Problem 151 - Objective Biology for NEET

Question

Assertion: Large intestine also shows the presence of villi like small intestine. Reason: Absorption of most substance takes place in large intestine.

Step-by-Step Solution

Answer

The assertion and reason are both false. The large intestine does not have villi and absorption of most nutrients occurs in the small intestine, not the large intestine.

Step 1: Identify the Assertion

The given assertion is that the large intestine also shows the presence of villi, much like the small intestine. This claim has to be verified based on facts or evidence.

Step 2: Analyze The Assertion

The presence of villi in the small intestine is a confirmed fact. The villi increase surface area for absorption of nutrients. However, the large intestine primarily absorbs water and salts and not nutrients. Thus, there are no villi in the large intestine, which contradicts the given assertion.

Step 3: Examine The Reason

The provided reasoning was that absorption of most substances occurs in the large intestine. In reality, the absorption of most nutrients takes place in the small intestine, but it is in the large intestine where most of the residual water is absorbed along with some electrolytes and vitamins produced by enteric bacteria. The reason proposed is therefore not accurate.

Step 4: Combine Analyses

In conclusion, the assertion itself is false, as the large intestine does not have villi. Additionally, the reason provided is also incorrect, as most nutrients are absorbed in the small intestine not the large intestine. This leads to the conclusion that the assertion is false and reason is also false.

Key Concepts

Large Intestine

The large intestine is a crucial part of the digestive system, but it often gets overshadowed by the small intestine. The large intestine is responsible for absorbing water and electrolytes from the food remains. This process helps to form solid waste, which is eventually excreted from the body.
Contrary to what some may think, the large intestine does not contain villi. Villi are tiny, finger-like projections found in the small intestine. The absence of villi makes sense since the large intestine focuses more on absorbing water and salts rather than nutrients. This is an essential role as it helps to maintain the body's fluid balance.

• The large intestine consists of several parts, including the cecum, colon, rectum, and anal canal.
• It is also home to a large population of beneficial bacteria that assist in breaking down substances that the small intestine could not digest.
• Though it doesn't absorb nutrients like the small intestine, it plays a vital role in the final stages of digestion.

Villi

Villi are small, finger-like projections that line the inside of the small intestine. They play a critical role in absorbing nutrients from the food we eat. These structures increase the surface area of the intestine, allowing for more efficient absorption.
If you imagine the small intestine as a plush carpet, the villi would be the fibers standing up, capturing and funneling nutrients into the bloodstream.

• The increased surface area provided by villi is essential; without them, nutrient absorption would be significantly less efficient.
• Each individual villus contains blood vessels and a lacteal, a small lymphatic vessel, which transport absorbed nutrients throughout the body.
• This efficient system facilitates the uptake of essential nutrients, including amino acids, fatty acids, and simple sugars.

Nutrient Absorption

Nutrient absorption is one of the main functions of the small intestine and an essential part of the digestive process. Most nutrients from the food we eat are absorbed here due to the rich presence of villi and microvilli, which together vastly increase the surface area.
These nutrients then enter the bloodstream through the villi's blood vessels and travel to various parts of the body. This process ensures that our organs receive the necessary nutrients to function.

• Proteins are broken down into amino acids, fats into fatty acids and glycerol, and carbohydrates into simple sugars—all absorbed in the small intestine.
• Vitamins and minerals are absorbed here as well, supporting various bodily functions.
• The efficiency of nutrient absorption contributes to overall health and energy levels.

Small Intestine

The small intestine plays a central role in digestion and nutrient absorption. It is a long, coiled tube where most digestion and absorption of nutrients take place. Its lining consists of many folds, villi, and microvilli, which serve to maximize nutrient absorption.
Unlike the large intestine, the small intestine is teeming with these absorptive adaptations. It is divided into three sections: the duodenum, jejunum, and ileum, each having a unique role in digestion.

• The duodenum receives partially digested food from the stomach and secretions from the pancreas and gallbladder, which aid further digestion.
• The jejunum and ileum are primarily involved in absorbing nutrients into the bloodstream.
• These regions ensure that nutrients, vitamins, and minerals are efficiently taken up into the body, which is crucial for maintaining good health.