Chapter 21Growth and Development

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PRENATAL PERIOD

Conception to birth Embryology

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PRENATAL PERIOD Fertilization to implantation requires about 10

days Fertilization normally occurs in outer third of

oviduct

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PRENATAL PERIOD

Fertilization to

implantation ZygoteMorulaBlastocystImplantation

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PRENATAL PERIOD Implantation

Yolk sacAmniotic cavity

Chorion Placenta

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PRENATAL PERIOD Periods of development

Gestation period – about 39 weeks Embryonic phase Fetal phase All organ systems are formed and

functioning by month 4 of gestation

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In the Womb

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Get Your Own Room, Buddy!

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PRENATAL PERIOD

Three primary germ layers:Endoderm—inside layer

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PRENATAL PERIOD

Three primary germ layers:Mesoderm – middle layer

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PRENATAL PERIOD

Three primary germ layers:Ectoderm—outside layer

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GERM LAYERS

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PRENATAL PERIOD

Histogenesis and organogenesisNew tissuesNew organs Cell differentiation, multiplication,

growth, and rearrangementFrom 4 months of gestation until

delivery, the development of the baby is mainly a matter of growth

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PRENATAL PERIOD

Birth defectsAny structural or functional

abnormality present at birthMay be caused by genetic factors

•Abnormal genes•Abnormal number of chromosomes

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PRENATAL PERIODBirth defects

May be caused by environmental factors•Teratogens• Include radiation, chemicals, and

infections•First trimester

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BIRTH, OR PARTURITION Process of birth called parturition

At the end of week 39 of gestation, the uterus becomes “irritable”

Fetus takes head-down position against the cervix

Muscular contractions begin, and labor is initiated

Amniotic sac (“bag of waters”) rupturesCervix dilatesFetus moves through vagina to exterior

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FULL TERM

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BIRTH, OR PARTURITION Stages of labor

Stage one—period from onset of uterine contractions until dilation of the cervix is complete

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BIRTH, OR PARTURITION Stages of labor

Stage two—period from the time of maximal cervical dilation until the baby exits through the vagina

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BIRTH, OR PARTURITION

Stages of labor Stage three—process of expulsion of

the placenta through the vagina

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POSTNATAL PERIOD

Divisions of postnatal periodInfancyChildhoodAdolescence and adulthoodOlder adulthood

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Obvious changes in the physical appearance of the body—in whole and in proportion—occur between birth and maturity

POSTNATAL PERIOD

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POSTNATAL PERIOD Infancy

Neonatal period • Neonatology

Cardiovascular changesRespiratory

changes

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POSTNATAL PERIOD Infancy

Developmental changes between the neonatal period and 18 months include:• Doubling of birth weight by 4

months and tripling by 1 year• 50% increase in body length

by 12 months• Development of normal spinal

curvature by 15 months• Ability to:

raise head by 3 months crawl by 10 months stand alone by 12 months run by 18 months

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POSTNATAL PERIOD

Childhood Extends from end of infancy to puberty

—13 years in girls and 15 in boys Overall rate of growth remains rapid but

decelerates Continuing development of motor and

coordination skills Loss of deciduous (baby) teeth and

eruption of permanent teeth

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POSTNATAL PERIOD

Adolescence Period of rapid growth resulting in

sexual maturity•Average age range usually from 13 to

19 years•Appearance of secondary sex

characteristics •Growth spurt typical

girls ≈10 boys ≈ 12

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POSTNATAL PERIOD

AdulthoodGrowth plates

•other structures such as the sinuses assume adult placement

Maintenance of existing body tissues

Degeneration of body tissue begins

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POSTNATAL PERIOD

Older adulthood Degenerative changes

•aka senescenceEvery organ system Senescence culminates in death

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EFFECTS OF AGING

Skeletal systemchanges in the texture,

calcification, and shape of bonesBone spurs Bones become porous and

fracture easilyDegenerative joint diseases

•osteoarthritis

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EFFECTS OF AGING

Integumentary system (skin)With age, skin “sags” and

becomes thin, dry, wrinkledPigmentation problems are

commonFrequently thinning or loss of

hair occurs

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EFFECTS OF AGING

Urinary systemNephron units decrease

Blood flow to kidney Bladder problems

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EFFECTS OF AGING

Respiratory systemBarrel chestDecreased respiratory

efficiencyRespiratory membrane

thickens

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EFFECTS OF AGING

Cardiovascular systemDegenerative heart and

blood vessel disease AtherosclerosisArteriosclerosisHypertension

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EFFECTS OF AGINGSpecial senses

Gradual Farsightedness CataractGlaucoma Loss of hair cells in inner ear Decreased transmission of sound

waves Hearing impairment Loss of taste buds