Gas Exchange

The partial pressure of oxygen of alveolar air is 104 mmHg. At rest the oxygen poor blood entering the capillaries has a partial pressure of oxygen of 40 mmHg. During external respiration there is a net diffusion of oxygen along its partial pressure gradient, from the alveolus into the blood, until equilibrium is reached. As this occurs, the partial pressure of oxygen of the blood is increased to... ?

104 mmHg

The partial pressure of CO2 of the alveolar air is 40 mmHg. At rest, the partial pressure of CO2 of the blood entering the capillaries is 45 mmHg. During external respiration, CO2 diffuses along its partial pressure gradient, from the blood into the alveolus, until equilibrium is reached. As blood flows past the alveolus, the partial pressure of CO2 is decreases to ...?

40 mmHg

The pressure of O2 of the blood entering the systemic capillaries is 100 mmHg. During internal respiration, there is a net diffusion of oxygen along its partial pressure gradient, from the blood into the tissues, until equilibrium is reached. As this occurs, the pressure of O2 of the blood decreases to ...?

40 mmHg

During internal respiration, CO2 diffuses along its partial pressure gradient until equilibrium is reached. As blood flows through the systemic capillaries, the pressure of CO2 increases to ...?

45 mmHg

Where do both internal and external respiration occur? What happens to oxygen and carbon dioxide during both?

Internal - occurs within the tissues; oxygen diffuses from the capillaries into the cells and carbon dioxide diffuses from the cells into the capillaries ; external - occurs within the lungs; oxygen diffuses from the alveoli into the pulmonary capillaries and carbon dioxide diffuses from the capillaries into the alveoli

How does the pressure of O2 and CO2 change as it travels from the alveoli to the systemic arteries to the systemic veins?

O2 changes from 105 to 100 to 40 mmHg. CO2 changes from 40 to 40 to 45 mmHg.

How do bronchioles respond to levels of blood gases?

When airflow through a bronchiole is less than normal, CO2 rises, which causes the bronchioles to dilate in order to remove the excess CO2. When airflow is high, CO2 drops, which causes the bronchioles to constrict, reducing airflow so that it is proportional to local blood flow

If you have 2 closed containers of water and gas at the same pressure and 1 container contains oxygen and the other contains carbon dioxide, which will dissolve to a greater extent?

carbon dioxide

The PCO2 of the blood entering the systemic capillaries is about 40 mmHg. At rest, the PCO2 of the blood leaving the systemic capillaries is about 45 mmHg. As blood flow through the systemic capillaries, the PCO2 increases or decreases?

decreases

The partial pressure of CO2 of the alveolar air is 40 mmHg. At rest the partial pressure of CO2 of the blood entering the capillaries is 45 mmHg. As blood flows past the alveolus, the partial pressure of CO2 increases or decreases?

decreases

The partial pressure of O2 in the blood entering the systemic capillaries is 100 mmHg. As blood flows through them, the pressure of oxygen increases or decreases?

decreases

What 3 factors account for the differences in the partial pressures in the alveoli from those in the atmosphere?

humidification of inhaled air, gas exchange between the alveoli and capillaries, and mixing of new and old air

What is Dalton's Law of Partial Pressures?

in a mixture of gases, the total pressure equals the sum of the partial pressures exerted by each gas

The partial pressure of CO2 of the blood entering the systemic capillaries is 40 mmHg. As blood flows through them, the pressure of CO2 increases or decreases?

increases

The partial pressure of oxygen in alveolar air is 104 mmHg. At rest, the oxygen poor blood entering the pulmonary capillaries as a partial pressure of oxygen of 40 mmHg. As blood flow passes the alveolus, the partial pressure of oxygen increases or decreases?

increases

In a container containing water and oxygen gas, some of the oxygen dissolves in the water. When equilibrium is reached, the pressure of the oxygen gas above the water is .... to the pressure of oxygen in the liquid.

is equal to

In a container containing water and oxygen gas, some of the oxygen dissolves in the water. When equilibrium is reached, the rate of oxygen gas diffusing into the water is ... to the rate of oxygen gas diffusing out of the water.

is equal to

As altitude increases, what happens to the atm. pressure?

it decreases, fewer oxygen molecules are present

As air travels through the respiratory passageways to the alveoli, it is humidified, picking up water molecules. What effect does this have on the partial pressure of water?

it increases

Explain how ventilation-perfusion coupling facilitates efficient gas exchange.

it maintains alveolar airflow so it is proportional to pulmonary capillary blood flow

What 2 factors account for the surface area and structure of the respiratory membrane allowing for efficient external respiration?

millions of alveoli and the thinness of the membrane

In a container containing water and oxygen, if you increase the pressure in the container, will more or less oxygen molecules dissolve in the liquid?

more

Do the alveoli completely empty between breaths?

no, so there is a mixing of new and old air

What four gases are found in the atmosphere?

oxygen, carbon dioxide, nitrogen, and water

Why does CO2 have a smaller partial pressure gradient than O2?

since CO2 is very soluble in blood, a larger number of molecules diffuse along the pressure gradient. O2 is less soluble, so it needs a larger concentration gradient to provide sufficient O2 to the body

Henry's Law states -

the amount of gas which dissolves in a liquid is proportional to the solubility and partial pressure of that gas

As gases are exchanged between the alveoli and pulmonary capillaries, what happens to the partial pressures of both gases?

the both change

Efficient external respiration depends on what 3 factors?

the surface area and structure of the respiratory membrane, the partial pressure gradients between the alveoli and capillaries, and efficient gas exchange requiring matching alveolar airflow to pulmonary capillary blood flow

What factor causes vasoconstriction and vasodilation associated with ventilation-perfusion coupling?

when airflow through a bronchiole is restricted, there is low O2, which causes the arterioles to vasoconstrict. High airflow regions have high O2, which causes them to vasodilate

During external respiration, oxygen equilibrium is reached within .... of the pulmonary capillary?

within the 1st third

During external respiration, CO2 equilibrium is reached within the ... of the capillary.

within the first four-tenths