Transcript Human Growth and Development

Day #6
3/29/11
Fort Omaha
Human
Growth
and
Development
Agenda
• Finish Genetics
• Prenatal development DVD
• Prenatal development notes (you may have to
go over some of these on your own)
• Assignment
Genotype and Phenotype
• Genotype -- all of a person’s genetic
material
• Phenotype -- observable characteristics
• Phenotypes include
– physical characteristics (such as height,
weight, and hair color)
– psychological characteristics (such as
personality and intelligence)
Genetic Principles
• Dominant-recessive genes
• Sex-linked genes
• Polygenically determined characteristics
Dominant-Recessive Genes Principle
• Dominant -- one gene of a pair always
exerts its effects
• Recessive gene – exerts its influence only
if the two genes of a pair are both
recessive
– may be overridden by a dominant gene
– May be carried from generation to
generation but not expressed in phenotype
Sex-Linked Genes
• X-linked inheritance -- mutated gene is carried
on the X chromosome
– very different implications for males than females
(Turner, 2006)
– males have no “backup” copy to counter the
harmful gene
– females have a second X chromosome, which is
likely to be unchanged
• Females who have one changed copy of the X gene are
known as “carriers”
Polygenic Inheritance
• Genetic transmission is usually quite
complex
– Few characteristics reflect the influence of
only a single gene or pair of genes
• polygenically determined characteristics - determined by the interaction of many
different genes
Chromosome Abnormalities
• Down syndrome -- caused by the
presence of an extra copy of
chromosome 21
– once in every 700 live births
– Women aged 16 - 34 are less likely to give
birth to a child with Down syndrome
• Sex-Linked Chromosome Abnormalities
Sex-Linked Chromosome
Abnormalities
• Klinefelter syndrome – extra X
chromosome
• Fragile X syndrome -- results from an
abnormality in the X chromosome
– X chromosome becomes constricted and
often breaks
• Turner syndrome -- females have either
an X chromosome missing or part of one
X chromosome is deleted
• XYY syndrome – male has extra Y
Gene-Linked Abnormalities
• Phenylketonuria (PKU) – individual
cannot properly metabolize
phenylalanine, an amino acid
– once in every 10,000 to 20,000 live births
– left untreated, phenylalanine builds up in
the child, producing mental retardation and
hyperactivity
• Sickle-cell anemia -- genetic disorder that
impairs the body’s red blood cells
– most often in African Americans
– red blood cell becomes a hook-shaped
“sickle” that cannot carry oxygen properly
– 1 in 400 African American babies is affected
• 1 in 10 African Americans is a carrier
• 1 in 20 Latin Americans is a carrier
• Other diseases that result from genetic
abnormalities
– cystic fibrosis
– diabetes
– hemophilia
– Huntington disease
– spina bifida
– Tay-Sachs disease
DVD: The biology of prenatal
development
PRENATAL DEVELOPMENT AND
BIRTH
The Fetal Period
• Fetal period begins two months after
conception and lasts for seven months
• Three months after conception-- fetus is about
3 inches long; weighs about 3 ounces
• At birth, the average American baby weighs 7
½ pounds and is about 20 inches long
Three Trimesters
• The germinal and embryonic periods occur in
the first trimester
• The fetal period begins toward the end of the
first trimester and continues through the
second and third trimesters
• Viability (the chances of surviving outside the
womb) occurs at the beginning of the third
trimester.
• Age of viability – about 23-24 weeks on
average
Amillia Taylor
http://abcnews.go.com/Health/story?id=2
890242&page=1
• Amillia Sonja Taylor, born Oct. 24, 2006 after
just under 22 weeks in the womb, will spend a
few extra days in a Florida hospital as a
precaution. Amillia, now a relatively robust 4½
pounds, was 9½ inches long and weighed 10
ounces at birth. (Baptist Hospital via The
Miami Herald/AP Photo) (2007)
2/21/2007
• Amillia Taylor now weighs 17
pounds and measures 27 1/2
inches long. Her favorite foods
are watermelon and bananas,
and she has begun self-feeding
and loves to laugh, play, and
interact with her family
members.
• Despite the emotional ups and
downs of the year since Amillia's
birth, Taylor knows she would do
it all over again if given a choice.
http://www.iparenting.com/mom/5458.php
http://www.youtube.com/watch?v=fejTulMNaPM
• October 2008
• Amillia is also taking
steps in their
Homestead home
and sounding out her
few words and
developmentally
progressing very
well.
• 26 pounds
26 ½ inches tall
Prenatal Tests
• Ultrasound sonography
– non-invasive
– high-frequency sound waves
• Chorionic villi sampling
– tiny tissue sample from the placenta is removed and analyzed
• Amnocentesis
– sample of amniotic fluid is withdrawn by syringe and tested for
chromosome or metabolic disorders
• Maternal blood screening
– identifies pregnancies that have an elevated risk for birth defects
(Bromage, 2006).
Teratogens
• Despite complexity, most babies are born
healthy
• Most hazards are avoidable
• Teratology—study of birth defects
– teratogens—broad range of substances that
can cause environmental insults that may
cause prenatal abnormalities or later
learning abilities
Timing of Exposure
• Critical period—in prenatal
development, the time when a
particular organ or other body
part is most susceptible to
teratogenic damage
-entire embryonic period is
critical
Amount of Exposure
• Dose and/or frequency
• Threshold effect—teratogen relatively
harmless until exposure reaches a
certain level
Amount of Exposure, cont.
• Interaction effect—risk of
harm increases if exposure to
teratogen occurs at the same
time as exposure to another
teratogen or risk
The Birth Process
• The Birth Process
– first stage -- contractions cause the woman’s
cervix to stretch and open
• longest of the three stages
• typically lasts 12 to 24 hours
– second stage begins when the baby’s head starts
to move through the cervix
– 45 minutes – 1 ½ hours, depending on number of
pregnancies
– third stage is afterbirth
• placenta, umbilical cord, and other membranes are
detached and expelled
• shortest of the three birth stages
Where and Who?
• Where do births take place?
– In U.S., 99% take place in hospitals
– Home births are far more common in many other
countries
• Who assists?
–
–
–
–
Obstetricians and nurses
Fathers or birth coaches
Midwives
Doula -- a caregiver who provides continuous physical,
emotional, and educational support for the mother
before, during, and after childbirth
Methods of Childbirth
• Medications
– Three basic kinds of drugs
• Analgesia
• Anesthesia
• Oxytocics
• Natural and Prepared Childbirth
– Natural childbirth – reduce pain the breathing
techniques and relaxation
– Prepared childbirth – a.k.a. Lamaze
Cesarean Delivery
• Breech position – buttocks rather than head
emerge first
– Can prevent the baby from breathing normally
• Cesarean delivery -- the baby is removed from
the mother’s uterus through an incision made
in her abdomen
– May be lifesaving but carry the risks of major
surgery
From Fetus to Newborn
• Anoxia -- fetus or newborn has an insufficient
supply of oxygen
– Cause of brain damage
• Immediately after birth, the umbilical cord is
cut and the baby is on its own
• Almost immediately after birth, a newborn is
taken to be weighed, cleaned up, and tested
Apgar Scale
• Used to assess the health of newborns at 1
and 5 minutes after birth
• A score, or reading, of 0, 1, or 2 on each of
these five health signs
– heart rate, respiratory effort, muscle tone, body
color, and reflex irritability
• identifies high-risk infants who need resuscitation.
Apgar Scoring
• Activity (muscle tone)
0 — Limp; no movement
1 — Some flexion of arms and legs
2 — Active motion
• Pulse (heart rate)
0 — No heart rate
1 — Fewer than 100 beats per minute
2 — At least 100 beats per minute
• http://www.babycenter.com/0_the-apgar-score_3074.bc
• Grimace (reflex response)
0 — No response to airways being suctioned
1 — Grimace during suctioning
2 — Grimace and pull away, cough,
or sneeze during suctioning
• Appearance (color)
0 — The baby's whole body is completely bluish-gray or pale
1 — Good color in body with bluish hands or feet
2 — Good color all over
• Respiration (breathing)
0 — Not breathing
1 — Weak cry; may sound like whimpering, slow or irregular
breathing
2 — Good, strong cry; normal rate and effort of breathing
Threats to Newborns
• Low birth weight
• LBW -- less than 5 ½ pounds at birth
• Very low birth weight - under 3 pounds
• Extremely low birth weight - under 2 pounds.
• Preterm
• born three weeks or more before the pregnancy has reached its
full term
• Small-for-date
• birth weight is below normal when the length of the
pregnancy is considered
Incidences and Causes of Low Birth
Weight
• Low birth weight and preterm births often
occur together
• Incidence of low birth weight varies
considerably from country to country
– Related to
• Poverty
• Maternal health status
• Maternal nutrition
Consequences of Low Birth Weight
• More health and developmental problems
than normal-weight infants (Moss, 2006).
• At school age, more likely to have a learning
disability, attention deficit hyperactivity
disorder, or breathing problems such as
asthma (Wocadlo & Rieger, 2006).
Interventions for Low Birth
Weight/Preterm Infants
• Kangaroo care -- a way of holding an infant so
that there is skin-to-skin contact for two to
three hours per day over an extended time in
early infancy (Feldman & others, 2003)
• Massage therapy -- firm stroking with the
palms of the hands three times per day for 15minute periods (Field & others, 1986)
Bonding
• Bonding -- formation of a connection,
especially a physical bond, between parents
and the newborn in the period shortly after
birth
• Bonding is inhibited by
– Anesthesia during labor
– Hospital policies that separate mothers from
infants
The Postpartum Period
• Postpartum period -- lasts for about six weeks
after childbirth or delivery or until the
mother’s body has completed its adjustment
and has returned to a nearly prepregnant
state
• Physical and psychological adjustments
Physical Adjustments
• Fatigue can undermine the new mother’s
sense of well-being and confidence in her
ability to cope with a new baby
• Dramatic changes in hormone production
• Involution -- process by which the uterus
returns to its pre-pregnant size
Emotional and Psychological
Adjustments
• Baby blues -- two to three days after birth,
many women begin to feel depressed,
anxious, and upset
• Postpartum depression -- a major depressive
episode about four weeks after delivery
– strong feelings of sadness, anxiety, or despair that
for at least a two-week period inhibit coping with
daily tasks
Treatments for Postpartum Issues
• Without professional treatment, postpartum
depression may become worse and last for
many months
(Driscoll, 2006)
• Parents should set aside some special time to
be together
• Father’s postpartum reaction also likely will be
improved if he has taken childbirth classes
with the mother and is an active participant in
caring for the baby
Assignment
• Test s MUST be submitted at class time on
Tuesday, April 5!!! You will transcribe answers
to the answer sheet at the
beginning of class! Be here
on time, please!
• Begin infancy –
the nervous system
• http://www.quia.com/files/quia/users/jcarterf
auchier/gabrielle