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Ch. 19 The Cardiovascular System: Blood Vessels
Marieb - Human Anatomy & Physiology 11th Edition
Marieb, Hoehn11th EditionHuman Anatomy & PhysiologyISBN: 9780136874034Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoMarieb, Hoehn 11th EditionCh. 19 The Cardiovascular System: Blood VesselsProblema 9
Capitolo 19, Problema 9

Blood flow in the capillaries is steady despite the rhythmic pumping of the heart because of the:
a. Elasticity of the large arteries
b. Small diameter of capillaries
c. Thin walls of the veins
d. Venous valves

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1
Understand the physiological context: The heart pumps blood in a rhythmic, pulsatile manner, but blood flow in capillaries is steady and continuous rather than pulsatile.
Recall the role of large arteries: Large arteries, such as the aorta, have elastic walls that stretch when the heart pumps blood and then recoil to maintain pressure and smooth out the flow between heartbeats.
Analyze the options: Consider how each option might contribute to steady blood flow. The small diameter of capillaries affects resistance but not the smoothing of flow; thin walls of veins relate to permeability, not flow steadiness; venous valves prevent backflow but do not smooth arterial pulsations.
Identify the correct mechanism: The elasticity of large arteries acts as a pressure reservoir, absorbing the pulsatile output of the heart and releasing it steadily, which results in continuous capillary blood flow.
Summarize the concept: The Windkessel effect, due to the elastic recoil of large arteries, is responsible for converting the intermittent pumping of the heart into a steady flow in the capillaries.

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Elasticity of Large Arteries

Large arteries, such as the aorta, have elastic walls that stretch during the heart's pumping phase and recoil during relaxation. This elasticity smooths out the pulsatile blood flow from the heart, converting it into a more steady flow in smaller vessels like capillaries.
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Percorso guidato
1:42
Arteries Example 1

Capillary Structure and Function

Capillaries are tiny blood vessels with thin walls that facilitate exchange of gases and nutrients. Their small diameter slows blood flow, but the steadiness of flow is mainly influenced by upstream factors rather than their size alone.
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Percorso guidato
5:59
General Structure of Capillary Beds

Role of Venous Valves

Venous valves prevent backflow of blood in veins, ensuring unidirectional flow toward the heart. While important for venous return, they do not directly affect the steadiness of blood flow in capillaries.
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7:13
Systole, Diastole, Pressure, & Valves
Pratica correlata
Domanda del libro di testo

The myocardium receives its blood supply directly from the:

a. Aorta

b. Coronary arteries

c. Coronary sinus

d. Pulmonary arteries

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Tracing the blood from the heart to the right hand, we find that blood leaves the heart and passes through the aorta, the right subclavian artery, the axillary and brachial arteries, and through either the radial or ulnar artery to arrive at the hand. Which artery is missing from this sequence?

a. Coronary

b. Brachiocephalic

c. Cephalic

d. Right common carotid

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How is the anatomy of capillaries and capillary beds well suited to their function?

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Using the letters from column B, match the artery descriptions in column A. (Note that some require more than a single choice.)

Column A 

____  (1) unpaired branch of abdominal aorta 

____  (2) second branch of aortic arch 

____ 3) branch of internal carotid 

____ (4) branch of external carotid 

____  (5) origin of femoral arteries

Column B

a. right common carotid

b. superior mesenteric

c. left common carotid

d. external iliac

e. inferior mesenteric

f. superficial temporal

g. celiac trunk

h. facial

i. ophthalmic

j. internal iliac

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Domanda del libro di testo

The structure of a capillary wall differs from that of a vein or an artery because

a. it has two tunics instead of three

b. there is less smooth muscle

c. it has a single tunic—only the tunica intima

d. none of these

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The baroreceptors in the carotid sinus and aortic arch are sensitive to

a. a decrease in CO₂

b. changes in arterial pressure

c. a decrease in O₂

d. all of these

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