B3.2.2—Artery and vein structure
Arteries and veins share layered vessel walls but differ clearly in wall thickness, lumen size, pressure conditions, elastic tissue and valve presence.
- Syllabus
- First assessment 2025
- Objective
- B3.2.2
- Level
- HL
Exam analysis
Chance of appearing3%of analysed past papers
Latest appearanceMay 2023
Most common paperPaper1
Typical marks1
Common command terms
- Identify
- Label
- Describe
- Explain
- Distinguish
Scoring notes
- Common mistake
- Using non-visible features such as valves when a micrograph question asks for visible artery-vein differences.
Recent exam appearances
May 2023Paper1 ["HL"] · TZ120[ 1 ]B3.2.2—Artery and vein structure
May 2022Paper1 ["HL"] · TZ220[ 1 ]B3.2.2—Artery and vein structure
May 2016Paper1 ["HL"] · TZ036[ 1 ]B3.2.2—Artery and vein structure
Practice this objective
Coverage 2016–2023 · Updated 15 Jul 2026
Arteries and Veins Handle Different Pressures
Arteries carry blood away from the heart under higher pressure; veins return blood at lower pressure and need valves and muscle assistance.
Thick elastic and muscular artery walls absorb pulse pressure. Veins have wider lumens, thinner walls and valves that prevent backflow as surrounding muscles compress them.
Trace direction and pressure first; then use wall thickness, lumen and valves to explain the vessel’s job.
During walking, leg muscles squeeze veins and push blood past valves toward the heart; the artery on the same route carries blood away under pulse pressure.
‘Away from the heart’ defines an artery, not oxygen content; the pulmonary artery carries deoxygenated blood.
Artery and vein structure
Assessment in practice
1–3 marksHow it is assessed
This objective is assessed through structured response, commonly using Identify / Label / Describe.
Command terms
Identify / Label / Describe / Explain / Distinguish
What earns marks
Build the answer around this relationship: Arteries have thicker walls and smaller lumens than veins.
Watch for
Using non-visible features such as valves when a micrograph question asks for visible artery-vein differences.
Representative question
Question 1
Explain the structures and functions of arteries and veins.
Link Transport Structure To Function
Animal and plant transport answers should link structure to function. In animals, capillaries exchange, arteries maintain high-pressure flow, veins return low-pressure blood, pulse measures arterial pressure waves, and coronary occlusion blocks oxygen delivery to heart muscle. In plants, xylem transports water by transpiration tension and cohesion, while stem and root tissue plans show where xylem and phloem are arranged.
- Blood vessel answers need structure plus pressure or exchange function.
- Xylem answers need transpiration pull, cohesion, adhesion, lignin, pits, and hollow vessels when relevant.
- Plant diagrams should identify tissue distribution: stem vascular bundles in a ring, root xylem cross with phloem between arms.
Concept essentials
- Arteries have thicker walls and smaller lumens than veins.
- Veins have larger lumens and valves for low-pressure return.
- Elastic tissue is more prominent in arteries and helps smooth pressure pulses.
- Visible lumen and wall thickness are key features in vessel micrographs.