Superior vena cava
Inferior vena cava
Hepatic portal vein
(becomes fossa ovalis)
Left renal artery
Common iliac artery
Internal iliac artery
The general pattern of fetal circulation is shown anatomically.
condition is often associated with other cardiovascular, uro-
genital, or gastrointestinal disorders. The vessels within the
severed cord are routinely counted following a birth because
of the possibility of these conditions.
summarizes the major features of fetal cir-
culation. At the time of birth, important adjustments must
occur in the cardiovascular system when the placenta ceases
to function and the newborn begins to breathe. Clinical
Application 23.2 describes a case in which fetal ultrasound
revealed two hearts and bloodstreams, yet a single body.
Which umbilical vessel carries oxygenated blood to the fetus?
What is the function of the ductus venosus?
What characteristic of fetal pulmonary circulation shunts blood
away from the lungs?
How does fetal circulation allow blood to bypass the lungs?
trunk to the descending portion of the aortic arch. As a result
of this connection, the blood with a relatively low oxygen
concentration, returning to the heart through the superior
vena cava, bypasses the lungs and does not enter the portion
of the aorta that branches to the heart and brain.
The more highly oxygenated blood that enters the
left atrium through the foramen ovale mixes with a small
amount of deoxygenated blood returning from the pulmo-
nary veins. This mixture moves into the left ventricle and is
pumped into the aorta. Some of it reaches the myocardium
through the coronary arteries, and some reaches the brain
tissues through the carotid arteries.
Blood carried by the descending aorta includes the less oxy-
genated blood from the ductus arteriosus. Some of the blood
is carried into the branches of the aorta that lead to the lower
regions of the body. The rest passes into the
which branch from the internal iliac arteries and lead to the pla-
centa. There the blood is reoxygenated
(f gs. 23.25
The umbilical cord usually contains two arteries and one
vein. Rarely, newborns have only one umbilical artery. This