1. Chapter 29, part 2 Development and Inheritance

2. SECTION 29-5The Second and Third Trimesters

3. Second and Third Trimesters • Second trimester • Organ systems increase in complexity • Third trimester • Many organ systems become fully functional • Fetus undergoes largest weight change • At end of gestation fetus and uterus push maternal organs out of position

4. Figure 29.9 The Second and Third Trimesters Figure 29.9a, b

5. Figure 29.10 Growth of the Uterus and Fetus Figure 29.10a, b

6. Figure 29.10 Growth of the Uterus and Fetus Figure 29.10c, d

7. Developing fetus totally dependent on maternal organs • Maternal adaptations include increased • Respiratory rate • Tidal volume • Blood volume • Nutrient and vitamin uptake • Glomerular filtration rate PLAY Animation: Anatomy comparison of pregnant and nonpregnant

8. Structural and Functional Changes in the Uterus • Progesterone inhibits uterine muscle contraction • Opposed by estrogens, oxytocin and prostaglandins • Multiple factors interact to produce labor contractions in uterine wall

9. Figure 29.11 Factors Involved in the Initiation of Labor and Delivery Figure 29.11

10. SECTION 29-6Labor and Delivery

11. Goal of labor is parturition • Stages of labor • Dilation • The cervix dilates and fetus moves toward cervical canal • Expulsion • The cervix completes dilation and fetus emerges • Placental • Ejection of the placenta

12. Figure 29.12 The Stages of Labor Figure 29.12

13. Other labor and delivery situations • Premature labor • True labor begins before fetus has completed normal development • Difficult deliveries • When the fetus faces the pubis rather than the sacrum • The legs or buttocks enter the vaginal canal first (breech births) • Multiple births • Twins, triplets, etc. • Dizygotic or monozygotic situations

14. SECTION 29-7Postnatal Development

15. Postnatal life stages • Neonatal period • Infancy • Childhood • Adolescence • Maturity • Senescence begins at maturity and ends in death

16. The neonatal period • From birth to one month • Respiratory, circulatory, digestive and urinary systems adjust • Infant must thermoregulate • Maternal mammary glands secrete colostrum first few days • Milk production thereafter • Both secretions are released via the milk let-down reflex • Body proportions change during infancy and childhood

17. Figure 29.13 The Milk Let-Down Reflex Figure 29.13

18. Figure 29.14 Growth and Changes in Body Form Figure 29.14

19. Adolescence • Begins at puberty • The period of sexual maturation • Ends when growth is completed

20. Puberty marked by • Increased production of GnRH • Rapid increase in circulating FSH and LH • Ovaries and testes become sensitive to FSH / LH • Gamete production initiated • Sex hormones produced • Growth rate increases

21. Hormonal changes at puberty produce gender specific differences in system • Differences are retained throughout life • Adolescence continues until growth completed • Further changes occur when sex hormones decline • Menopause • Male climacteric

22. Senescence • Aging affects functional capabilities of all system

23. SECTION 29-8Genetics, Development, and Inheritance

24. Genes and chromosomes • Every somatic cell carries copies of the 46 original chromosomes in the zygote • Genotype – Chromosomes and their component genes • Phenotype – physical expression of the genotype

25. Patterns of inheritance • Somatic cells contain 23 pairs of chromosomes • Homologous chromosomes • 22 pair of autosomes and one pair of sex chromosomes • Chromosomes contain DNA • Genes are functional segments of DNA

26. Figure 29.15 Human Chromosomes Figure 29.15

27. Various forms of a gene are called alleles • Homozygous if homologous chromosomes carry the same alleles • Heterozygous if homologous chromosomes carry different alleles • Alleles are either dominant or recessive depending on expression • Punnett square diagram predicts characteristics of offspring

28. Figure 29.16 Predicting Phenotypic Characteristics by Using Punnett Squares Figure 29.16a, b

29. Inheritance • Simple inheritance • Phenotypic characteristics are determined by interactions between single pair of alleles • Polygenic inheritance • Phenotypic characteristics are determined by interactions among alleles on several genes

30. Sources of individual variation • Genetic recombination • Gene reshuffling • Crossing over and translocation • Occurs during meiosis • Spontaneous mutations • Random errors in DNA replication

31. Figure 29.17 Crossing over and Translocation Figure 29.17a-c

32. Sex-linked inheritance • Sex chromosomes are X chromosome and Y chromosome • Male = XY • Female = XX • X chromosome carries X-linked (sex linked) genes • Affect somatic structures • Have no corresponding alleles on Y chromosome

33. Figure 29.18 X-Linked inheritance Figure 29.18

34. The Human Genome Project • Mapped more than 38,000 of our genes • Including some responsible for inherited disorders

35. Figure 29.19 A Map of the Human Chromosomes Figure 29.19

36. You should now be familiar with: • The relationship between differentiation and development, and the various stages of development • The process of fertilization • The three prenatal periods and describe the major events associated with each • The importance of the placenta as an endocrine organ

37. You should now be familiar with: • The structural and functional changes in the uterus during gestation • The events that occur during labor and delivery • The basic principles of genetics as they relate to the inheritance of human traits