© 2012 pearson education, inc. an introduction to development and inheritance development gradual...

© 2012 Pearson Education, Inc.

An Introduction to Development and Inheritance

• Development

• Gradual modification of anatomical structures and physiological characteristics from fertilization to maturity

• Inheritance

• Transfer of genetic material from generation to generation


29-1 Development

• Differentiation

• Creation of different types of cells required in

development

• Occurs through selective changes in genetic activity

• As development proceeds, some genes are turned off,

others are turned on

• Fertilization

• Also called conception

• When development begins


29-1 Development

• Embryological Development

• Occurs during first two months after fertilization

• Study of these events is called embryology

• Fetal Development

• Begins at start of ninth week

• Continues until birth


29-1 Development

• Prenatal Development

• Embryological and fetal development stages

• Postnatal Development

• Commences at birth

• Continues to maturity, the state of full development

or completed growth


29-1 Development

• Inheritance

• Transfer of genetically determined characteristics

from generation to generation

• Genetics

• Study of mechanisms responsible for inheritance


29-2 Fertilization

• Fertilization

• Fusion of two haploid gametes, each containing 23 chromosomes

• Produces zygote containing 46 chromosomes

• Spermatozoon

• Delivers paternal chromosomes to fertilization site

• Travels relatively large distance

• Is small, efficient, and highly streamlined


29-2 Fertilization

• Gamete

• Provides:

• Cellular organelles

• Inclusions

• Nourishment

• Genetic programming necessary to support development of embryo for a week


29-2 Fertilization

• Fertilization

• Occurs in uterine tube within a day after ovulation

• Secondary oocyte travels a few centimeters

• Spermatozoa must cover distance between vagina and ampulla

• Capacitation

• Must occur before spermatozoa can fertilize secondary oocyte

• Contact with secretions of seminal glands

• Exposure to conditions in female reproductive tract


29-2 Fertilization

• Acrosomes

• Release hyaluronidase and acrosin, enzymes

• Penetrate corona radiata, zona pellucida, toward

oocyte surface

• Oocyte Activation

• Contact and fusion of cell membranes of sperm and

oocyte

• Follows fertilization

• Oocyte completes meiosis II, becomes mature ovum


29-2 Fertilization

• Polyspermy

• Fertilization by more than one sperm

• Prevented by cortical reaction

• Cortical Reaction

• Releases enzymes that:

• Inactivate sperm receptors

• Harden zona pellucida


29-2 Fertilization

• Female Pronucleus

• Nuclear material remaining in ovum after oocyte activation

• Male Pronucleus

• Swollen nucleus of spermatozoon

• Migrates to center of cell


29-2 Fertilization

• Amphimixis

• Fusion of female pronucleus and male pronucleus

• Moment of conception

• Cell becomes a zygote with 46 chromosomes

• Fertilization is complete


29-2 Fertilization

• Cleavage

• Series of cell divisions

• Produces daughter cells

• Differentiation

• Involves changes in genetic activity of some cells but not others


Figure 29-1a Fertilization

A secondary oocyte andnumerous sperm at the time offertilization. Notice thedifference in size between thegametes.


Figure 29-1b Fertilization

Ovulation releases a secondaryoocyte and the first polar body;both are surrounded by the coronaradiata. The oocyte is suspended inmetaphase of meiosis II.

Coronaradiata

First polarbody

Zonapellucida

Oocyte at Ovulation



Acrosomal enzymes from multiplesperm create gaps in the coronaradiata. A single sperm then makescontact with the oocyte membrane,and membrane fusion occurs,triggering oocyte activation andcompletion of meiosis.

Fertilizingspermatozoon

Second polarbody

Fertilization and OocyteActivation



Pronucleus FormationBegins

The sperm is absorbed intothe cytoplasm, and the femalepronucleus develops.

Nucleus offertilizing

spermatozoon

Femalepronucleus



Spindle Formation andCleavage PreparationThe male pronucleusdevelops, and spindle fibersappear in preparation for thefirst cleavage division.

Femalepronucleus

Malepronucleus



Amphimixis Occurs andCleavage Begins

Metaphase of firstcleavage division



The first cleavage divisionnears completion roughly30 hours after fertilization.

Cleavage Begins

Blastomeres


29-3 Gestation

• Induction

• Cells release chemical substances that affect

differentiation of other embryonic cells

• Can control highly complex processes

• Gestation

• Time spent in prenatal development

• Consists of three integrated trimesters, each three

months long


29-3 Gestation

1. First Trimester

• Period of embryological and early fetal development

• Rudiments of all major organ systems appear

2. Second Trimester

• Development of organs and organ systems

• Body shape and proportions change

3. Third Trimester

• Rapid fetal growth and deposition of adipose tissue

• Most major organ systems are fully functional


29-4 The First Trimester

• First Trimester

• Includes four major stages

1. Cleavage

2. Implantation

3. Placentation

4. Embryogenesis



• Cleavage

• Sequence of cell divisions begins immediately after fertilization

• Zygote becomes a pre-embryo, which develops into multicellular blastocyst

• Ends when blastocyst contacts uterine wall

• Implantation

• Begins with attachment of blastocyst to endometrium of uterus

• Sets stage for formation of vital embryonic structures



• Placentation

• Occurs as blood vessels form around periphery of

blastocyst and placenta develops

• Embryogenesis

• Formation of viable embryo

• Establishes foundations for all major organ systems



• The First Trimester

• Most dangerous period in prenatal life

• 40% of conceptions produce embryos that survive

past first trimester



• Cleavage and Blastocyst Formation

• Blastomeres

• Identical cells produced by cleavage divisions

• Morula

• Stage after three days of cleavage

• Pre-embryo is solid ball of cells resembling mulberry

• Reaches uterus on day 4




• Blastocyst

• Formed by blastomeres

• Hollow ball with an inner cavity

• Known as blastocoele




• Trophoblast

• Outer layer of cells separate outside world from

blastocoele

• Cells responsible for providing nutrients to

developing embryo




• Inner cell mass

• Clustered at end of blastocyst

• Exposed to blastocoele

• Insulated from contact with outside environment by

trophoblast

• Will later form embryo


Figure 29-2 Cleavage and Blastocyst Formation

Polar bodies

2-cell stage

DAY 1 DAY 2

4-cell stage

Blastomeres

DAY 0:

First cleavagedivision

Fertilization


Figure 29-2 Cleavage and Blastocyst Formation

Early morula

DAY 3DAY 4

DAY 6

Advancedmorula

Hatching

Inner cellmass

Blastocoele

Trophoblast

Blastocyst

Days 7–10:Implantation in

uterine wall(See Figure 29–3)



• Implantation

• Occurs (begins) seven days after fertilization

• Blastocyst adheres to uterine lining

• Trophoblast cells divide rapidly, creating several

layers



• Implantation

• Cellular trophoblast

• Cells closest to interior of blastocyst

• Syncytial trophoblast

• Outer layer

• Erodes path through uterine epithelium by secreting

hyaluronidase


Figure 29-3 Stages in Implantation

DAY 6 FUNCTIONAL ZONEOF ENDOMETRIUM

DAY 7

UTERINECAVITY

Uterineglands

Blastocyst

Trophoblast

BlastocoeleInner cellmass


Figure 29-3 Stages in Implantation

DAY 8

Syncytialtrophoblast

Cellulartrophoblast

AmnioticcavityLacuna

Developingvilli

DAY 9



• Ectopic Pregnancy

• Implantation occurs outside uterus

• Does not produce viable embryo

• Can be life threatening

• Lacunae

• Trophoblastic channels carrying maternal blood



• Formation of the Amniotic Cavity

• Villi extend away from trophoblast into endometrium

• Increase in size and complexity until day 21

• Amniotic Cavity

• A fluid-filled chamber

• Inner cell mass is organized into an oval sheet two layers thick

• Superficial layer faces amniotic cavity

• Deeper layer is exposed to fluid contents of blastocoele



• Gastrulation and Germ Layer Formation

• Formation of third layer of cells

• Cells in specific areas of surface move toward central

line

• Known as primitive streak



• Primitive Streak

• Migrating cells leave surface and move between two

layers

• Creates three distinct embryonic layers, or germ layers

1. Ectoderm: consists of the superficial cells that did not

migrate into interior of inner cell mass

2. Endoderm: consists of cells that face blastocoele

3. Mesoderm: consists of poorly organized layer of

migrating cells between ectoderm and endoderm



• Ectodermal Contributions

• Integumentary system:

• Epidermis, hair follicles and hairs, nails, and glands communicating with the skin (sweat glands, mammary glands, and sebaceous glands)

• Skeletal system:

• Pharyngeal cartilages and their derivatives in adults (portion of sphenoid, the auditory ossicles, the styloid processes of the temporal bones, the cornu and superior rim of the hyoid bone)*

• Nervous system:

• All neural tissue, including brain and spinal cord



• Ectodermal Contributions

• Endocrine system:

• Pituitary gland and adrenal medullae

• Respiratory system:

• Mucous epithelium of nasal passageways

• Digestive system:

• Mucous epithelium of mouth and anus, salivary glands



• Mesodermal Contributions

• Integumentary system:

• Dermis and hypodermis

• Skeletal system:

• All components except some pharyngeal derivatives

• Muscular system:

• All components



• Mesodermal Contributions


• Adrenal cortex, endocrine tissues of heart, kidneys, and gonads

• Cardiovascular system:

• All components



• Mesodermal Contributions• Lymphatic system:

• All components

• Urinary system:

• The kidneys, including the nephrons and the initial portions of the collecting system

• Reproductive system:

• The gonads and the adjacent portions of the duct systems

• Miscellaneous:

• The lining of the body cavities (pleural, pericardial, and peritoneal) and the connective tissues that support all organ systems



• Endodermal Contributions


• Thymus, thyroid gland, and pancreas

• Respiratory system: • Respiratory epithelium (except nasal passageways) and

associated mucous glands

• Digestive system:

• Mucous epithelium (except mouth and anus), exocrine glands (except salivary glands), liver, and pancreas



• Endodermal Contributions

• Urinary system: • Urinary bladder and distal portions of the duct system

• Reproductive system: • Distal portions of the duct system, stem cells that

produce gametes



• Embryonic Disc

• Oval, three-layered sheet

• Produced by gastrulation

• Will form body of embryo

• Rest of blastocyst will be involved in forming

extraembryonic membranes


Figure 29-4 The Inner Cell Mass and Gastrulation

Superficial layer

Deep layer

Day 10: Yolk Sac Formation

Lacunae

Blastocoele

Yolk sac

Amniotic cavity

Cellular trophoblast

Syncytial trophoblast


Figure 29-4 The Inner Cell Mass and Gastrulation

Day 12: Gastrulation

Amnion

Ectoderm

Primitivestreak

Blastodisc

Yolk sac

Mesoderm

Endoderm

Embryonic disc



• Formation of the Extraembryonic Membranes

• Support embryological and fetal development

• Yolk sac

• Amnion

• Allantois

• Chorion



• The Yolk Sac

• Begins as layer of cells spread out around outer edges

of blastocoele to form complete pouch

• Important site of blood cell formation



• The Amnion

• Combination of mesoderm and ectoderm

• Ectodermal layer enlarges and cells spread over inner surface of amniotic cavity

• Mesodermal cells create outer layer

• Continues to enlarge through development

• Amniotic fluid

• Surrounds and cushions developing embryo or fetus



• The Allantois

• Sac of endoderm and mesoderm

• Base later gives rise to urinary bladder

• The Chorion

• Combination of mesoderm and trophoblast

• Blood vessels develop within mesoderm

• Rapid-transit system for nutrients that links embryo with trophoblast

• First step in creation of functional placenta



• Chorionic Villi

• In contact with maternal tissues

• Create intricate network within endometrium carrying

maternal blood


Figure 29-5 Extraembryonic Membranes and Placenta Formation

Migration of mesoderm around the inner surface of thetrophoblast creates the chorion. Mesodermal migrationaround the outside of the amniotic cavity, between theectodermal cells and the trophoblast, forms the amnion.Mesodermal migration around the endodermal pouchcreates the yolk sac.

Week 2

Amnion


Cellulartrophoblast

Mesoderm

Yolk sac

Blastocoele

Chorion



The embryonic disc bulges into the amniotic cavity at thehead fold. The allantois, an endodermal extensionsurrounded by mesoderm, extends toward the trophoblast.

Week 3

Amniotic cavity(containingamniotic fluid)

Allantois

Head foldof embryo


Chorion

Yolksac

Chorionic villiof placenta



Embryonichead fold

Embryonic gut

Yolk sac

Yolk stalk

Body stalk

Tail fold

The embryo now has a head fold and a tail fold. Constrictionof the connections between the embryo and the surroundingtrophoblast narrows the yolk stalk and body stalk.

Week 4



Week 5The developing embryo and extraembryonicmembranes bulge into the uterine cavity. Thetrophoblast pushing out into the uterine lumen remainscovered by endometrium but no longer participates innutrient absorption and embryo support. The embryomoves away from the placenta, and the body stalk andyolk stalk fuse to form an umbilical stalk.

Uterus

Myometrium

Chorionic villiof placenta

Umbilical stalk

Placenta

Yolk sac

Deciduacapsularis

Deciduaparietalis

Uterine lumen

Deciduabasalis



Deciduacapsularis

Week 10The amnion has expandedgreatly, filling the uterine cavity.The fetus is connected to theplacenta by an elongated umbilicalcord that contains a portion of theallantois, blood vessels, and theremnants of the yolk stalk.

Chorion

Amnion

Amniotic cavity

Placenta

Umbilical cord

Deciduaparietalis

Decidua basalis



• Placentation

• Body stalk

• Connection between embryo and chorion

• Contains distal portions of allantois and blood vessels

that carry blood to and from placenta

• Yolk stalk

• Narrow connection between endoderm of embryo and

yolk sac



• Decidua Capsularis

• Thin portion of endometrium

• No longer participates in nutrient exchange and chorionic villi in region disappear

• Decidua Basalis

• Disc-shaped area in deepest portion of endometrium

• Where placental functions are concentrated

• Decidua Parietalis

• Rest of the uterine endometrium

• No contact with chorion



• Umbilical Cord

• Connects fetus and placenta

• Contains allantois, placental blood vessels, and yolk

stalk

• Placental Circulation

• Through paired umbilical arteries

• Returns in single umbilical vein


Figure 29-6a A Three-Dimensional View of Placental Structure

Chorionicvilli

Umbilicalarteries

Umbilicalvein

Area filled withmaternal blood

Arrows in the enlarged view indicate the direction of blood flow.

Maternalblood vessels

Trophoblast (cellularand syncytial layers)

Amnion



• The Endocrine Placenta

• Synthesized by syncytial trophoblast, released into maternal bloodstream

• Human chorionic gonadotropin (hCG)

• Human placental lactogen (hPL)

• Placental prolactin

• Relaxin

• Progesterone

• Estrogens



• Human Chorionic Gonadotropin (hCG)

• Appears in maternal bloodstream soon after

implantation

• Provides reliable indication of pregnancy

• Pregnancy ends if absent



• Human Placental Lactogen (hPL)

• Human chorionic somatomammotropin (hCS)

• Prepares mammary glands for milk production

• Synergistic with growth hormone at other tissues

• Ensures adequate glucose and protein is available

for the fetus



• Placental Prolactin

• Helps convert mammary glands to active status

• Relaxin

• A peptide hormone secreted by placenta and corpus luteum during pregnancy

• Increases flexibility of pubic symphysis, permitting pelvis to expand during delivery

• Causes dilation of cervix

• Suppresses release of oxytocin by hypothalamus and delays labor contractions



• Embryogenesis

• Body of embryo begins to separate from embryonic disc

• Body of embryo and internal organs start to form

• Folding, differential growth of embryonic disc produces bulge that projects into amniotic cavity

• Projections are head fold and tail fold

• Organogenesis

• Process of organ formation


Figure 29-7a The First 12 Weeks of Development

Future headof embryo

Thickenedneural plate(will form brain)

Axis of futurespinal cord

Somites

Neural folds

Cut wall ofamniotic cavity

Future tailof embryo

Week 2. An SEM of the superior surface of a monkeyembryo at 2 weeks of development. A human embryoat this stage would look essentially the same.


Figure 29-7b The First 12 Weeks of Development

Tail

Bodystalk

Heart

Eye

Forebrain

Ear

Medullaoblongata

Week 4. Fiberoptic view of humandevelopment at week 4.

Leg bud

Arm bud

Somites

Pharyngealarches


Figure 29-7c The First 12 Weeks of Development

Umbilicalcord

Amnion


Placenta

Chorionicvilli


Figure 29-7d The First 12 Weeks of Development


Umbilicalcord

Amnion


29-5 The Second and Third Trimesters

• Second Trimester

• Fetus grows faster than surrounding placenta

• Third Trimester

• Most of the organ systems become ready

• Growth rate starts to slow

• Largest weight gain

• Fetus and enlarged uterus displace many of mother’s

abdominal organs


Figure 29-8a The Second and Third Trimesters

A four-month-old fetus, seen through a fiberoptic endoscope


Figure 29-8b The Second and Third Trimesters

Head of a six-month-old fetus, revealedthrough ultrasound


Figure 29-9a Growth of the Uterus and Fetus

Placenta

Umbilicalcord

Fetus at16 weeks

Uterus

Amniotic fluid

Cervix

Vagina

Pregnancy at 16 weeks, showing thepositions of the uterus, fetus, and placenta.


Figure 29-9b Growth of the Uterus and Fetus

After dropping,in preparationto delivery

Pregnancy at three months to nine months(full term), showing the superior-mostposition of the uterus within the abdomen.

9 months

8 months

7 months6 months5 months

4 months

3 months


Figure 29-9c Growth of the Uterus and FetusStomach

Transversecolon

Liver

Fundusof uterus

Small intestine

Pancreas

Aorta

Commoniliac vein

Cervical (mucus)plug in cervical canal

External os

Rectum

Urethra

VaginaPubic symphysis

Urinary bladder

Placenta

Umbilical cord

Pregnancy at full term. Note the positions of theuterus and full-term fetus within the abdomen,and the displacement of abdominal organs.


Figure 29-9d Growth of the Uterus and Fetus

A sectional view through theabdominopelvic cavity of a womanwho is not pregnant.



• Pregnancy and Maternal Systems

• Developing fetus is totally dependent on maternal organ systems for nourishment, respiration, and waste removal

• Maternal adaptations include increases in:

• Respiratory rate and tidal volume

• Blood volume

• Nutrient and vitamin intake

• Glomerular filtration rate

• Size of uterus and mammary glands



• Progesterone

• Released by placenta

• Has inhibitory effect on uterine smooth muscle

• Prevents extensive, powerful contractions

• Opposition to Progesterone

• Three major factors

1. Rising estrogen levels

2. Rising oxytocin levels

3. Prostaglandin production



• Structural and Functional Changes in the Uterus

• False labor

• Occasional spasms in uterine musculature

• Contractions not regular or persistent

• True labor

• Results from biochemical and mechanical factors

• Continues due to positive feedback

• Labor contractions

• Begin in myometrium


29-6 Labor

• Parturition

• Is forcible expulsion of fetus

• Contractions

• Begin near top of uterus, sweep in wave toward cervix

• Strong, occur at regular intervals, increase in force

and frequency

• Change position of fetus, move it toward cervical

canal


29-6 Labor

• Stages of Labor

1. Dilation stage

2. Expulsion stage

3. Placental stage


29-6 Labor

• Dilation Stage

• Begins with onset of true labor

• Cervix dilates

• Fetus begins to shift toward cervical canal

• Highly variable in length, but typically lasts over eight

hours

• Frequency of contractions steadily increases

• Amniochorionic membrane ruptures (water breaks)


Figure 29-11 The Stages of Labor

Fully developed fetus before labor begins

Placenta Umbilicalcord

Sacralpromontory

Cervicalcanal

Cervix Vagina

Pubicsymphysis



The Dilation Stage


29-6 Labor

• Expulsion Stage

• Begins as cervix completes dilation

• Contractions reach maximum intensity

• Continues until fetus has emerged from vagina

• Typically less than two hours

• Delivery

• Arrival of newborn infant into outside world


29-6 Labor

• Episiotomy

• Incision through perineal musculature

• Needed if vaginal canal is too small to pass fetus

• Repaired with sutures after delivery


29-6 Labor

• Cesarean Section (C-section)

• Removal of infant by incision made through

abdominal wall

• Opens uterus just enough to pass infant’s head

• Needed if complications arise during dilation or

expulsion stages



The Expulsion Stage


29-6 Labor

• Placental Stage

• Muscle tension builds in walls of partially empty uterus

• Tears connections between endometrium and placenta

• Ends within an hour of delivery with ejection of

placenta, or afterbirth

• Accompanied by a loss of blood



The Placental Stage

Uterus Ejection of theplacenta


29-6 Labor

• Premature Labor

• Occurs when true labor begins before fetus has

completed normal development

• Newborn’s chances of surviving are directly

related to body weight at delivery


29-6 Labor

• Immature Delivery

• Refers to fetuses born at 25–27 weeks of gestation

• Most die despite intensive neonatal care

• Survivors have high risk of developmental

abnormalities

• Premature Delivery

• Refers to birth at 28–36 weeks

• Newborns have a good chance of surviving and

developing normally


29-6 Labor

• Difficult Deliveries

• Forceps delivery

• Needed when fetus faces mother’s pubis instead of

sacrum

• Risks to infant and mother are reduced if forceps are

used

• Forceps resemble large, curved salad tongs

• Used to grasp head of fetus


29-6 Labor

• Difficult Deliveries

• Breech birth

• Legs or buttocks of fetus enter vaginal canal first instead

of head

• Umbilical cord can become constricted, cutting off

placental blood flow

• Cervix may not dilate enough to pass head

• Prolongs delivery

• Subjects fetus to severe distress and potential injury


29-6 Labor

• Multiple Births

• Dizygotic twins

• Also called “fraternal” twins

• Develop when two separate oocytes were ovulated and

subsequently fertilized

• Genetic makeup not identical

• 70% of twins


29-6 Labor

• Multiple Births

• Monozygotic twins

• Also called “identical” twins

• Result either from:

• Separation of blastomeres early in cleavage

• Splitting of inner cell mass before gastrulation

• Genetic makeup is identical because both formed from

same pair of gametes


29-6 Labor

• Multiple Births

• Conjoined twins

• Siamese twins

• Genetically identical twins

• Occurs when splitting of blastomeres or of

embryonic disc is not completed


29-6 Labor

• Rates of Multiple Births

• Twins in 1 of every 89 births

• Triplets in 1 of every 892 (7921) births

• Quadruplets in 1 of every 893 (704,969) births


29-7 Postnatal Life

• Five Life Stages

1. Neonatal period

2. Infancy

3. Childhood

4. Adolescence

5. Maturity


29-7 Postnatal Life

• Duration of Life Stages

• Neonatal Period: extends from birth to 1 month

• Infancy: 1 month to 2 years of age

• Childhood: 2 years until adolescence

• Adolescence: period of sexual and physical

maturation

• Senescence: process of aging that begins at end of

development (maturity)


29-7 Postnatal Life

• The Neonatal Period, Infancy, and Childhood

• Two major events occur

1. Organ systems become fully operational

2. Individual grows rapidly and body proportions change

significantly

• Pediatrics

• Medical specialty focusing on postnatal development

from infancy to adolescence


29-7 Postnatal Life

• The Neonatal Period

• Transition from fetus to neonate

• Neonate

• Newborn

• Systems begin functioning independently

• Respiratory

• Circulatory

• Digestive

• Urinary


29-7 Postnatal Life

• Lactation and the Mammary Glands

• Colostrum

• Secretion from mammary glands

• Ingested by infant during first two to three days

• Contains more proteins and less fat than breast milk

• Many proteins are antibodies that help ward off infections until immune system is functional

• Mucins present inhibit replication of rotaviruses

• As production drops, mammary glands convert to milk production


29-7 Postnatal Life

• Breast Milk

• Consists of water, proteins, amino acids, lipids,

sugars, and salts

• Also contains large quantities of lysozymes—enzymes

with antibiotic properties

• Milk let-down reflex

• Mammary gland secretion triggered when infant sucks

on nipple

• Continues to function until weaning, typically one to two

years


Figure 29-12 The Milk Let-Down Reflex

Milk Ejected

Stimulation of Tactile ReceptorsStart

Neural Impulse Transmission

Oxytocin Release

Posteriorlobe of thepituitarygland

Stimulation of HypothalamicNuclei


29-7 Postnatal Life

• Infancy and Childhood

• Growth occurs under direction of circulating hormones

• Growth hormone

• Adrenal steroids

• Thyroid hormones

• Growth does not occur uniformly

• Body proportions gradually change


Figure 29-13 Growth and Changes in Body Form and Proportion

Prenatal DevelopmentEmbryological Development Fetal Development

16 weeks

8 weeks

4 weeks


Figure 29-13 Growth and Changes in Body Form and Proportion

Postnatal Development

Neonatal Infancy Childhood Adolescence Maturity

1 month 2 years 18 yearsPuberty(between 9–14 years)


29-7 Postnatal Life

• Adolescence and Maturity

• Puberty is a period of sexual maturation and marks the beginning of adolescence

• Generally starts at age 12 in boys, age 11 in girls

• Three major hormonal events interact

1. Hypothalamus increases production of GnRH

2. Circulating levels of FSH and LH rise rapidly

3. Ovarian or testicular cells become more sensitive to FSH and LH

• Hormonal changes produce sex-specific differences in structure and function of many systems


29-7 Postnatal Life

• Adolescence

• Begins at puberty

• Continues until growth is completed

• Maturity (Senescence)

• Aging

• Reduces functional capabilities of individual

• Affects homeostatic mechanisms

• Sex hormone levels decline at menopause or male climacteric


29-7 Postnatal Life

• Geriatrics

• Medical specialty dealing with problems

associated with aging

• Trained physicians, or geriatricians


Figure 29-19 A Map of Human Chromosomes

Color Blindness (multiple forms) Chapter 17Fragile-X Syndrome Chapter 29

HemophiliaChapter 19

Neurofibromatosis, Type 2Tumors of the auditory nerves

and tissues surrounding the brainDown’s Syndrome

Chapter 29

Amyotrophic Lateral Sclerosis*Chapter 15

ADA DeficiencyAn enzyme deficiency that

affects the immune system

Familial HypercholesterolemiaExtremely high cholesterol

Myotonic DystrophyForm of muscular dystrophy in

which symptoms oftendevelop after puberty

AmyloidosisAccumulation of an insolublefibrillar protein in the tissues

Breast Cancer*Chapter 28

Polycystic Kidney DiseaseChapter 26

Tay–Sachs DiseaseLysosomal storage disease

affecting neural tissue

Marfan’s SyndromeChapter 6

Alzheimer’s Disease*Chapter 16

1-Antitrypsin DeficiencyCauses a predisposition to

develop emphysemaRetinoblastoma

A relatively common tumor of the eye,accounting for 2% of childhood malignancies

PKU(phenylketonuria)

Chapter 25

Muscular Dystrophy Chapter 10

Prostate Cancer Chapter 28

Gaucher’s DiseaseLysosomal storage disease causedby excess glycolipids in plasma membranes

Familial Colon Cancer*Chapter 24Retinitis Pigmentosa*Chapter 17Huntington’s Disease*Chapter 17Familial Polyposis of the ColonAbnormal tissue growths thatcommonly lead to colon cancer

Spinocerebellar AtaxiaDestroys neurons in the brainand spinal cord, resulting inloss of muscle control

Cystic FibrosisChapter 23

Burkitt’s LymphomaCancer of lymphocytes; atype of non-Hodgkin lymphoma

Retinitis Pigmentosa*Chapter 17Epilepsy, progressiveChapter 14

Malignant MelanomaChapter 5Ovarian CancerChapter 28

Multiple Endocrine Neoplasia, Type 2Tumors in endocrine glands andother tissuesSCID Chapter 22

Diabetes Mellitus, Type 1Chapter 18

Sickle Cell Anemia Chapter 19

* One form of the disease

CHROMOSOMEPAIRS

XY 1 2 34

5

6

7

89

1011121314

1516

1718

1920

2122

© 2012 pearson education, inc. an introduction to development and inheritance development gradual...

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