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  • 1. © 2012 Pearson Education, Inc. PowerPoint® Lecture Presentations prepared by Jason LaPres Lone Star College—North Harris 29 Development and Inheritance
  • 2. © 2012 Pearson Education, Inc. An Introduction to Development and Inheritance • Learning Outcomes • 29-1 Explain the relationship between differentiation and development, and specify the various stages of development. • 29-2 Describe the process of fertilization, and explain how developmental processes are regulated. • 29-3 List the three stages of prenatal development, and describe the major events of each.
  • 3. © 2012 Pearson Education, Inc. An Introduction to Development and Inheritance • Learning Outcomes • 29-4 Explain how the three germ layers participate in the formation of extraembryonic membranes, and discuss the importance of the placenta as an endocrine organ. • 29-5 Describe the interplay between the maternal organ systems and the developing fetus, and discuss the structural and functional changes in the uterus during gestation.
  • 4. © 2012 Pearson Education, Inc. An Introduction to Development and Inheritance • Learning Outcomes • 29-6 List and discuss the events that occur during labor and delivery. • 29-7 Identify the features and physiological changes of the postnatal stages of life. • 29-8 Relate basic principles of genetics to the inheritance of human traits.
  • 5. © 2012 Pearson Education, Inc. An Introduction to Development and Inheritance • Development • Gradual modification of anatomical structures and physiological characteristics from fertilization to maturity • Inheritance • Transfer of genetic material from generation to generation
  • 6. © 2012 Pearson Education, Inc. 29-1 Development • Differentiation • Creation of different types of cells required in development • Occurs through selective changes in genetic activity • As development proceeds, some genes are turned off, others are turned on • Fertilization • Also called conception • When development begins
  • 7. © 2012 Pearson Education, Inc. 29-1 Development • Embryological Development • Occurs during first two months after fertilization • Study of these events is called embryology • Fetal Development • Begins at start of ninth week • Continues until birth
  • 8. © 2012 Pearson Education, Inc. 29-1 Development • Prenatal Development • Embryological and fetal development stages • Postnatal Development • Commences at birth • Continues to maturity, the state of full development or completed growth
  • 9. © 2012 Pearson Education, Inc. 29-1 Development • Inheritance • Transfer of genetically determined characteristics from generation to generation • Genetics • Study of mechanisms responsible for inheritance
  • 10. © 2012 Pearson Education, Inc. 29-2 Fertilization • Fertilization • Fusion of two haploid gametes, each containing 23 chromosomes • Produces zygote containing 46 chromosomes • Spermatozoon • Delivers paternal chromosomes to fertilization site • Travels relatively large distance • Is small, efficient, and highly streamlined
  • 11. © 2012 Pearson Education, Inc. 29-2 Fertilization • Gamete • Provides: • Cellular organelles • Inclusions • Nourishment • Genetic programming necessary to support development of embryo for a week
  • 12. © 2012 Pearson Education, Inc. 29-2 Fertilization • Fertilization • Occurs in uterine tube within a day after ovulation • Secondary oocyte travels a few centimeters • Spermatozoa must cover distance between vagina and ampulla • Capacitation • Must occur before spermatozoa can fertilize secondary oocyte • Contact with secretions of seminal glands • Exposure to conditions in female reproductive tract
  • 13. © 2012 Pearson Education, Inc. 29-2 Fertilization • Hyaluronidase • Enzyme breaks down bonds between adjacent follicle cells • Allows spermatozoon to reach oocyte • Acrosin • Is a proteolytic enzyme • Is required to reach oocyte
  • 14. © 2012 Pearson Education, Inc. 29-2 Fertilization • Acrosomes • Release hyaluronidase and acrosin • Penetrate corona radiata, zona pellucida, toward oocyte surface • Oocyte Activation • Contact and fusion of cell membranes of sperm and oocyte • Follows fertilization • Oocyte completes meiosis II, becomes mature ovum
  • 15. © 2012 Pearson Education, Inc. 29-2 Fertilization • Polyspermy • Fertilization by more than one sperm • Prevented by cortical reaction • Cortical Reaction • Releases enzymes that: • Inactivate sperm receptors • Harden zona pellucida
  • 16. © 2012 Pearson Education, Inc. 29-2 Fertilization • Female Pronucleus • Nuclear material remaining in ovum after oocyte activation • Male Pronucleus • Swollen nucleus of spermatozoon • Migrates to center of cell
  • 17. © 2012 Pearson Education, Inc. 29-2 Fertilization • Amphimixis • Fusion of female pronucleus and male pronucleus • Moment of conception • Cell becomes a zygote with 46 chromosomes • Fertilization is complete
  • 18. © 2012 Pearson Education, Inc. 29-2 Fertilization • Cleavage • Series of cell divisions • Produces daughter cells • Differentiation • Involves changes in genetic activity of some cells but not others
  • 19. © 2012 Pearson Education, Inc. Figure 29-1a Fertilization A secondary oocyte and numerous sperm at the time of fertilization. Notice the difference in size between the gametes.
  • 20. © 2012 Pearson Education, Inc. Figure 29-1b Fertilization Ovulation releases a secondary oocyte and the first polar body; both are surrounded by the corona radiata. The oocyte is suspended in metaphase of meiosis II. Corona radiata First polar body Zona pellucida Oocyte at Ovulation
  • 21. © 2012 Pearson Education, Inc. Figure 29-1b Fertilization Acrosomal enzymes from multiple sperm create gaps in the corona radiata. A single sperm then makes contact with the oocyte membrane, and membrane fusion occurs, triggering oocyte activation and completion of meiosis. Fertilizing spermatozoon Second polar body Fertilization and Oocyte Activation
  • 22. © 2012 Pearson Education, Inc. Figure 29-1b Fertilization Pronucleus Formation Begins The sperm is absorbed into the cytoplasm, and the female pronucleus develops. Nucleus of fertilizing spermatozoon Female pronucleus
  • 23. © 2012 Pearson Education, Inc. Figure 29-1b Fertilization Spindle Formation and Cleavage Preparation The male pronucleus develops, and spindle fibers appear in preparation for the first cleavage division. Female pronucleus Male pronucleus
  • 24. © 2012 Pearson Education, Inc. Figure 29-1b Fertilization Amphimixis Occurs and Cleavage Begins Metaphase of first cleavage division
  • 25. © 2012 Pearson Education, Inc. Figure 29-1b Fertilization The first cleavage division nears completion roughly 30 hours after fertilization. Cleavage Begins Blastomeres
  • 26. © 2012 Pearson Education, Inc. 29-3 Gestation • Induction • Cells release chemical substances that affect differentiation of other embryonic cells • Can control highly complex processes • Gestation • Time spent in prenatal development • Consists of three integrated trimesters, each three months long
  • 27. © 2012 Pearson Education, Inc. 29-3 Gestation 1. First Trimester • Period of embryological and early fetal development • Rudiments of all major organ systems appear 2. Second Trimester • Development of organs and organ systems • Body shape and proportions change 3. Third Trimester • Rapid fetal growth and deposition of adipose tissue • Most major organ systems are fully functional
  • 28. © 2012 Pearson Education, Inc. 29-4 The First Trimester • First Trimester • Includes four major stages 1. Cleavage 2. Implantation 3. Placentation 4. Embryogenesis
  • 29. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Cleavage • Sequence of cell divisions begins immediately after fertilization • Zygote becomes a pre-embryo, which develops into multicellular blastocyst • Ends when blastocyst contacts uterine wall • Implantation • Begins with attachment of blastocyst to endometrium of uterus • Sets stage for formation of vital embryonic structures
  • 30. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Placentation • Occurs as blood vessels form around periphery of blastocyst and placenta develops • Embryogenesis • Formation of viable embryo • Establishes foundations for all major organ systems
  • 31. © 2012 Pearson Education, Inc. 29-4 The First Trimester • The First Trimester • Most dangerous period in prenatal life • 40% of conceptions produce embryos that survive past first trimester
  • 32. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Cleavage and Blastocyst Formation • Blastomeres • Identical cells produced by cleavage divisions • Morula • Stage after three days of cleavage • Pre-embryo is solid ball of cells resembling mulberry • Reaches uterus on day 4
  • 33. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Cleavage and Blastocyst Formation • Blastocyst • Formed by blastomeres • Hollow ball with an inner cavity • Known as blastocoele
  • 34. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Cleavage and Blastocyst Formation • Trophoblast • Outer layer of cells separate outside world from blastocoele • Cells responsible for providing nutrients to developing embryo
  • 35. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Cleavage and Blastocyst Formation • Inner cell mass • Clustered at end of blastocyst • Exposed to blastocoele • Insulated from contact with outside environment by trophoblast • Will later form embryo
  • 36. © 2012 Pearson Education, Inc. Figure 29-2 Cleavage and Blastocyst Formation Polar bodies 2-cell stage DAY 1 DAY 2 4-cell stage Blastomeres DAY 0: First cleavage division Fertilization
  • 37. © 2012 Pearson Education, Inc. Figure 29-2 Cleavage and Blastocyst Formation Early morula DAY 3 DAY 4 DAY 6 Advanced morula Hatching Inner cell mass Blastocoele Trophoblast Blastocyst Days 7–10: Implantation in uterine wall (See Figure 29–3)
  • 38. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Implantation • Occurs seven days after fertilization • Blastocyst adheres to uterine lining • Trophoblast cells divide rapidly, creating several layers
  • 39. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Implantation • Cellular trophoblast • Cells closest to interior of blastocyst • Syncytial trophoblast • Outer layer • Erodes path through uterine epithelium by secreting hyaluronidase
  • 40. © 2012 Pearson Education, Inc. Figure 29-3 Stages in Implantation DAY 6 FUNCTIONAL ZONE OF ENDOMETRIUM DAY 7 UTERINE CAVITY Uterine glands Blastocyst Trophoblast Blastocoele Inner cell mass
  • 41. © 2012 Pearson Education, Inc. Figure 29-3 Stages in Implantation DAY 8 Syncytial trophoblast Cellular trophoblast Amniotic cavity Lacuna Developing villi DAY 9
  • 42. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Ectopic Pregnancy • Implantation occurs outside uterus • Does not produce viable embryo • Can be life threatening • Lacunae • Trophoblastic channels carrying maternal blood
  • 43. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Formation of the Amniotic Cavity • Villi extend away from trophoblast into endometrium • Increase in size and complexity until day 21 • Amniotic Cavity • A fluid-filled chamber • Inner cell mass is organized into an oval sheet two layers thick • Superficial layer faces amniotic cavity • Deeper layer is exposed to fluid contents of blastocoele
  • 44. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Gastrulation and Germ Layer Formation • Formation of third layer of cells • Cells in specific areas of surface move toward central line • Known as primitive streak
  • 45. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Primitive Streak • Migrating cells leave surface and move between two layers • Creates three distinct embryonic layers, or germ layers 1. Ectoderm: consists of the superficial cells that did not migrate into interior of inner cell mass 2. Endoderm: consists of cells that face blastocoele 3. Mesoderm: consists of poorly organized layer of migrating cells between ectoderm and endoderm
  • 46. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Ectodermal Contributions • Integumentary system: • Epidermis, hair follicles and hairs, nails, and glands communicating with the skin (sweat glands, mammary glands, and sebaceous glands) • Skeletal system: • Pharyngeal cartilages and their derivatives in adults (portion of sphenoid, the auditory ossicles, the styloid processes of the temporal bones, the cornu and superior rim of the hyoid bone)* • Nervous system: • All neural tissue, including brain and spinal cord
  • 47. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Ectodermal Contributions • Endocrine system: • Pituitary gland and adrenal medullae • Respiratory system: • Mucous epithelium of nasal passageways • Digestive system: • Mucous epithelium of mouth and anus, salivary glands
  • 48. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Mesodermal Contributions • Integumentary system: • Dermis and hypodermis • Skeletal system: • All components except some pharyngeal derivatives • Muscular system: • All components
  • 49. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Mesodermal Contributions • Endocrine system: • Adrenal cortex, endocrine tissues of heart, kidneys, and gonads • Cardiovascular system: • All components
  • 50. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Mesodermal Contributions • Lymphatic system: • All components • Urinary system: • The kidneys, including the nephrons and the initial portions of the collecting system • Reproductive system: • The gonads and the adjacent portions of the duct systems • Miscellaneous: • The lining of the body cavities (pleural, pericardial, and peritoneal) and the connective tissues that support all organ systems
  • 51. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Endodermal Contributions • Endocrine system: • Thymus, thyroid gland, and pancreas • Respiratory system: • Respiratory epithelium (except nasal passageways) and associated mucous glands • Digestive system: • Mucous epithelium (except mouth and anus), exocrine glands (except salivary glands), liver, and pancreas
  • 52. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Endodermal Contributions • Urinary system: • Urinary bladder and distal portions of the duct system • Reproductive system: • Distal portions of the duct system, stem cells that produce gametes
  • 53. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Embryonic Disc • Oval, three-layered sheet • Produced by gastrulation • Will form body of embryo • Rest of blastocyst will be involved in forming extraembryonic membranes
  • 54. © 2012 Pearson Education, Inc. Figure 29-4 The Inner Cell Mass and Gastrulation Superficial layer Deep layer Day 10: Yolk Sac Formation Lacunae Blastocoele Yolk sac Amniotic cavity Cellular trophoblast Syncytial trophoblast
  • 55. © 2012 Pearson Education, Inc. Figure 29-4 The Inner Cell Mass and Gastrulation Day 12: Gastrulation Amnion Ectoderm Primitive streak Blastodisc Yolk sac Mesoderm Endoderm Embryonic disc
  • 56. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Formation of the Extraembryonic Membranes • Support embryological and fetal development • Yolk sac • Amnion • Allantois • Chorion
  • 57. © 2012 Pearson Education, Inc. 29-4 The First Trimester • The Yolk Sac • Begins as layer of cells spread out around outer edges of blastocoele to form complete pouch • Important site of blood cell formation
  • 58. © 2012 Pearson Education, Inc. 29-4 The First Trimester • The Amnion • Combination of mesoderm and ectoderm • Ectodermal layer enlarges and cells spread over inner surface of amniotic cavity • Mesodermal cells create outer layer • Continues to enlarge through development • Amniotic fluid • Surrounds and cushions developing embryo or fetus
  • 59. © 2012 Pearson Education, Inc. 29-4 The First Trimester • The Allantois • Sac of endoderm and mesoderm • Base later gives rise to urinary bladder • The Chorion • Combination of mesoderm and trophoblast • Blood vessels develop within mesoderm • Rapid-transit system for nutrients that links embryo with trophoblast • First step in creation of functional placenta
  • 60. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Chorionic Villi • In contact with maternal tissues • Create intricate network within endometrium carrying maternal blood
  • 61. © 2012 Pearson Education, Inc. Figure 29-5 Extraembryonic Membranes and Placenta Formation Migration of mesoderm around the inner surface of the trophoblast creates the chorion. Mesodermal migration around the outside of the amniotic cavity, between the ectodermal cells and the trophoblast, forms the amnion. Mesodermal migration around the endodermal pouch creates the yolk sac. Week 2 Amnion Syncytial trophoblast Cellular trophoblast Mesoderm Yolk sac Blastocoele Chorion
  • 62. © 2012 Pearson Education, Inc. Figure 29-5 Extraembryonic Membranes and Placenta Formation The embryonic disc bulges into the amniotic cavity at the head fold. The allantois, an endodermal extension surrounded by mesoderm, extends toward the trophoblast. Week 3 Amniotic cavity (containing amniotic fluid) Allantois Head fold of embryo Syncytial trophoblast Chorion Yolk sac Chorionic villi of placenta
  • 63. © 2012 Pearson Education, Inc. Figure 29-5 Extraembryonic Membranes and Placenta Formation Embryonic head fold Embryonic gut Yolk sac Yolk stalk Body stalk Tail fold The embryo now has a head fold and a tail fold. Constriction of the connections between the embryo and the surrounding trophoblast narrows the yolk stalk and body stalk. Week 4
  • 64. © 2012 Pearson Education, Inc. Figure 29-5 Extraembryonic Membranes and Placenta Formation Week 5 The developing embryo and extraembryonic membranes bulge into the uterine cavity. The trophoblast pushing out into the uterine lumen remains covered by endometrium but no longer participates in nutrient absorption and embryo support. The embryo moves away from the placenta, and the body stalk and yolk stalk fuse to form an umbilical stalk. Uterus Myometrium Chorionic villi of placenta Umbilical stalk Placenta Yolk sac Decidua capsularis Decidua parietalis Uterine lumen Decidua basalis
  • 65. © 2012 Pearson Education, Inc. Figure 29-5 Extraembryonic Membranes and Placenta Formation Decidua capsularis Week 10 The amnion has expanded greatly, filling the uterine cavity. The fetus is connected to the placenta by an elongated umbilical cord that contains a portion of the allantois, blood vessels, and the remnants of the yolk stalk. Chorion Amnion Amniotic cavity Placenta Umbilical cord Decidua parietalis Decidua basalis
  • 66. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Placentation • Body stalk • Connection between embryo and chorion • Contains distal portions of allantois and blood vessels that carry blood to and from placenta • Yolk stalk • Narrow connection between endoderm of embryo and yolk sac
  • 67. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Decidua Capsularis • Thin portion of endometrium • No longer participates in nutrient exchange and chorionic villi in region disappear • Decidua Basalis • Disc-shaped area in deepest portion of endometrium • Where placental functions are concentrated • Decidua Parietalis • Rest of the uterine endometrium • No contact with chorion
  • 68. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Umbilical Cord • Connects fetus and placenta • Contains allantois, placental blood vessels, and yolk stalk • Placental Circulation • Through paired umbilical arteries • Returns in single umbilical vein
  • 69. © 2012 Pearson Education, Inc. Figure 29-6a A Three-Dimensional View of Placental Structure Chorion Amnion Decidua capsularis Umbilical cord (cut) Placenta Yolk sac Decidua basalis A view of the uterus after the fetus has been removed and the umbilical cord cut.
  • 70. © 2012 Pearson Education, Inc. Figure 29-6a A Three-Dimensional View of Placental Structure A view of the uterus after the fetus has been removed and the umbilical cord cut. Cervix Vagina External os Cervical (mucous) plug in cervical canal Uterine cavity Decidua parietalis Myometrium
  • 71. © 2012 Pearson Education, Inc. Figure 29-6a A Three-Dimensional View of Placental Structure Chorionic villi Umbilical arteries Umbilical vein Area filled with maternal blood Arrows in the enlarged view indicate the direction of blood flow. Maternal blood vessels Trophoblast (cellular and syncytial layers) Amnion
  • 72. © 2012 Pearson Education, Inc. Figure 29-6b A Three-Dimensional View of Placental Structure Fetal blood vessels Syncytial trophoblast Embryonic connective tissue Area filled with maternal blood A cross section through a chorionic villus, showing the syncytial trophoblast exposed to the maternal blood space. LM × 280Chorionic villus
  • 73. © 2012 Pearson Education, Inc. 29-4 The First Trimester • The Endocrine Placenta • Synthesized by syncytial trophoblast, released into maternal bloodstream • Human chorionic gonadotropin (hCG) • Human placental lactogen (hPL) • Placental prolactin • Relaxin • Progesterone • Estrogens
  • 74. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Human Chorionic Gonadotropin (hCG) • Appears in maternal bloodstream soon after implantation • Provides reliable indication of pregnancy • Pregnancy ends if absent
  • 75. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Human Placental Lactogen (hPL) • Human chorionic somatomammotropin (hCS) • Prepares mammary glands for milk production • Synergistic with growth hormone at other tissues • Ensures adequate glucose and protein is available for the fetus
  • 76. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Placental Prolactin • Helps convert mammary glands to active status • Relaxin • A peptide hormone secreted by placenta and corpus luteum during pregnancy • Increases flexibility of pubic symphysis, permitting pelvis to expand during delivery • Causes dilation of cervix • Suppresses release of oxytocin by hypothalamus and delays labor contractions
  • 77. © 2012 Pearson Education, Inc. 29-4 The First Trimester • Embryogenesis • Body of embryo begins to separate from embryonic disc • Body of embryo and internal organs start to form • Folding, differential growth of embryonic disc produces bulge that projects into amniotic cavity • Projections are head fold and tail fold • Organogenesis • Process of organ formation
  • 78. © 2012 Pearson Education, Inc. Figure 29-7a The First 12 Weeks of Development Future head of embryo Thickened neural plate (will form brain) Axis of future spinal cord Somites Neural folds Cut wall of amniotic cavity Future tail of embryo Week 2. An SEM of the superior surface of a monkey embryo at 2 weeks of development. A human embryo at this stage would look essentially the same.
  • 79. © 2012 Pearson Education, Inc. Figure 29-7b The First 12 Weeks of Development Tail Body stalk Heart Eye Forebrain Ear Medulla oblongata Week 4. Fiberoptic view of human development at week 4. Leg bud Arm bud Somites Pharyngeal arches
  • 80. © 2012 Pearson Education, Inc. Figure 29-7c The First 12 Weeks of Development Umbilical cord Amnion Week 8. Fiberoptic view of human development at week 8. Placenta Chorionic villi
  • 81. © 2012 Pearson Education, Inc. Figure 29-7d The First 12 Weeks of Development Week 12. Fiberoptic view of human development at week 12. Umbilical cord Amnion
  • 82. © 2012 Pearson Education, Inc. 29-5 The Second and Third Trimesters • Second Trimester • Fetus grows faster than surrounding placenta • Third Trimester • Most of the organ systems become ready • Growth rate starts to slow • Largest weight gain • Fetus and enlarged uterus displace many of mother’s abdominal organs
  • 83. © 2012 Pearson Education, Inc. Table 29-2 An Overview of Prenatal Development
  • 84. © 2012 Pearson Education, Inc. Table 29-2 An Overview of Prenatal Development
  • 85. © 2012 Pearson Education, Inc. Table 29-2 An Overview of Prenatal Development
  • 86. © 2012 Pearson Education, Inc. Table 29-2 An Overview of Prenatal Development
  • 87. © 2012 Pearson Education, Inc. Figure 29-8a The Second and Third Trimesters A four-month-old fetus, seen through a fiberoptic endoscope
  • 88. © 2012 Pearson Education, Inc. Figure 29-8b The Second and Third Trimesters Head of a six-month-old fetus, revealed through ultrasound
  • 89. © 2012 Pearson Education, Inc. Figure 29-9a Growth of the Uterus and Fetus Placenta Umbilical cord Fetus at 16 weeks Uterus Amniotic fluid Cervix Vagina Pregnancy at 16 weeks, showing the positions of the uterus, fetus, and placenta.
  • 90. © 2012 Pearson Education, Inc. Figure 29-9b Growth of the Uterus and Fetus After dropping, in preparation to delivery Pregnancy at three months to nine months (full term), showing the superior-most position of the uterus within the abdomen. 9 months 8 months 7 months 6 months 5 months 4 months 3 months
  • 91. © 2012 Pearson Education, Inc. Figure 29-9c Growth of the Uterus and Fetus Stomach Transverse colon Liver Fundus of uterus Small intestine Pancreas Aorta Common iliac vein Cervical (mucus) plug in cervical canal External os Rectum Urethra Vagina Pubic symphysis Urinary bladder Placenta Umbilical cord Pregnancy at full term. Note the positions of the uterus and full-term fetus within the abdomen, and the displacement of abdominal organs.
  • 92. © 2012 Pearson Education, Inc. Figure 29-9d Growth of the Uterus and Fetus A sectional view through the abdominopelvic cavity of a woman who is not pregnant.
  • 93. © 2012 Pearson Education, Inc. 29-5 The Second and Third Trimesters • Pregnancy and Maternal Systems • Developing fetus is totally dependent on maternal organ systems for nourishment, respiration, and waste removal • Maternal adaptations include increases in: • Respiratory rate and tidal volume • Blood volume • Nutrient and vitamin intake • Glomerular filtration rate • Size of uterus and mammary glands
  • 94. © 2012 Pearson Education, Inc. 29-5 The Second and Third Trimesters • Progesterone • Released by placenta • Has inhibitory effect on uterine smooth muscle • Prevents extensive, powerful contractions • Opposition to Progesterone • Three major factors 1. Rising estrogen levels 2. Rising oxytocin levels 3. Prostaglandin production
  • 95. © 2012 Pearson Education, Inc. 29-5 The Second and Third Trimesters • Structural and Functional Changes in the Uterus • False labor • Occasional spasms in uterine musculature • Contractions not regular or persistent • True labor • Results from biochemical and mechanical factors • Continues due to positive feedback • Labor contractions • Begin in myometrium
  • 96. © 2012 Pearson Education, Inc. Figure 29-10 Factors Involved in the Initiation of Labor and Delivery Placental estrogens increase the sensitivity of the smooth muscle cells of the myometrium and make contractions more likely. As delivery approaches, the production of estrogens accelerates. Estrogens also increase the sensitivity of smooth muscle fibers to oxytocin. Placental Factors Fetal Factors Relaxin produced by the placenta relaxes the pelvic articulations and dilates the cervix. Growth and the increase in fetal weight stretches and distorts the myometrium. Fetal pituitary releases oxytocin in response to estrogens. 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. Distortion of Myometrium Prostaglandin Production Estrogens and oxytocin stimulate the production of prostaglandins in the endometrium. These prostaglandins further stimulate smooth muscle contractions. Maternal Oxytocin Release Maternal oxytocin release is stimulated by high estrogen levels and by distortion of the cervix. Increased Excitability of the Myometrium Oxytocin and prostaglandins both stimulate the myometrium. In addition, the sensitivity of the uterus to oxytocin increases dramatically; the smooth muscle in a late-term uterus is 100 times more sensitive to oxytocin than the smooth muscle in a nonpregnant uterus. LABOR CONTRACTIONS OCCUR 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.
  • 97. © 2012 Pearson Education, Inc. 29-6 Labor • Parturition • Is forcible expulsion of fetus • Contractions • Begin near top of uterus, sweep in wave toward cervix • Strong, occur at regular intervals, increase in force and frequency • Change position of fetus, move it toward cervical canal
  • 98. © 2012 Pearson Education, Inc. 29-6 Labor • Stages of Labor 1. Dilation stage 2. Expulsion stage 3. Placental stage
  • 99. © 2012 Pearson Education, Inc. 29-6 Labor • Dilation Stage • Begins with onset of true labor • Cervix dilates • Fetus begins to shift toward cervical canal • Highly variable in length, but typically lasts over eight hours • Frequency of contractions steadily increases • Amniochorionic membrane ruptures (water breaks)
  • 100. © 2012 Pearson Education, Inc. Figure 29-11 The Stages of Labor Fully developed fetus before labor begins Placenta Umbilical cord Sacral promontory Cervical canal Cervix Vagina Pubic symphysis
  • 101. © 2012 Pearson Education, Inc. Figure 29-11 The Stages of Labor The Dilation Stage
  • 102. © 2012 Pearson Education, Inc. 29-6 Labor • Expulsion Stage • Begins as cervix completes dilation • Contractions reach maximum intensity • Continues until fetus has emerged from vagina • Typically less than two hours • Delivery • Arrival of newborn infant into outside world
  • 103. © 2012 Pearson Education, Inc. 29-6 Labor • Episiotomy • Incision through perineal musculature • Needed if vaginal canal is too small to pass fetus • Repaired with sutures after delivery
  • 104. © 2012 Pearson Education, Inc. 29-6 Labor • Cesarean Section (C-section) • Removal of infant by incision made through abdominal wall • Opens uterus just enough to pass infant’s head • Needed if complications arise during dilation or expulsion stages
  • 105. © 2012 Pearson Education, Inc. Figure 29-11 The Stages of Labor The Expulsion Stage
  • 106. © 2012 Pearson Education, Inc. 29-6 Labor • Placental Stage • Muscle tension builds in walls of partially empty uterus • Tears connections between endometrium and placenta • Ends within an hour of delivery with ejection of placenta, or afterbirth • Accompanied by a loss of blood
  • 107. © 2012 Pearson Education, Inc. Figure 29-11 The Stages of Labor The Placental Stage Uterus Ejection of the placenta
  • 108. © 2012 Pearson Education, Inc. 29-6 Labor • Premature Labor • Occurs when true labor begins before fetus has completed normal development • Newborn’s chances of surviving are directly related to body weight at delivery
  • 109. © 2012 Pearson Education, Inc. 29-6 Labor • Immature Delivery • Refers to fetuses born at 25–27 weeks of gestation • Most die despite intensive neonatal care • Survivors have high risk of developmental abnormalities • Premature Delivery • Refers to birth at 28–36 weeks • Newborns have a good chance of surviving and developing normally
  • 110. © 2012 Pearson Education, Inc. 29-6 Labor • Difficult Deliveries • Forceps delivery • Needed when fetus faces mother’s pubis instead of sacrum • Risks to infant and mother are reduced if forceps are used • Forceps resemble large, curved salad tongs • Used to grasp head of fetus
  • 111. © 2012 Pearson Education, Inc. 29-6 Labor • Difficult Deliveries • Breech birth • Legs or buttocks of fetus enter vaginal canal first instead of head • Umbilical cord can become constricted, cutting off placental blood flow • Cervix may not dilate enough to pass head • Prolongs delivery • Subjects fetus to severe distress and potential injury
  • 112. © 2012 Pearson Education, Inc. 29-6 Labor • Multiple Births • Dizygotic twins • Also called “fraternal” twins • Develop when two separate oocytes were ovulated and subsequently fertilized • Genetic makeup not identical • 70% of twins
  • 113. © 2012 Pearson Education, Inc. 29-6 Labor • Multiple Births • Monozygotic twins • Also called “identical” twins • Result either from: • Separation of blastomeres early in cleavage • Splitting of inner cell mass before gastrulation • Genetic makeup is identical because both formed from same pair of gametes
  • 114. © 2012 Pearson Education, Inc. 29-6 Labor • Multiple Births • Conjoined twins • Siamese twins • Genetically identical twins • Occurs when splitting of blastomeres or of embryonic disc is not completed
  • 115. © 2012 Pearson Education, Inc. 29-6 Labor • Rates of Multiple Births • Twins in 1 of every 89 births • Triplets in 1 of every 892 (7921) births • Quadruplets in 1 of every 893 (704,969) births
  • 116. © 2012 Pearson Education, Inc. 29-7 Postnatal Life • Five Life Stages 1. Neonatal period 2. Infancy 3. Childhood 4. Adolescence 5. Maturity
  • 117. © 2012 Pearson Education, Inc. 29-7 Postnatal Life • Duration of Life Stages • Neonatal Period: extends from birth to 1 month • Infancy: 1 month to 2 years of age • Childhood: 2 years until adolescence • Adolescence: period of sexual and physical maturation • Senescence: process of aging that begins at end of development (maturity)
  • 118. © 2012 Pearson Education, Inc. 29-7 Postnatal Life • The Neonatal Period, Infancy, and Childhood • Two major events occur 1. Organ systems become fully operational 2. Individual grows rapidly and body proportions change significantly • Pediatrics • Medical specialty focusing on postnatal development from infancy to adolescence
  • 119. © 2012 Pearson Education, Inc. 29-7 Postnatal Life • The Neonatal Period • Transition from fetus to neonate • Neonate • Newborn • Systems begin functioning independently • Respiratory • Circulatory • Digestive • Urinary
  • 120. © 2012 Pearson Education, Inc. 29-7 Postnatal Life • Lactation and the Mammary Glands • Colostrum • Secretion from mammary glands • Ingested by infant during first two to three days • Contains more proteins and less fat than breast milk • Many proteins are antibodies that help ward off infections until immune system is functional • Mucins present inhibit replication of rotaviruses • As production drops, mammary glands convert to milk production
  • 121. © 2012 Pearson Education, Inc. 29-7 Postnatal Life • Breast Milk • Consists of water, proteins, amino acids, lipids, sugars, and salts • Also contains large quantities of lysozymes—enzymes with antibiotic properties • Milk let-down reflex • Mammary gland secretion triggered when infant sucks on nipple • Continues to function until weaning, typically one to two years
  • 122. © 2012 Pearson Education, Inc. Figure 29-12 The Milk Let-Down Reflex Milk Ejected Stimulation of Tactile Receptors Start Neural Impulse Transmission Oxytocin Release Posterior lobe of the pituitary gland Stimulation of Hypothalamic Nuclei
  • 123. © 2012 Pearson Education, Inc. 29-7 Postnatal Life • Infancy and Childhood • Growth occurs under direction of circulating hormones • Growth hormone • Adrenal steroids • Thyroid hormones • Growth does not occur uniformly • Body proportions gradually change
  • 124. © 2012 Pearson Education, Inc. Figure 29-13 Growth and Changes in Body Form and Proportion Prenatal Development Embryological Development Fetal Development 16 weeks 8 weeks 4 weeks
  • 125. © 2012 Pearson Education, Inc. Figure 29-13 Growth and Changes in Body Form and Proportion Postnatal Development Neonatal Infancy Childhood Adolescence Maturity 1 month 2 years 18 yearsPuberty (between 9–14 years)
  • 126. © 2012 Pearson Education, Inc. 29-7 Postnatal Life • Adolescence and Maturity • Puberty is a period of sexual maturation and marks the beginning of adolescence • Generally starts at age 12 in boys, age 11 in girls • Three major hormonal events interact 1. Hypothalamus increases production of GnRH 2. Circulating levels of FSH and LH rise rapidly 3. Ovarian or testicular cells become more sensitive to FSH and LH • Hormonal changes produce sex-specific differences in structure and function of many systems
  • 127. © 2012 Pearson Education, Inc. 29-7 Postnatal Life • Adolescence • Begins at puberty • Continues until growth is completed • Maturity (Senescence) • Aging • Reduces functional capabilities of individual • Affects homeostatic mechanisms • Sex hormone levels decline at menopause or male climacteric
  • 128. © 2012 Pearson Education, Inc. 29-7 Postnatal Life • Geriatrics • Medical specialty dealing with problems associated with aging • Trained physicians, or geriatricians
  • 129. © 2012 Pearson Education, Inc. 29-7 Postnatal Life • Effects of Aging on Organ Systems • The characteristic physical and functional changes that are part of the aging process affect all organ systems • Examples discussed in previous chapters include the following: • A loss of elasticity in the skin that produces sagging and wrinkling (p. 164) • A decline in the rate of bone deposition, leading to weak bones, and degenerative changes in joints that make them less mobile (pp. 192, 273) • Reductions in muscular strength and ability (p. 368)
  • 130. © 2012 Pearson Education, Inc. 29-7 Postnatal Life • Effects of Aging on Organ Systems • Examples discussed in previous chapters include the following: • Impairment of coordination, memory, and intellectual function (pp. 541–542) • Reductions in the production of, and sensitivity to, circulating hormones (p. 630) • Appearance of cardiovascular problems and a reduction in peripheral blood flow that can affect a variety of vital organs (p. 758) • Reduced sensitivity and responsiveness of the immune system, leading to infection, cancer, or both (p. 806)
  • 131. © 2012 Pearson Education, Inc. 29-7 Postnatal Life • Effects of Aging on Organ Systems • Examples discussed in previous chapters include the following: • Reduced elasticity in the lungs, leading to decreased respiratory function (p. 855) • Decreased peristalsis and muscle tone along the digestive tract (p. 909) • Decreased peristalsis and muscle tone in the urinary system, coupled with a reduction in the glomerular filtration rate (p. 990) • Functional impairment of the reproductive system, which eventually becomes inactive when menopause or the male climacteric occurs (p. 1069)
  • 132. © 2012 Pearson Education, Inc. 29-8 Inheritance • Nucleated Somatic Cells • Carry copies of original 46 chromosomes present in zygote • Genotype • Chromosomes and their component genes • Contain unique instructions that determine anatomical and physiological characteristics • Derived from genotypes of parents • Phenotype • Physical expression of genotype • Anatomical and physiological characteristics
  • 133. © 2012 Pearson Education, Inc. 29-8 Inheritance • Patterns of Inheritance • Homologous chromosomes • Members of each pair of chromosomes • 23 pairs carried in every somatic cell • At amphimixis, one member of each pair is contributed by spermatozoon, other by ovum
  • 134. © 2012 Pearson Education, Inc. 29-8 Inheritance • Patterns of Inheritance • Autosomal chromosomes • 22 pairs of homologous chromosomes • Most affect somatic characteristics • Each chromosome in pair has same structure and carries genes that affect same traits
  • 135. © 2012 Pearson Education, Inc. 29-8 Inheritance • Patterns of Inheritance • Sex chromosomes • Last pair of chromosomes • Determine whether individual is genetically male or female • Karyotype • Entire set of chromosomes • Locus • Gene’s position on chromosome
  • 136. © 2012 Pearson Education, Inc. Figure 29-14 A Human Karyotype
  • 137. © 2012 Pearson Education, Inc. 29-8 Inheritance • Patterns of Inheritance • Alleles are various forms of given gene • Alternate forms determine precise effect of gene on phenotype • Homozygous • Both homologous chromosomes carry same allele of particular gene • Simple inheritance • Phenotype determined by interactions between single pair of alleles
  • 138. © 2012 Pearson Education, Inc. 29-8 Inheritance • Interactions between Alleles • Heterozygous • Homologous chromosomes carry different allele of particular gene • Resulting phenotype depends on nature of interaction between alleles • Strict dominance • Dominant allele expressed in phenotype, regardless of conflicting instructions carried by other allele
  • 139. © 2012 Pearson Education, Inc. 29-8 Inheritance • Interactions between Alleles • Recessive allele • Expressed in phenotype only if same allele is present on both chromosomes of homologous pair • Incomplete dominance • Heterozygous alleles produce unique phenotype • Codominance • Exhibits both dominant and recessive phenotypes for traits
  • 140. © 2012 Pearson Education, Inc. Figure 29-15 Major Patterns of Inheritance Major Patterns of Inheritance Inheritance Involving Autosomal Chromosomes Simple Inheritance Polygenic Inheritance The phenotype is determined by a single pair of alleles; roughly 80% of your genotype falls within this category. The phenotype is determined by interactions among the alleles of several genes. Example: • Hair color (other than blond or red, which are recessive traits), skin color, eye color, and height Inheritance Involving Sex Chromosomes X-linked inheritance: The allele on the X chromosome determines the phenotype in the absence of a corresponding allele on the Y chromosome. Most known cases involve alleles that are recessive in females. Examples: • Red–green color blindness • Hemophilia (some forms) • Duchenne’s muscular dystrophy
  • 141. © 2012 Pearson Education, Inc. Figure 29-15 Major Patterns of Inheritance Major Patterns of Inheritance Strict Dominance Codominance Incomplete Dominance Examples: • Hemoglobin A production • Hemoglobin S production Two different alleles produce intermediate traits Both alleles are expressed Examples: • Type AB blood • Structure of albumins • Structure of transferrins Examples of recessive traits: • Albino pigmentation • Absence of freckles • Normal vision • Straight hair • Attached earlobes • Inability to roll tongue • Rh factor absence • Type O blood • Sickle cell anemia • Cystic fibrosis • Tay–Sachs disease • Phenylketonuria One allele dominates the other allele and determines the phenotype Examples of dominant traits: • Normal skin pigmentation • Freckles • Nearsightedness • Farsightedness • Astigmatism • Curly hair • Free earlobes • Tongue rolling • Rh factor • Type A or B blood • Huntington’s disease Inheritance Involving Autosomal Chromosomes
  • 142. © 2012 Pearson Education, Inc. 29-8 Inheritance • Penetrance and Expressivity • Penetrance • Percentage of individuals with particular genotype that show “expected” phenotype • Expressivity • Extent to which particular allele is expressed • Teratogens • Factors that result in abnormal development
  • 143. © 2012 Pearson Education, Inc. 29-8 Inheritance • Predicting Inheritance • Punnett square • Simple box diagram used to predict characteristics of offspring • Polygenic inheritance • Involves interactions among alleles on several genes • Cannot predict phenotypic characteristics using Punnett square • Linked to risks of developing several important adult disorders
  • 144. © 2012 Pearson Education, Inc. Figure 29-16a Predicting Phenotypic Characters by Using Punnett Squares Maternal alleles (contributed by the ovum). Every ovum will carry the recessive gene a. Paternal alleles (contributed by the spermatozoon). Every sperm produced by a homozygous dominant (AA) father will carry the A allele. All have normal skin pigmentation If the father is homozygous for normal pigmentation, all of the children will have the genotype Aa, and all will have normal skin pigmentation.
  • 145. © 2012 Pearson Education, Inc. Figure 29-16b Predicting Phenotypic Characters by Using Punnett Squares Half of the sperm produced by a heterozygous (Aa) father will carry the dominant allele A, and the other half will carry the recessive allele a. If the father is heterozygous for normal skin pigmentation, the probability that a child will have normal pigmentation is reduced to 50%. Maternal alleles 50% of the children are heterozygous and have normal pigmentation 50% of the children are homozygous recessive and exhibit albinism.
  • 146. © 2012 Pearson Education, Inc. 29-8 Inheritance • Predicting Inheritance • Suppression • One gene suppresses other • Second gene has no effect on phenotype • Complementary gene action • Dominant alleles on two genes interact to produce phenotype different from that seen when one gene contains recessive alleles
  • 147. © 2012 Pearson Education, Inc. 29-8 Inheritance • Sources of Individual Variation • During meiosis, maternal and paternal chromosomes are randomly distributed • Each gamete has unique combination of maternal and paternal chromosomes
  • 148. © 2012 Pearson Education, Inc. 29-8 Inheritance • Genetic Recombination • During meiosis, various changes can occur in chromosome structure, producing gametes with chromosomes that differ from those of each parent • Greatly increases range of possible variation among gametes • Can complicate tracing of inheritance of genetic disorders
  • 149. © 2012 Pearson Education, Inc. 29-8 Inheritance • Genetic Recombination • Crossing over • Parts of chromosomes become rearranged during synapsis • When tetrads form, adjacent chromatids may overlap • Translocation • Reshuffling process • Chromatids may break, overlapping segments trade places
  • 150. © 2012 Pearson Education, Inc. Figure 29-17 Crossing Over and Recombination Tetrad at synapsis. Synapsis, with the formation of a tetrad during meiosis Crossing over. Crossing over of portions of two homologous chromosomes Recombination. The exchange of corresponding segments and groups of genes increases chromosomal variation among the gametes produced.
  • 151. © 2012 Pearson Education, Inc. 29-8 Inheritance • Genetic Recombination • Genomic imprinting • During recombination, portions of chromosomes may break away and be deleted • Effects depend on whether abnormal gamete is produced through oogenesis or spermatogenesis
  • 152. © 2012 Pearson Education, Inc. 29-8 Inheritance • Genetic Recombination • Chromosomal abnormalities • Damaged, broken, missing, or extra copies of chromosomes • Few survive to full term • Produce variety of serious clinical conditions
  • 153. © 2012 Pearson Education, Inc. 29-8 Inheritance • Mutation • Changes in nucleotide sequence of allele • Spontaneous mutations • Result of random errors in DNA replication • Errors relatively common, but in most cases error is detected and repaired by enzymes in nucleus • Errors that go undetected and unrepaired have potential to change phenotype • Can produce gametes that contain abnormal alleles • Carriers • Individuals who are heterozygous for abnormal allele but do not show effects of mutation
  • 154. © 2012 Pearson Education, Inc. 29-8 Inheritance • Sex-Linked Inheritance • Sex Chromosomes • X Chromosome • Considerably larger than Y • Has more genes than does Y chromosome • Carried by all oocytes • Y Chromosome • Includes dominant alleles specifying that the individual will be male • Not present in females
  • 155. © 2012 Pearson Education, Inc. 29-8 Inheritance • Sperm • Carry either X or Y chromosome • Because males have one of each, can pass along either • X-Linked • Genes that affect somatic structures • Carried by X chromosome • Inheritance does not follow pattern of alleles on autosomal chromosomes
  • 156. © 2012 Pearson Education, Inc. Figure 29-18 Inheritance of an X-Linked Trait A woman—who has two X chromosomes—can be either homozygous dominant (XC XC ) or heterozygous (XC Xc ) and still have normal color vision. She will be unable to distinguish reds from greens only if she carries two recessive alleles, Xc Xc . A man has only one X chomosome, so whichever allele that chromosome carries determines whether he has normal color vision or is red–green color blind. Normal female Normal female (carrier) Color blind male Normal male
  • 157. © 2012 Pearson Education, Inc. 29-8 Inheritance • The Human Genome Project and Beyond • Goal was to transcribe entire human genome • Has mapped thousands of human genes • Genome • Full complement of genetic material • Karyotyping • Determination of individual’s complete chromosomal complement
  • 158. © 2012 Pearson Education, Inc. Figure 29-19 A Map of Human Chromosomes Color Blindness (multiple forms) Chapter 17 Fragile-X Syndrome Chapter 29 Hemophilia Chapter 19 Neurofibromatosis, Type 2 Tumors of the auditory nerves and tissues surrounding the brain Down’s Syndrome Chapter 29 Amyotrophic Lateral Sclerosis* Chapter 15 ADA Deficiency An enzyme deficiency that affects the immune system Familial Hypercholesterolemia Extremely high cholesterol Myotonic Dystrophy Form of muscular dystrophy in which symptoms often develop after puberty Amyloidosis Accumulation of an insoluble fibrillar protein in the tissues Breast Cancer* Chapter 28 Polycystic Kidney Disease Chapter 26 Tay–Sachs Disease Lysosomal storage disease affecting neural tissue Marfan’s Syndrome Chapter 6 Alzheimer’s Disease* Chapter 16 α1-Antitrypsin Deficiency Causes a predisposition to develop emphysema Retinoblastoma A relatively common tumor of the eye, accounting for 2% of childhood malignancies PKU (phenylketonuria) Chapter 25 Muscular Dystrophy Chapter 10 Prostate Cancer Chapter 28 Gaucher’s Disease Lysosomal storage disease caused by excess glycolipids in plasma membranes Familial Colon Cancer* Chapter 24 Retinitis Pigmentosa* Chapter 17 Huntington’s Disease* Chapter 17 Familial Polyposis of the Colon Abnormal tissue growths that commonly lead to colon cancer Spinocerebellar Ataxia Destroys neurons in the brain and spinal cord, resulting in loss of muscle control Cystic Fibrosis Chapter 23 Burkitt’s Lymphoma Cancer of lymphocytes; a type of non-Hodgkin lymphoma Retinitis Pigmentosa* Chapter 17 Epilepsy, progressive Chapter 14 Malignant Melanoma Chapter 5 Ovarian Cancer Chapter 28 Multiple Endocrine Neoplasia, Type 2 Tumors in endocrine glands and other tissues SCID Chapter 22 Diabetes Mellitus, Type 1 Chapter 18 Sickle Cell Anemia Chapter 19 * One form of the disease CHROMOSOME PAIRS XY 1 2 3 4 5 6 7 8 9 10 11121314 15 16 17 18 19 20 21 22