Mosby items and derived items © 2007, 2003 by Mosby, Inc.Slide 1 Chapter 33 Growth and Development.

Mosby items and derived items © 2007, 2003 by Mosby, Inc.

Chapter 33Chapter 33Growth and DevelopmentGrowth and Development


IntroductionIntroduction

Prenatal period—period beginning with Prenatal period—period beginning with conception and ending at birthconception and ending at birth

Postnatal period—period beginning with birth Postnatal period—period beginning with birth and continuing until deathand continuing until death

Human developmental biology—study of Human developmental biology—study of changes occurring during the cycles of life changes occurring during the cycles of life from conception to deathfrom conception to death


A New Human LifeA New Human Life Production of sex cells—spermatozoa are produced by Production of sex cells—spermatozoa are produced by

spermatogenesis; ova are produced by oogenesisspermatogenesis; ova are produced by oogenesis Meiosis (Figures 33-1 and 33-2)Meiosis (Figures 33-1 and 33-2)

• Special form of cell division that reduces the number of chromosomes in each Special form of cell division that reduces the number of chromosomes in each daughter cell to one half of those in the parent celldaughter cell to one half of those in the parent cell

• Mature ova and sperm contain only 23 chromosomes, half as many as other Mature ova and sperm contain only 23 chromosomes, half as many as other human cellshuman cells

• Meiotic division—two cell divisions that occur one after another in successionMeiotic division—two cell divisions that occur one after another in succession Meiotic division I and meiotic division IIMeiotic division I and meiotic division II Both divisions made up of an interphase, prophase, metaphase, anaphase, and Both divisions made up of an interphase, prophase, metaphase, anaphase, and

telophasetelophase• During prophase I of meiosis, “cross over” occurs where genetic material is During prophase I of meiosis, “cross over” occurs where genetic material is

“shuffled”“shuffled”• Daughter cells formed by meiotic division I contain a haploid number of Daughter cells formed by meiotic division I contain a haploid number of

chromosomeschromosomes• Meiotic division II—essentially the same as mitotic division; reproduces each Meiotic division II—essentially the same as mitotic division; reproduces each

of the two cells formed by meiotic division I and forms four cells, each with the of the two cells formed by meiotic division I and forms four cells, each with the haploid number of chromosomeshaploid number of chromosomes


A New Human LifeA New Human Life

Production of sex cells (cont.)Production of sex cells (cont.)

Spermatogenesis (Figure 33-3)—process by Spermatogenesis (Figure 33-3)—process by which primitive male sex cells become which primitive male sex cells become transformed into mature sperm; begins transformed into mature sperm; begins approximately at puberty and continues approximately at puberty and continues throughout a man’s lifethroughout a man’s life

• Meiotic division I—one primary spermatocyte forms two Meiotic division I—one primary spermatocyte forms two secondary spermatocytes, each with 23 chromosomessecondary spermatocytes, each with 23 chromosomes

• Meiotic division II—each of the two secondary Meiotic division II—each of the two secondary spermatocytes form a total of four spermatidsspermatocytes form a total of four spermatids



Production of sex cells (cont.)Production of sex cells (cont.)

Oogenesis (Figure 33-4)—process by which primitive Oogenesis (Figure 33-4)—process by which primitive female sex cells become transformed into mature ovafemale sex cells become transformed into mature ova

• Mitosis—oogonia reproduce to form primary oocytes; most Mitosis—oogonia reproduce to form primary oocytes; most primary oocytes begin meiosis and develop to prophase primary oocytes begin meiosis and develop to prophase I before birth; there they stay until pubertyI before birth; there they stay until puberty

• Once during each menstrual cycle, a few primary oocytes Once during each menstrual cycle, a few primary oocytes resume meiosis and migrate toward the surface of the ovary; resume meiosis and migrate toward the surface of the ovary; usually only one oocyte matures enough for ovulation, and usually only one oocyte matures enough for ovulation, and meiosis again halts at metaphase IImeiosis again halts at metaphase II

• Meiosis resumes only if the head of a sperm cell enters Meiosis resumes only if the head of a sperm cell enters the ovumthe ovum



Ovulation and inseminationOvulation and insemination

Ovulation—expulsion of the mature ovum from the Ovulation—expulsion of the mature ovum from the mature ovarian follicle, into the abdominopelvic mature ovarian follicle, into the abdominopelvic cavity, and then the uterine (fallopian) tubecavity, and then the uterine (fallopian) tube

Insemination—expulsion of seminal fluid from Insemination—expulsion of seminal fluid from male into the female vagina; sperm travel through male into the female vagina; sperm travel through cervix and uterus and into uterine (fallopian) tubescervix and uterus and into uterine (fallopian) tubes



Fertilization—also known as conception (Figure 33-5)Fertilization—also known as conception (Figure 33-5) Most often occurs in the outer one third of oviductMost often occurs in the outer one third of oviduct

Ovum attracts and “traps” sperm with special receptor Ovum attracts and “traps” sperm with special receptor molecules on its surfacemolecules on its surface

When one spermatozoon enters ovum, ovum stops collecting When one spermatozoon enters ovum, ovum stops collecting sperm on its surfacesperm on its surface

The sperm releases its nuclear chromosomes into the ovum; The sperm releases its nuclear chromosomes into the ovum; proteins and RNA from the sperm enter the ovum to assist with proteins and RNA from the sperm enter the ovum to assist with early developmentearly development

23 chromosomes from the sperm head and 23 chromosomes in 23 chromosomes from the sperm head and 23 chromosomes in the ovum comprise a total of 46 chromosomesthe ovum comprise a total of 46 chromosomes

Zygote—fertilized ovum; genetically completeZygote—fertilized ovum; genetically complete


Prenatal PeriodPrenatal Period Begins with conception and continues until the birth of a childBegins with conception and continues until the birth of a child Cleavage and implantation (Figure 33-6)—once zygote is formed, it Cleavage and implantation (Figure 33-6)—once zygote is formed, it

immediately begins to divideimmediately begins to divide Morula—solid mass of cells formed from zygote; takes approximately 3 Morula—solid mass of cells formed from zygote; takes approximately 3

days; continues to divide (Figure 33-7)days; continues to divide (Figure 33-7) Blastocyst—by the time developing embryo reaches uterus, it has Blastocyst—by the time developing embryo reaches uterus, it has

formed a hollow ball of cells, which implants into uterine lining (Figure formed a hollow ball of cells, which implants into uterine lining (Figure 33-8)33-8)

Approximately 10 days pass from fertilization until implantation in Approximately 10 days pass from fertilization until implantation in uterine lining; ovum has a store of nutrients that support this embryonic uterine lining; ovum has a store of nutrients that support this embryonic development until implantation has occurreddevelopment until implantation has occurred

Blastocyst has an outer layer of cells and an inner cell massBlastocyst has an outer layer of cells and an inner cell mass• Trophoblast—outer wall of blastocystTrophoblast—outer wall of blastocyst• Inner cell mass—as blastocyst develops, yolk sac and amniotic cavity are Inner cell mass—as blastocyst develops, yolk sac and amniotic cavity are

formed (Figure 33-9)formed (Figure 33-9) In humans, yolk sac’s functions are largely nonnutritiveIn humans, yolk sac’s functions are largely nonnutritive Amniotic cavity becomes a fluid-filled, shock-absorbing sac (bag of waters) in Amniotic cavity becomes a fluid-filled, shock-absorbing sac (bag of waters) in

which embryo floats during development (Figure 33-10)which embryo floats during development (Figure 33-10)

• Chorion develops from trophoblast to become an important fetal membrane Chorion develops from trophoblast to become an important fetal membrane in the placentain the placenta


Prenatal PeriodPrenatal Period

Cleavage and implantation (cont.)Cleavage and implantation (cont.)

Placenta (Figure 33-11)Placenta (Figure 33-11)

• Anchors fetus to uterus and provides “bridge” for exchange Anchors fetus to uterus and provides “bridge” for exchange of nutrients and waste products between mother and babyof nutrients and waste products between mother and baby

• Also serves as excretory, respiratory, and endocrine organAlso serves as excretory, respiratory, and endocrine organ

• Placental tissue normally separates maternal and fetal Placental tissue normally separates maternal and fetal blood suppliesblood supplies

• Has important endocrine functions—secretes large Has important endocrine functions—secretes large amounts of human chorionic gonadotropin (HCG), which amounts of human chorionic gonadotropin (HCG), which stimulates the corpus luteum to continue its secretion of stimulates the corpus luteum to continue its secretion of estrogen and progesterone (Figure 33-12)estrogen and progesterone (Figure 33-12)


Prenatal PeriodPrenatal Period

Periods of development Periods of development (Figures 33-13 through 33-15)(Figures 33-13 through 33-15)

Gestation period—approximately 39 weeks; Gestation period—approximately 39 weeks; divided into three 3-month segments called divided into three 3-month segments called trimesterstrimesters

Embryonic phase extends from fertilization until Embryonic phase extends from fertilization until the end of week 8 of gestationthe end of week 8 of gestation

Fetal phase—weeks 8 to 39Fetal phase—weeks 8 to 39


Prenatal PeriodPrenatal Period Formation of the primary germ layersFormation of the primary germ layers

Three layers of specialized cells develop early in first Three layers of specialized cells develop early in first trimester of pregnancytrimester of pregnancy

Cells of embryonic disk differentiate and form each of Cells of embryonic disk differentiate and form each of the three primary germ layersthe three primary germ layers

Each primary germ layer gives rise to specific organs Each primary germ layer gives rise to specific organs and systems of the body (Figure 33-16)and systems of the body (Figure 33-16)

There are three primary germ layers:There are three primary germ layers:

• Endoderm—inside layerEndoderm—inside layer

• Ectoderm—outside layerEctoderm—outside layer

• Mesoderm—middle layerMesoderm—middle layer


Prenatal PeriodPrenatal Period Histogenesis and organogenesis (Figure 33-19)Histogenesis and organogenesis (Figure 33-19)

Histogenesis—process by which primary germ layers develop Histogenesis—process by which primary germ layers develop into different kinds of tissuesinto different kinds of tissues

Organogenesis—how tissues arrange themselves into organsOrganogenesis—how tissues arrange themselves into organs Differentiation and development of the reproductive systems Differentiation and development of the reproductive systems

are an exampleare an example

• Reproductive tract (Figure 33-17)Reproductive tract (Figure 33-17) Gonads attach to mesonephric (Wolffian) ducts, which become the male Gonads attach to mesonephric (Wolffian) ducts, which become the male

reproductive tractreproductive tract Gonads (unattached) and paramesonephric (Müllerian) ducts develop Gonads (unattached) and paramesonephric (Müllerian) ducts develop

into the female reproductive tractinto the female reproductive tract

• External genitals (Figure 33-18)External genitals (Figure 33-18) In the male, the genital tubercle eventually becomes the glans of the In the male, the genital tubercle eventually becomes the glans of the

penis and the folds become the penis shaft and scrotum penis and the folds become the penis shaft and scrotum In the female, the genital tubercle becomes the clitoris and the folds In the female, the genital tubercle becomes the clitoris and the folds

become the labiabecome the labia


Birth, or ParturitionBirth, or Parturition

Transition between prenatal and postnatal Transition between prenatal and postnatal periods of lifeperiods of life

Stages of labor (Figure 33-20)Stages of labor (Figure 33-20)

Stage one—period from onset of uterine Stage one—period from onset of uterine contractions until cervical dilation is completecontractions until cervical dilation is complete

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

Stage three—process of expulsion of the placenta Stage three—process of expulsion of the placenta through the vaginathrough the vagina


Birth, or ParturitionBirth, or Parturition

Multiple births—birth of two or more infants Multiple births—birth of two or more infants from the same pregnancy; twins are most from the same pregnancy; twins are most common (Figure 33-21)common (Figure 33-21)

Identical twins result from the splitting of embryonic Identical twins result from the splitting of embryonic tissue from the same zygote early in developmenttissue from the same zygote early in development

Fraternal twins result from the fertilization of two Fraternal twins result from the fertilization of two different ova by two different spermatozoadifferent ova by two different spermatozoa


Postnatal PeriodPostnatal Period

Begins at birth and continues until death; Begins at birth and continues until death; commonly divided into a number of periods commonly divided into a number of periods (Figure 33-22)(Figure 33-22)

Infancy begins at birth and lasts until Infancy begins at birth and lasts until approximately 18 monthsapproximately 18 months

Neonatal period—first 4 weeks of infancy; dramatic Neonatal period—first 4 weeks of infancy; dramatic changes occur at a rapid rate (Figure 33-23)changes occur at a rapid rate (Figure 33-23)

Changes allow the infant to become totally Changes allow the infant to become totally self-supporting, especially respiratory and self-supporting, especially respiratory and cardiovascular systems (Figure 33-24)cardiovascular systems (Figure 33-24)


Postnatal PeriodPostnatal Period Childhood extends from end of infancy to sexual Childhood extends from end of infancy to sexual

maturity, or pubertymaturity, or puberty Early childhood—growth continues at a rapid pace but Early childhood—growth continues at a rapid pace but

slows downslows down By age 6, child looks more like a preadolescent than an By age 6, child looks more like a preadolescent than an

infant or toddlerinfant or toddler Nervous and muscular systems develop rapidly during Nervous and muscular systems develop rapidly during

middle years of childhoodmiddle years of childhood Deciduous teeth are lost during childhood, beginning at Deciduous teeth are lost during childhood, beginning at

approximately 6 years of ageapproximately 6 years of age Permanent teeth have erupted by age 14, except for third Permanent teeth have erupted by age 14, except for third

molars (wisdom teeth)molars (wisdom teeth)


Postnatal PeriodPostnatal Period Adolescence and adulthoodAdolescence and adulthood

Adolescence is considered to be the teenage years (from 13 to Adolescence is considered to be the teenage years (from 13 to 19); marked by rapid and intense physical growth, resulting in 19); marked by rapid and intense physical growth, resulting in sexual maturitysexual maturity

• Puberty—stage of adolescence during which a person becomes Puberty—stage of adolescence during which a person becomes sexually maturesexually mature

• Changes triggered by increases in reproductive hormones (Figure Changes triggered by increases in reproductive hormones (Figure 33-25)33-25)

• Primary sexual characteristics—maturity of gonads and reproductive Primary sexual characteristics—maturity of gonads and reproductive tracttract

• Secondary sexual characteristics—fat and hair distribution, skeletal Secondary sexual characteristics—fat and hair distribution, skeletal changes, etc. (Figure 33-26)changes, etc. (Figure 33-26)

Adulthood—characterized by maintenance of existing body Adulthood—characterized by maintenance of existing body tissuestissues


Postnatal PeriodPostnatal Period

Older adulthood and senescenceOlder adulthood and senescence As a person grows older, a gradual decline occurs in As a person grows older, a gradual decline occurs in

every major organ system in the bodyevery major organ system in the body

Gerontologists theorize a number of different aging Gerontologists theorize a number of different aging mechanisms, all of which may be involved in the mechanisms, all of which may be involved in the processes of aging:processes of aging:

• Limit on cell reproduction Limit on cell reproduction

• Environmental factors Environmental factors

• VirusesViruses

• Aging genesAging genes

• Degeneration of mitochondria—perhaps progressive damage by Degeneration of mitochondria—perhaps progressive damage by oxygen free-radicals (Figure 33-27)oxygen free-radicals (Figure 33-27)


Effects of Aging—Common Degenerative Effects of Aging—Common Degenerative Changes That Frequently Characterize Changes That Frequently Characterize

Senescence (Figure 33-28)Senescence (Figure 33-28)

Skeletal system (Figure 33-29)Skeletal system (Figure 33-29)

Bones decrease in bone mineral density (BMD ) and Bones decrease in bone mineral density (BMD ) and thus change in texture, degree of calcification, and thus change in texture, degree of calcification, and shapeshape

Lipping occurs, which can limit range of motionLipping occurs, which can limit range of motion

Decreased bone size and density lead to increased Decreased bone size and density lead to increased risk of fracturerisk of fracture

Decreased BMD can be avoided (at least partly) by Decreased BMD can be avoided (at least partly) by exercise and adequate calcium intakeexercise and adequate calcium intake




Muscular system (Figure 33-30)Muscular system (Figure 33-30)

Muscle mass decreases to about 90% by age 50 Muscle mass decreases to about 90% by age 50 and around 50% by age 80and around 50% by age 80

The number of muscle fibers decreases as The number of muscle fibers decreases as humans age but can be offset by an increase in humans age but can be offset by an increase in muscle fiber size through exercisemuscle fiber size through exercise

Ratio of “fast” to “slow” functioning in muscle fibers Ratio of “fast” to “slow” functioning in muscle fibers decreases, slowing the function of muscle organsdecreases, slowing the function of muscle organs




Integumentary system (skin)Integumentary system (skin)

Skin becomes dry, thin, and inelasticSkin becomes dry, thin, and inelastic

Pigmentation changes and thinning hair are Pigmentation changes and thinning hair are common problems associated with agingcommon problems associated with aging




Urinary systemUrinary system

Number of nephron units in the kidney decreases Number of nephron units in the kidney decreases by almost 50% between the ages of 30 and 75by almost 50% between the ages of 30 and 75

Decreased blood flow through kidneys reduces Decreased blood flow through kidneys reduces overall function and excretory capacityoverall function and excretory capacity

Diminished muscle tone in bladder results in Diminished muscle tone in bladder results in decreased capacity and inability to empty, or void, decreased capacity and inability to empty, or void, completelycompletely




Respiratory systemRespiratory system

Costal cartilages become calcifiedCostal cartilages become calcified

Respiratory efficiency decreasesRespiratory efficiency decreases

Decreased strength of respiratory musclesDecreased strength of respiratory muscles




Cardiovascular systemCardiovascular system

Degenerative heart and blood vessel disease—one Degenerative heart and blood vessel disease—one of the most common and serious effects of agingof the most common and serious effects of aging

Atherosclerosis—build-up of fatty deposits on blood Atherosclerosis—build-up of fatty deposits on blood vessel walls narrows the passageway for bloodvessel walls narrows the passageway for blood

Arteriosclerosis—“hardening” of the arteriesArteriosclerosis—“hardening” of the arteries

Hypertension—high blood pressureHypertension—high blood pressure




Special sensesSpecial senses

Sense organs—gradual decline in performance and Sense organs—gradual decline in performance and capacity with agingcapacity with aging

Presbyopia—far-sightedness due to hardening of lensPresbyopia—far-sightedness due to hardening of lens

Cataract—cloudy lens, which impairs visionCataract—cloudy lens, which impairs vision

Glaucoma—increased pressure within the eyeball; if Glaucoma—increased pressure within the eyeball; if left untreated, often results in blindnessleft untreated, often results in blindness

Decreased hearingDecreased hearing

Decreased tasteDecreased taste




Reproductive systemsReproductive systems

Mechanism of sexual response may changeMechanism of sexual response may change

Fertility decreasesFertility decreases

In females, menopause occurs between ages of 45 In females, menopause occurs between ages of 45 and 60and 60


Causes of DeathCauses of Death

In developed countries such as the United In developed countries such as the United States, heart disease, cancer, and stroke States, heart disease, cancer, and stroke (CVA) are among the leading causes of death (CVA) are among the leading causes of death (Figure 33-31)(Figure 33-31)

In developing countries, heart disease and In developing countries, heart disease and stroke are also leading causes of death, stroke are also leading causes of death, along with infectious diseases such as along with infectious diseases such as HIV/AIDS, diarrheal disorders, and malariaHIV/AIDS, diarrheal disorders, and malaria

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