Essentials of Anatomy and Physiology

and nutrients from the mother’s blood enter fetal

circulation.

The umbilical veincarries this oxygenated blood

from the placenta to the fetus. Within the body of the

fetus, the umbilical vein branches: One branch takes

some blood to the fetal liver, but most of the blood

passes through the ductus venosusto the inferior

vena cava, to the right atrium. After birth, when the

umbilical cord is cut, the remnants of these fetal ves-

sels constrict and become nonfunctional.

The other modifications of fetal circulation con-

cern the fetal heart and large arteries (also shown in

304 The Vascular System

Inferior vena cava

Hepatic vein

Liver

Portal vein

Superior

mesenteric V

Right colic V.

Ascending colon

Left gastric V.

Right gastric V.

Splenic V.

Spleen

Stomach

Pancreas

Left gastroepiploic V.

Inferior mesenteric V.Inferior mesenteric V.

Left colic V.

Descending colon

Figure 13–7. Hepatic por-

tal circulation. Portions of

some of the digestive organs

have been removed to show

the veins that unite to form

the portal vein. See text for

description.

QUESTION:The blood in the

portal vein is going to what

organ? Where is the blood

coming from?

BOX13–3 PULSE SITES

Popliteal—the popliteal artery at the back of the

knee.

Dorsalis pedis—the dorsalis pedis artery on the

top of the foot (commonly called the pedal pulse).

Pulse rate is, of course, the heart rate. However,

if the heart is beating weakly, a radial pulse may be

lower than an apical pulse(listening to the heart

itself with a stethoscope). This is called a pulse

deficitand indicates heart disease of some kind.

When taking a pulse, the careful observer also

notes the rhythm and force of the pulse. Abnormal

rhythms may reflect cardiac arrhythmias, and the

force of the pulse (strong or weak) is helpful in

assessing the general condition of the heart and

arteries.

A pulse is the heartbeat that is felt at an arterial site.

What is felt is not actually the force exerted by the

blood, but the force of ventricular contraction

transmitted through the walls of the arteries. This is

why pulses are not felt in veins; they are too far

from the heart for the force to be detectable.

The most commonly used pulse sites are:

Radial—the radial artery on the thumb side of the

wrist.

Carotid—the carotid artery lateral to the larynx in

the neck.

Temporal—the temporal artery just in front of the

ear.

Femoral—the femoral artery at the top of the

thigh.