Question

Alveoli and villi both increases :

• A. Surface area for absorption
• B. Surface tension for assimilation
• C. Mean area for adsorption
• D. None of the above

Hint:

Think of highly folded structures in biology:
{Alveoli} (in lungs): Millions of tiny sacs \(\rightarrow\) Huge surface area for O\(_2\) / CO\(_2\) exchange (absorption/release of gases).
{Villi} (in small intestine): Many finger-like projections \(\rightarrow\) Huge surface area for absorption of digested food. The common theme is a massive {increase in surface area} to make absorption processes very efficient.

Answer 1

The Correct Option is A

Concept: Alveoli and villi are specialized biological structures found in different organ systems. Despite their different locations and primary functions, they share a common structural adaptation that enhances their efficiency. Step 1: Understanding Alveoli
Location: Alveoli (singular: alveolus) are tiny air sacs in the lungs.
Function: They are the primary sites of gas exchange (oxygen into the blood, carbon dioxide out of the blood).
Structure: Millions of alveoli provide an enormous surface area within the lungs, facilitating efficient diffusion of gases. Their walls are very thin (one cell thick). Step 2: Understanding Villi
Location: Villi (singular: villus) are small, finger-like projections that line the inner surface of the small intestine.
Function: They are primarily involved in the absorption of digested nutrients (like glucose, amino acids, fatty acids) from the small intestine into the bloodstream and lymphatic system.
Structure: The presence of numerous villi (and even smaller microvilli on the surface of villus cells) vastly increases the surface area of the small intestine available for nutrient absorption. Step 3: Identifying the common feature enhanced by both structures Both alveoli and villi are highly folded or branched structures. This intricate folding serves a common purpose: to increase the surface area available for their respective functions.
Alveoli increase the surface area for gas absorption (oxygen) and release (carbon dioxide).
Villi increase the surface area for nutrient absorption. So, the commonality is the increase in surface area, primarily for absorption processes. Step 4: Analyzing the options
(1) Surface area for absorption: Correct. Both structures significantly increase the surface area available for absorption (gases for alveoli, nutrients for villi).
(2) Surface tension for assimilation: Surface tension is a property of liquids. While important at interfaces, increasing surface tension is not the primary role of these structures. Assimilation is the process of incorporating absorbed nutrients into the body's cells, which occurs after absorption.
(3) Mean area for adsorption: Adsorption is the adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to a surface. While related to surface phenomena, "absorption" (taking in substances into the bulk) is more appropriate for the primary functions of alveoli and villi. "Mean area" is also not the direct feature increased; it's the total effective surface area.
(4) None of the above: Incorrect. Therefore, alveoli and villi both function to increase the surface area for absorption.