Question

What is External respiration?
A) Respiration in skin cells
B) Gaseous exchange between organism and external environment
C) Gaseous exchange between cells and tissue fluid
D) Both B and C

Answer 1

Hint: For external respiration to occur there has to be an “external” environment for the organism to interact with, along with a layer of diffusion.

Complete answer:
1) External respiration simply consists of the bulk flow of air into and out of the lungs of the organism and the transfer of oxygen and carbon dioxide into its blood through diffusion.
2) In the case of respiration in skin cells (also known as cutaneous respiration) comprises gas exchange occurring across the skin (or outer integument as in some species) of an organism rather than the use of gills or lungs.
3) Gaseous exchange between organism and external environment is simply the meaning of external respiration as external respiration describes the exchange of gasses between the external environment and the bloodstream of the organism, using a process called diffusion which occurs when there is a pressure gradient across the alveolar tissue in the lungs of the organism.
4)Gaseous exchange between cells and tissue fluid is termed as internal respiration, simply because there is not any interaction with the external environment. Internal respiration involves gas exchange between the bloodstream and tissues, and cellular respiration. Gas exchange in tissues is a result of tissue surface area, gas partial pressure gradients, and the blood vessels of those tissues.
5) As gaseous exchange between cells and tissue fluid is internal respiration and is different from the process of external respiration, option D becomes invalid.

Thus, the correct answer is option B (Gaseous exchange between organism and external environment).

Note:Presence of partial pressure gradients allow gasses to flow from areas of high pressure to areas of lower pressure. Ventilation of air in the alveoli must be balanced to maintain efficient gas exchange between the organism and the environment.