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CHAPTER 23:
PREGNANCY, GROWTH,
AND DEVELOPMENT
BIO 139
ANATOMY AND PHYSIOLOGY II
MARY CATHERINE FLATH, Ph.D.
Copyright 2010 Dr. Mary Cat Flath
FERTILIZATION


Fertilization is the fusion of genetic
material from the sperm and ovum
into a single nucleus
Occurs in fallopian tube
 Sperm becomes capacitated
 Secondary oocyte surrounded by
zona pellucida and corona
radiata
Copyright 2010 Dr. Mary Cat Flath
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Path of
sperm cells
Fig. 23.1
Body of uterus
Ovary
Infundibulum
Path of egg cell
Egg cell
Sperm cells
Cervix
Vagina
Semen deposited in vagina
during sexual intercourse
Copyright 2010 Dr. Mary Cat Flath
Steps in Fertilization
• sperm cell reaches corona radiata of oocyte
• acrosome releases enzymes to digest corona
radiata
• one sperm cell penetrates zona pellucida
(syngamy)
Copyright 2010 Dr. Mary Cat Flath
23-4
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Corona radiata
First polar body
Fig. 23.3
Second meiotic
spindle
Cytoplasm of secondary
oocyte
Zona pellucidav
Cell membrane
of secondary
oocyte
Acrosome
containing
enzymes
Nucleus
containing
chromosomes
3
1
4
5
2
Copyright 2010 Dr. Mary Cat Flath
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 23.3a
Corona radiata
First polar body
Second meiotic
spindle
Cytoplasm of secondary
oocyte
Zona pellucidav
Cell membrane
of secondary
oocyte
Copyright 2010 Dr. Mary Cat Flath
Fertilization

Once the sperm has penetrated the secondary
oocyte:
 Meiosis II occurs forming female pronucleus
 23 chromosomes
 Sperm’s flagellum is shed forming male
pronucleus
 23 chromosomes
 Pronuclei fuse forming segmentation
nucleus
 23 pairs of chromosomes
 ZYGOTE = segmentation nucleus and
cytoplasm surrounded by the zona pellucida
Copyright 2010 Dr. Mary Cat Flath
Copyright 2010 Dr. Mary Cat Flath
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Acrosome Fig. 23.3b
containing
enzymes
Nucleus
containing
chromosomes
3
1
4
5
2
Copyright 2010 Dr. Mary Cat Flath
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 23.2
From M. Tegner and D. Epel. 16 February 1973. "Sea Urchin Sperm." Science, 179:685-688. © 1973 American Association for the
Advancement of Science
Copyright 2010 Dr. Mary Cat Flath
Formation of the Morula

CLEAVAGE






Early mitotic divisions of the zygote
Occur rapidly so growth of cells does not
take place between divisions
Mass of cells, blastomeres, are held within
the zona pellucida
First division = 36 hours = 2 cells
Second division = 48 hours = 4 cells
MORULA

Solid ball of 32 cells; about 4 days
Copyright 2010 Dr. Mary Cat Flath
Copyright 2010 Dr. Mary Cat Flath
Copyright 2010 Dr. Mary Cat Flath
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 23.4
(a)
(b)
(c)
a: © A. Tsiara/Photo Researchers, Inc.; b: © Omikron/Photo Researchers, Inc.; c: © Petit Format/Nestle/Photo Researchers, Inc.
Copyright 2010 Dr. Mary Cat Flath
Formation of Blastocyst

Blastocyst is a hollow ball of cells
surrounding a central cavity; 5 days

Trophoblast



Inner cell mass (ICM)



Outer covering of the blastocyst, beneath zona
pellucida
Will become chorion, fetal portion of placenta
Cells concentrated in one portion of cavity
Will become the embryonic body
Blastocoel

Fluid-filled cavity
Copyright 2010 Dr. Mary Cat Flath
Copyright 2010 Dr. Mary Cat Flath
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Sperm
nucleus
Egg
nucleus
Polar
bodies
Zona pellucida
Cleavages (first cleavage completed about 30 hours after fertilization)
Stem cells
EaEarly Human DevelopmentrlyEarly Human Development Human Development
Day 0
Pronucleus
formation
begins
Zygote First cleavage division
Day 1
2-cell stage
Day 2
4-cell stage
Day 3
Early morula
Day 4
Late morula
Stem cells
Fertilization
occurs about
12-24 hours
after ovulation
Day 6-7
Blastocyst
implantation
Endometrium
Ovulation
Uterus
Copyright 2010 Dr. Mary Cat Flath
Implantation



The zona pellucida surrounding the
blastocyst disintegrates while in
uterine cavity (Day 5)
At about day 6, implantation
occurs.
The blastocyst adheres to the
endometrial wall through the ICM.
Copyright 2010 Dr. Mary Cat Flath
Implantation

The trophoblast forms two layers
 Cytotrophoblast


Boundary cells
Syncytiotrophoblast


Closest to endometrium
Invades endometrium (decidua basalis) by
secretion of digestive enzymes
 Endometrial cells nourish burrowing embryo
for one more week
 Decidua capsularis is the portion of the
endometrium that surrounds the burrowed
blastocyst.
Copyright 2010 Dr. Mary Cat Flath
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Trophoblast
Fig. 23.6a
Blastocyst
Inner cell
mass
Uterine
wall
(a)
Copyright 2010 Dr. Mary Cat Flath
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 23.6b
Invading
trophoblast
(b)
Copyright 2010 Dr. Mary Cat Flath
Copyright 2010 Dr. Mary Cat Flath
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Trophoblast
Blastocyst
Trophoblast
Fig. 23.6
Inner cell
mass
Inner cell mass
Uterine
wall
(a)
(c)
Invading
trophoblast
(b)
c: Courtesy of Ronan O'Rahilly, M.D. Carnegie Institute of Washington
Copyright 2010 Dr. Mary Cat Flath
Endometrium
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Lumen
Fig. 23.7
Endometrium
Copyright 2010 Dr. Mary Cat Flath
Courtesy of Ronan O'Rahilly, M.D. Carnegie Institute of Washington
Summary of Stages and
Events of Early Human
Prenatal Development
• fertilized ovum
• 12-24 hours after
ovulation
• zygote forms
• cleavage
• 30 hours to third day
• mitosis increases cell
number
• morula
• third to fourth day
• solid ball of cells
• blastocyst
• fifth day through
second week
• trophoblast and inner
cell mass form
• gastrula
• end of second week
• primary germ layers
form
Copyright 2010 Dr. Mary Cat Flath
23-8
Let’s shift to what’s
happening during pregnancy.
HORMONES
MATERNAL CHANGES
Copyright 2010 Dr. Mary Cat Flath
HORMONES OF
PREGNANCY







ESTROGENS AND PROGESTERONES
HUMAN CHORIONIC
GONADOTROPIN
HUMAN PLACENTAL LACTOGEN
RELAXIN
INHIBIN
ALDOSTERONE
PARATHYROID
HORMONE
Copyright 2010 Dr. Mary Cat Flath
HORMONES OF
PREGNANCY

ESTROGENS AND PROGESTERONES

From corpus luteum through month 3


Relatively low levels to maintain uterine lining
during pregnancy
From chorion of placenta from month
3 through birth





Extremely high levels to maintain pregnancy
Develop mammary glands for lactation
Inhibit secretion of FSH and LH
Inhibit uterine contractions
Enlarge reproductive organs
Copyright 2010 Dr. Mary Cat Flath
HORMONES OF
PREGNANCY
hCG
 HUMAN CHORIONIC
GONADOTROPIN is secreted from the



chorion of the placenta
Stimulates the corpus luteum’s continued
secretion of estrogens and progesterones
Can be detected by day 8, peaks at week 9,
decreases sharply during month 4-5
May cause “morning sickness”
Copyright 2010 Dr. Mary Cat Flath
Hormonal Changes During
Pregnancy
Mechanism that preserves uterine lining during early pregnancy
Copyright 2010 Dr. Mary Cat Flath
23-9
Hormonal Changes During
Pregnancy
Relative concentrations of three hormones in maternal
blood during pregnancy
Copyright 2010 Dr. Mary Cat Flath
23-10
HORMONES OF
PREGNANCY

HUMAN PLACENTAL LACTOGEN
(hPL)



Secretion starts about day 8
Levels increase as placenta enlarges
and peak at week 32
Effects include:



Breast development for lactation
Protein deposition in tissues
Regulation of metabolism
Copyright 2010 Dr. Mary Cat Flath
HORMONES OF
PREGNANCY

RELAXIN




Secreted by corpus luteum of ovary
Relaxes symphysis pubis and pelvic
ligaments
Dilates uterine cervix
INHIBIN


Secreted by ovaries
Inhibits secretion of FSH
Copyright 2010 Dr. Mary Cat Flath
HORMONES OF
PREGNANCY

ALDOSTERONE



Secreted by adrenal cortex
Promotes sodium and fluid retention
PARATHYROID HORMONE


Maintains high calcium
concentrations in maternal blood
Fetal demand may cause
hypocalcemia

Leading to cramping
Copyright 2010 Dr. Mary Cat Flath
GESTATION



The length of time that the zygote,
embryo and fetus is carried in the
female reproductive tract
About 266 days
Obstetrics is the special branch of
medicine that deals with this
period
Copyright 2010 Dr. Mary Cat Flath
PREGNANCY:
Anatomical changes


Fetus occupies pelvic cavity by end
of month 3
At full term, fetus occupies most of
abdominal cavity



Diaphragm pushed upward by liver,
intestine and stomach
Thoracic cavity is widened
Ureters and bladder are compressed
Copyright 2010 Dr. Mary Cat Flath
PREGNANCY:
Physiological Changes







General
Cardiovascular changes
Pulmonary changes
GI changes
Urinary Changes
Skin changes
Reproductive Changes
Copyright 2010 Dr. Mary Cat Flath
PREGNANCY:
Physiological Changes

General
 Weight gain
 Fetus, amniotic fluid, placenta, uterus,
water
 Increased storage of proteins, Triglycerides,
and minerals
 Breast enlargement
 Preparation for lactation
 Lower back pain
 lordosis
Copyright 2010 Dr. Mary Cat Flath
PREGNANCY:
Physiological Changes

Cardiovascular changes
 Increased SV and CO
 30%
 Increased HR
 10-15%
 Increased BV
 30-50%
 Compression of IVC decreases venous
return
 edema
Copyright 2010 Dr. Mary Cat Flath
PREGNANCY:
Physiological Changes

Pulmonary changes
 TV and ERV increased
 30- 40%
 Functional residual capacity
decreased
 To 25%
 Total oxygen consumption increased
 10-20%
Copyright 2010 Dr. Mary Cat Flath
PREGNANCY:
Physiological Changes

GI changes
 Appetite increased
 Motility decreased
 constipation
 Nausea, vomiting, heartburn may
result
Copyright 2010 Dr. Mary Cat Flath
PREGNANCY:
Physiological Changes

Urinary Changes
 Increased frequency and urgency
 Incontinence may result
 Increased GFR
 30-50%
Copyright 2010 Dr. Mary Cat Flath
PREGNANCY:
Physiological Changes

Skin changes
 Increased pigmentation
 Blotches may occur
 Dermis of abdomen is stretched
 Striae may result
Copyright 2010 Dr. Mary Cat Flath
PREGNANCY:
Physiological Changes

Reproductive Changes
 Increased vascularity
 Vulva and vagina swell
 Uterus hypertrophy
 From 60-80 g to 900-1200g

15x original weight
Copyright 2010 Dr. Mary Cat Flath
Let’s shift back to what’s
happening with embryonic
development
Copyright 2010 Dr. Mary Cat Flath
EMBRYONIC
DEVELOPMENT




Considered first 8-10 weeks
gestation
Embryo = to grow
Rudiments of all principle adult
organs are present by 8th week
Embryonic membranes have
formed
Copyright 2010 Dr. Mary Cat Flath
EMBRYONIC DEVELOPMENT:
GASTRULATION


Three germ layers develop within
inner cell mass of the blastocyst
(now a gastrula)
These germ layers will give rise to
all adult organs/organ systems



Ectoderm
Endoderm
Mesoderm
Copyright 2010 Dr. Mary Cat Flath
EMBRYONIC DEVELOPMENT:
GASTRULATION


About day 8, the ICM cells form the
amnion and the amniotic cavity
The Ectoderm is the outer most
layer (closest to amniotic cavity)
 Gives rise to epidermis and
 Nervous tissue
Copyright 2010 Dr. Mary Cat Flath
EMBRYONIC DEVELOPMENT:
GASTRULATION


At about day 8, the endoderm is formed
(ICM cells that border blastocoel)
The endoderm is the innermost germ
layer
 Gives rise to mucous membranes
The endoderm and ectoderm are called
the embryonic disc
Copyright 2010 Dr. Mary Cat Flath
EMBRYONIC DEVELOPMENT:
GASTRULATION

At about day 12
 The endoderm forms the yolk sac
 A third layer called the mesoderm
develops
 The mesoderm is the middle germ
layer
 Gives rise to muscles, bones, and
many internal organs
Copyright 2010 Dr. Mary Cat Flath
Development of the Three Germ Layers: Gastrulation
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 23.10
Lumen of
uterus
Endometrium
Chorion
Extraembryonic cavity
Amnion
Ectoderm
Germ layers of
Mesoderm
embryonic disc
Endoderm
Amniotic cavity
Connecting stalk
Chorionic villi
Yolk sac
of embryo
Copyright 2010 Dr. Mary Cat Flath
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Neural tube
(Spinal cord)
Skin
Tail end
Amnion
Fig. 23.11
Chorionic villi
Amniotic
fluid
Connecting stalk
Digestive
tract
Heart
Yolk sac
Chorion
Allantois
Brain
Endoderm
Ectoderm
MesodermDr. Mary Cat Flath
Copyright 2010
EMBRYONIC MEMBRANES




Yolk Sac
 Nourishment and early blood cell formation
 Becomes non-functional part of umbilical cord
Amnion
 Encases embryo
 Cavity is filled with amniotic fluid
 Protection
 Helps regulated fetal body temperature
Chorion
 From trophoblast of blastocyst
 Embryonic/fetal portion of placenta
Allantois
 Early blood cell formation
 Its blood vessels will form connections with placenta
as umbilical cord
Copyright 2010 Dr. Mary Cat Flath
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Chorion
Umbilical
cord
Allantois
Amnion
Maternal
blood
vessels
Fig. 23.15
Developing
placenta
Amniotic cavity
Yolk
sac
Extraembryonic
cavity
Endometrium
Copyright 2010 Dr. Mary Cat Flath
Embryos (page 889)
• three weeks; dorsal view
• three and a half weeks; lateral view
• four weeks; lateral view
Copyright 2010 Dr. Mary Cat Flath
23-14
Embryonic Development
Copyright 2010 Dr. Mary Cat Flath
23-15
Changes During
Embryonic Development
Copyright 2010 Dr. Mary Cat Flath
23-16
DEVELOPMENT OF
PLACENTA
COMPLETE BY THIRD MONTH
OF PREGNANCY
Copyright 2010 Dr. Mary Cat Flath
ANATOMY OF PLACENTA


SHAPED LIKE FLAT CAKE WHEN
MATURE
EMBRYONIC/FETAL PORTION IS
CHORION



CHORIONIC VILLI (CONTAINING FETAL
BLOOD VESSELS FROM ALLANTOIS) EXTEND
INTO INTERVILLOUS SPACES (MATERNAL
BLOOD SINUSES)
EXCHANGE SITE for GASES AND NUTRIENTS
AND WASTES
MATERNAL PORTION IS DECIDUA
BASALIS
Copyright 2010 Dr. Mary Cat Flath
PHYSIOLOGY OF
PLACENTA

MAINTAINS FETUS




PROTECTS FETUS


OXYGEN AND NUTRIENTS DIFFUSE FROM MATERNAL
BLOOD INTO FETAL BLOOD
CO2 AND WASTES DIFFUSE FROM FETAL BLOOD TO
MATERNAL BLOOD
NEARLY ALL DRUGS PASS THROUGH PLACENTA
BARRIER AGAINST MOST MICROORGANISMS
 PERMEABLE TO SOME VIRUSES
 HIV, MEASLES, GERMAN MEASLES, CHCKEN
POX, ENCEPHALITIS, POLIOMYELITIS
MAINTAINS PREGANACY

THROUGH SECRETION OF HORMONES
Copyright 2010 Dr. Mary Cat Flath
Copyright 2010 Dr. Mary Cat Flath
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Amniochorionic membrane
Amniotic fluid
Fig. 23.18
Umbilical cord
Chorion
Endometrium Myometrium
Copyright 2010 Dr. Mary Cat Flath
Placenta
UMBILICAL CORD

VASCULAR CONNECTION BETWEEN
MOTHER AND FETUS

ONE UMBILICAL VEIN


TWO UMBILICAL ARTERIES



OXYGEN AND NUTRIENTS TOWARD FETUS
CO2 AND WASTES AWAY FROM FETUS
COMPLETELY SURROUNDED BY LAYER
OF AMNION
SEVERED AT DELIVERY

REMNANT IS NAVEL
Copyright 2010 Dr. Mary Cat Flath
Copyright 2010 Dr. Mary Cat Flath
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Umbilical cord
Umbilical arteries
Fig. 23.17
Umbilical vein
Chorion
Embryonic
blood vessels
Lacuna
Villi
(embryonic portion
of placenta)
Myometrium
Decidua basalis
(maternal portion
of placenta)
Maternal
blood vessels
Copyright 2010 Dr. Mary Cat Flath
Embryo at Eight Weeks
End of eighth week marks end of embryonic period
Copyright 2010 Dr. Mary Cat Flath
23-21
Teratogens
• factors that cause congenital malformations during
embryonic development
Drugs, viruses, radiation, large amounts of
normal substances (fat- soluble vitamins)
•Structures in developing embryo are sensitive to
teratogens at different times
• Each structure has time called “critical period”
• Neural Tube defects are traced to day 28 in
development
•Interruption results in spina bifida or anecephaly
Copyright 2010 Dr. Mary Cat Flath
23-22
Teratogens
In acne medications
Prescribed to prevent miscarriages
Prescribed to alleviate
morning sickness
Copyright 2010 Dr. Mary Cat Flath
Development
body proportions change considerably
Copyright 2010 Dr. Mary Cat Flath
23-23
Development of the Genitalia
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Genital tubercle
Urogenital fold
Genital tubercle
Urogenital folds
Embryonic tail
Labioscrotal folds
Fig. 23.22
(a)
Glans
Urogenital fold
Urethral groove
Labioscrotal fold
Male
Female
(b)
Developing penis
Developing clitoris
Urethral groove
Labia minora
Fused urogenital folds
Labia majora
Perineum
Anus
(c)
Glans penis
(e)
Prepuce
Glans clitoris
Urethral orifice
Hymen
Scrotum
Vaginal
orifice
Perineum
Anus
(d)
(f)
Copyright 2010 Dr. Mary Cat Flath
Position of Full-Term Fetus
Copyright 2010 Dr. Mary Cat Flath
23-25
Major Events of
Fetal Development
9th –12th week
• ossification centers appear
• sex organs differentiate
• nerves and muscles coordinate so fetal
limbs begin to move
• length is four inches; weight is one ounce
13th – 16th week
• body grows rapidly
• ossification continues
• length is eight inches; weight is six ounces
Copyright 2010 Dr. Mary Cat Flath
23-26
Major Events of
Fetal Development
17th – 20th week
• muscle movements stronger
• skin is covered with fine downy hair (lanugo)
• length is 12 inches; weight is one pound
• skin is covered sebum mixed with dead epidermal cells
vernix caseosa
21st – 38th week
• body gains weight (to 6-10 pounds; 21 inches in
length
• subcutaneous fat deposited
• eyebrows and eyelashes appear
• eyelids open
23-27
Copyright 2010 Dr. Mary Cat Flath
• testes descend
Fetal Circulation
• oxygen and nutrients
diffuse into the
fetal blood from
the maternal
blood
• waste diffuses into the
maternal blood
from the fetal
blood
Copyright 2010 Dr. Mary Cat Flath
23-28
Fetal Cardiovascular
Adaptations
• fetal blood has greater oxygen-carrying capacity
• umbilical vein carries oxygenated blood from placenta to
fetus
• ductus venosus conducts half the blood from umbilical vein to
inferior vena cava; liver is bypassed
• foramen ovale conveys blood from right atrium to left
atrium; lungs are bypassed
• ductus arteriosis conducts some blood from pulmonary trunk
to aorta; lungs are bypassed
• umbilical arteries carry blood from internal iliac arteries to
placenta
Copyright 2010 Dr. Mary Cat Flath
23-29
Fetal Circulation
Copyright 2010 Dr. Mary Cat Flath
23-30
Copyright 2010 Dr. Mary Cat Flath
Copyright 2010 Dr. Mary Cat Flath
Factors Contributing to the
Labor Process
• as birth approaches, progesterone levels decrease
• prostaglandins synthesized which may initiate labor
• stretching uterine tissue stimulates release of oxytocin
• oxytocin stimulates uterine contractions
• fetal head stretches uterus
• positive feedback results in stronger and stronger
contractions and greater release of oxytocin
Copyright 2010 Dr. Mary Cat Flath
23-32
Birth Process
A positive feedback mechanism propels the birth process
Copyright 2010 Dr. Mary Cat Flath
23-33
Stages in Birth
• dilation stage
• expulsion stage
• placental stage
Copyright 2010 Dr. Mary Cat Flath
23-34
“Fight or flight” for
Newborn


Hypoxia results from fetal head
compression
High levels of epinephrine and
norepinephrine are secreted which
allow infant to survive extra-uterine life
 Lungs are cleared for breathing
 Nutrients are mobilized for
metabolism
 Blood is rushed to brain and heart
Copyright 2010 Dr. Mary Cat Flath
Post-Natal
Circulatory Changes
Copyright 2010 Dr. Mary Cat Flath
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Aorta
Ductus arteriosus
constricts and
becomes solid
ligamentum
arteriosum
Foramen ovale
closes and becomes
fossa ovalis
Fig. 23.32
Ductus venosus
constricts and
becomes solid
ligamentum
venosum
Deoxygenated
blood
Liver
Oxygenated
blood
Umbilical
vein becomes
solid
ligamentum
teres
Inferior vena cava
Distal portions
of umbilical
arteries constrict
and become
medial umbilical
ligaments
Proximal portions of
umbilical arteries persist
Copyright 2010 Dr. Mary Cat Flath
as superior vesical arteries
Postnatal Period
Neonatal period
• birth to end of 4th week
• newborn begins to carry on respiration, obtain
nutrients, digest nutrients, excrete wastes, regulate body
temperature, and make cardiovascular adjustments
Infancy
• end of 4th week to one year
• growth rate is high
• teeth begin to erupt
• muscular and nervous systems mature
• communication begins
Copyright 2010 Dr. Mary Cat Flath
23-38
Postnatal Period
Adolescence
Childhood
• puberty to adulthood
• one year to puberty
• person becomes
• growth rate is high
reproductively functional
• permanent teeth appear
and emotionally more
• muscular control is
mature
achieved
• growth spurts occur
• bladder and bowel
• motor skills continue to
controls are established
develop
• intellectual abilities
• intellectual abilities
mature
continue to mature
Copyright 2010 Dr. Mary Cat Flath
23-39
Postnatal Period
Adulthood
• adolescence to old age
• person remains
relatively unchanged
anatomically and
physiologically
• degenerative changes
begin
Senescence
• old age to death
• degenerative changes
continue
• body becomes less able to
cope with demands placed
on it
• death results from
various conditions and
diseases
Copyright 2010 Dr. Mary Cat Flath
23-40
Copyright 2010 Dr. Mary Cat Flath
Copyright 2010 Dr. Mary Cat Flath
Causes of Death
Copyright 2010 Dr. Mary Cat Flath
23-43
Clinical Application
Preimplantation Genetic Diagnosis
Probes diseasecausing genes in
an eight-celled
embryo
Copyright 2010 Dr. Mary Cat Flath
23-44
Copyright 2010 Dr. Mary Cat Flath