Lesson 7 of 7 / Transport in humans
Coronary arteries and heart disease
Why can a blocked coronary artery damage a heart that is full of blood?
I can connect coronary narrowing, reduced oxygen supply and risk factors.
I can explain coronary obstruction, risk factors and prevention.Syllabus
Syllabus K224 / K225, Topic 5(e). Explain coronary obstruction, risk factors and prevention.
About 4 min
Make a guess. You are not marked.
The heart is always full of blood. Why can a blocked artery on its surface still kill heart muscle?
Show the answer
Heart muscle gets oxygen from its own coronary arteries.
Blood inside the chambers does not feed the thick wall. A blocked coronary artery cuts oxygen to the muscle it supplies.
The key idea
Heart muscle needs its own coronary blood supply. An obstruction can reduce oxygen delivery and aerobic energy release.
Explanation
The blood inside the heart's chambers does not feed the heart muscle. The heart muscle has its own blood supply. Coronary arteries branch off the aorta and bring oxygen and nutrients to the heart muscle.
In coronary heart disease, fatty deposits build up in the walls of the coronary arteries and make them narrower. A blood clot can then block the narrow space.
With less blood flow, the heart muscle gets less oxygen. It can carry out less aerobic respiration, so it has less energy to contract. If the blood supply is cut off for long enough, heart muscle cells die. This is a heart attack.
Smoking, not exercising and a diet high in saturated fat are risk factors. Smoking can damage the lining of arteries, and some diets raise blood cholesterol, which helps fatty deposits form. Risk factors make heart disease more likely, but they do not make it certain.
Not smoking, exercising regularly and eating a balanced diet low in saturated fat can lower the risk. Age and genes also affect risk, so these steps cannot remove it completely.
Step by step
- 1
Find the blockage
Name a coronary artery, which supplies the heart muscle, not just "the heart".
- 2
Follow what happens
Narrower artery -> less blood flow -> less oxygen reaches the muscle.
- 3
Say the effect on the cells
Less aerobic respiration means less energy for contraction. A long, severe shortage can kill heart muscle cells.
Worked example
Explain an association carefully
A study finds more coronary disease among smokers. Give a biological explanation and one limit to the conclusion.
One way to explain it
Smoking can damage artery linings and contribute to narrowing or blockage of coronary arteries, reducing oxygen delivery to heart muscle. The association does not show that every smoker develops disease or that smoking is the only risk factor.
Why this answer works
- Connect the risk factor to the vessel.
- Connect reduced flow to oxygen supply.
- Avoid treating a risk factor as a certain prediction for an individual.
Watch out for this
A student says: "A coronary blockage stops oxygen entering the lungs." What is wrong with this?
Show the answer
It restricts blood supplying part of the heart muscle. Lung gas exchange is a different step in the oxygen-delivery pathway.
Check your understanding
What is the most direct effect of a blocked coronary artery on the muscle it supplies?
Show the answer
Less oxygen arrives, reducing aerobic energy release.
The muscle needs a continuing blood supply for respiration and contraction.
Exam-style questions
Check your understanding
A coronary artery is partly blocked by fatty deposits. Why can this cause chest pain during exercise?
Show the answer
Heart muscle gets too little oxygen for the aerobic respiration it needs
Less blood reaches the heart muscle, so it cannot release enough energy aerobically when working hard.
Quick recall
Why can a blocked coronary artery damage a heart that is full of blood?