WEEK 3: CH 14--Circulation & CH 15--Vascular Distensibility

Question 1

The blood vessels of the body form a______ loop system that begins and ends at the heart

Answer 1

closed

Question 2

Structure of Vessel Walls

1. Except for the capillaries, all the other blood vessel walls have three layers referred to as “_________” (coverings) that surround the lumen
2. The ________ is the inner channel within the blood vessel tubing that contains the blood.

Answer 2

tunics

lumen

Question 3

Blood Vessel Layers

1. Tunica Intima-contains the endothelium that lines the lumen. Forms a slick surface that minimizes friction.
2. Tunica Media-circularly arranged smooth muscle and layers of elastic fibers. Regulates vasoconstriction and
   vasodilation of vessels. Usually thickest layer.
3. Tunica Externa (Adventitia) composed mainly of collagen fibers that protect and reinforce the vessel. This layer contains nerve fibers, lymphatic vessels and tiny blood vessels called____ _______ to nourish the external
   tissues of the blood vessels.

Answer 3

vasa vasorum

Question 4

General blood circulation is divided into:

A. ___________Circulation—blood flow to
all the tissues in the body except the lungs.
Arteries carry oxygenated blood to the tissues
and veins carry deoxgenated blood back to the
heart.
B. ___________ Circulation—blood flow through the
lungs to exchange CO2 for O2. Pulmonary
arteries still carry blood away from the heart but
it is deoxgenated. Therefore, the pulmonary
veins carry oxygenated blood back to the heart

Answer 4

Peripheral (Systemic)

Pulmonary

Question 5

_________ are the largest and most elastic vessels
on the arterial side to move blood away from the
heart under high pressure.

Answer 5

Arteries

Question 6

Arteries empty into smaller arterioles and blood
pressure_________ rapidly. Arterioles have strong
muscular walls so terminal arterioles are able to
vasodilate and vasoconstrict in response to tissue
needs

Answer 6

decreases

Question 7

Capillaries are the narrowest of vessels, the walls are one cell thick. Pressure is ________ considerably so that gas and nutrient exchange can occur between the blood and the tissues. Capillary pores are permeable to water, nutrients, electrolytes, hormones and other small molecules.

Answer 7

reduced

Question 8

Capillaries eventually connect to __________ which
empty into veins. There is little _________ in the
veins so the walls are thinner but the lumen is
larger in diameter. The larger lumen allows the
veins to serve as a reservoir for blood. Veins are
highly expandable so can expand and contract.

Answer 8

venules

pressure

Question 9

Volume of Blood in Areas of Circulatory System

Pulmonary System = 16%

a) heart = 7%
b) lungs = 9%

Systemic System = 84%

a) arteries = 13%
b) arterioles &capillaries = 7%
c) venules & veins = 64%

Answer 9

know

Question 10

Blood flow the volume of blood flowing through the vessels, organs, or the entire system in a given period (e.g. SV = 70 ml/beat at rest)

Tissues regulate blood flow based on need. When tissues are more active, they may require ___ to ____ times the blood flow at rest. Because blood flow can only increase 4 to 7 times above resting, local tissues must vasoconstrict or
vasodilate blood vessels depending on their need at that time.

Answer 10

20 to 30

Question 11

Types of Blood Flow

1. _______ Flow—occurs when blood flows at a steady
   stream though a smooth vessel because each layer
   of blood remains the same distance from the vessel
   wall. When ______flow occurs, the blood in the center
   flows faster than outer layers. Therefore, _________
   flow exhibits a parabolic profile.

Answer 11

Laminar

laminar

laminar

Question 12

Types of Blood Flow

2. __________ Flow—occurs when blood flow is fast and/or the blood passes over a rough surface or an obstruction. ________ flow means that the blood begins forming whorls resulting in eddy currents. The eddy currents cause resistance to flow when compared to the streamlined movements of laminar flow.

Answer 12

Turbulent

Turbulent

***Turbulence is mostly seen when blood enters the pulmonary artery and especially the aorta. Not usually seen in the smaller blood vessels.

Question 13

Blood Pressures in Areas of Systemic System

• Blood Pressure is the force per unit area exerted on the vessel wall by the contained blood. It is measured in mmHg.
• Arterial Pressure fluctuates between 120 mmHg (SBP) and 80 mmHg (DBP).
• Capillary Pressure ranges from a high of 35 mmHg on the arteriole side and drops to 15 mmHg on the venule side

Answer 13

know this

Question 14

Resistance is the opposition to ____. It is a measure of the friction blood encounters as it passes through the vessels.

Most friction is encountered in vessels away from
the heart so it is referred to as _________ resistance.

Resistance of the entire systemic circulation
(arteries through veins) is called : _____ _________
resistance.

Answer 14

flow

peripheral

total peripheral

Question 15

Four Sources of Resistance

1. Blood Vessel Length—the relationship of length to
   resistance is straight foward:
   a. the LONGER the vessel, the GREATER the resistance.
   b. If diameter is equal, if you ________ the length, you double the resistance.
   c. ________ increases with growth during childhood but is normally unchanged as adults.

Answer 15

double

Length

Question 16

Four Sources of Resistance

2. Blood Vessel Diameter—changes in diameter significantly alter peripheral resistance. Largest changes to resistance to flow occur in the ________ where the muscular layer (tunica media) can change the diameter of the vessel significantly by way of vasoconstriction (narrowing of vessel) and vasodilation (widening vessel).

–Change is blood vessel ________ is based on the “Fourth Power Law” meaning that if the diameter of a vessel doubles, flow does not double (r2), it increases by the power of four (r4).

Answer 16

arterioles

diameter

Question 17

Four Sources of Resistance

3. Series vs. Parallel Blood Vessels—blood vessels are a sequence of both series and parallel blood vessels. Blood flow begins in the larger series vessels (arteries) and eventually into smaller parallel vessels (capillaries) in many organs—brain, kidneys, muscle, digestive system, skin, and coronary circulation.

*** Although the parallel areas are smaller in diameter, the vessels are smoother and not much muscle so resistance is lower thus flow through PARALLEL vessels is _________.

Answer 17

faster.

Side Note: Because parallel blood vessels help lower total peripheral resistance (TPR), if a limb is amputated or a kidney is surgically removed, this will raise TPR because part of the parallel system has been removed.

Question 18

Four Sources of Resistance

4. Blood Viscosity—resistance to flow is affected by the thickness of the blood (viscosity). Normal blood viscosity is about 3 to 4 times the viscosity of water.

A. If all other factors (vessel length and diameter) are the same, the more viscous the blood, the more_______ to flow.

B. Blood is made up of two major components:

(a) plasma—water and plasma proteins
(b) formed elements—RBCs, WBCs, platelets

Answer 18

resistance

QUICK TIP

**Hematocrit—the percentage of blood made up of RBCs.
Males 42% (males have higher EPO levels)
Females 38%

Question 19

Blood viscosity is fairly constant but conditions like _______ (low RBC count) and __________ (very high number of RBCs) can affect viscosity and thus resistance to flow.

Answer 19

anemia

polycythemia

Question 20

Ohm’s Law – is a formula based on two factors
as they relate to the 3 components (F, P, R):

1. Blood Flow (F) is directly proportional to the difference is blood pressure (∆P) between two points in circulation resulting from the pressure gradient.

Answer 20

↑ ∆P → ↑F

↓ ∆P → ↓F

Question 21

Ohm’s Law

2. Blood Flow (F) is __________ proportional to
   peripheral resistance (R). This most often
   occurs in the arterioles with the thick layer of
   tunica media.
   Vasodilation: ↓ R → ↑F

Vasoconstriction: ↑ R → ↓F

Answer 21

inversely

Question 22

______________ – is the ability of a blood vessel to
become stretched, expanded, or dilated due
to an internal pressure. The blood vessels are able to dilate (expand) because of layers of elastin between the layers
of smooth muscle.

Answer 22

Distensability

Question 23

The walls of the arteries are able to stretch but they are much stronger than the walls of the veins. Therefore, the walls of the veins are about __ times more distensible than the walls of the arteries.

Answer 23

8

Question 24

__________– deals not only with the ability of the
vessel to stretch but also includes the total quantity of blood that can be stored in a given vessel for each mmHg of pressure. A vessel may have the ability to stretch (high dispensability) but if it does not contain a lot of blood, it has low compliance.

Answer 24

Compliance

Compliance = dispensability X volume

Question 25

________ __________—is calculated as the difference
between SBP and DBP.

PP = SBP - DBP
= 120 - 80
= 40 mmHg

Answer 25

Pulse Pressure

Question 26

Mean Arterial Pressure (MAP) is an important measurement as it reflects the pressure that _______ the blood to the tissues.

Answer 26

propels

Question 27

Functions of Veins

• Blood Reservoir—under normal, resting conditions, 64% of all blood volume is in the _______side of circulation.

• When blood is lost (hemorrhage) and the arterial pressure begins to fall, pressure sensitive areas of circulation (e.g. carotid sinuses) signal the CNS to release hormones via the
sympathetic NS which signal the veins to ________

• This allows more blood to stay in the system for a longer
period of time. In fact, even with ____- ____ % blood loss, the circulatory system functions normally.

Answer 27

venous

constrict.

20-25%

Question 28

“______ _________” or muscle pump—every time a
person takes a step, a certain amount of blood is
propelled back toward the heart. The skeletal muscles surrounding the deep veins push the blood upward and one-way valves prevent backflow.

Answer 28

Venous Pump

Question 29

“___________” Veins—occurs when the valves in the venous system become incompetent.

1 • The veins can be overstretched by excessive venous pressures such as during pregnancy.

2 • The cross-sectional area of the vein ________ but the
valves do NOT increase in size so the leaflets do NOT close the vein off completely. This will increase ______ more and eventually the valve is destroyed.

Answer 29

Varicose

increases

pressure