Circulatory system- heart

Structure of the Heart:

The heart is divided into two halves: the right side and the left side, separated by a wall called the septum.

• The right side pumps deoxygenated bloo****d to the lungs.

• The left side pumps oxygenated blood around the body. Each side of the heart contains two chambers:

• Atria (plural of atrium): These are the upper chambers of the heart that receive blood. The right atrium receives deoxygenated blood from the body, and the left atrium receives oxygenated blood from the lungs.

• Ventricles: These are the lower chambers of the heart that pump blood out. The right ventricle pumps deoxygenated blood to the lungs, and the left ventricle pumps oxygenated blood to the rest of the body.

Valves and Their Role:

Tricuspid Valve: Located between the right atrium and right ventricle. It opens when pressure builds up in the right atrium, allowing blood to flow into the right ventricle.

Bicuspid (Mitral) Valve: Located between the left atrium and left ventricle. It opens when pressure builds in the left atrium, allowing blood to flow into the left ventricle.

Semilunar Valves: These valves prevent backflow of blood into the heart:

• One is located at the entrance of the aorta (from the left ventricle).
• Another is at the entrance of the pulmonary artery (from the right ventricle).

Major Blood Vessels:

Aorta:

• The largest artery in the body.

• Carries oxygenated blood from the left ventricle to the rest of the body. Vena Cava:

• The largest vein in the body.

• Carries deoxygenated blood from the body back to the right atrium. Pulmonary Artery:

• Carries deoxygenated blood from the right ventricle to the lungs for oxygenation. Pulmonary Vein:

• Carries oxygenated blood from the lungs back to the left atrium.

Relative Thickness of Chamber Walls:

Left Ventricle:

• The wall of the left ventricle is much thicker than the wall of the right ventricle because it needs to pump blood around the entire body. The left ventricle must generate a high pressure to ensure blood reaches distant tissues and organs. Right Ventricle:

• The wall of the right ventricle is thinner than the left ventricle because it only needs to pump blood a short distance to the lungs. The pressure required is much lower compared to the systemic circulation. Atria:

• The walls of the atria are thinner than those of the ventricles because they only need to push blood into the ventricles, a much shorter distance.

How the Heart Works:

• Blood enters the heart via the vena cava into the right atrium.
• The right atrium contracts, pushing blood through the tricuspid valve into the right ventricle.
• The right ventricle then contracts, sending blood through the pulmonary artery to the lungs for oxygenation.
• Oxygenated blood returns to the heart via the pulmonary vein into the left atrium.
• The left atrium contracts, pushing blood through the bicuspid valve into the left ventricle.
• The left ventricle contracts, sending oxygenated blood through the aorta to the rest of the body. This double circulatory system ensures that blood is efficiently pumped to both the lungs (pulmonary circulation) and the rest of the body (systemic circulation).

Double circulatory system (mammals)	Single circulatory system (fish)
PULMONARY CICUIT Heart-lungs heart-body-heart	Deoxygenated blood from body of fish travels to heart and pumper round again in a single circuit
SYSTEMIC CIRCUIT Heart

The Circulatory System:

The circulatory system is made up of:

• Arteries: These carry oxygenated blood away from the heart, except for the pulmonary artery, which carries deoxygenated blood to the lungs.
• Veins: These carry deoxygenated blood toward the heart, except for the pulmonary vein, which carries oxygenated blood from the lungs.
• Capillaries: These tiny blood vessels connect arteries and veins, allowing the exchange of gases, nutrients, and waste between the blood and cells.

Cardiac output= stroke volume x heart rate

Cardiac output The total volume of blood pumper from left ventricle per minute Stroke volume The amount of blood ejected from the heart per contraction Heart rate The number of beats per minute

Summary:

• The heart is a muscular pump divided into two halves (right and left), each with an atrium and ventricle. The right side handles deoxygenated blood, and the left side handles oxygenated blood.
• Valves in the heart prevent backflow of blood, ensuring a one-way flow of blood through the heart and into major blood vessels.
• The heart's chamber walls differ in thickness, with the left ventricle having the thickest wall to generate enough force to pump blood around the body.
• Major blood vessels such as the aorta, vena cava, pulmonary artery, and pulmonary vein are responsible for transporting blood to and from the heart.
• The circulatory system ensures that oxygenated and deoxygenated blood are transported efficiently, supporting the body's metabolic needs.