Chapter 027

The Human Body in Health and Illness, 4th edition

Barbara Herlihy

Chapter 27:Human Development

and Heredity

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Lesson 27-1 Objectives

• Describe the process of fertilizationwhen, where, and how it occurs.

• Describe the process of developmentcleavage, growth, morphogenesis, and differentiation.

• Explain the three periods of prenatal developmentearly embryonic, embryonic, and fetal periods.

Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights

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Lesson 27-1 Objectives (cont’d.)

• State two functions of the placenta.• Explain hormonal changes during pregnancy.• Describe the hormonal changes and stages of

labor.


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Fertilization: Sperm and Egg Unite

• When:– Near midcycle, ovulation

• Where:– First third of the fallopian tube

• How:– At intercourse, sperm swim to fallopian tube– At fertilization, nuclei of sperm and egg unite

• Result: The zygote– Has 46 chromosomes, 23 each from male and female


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Prenatal Development

• Three periods– Early embryonic, first 2 weeks– Embryonic, weeks 3 to 8– Fetal, week 9 to birth

• Pregnancy: Conception to birth– 38 weeks (~9 months)– Divided into trimesters


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Prenatal development includes…

• Cleavage: Cell division by mitosis• Growth: Size of the cells increase• Morphogenesis: Shaping of the cell cluster• Differentiation: Cellular specialization


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Early Embryonic PeriodZygoteFertilized ovum

Blastomeres Mitosis

MorulaRaspberry (16 cells)

BlastocystsEarly and lateTrophoblastic cellsImplantation


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ZygoteFertilized ovum

Blastomeres Mitosis



ZygoteFertilized ovum

Blastomeres Mitosis



Twinning

• Monozygotic (identical) – Develop from the same zygote – Have identical genetic information– One egg, one sperm

• Dizygotic (fraternal)– Develop from two different zygotes – Do not have the same genetic information– Like having two separate pregnancies – Two eggs, two sperm


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Embryonic Period: Extraembryonic Membranes

• Amnion amniotic sac, fluid

• Chorion chorionic villi, placenta

• Yolk sac RBCs, immature sex cells

• Allantois urinary bladder, umbilical cord


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Chorionic Villi and Placenta

Placenta formed when chronic villi penetrate endometrium – Site for fetal eating,

breathing, excreting– Secretes hormones– Umbilical cord joins

fetus, placenta


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Diagnostic Tests for Birth Defects

• Amniocentesis

• Chorionic villi sampling


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Embryonic Period

• Organogenesis: Formation of organs • Embryonic disc: Formed by blastocyst’s inner

cell mass • Inner cell mass forms three primary germ

layers– Ectoderm– Mesoderm– Endoderm


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Embryonic Period: Teratogens

• Particularly harmful in embryonic period

• Cause severe birth defects


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Fetal Period: Shaping Up•Body proportions change.•Fetus is viable at 20 weeks.•Preterm: Birth before 38 weeks


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Fetal Period: Terms

• Quickening: Movement of fetus felt by mother• Lanugo: Fine hair covering the fetus• Vernix caseosa: White, cheese-like substance

protecting fetal skin from amniotic fluid• Abortion: Loss of fetus at any time

– Spontaneous (miscarriage)– Induced– Therapeutic


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Maternal Changes in Pregnancy

• Rate of metabolism increases.• Blood volume expands 40%-50%.• Respiratory activity increases.• Kidneys produce more urine.• Nutritional needs increase.• Increased hormonal secretions: hCG, estrogen,

progesterone, prolactin, oxytocin, prostaglandins, thyroid hormones, aldosterone


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Labor: The Mama Drama

• Forceful contractions expel fetus from the uterus

• Hormones involved– Progesterone: Quiets uterine contractions before

labor – Estrogen: Sensitizes uterus to oxytocin – Prostaglandins: Initiate uterine contractions– Oxytocin: Stimulates uterine contractions


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Birth of Baby: Stages of Labor

• Dilation stage (B)

• Expulsion stage (C)

• Placental stage (D)


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Lesson 27-2 Objectives• Describe the structure of the breast and

lactation.• Describe the relationships among

deoxyribonucleic acid (DNA), chromosomes, and genes.

• Define karyotype.• Explain how the gender of the child is

determined.• State the difference between congenital and

hereditary diseases.


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Breast: Structure

• Mammary glands – 15-20 lobes

• Alveolar glands– Located in lobes– Secrete colostrum and

milk into lactiferous ducts

• Nipple and areola• Suspensory ligaments


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Breast: Hormones of Lactation

• Estrogen and progesterone– Prepare breasts for lactation

• Prolactin – Suppressed during pregnancy by estrogen and

progesterone– Stimulates milk production after birth

• Oxytocin– Stimulates release of milk from breast– Milk let-down reflex


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Lactation: Milk Let-Down Reflex

• Sensory stimulus, suckling

• Posterior pituitary releases oxytocin

• Oxytocin stimulates breasts’ smooth muscle to contract, releasing milk.


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Postnatal Adjustments in Baby

• Breathing is established.• Blood flow through lungs begins.• Mechanisms for temperature regulation adjust.• Functioning digestive system produces

meconium.– Baby’s first stool– Tarry and dark green

• Most organs begin to function more efficiently.


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Developmental Stages: Life Span

• Neonatal period: Birth to 4 weeks• Infancy: 2nd to 12th month • Childhood: 2nd year to puberty• Adolescence: Puberty to adulthood• Adulthood: Adolescence to old age• Senescence: Old age to death


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Heredity

• Transmission of traits from parent to child– Examples: Color of hair and eyes, dimples, Rh

factor, ear lobes

• DNA: Location of genetic information• Chromosomes: Threadlike structures of tightly

wound DNA in nuclei of most cells • Genes: Segments of DNA carrying information

for a specific trait


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Chromosomes

• Exist in pairs– 23 pairs, one chromosome from male and female

• Autosomes– 22 pairs of non-sex chromosomes

• Sex chromosomes– One pair , either X or Y


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Karyotype: Genetic Art

• Displays the paired chromosomes

• Used to diagnose genetic disorders


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Heredity: Dominance

• Dominant gene expresses itself; overshadows a recessive gene

• Recessive gene unexpressed if paired with a dominant gene

• Codominant genes express a trait equally– Blood types


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Gender Determination: Xs and Ys

• Girl’s sex chromosome is XX.

• Boy’s sex chromosome is XY.

• Male determines gender of offspring.

• Sex-linked traits are carried on sex chromosomes.


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Heredity: Terms

• Genetic expression: Determines offspring’s appearance

• Genetic mutation: Change in the genetic code• Congenital condition: Any disease or defect

present at birth• Hereditary disease: Genetically transmitted• Gene therapy: Insertion of normal genes into

cells with abnormal genesCopyright © 2011, 2007 by Saunders,

an imprint of Elsevier Inc. All rights reserved.

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Chapter 027

Health & Medicine

Transcript of Chapter 027