Human Circulatory System: Heart, Blood & Health

The Human Heart: Structure and Function

The heart is a muscular organ situated between the lungs, slightly to the left. Its walls, known as the myocardium, are responsible for pumping blood.

It is made up of four chambers:

• Two atria (upper chambers)
• Two ventricles (lower chambers)

The heart also contains valves that regulate blood flow:

• The tricuspid valve connects the right atrium and the right ventricle.
• The mitral valve connects the left atrium and the left ventricle.

Understanding the Cardiac Cycle

The cardiac cycle is the sequence of events that occurs with each heartbeat. As the heart beats, it circulates blood through the body's pulmonary and systemic circuits.

There are two main phases of the cardiac cycle:

• Diastole Phase: The heart ventricles relax, allowing the heart to fill with blood.
• Systole Phase: The ventricles contract, pumping blood out of the heart and into the arteries.

A complete cardiac cycle involves the filling of heart chambers with blood, followed by its efficient pumping out to the body.

The Double Circulatory System

The heart utilizes a double circulatory system to keep oxygenated (arterial) blood and deoxygenated (venous) blood separate as they both pass through the heart.

• Pulmonary Circuit: Pumps deoxygenated blood from the heart to the lungs for oxygenation, and then returns oxygenated blood to the heart.
• Systemic Circuit: Links the heart with the rest of the body, delivering oxygenated blood to tissues and collecting deoxygenated blood to return to the heart.

Key vessels involved in circulation include: Aorta, Superior Vena Cava, Inferior Vena Cava, Pulmonary Artery, Right Pulmonary Veins, Left Pulmonary Vein.

Common Cardiovascular Conditions

Some common cardiovascular diseases include:

• Atherosclerosis: Hardening and narrowing of the arteries.
• Hypertension: Also known as high blood pressure.
• Myocardial Infarction: Commonly known as a heart attack.

Blood Disorders and Conditions

Several conditions can affect the blood:

• Anemia: Characterized by a low level of hemoglobin, which carries oxygen. If hemoglobin levels are very low, the blood cannot effectively deliver oxygen to the body's tissues.
• Leukemia: A type of cancer affecting the blood, where white blood cells are unable to fight infection effectively. Bone marrow transplant is a common treatment.
• Hemophilia: A condition where blood clots more slowly or not at all. Individuals with hemophilia experience prolonged bleeding after injuries.

Healthy Habits for Circulatory System

To maintain a healthy circulatory system, consider these habits:

• Engage in moderate-intensity exercise daily.
• Drink at least two liters of water per day.
• Avoid smoking.
• Limit high-fat diets.
• Lead a calm yet active lifestyle.
• Follow a low-salt diet.