Absorption Revision Notes

The small intestine follows the stomach in the digestive system.

Its primary role is to absorb nutrients from digested food into the body.

• Main site of nutrient absorption.
• Connects stomach to large intestine.

The inner surface of the small intestine has many folds and finger-like projections called villi.

Each villus is covered with microvilli, increasing surface area to maximize absorption.

• Villi and microvilli increase surface area.
• Large surface area allows efficient nutrient uptake.

Nutrients absorbed include glucose, amino acids, fatty acids, vitamins, and minerals.

These nutrients pass through the intestinal wall into the blood or lymphatic system for transport.

• Sugars and amino acids enter blood capillaries.
• Fatty acids and glycerol enter lymph vessels.

The small intestine absorbs the majority of water from digested food and digestive juices.

Its large surface area due to villi and microvilli allows efficient water uptake into the bloodstream.

• Most water absorption occurs here.
• Supports nutrient absorption by dissolving nutrients.

The colon (large intestine) absorbs some water from remaining waste material.

This absorption helps solidify feces before excretion.

• Colon absorbs less water than small intestine.
• Important for forming solid waste.

Water absorption maintains body hydration and fluid balance.

Poor absorption can lead to dehydration or diarrhea.

• Essential for health and digestion.
• Prevents excessive water loss.

Villi are small finger-like projections lining the small intestine.

Each villus is covered with even smaller projections called microvilli, resembling tiny hairs.

• Villi increase surface area significantly.
• Microvilli further multiply surface area on each villus.

Together, villi and microvilli create a very large internal surface area inside the small intestine.

This large surface area allows more digested nutrients to contact the intestinal lining.

• More surface area means more absorption sites.
• Increased contact with nutrients speeds absorption.

A larger surface area enables faster and more efficient absorption of nutrients into the bloodstream.

This adaptation supports the body's nutritional needs effectively.

• Efficient absorption supports growth and repair.
• Maximizes nutrient uptake from food.

A villus is a tiny finger-like projection found in the lining of the small intestine.

It has a thin outer layer made of epithelial cells to allow nutrients to pass through easily.

• Finger-like shape increases surface area.
• Thin epithelial layer facilitates nutrient passage.

Inside the villus are blood capillaries that absorb amino acids and sugars.

A lymph vessel called a lacteal absorbs fatty acids and glycerol.

Muscle fibers in the villus help it move to improve contact with food.

• Blood capillaries transport absorbed sugars and amino acids.
• Lacteal carries absorbed fats via the lymphatic system.
• Muscle fibers enhance absorption by moving the villus.

The villus structure maximizes nutrient absorption by increasing surface area and providing close access to transport vessels.

Movement of villi improves mixing and contact with digested food.

• Efficient nutrient uptake into blood and lymph.
• Supports digestion and nutrition.

Capillaries are tiny blood vessels located inside each villus of the small intestine. Their main function is to absorb water-soluble nutrients such as glucose and amino acids from digested food. Once absorbed, these nutrients enter the bloodstream through the capillaries and are transported to body cells for energy, growth, and repair.

• Absorb glucose and amino acids from digested food.
• Transport these nutrients directly into the bloodstream.
• Located within the villi to maximize nutrient uptake.

Lacteals are small lymphatic vessels found inside villi alongside capillaries. They absorb fat-soluble nutrients, mainly fatty acids and glycerol, which are products of fat digestion. These nutrients enter the lymphatic system via lacteals and eventually reach the bloodstream, bypassing the direct blood capillaries initially.

• Absorb fatty acids and glycerol from digested fats.
• Transport fats through the lymphatic system before entering the blood.
• Work alongside capillaries to ensure all nutrient types are absorbed.

Villi are finger-like projections that increase the surface area of the small intestine, enhancing nutrient absorption. The presence of both capillaries and lacteals within villi allows efficient separation and transport of water-soluble and fat-soluble nutrients, ensuring the body receives a full range of digested food components.

• Increase surface area for absorption in the small intestine.
• Contain both capillaries and lacteals for different nutrient types.
• Support efficient nutrient uptake and distribution.