What is the difference between pulmonary ventilation and external respiration

This will cause oxygen to enter and carbon dioxide to leave the blood more quickly. Two important aspects of gas exchange in the lung are ventilation and perfusion. Ventilation is the movement of air into and out of the lungs, and perfusion is the flow of blood in the pulmonary capillaries. For gas exchange to be efficient, the volumes involved in ventilation and perfusion should be compatible.

However, factors such as regional gravity effects on blood, blocked alveolar ducts, or disease can cause ventilation and perfusion to be imbalanced. The partial pressure of oxygen in alveolar air is about mm Hg, whereas the partial pressure of the oxygenated pulmonary venous blood is about mm Hg. When ventilation is sufficient, oxygen enters the alveoli at a high rate, and the partial pressure of oxygen in the alveoli remains high. In contrast, when ventilation is insufficient, the partial pressure of oxygen in the alveoli drops.

Without the large difference in partial pressure between the alveoli and the blood, oxygen does not diffuse efficiently across the respiratory membrane. The body has mechanisms that counteract this problem. In cases when ventilation is not sufficient for an alveolus, the body redirects blood flow to alveoli that are receiving sufficient ventilation.

This is achieved by constricting the pulmonary arterioles that serves the dysfunctional alveolus, which redirects blood to other alveoli that have sufficient ventilation.

At the same time, the pulmonary arterioles that serve alveoli receiving sufficient ventilation vasodilate, which brings in greater blood flow. Factors such as carbon dioxide, oxygen, and pH levels can all serve as stimuli for adjusting blood flow in the capillary networks associated with the alveoli.

Ventilation is regulated by the diameter of the airways, whereas perfusion is regulated by the diameter of the blood vessels. The diameter of the bronchioles is sensitive to the partial pressure of carbon dioxide in the alveoli. A greater partial pressure of carbon dioxide in the alveoli causes the bronchioles to increase their diameter as will a decreased level of oxygen in the blood supply, allowing carbon dioxide to be exhaled from the body at a greater rate. As mentioned above, a greater partial pressure of oxygen in the alveoli causes the pulmonary arterioles to dilate, increasing blood flow.

Gas exchange occurs at two sites in the body: in the lungs, where oxygen is picked up and carbon dioxide is released at the respiratory membrane, and at the tissues, where oxygen is released and carbon dioxide is picked up. External respiration is the exchange of gases with the external environment, and occurs in the alveoli of the lungs. Internal respiration is the exchange of gases with the internal environment, and occurs in the tissues.

The actual exchange of gases occurs due to simple diffusion. Energy is not required to move oxygen or carbon dioxide across membranes. Instead, these gases follow pressure gradients that allow them to diffuse. The anatomy of the lung maximizes the diffusion of gases: The respiratory membrane is highly permeable to gases; the respiratory and blood capillary membranes are very thin; and there is a large surface area throughout the lungs. The pulmonary artery carries deoxygenated blood into the lungs from the heart, where it branches and eventually becomes the capillary network composed of pulmonary capillaries.

These pulmonary capillaries create the respiratory membrane with the alveoli. As the blood is pumped through this capillary network, gas exchange occurs. Although a small amount of the oxygen is able to dissolve directly into plasma from the alveoli, most of the oxygen is picked up by erythrocytes red blood cells and binds to a protein called hemoglobin, a process described later in this chapter.

Oxygenated hemoglobin is red, causing the overall appearance of bright red oxygenated blood, which returns to the heart through the pulmonary veins. Carbon dioxide is released in the opposite direction of oxygen, from the blood to the alveoli.

Some of the carbon dioxide is returned on hemoglobin, but can also be dissolved in plasma or is present as a converted form, also explained in greater detail later in this chapter.

The intercostal nerves that stimulate these muscles originate from the spinal cord thoracic nerves Inhalation is initiated as the dome-shaped diaphragm is stimulated. As it contracts and flattens, the thorax expands inferiorly.

The internal and innermost intercostal muscles relax, while the external intercostal muscles contract from stimulus by the thoracic nerves. This produces an upward and outward movement of the ribs similar to the movement of a bucket handle , and the sternum similar to when pulling upward on a handle of a water pump.

The fluid in the pleural cavity acts like glue, adhering the thorax to the lungs. Hence, as the thorax expands vertically and laterally, the parietal layer drags the visceral layer along with it, causing the lungs to expand. Adequate expansion of the lungs results in a decreased pressure within the alveoli. Therefore, when the alveolar pressure drops below atmospheric pressure, air rushes into the lungs.

Remember, inhalation requires a stimulus initiated from the central nervous system. Think of it like turning on a light. The light stays unlit until you flip a switch CNS , releasing electricity and stimulating the components of the light bulb.

As long as the switch is on and there is an impulse, the light stays lit. However, if you turn off the switch, the stimulus ceases, and the light shuts down. Exhalation is akin to turning off the switch, so to speak.

Thoracic stretch receptors constantly monitor chest expansion. Consequently, the diaphragm and the external intercostal muscles relax, decreasing the thoracic volume — like letting air out of a balloon. Assisting with this passive process, the internal and innermost intercostal muscles are stimulated. Their contraction pulls the ribcage and attached pleura further downward and inward, compressing the lungs and increasing the air pressure within the alveoli.

Once the alveolar pressure exceeds the atmospheric pressure, air moves out of the lungs. That is all there is to it — simple, right? Adults normally ventilate between 12 to 20 times per minute, thanks to the autonomic nervous system. We do not even have to think about it! Nonetheless, what becomes a problem and why EMS gets a call is when the nervous system, the thoracic musculature, or the lungs become diseased or disabled. Here is a partial list of pathologies that impair ventilation:.

Respiration is the movement of gas across a membrane. The gas exchange in the lungs is referred to as external respiration. The very thin membrane gas crosses is called the respiratory membrane, separating the air within the alveoli from the blood within pulmonary capillaries. As the volume of the lungs increases, air pressure drops and air rushes in. During normal exhalation, the muscles relax. The lungs become smaller, the air pressure rises, and air is expelled.

Inside the lungs, oxygen is exchanged for carbon dioxide waste through the process called external respiration. This respiratory process takes place through hundreds of millions of microscopic sacs called alveoli. Oxygen from inhaled air diffuses from the alveoli into pulmonary capillaries surrounding them. It binds to hemoglobin molecules in red blood cells, and is pumped through the bloodstream.

Meanwhile, carbon dioxide from deoxygenated blood diffuses from the capillaries into the alveoli, and is expelled through exhalation.

The bloodstream delivers oxygen to cells and removes waste carbon dioxide through internal respiration, another key function of the respiratory system. In this respiratory process, red blood cells carry oxygen absorbed from the lungs around the body, through the vasculature.

When oxygenated blood reaches the narrow capillaries, the red blood cells release the oxygen. This is no surprise, as gas exchange removes oxygen from and adds carbon dioxide to alveolar air. Both deep and forced breathing cause the alveolar air composition to be changed more rapidly than during quiet breathing. As a result, the partial pressures of oxygen and carbon dioxide change, affecting the diffusion process that moves these materials across the membrane.

This will cause oxygen to enter and carbon dioxide to leave the blood more quickly. Two important aspects of gas exchange in the lung are ventilation and perfusion. Ventilation is the movement of air into and out of the lungs, and perfusion is the flow of blood in the pulmonary capillaries.

For gas exchange to be efficient, the volumes involved in ventilation and perfusion should be compatible. However, factors such as regional gravity effects on blood, blocked alveolar ducts, or disease can cause ventilation and perfusion to be imbalanced.

The partial pressure of oxygen in alveolar air is about mm Hg, whereas the partial pressure of oxygenated blood in pulmonary veins is about mm Hg.

When ventilation is sufficient, oxygen enters the alveoli at a high rate, and the partial pressure of oxygen in the alveoli remains high. In contrast, when ventilation is insufficient, the partial pressure of oxygen in the alveoli drops. Without the large difference in partial pressure between the alveoli and the blood, oxygen does not diffuse efficiently across the respiratory membrane. The body has mechanisms that counteract this problem.

In cases when ventilation is not sufficient for an alveolus, the body redirects blood flow to alveoli that are receiving sufficient ventilation. This is achieved by constricting the pulmonary arterioles that serves the dysfunctional alveolus, which redirects blood to other alveoli that have sufficient ventilation.

At the same time, the pulmonary arterioles that serve alveoli receiving sufficient ventilation vasodilate, which brings in greater blood flow. Factors such as carbon dioxide, oxygen, and pH levels can all serve as stimuli for adjusting blood flow in the capillary networks associated with the alveoli. Ventilation is regulated by the diameter of the airways, whereas perfusion is regulated by the diameter of the blood vessels. The diameter of the bronchioles is sensitive to the partial pressure of carbon dioxide in the alveoli.

A greater partial pressure of carbon dioxide in the alveoli causes the bronchioles to increase their diameter as will a decreased level of oxygen in the blood supply, allowing carbon dioxide to be exhaled from the body at a greater rate. As mentioned above, a greater partial pressure of oxygen in the alveoli causes the pulmonary arterioles to dilate, increasing blood flow. Gas exchange occurs at two sites in the body: in the lungs, where oxygen is picked up and carbon dioxide is released at the respiratory membrane, and at the tissues, where oxygen is released and carbon dioxide is picked up.

External respiration is the exchange of gases with the external environment, and occurs in the alveoli of the lungs. Internal respiration is the exchange of gases with the internal environment, and occurs in the tissues. The actual exchange of gases occurs due to simple diffusion. Energy is not required to move oxygen or carbon dioxide across membranes.

Instead, these gases follow pressure gradients that allow them to diffuse. The anatomy of the lung maximizes the diffusion of gases: The respiratory membrane is highly permeable to gases; the respiratory and blood capillary membranes are very thin; and there is a large surface area throughout the lungs.

The pulmonary artery carries deoxygenated blood into the lungs from the heart, where it branches and eventually becomes the capillary network composed of pulmonary capillaries. These pulmonary capillaries create the respiratory membrane with the alveoli Figure 2. As the blood is pumped through this capillary network, gas exchange occurs. Although a small amount of the oxygen is able to dissolve directly into plasma from the alveoli, most of the oxygen is picked up by erythrocytes red blood cells and binds to a protein called hemoglobin, a process described later in this chapter.

Oxygenated hemoglobin is red, causing the overall appearance of bright red oxygenated blood, which returns to the heart through the pulmonary veins. Carbon dioxide is released in the opposite direction of oxygen, from the blood to the alveoli.

Some of the carbon dioxide is returned on hemoglobin, but can also be dissolved in plasma or is present as a converted form, also explained in greater detail later in this chapter. External respiration occurs as a function of partial pressure differences in oxygen and carbon dioxide between the alveoli and the blood in the pulmonary capillaries. Figure 2: In external respiration, oxygen diffuses across the respiratory membrane from the alveolus to the capillary, whereas carbon dioxide diffuses out of the capillary into the alveolus.