Chapter 43: Circulatory System

Atmospheric pressure at sea level is equal to a column of 760 mm Hg. Oxygen makes up 21 percent of the atmosphere by volume. The partial pressure of oxygen (PO2) in such conditions is _____.

160 mm Hg16 mm Hg SubmitP

At the summit of a high mountain, the atmospheric pressure is 380 mm Hg. If the atmosphere is still composed of 21percent oxygen, then the partial pressure of oxygen at this altitude is about _____.

80 mm Hg

Which lung structure is a tiny sac that functions as an interface between air and blood?

Alveolus.

_____ in carbon dioxide in your red blood cells, which causes _____ in pH, causes your breathing to speed up.

An increase ... a drop

Which of the following best describes an artery?

Arteries carry blood away from the heart.

How is most carbon dioxide transported from tissues to the lungs?

As bicarbonate ions (HCO3−HCO3−).

Why does the velocity of blood slow greatly as blood flows from arterioles into capillaries?

Because capillary beds have a total cross-sectional area much greater than the total cross-sectional area of the arterioles.

Select the correct statement about capillary beds.

Capillary beds are the site of nutrient and oxygen delivery to tissues.

Which statement about human blood vessels is correct?

Pulmonary veins carry oxygen-rich blood to the heart.

By picking up hydrogen ions, hemoglobin prevents the blood from becoming too _____.

acidic

Damage to the sinoatrial node in humans _____.

would disrupt the rate and timing of cardiac muscle contractions

True or false? The driving force for the unloading of oxygen from hemoglobin into tissues is the difference in PCO2 levels between the blood and body tissues.

False

True or false? The pressure inside the human chest cavity is always positive, so the lungs stay relatively inflated even upon exhalation.

False

How has the avian lung adapted to the metabolic demands of flight?

Gas exchange occurs during both inhalation and exhalation

Which statement about lipoproteins is correct?

High-density lipoproteins are cholesterol transporters in the blood.

Which statement regarding the mammalian heart is correct?

In the adult heart, blood in the right chambers of the heart cannot enter the left chambers without passing through the lungs. Submit

How are gases transported in insect bodies?

In tracheal systemsC

What is the function of a circulatory system?

It brings a transport liquid into close contact with all cells in the body.

What is the function of the left ventricle?

It pumps oxygenated blood around the body via the systemic circulation.

Which event occurs first during atrial and ventricular diastole?

The atria and ventricles are relaxed, and blood flows into the atria.

Which of the following statements about the oxygen-hemoglobin interaction is true?

The binding of one oxygen molecule to hemoglobin stimulates the binding of other oxygen molecules.

Why do the circulatory systems of land vertebrates have separate circuits to the lungs and to the rest of the body?

The large decrease in blood pressure as blood moves through the lungs may prevent efficient circulation through the rest of the body.

A rabbit taken from a meadow near sea level and moved to a meadow high on a mountainside would have some trouble breathing. Why?

The partial pressure of oxygen in the air at high elevations is lower than at sea level.

Select the correct statement about the three-chambered hearts of amphibians and nonbird reptiles.

The three-chambered hearts of amphibians and nonbird reptiles are facultative, allowing variation in blood flow through the heart.

Which event of the cardiac cycle occurs when systolic blood pressure is measured?

The ventricles contract, carrying blood into the aorta, and blood flows into the relaxed atria.

True or false? The circulatory systems of land-dwelling vertebrates are composed of two pumping circuits: the systemic circulation, which is a lower-pressure circuit to the lung, and the pulmonary circulation, which is a higher-pressure circuit to the rest of the body.

True

True or false? The lungs of humans form from the embryonic foregut.

True

Which of the following statements about blood circulation in the body is true?

Valves prevent the backflow of blood into the atria and ventricles.

Stroke occurs when _____.

a blood clot enters the cerebral circulation, blocking an artery and causing the death of brain tissue

Organisms with a circulating body fluid that is distinct from the fluid that directly surrounds the body's cells are likely to have _____.

a closed circulatory system

A normal event in the process of blood clotting is the _____.

activation of prothrombin to thrombin

Most carbon dioxide is carried from the body tissues to the lungs _____.

as bicarbonate ions (HCO3 -)

The smallest airway through which inspired air passes before gas exchange occurs in the mammalian lungs is the _____.

bronchiole

Which barrier(s) must O2O2 and CO2CO2 cross to pass between air and blood inside lungs?

capillary wall, extracellular fluid, epithelial cells

In the blood most of the oxygen that will be used in cellular respiration is carried from the lungs to the body tissues _____.

combined with hemoglobin

Most of the carbon dioxide produced by humans is _____.

converted to bicarbonate ions by an enzyme in red blood cells

Countercurrent exchange in the fish gill helps to maximize _____.

diffusion Submit

The only vertebrates in which blood flows directly from respiratory organs to body tissues without first returning to the heart are the _____.

fishes

To become bound to hemoglobin for transport in a mammal, atmospheric molecules of oxygen must cross _____.

five membranes-in and out of the cell lining the lung, in and out of the endothelial cell lining an alveolar capillary, and into the red blood cell-to bind with hemoglobin

In which of the following organisms does blood flow from the pulmocutaneous circulation to the heart before circulating through the rest of the body?

frogs

The greatest difference in the concentration of respiratory gases is found in which of the following pairs of mammalian blood vessels?

he pulmonary vein and the jugular vein

A decrease from pH 7.4 to pH 7.2 causes hemoglobin to _____.

increase its binding of H+

From the capillaries of the abdominal organs and hind limbs, blood flows to the _____.

inferior vena cava Submit

Voice sounds are produced by the _____.

larynx

From the pulmonary veins, blood flows to the _____.

left atrium

The primary functions of the _____ are to warm, filter, and humidify air.

nasal cavity

In an open circulatory system, blood is _____.

not always confined to blood vessels and is under lower pressure than in closed circulatory systems

The Bohr shift on the oxygen-hemoglobin dissociation curve is produced by changes in _____.

pH

Blood returns to the heart via the _____.

pulmonary veins

From the superior vena cava, blood flows to the _____.

right atrium

Which of the following develops the greatest pressure on the blood in the mammalian aorta?

systole of the left ventricle

If a molecule of carbon dioxide released into the blood in your left toe is exhaled from your nose, it must pass through all of the following EXCEPT _____.

the pulmonary vein

Circulatory systems compensate for _____.

the slow rate at which diffusion occurs over large distances

The velocity of blood flow is the lowest in capillaries because _____.

the total cross-sectional area of the capillaries is greater than the total cross-sectional area of the arteries or any other part of the circulatory system Submit

Which of the following is the correct sequence of blood flow in birds and mammals?

vena cava → right atrium → right ventricle pulmonary artery

Countercurrent exchange is evident in the flow of _____.

water across the gills of a fish and the blood within those gills

An advantage of gas exchange in fresh water, compared with gas exchange in air, is that _____.

water loss through evaporation across the respiratory surface can be minimizedventilation requires less energy in water