Download The Growth and Development of the Respiratory, Cardiovascular

Growth & Development of the
Respiratory & Cardiovascular Systems
Be able to describe the four stages of development of the
respiratory system
Lung Growth
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Alveolar development
– last trimester, most postnatally,
– 20 million at birth,
– 300 million at 8 (adult)
Fetal respiratory movements
Lung weight:
– 60-70gm at birth
– increasing 20 fold to adulthood,
– correlates best with height
Spirometry
Be able to describe the development
of the heart
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Endocardial tubes form,
that eventually coalesce to
form the primitive heart
tube at 3 weeks
Heart beats soon after
Nearby angiogenic cells
(mesodermal) form in
clusters (blood pools) and
migrate to form endothelial
lining of blood vessels
Adjacent mesenchymal
cells migrate around
endothelial lining to form
vessel wall
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6th week - heart
has developed its
general definitive
form
8th week - blood
vessels are formed
Heart tube folds
and twists forming
four distinct
chambers
Fetal Circulation
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Placenta
One umbilical vein - placenta to
fetus
Two umbilical arteries - fetus to
placenta
Foramen Ovale
Ductus Arteriosus
Result 10-15% of fetal blood goes
through lungs
Ductus Venosus
Be able to describe the fetal and
postnatal circulatory systems and
the transitions that occur at birth
Fetal Circulation
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Umbilical vein - Oxygen saturation = 70%
Fetal Periphery - Oxygen saturation = 55%
After birth
– Arterial = 97%
– Venous = 70%
fetal hemoglobin -greater affinity for Oxygen
Birth Adjustments
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Lungs expand, pulmonary vascular resistance
decreases and systemic blood pressure rises
Left atrial pressure rises - foramen ovale
closes
Ductus Arteriosus flows in opposite direction
until vasoconstriction and eventual closure
Heart Size
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Left side grows faster after birth
Heart growth curve same as weight (fat free mass)
40 ml at birth, 600 - 800 ml as adult
– doubles by 6 months,
– quadruples by 2 years,
Heart Rate,
Stroke
Volume
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Heart rate: 140 bts/min (sd = 20) at birth
Stroke Volume:
– 3-4 ml at birth, 40 ml just before growth spurt, 60 ml as adult
Cardiac Output:
– 0.5 l/min at birth, 5 l/min as adult
Blood
Pressure
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Reduction in pulmonary resistance, increase in
peripheral resistance
Systemic BP rises as Heart Rate drops
Blood Composition
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BloodVolume:
Highly correlated with heart
size and body weight, and
maximum oxygen uptake
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Hematocrit:
–
Adult
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30% at 2 months of
age,
– sex difference
established at puberty
Red blood cell count and
hemoglobin concentration
similar pattern
–
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males 40-45%,
females 38-42%
Thermoregulation
HEAT BALANCE &
TEMPERATURE REGULATION
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METABOLISM:
CHEMICAL REACTIONS: HEAT & ENERGY
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HEAT LOSS:
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RADIATION, CONDUCTION, CONV ECT ION
EVAPORATION (skin & lungs)
WARMING INSPIRED Al R
URINE & FAECES
CONTROL:
–
–
–
H Y P OT H A LAM U S
PERIPHERAL RECEPTORS
Comparison of core and peripheral temperatures
70%
27%
2%
1%
CONTROL IN NEWBORNS
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Mechanisms of shivering & sweating are poorly developed
Sweat glands immature
Large S.A./ Wt ratio
Thin subcutaneous adipose tissue layer
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LEADS TO INSTABILITY OF BODY TEMPERATURE
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Average body temperature drops with age
SD also drops, indicating better control
CONTROL IN NEWBORNS
 Vasoconstriction
well developed
 Crying increases metabolic rate
 Restlessness & increased
movements
 Brown fat
Vulnerability of the Adolescent Athlete
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There have been several deaths of
adolescent athletes
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Intense prolonged activity
High ambient temperature & humidity
Athletic equipment
Big (small S.A. /Weight ratio)
Lack of water
HEAT STROKE
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Sweating (Sweat is hypotonic)
Water leaves cells to hypertonic exterior
Water leaves blood, decrease in blood volume
High concentration of electrolytes in blood
Excessive water loss, sweating is shut-off
Temperature rises rapidly (>40ºC)
Heart failure