Overview
This lecture covers the structure and function of circulatory systems in fish and mammals, focusing on blood flow, the heart, and coronary heart disease.
Circulatory Systems Overview
- The circulatory system transports nutrients and gases via blood, blood vessels, a pump (heart), and valves.
- Fish have a single circulatory system where blood passes through the heart once per cycle.
- Mammals have a double circulatory system where blood passes through the heart twice per full body circuit.
Single vs. Double Circulation
- In fish, the heart has two chambers: atrium and ventricle.
- Fish: deoxygenated blood enters the heart, gets oxygenated at the gills, then circulates through the body.
- Mammals: four-chambered heart (right/left atria and ventricles), with separate pulmonary (lungs) and systemic (body) circuits.
- Double circulation allows higher blood pressure and more efficient delivery of oxygen and glucose.
Structure of the Mammalian Heart
- Right atrium receives deoxygenated blood from the body via the vena cava.
- Tricuspid valve prevents backflow from right ventricle to right atrium.
- Right ventricle pumps deoxygenated blood to lungs via pulmonary artery and semilunar valve.
- Pulmonary vein brings oxygenated blood from lungs to left atrium.
- Bicuspid valve prevents backflow from left ventricle to left atrium.
- Left ventricle pumps oxygenated blood through aorta to the body.
- Septum separates oxygenated and deoxygenated blood.
- Arteries carry blood away from the heart; veins carry blood towards the heart.
Coronary Circulation and Heart Structure
- Coronary arteries supply blood to the heart muscle itself.
- Ventricles have thicker muscle walls than atria due to their role in pumping blood out of the heart.
- Left ventricle wall is thicker than right because it pumps blood to the entire body.
Heart Rate and Physical Activity
- Exercise increases heart rate to supply more oxygen and glucose to muscle cells.
- Heart rate gradually returns to normal after exercise as oxygen debt is repaid.
Coronary Heart Disease
- Caused by blockage of coronary arteries, leading to oxygen deprivation of heart muscles (heart attack).
- Risk factors: high-fat diet, lack of exercise, stress, smoking, genetics, age, and male gender.
- Prevention: avoid smoking, eat a healthy diet low in animal fats, and exercise regularly.
Key Terms & Definitions
- Atrium — Upper heart chamber that receives blood.
- Ventricle — Lower heart chamber that pumps blood out.
- Valve — Structure that prevents backflow of blood.
- Pulmonary artery/vein — Blood vessels carrying blood between heart and lungs.
- Aorta — Major artery carrying oxygenated blood from heart to body.
- Coronary artery — Blood vessel supplying heart muscle itself.
- Single circulation — Blood passes through the heart once per body circuit.
- Double circulation — Blood passes through the heart twice per body circuit.
Action Items / Next Steps
- Review diagrams of single and double circulation.
- Memorize the function of each heart chamber and vessel.
- Study risk factors and prevention for coronary heart disease.