Cardiovascular Development

• Postnatal Circulatory System

  • 2 closed circuits
  • pulmonary
  • systemic
  • arranged in series
  • pressure = L > R
• pulmonary circulatory system

  • right side
  • oxygenation
  • removal of CO2
• systemic circulatory system

  • left side
  • delivery system
  • transport waste from the body tissue to the liver and to the lungs
• systemic pressure is higher than pulmonary pressure
• 3 bypasses in fetal circulation

  1. ductus venosus
  2. foreamen ovale
  3. ductus arteriosus
• Fetal circulation

  • 2 open circuits
  • operate in parallel since there is an opening between the left and right side of the heart
  • pressure = R > L
• ductus venosus

  • joins with IVC; goes from umbilical vein to ductus venosus directly to IVC
  • bypasses the liver
  • relatively nonfunctional because the detoxification and filtering is also supported by mothers circulation
• placenta

  • oxygen exchange occurs at the placenta
  • the left side of the heart is connected to the placenta
  • low resistance for blood flow
• Foramen ovale

  • blood passing from the right side of the heart to the left side; blood goes from RA, foramen ovale directly to LA
  • bypass right ventricle
• ductus arteriosus

  • bypass the lungs because they are not functional; goes from pulmonary trunk directly, then ductus arteriosus to aorta
  • goes right through the aorta out to the body tissues then pulmonary trunk to the aorta
• key changes at birth

  • gas exchange
  • baby breathes for the first time
  • loss of umbilical cord means loss of placenta
  • drops in resistance of blood flow on the right side with the change in gas exchange
  • pressure differential
  • pressure on left side starts to rise
  • lungs and vasculature start to open up
• functional closure: organ shut down
• physiological changes: changes to the actual structure of the organ

  • takes months to a year
• postnatal remnants of fetal structures

  • fetal = postnatal
  • foramen ovale = fossa ovalis
  • ductus arteriosus = ligamentum arteriosum
  • ductus venosus = ligamentum venosum
  • umbilical arteries = medial umbilical ligaments
  • umbilical vein = ligamentum teres
• closures in the postnatal circulation

  • ligamentum arteriosum
  • ligamentum venosum
  • fossa ovalis
  • ligamentum teres
  • medial umbilical ligaments
• Site of oxygen exchange

  • fetal: placenta
  • postnatal: lungs
• circulations

  • fetal: parallel, open circuit
  • postnatal: series, closed circuits, separation of R & L sides
• shunts and bypasses

  • fetal: open
  • postnatal: closed
• oxygenation of blood in the heart

  • fetal:
  • right and left sides: mixing of deoxygenated and oxygenated blood
  • postnatal:
  • right side: deoxygenated
  • left side: oxygenated
• pressure

  • fetal: higher on right side
  • postnatal: higher on left side
• foramen ovale allows blood flow from the right atrium to the left atrium
• @2 weeks in the womb, the heart starts as 2 tubes that fuse together
• @4 weeks the 2 tubes fuse together to become the tubular heart
• segments of the tubular heart

  • truncus arteriosus
  • bulbus cordis
  • ventricle
  • atrium
  • sinus venosus
• the truncus arteriosus develops into:

  • aorta
  • pulmonary trunk
• the sinus venosus develops into:

  • right atrium
  • SA node
  • coronary sinus
• the bulbus cordis develops into:

  • right ventricle
• the primitive atrium develops into:

  • right atrium
  • left atrium
  • right and left auricles
• the primitive ventricle develops into:

  • left ventricle
• 2 divisions of truncus arteriosus

  1. bulbar ridges
  2. aorticopulmonary (spiral) septum
• bulbar ridges grow together to form a septum
• aorticopulmonary (sprial) septum form lateral ridges of the truncus arteriosus

  • as it grows, it will spiral 180º degrees when it fully forms
• the aorticopulmonary (spiral) septum develops into and separates the aorta from the pulmonary trunk

  • the pulmonary trunk is infront of the ascending aorta
  • orientation results because of the spiral of the septum
• the aorticopulmonary septum cuts across the truncus arteriosus to split into the aorta and pulmonary trunk
• how to differentiate the aorta from the pulmonary trunk

  the aorta has 2 coronary arteries located towards the base of the aorta
• Persistent truncus arteriosus

  • aorticopulmonary septum fails to develop
  • if septum fails to develop, oxygen and deoxygenated blood mix from the atria and ventricles
  • desaturated blood moving into the body tissues
  • infant will present as cyanotic because they will not have sufficient oxygen in their body tissues
• valve stenosis

  • due to unequal partitioning
  • a result of deviation of the articopulmonary septum:
  • one side expanded
  • one side stenosed
  • one vessel bigger than the other
  • smaller vessel can have a small valve, valve stenosis
  • increase in pressure and difficulty in blood moving through the vessels
• Stenosis

  • Factor: obstruction or shunt
  • Effect: obstruction
• stenosis

  • factor: effect on blood flow
  • effect:
  • obstructed ventricular flow
  • reduced flow into pulmonary artery (trunk)
• stenosis

  • factor: volume or pressure load
  • effect: pressure load - more resistance and pressure on right side of heart