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The Human Body in Health and Illness, 4th edition
Barbara Herlihy
Chapter 27:Human Development
and Heredity
1
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
reserved.2
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.
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.3
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
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.4
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
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.5
Prenatal development includes…
• Cleavage: Cell division by mitosis• Growth: Size of the cells increase• Morphogenesis: Shaping of the cell cluster• Differentiation: Cellular specialization
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.6
Early Embryonic PeriodZygoteFertilized ovum
Blastomeres Mitosis
MorulaRaspberry (16 cells)
BlastocystsEarly and lateTrophoblastic cellsImplantation
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.7
ZygoteFertilized ovum
Blastomeres Mitosis
MorulaRaspberry (16 cells)
BlastocystsEarly and lateTrophoblastic cellsImplantation
ZygoteFertilized ovum
Blastomeres Mitosis
MorulaRaspberry (16 cells)
BlastocystsEarly and lateTrophoblastic cellsImplantation
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
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.8
Embryonic Period: Extraembryonic Membranes
• Amnion amniotic sac, fluid
• Chorion chorionic villi, placenta
• Yolk sac RBCs, immature sex cells
• Allantois urinary bladder, umbilical cord
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.9
Chorionic Villi and Placenta
Placenta formed when chronic villi penetrate endometrium – Site for fetal eating,
breathing, excreting– Secretes hormones– Umbilical cord joins
fetus, placenta
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.10
Diagnostic Tests for Birth Defects
• Amniocentesis
• Chorionic villi sampling
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.11
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
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.12
Embryonic Period: Teratogens
• Particularly harmful in embryonic period
• Cause severe birth defects
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.13
Fetal Period: Shaping Up•Body proportions change.•Fetus is viable at 20 weeks.•Preterm: Birth before 38 weeks
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.14
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
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.15
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
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.16
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
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.17
Birth of Baby: Stages of Labor
• Dilation stage (B)
• Expulsion stage (C)
• Placental stage (D)
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.
18
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.
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.19
Breast: Structure
• Mammary glands – 15-20 lobes
• Alveolar glands– Located in lobes– Secrete colostrum and
milk into lactiferous ducts
• Nipple and areola• Suspensory ligaments
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.20
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
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.21
Lactation: Milk Let-Down Reflex
• Sensory stimulus, suckling
• Posterior pituitary releases oxytocin
• Oxytocin stimulates breasts’ smooth muscle to contract, releasing milk.
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.22
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.
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.23
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
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.24
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
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.25
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
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.26
Karyotype: Genetic Art
• Displays the paired chromosomes
• Used to diagnose genetic disorders
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.27
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
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.28
Heredity: Dominance (cont’d.)
Eye color: Dominant and recessive genesCopyright © 2011, 2007 by Saunders,
an imprint of Elsevier Inc. All rights reserved.
29
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.
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.30
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.
31