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PowerPoint® Lecture Slides prepared by Betsy C. Brantley Valencia College CHAPTER 19 Development and Inheritance © 2013 Pearson Education, Inc. Chapter 19 Learning Outcomes • Section 1: An Overview of Development • 19.1 • Discuss cleavage, blastocyst formation, and implantation of the blastocyst in the uterine wall. • 19.2 • Describe gastrulation and the formation and fate of the three germ layers. • 19.3 • Identify and describe the formation, location, and functions of the extra-embryonic membranes. • 19.4 • Discuss the importance of the placenta to the fetus during prenatal development and as an endocrine organ. © 2013 Pearson Education, Inc. Chapter 19 Learning Outcomes • 19.5 • Describe organogenesis and its role in the developing fetus. • 19.6 • Describe the interplay between the maternal organ systems and the developing fetus. • 19.7 • List and discuss the events that occur during labor and delivery. • 19.8 • Explain the milk let-down reflex and describe the five postnatal life stages. • 19.9 • Explain the role of hormones in males and females at puberty. © 2013 Pearson Education, Inc. Chapter 19 Learning Outcomes • Section 2: Genetics and Inheritance • 19.10 • Relate basic principles of genetics to the inheritance of human traits. • 19.11 • CLINICAL MODULE Identify several chromosomal disorders and describe three tests performed during pregnancy used to detect abnormal fetal development. © 2013 Pearson Education, Inc. Overview of Development (Section 1) • Development • Gradual modification of anatomical structures and physiological characteristics from fertilization to maturity • Divided into prenatal (before birth) and postnatal • Prenatal development • Embryological development • Events occurring in first two months after fertilization • Study of these events is embryology • Fetal development • Begins at start of ninth week and continues until birth © 2013 Pearson Education, Inc. Prenatal development Prenatal Development Embryological development Fetal development 4 weeks 8 weeks 16 weeks © 2013 Pearson Education, Inc. Figure 19 Section 1 1 1 Gestation (Section 1) • Time spent in prenatal development • Usually divided into three trimesters (each three months long) 1. First trimester • All major organ systems first appear 2. Second trimester • Development of all organ systems 3. Third trimester • © 2013 Pearson Education, Inc. Most organ systems fully functional Gestation or Prenatal Development (Section 1) • Usually divided into three trimesters (each 3 months long) 1. First trimester • All major organ systems first appear 2. Second trimester • Development of all organ systems • Body shape and proportions change 3. Third trimester • Most organ systems fully functional • Largest gain in fetal weight © 2013 Pearson Education, Inc. Postnatal Development (Section 1) • Begins at birth and continues to maturity • Maturity is state of full development and growth • Basic understanding of prenatal and postnatal development important • Provides insights into anatomical structures • Mechanisms of development and growth similar to mechanisms for repair of injuries © 2013 Pearson Education, Inc. Day 0: Fertilization (19.1) • Fertilization is fusion of two haploid gametes • Enzymes released by multiple sperm create gap in follicular cells and single sperm contacts oocyte membrane • Sperm and egg nuclei (23 chromosomes each) fuse • Produces zygote with 46 chromosomes • Zygote then divides in process called cleavage • Group of blastomeres created by cleavage called pre-embryo • Cleavage lasts about seven days as pre-embryo travels down uterine tube into uterus © 2013 Pearson Education, Inc. Development: Days 1–5 (19.1) • First cleavage completed about 30 hours after fertilization • Day 1: Two-cell stage • Daughter cells (blastomeres) half size of zygote • Day 2: Four-cell stage • Two more daughter cells produced by second division • Day 3: Early morula • Pre-embryo now a solid ball of cells called morula • Day 4: Advanced morula • Morula reaches uterus by day 4 • Day 5 • Zona pellucida shed as morula enters uterus © 2013 Pearson Education, Inc. Cleavage and blastocyst formation Day 3: First Cleavage Day 1: Day 2: Two-Cell Stage Four-Cell Stage Early Morula Division Polar bodies Blastomeres Day 4: Advanced Morula Blastomeres Day 5: Loss of zona pellucida and transport to uterus Day 0: Fertilization Start Fertilization Ovulation © 2013 Pearson Education, Inc. Figure 19.1 Development: Days 6–7 (19.1) • Day 6: Blastocyst • Blastomeres form a hollow ball (blastocyst) around an inner cavity (blastocoele) • Rate of growth increases and blastomeres no longer all identical in size and shape • Outer layer of cells (trophoblast) will provide nutrients to embryo • Inner cell mass will form the embryo • Day 7: Implantation • Blastocyst attaches to endometrium, erodes endometrial lining, and is enclosed within endometrium by day 10 © 2013 Pearson Education, Inc. Development: Days 8–9 (19.1) • Day 8: Trophoblast development • Trophoblast cells divide rapidly • Cells closest to blastocoele form cellular trophoblast • Syncytial trophoblast • Cells near endometrial wall lose plasma membranes, creating layer of cytoplasm with multiple nuclei • Day 9: Formation of amniotic cavity • Fingerlike villi extend away from trophoblast into endometrium creating channels called lacunae that fill with maternal blood • Inner cell mass separates from trophoblast creating fluid-filled chamber called amniotic cavity © 2013 Pearson Education, Inc. Implantation Day 6: Blastocyst FUNCTIONAL ZONE OF ENDOMETRIUM Uterine glands UTERINE CAVITY Blastocyst Trophoblast (outer layer of cells) Day 7: Implantation Blastocoele Inner cell mass Day 8: Trophoblast Development Syncytial trophoblast Day 9: Formation of Amniotic Cavity Cellular trophoblast Villi Lacuna Amniotic cavity Endometrial capillary © 2013 Pearson Education, Inc. Figure 19.1 Module 19.1 Review a. Define cleavage. b. What developmental stage begins once the zygote arrives in the uterine cavity? c. Describe the blastocyst and its role in implantation. © 2013 Pearson Education, Inc. Development: Days 9–10 (19.2) • Day 9: Continued formation of amniotic cavity • Inner cell mass organized into two layers, superficial and deep • Cells from superficial layer migrate along walls of amniotic cavity • First step in formation of amnion, an extra-embryonic membrane • Day 10: Yolk sac formation • Cells from deep layer of inner cell mass migrate around outer edge of blastocoele • First step in formation of yolk sac • Yolk sac primary nutrient source for inner cell mass for next two weeks © 2013 Pearson Education, Inc. Day 12: Gastrulation (19.2) • Some cells from superficial layer leave surface and move between existing layers (superficial and deep) • Process called gastrulation • Creates three embryonic layers called germ layers 1. Ectoderm – superficial cells that didn't migrate 2. Endoderm – cells facing yolk sac 3. Mesoderm – migrating cells between endoderm and ectoderm • End result is oval, three-layered sheet called embryonic disc © 2013 Pearson Education, Inc. Gastrulation Day 9: Formation of Amniotic Cavity (continued) ENDOMETRIUM Inner cell mass Superficial layer (blue) Deep layer (orange) Amniotic cavity Blastocoele Amnion Cellular trophoblast Day 10: Yolk Sac Formation Syncytial trophoblast Cellular trophoblast Yolk sac Lacuna Day 12: Gastrulation Yolk sac Amnion Ectoderm Mesoderm Primitive streak Blastodisc Endoderm Embryonic disc © 2013 Pearson Education, Inc. Figure 19.2 © 2013 Pearson Education, Inc. Figure 19.2 Gestational Trophoblastic Neoplasia (19.2) • Trophoblast divides rapidly and repeatedly and invades tissue • Also supposed to form extra-embryonic membranes • In about 0.1 percent of pregnancies: • Trophoblast behaves like a tumor • Gestational trophoblastic neoplasia • In 20 percent of cases, cells metastasize to other tissues and can be fatal • Treated with surgical removal of mass followed by chemotherapy © 2013 Pearson Education, Inc. Module 19.2 Review a. Define gestational trophoblastic neoplasia. b. Define gastrulation and describe its importance. c. What germ layer gives rise to nearly all body systems except the nervous and respiratory systems? © 2013 Pearson Education, Inc. Four Extra-Embryonic Membranes (19.3) • Germ layers part of membrane formation 1. Yolk sac (endoderm and mesoderm) 2. Amnion (ectoderm and mesoderm) 3. Allantois (endoderm and mesoderm) 4. Chorion (mesoderm and trophoblast) • Membranes support embryological and fetal development © 2013 Pearson Education, Inc. Yolk Sac (19.3) • Begins as layer of cells around outer edges of blastocoele • Visible 10 days after fertilization • Vascular network of yolk sac site of blood cell formation • Collects and distributes nutrients absorbed from blastocoele © 2013 Pearson Education, Inc. Amnion (19.3) • Begins as superficial cells migrate around amniotic cavity • Combination of mesodermal and ectodermal cells • Amniotic fluid in amniotic cavity surrounds and cushions developing embryo or fetus © 2013 Pearson Education, Inc. Formation of yolk sac and amnion Formation of the Yolk Sac Endometrium Formation of the Amnion Syncytial trophoblast Cellular trophoblast Layer of cells that will become yolk sac Superficial cells that will become amnion Blastocoele Day 10 Syncytial trophoblast Cellular trophoblast Blastocoele Completed yolk sac Amnion (combination of mesodermal and ectodermal cells) Amniotic fluid Day 14 © 2013 Pearson Education, Inc. Figure 19.3 Allantois (19.3) • Begins as outpocketing of endoderm near base of yolk sac • Free endodermal tip grows toward wall of blastocyst, surrounded by mesodermal cells • Extends partway into umbilical stalk • Base of allantois will form urinary bladder © 2013 Pearson Education, Inc. Chorion and Placenta (19.3) • Chorion • Mesoderm associated with allantois spreads around blastocyst, separating trophoblast from blastocoele • Combination of mesoderm and trophoblast is chorion • Beginning of the placenta • Placenta • • • • Forms from fetal and maternal cells Villi of chorion invade endometrium Primary support mechanism for developing embryo Site of exchange (oxygen and nutrients for carbon dioxide and wastes) © 2013 Pearson Education, Inc. Formation of allantois and chorion Formation of the Allantois Formation of the Chorion Endometrium Allantois Chorion Amniotic cavity Yolk sac Blastocoele Embryo Uterine lumen Syncytial trophoblast Week 3 Umbilical stalk Allantois Amniotic cavity Blastocoele Embryo Uterus Uterine lumen Placenta Yolk sac Cervical (mucous) plug © 2013 Pearson Education, Inc. Week 5 Figure 19.3 Module 19.3 Review a. Name the four extra-embryonic membranes. b. Which extra-embryonic membrane later gives rise to the urinary bladder? c. From which germ layers do the extra-embryonic membranes form, and what are each membrane's functions? © 2013 Pearson Education, Inc. Placenta Blood Supply (19.4) • Umbilical arteries • Carry blood from developing fetus to placenta • Blood is deoxygenated and full of waste products • Placenta • Chorionic villi provide surface area for exchange of gases, nutrients, and wastes • Umbilical vein • Carries blood from placenta back to fetus © 2013 Pearson Education, Inc. Placental structures with chorionic villus cross section Area filled with maternal blood Trophoblast Fetal blood vessels Umbilical cord (cut) Embryonic connective tissue Yolk sac Placenta Chorionic villus, cross section LM x 280 Amnion Chorion Chorionic villi Endometrium Myometrium Area filled with maternal blood Uterine cavity Cervical (mucous) plug in cervical canal External os Cervix Vagina © 2013 Pearson Education, Inc. Maternal blood vessels Umbilical Umbilical vein arteries Amnion Trophoblast (cellular and syncytial layers) Figure 19.4 11 Placental structures with chorionic villus cross section Umbilical cord (cut) Yolk sac Placenta Amnion Chorion Chorionic villi Endometrium Myometrium Uterine cavity Cervical (mucous) plug in cervical canal External os Cervix Vagina © 2013 Pearson Education, Inc. Area filled with maternal blood Maternal blood vessels Umbilical Umbilical Amnion Trophoblast (cellular and syncytial layers) vein arteries Figure 19.4 11 Placental Hormones (19.4) • Human chorionic gonadotropin (hCG) • Presence in blood or urine provides reliable indicator of pregnancy • Maintains corpus luteum and promotes continued secretion of progesterone to maintain uterine lining • Corpus luteum persists for three to four months before declining in function • Human placental lactogen (hPL) • Helps prepare mammary glands for milk production © 2013 Pearson Education, Inc. Placental Hormones (19.4) • Relaxin 1. Increases flexibility of pubic symphysis allowing expansion of pelvis during delivery 2. Causes dilation of cervix 3. Delays onset of labor contractions until late pregnancy • Progesterone and estrogen • After first trimester, progesterone from placenta maintains endometrial lining • Estrogen production accelerates near end of third trimester, playing role in stimulating labor and delivery © 2013 Pearson Education, Inc. Placental hormones Placental Hormones Human Chorionic Gonadotropin (hCG) Human chorionic gonadotropin (hCG) appears in maternal bloodstream soon after implantation and can be tested for (in urine or blood) as an indicator of pregnancy. hCG maintains the corpus leteum and promotes continued secretion of progesterone. Human Placental Lactogen (hPL) Human placental lactogen (hPL) helps prepare the mammary glands for milk production. At the mammary glands, the conversion from inactive to active status requires the presence of placental hormones (hPL, estrogen, and progesterone) as well as several maternal hormones (GH, prolactin, and thyroid hormones). Relaxin Relaxin is a peptide hormone that is secreted by the placenta and the corpus luteum during pregnancy. Relaxin (1) increases the flexibility of the pubic symphysis, permitting the pelvis to expand during delivery; (2) causes dilation of the cervix, making it easier for the fetus to enter the vaginal canal; and (3) delays the onset of labor contractions until late in the pregnancy. Progesterone and Estrogen After the first trimester, the placenta produces sufficient amounts of progesterone to maintain the endometrial lining and continue the pregnancy. As the end of the third trimester approaches, estrogen production by the placenta accelerates. As we will see in a later module, the rising estrogen levels play a role in stimulating labor and delivery. © 2013 Pearson Education, Inc. Figure 19.4 22 Module 19.4 Review a. Name the hormones synthesized by the syncytial trophoblast. b. The presence of which hormone in the urine provides a reliable indicator of pregnancy in home pregnancy tests? c. When does the placenta become sufficiently functional to continue the pregnancy? © 2013 Pearson Education, Inc. Organ System Formation (19.5) • Process of organ formation is organogenesis • Second week of development • CNS forming • Deep groove in ectodermal band along posterior midline of embryo • Fourth week of development • Heart is beating © 2013 Pearson Education, Inc. Embryo in the second week of development Future head of embryo Thickened neural plate (will form brain) Central canal of future spinal cord Somites (mesodermal blocks that will form muscles and vertebrae) Neural folds (fuse to enclose brain ventricles and central canal of spinal cord) Cut wall of amnion © 2013 Pearson Education, Inc. Figure 19.5 11 Human development at four weeks Medulla oblongata Ear Forebrain Eye Heart Body stalk Arm bud Leg bud Tail © 2013 Pearson Education, Inc. Figure 19.5 22 Organ System Formation (19.5) • Sixth week of development • Placenta has formed • Embryo floating in amniotic cavity • Limbs grow longer and skull bones form around brain • End of first trimester • Human features better defined • Axial and appendicular muscles forming • Fetal movements will begin soon © 2013 Pearson Education, Inc. Human development at six weeks Chorionic villi Amnion Umbilical cord Placenta © 2013 Pearson Education, Inc. Figure 19.5 33 Human development at 12 weeks Amnion Umbilical cord © 2013 Pearson Education, Inc. Figure 19.5 44 Fetal Development (19.5) • After four months: • Face and palate formed • Cerebral hemispheres enlarging • Hair follicles present and hair growing • Peripheral nerves formed • First eight weeks of fetal growth most rapid • By end of second trimester, weighs about 0.64 kg © 2013 Pearson Education, Inc. Four month old fetus © 2013 Pearson Education, Inc. Figure 19.5 55 Fetal Development (19.5) • Third trimester • Organ systems become ready for normal function • Rate of growth slows a little • Largest weight gain in third trimester (about 2.6 kg) to reach full-term weight of about 3.2 kg (7 lb) © 2013 Pearson Education, Inc. Ultrasound of six month old fetus © 2013 Pearson Education, Inc. Figure 19.5 66 Module 19.5 Review a. Define organogenesis. b. Identify the main event in fetal development during the second trimester and third trimester. c. During which trimester does the fetus undergo its largest absolute weight gain? © 2013 Pearson Education, Inc. Maternal Changes with Pregnancy (19.6) • Mother has to absorb enough oxygen, nutrients, and vitamins for herself and fetus • Must also eliminate all wastes generated • Physical changes include: • Weight gain of 6–7 kg • Changes in balance since additional weight is not evenly distributed • Pushing maternal abdominal organs out of position © 2013 Pearson Education, Inc. Sectional view comparing organ positions in nonpregnant and pregnant women Diaphragm Liver Stomach Pancreas Transverse colon Small intestine Fundus of uterus Umbilical cord Placenta Uterus Urinary bladder Pubic symphysis Rectum Urethra Vagina Nonpregnant female © 2013 Pearson Education, Inc. Cervical (mucous) plug in cervical canal External os Pregnant female (full-term infant) Figure 19.6 11 Maternal Physiological Adjustments (19.6) • Increased respiratory rate and tidal volume • To deliver extra oxygen and remove excess carbon dioxide • Almost 50 percent increase in maternal blood volume • To deliver blood to placenta and to compensate for lowered oxygen levels in maternal blood • Increased hunger sensations • To meet increased requirements for nutrients, which can be up to 30 percent above normal © 2013 Pearson Education, Inc. Maternal Physiological Adjustments (19.6) • Increased maternal glomerular filtration rate (GFR) by 50 percent • To eliminate additional wastes produced • Increased frequency of urination • In response to increased urine production and weight of uterus pressing on urinary bladder • Mammary gland development • Fully developed and producing clear secretions by end of sixth month • Requires combination of hormones (hPL, prolactin, estrogen, progesterone, GH, and thyroxine) © 2013 Pearson Education, Inc. Changes in the Uterus (19.6) • Grows from 7.5 cm in length and 30–40 g in weight to 30 cm in length and 1100 g in weight • May contain up to 2 liters of fluid plus fetus and placenta for total weight of 6–7 kg • Number of uterine cells does not increase • Expansion due to hypertrophy or enlargement of existing cells, especially smooth muscle cells © 2013 Pearson Education, Inc. Physiological changes in maternal systems by end of third trimester Maternal respiratory rate goes up and tidal volume increases. Mammary glands are fully developed by the end of the sixth month of pregnancy. Maternal glomerular filtration rate increases by roughly 50 percent. Maternal blood volume increases by almost 50 percent by the end of gestation. Maternal requirements for nutrients increases up to 30 percent above normal. The uterus expands from 7.5 cm to 30 cm in length. Because the volume of urine produced increases and the weight of the uterus presses down on the urinary bladder, pregnant women need to urinate frequently. © 2013 Pearson Education, Inc. Figure 19.6 22 Pregnancy Risks (19.6) • Pregnancy is a natural phenomenon yet not without health risks • Demands on maternal systems are possibly dangerous • Pregnant women over 35 are twice as likely to die from pregnancy-related complications as from an automobile accident © 2013 Pearson Education, Inc. Module 19.6 Review a. List the major changes that occur in maternal systems during pregnancy. b. Why does a mother's blood volume increase during pregnancy? c. Based on the illustrations showing the locations of the internal organs in nonpregnant and pregnant women, explain why some women experience difficulty breathing while pregnant. © 2013 Pearson Education, Inc. False and True Labor (19.7) • Stretching of uterus causes gradual increase in spontaneous smooth muscle contraction in myometrium • Progesterone from placenta inhibits contractions in early pregnancy • False labor • Spasms in uterine muscle that are not regular or persistent • True labor • Begins with series of events that are not reversible © 2013 Pearson Education, Inc. Position of fetus at onset of true labor Placenta Umbilical cord Public Vagina symphysis Cervical canal © 2013 Pearson Education, Inc. Cervix Figure 19.7 11 Labor Initiation (19.7) • Multiple factors responsible for beginning of true labor • Placental factors include: • Rising estrogen levels increasing muscle cells' sensitivity to oxytocin • Relaxin dilating cervix • Release of maternal oxytocin stimulates smooth muscle contraction • Contraction of myometrium distorts uterus, which stimulates more oxytocin release • Positive feedback continues until delivery is complete © 2013 Pearson Education, Inc. Factors involved in initiation of labor and delivery Placental Factors Placental estrogen increases the sensitivity of the smooth muscle cells of the myometrium and makes contractions more likely. As delivery approaches, the production of estrogen accelerates. Estrogen also increases the sensitivity of smooth muscle fibers to oxytocin. Maternal Oxytocin Release Maternal oxytocin release is stimulated by high estrogen levels. The smooth muscle in a late-term uterus is 100 times more sensitive to oxytocin than the smooth muscle in a nonpregnant uterus. Relaxin produced by the placenta relaxes the pelvic articulations and dilates the ervix. Distortion of Myometrium Distortion of the myometrium increases the sensitivity of the smooth muscle layers, promoting spontaneous contractions that get stronger and more frequent as the pregnancy advances. Labor contractions move the fetus and further distort the myometrium. This distortion stimulates additional oxytocin and prostaglandin release. This positive feedback continues until delivery is completed. LABOR CONTRACTIONS OCCUR © 2013 Pearson Education, Inc. Figure 19.7 22 Stages of Labor (19.7) • Goal of labor is parturition: forcible expulsion of fetus and placenta • Divided into three stages 1. Dilation stage 2. Expulsion stage 3. Placental stage © 2013 Pearson Education, Inc. Dilation Stage (19.7) • Begins with onset of true labor • Cervix dilates • Fetus shifts toward cervical canal moved by gravity and uterine contractions • Lasts eight or more hours • Contractions at the beginning last up to 30 seconds and occur once every 10–30 minutes • Frequency and duration of contractions increase • Amnion ruptures late in stage ("water breaks") © 2013 Pearson Education, Inc. Expulsion Stage (19.7) • Begins as cervix completes dilation • Contractions reach maximum intensity • Can last up to full minute and occur two to three minutes apart • Stage continues until fetus has emerged from vagina • Usually lasts less than two hours • Arrival of newborn outside mother's body is called delivery © 2013 Pearson Education, Inc. Placental Stage (19.7) • Uterine contractions continue • Size of uterus decreases gradually • Contractions tear connections between endometrium and placenta • Placenta or afterbirth is ejected • Continued contractions after placenta ejected compresses uterine blood vessels to restrict blood loss © 2013 Pearson Education, Inc. Stages of labor Dilation Stage Expulsion Stage Placental Stage Uterus Ejection of the placenta © 2013 Pearson Education, Inc. Figure 19.7 33 Premature Labor (19.7) • When true labor begins before fetus has completed normal development • Chances of newborn surviving are directly related to body weight at delivery • Less than 400 g will not survive • Respiratory, cardiovascular, urinary systems unable to support life • Less than 600 g (25–27 weeks) will not likely survive • Premature delivery • Birth at 28–36 weeks and weight over 1 kg • With care, good chance of surviving and developing normally © 2013 Pearson Education, Inc. Module 19.7 Review a. List and describe the factors involved in initiating labor contractions. b. What chemicals are primarily responsible for initiating contractions of true labor? c. Name the three stages of labor, and describe the events that characterize each stage. © 2013 Pearson Education, Inc. Neonatal Period (19.8) • Development continues after birth in the neonatal period (first 28 days) • Infancy is first year of life • Dependent on mother for nourishment, transportation, and protection © 2013 Pearson Education, Inc. Milk Production (19.8) • By end of sixth month of pregnancy, mammary glands fully developed and secreting colostrum • Colostrum contains antibodies that help fight infection until newborn's immune system develops • Few days into nursing, mammary glands produce breast milk • Breast milk higher in fat content than colostrum • Also contains antibodies and lysozyme (enzyme with antibiotic properties) • Breast milk provided to infants through milk let-down reflex © 2013 Pearson Education, Inc. Milk Let-Down Reflex (19.8) 1. Stimulation by tactile receptors • Infant suckling 2. Neural impulse transmission to spinal cord and then to brain 3. Stimulation of hypothalamic nuclei • Neurons in paraventricular nucleus 4. Oxytocin release at posterior lobe of pituitary gland • Hypothalamic neurons release oxytocin, which enters bloodstream and circulates throughout body 5. Milk ejected • Oxytocin causes contraction of myoepithelial cells in walls of lactiferous ducts and sinuses © 2013 Pearson Education, Inc. 3 The milk let-down reflex Stimulation of Hypothalamic Nuclei Posterior lobe of the pituitary gland 4 5 Oxytocin Release Milk Ejected Start © 2013 Pearson Education, Inc. 1 Stimulation of Tactile Receptors 2 Neural Impulse Transmission Figure 19.8 1 Life Stages (19.8) • Five life stages in postnatal development 1. Neonatal period (first 28 days) 2. Infancy (first year) • Dependent on nutrition contained in milk 3. Childhood • Weaned from breast milk in early childhood • Body proportions gradually change 4. Adolescence • Begins at puberty, period of sexual maturation • Ends when growth is complete 5. Maturity © 2013 Pearson Education, Inc. Postnatal development Postnatal Development Neonatal Infancy Childhood Adolescence Maturity 5 ft 4 ft 3 ft 2 ft 5 1 ft 0 1 month © 2013 Pearson Education, Inc. 2 years Puberty (between) 9–14 years 18 years Figure 19.8 22 Postnatal Hormonal Influences (19.8) • Hormones affect tissues in specific ways • Growth during infancy and childhood affected by: • Growth hormone • Adrenal steroids • Thyroid hormones • Adolescent growth and development • Most affected by sex hormones • Maturity • Gradual changes associated with aging © 2013 Pearson Education, Inc. Module 19.8 Review a. What hormone causes the milk let-down reflex? b. Explain the difference between colostrum and breast milk. c. Name the stages of postnatal development, and describe the time frame involved for each of the stages. © 2013 Pearson Education, Inc. Hormonal Changes at Puberty (19.9) • Hypothalamus increases production of gonadotropin-releasing hormone (GnRH) • Anterior pituitary gland responds by increasing FSH and LH • In response, testicular or ovarian cells initiate: 1. Gamete production 2. Secretion of sex hormones, which stimulate secondary sex characteristics and behaviors 3. Sudden acceleration in growth rate, ending with closure of epiphyseal cartilages © 2013 Pearson Education, Inc. Responses to Testosterone in Males (19.9) • Development of hairs on face and chest • Terminal hair growth in axillae and genital area • Accelerated bone deposition and skeletal growth • Increased skeletal muscle growth and mass • Activates central nervous system centers involved in sexual drive and behavior • Increased blood volume and hematocrit • Thickening of larynx and lengthening vocal cords • Functional development of accessory reproductive glands and promotion of spermatogenesis © 2013 Pearson Education, Inc. Male responses to hormonal changes at puberty Responses to Testosterone in Males Integumentary System Testosterone stimulates the development of hairs on the face and chest, and stimulates terminal hair growth in the axillae and in the genital area. Adipose tissues respond differently to testosterone than to estrogen, and this difference produces the distinct distributions of subcutaneous body fat in males versus females. Skeletal System Testosterone accelerates bone deposition and skeletal growth. In the process, it promotes closure of the epiphyseal cartilages and thus places a limit on growth in height. Muscular System Testosterone stimulates the growth of skeletal muscle fibers, and the increased muscle mass accounts for significant sex differences in body mass, even for males and females of the same height. Nervous System A surge in testosterone secretion at puberty activates the central nervous system centers concerned with male sexual drive and sexual behaviors. Cardiovascular System Testosterone stimulates erythropoiesis, thereby increasing blood volume and the hematocrit. Respiratory System Testosterone stimulates disproportionate growth of the larynx and a thickening and lengthening of the vocal cords. These changes cause a gradual deepening of the voice in males. Reproductive System Testosterone stimulates the functional development of the accessory reproductive glands, such as the prostate gland and seminal glands, and helps promote spermatogenesis. © 2013 Pearson Education, Inc. Figure 19.9 Responses to Estrogen in Females (19.9) • Continued development of fine vellus hairs • Terminal hair growth in axillae and genital area • Promotes initial development of mammary glands • Causes more rapid epiphyseal closure • Some stimulation of skeletal muscle fibers • Activates central nervous system centers involved in sexual drive and behavior • Decreased plasma cholesterol levels • Increased risk of iron-deficiency anemia due to iron loss with menses • Thickening of myometrium and increased blood flow to endometrium • Functional development of accessory reproductive structures © 2013 Pearson Education, Inc. Female responses to hormonal changes at puberty Responses to Estrogen in Females Integumentary System Estrogen stimulates the hair follicles to continue to produce fine vellus hairs and stimulate terminal hair growth in the axillae and in the genital area. The combination of estrogen, prolactin, growth hormone, and thyroid hormones promotes the initial development of the mammary glands. Skeletal System Estrogen causes more rapid epiphyseal closure than does testosterone. In addition, the period of skeletal growth is briefer in females than in males, and so females generally do not grow as tall as males. Muscular System Estrogen stimulates the growth of skeletal muscle fibers, increasing strength and endurance, but not to the extent that testosterone does in males. Nervous System A surge in estrogen secretion at puberty activates central nervous system centers involved in female sexual drive and sexual behaviors. Cardiovascular System The iron loss associated with menses increases the risk of developing iron-deficiency anemia. Estrogen decreases plasma cholesterol levels and slows the formation of plaque within arteries. As a result, premenopausal women have a lower risk of atherosclerosis than do adult men. Reproductive System Estrogen does not cause excessive growth of the larynx and vocal cords, so females typically have higher-pitched voices than males. Reproductive System Estrogen targets the uterus, promoting a thickening of the myometrium and increasing blood flow to the endometrium. Estrogen also promotes the functional development of accessory reproductive structures in females. © 2013 Pearson Education, Inc. Figure 19.9 Module 19.9 Review a. Name the three major interacting hormonal events associated with the onset of puberty. b. Why does a male generally have a deeper voice and larger larynx than a female? c. Why are premenopausal women at lesser risk of atherosclerosis than men? © 2013 Pearson Education, Inc. Genetics (Section 2) • Inheritance • Transfer of genetically determined characteristics from generation to generation • Genetics • Study of mechanisms responsible for inheritance © 2013 Pearson Education, Inc. Genotype and Phenotype (Section 2) • Genotype • Chromosomes and component genes • Analogous to house architectural plan or blueprint • Phenotype • Anatomical and physiological characteristics displayed by your pattern of genetic expression • Analogous to physical appearance of a house © 2013 Pearson Education, Inc. Genotype versus phenotype Genotype is like a set of plans. Phenotype is the detailed structure. © 2013 Pearson Education, Inc. Figure 19 Section 2 1 1 Karyotype (Section 2) • Entire set of chromosomes is a karyotype • 23 pairs of chromosomes • One member of pair came from spermatozoon • Other member came from ovum • Two together called homologous chromosomes • 22 of the 23 pairs are autosomal chromosomes • Genes affect somatic characteristics like eye color • Last pair contains sex chromosomes • Determines male (XY) or female (XX) © 2013 Pearson Education, Inc. Human karyotype © 2013 Pearson Education, Inc. Figure 19 Section 2 2 2 Homologous Pairs (19.10) • Chromosomes in a homologous pair have same structure and carry genes affecting same trait • Genes found at same location or locus on each chromosome • Two chromosomes may carry same or different form (allele) of gene • If you have same allele, you are homozygous for trait • If different alleles, you are heterozygous for trait © 2013 Pearson Education, Inc. Homologous autosomal pair of chromosomes Homozygous (same allele of a gene) Heterozygous (different alleles for same gene) © 2013 Pearson Education, Inc. "Average" autosomal pair of chromosomes contains about 1000 pairs of alleles Figure 19.10 11 Inheritance (19.10) • Phenotype from a heterozygous genotype depends on how corresponding alleles interact • Most common form of interaction is simple inheritance • Strict dominance • Any dominant allele present is expressed in phenotype • For example, even if you have only one allele for freckles, you will show freckles • "Freckle" allele dominant over "nonfreckle" allele • Recessive allele only expressed if present on both chromosomes of homologous pair © 2013 Pearson Education, Inc. Phenotype examples © 2013 Pearson Education, Inc. Figure 19.10 22 Punnett Squares (19.10) • Dominant alleles indicated by capital letters • Recessive alleles indicated by lowercase letters • TT would be homozygous dominant • Tt would be heterozygous • tt would be homozygous recessive • Punnett squares used to predict genetic probabilities • In albinism example, if father homozygous (AA) for normal pigmentation and mother homozygous (aa) for albinism, all children will have genotype Aa and normal skin pigmentation © 2013 Pearson Education, Inc. Punnett squares Maternal a alleles a A Aa Aa A Aa Aa Paternal alleles (contributed by sperm) a Aa A Paternal alleles (contributed by sperm) a © 2013 Pearson Education, Inc. Maternal alleles a Aa 50% of the children are heterozygous and have normal pigmentation aa aa 50% of the children are homozygous recessive and have albinism Figure 19.10 33 Polygenic Inheritance (19.10) • Many phenotypic characteristics involve interactions among several genes • Polygenic inheritance • Resulting phenotype depends on nature of alleles and how those alleles interact with alleles from other genes • For example, shading of brown or black hair color © 2013 Pearson Education, Inc. Example of polygenic inheritance © 2013 Pearson Education, Inc. Figure 19.10 44 Module 19.10 Review a. Describe homozygous and heterozygous. b. Differentiate between simple inheritance and polygenic inheritance. c. The trait "curly hair" operates through strict dominance. What would be the phenotype of a person who is heterozygous for this trait? © 2013 Pearson Education, Inc. Abnormal Chromosomes or Genes (19.11) • Chromosomal abnormalities may involve thousands of genes, so are usually lethal • Variations in structure of individual genes are relatively common • More than 99 percent of human nucleotide bases are the same in all people • About 1.4 million single base differences or single nucleotide polymorphisms (SNPs) exist • Some associated with specific diseases © 2013 Pearson Education, Inc. Trisomy 21 (19.11) • Down syndrome or trisomy 21 (three copies of chromosome 21) • Most common viable chromosome abnormality • Causes mental retardation and physical malformations • Degree of mental retardation ranges from moderate to severe • Anatomical problems affecting cardiovascular system are often fatal • In adulthood, many develop Alzheimer's disease before age 40 • Direct correlation between maternal age and risk of having child with trisomy 21 • Risk increases from 1 in 2000 (before age 25) to 1 in 900 (ages 30–34) to 1 in 46 (ages 35–44) © 2013 Pearson Education, Inc. Trisomy 21 © 2013 Pearson Education, Inc. Figure 19.11 11 Klinefelter Syndrome (19.11) • Individual has sex chromosome pattern XXY • Male phenotype but reduced androgen production • Testes fail to mature (causing sterility) • Breasts slightly enlarged • Occurs in 1 in 750 male births © 2013 Pearson Education, Inc. Klinefelter syndrome © 2013 Pearson Education, Inc. Figure 19.11 22 Turner Syndrome (19.11) • Individual has only single female sex chromosome (XO) • Type of chromosomal deletion called monosomy • Phenotype is normal female • Estimated occurrence 1 in 2500 female births • Maturation changes do not occur at puberty • Ovaries nonfunctional with negligible estrogen production • Physical abnormalities include short stature, low-set ears, webbed neck © 2013 Pearson Education, Inc. Turner syndrome © 2013 Pearson Education, Inc. Figure 19.11 33 X-Linked Characteristics (19.11) • X chromosome larger than Y chromosome • Carries genes that affect somatic structures • These genes called X-linked or sex linked • No corresponding allele on Y chromosome • Many associated with identifiable diseases or deficits such as color blindness © 2013 Pearson Education, Inc. X-linked characteristics X-linked allele (allele not present on Y chromosome) Y X © 2013 Pearson Education, Inc. Figure 19.11 44 Color Blindness (19.11) • Gene for distinguishing colors carried on X chromosome • Males with dominant allele (XC) have normal color vision • Males with recessive allele (Xc) have red–green color blindness • Females can have one dominant and one recessive allele and still have normal color vision (XCXc) • Females must have two recessive alleles to have red– green color blindness (XcXc) © 2013 Pearson Education, Inc. Inheritance of an X-linked trait A woman—who has two X chromosomes— can be either homozygous dominant (XCXC) or heterozygous (XCXc) and still have normal color vision. She will be unable to distinguish reds from greens only if she carries two recessive alleles, XcXc. XC A man has only one X chromosome, so whichever allele that chromosome carries determines whether he has normal color vision or is red–green color blind. Y © 2013 Pearson Education, Inc. XC Xc X C XC XC Xc Normal female Normal female (carrier) XC Y Xc Y Normal male Color-blind male Figure 19.11 55 © 2013 Pearson Education, Inc. Figure 19.11 66 Module 19.11 Review a. Define single nucleotide polymorphism. b. Name the disorder characterized by each of the following chromosome patterns: (1) XO and (2) XXY. c. Why are X-linked traits expressed more frequently in males than females? © 2013 Pearson Education, Inc.