External respiration

Definition

External respiration refers to the process of gas exchange between the atmosphere and the blood in the lungs. This process involves inhalation of oxygen into the alveoli, where it diffuses into the blood, and the exhalation of carbon dioxide from the blood into the alveoli, allowing it to be expelled from the body. This crucial mechanism ensures that oxygen is available for cellular metabolism and that carbon dioxide, a waste product, is removed from the bloodstream.

5 Must Know Facts For Your Next Test

1. External respiration takes place in the alveoli, where oxygen enters the bloodstream and carbon dioxide is released into the air sacs.
2. The process is driven by differences in partial pressure; oxygen moves from areas of higher concentration in the alveoli to lower concentration in the blood.
3. Carbon dioxide moves in the opposite direction, from areas of higher concentration in the blood to lower concentration in the alveoli.
4. Efficient external respiration is vital for maintaining proper blood pH levels, as it helps regulate carbon dioxide concentrations.
5. Factors such as lung surface area, thickness of alveolar membranes, and ventilation-perfusion matching significantly affect the efficiency of external respiration.

Review Questions

• How does the structure of alveoli facilitate external respiration?
  • Alveoli are structured as tiny air sacs with thin walls that maximize surface area for gas exchange. The large surface area allows for efficient diffusion of oxygen into the blood and carbon dioxide out of it. The thin walls help minimize the distance gases must travel, facilitating quick and effective gas exchange during external respiration.
• Discuss the role of hemoglobin in external respiration and how it affects oxygen transport.
  • Hemoglobin plays a critical role in external respiration by binding to oxygen molecules in the lungs and transporting them through the bloodstream to tissues. When oxygen diffuses into red blood cells at high concentrations in the lungs, hemoglobin quickly binds to it, forming oxyhemoglobin. This process allows for efficient delivery of oxygen to tissues that need it while facilitating carbon dioxide transport back to the lungs for exhalation.
• Evaluate how changes in partial pressure can impact external respiration and overall respiratory efficiency.
  • Changes in partial pressure can significantly influence external respiration. For instance, if atmospheric pressure decreases or if there are high altitudes, the partial pressure of oxygen also decreases, resulting in less oxygen available for diffusion into the blood. Conversely, if carbon dioxide levels increase in the bloodstream, its higher partial pressure can lead to inefficient removal during exhalation. These changes can affect overall respiratory efficiency and impact oxygen delivery to tissues.

Related terms

alveoli:

Tiny air sacs in the lungs where gas exchange occurs, providing a large surface area for oxygen and carbon dioxide to diffuse.

hemoglobin:

A protein in red blood cells that binds to oxygen and transports it from the lungs to tissues throughout the body.

partial pressure: The pressure exerted by a specific gas in a mixture of gases, important for understanding how gases diffuse during external respiration.