Edexcel iGCSE Biology-2.32 small intestine- Study Notes- New Syllabus
Edexcel iGCSE Biology-2.32 small intestine- Study Notes- New syllabus
Edexcel iGCSE Biology-2.32 small intestine- Study Notes -Edexcel iGCSE Biology – per latest Syllabus.
Key Concepts:
2.32 understand how the small intestine is adapted for absorption, including the structure of a villus
Small Intestine – Adaptations for Absorption
📝 Introduction
After digestion, the small intestine absorbs nutrients into the blood or lymph.
Adaptations of its structure ensure absorption is efficient and fast.
⚙️ Key Adaptations
- Length
Very long (~6 meters) → provides large surface area for absorption. - Inner lining – Villi
Small finger-like projections in the lining of the ileum.
Greatly increase surface area for absorption. - Microvilli
Tiny projections on the epithelial cells of villi.
Further increase surface area (brush border).
- Thin walls
Villus epithelium is one cell thick → short diffusion distance for nutrients. - Rich blood supply
Each villus has capillaries → maintains concentration gradient for glucose & amino acids.
Lacteal (lymph vessel) → absorbs fatty acids & glycerol. - Movement of villi
Slight movement mixes food → brings fresh nutrients close to absorbing surface.
🧩 Structure of a Villus
| Part | Adaptation | Function |
|---|---|---|
| Epithelial cells | One cell thick | Short diffusion distance |
| Microvilli | Tiny projections | Large surface area |
| Capillaries | Network of blood vessels | Absorb glucose & amino acids |
| Lacteal | Central lymph vessel | Absorb fatty acids & glycerol |
| Thin wall + moist surface | Easy diffusion of nutrients |
📊 How Absorption Works
- Glucose & amino acids → diffuse into capillaries → transported in blood.
- Fatty acids & glycerol → enter lacteal → transported via lymph.
- Large surface area + thin walls + rich blood supply = efficient nutrient absorption.
⚡ Quick Recap
Length + villi + microvilli → huge surface area.
Thin walls → short diffusion distance.
Capillaries & lacteal → absorb nutrients fast.
Villi movement → mixes contents → improves absorption.