- Define and explain Heart and Circulation in your own words
- Use key terms such as double circulation accurately
- Apply what you have learned to new examples and questions
- Avoid the common mistakes learners make with this topic
This lesson focuses on Heart and Circulation: explore the double circulatory system and how blood moves around the body.
Explore the double circulatory system and how blood moves around the body.
Key ideas
The heart and double circulation
The heart is a double pump made of muscle. The right side pumps deoxygenated blood to the lungs, where it picks up oxygen; the left side pumps oxygenated blood around the body. Valves prevent backflow. This double circulation keeps high pressure on the body side, so oxygen reaches tissues quickly, and lets blood be re-oxygenated every circuit.
The hierarchy of organisation
Cells with a similar structure and function form a tissue, such as muscle tissue. Different tissues combine into an organ, such as the stomach, which contains muscle, glandular and epithelial tissue. Organs work together in organ systems, such as the digestive system. Plants are organised the same way: mesophyll tissue forms part of a leaf, which belongs to the shoot system.
Key term — double circulation: The two-loop circulatory system in mammals: one loop carries blood to the lungs, the other to the rest of the body.
Why does the left ventricle have a thicker wall than the right ventricle?
The left ventricle pumps blood all around the body, which needs much higher pressure than pumping blood the short distance to the lungs, so its muscle wall is thicker.
Answer: The left ventricle pumps blood all around the body, which needs much higher pressure than pumping blood the short distance to the lungs, so its muscle wall is thicker.
- Mixing up arteries and veins Arteries carry blood away from the heart (usually oxygenated); veins carry blood towards the heart (usually deoxygenated). The direction relative to the heart defines them, not the oxygen content.
- Saying enzymes are used up or killed Enzymes are not used up in reactions, and they are not alive so they cannot be killed. High temperatures denature them by changing the shape of the active site.
Practice
Valves prevent the backflow of blood, keeping it moving in one direction through the heart and veins.
Cell → tissue → organ → organ system.
Any two of: large surface area; wall one cell thick for a short diffusion distance; rich blood supply to maintain a concentration gradient; many mitochondria for active transport.
21 × 4 = 84 beats per minute.
Quick check
Which of these best defines "double circulation"?
Name the three digestive enzymes and what each breaks down.
- Heart and Circulation: explore the double circulatory system and how blood moves around the body.
- The heart and double circulation: The heart is a double pump made of muscle.
- tissue: A group of similar cells working together to carry out a particular function, such as muscle tissue or xylem tissue.
- Watch out for: mixing up arteries and veins