Blood vessels: structure fits pressure and exchange
| English | 中文 | Pinyin |
|---|---|---|
| artery/ˈɑːtəri/ | 动脉 | dòng mài |
| capillary/kəˈpɪləri/ | 毛细血管 | máo xì xuè guǎn |
What would explain this observation?
- A vessel supplying tissue under high pressure has a different structure from a vessel where exchange with cells occurs.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Arteries carry blood away from the heart and have thick muscular, elastic walls suited to higher pressure. Veins return blood toward the heart at lower pressure; they generally have a larger lumen and valves helping prevent backflow. Capillaries have very thin walls, allowing a short diffusion path between blood and tissues.
- artery 动脉: A blood vessel carrying blood away from the heart; capillary 毛细血管: A very small vessel with a thin wall supporting exchange.
Which feature directly supports exchange across a capillary?
Use structure → effect → function. A capillary wall only one cell thick reduces diffusion distance. Arterial muscle and elastic tissue cope with and modify blood flow under pressure. Venous valves aid one-way flow, particularly when pressure is low. Direction defines artery versus vein, while exchange defines the key capillary role.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Use structure → effect → function. A capillary wall only one cell thick reduces diffusion distance. Arterial muscle and elastic tissue cope with and modify blood flow under pressure. Venous valves aid one-way flow, particularly when pressure is low. Direction defines artery versus vein, while exchange defines the key capillary role.
- Compare provided transverse vessel diagrams using their own scale information. Identify wall thickness and lumen, and distinguish a section image from the direction of flow. A collapsed specimen or schematic drawing should not be treated as a precise pressure measurement.
Which two habits make the investigation or model in this case more defensible?
Compare provided transverse vessel diagrams using their own scale information. Identify wall thickness and lumen, and distinguish a section image from the direction of flow. A collapsed specimen or schematic drawing should not be treated as a precise pressure measurement.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: in a fictional diagram an artery lumen radius is 1 mm and a vein lumen radius is 2 mm. Circular areas are π and 4π mm², giving area ratio 4. Doubling radius gives four times the area; it does not alone specify actual flow or pressure because those depend on further conditions.
Two model circular lumens have radii 1 and 3 units. Calculate larger/smaller area ratio. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
Two model circular lumens have radii 1 and 3 units. Calculate larger/smaller area ratio.
The result is 9 . Known: in a fictional diagram an artery lumen radius is 1 mm and a vein lumen radius is 2 mm. Circular areas are π and 4π mm², giving area ratio 4. Doubling radius gives four times the area; it does not alone specify actual flow or pressure because those depend on further conditions.
Check the conclusion and its limits
- A vein does not necessarily carry oxygen-poor blood: the pulmonary vein returns oxygen-rich blood. Large lumen area is not by itself evidence that a vessel’s flow rate is greater. Capillaries are small exchange vessels, not tiny versions with all arterial wall layers.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
A vessel’s oxygen content alone defines whether it is an artery. This claim is false: A vein does not necessarily carry oxygen-poor blood: the pulmonary vein returns oxygen-rich blood. Large lumen area is not by itself evidence that a vessel’s flow rate is greater. Capillaries are small exchange vessels, not tiny versions with all arterial wall layers.
Blood vessels: structure fits pressure and exchange: Use structure → effect → function. A capillary wall only one cell thick reduces diffusion distance. Arterial muscle and elastic tissue cope with and modify blood flow under pressure. Venous valves aid one-way flow, particularly when pressure is low. Direction defines artery versus vein, while exchange defines the key capillary role.
A vessel’s oxygen content alone defines whether it is an artery.
A vein does not necessarily carry oxygen-poor blood: the pulmonary vein returns oxygen-rich blood. Large lumen area is not by itself evidence that a vessel’s flow rate is greater. Capillaries are small exchange vessels, not tiny versions with all arterial wall layers.
A blood vessel carrying blood away from the heart: write the technical term.
artery means A blood vessel carrying blood away from the heart.