Human Circulatory System Overview

Blood vessels are tubes that carry blood throughout the body. They are vital for transporting oxygen, nutrients, and waste products.

Arteries are responsible for carrying oxygenated blood away from the heart. The only exceptions are the pulmonary artery and umbilical artery.

Veins carry deoxygenated blood back to the heart, with the pulmonary vein and umbilical vein being exceptions.

Capillaries are tiny blood vessels that connect arteries and veins. They're responsible for gas and nutrient exchange.

Arteries have thicker walls than veins to withstand the higher pressure generated by the heart's pumping action.

The walls of arteries contain more elastic tissue, allowing them to expand and contract to maintain continuous blood flow.

Veins have larger lumens than arteries, reducing resistance to blood flow. This allows blood to flow back to the heart more easily.

Valves in veins prevent backflow of blood, ensuring that it flows in the correct direction back to the heart.

The valves between the atria and ventricles (bicuspid and tricuspid) and the valves at the base of blood vessels (semi-lunar valves) prevent the backflow of blood.

The bicuspid valve prevents the backflow of blood from the left ventricle into the left atrium when the ventricle contracts.

The tricuspid valve prevents the backflow of blood from the right ventricle into the right atrium when the ventricle contracts.

The semilunar valves prevent the backflow of blood from the aorta or pulmonary artery into the left and right ventricles respectively.

Pressure differences between the heart chambers control the opening and closing of the valves. Valves only open in one direction.

The movement of blood through the heart and body in a complete circuit.

The circulation of blood between the heart and lungs.

The circulation of blood between the heart and the rest of the body, excluding the lungs.

A condition where blood is only pumped through the heart once per complete circulatory loop.

The condition of having blood flow through the heart twice in a complete circulatory cycle.

A hole in the wall separating the left and right atria of the heart.

When blood from the left atrium mixes with deoxygenated blood from the right atrium due to a septal defect.

This condition prevents the body from receiving sufficient oxygen, potentially leading to health problems like fatigue and shortness of breath.

The inner space of a blood vessel through which blood flows.

Arteries have thicker walls than veins. This is to withstand the higher blood pressure from the heart.

Veins have larger lumens than arteries. This allows for easier blood flow back to the heart.

Blood vessels with thick walls can stretch and recoil, helping to maintain a continuous blood flow.

The pericardium is a membrane surrounding the heart. The pericardial fluid it contains reduces friction during heartbeats.

The left ventricle has a thicker wall to pump blood to the entire body, while the right ventricle only pumps to the lungs.

Coronary arteries supply the heart muscle with blood. If they are blocked, the heart muscle receives insufficient oxygen and nutrients, potentially leading to a heart attack.

The septum is a muscular wall that separates the left and right sides of the heart, preventing blood from mixing between the oxygenated and deoxygenated sides.

The size of the molecules determines their ability to pass through the capillary wall. Plasma proteins, red blood cells and blood platelets are too large to pass through the capillary wall.

At the venule end of the capillaries, the water potential of the blood is lower than that of the tissue fluid due to the presence of plasma proteins. This water potential gradient drives water back into the blood by osmosis.

Most tissue fluid returns to the blood at the venule end of capillaries. The remaining fluid drains into lymph capillaries, following a pressure gradient.

The difference in hydrostatic pressure between blood and tissue fluid at the arterial end of the capillary, where blood pressure is higher.

The difference in hydrostatic pressure between tissue fluid and lymph at the arterial end of the capillary, where tissue fluid pressure is higher.

The lymphatic system is a network of vessels, tissues, and organs that help maintain fluid balance, filter waste, and fight infections.

Lymph is a fluid that circulates throughout the lymphatic system. It's similar to blood, but lacks red blood cells, platelets, and some plasma proteins.

Lymph nodes are small, bean-shaped organs that filter lymph and house white blood cells.

The spleen filters blood, removes old or damaged red blood cells, and stores white blood cells.

The thymus gland produces and matures white blood cells called T-cells, which are crucial for immune defense.

The tonsils are two masses of lymphatic tissue located in the back of the throat. They trap and destroy germs entering the mouth and nose.

Lymph flow is maintained by skeletal muscle contractions and valves within the lymph vessels, similar to the veins in the circulatory system.

The lymphatic system plays a vital role in maintaining fluid balance, filtering waste, transporting fats, and defending the body against infections.