CHAPTER 29        DEVELOPMENT AND INHERITANCE

 

I.EARLY DEVELOPMENT

        A.Pregnancy

               1. events from conception to birth

               2.Conceptus - developing offspring

               3.gestation

                       a.last menstrual period until birth

                       b.280 days

        B.fertilization (conception)

               1.sperm present in reproductive tract 72 hrs before ovulation- 24 hrs after

               2.sperm must be capacitated to fertilize ovum

                       a.enzymes released from acrosome

                       b.only one is permited to enter

               3.female and male nuclei swell 'pronuclei'

               4.zygote formed - diploid

               5.2 weeks after = preembryo

               6.3-8 weeks = embryo

               7.9 weeks to birth = fetus

        C.Preembryonic development

               1.cleavage -> blastomeres->morula (16)

                       hollow area becomes fluid filled

               2.blastocyst cavity

               3.zona pellucida degenerates

                4.outer layer of cells known as Trophoblast

               5.inner cells is embryonic disc

        D.blastocyst starts implantation

        E.trophoblast cells secrete hormone

               1.HCG

                       a.human chorionic gonadotropin

                       b.keeps corpus luteum secreting P,E

               2.trophoblast becomes chorion

               3.HCG detectable in blood of mother by 3rd week

        F.Placental takes over functions of chorion and corpus luteum

               1.chorionic villi from chorion

               2.umbilical artery and vein connect to placenta

               3.nutrients, oxygen, wastes exchanged

               4.substances cross cause congenital abnormalities

                       a.teratogens

              

II. Embryonic Development

        A.blastocyst becomes gastrula

        B.embryonic membranes form

               1.amnion

                       a.fluid filled (amniotic fluid ) sac

                       b.umbilical cord passes through

               2.yolk sac

                       a.early site of blood cell formation

               3.chorion

               4.allantois

                       a.from part of yolk sac

                       b.structural base for umbilical cord connection

                       c.becomes part of bladder

        C.Gastrulation

               1.three layered embryo formed

               2.primary germ layers

                       a.ectoderm

                       b.mesoderm

                       c.endoderm

               3.notochord

                       a.invagination of mesodermal cells

                       b.axial support

              

        D.organogenesis

               1.differentiation of germ layers

               2.ectodermal cells fold into notochord

                       a.forms a neural tube

                       b. ant = brain

                       c.post= spinal chord

                       d.gives rise to

                              (1)all nervous tissue

                              (2)epidermis and derivatives

                              (3)cornea,iris

               3.endoderm

                       a.folding

                              (1)lateral

                              (2)rostral

                              (3)caudal

                       b.gives rise to

                              (1)lining of GI, respiratory

                             

               4.mesoderm

                       a.limb buds

                       b.skeleton and muscles           

                      

 

        E. Fetal Circulation is specilized system

III.Maternal Effects of Pregnancy

        A.Uterus increases in size

               1.reaches xiphoid process

               2.shifts center of gravity

               3.weight gain

                       a.uterus

                       b.placenta

                       c.fetus

                       d.amniotic fluid

        B.Physiological changes in pregnancy

               1.increase salivation

               2.morning sickness

               3.heartburn

               4.constipation

               5.increased urine output

               6.compression on bladder

               7.increase in total body water

               8.increase BP, HR

        C.Parturition

               1.labor

                2.oxytocin acts on placenta to release prostaglandins

               3.positive feedback regulation of oxytocin for

                       contractions until delivery

               4.Dilation Stage

                       a.dilation of cervix

                       b.rupture of amnion

               5.expulsion stage

                       a.crowning- head down (breech: buttock-first)

                       b.episiotomy

               6.Placental stage

                       a.15 min

                       b.uterine contractions continue after birth

                       c.afterbirth

        D.Neonatal period

               1.up to 4 week

               2.Apgar score 8 -10 healthy

                       a.administered 1-5 min after birth

                       b.5 signs

                              (1)HR, RR, color, muscle tone, reflexes

               3.45 RR

               4.closure of circulatory shunts

               5.foramen ovale close in atrria

               6.ductus arteriosus constricts (aorta/pulm)

        E.Lactation

               1.prolactin

                       a.let-down reflex

               2.colostrum

                       a.IgA antibodies

       

                             

I.GENETICS

        A.Study of heredity

        B.Genes

               1.alleles

                       a.same locus on homologous chromosomes

                       b.same traits or alternate traits

                       c.dominant , recessive

                       d.heterozygous

                       e.homozygous

        C.Genotype- genetic makeup

        D.Phenotype- appearance

        E.Punnett Squares

               1.to determine probability of offspring genotype/phenotype

               2.possible gametes from each parent on top/bottom

               3.join for offspring

        F.Multiple allele inheritance

               1.ABO

                       a.type O has ii genotype

                       b.type A IAIA or IAi

                       c.type B IBIB or IBi

                       d.type AB IAIB

        G.Sex-linked

               1.Y chromosome is smaller than X not really homologous

               2.determines maleness

               3.gene only of the X is X-linked

               4.male has only on X chromosome so a recessive trait would be the phenotype

               5.Hemophilia, color-blindness

        H.Polygenes

               1.more than 3 alleles

               2.skin color A,a,B,b,C,c

               3.many combinations unless all ABC dark or abc light

               4.broad range of pigmentation in offspring is possible

        I.Pedigree analysis

               1.carriers

               2.circles = females

               3.square = male

               4.filled if have trait, empty if do not

               5.half filled if carrier

               6.marrying relatives

                       a.if recessive traits are present more likely in both and increase chance of homozygous recessive or abnormality

        J. amniocentesis

               1.detection in amniotic fluid

               2.need a cell to look at chromosomes

II.Do a Punnett Square to determine what your offspring's probability of having blue eyes (bb) if yours are brown (your father had blue eyes (bb), your mother brown (BB)) and your spouse has blue eyes(bb).

 

EXAMPLES: