THE ARTERIAL DISTRIBUTION AND VENOUS COLLECTION SYSTEMS

Question 1

_______________ is the study of the physical laws of blood circulation. It therefore addresses the properties of both the “content” (i.e., blood) and the “container” (i.e., blood vessels).

Answer 1

Hemodynamics

Question 2

True or False: The circulation is not a system of rigid tubes.

Answer 2

True

Question 3

We can think of the _________ as a distribution system, the ______________ as a diffusion and filtration system, and the ______ as a collection system.

Answer 3

arteries
microcirculation
veins

Question 4

The aorta branches out into billions of capillaries that ultimately regroup into a __________.

Answer 4

single vena cava

Question 5

At each level of arborization of the peripheral circulation, the values of several key parameters vary dramatically:

Answer 5

1. Number of vessels at each level of arborization
2. Radius of a typical individual vessel
3. Aggregate cross-sectional area of all vessels at that level
4. Mean linear velocity of blood ow within an individual vessel
5. Flow (i.e., volume/second) through a single vessel

Question 6

At each level of arborization of the peripheral circulation, the values of several key parameters vary dramatically: (II)

Answer 6

6. Relative blood volume (i.e., the fraction of the body’s total blood volume present in all vessels of a given level)
7. Circulation (i.e., transit) time between two points of the circuit
8. Pressure pro le along that portion of the circuit
9. Structure of the vascular walls
10. Elastic properties of the vascular walls

Question 7

The _____________ at a particular level of arborization increases enormously from a single aorta to ∼104 small arteries, 107 arterioles, and finally ∼4 ×1010 capillaries.

Answer 7

number of vessels

Question 8

However, only about __________ of all capillaries are normally open to ow at rest. Finally, all of the blood returns to a single vessel where the superior and inferior venae cavae join.

Answer 8

one fourth

Question 9

The ____________ declines as a result of the arborization, decreasing from 1.1 cm in the aorta to a minimum of ∼3 μm in the smallest capillaries.

Answer 9

radius of an individual vessel

Question 10

Because the cross-sectional area of an individual vessel is __________ to the square of the radius, this parameter decreases even more precipitously.

Answer 10

proportional

Question 11

The ______________ at any level of branching is the sum of the single cross-sectional areas of all parallel vessels at that level of branching.

Answer 11

aggregate cross-sectional area

Question 12

A fundamental law of vessel branching is that at each branch point, the combined cross-sectional area of daughter vessels ____________ the cross-sectional area of the parent vessel.

Answer 12

exceeds

Question 13

In this process of bifurcation, the steepest increase in total cross-sectional area occurs in the _____________.

Answer 13

microcirculation

Question 14

A _______________ in the smooth muscle and submucosa of the intestine encompasses a first-order arteriole, several orders of progressively smaller arterioles, capillaries, several orders of venules into which the capillaries empty, and eventually a first-order venule.

Answer 14

typical microcirculation

Question 15

In humans, the maximum cross-sectional area occurs not at the level of the capillaries but at the “_______________” (i.e., fourth-order) venules.

Answer 15

postcapillary

Question 16

Because of anastomoses among capillaries, capillaries only _____________ fourth-order venules, whereas the cross-sectional unit area of each venule is appreciably _______ than the area of a capillary.

Answer 16

Slightly outnumber

greater

Question 17

Assuming that only a quarter of the capillaries are usually open, the peak aggregate cross-sectional area of these postcapillary venules can be ~______________ than the cross section of the parent artery (e.g., aorta).

Answer 17

1000-fold greater

Question 18

The profile of the _________________ of flow (v) along a vascular circuit is roughly a mirror image of the profile of the total cross-sectional area.

Answer 18

Mean linear velocity

Question 19

According to the _____________, which is an application of conversation of mass, TOTAL VOLUME FLOW of blood must be the same at any level of arborization.

Answer 19

Principle of continuity

Question 20

As a consequence, v must be minimal in the postcapillary venules (~_______ cm/s) where A(total) is maximal.

Answer 20

0.03 cm/s

Question 21

Conversely, v is maximal in the aorta (~__________ cm/s)

Answer 21

20 to 50 cm/s

Question 22

Thus, both A(total) and v values range ~1000 fold from the aorta to the capillaries but are ___________ to one another.

Answer 22

Inversely related

Question 23

The vena cava with a cross-sectional area ~50% larger than that of the aorta, has a mean linear velocity that is about __________.

Answer 23

One third less

Question 24

___________, in contrast to total flow, varies by ~10 orders of magnitude.

Answer 24

Single-vessel flow

Question 25

In the aorta, the flow is ______ the same as the cardiac output (~5 L/min).

Answer 25

~83 mL/s

Question 26

When about ____ of the capillaries are open, a typical capillary has a mean linear velocity of 0.03 cm/s and a flow of 8x10-9 mL/s (8 pL/s) - 10 orders of magnitude less than the flow in the aorta.

Answer 26

25%

Question 27

True or False: Within the microcirculation, single-vessel flow has considerable range.

Answer 27

True

Question 28

Most of the blood volume resides in the _________.

Answer 28

Systemic veins

Question 29

The body's ______________ of about 5 L is not uniformly distributed along the x-axis.

Answer 29

Total blood volume (V)

Question 30

At any level of branching, the __________ is the sum of the volumes of all parallel branches.

Answer 30

Total blood volume

Question 31

Percentage of total blood volume.

Answer 31

Relative blood volumes

Question 32

First, we can divide the blood volume into the systemic circulation (where ____ of blood resides), the pulmonary circulation (____) and the heart chambers (_____).

Answer 32

85% 10% 5%

Question 33

________________ is quite adjustable (i.e, it can be much higher than 10%) and is carefully regulated.

Answer 33

Pulmonary blood volume

Question 34

We can divide blood volume into what is contained in the high-pressure system (____), the low-pressure system (____) and the heart chambers (____).

Answer 34

15% 80% 5%

Question 35

Of the 85% of the total blood volume that resides in the systemic circulation about three fourths ____% of the total- is on the venous side, particularly in the smaller veins.

Answer 35

65%

Question 36

Thus the _________ acts as a volume reservoir.

Answer 36

Venous system

Question 37

An abrupt increase in venous capacity causes pooling of blood in venous segments and may lead to ___________.

Answer 37

Syncope

Question 38

We can also use a fourth approach for grouping of blood volumes - divide the blood into the _______________ (volumes of heart chambers and pulmonary circulation) versus the rest of circulation.

Answer 38

Central blood volume

Question 39

This is very adjustable and it constitutes the filling reservoir for the left heart.

Answer 39

Central blood group

Question 40

Can cause the normally careful regulation of the central blood volume to break down.

Answer 40

Left-sided heart failure

Question 41

The _______________ is the time required for a bolus of blood to travel either across the entire length of the circulation or across a particular vascular bed.

Answer 41

Circulation time

Question 42

Total circulation time is ____ minute.

Answer 42

1 minute

Question 43

Circulatory time across a single vascular bed (i.e coronary circulation) may be as short as ___________.

Answer 43

10 seconds

Question 44

Circulation times may be obtained in humans by injection of a substance such as _________ into an antecubital vein and measurement of the time to its appearance in the lung (___ to ____ seconds) or by injection of a bitter or sweet substance and measurement of the time to the perception of taste in the tongue (____ to ____ seconds).

Answer 44

Ether 4 to 8 seconds 10 to 18 seconds

Question 45

Although in the past, circulation time was used clinically as an index of __________, the measurement has little physiological significance.

Answer 45

Cardiac output

Question 46

The rationale for determination of ___________ was that a shortening of circulation time could signify an improvement of cardiac output.

Answer 46

Circulation time

Question 47

However, the interpretation is more complicated because the _____________ is actually the ratio of blood volume to blood flow.

Answer 47

circulation time

Question 48

True or False: Changes in circulation time may thus reflect no changes in volume as well as in flow.

Answer 48

False: Changes

Question 49

The intravascular pressures along the systemic circuit are ______ than those along the pulmonary circuit.

Answer 49

Higher

Question 50

Pressures are far ________ in the systemic than in the pulmonary circulation.

Answer 50

Higher

Question 51

Although the cardiac output of the left and right hearts are the same in the steady state, the total resistance of the systemic circulation is far _____ than that of the pulmonary circulation.

Answer 51

Higher

Question 52

This difference explains why the upstream driving pressure averages ___ mmHg in the systemic circulation but only ____ mmHg in the pulmonary circulation.

Answer 52

95 mmHg | 15 mmHg

Question 53

In both the systemic and pulmonary circulations, the systolic and diastolic pressures ________ downstream from the ventricles.

Answer 53

Decay

Question 54

In addition, the systemic venous and pulmonary pressures vary with the respiratory cycle and venous pressure in the lower limbs varies with the contraction of _______________.

Answer 54

Skeletal muscle

Question 55

The ___________ extends froms the left ventricle in the contracted state all the way to the systemic arterioles.

Answer 55

High pressure system

Question 56

The ____________ extends from the systemic capillaries, through the rest of the systemic circuit into the right heart and then through the pulmonary circuit into the left heart in the relaxed state.

Answer 56

Low-pressure system

Question 57

The ____________, unlike the systemic circuit is entirely a low pressure system; ___________ normally do not exceed 15 mmHg and the _________ do not rise above 10 mmHg.

Answer 57

Pulmonary circuit Mean arterial pressure Capillary pressures

Question 58

Under normal conditions, the steepest pressure drop in the sytemic circulation occurs in __________, the site of greatest vascular resistance.

Answer 58

Arterioles

Question 59

It is the ___________ of each vascular segment that determines the profile of pressure fall between the upstream arterial and downstream venous ends of the circulation.

Answer 59

resistance

Question 60

In particular, the pressure difference between two points along the axis of the vessel depends on the _______ and ___________.

Answer 60

Flow and resistance

Question 61

According to ___________, the resistance (Ri) of an individual, unbranched vascular segment is inversely proportional to the fourth power of the radius,

Answer 61

Poiseuille's law

Question 62

Thus the pressure drop between any two points along the circuit depends critically on the ____________ between these two points.

Answer 62

Diameter of the vessels

Question 63

The steepest pressure drop does not occur along the capillaries where vessel diameters are smallest but rather along the _______________.

Answer 63

Precapillary arterioles

Question 64

The _______________ contributed by vessels of a particular order of arborization depends not only on their average radius but also on the number of vessels in parallel.

Answer 64

Aggregate resistance

Question 65

The more vessels in parallel, the ________ the aggregate resistance.

Answer 65

Smaller

Question 66

True or False: Although the resistance of a single capillary exceeds that of a single arteriole, capillaries far outnumber arterioles.

Answer 66

True

Question 67

The result is that aggregate resistance is larger in the arterioles and this is where the ____________ occurs.

Answer 67

Steepest 🔼P

Question 68

________________ depends on the distribution of vascular resistance.

Answer 68

Local intravascular pressure

Question 69

The major site of control of vascular resistance in the systemic circulation is the _____________ and ____________.

Answer 69

Terminal small arteries or feed arteries and arterioles

Question 70

During ___________, the pressure drop between two points along the circuit is steep and concentrated at the arteriolar site.

Answer 70

Arteriolar constriction

Question 71

During __________, the gradient is shallow and more spread out.

Answer 71

Arteriolar dilation