In the human digestive system, which organ has numerous finger like projections called villi (singular: villus) that greatly increase the surface area for absorption of digested food?

Introduction / Context:
The human digestive system is specialized not only for breaking down food but also for efficiently absorbing nutrients into the bloodstream. To maximize absorption, certain regions of the gut have structural adaptations that increase surface area. One of the most important of these adaptations is the presence of tiny finger like projections called villi in a particular part of the intestine. This question tests whether you can correctly identify the organ that contains villi and understand their role in digestion and absorption.

Given Data / Assumptions:

• The question mentions finger like outgrowths called villi (singular villus).
• These structures increase surface area and are associated with absorption.
• The options list various organs including large intestine, bladder, small intestine, stomach, and oesophagus.
• We assume basic knowledge of the structure of the intestinal wall.

Concept / Approach:
The small intestine is the primary site of digestion and absorption of nutrients in humans. Its inner lining is thrown into folds, which bear numerous villi. Each villus is covered by epithelial cells and contains a network of capillaries and a lacteal for fat absorption. These villi greatly increase the surface area available for absorption of amino acids, simple sugars, fatty acids, and glycerol. The large intestine, in contrast, mainly absorbs water and minerals and does not possess villi in the same prominent way. The stomach and oesophagus are not major sites of nutrient absorption and also lack such villi.

Step-by-Step Solution:
Step 1: Identify villi as finger like projections that increase the surface area of the intestinal lining. Step 2: Recall that the small intestine, especially the jejunum and ileum, has abundant villi and microvilli. Step 3: Understand that these structures help in the absorption of digested nutrients into blood and lymph. Step 4: Compare the options and select the organ known to be the main site of nutrient absorption. Step 5: Reject organs such as bladder and oesophagus which have unrelated functions.

Verification / Alternative check:
Visualizing a textbook diagram of the small intestine wall helps in verification. Such diagrams commonly show folds, villi, and microvilli forming a brush border. Labels usually point to the presence of blood capillaries and a lacteal inside each villus. In contrast, diagrams of the large intestine show a smoother inner surface with no such villi, and the bladder is drawn as a muscular sac with a simple lining. These visual memories from diagrams support the conclusion that the small intestine is the correct organ.

Why Other Options Are Wrong:
Large intestine, mainly responsible for water absorption: Although it absorbs water and minerals, it does not have the dense villi that are characteristic of the small intestine. Urinary bladder, storing urine temporarily: The bladder is part of the excretory system, not involved in food digestion or absorption. Stomach, which mainly performs mechanical and chemical digestion: The stomach has folds called rugae, but these are not villi, and nutrient absorption there is limited. Oesophagus, which transports food from mouth to stomach: The oesophagus is a muscular tube for food transport and lacks villi.

Common Pitfalls:
A common mistake is to confuse the small and large intestine because both are parts of the intestinal tract. Remember that most nutrient absorption occurs in the small intestine, which is why it is specially adapted with villi and microvilli. Another confusion may arise from thinking that any folded structure inside the digestive tract counts as villi. It is important to distinguish between large folds (plicae circulares) and the fine finger like villi that are unique features of the small intestine lining.

Final Answer:
Therefore, the organ that has finger like outgrowths called villi for efficient absorption of digested food is the Small intestine, with villi for nutrient absorption.