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Heart - Coronary Blood Flow
Anatomy of coronary arteries - shown in Fig 30-1 from BLT
The Fick equation: VO2 = A-VO2 diff x Q
For the myocardium: MVO2 = A-VO2 diff x CBF
When the body is at rest, A-VO2 diff very high about 16 ml O2 /100
ml blood
Therefore increases in MVO2 must occur by increases in CBF (Figure 30-5)
Coronary Circulation
Anatomy of coronaries - see Fig 30-1
Mechanical - ventricular compression - see F 30-3
autoregulation
Neural factors - F 30-7 and related text. Understand the importance of high intrinsic vasomotor tone
Metabolic - F 30-7 and related text - reactive and active hyperemia
B. Skeletal Muscle Flow
D. Cerebral Blood Flow
E. Renal Blood Flow
F. Skin Blood Flow
G. Fetal Circulation -see Fig 30-18.
Structures the are unique to fetal circulation
placenta - trophoblasts - alveolar-like extensions of the umbilical vein allow for exchange of O2, CO2 and nutrients between fetal and maternal circulations. At normal flow rates there is not complete equilibrium between the two circulations. Fetal Hb has a higher affinity for O2 - partially compensating for this problem.
ductus venosus - connects umbilical vein which is bringing blood from the placenta to the IVC near the liver.
foramen ovale - connects the right atrium to the left atrium
ductus arteriosus - connects the pulmonary artery to the aorta
crista dividens - directs SVC and IVC blood coming into RA to different outflow tracts.
Flow of Blood:
oxygenated blood (saturation ~ 80%) from the placenta comes to the fetus through the umbilical vein. About half of the this blood goes to the liver and the other half enters the IVC through the ductus venosus.
blood comes into the RA through the IVC and SVC as in adults but the IVC blood is much more oxygenated than that in the SVC. In the right atrium of the neonate heart the foramen ovale allows blood from the IVC to be shunted to the left atrium.
ventricles in the neonate heart are working in series rather than in parallel as in the adult. The lungs in the neonate are not responsible for oxygenating the blood and pulmonary vascular resistance is high.
most blood ejected by the right ventricle into the pulmonary artery flows from the PA through the ductus arteriosus into the aorta and becomes part of the descending aorta flow. Blood ejected by the left ventricle into the aorta supplies most of the blood for the head, upper thorax and arms.