The small intestineThe small intestine is a long, narrow tube in the digestive system where most of the digestion and absorption of nutrients occurs. It consists of three sections: the duodenum, jejunum, and ileum. Enzymes from the pancreas and bile from the liver aid in breaking down food, allowing nutrient absorption into the bloodstream. is uniquely designed to maximize the absorption of digested food. Its structure and features are specialized to efficiently absorb nutrients and water from the food we eat. Key aspects of this design include:

Large Surface Area

Villi and Microvilli: The inner surface of the small intestine is lined with millions of tiny, finger-like projections called villi. Each villus is covered with even smaller hair-like structures called microvilli, forming a brush border. This dramatically increases the surface area for absorption.

Increased Surface Area: The presence of villi and microvilli enlarges the surface area of the small intestine’s lining by several folds, allowing for more efficient nutrient absorption.

Rich Blood Supply

Capillary Networks: Each villus contains a dense network of capillaries (tiny blood vessels). This close proximity to the absorbed nutrients allows for quick and efficient transfer of nutrients into the bloodstream.
Lacteals: In addition to blood capillaries, each villus contains a lymphatic vessel called a lacteal. Lacteals absorb dietary fats and fat-soluble vitamins, which are then transported via the lymphatic system.

Digestive Enzymes

The brush border of the microvilli produces various enzymes that play a role in the final stages of carbohydrate and protein digestion. These enzymes help break down nutrients into their simplest forms right at the absorption site.

Selective Permeability:
The cells of the intestinal wall selectively allow digested nutrients to pass through into the bloodstream. This selective permeability is crucial for regulating the absorption of different substances.

Movement and Mixing

Peristalsis: Wave-like muscle contractions, known as peristalsis, move the food along the intestine, aiding in its mixing and contact with the absorptive surfaces.
Segmentation: This is a type of intestinal movement that mixes the chyme (partially digested food) and increases its contact with the intestinal wall.

Optimal pH and Enzymatic Environment:
The small intestine maintains an optimal pH and enzymatic environment for digestive enzymes to function effectively, further aiding in the breakdown and absorption of nutrients.

Transport Mechanisms

The cells in the small intestine use various transport mechanisms, including passive diffusion, facilitated diffusion, active transport, and endocytosis, to absorb different nutrients.

Through these structural and functional adaptations, the small intestine efficiently absorbs carbohydrates, proteins, fats, vitamins, minerals, and water, ensuring that the body receives the necessary nutrients from the food consumed.

Discuss this question in detail or visit to Class 10 Science Chapter 5 for all questions.
List of Questions of Class 10 Science Chapter 5

Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans?
What criteria do we use to decide whether something is alive?
What are outside raw materials used for by an organism?
What processes would you consider essential for maintaining life?
What are the differences between autotrophic nutrition and heterotrophic nutrition?
Where do plants get each of the raw materials required for photosynthesis?
What is the role of the acid in our stomach?
What is the function of digestive enzymes?
How is the small intestine designed to absorb digested food?
What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
What are the different ways in which glucose is oxidised to provide energy in various organisms?
How is oxygen and carbon dioxide transported in human beings?
How are the lungs designed in human beings to maximise the area for exchange of gases?
What are the components of the transport system in human beings?
Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
What are the components of the transport system in highly organised plants?
How are water and minerals transported in plants?
How is food transported in plants?
Describe the structure and functioning of nephrons.
What are the methods used by plants to get rid of excretory products?
How is the amount of urine produced regulated?
How are fats digested in our bodies? Where does this process take place?
What is the role of saliva in the digestion of food?
What are the necessary conditions for autotrophic nutrition and what are its byproducts?
What are the differences between aerobic and anaerobic respiration?
How are the alveoli designed to maximise the exchange of gases?
What would be the consequences of a deficiency of haemoglobin in our bodies?
Describe double circulation of blood in human beings. Why is it necessary?
What are the differences between the transport of materials in xylem and phloem?
Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.

Last Edited: November 16, 2023