours after ovulation oocyte membrane does not permit second sperm to enter Fertilization = Sperm DNA combines with oocyte DNA  Zygote

Introduction to Pregnancy and Development Cleavage: Rapid cell division of embryo 4 days after ovulation, it reaches uterus 7 days after ovulation, embryo implants Embryo—fertilization to week 8 Fetus—week 9 to birth Gestation period—280 days Cleavage Embryo Fertilization 1-week conceptus 3-week embryo (3 mm) 5-week embryo (10 mm) 8-week embryo (22 mm) 12-week fetus (90 mm)

Development After Implantation Placenta: Amnion—fluid-filled sac that surrounds the embryo Umbilical cord Blood vessel-containing stalk of tissue Attaches the embryo to the placenta Umbilical cord Amnion Chorionic villi Uterine cavity Chorion Ectoderm Forming mesoderm Embryo Endoderm

Amniotic sac Umbilical cord Umbilical vein Chorionic villi Yolk sac Cut edge of chorion Figure 16.18

Functions of the Placenta Forms barrier: blood is not mixed Delivers nutrients & oxygen Removes waste Produces Estrogen & Progesterone to maintain pregnancy

Effects of Pregnancy on the Mother Enlargement of uterus Accentuated lumbar curvature Morning sickness (elevated progesterone & estrogens) Heartburn: crowding by the fetus Constipation

Effects of Pregnancy on the Mother … Kidneys: produce more urine Bladder squeezed: incontinence Blood volume increases Blood pressure and pulse increase Childbirth (Parturition) Initiation of labor Uterine contractions begin Oxytocin is released by the pituitary  stronger contractions Hypothalamus sends efferent impulses to posterior pituitary, where oxytocin is stored 4 Posterior pituitary releases oxytocin to blood; oxytocin targets mother’s uterine muscle 5 Uterus responds by contracting more vigorously 6 Baby moves deeper into mother’s birth canal 1 Afferent impulses to hypothalamus 3 Pressoreceptors in cervix of uterus excited 2 Positive feedback mechanism continues to cycle until interrupted by birth of baby

Placenta Umbilical cord Uterus Cervix Vagina Sacrum Stages of Labor Dilation Cervix becomes dilated to 10 cm The amnion ruptures (“breaking the water”) Placenta Umbilical cord Uterus Cervix Vagina Sacrum

Perineum Expulsion Infant passes through the cervix & vagina Stages of Labor … Expulsion Infant passes through the cervix & vagina head first Perineum Placental stage Delivery of the placenta Perineum

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