Development and Inheritance

1. Development and Inheritance Chapter 19

2. Development • Involves: • The division and differentiation of cells • The changes that produce and modify anatomical structures. • Begins at fertilization (conception) • Occurs among several periods: • Embryological • Fetal • Prenatal • Postnatal INTRO:Development

3. Development • QUESTION: Why might the science of development important to us as Christians? INTRO:Development

4. Inheritance • The transfer of genetically determined characteristics from generation to generation. • Taken to the extreme, this would reference evolutionary biology. • At minimum, we can account for adaptation (aka microevolution). • Genetics is the study of the mechanisms responsible for inheritance. INTRO:Inheritance

5. Fusion of 2 haploid gametes: • Spermatazoon • Paternal genetic information • Takes ½-2 hours to go from vagina to upper uterine tube • 10,000 of 200,000,000 get to upper uterine tube • <100 reach the ovum. • Multiple spermatozoa required to breach corona radiata • Ovum • Nourishment • Genetic programming • 2x diameter of spermatozoon • 2000x volume of spermatozoon • Produce a zygote of 46 chromosomes • Pop culture references: • Tool – 46 & 2 Fertilization

6. Activation of the oocyte • Ovulation happens before the oocyte is completely mature. • It’s development is on pause: fertilization or death • The corona radiatamust be affected by multiple sperm. • The collective pool of the enzumehyaluronidase from the acrosomal body of the spermatozoa breaks the bonds between adjacent follicle cells of the corona radiata. • Activation occurs when a spermatozoon contacts the zonapellucida. This membrane is broken by additional acrosomal enzymes to breach the oocyte membrane. This is fertilization. Fertilization

7. An overview of prenatal development • Prenatal development (before birth) • Aka, gestation, pregnancy • 3 trimesters Fertilization

8. 1st TRIMESTER • Period of embryological and early fetal development, also the most dangerous. • The basic components of each major organ systems appear. • Only about 40% of embryos survive this trimester. • 4 general processes occur: • Cleavage & blastocyst formation • Implantation • Placentation • Embryogenesis The First Trimester

9. CLEAVAGE & BLASTOCYST FORMATION • Cleavage: a series of cell divisions that begins immediately after fertilization. • 1st cleavage is 30 hours after fertilization. • Every other cleavage is 10-12 hours after the previous. The First Trimester

10. CLEAVAGE & BLASTOCYST FORMATION • Blasto-meres: (blast – precursor; meros – part): the products of cleavage; genetically identical daughter cells. • The blastomeres form a blastocyst. • Blasto-cyst: (precursor cell) a hollow ball with an inner cavity called a blastocoele. • Blasto-coele: (koiloma – cavity). • Tropho-blast: (tropho – food): food for embryo. The First Trimester

11. IMPLANTATION When it’s fully formed, the blastocyst contacts the endometrium. At that point, cleavage ends and implantation begins. These structures form: • Amniotic cavity • Gastrulation and germ layer • Extraembryonic membranes • Yolk sac • Amnion • Allantois • Chorion hCG – human chorionic gonadotropin appears in bloodstream after implantation. The First Trimester

12. PLACENTATIONPlacenta formation Placenta – temporary structure in uterine wall. • Provides a site for diffusion between the fetal and maternal circulatory systems. • Functions as a temporary endocrine organ for the mother. EMBRYOGENESISMaking an embryo The First Trimester

13. End of week 12 is the end of the first trimester • At this point the basic elements of all the major organ systems have formed. • 2ND TRIMESTER: Mostly development of organs and completing organ systems. Body proportions change and at the end of the 2nd trimester, the baby looks more familiar as a human. • Amnion: • baby’s growth is faster than the amnion’s • Once it touches the chorion, they fuse. The Second and Third Trimester

14. 3rd TRIMESTER: • Very rapid fetal growth. • The baby is fully functional at the beginning of this trimester. • A baby born 1-2 months premature has a decent chance of survival. The Second and Third Trimester

15. INCREASES IN THE MOTHER’S SYSTEMS: • Respiratory rate • Tidal volume • Blood volume • Nutritional requirements climb 10-30% • GFR increases by 50% • Mammary gland size (and secretory activity starts) • Uterus size Effects of pregnancy on Maternal Systems

16. THE UTERUS • Increase occurs mostly from enlargement of existing smooth muscle cells rather than by the increase in the total number of cells. • Estrogen • Stimulating hormone • Contraction increaser • Progesterone • Inhibiting hormone • Contraction decreaser • Also present: prostaglandins and relaxin Effects of pregnancy on Maternal Systems

17. The goal of labor is parturition: forcibly expelling the baby from the uterus. • 3 Stages of Labor • Dilation • Expulsion • Placental • Dilation: references the opening of the cervix. • Beginning of labor. • Baby slides down cervical canal. • Varies greatly, but typically lasts 8+ hours. • Contractions sweep from top of uterus toward cervix. • Occur every 10-30 minutes and steadily increase in frequency and strength • Amnion rupture: “water breaks” Labor and Delivery

18. Expulsion: occurs until baby is out of vagina. • Complete dilation of cervix, pushed open by baby. • Normally takes less than 2 hours. • Newborn arrival is delivery, or birth. • Procedures for complications in first 2 stages: • Episiotomy • If vaginal canal is too small, it poses a danger to perineal tearing. • Perineum sometimes intentionally cut (episiotomy) to ensure a clean break in the skin versus jagged edges. • C-section (cesarean section) • Incision made through abdominal wall • Uterus opened just enough to allow delivery. Labor and Delivery

19. Placental Stage • Once baby is delivered, placenta still in uterus • Contraction of uterus tears the connection between the endometrium and the placenta. • Ejection of placenta (afterbirth) normally occurs within 1 hour of delivery • Ejection accompanied by blood loss. Labor and Delivery

20. Premature Labor • Contractions occur prior to full development. • Survivability dependent largely on birth weight • <14 oz. will not survive – organs cannot support life. • 17.6 oz. is the threshold. • 25-27 weeks increases developmental abnormality risk. • 28-36 weeks is called prematuredelivery • High rate of survivability and low chance of developmental abnormalities. Labor and Delivery

21. Multiple Births • 1:89 births are twins • 1:892 births are triplets • Fraternal – dizygotic; “2-zygotes” • 2 eggs fertilized simultaneously • Can be of the same or different sex • 70% of all twin births • Identical – monozygotic; “1 zygote” • Happens 2 ways: • 1. Blastomeres split early in cleavage • 2. Inner cell mass splits before gastrulation • If the split is not complete, conjoined twins develop • Same sex • 30% of all twin births Labor and Delivery

22. Life stages: • Neonatal • Infancy • Childhood • Adolescence • Maturity Postnatal Development

23. Neonatal period • 0-1 month after birth • Blood flow changes • Heart rate decreases • Body temperature control limited • Urine can’t really be concentrated yet • From the mom, mammary glands first produce colostrum for a few days, then milk. • Colostrum • High protein concentration (many are antibodies) • Low fat • Milk • Water, proteins, amino acids, lipids, sugars, salts, lysozymes (enzymes with antibiotic properties. Postnatal development

24. Phenotype: physical display • Genotype: genetic information • Allele: all the forms of a particular gene: A/a • i.e. the letter of the alphabet. • Upper-case letter (A): dominant • Lower-case letter (a): recessive • Homozygous: same case • Heterozygous: different case • 2 members of a pair are homologous • 22 autosomal chromosomes • 1 sex chromosome pair Genetics, Development, and Inheritance

25. Types of inheritance: • Simple – single pair of alleles • Polygenetic – interactions among >1 pair of alleles • Males: XY • Females: XX Genetics, Development, and Inheritance