Section 11.3: Blood Vessels
Mini Investigation: Taking a Pulse
(Page. 488)
A. The radial artery is the most commonly used pulse point because it is usually the most accessible
(easiest to observe).
B. Answers will vary. Students may have experienced difficulty in finding other pulse points because
they have not tried to locate these points before. Some of them may be more difficult to locate
because the artery may be deeper under the skin and are therefore less noticeable.
C. Police or medical personnel usually check the carotid pulse rather than the radial pulse because the
limbs are often injured in trauma cases or blood flow to the extremities may be blocked, so the
radial pulse might not be observable even though the person is alive. The carotid pulse is nearer the
heart and might be observable even with a weak heart beat.
Section 11.3 Questions
(Page 494)
1.
Arteries
carry blood away from the heart
layer of smooth muscle is thicker than in veins
2.
3.
4.
5.
6.
7.
Veins
carry blood toward the heart
layer of smooth muscle is thinner than in
arteries
internal diameter less than veins
internal diameter greater than arteries
do not have valves
larger veins have valves
higher blood pressure
lower blood pressure
(a) A pulse is the temporary expansion of an artery that is felt when the heart contracts and forces
blood through the artery.
(b) Each time the heart beats you can feel the pulse. By observing the pulse you can determine the
heart rate.
Gravity helps the flow of blood when it is moving downward from the heart but hinders the flow
when blood is moving upward toward the heart or the head and upper parts of the body. The larger
veins of the body have valves that prevent blood from flowing backwards when the pressure is
reduced. For example, when blood is moving upward through the veins of the legs, the valves close
preventing the blood from flowing back when the heart relaxes between beats.
The blood vessel shown in Figure 15 is a capillary because the blood vessel is just a little wider than
the diameter of the red blood cells. This is the smallest blood vessel through which blood cells can
travel, so it must be a capillary.
The blood flow decreases in the capillary networks because the cross-sectional area in the capillary
networks is much greater than the cross-sectional area of the largest blood vessel. When a fluid
moves from a small diameter tube into a tube of larger diameter, the pressure is reduced and the rate
of flow is also reduced. This is an advantage because the slower flow provides more time for
materials to diffuse in to and out of the bloodstream.
A smoker would have high blood pressure. Since the blood vessels are smaller in diameter when
constricted by nicotine and the volume of blood remains the same, the pressure inside the vessels
must be greater.
Answers will vary. Students will likely find that they consumed more than the recommended upper
level of 2300 mg per day. Hypertension is one of the possible effects of consuming too much
sodium. An increase in the sodium concentration causes water to move into the blood by osmosis,
causing an increase in the volume of blood and therefore increased blood pressure.
Copyright © 2011 Nelson Education Ltd.
Chapter 11: The Circulatory System
11.3-1
8. Answers will vary.
Sample answer: Hypertension is a major risk factor for cardiovascular disease (CVD) and stroke.
Approximately 31 million individuals worldwide suffer strokes each year leading to approximately
4 million deaths. Most of the direct cost of hypertension comes from drug treatment and other health
care measures. However, the cost also includes the cost of an increased incidence of cardiovascular
events resulting from hypertension. Approximately only 13–27 % of people with hypertension are
adequately treated and have their hypertension controlled. This has a cost-saving effect because it
prevents the costs associated with illnesses stemming from hypertension. However, there is still a
tremendous financial and social burden on the healthcare system and society, because uncontrolled
hypertension leads to higher rates of cardiovascular events and early death. It is fairly easy to
estimate the short-term costs of treating hypertension; estimating the costs savings associated with
fewer cardiovascular events is much more difficult.
9. The lymphatic system has two main roles. The first role is to help maintain the volume of blood by
ensuring that excess fluid is collected from the tissues and returned to the blood. It also collects fat
molecules absorbed through the lacteals in the villi of the large intestine and transfers them into the
bloodstream. The other role is in the immune system. The lymphatic system acts as a filtration
system to remove bacterial or other harmful cells from the blood.
10. The spleen acts as a filtering station and as a reservoir of red and white blood cells. Removal of the
spleen can affect the immune system and make the individual more susceptible to bacterial, viral, or
fungal infections. During times of high oxygen demand, the spleen can release extra red blood cells
to help carry more oxygen. An individual who has had the spleen removed may experience a lack of
oxygen characterized by shortness of breath and fatigue during periods of physical exertion.
Copyright © 2011 Nelson Education Ltd.
Chapter 11: The Circulatory System
11.3-2