1. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Fundamentals of Anatomy & Physiology SIXTH EDITION Frederic H. Martini Lecture 29, Development and Inheritance Lecturer: Dr. Barjis Room: P313 Phone: (718) 260-5285 E-Mail: ibarjis@citytech.cuny.edu

2. Learning Objectives Explain the relationship between differentiation and development and specify the various stages of development Describe the process of fertilization List the three prenatal periods and describe the major events associated with each Discuss the importance of the placenta as an endocrine organ

3. Learning Objectives Discuss the structural and functional changes in the uterus during gestation List and discuss the events that occur during labor and delivery Relate basic principles of genetics to the inheritance of human traits

4. Development involves: 1) Cell division and differentiation Differentiation is the creation of different types of cells 2) changes in anatomical structures Anatomical changes include gradual modification of physical and physiological characteristics Development begins at fertilization Differentiation and development

5. Development can be divided into: Prenatal and postnatal development Prenatal development begins at fertilization and ends with birth Prenatal development includes: Embryological development Changes occurring during the first two months after fertilization Fetal development Begins at the start of the ninth week and continues until birth Postnatal development Commences at birth and continues to maturity Stages of development

6. Fertilization is fusion of two haploid gametes (egg and sperm) each with 23 chromosome to produce a zygote that contains 46 chromosomes Fertilization occurs in the uterine tubes Within a day of ovulation Spermatozoa cannot fertilize an ovum until after capacitation Fertilization (conception)

7. Fertilization

8. Fertilization Steps Step 1 Ovulation At ovulation the oocyte is in metaphase of meiosis II Both the occyte and the polar body is surrounded by corona radiate Step 2 Fertilization Oocyte is surrounded by the sperms Acrosomal enzyme from several sperms creates gaps in corona radiata One sperm makes contact with the oocyte membrane Sperm and oocyte fused The process of meiosis will complete

9. Fertilization

10. Ovulation occurs before the oocyte is completely mature i.e. oocyte is ovulated before the process of meiosis is completed Ovulated oocyte is in metaphase of meiosis II If the egg is fertilized the process of meiosis will complete If fertilization does not occur, the oocyte disintegrate without completing the process of meiosis Oocyte is surrounded by the corona radiate Spermatozoa release hyaluronidase and acrosin Enzymes required to penetrate corona radiate Single spermatozoan contacts oocyte, fertilization begins Oocyte activation Polyspermy prevented by membrane depolarization and cortical reaction The Oocyte at Ovulation

11. Induction During prenatal development differences in cytoplasmic composition trigger changes in genetic activity Gestation periods The gestation period is divided into three integrated trimesters The Stages of Prenatal Development Embryonic and Fetal Periods

12. The first trimester is the period of embryological and early fetal development Four processes occur during the first trimeter 1) Cleavage 2) Implantation 3) Placentation 4) Embryogenesis The First Trimester

13. Cleavage - cleavage is the first cell division Zygote becomes a preembryo then a blastocyst Blastocyte includes: Trophoblast – outer layer of cells Inner cell mass – cluster of cells at one end of blastocyst The First Trimester Cleavage

14. Cleavage and Blastocyst Formation

15. Implantation Attachment of blastocyst into the uterine endometrium Occurs about 7 days after fertilization Placentation Blood vessels form around blastocyst and placenta develops The placenta is a complex organ that permits exchange between the maternal and embryonic circulatory systems The First Trimester Implantation and Placentation

16. Stages in Implantation Animation: Location of the Endometrium (see tutorial)

17. Embryogenesis Formation of a viable embryo This process establishes the foundations for all major organ systems Gastrulation Embryonic disc composed of germ layers Endoderm Mesoderm Ectoderm The First Trimester Embryogenesis

18. The Inner Cell Mass and Gastrulation

19. Gastrulation By day 12 surface cells move toward the primitive streak A third germ layer forms The three germ layers are: Ectoderm – superficial cells that did not migrate Endoderm – cells facing the blastocoele Mesoderm – migrating cells between ectoderm and endoderm Germ layers

20. Four extraembryonic membranes: Yolk sac Amnion Allantois Chorion Extraembryonic Membranes

21. Extraembryonic Membranes and Placenta Formation

24. Yolk sac Important site of blood cell formation Amnion Encloses fluid that surrounds and cushions developing embryo Allantois Eventually becomes bladder Chorion Embryo Anatomy

25. A Three-Dimensional View of Placental Structure

26. Chorionic villi extend into maternal tissue Forms intricate branching network for maternal blood Umbilical cord connects fetus to placenta Placentation

27. Trophoblast secretes hormones to maintain pregnancy HCG Estrogens Progesterone hPL Placental prolactin Relaxin Hormones of the placenta

28. 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 Second and Third Trimesters

29. The Second and Third Trimesters

30. Growth of the Uterus and Fetus

32. Developing fetus totally dependent on maternal organs Maternal adaptations include increased Respiratory rate Tidal volume Blood volume Nutrient and vitamin uptake Glomerular filtration rate Animation: Anatomy comparison of pregnant and non-pregnant (see tutorial)

33. 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

34. Factors Involved in the Initiation of Labor and Delivery

35. Labor and Delivery 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 Goal of labor is parturition

36. The Stages of Labor

37. 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

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

39. 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

40. The Milk Let-Down Reflex

41. Growth and Changes in Body Form

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

43. 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

44. 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

45. Aging affects functional capabilities of all system Senescence

46. 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

47. 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