B3.2.1—Capillary adaptations
Capillaries are narrow, thin-walled exchange vessels whose branching, permeability and closeness to cells support rapid movement between blood and tissues.
- Syllabus
- First assessment 2025
- Objective
- B3.2.1
- Level
- HL
Exam analysis
Chance of appearing2%of analysed past papers
Latest appearanceMay 2014
Most common paperPaper1
Typical marks1–3
Common command terms
- Identify
- Describe
- Explain
Scoring notes
- Common mistake
- Describing capillary walls as thin membranes instead of one-cell-thick endothelial walls.
Recent exam appearances
May 2014Paper1 ["HL"] · TZ221[ 1 ]B3.2.1—Capillary adaptations
May 2012Paper2 ["HL"] · TZ23(c)[ 3 ]B3.2.1—Capillary adaptations
Practice this objective
Coverage 2012–2014 · Updated 15 Jul 2026
Concept essentials
- Capillary walls are one cell thick, giving a short diffusion path.
- Narrow capillaries bring blood close to almost every cell.
- Branching capillary beds increase total surface area for exchange.
- Fenestrations or gaps increase permeability for rapid movement of substances.