Differentiate between external respiration and internal respiration.

External respiration and internal respiration are two processes involved in the exchange of gases in living organisms, specifically in the respiratory system. While they are interconnected, they occur in different locations and serve distinct functions. Here's a differentiation between external respiration and internal respiration:

External Respiration:

Definition: External respiration refers to the exchange of gases (specifically oxygen and carbon dioxide) between the external environment and the body's respiratory system.
Location: It occurs in the respiratory organs, primarily in the lungs of terrestrial animals and gills of aquatic organisms.
Process: During external respiration, oxygen is taken in from the external environment (air or water) and transported to the lungs/gills. Carbon dioxide, produced as a waste product during cellular respiration, is expelled from the lungs/gills to the external environment.
Mechanism: In the lungs, oxygen diffuses from the alveoli (small air sacs) into the blood capillaries, where it binds with hemoglobin in red blood cells for transport. At the same time, carbon dioxide is released from the blood into the alveoli and then expelled during exhalation. In gills, oxygen is absorbed from water through specialized structures, while carbon dioxide is released into the water.
Purpose: The main goal of external respiration is to replenish oxygen levels in the body and remove carbon dioxide, facilitating gas exchange with the environment.
Internal Respiration:

Definition: Internal respiration refers to the exchange of gases between the blood and the body's tissues at the cellular level.
Location: It occurs in the systemic capillaries throughout the body.
Process: After oxygen is transported from the lungs/gills to the body tissues via the bloodstream, internal respiration takes place. Oxygen diffuses from the blood capillaries into the cells, where it is utilized for cellular respiration, producing energy. Simultaneously, carbon dioxide, generated as a byproduct, moves from the cells into the blood capillaries.
Mechanism: In internal respiration, oxygen diffuses from the high partial pressure in the blood to the lower partial pressure in the tissues, allowing oxygen to enter the cells. Carbon dioxide follows the opposite path, diffusing from the higher partial pressure in the cells to the lower partial pressure in the blood, enabling its transport back to the lungs for elimination.
Purpose: Internal respiration provides oxygen to the cells for energy production (cellular respiration) and removes carbon dioxide, allowing waste elimination.
In summary, external respiration occurs in the lungs/gills and involves the exchange of gases between the external environment and the respiratory system. Internal respiration takes place in the systemic capillaries and involves the exchange of gases between the blood and the body's tissues at the cellular level.