9700 · 8.3
The heart
Welcome to this lesson on **The Heart**! This incredible organ is the driving force of your circulatory system, a true marvel of biological engineering. For your Cambridge International Biology 9700 exams, you need a solid understanding of its **structure**, **function**, and how it integrates with different **blood vessels**. Let's dive in and master this vital topic. Key points align with **A-Level Notes** 9700 Biology chapter **8** (topic **8.3**). Notes and diagrams from **A-Level Notes** chapter **8**, topic **8.3** (4 pages).
Need to know
What you need to know
- **Four Chambers:** The heart has two upper chambers, the **atria** (singular: atrium), which receive blood, and two lower chambers, the **ventricles**, which pump blood out.
- **Septum:** A muscular wall called the septum separates the left and right sides of the heart, preventing the mixing of oxygenated and deoxygenated blood.
- **Valves:** Four valves ensure unidirectional blood flow: - **Atrioventricular (AV) Valves:** Located between atria and ventricles. The **tricuspid valve** is on the right, and the **bicuspid (or mitral) valve** is on the left. - **Semilunar (SL) Valves:** Located at the exit of the ventricles. The **pulmonary valve** is at the start of the pulmonary artery, and the **aortic valve** is at the start of the aorta.
- **Major Blood Vessels:** - **Vena Cava (Superior & Inferior):** Brings deoxygenated blood from the body to the right atrium. - **Pulmonary Artery:** Carries deoxygenated blood from the right ventricle to the lungs. - **Pulmonary Veins:** Bring oxygenated blood from the lungs to the left atrium. - **Aorta:** Carries oxygenated blood from the left ventricle to the rest of the body.
- **Coronary Arteries:** These are the heart's own blood supply, branching off the aorta to deliver oxygen and nutrients to the cardiac muscle itself.
Explanation
The heart
- **Four Chambers:** The heart has two upper chambers, the **atria** (singular: atrium), which receive blood, and two lower chambers, the **ventricles**, which pump blood out.
- **Septum:** A muscular wall called the septum separates the left and right sides of the heart, preventing the mixing of oxygenated and deoxygenated blood.
- **Valves:** Four valves ensure unidirectional blood flow: - **Atrioventricular (AV) Valves:** Located between atria and ventricles. The **tricuspid valve** is on the right, and the **bicuspid (or mitral) valve** is on the left. - **Semilunar (SL) Valves:** Located at the exit of the ventricles. The **pulmonary valve** is at the start of the pulmonary artery, and the **aortic valve** is at the start of the aorta.
- **Major Blood Vessels:** - **Vena Cava (Superior & Inferior):** Brings deoxygenated blood from the body to the right atrium. - **Pulmonary Artery:** Carries deoxygenated blood from the right ventricle to the lungs. - **Pulmonary Veins:** Bring oxygenated blood from the lungs to the left atrium. - **Aorta:** Carries oxygenated blood from the left ventricle to the rest of the body.