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Absorption, liver and heart

الأسبوع 5 · الفصل 3: 3-3 كيف يتم الامتصاص (الزغابات والكبد)؛ الفصل 4 «الدورة الدموية والإخراج»: 4-1 القلب والدم · 3 دروس
1

Villi: tiny bumps that soak up food

Science P6: Term 1, Chapters 3–4, pp. 30–37
GoalExplain how villi in the small intestine help absorb nutrients.
New words
absorb · to take into the blood or into the bodynutrient · a part of food that the body needsvilli · tiny finger-like bumps lining the small intestine
Explanation

After digestion, food has been broken into very small pieces called nutrients. To use them, the body must absorb them, and that happens mainly in the small intestine. The inside wall of the small intestine is not smooth. It is covered with villi, tiny finger-like bumps. Villi give the wall a much larger surface, so many more nutrients can pass through into the blood at the same time. Think of a towel: a towel with loops soaks up far more water than a smooth cloth of the same size. The same idea works for villi. Water is absorbed here too. Nutrients and water enter blood vessels in the villi and travel on in the blood.

Smooth wallWall with villi
Surface for absorbingsmalllarge
Nutrients absorbedfewermany more
Worked examples
spilllooped towel
Mariam wipes a spill with a smooth plastic sheet and a looped towel. The towel holds much more water. Villi do the same job for nutrients.
Imagine a straight rope and the same rope with many knots and loops: the knotted one has more surface to hold things. Villi are the loops of the small intestine.
After a meal, nutrients leave the small intestine and enter the blood.
Class activity

Towel test. With a grown-up, use the same amount of water to wet a smooth cloth and a towel with loops. Which holds more? Draw a smooth line and a wavy line to show the wall of the intestine with and without villi.

Practice
1
What are villi?
2
Why do villi help absorption?
3
Where do the nutrients go after absorption?
4
Which one soaks up more: a smooth cloth or a towel with loops?