Human Anatomy and Physiology : Help with Gas Exchange

Study concepts, example questions & explanations for Human Anatomy and Physiology

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Example Questions

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Example Question #1 : Help With Gas Exchange

Which of the following factors determines the oxygen saturation of hemoglobin?

Possible Answers:

Height in the body

Speed of the hemoglobin in the blood

Oxygen partial pressure

Amount of air inhaled

Correct answer:

Oxygen partial pressure

Explanation:

Oxygen will attach to hemoglobin and be delivered to the body's tissues via gas exchange. In order to detach from hemoglobin, there needs to be a decrease in the partial pressure of oxygen. The oxygen pressure in the lungs is much higher than in the body. This is why oxygen attaches to hemoglobin in the lungs. As the hemoglobin goes to the body's tissues, oxygen pressure decreases. This causes the oxygen to detach and be diffused into the tissues.

Example Question #1 : Help With Gas Exchange

What is the most common way for carbon dioxide to be carried in the blood?

Possible Answers:

Attached to hemoglobin

As a bicarbonate ion

Free floating in the bloodstream

Attached to a protein

Correct answer:

As a bicarbonate ion

Explanation:

There are three main ways that carbon dioxide can be carried in the blood: it can be in solution independently, it can be turned into a bicarbonate ion via the enzyme carbonic anhydrase, or it can be attached to hemoglobin and other proteins. Carbon dioxide transport as bicarbonate ions is ten times more common than any other method.

In the lungs, the bicarbonate ion will undergo the reverse reaction experienced in the tissues, and dissociate into carbon dioxide and water. This allows the carbon dioxide gas to be exhaled.

Example Question #18 : Respiratory Physiology

As the carbon dioxide partial pressure increases, what will happen to hemoglobin's affinity for oxygen?

Possible Answers:

It will decrease

It will initially decrease, then increase

It depends on the temperature

It will stay the same

It will increase

Correct answer:

It will decrease

Explanation:

There are a few factors which can decrease the affinity of hemoglobin for oxygen: increased acidity, increased temperature, and carbon dioxide pressure. As carbon dioxide levels increase, hemoglobin's affinity for oxygen decreases. This means that it will release oxygen more readily in areas of high carbon dioxide levels, such as in the body's tissues. Since carbon dioxide is a product of cell metabolism, regions with high carbon dioxide content are likely very active in metabolism. This metabolism requires oxygen for the electron transport chain; thus, it is beneficial for hemoglobin to release oxygen in these regions in order to promote further metabolism.

Example Question #2 : Help With Gas Exchange

If an individual has a blood pH of 6.8, then they should __________.

Possible Answers:

breathe slower to maximize use of O2

eat more acidic foods

breathe slower to minimize loss of CO2

breathe faster to remove excess CO2

breathe faster to intake excess O2

Correct answer:

breathe faster to remove excess CO2

Explanation:

Normal blood pH is about 7.4 in most tissues (it is a bit lower in veins since they carry waste products, which are acidic). To get back to the physiological set point of pH = 7.4, we want to remove the acid from the blood. The major blood buffer system is shown in the following equation: 

As we know, carbon dioxide is one of the major byproducts of respiration, and is considered waste for our bodies. Combined with water and catalyzed by carbonic anhydrase, it is converted into carbonic acid. Carbonic acid is a weak acid and will partially dissociate into hydrogen ions and bicarbonate ions. Thus, overall, carbon dioxide and water yields acid (hydrogen ions). As a result, excess carbon dioxide in the blood will lower the pH.

In order to increase the pH, we must stop this equation from proceeding in the forward direction; thus, (remember Le Chatelier's principle) we must remove carbon dioxide from the left side. This will push the reaction in the reverse direction, quenching hydrogen ions (acid) and removing them from the blood, increasing blood pH back to normal.

Since we want to get rid of excess carbon dioxide, we breathe faster. Oxygen does not have any effect on blood pH. Furthermore, the atmospheric oxygen level (21%) is plenty for our bodies to utilize, as when we exhale there is about 15% oxygen left over, meaning we only use about 25% of the oxygen we breathe (this is why CPR works!).

Example Question #3 : Help With Gas Exchange

The lungs produces surfactant, which covers each alveolus; what is the function of surfactant?

Possible Answers:

Cleans the lungs

Relaxes the diaphragm

Increases oxygen levels

Decreases surface tension

Correct answer:

Decreases surface tension

Explanation:

Surfactant coats each alveolus, and is a detergent that lowers surface tension that prevents the alveolus from collapsing on itself. Also, decreasing surface tension facilitates the diffusion of gasses across the alveolar epithelium.

Example Question #4 : Help With Gas Exchange

A higher than normal concentration of __________ indicates cyanosis (a bluish color of the skin and mucous membranes).

Possible Answers:

adenosine triphosphate (ATP)

hydrogen ion

carbon monoxide

carbon dioxide

reduced hemoglobin

Correct answer:

reduced hemoglobin

Explanation:

Cyanosis in the body occurs due a reduced hemoglobin concentration that is at least 6-8 grams of hemoglobin per deciliter of blood lower than the normal hemoglobin range for men and women.

Hemoglobin is what carries oxygen in the blood. The blood then carries this oxygen to various tissues in the body. When hemoglobin is low, oxygen is not delivered fast and efficiently enough to the appropriate tissues of the body, thus turning them visibly blue (cyanosis). 

Example Question #5 : Help With Gas Exchange

A man who has a residual lung volume of 2.5 liters has a value that is __________.

Possible Answers:

within the normal range

just barely below normal

above normal

below normal

just barely above normal

Correct answer:

above normal

Explanation:

The man has above normal residual lung volume , as the normal residual volume (RV) for an adult male of average size is 1.2 liters. Causes for such high residual lung volumes in a man can occur from lung diseases, such as emphysema, that cause obstruction of the lungs and trapping of air. 

Example Question #6 : Help With Gas Exchange

In which of the following places is the partial pressure of carbon dioxide the highest?

Possible Answers:

Systemic arterial blood

Alveolar gas

Systemic venous blood

Exhaled gas

The same in all of the places listed

Correct answer:

Systemic venous blood

Explanation:

The partial pressure of carbon dioxide would be the highest in systemic venous blood. This is because the systemic venous blood contains both the carbon dioxide that was in the systemic arterial blood and that which is added to the blood by tissue metabolism as the blood passes through the systemic capillaries.

Example Question #7 : Help With Gas Exchange

For a person who is at rest, an oxyhemoglobin saturation of mixed systemic venous blood of 25% is __________.

Possible Answers:

much below normal

within the normal range

much above normal

slightly below normal

slightly above normal

Correct answer:

much below normal

Explanation:

The normal oxyhemoglobin concentration in mixed systemic venous blood for a person at rest is 75%. Therefore, a person with a oxyhemoglobin concentration of 25% is much below normal.

Example Question #8 : Help With Gas Exchange

IRV (inspiratory reserve volume), TV (tidal volume), ERV (expiratory reserve volume), RV (residual volume)

The total lung capacity (TLC) is equal to which of the following?

Possible Answers:

IRV + TV + ERV + RV

IRV + TV

IRV + TV + ERV

TV + ERV

IRV + ERV

Correct answer:

IRV + TV + ERV + RV

Explanation:

The total lung capacity (TLC) = IRV (inspiratory reserve volume) + TV (tidal volume) + ERV (expiratory reserve volume) + RV (residual volume).

The total lung capacity (TLC ) is the maximum volume of gas present in the lungs after a maximal inspiration. It includes all of the possible lung volumes.

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