Download Circulation Assignment KEY

Assignment Questions for
C-13 Circulation
--------------------------------------------Name
1. Explain the relationship between blood vessel structure and function.
Walls of arteries are usually much thicker, their tunica media tends to be much heavier. This
is because arteries are closer to the pumping action of the heart – they must be able to expand
as blood is forced into them and recoil passively as blood flows off. So their walls must be
strong and stretch enough to take these continuous changes in pressure.
Veins are far from the heart in the circulatory pathway, and the pressure in them tends to be
low all the time, so veins have thinner walls. However, since blood pressure in veins is
usually too low to force blood back to the heart and blood returning back to the heart often
flows against gravity, veins are modified to assure that the amount of blood returning to the
heart equals that being pumped out of the heart at any time. Therefore, their lumens tend to
be much larger than those of corresponding arteries; and larger veins have valves that prevent
backflow of blood.
2. Trace the path of blood through the hepatic portal and fetal circulations.
The veins of the hepatic portal circulation drain the digestive organs, spleen, pancreas, and
deliver this blood to the liver through the hepatic portal vein. As blood flows slowly through
the liver, some of the nutrients are removed to be stored or processed in various ways for
later release to the blood. The liver is drained by the hepatic veins that enter the inferior vena
cava. The inferior mesenteric vein, which drains the terminal part of the large intestine,
drains into the splenic vein, which drains into the spleen, pancreas, and left side of the
stomach. The splenic vein and superior mesenteric vein (which drains the small intestine and
the first part of the colon) join to form the hepatic portal vein. The gastric vein, which drains
the right side of the stomach, drains directly into the hepatic portal vein.
Normally arteries feed capillary beds, which in turn drain into veins, but hepatic circulation is
unique in that veins feed the liver circulation.
Fetal circulation is different because the lungs and digestive system are not yet functioning in
a fetus, so nutrient, excretory, and gas exchanges occur through the placenta.
The umbilical cord contains three blood vessels: one large umbilical vein and two smaller
umbilical arteries. The umbilical vein carries blood rich in nutrients and oxygen to the fetus.
The umbilical arteries carry carbon dioxide and wastes to the placenta. As blood flows
superiorly toward the heart of the fetus, most of it bypasses the immature liver through the
ductus venosus and enters the inferior vena cava, which carries the blood to the right atrium
of the heart.
Some of the blood entering the right atrium is shunted directly into the left atrium through a
flap-like opening in the interatrial septum, the foramen ovale, because the fetal lungs are
nonfunctional and collapsed. Blood that does manage to enter the right ventricle is pumped
out the pulmonary trunk, where it meets a second shunt, the ductus arteriosus, a short vessel
that connects the aorta and pulmonary trunk. Blood tends to enter the systemic circulation
through the ductus arteriosus and the aorta carries blood to the tissues of the fetal body and
ultimately back to the placenta through the umbilical arteries.
3. Identify the primary factors involved in the generation and regulation of blood pressure
and explain the relationships between these factors.
Blood pressure is the pressure the blood exerts against the inner walls of the blood vessels.
Systolic pressure is the pressure in the arteries at the peak of ventricular contraction and
diastolic pressure is the pressure when the ventricles are relaxing. Arterial blood pressure is
directly related to cardiac output (the amount of blood pumped out of the left ventricle per
minute) and peripheral resistance to blood flow.
Cardiac output is the amount of blood pumped out by each side of the heart in one minute. It
is the product of heart rate and stroke volume.
Stroke volume is the volume of blood pumped out by a ventricle with each heartbeat.
Peripheral resistance is the mount of friction encountered by the blood as it flows through the
blood vessels.
Effects of blood pressure are constriction of blood vessels, increased blood volume or blood
viscosity (thickness), age, weight, time of day, exercise, body position, emotional state, and
various drugs.
4. Intravenous injections are most often given into a vein called:
Median cubital vein, Cephalic Vein (lateral forearm), Basilic Vein (medial forearm)
5. In fetal circulation, the aorta is connected to the pulmonary artery by a vessel called:
Ductus arteriosus
6. Pulse felt in the wrist region develops from an artery called:
Radial artery
7. The body organ that stores blood and releases it in the case of hemorrhage is called the:
Spleen & Liver
8. Blood pressure is highest in the
venae cavae (veins)
large arteries
.
and lowest in the