IGCSE Biology: Circulatory Systems, Heart & Blood Vessels Vocabulary

Vocabulary practice flashcards covering key definitions, anatomical structures, blood components, and physiological concepts from the IGCSE Biology unit on the circulatory system, heart, and blood vessels.

Circulatory System

An organ system whose role is to transport blood around the body, consisting of blood vessels, a pump (the heart), and valves to ensure one-way blood flow.

Single Circulation

A circulatory system in which blood passes through the heart once for every complete circuit of the body, typical of fish with a two-chambered heart.

Double Circulation

A circulatory system in which blood passes through the heart twice for every complete circuit of the body, typical of mammals with a four-chambered heart.

Pulmonary Circulation

The circulation loop where the right side of the heart receives deoxygenated blood from the body and pumps it to the lungs.

Systemic Circulation

The circulation loop where the left side of the heart receives oxygenated blood from the lungs and pumps it to the rest of the body tissues.

Septum

The muscle wall separating the right and left sides of the heart, preventing the mixing of oxygenated and deoxygenated blood.

Coronary Arteries

Arteries supplying cardiac muscle cells with oxygen, glucose, and nutrients, while removing carbon dioxide and other waste products.

Coronary Heart Disease (CHD)

A condition resulting from the partial or complete blockage of coronary arteries by fatty deposits, reducing blood flow to cardiac muscle cells.

Plaque

A fatty deposit mainly composed of cholesterol and white blood cells that accumulates in artery walls, causing them to narrow and become less elastic.

Angina

Severe chest pain caused by restricted blood flow to the cardiac muscle cells due to partial blockage of the coronary arteries.

Heart Attack

An event caused by the complete blockage of a coronary artery, preventing cardiac muscle cells in that area from respiring and contracting.

Atrioventricular Valves

Valves between the atria and ventricles (tricuspid on the right side, bicuspid on the left side) that shut during ventricular contraction to prevent blood flowing back into the atria.

Semilunar Valves

Valves located in the pulmonary artery and aorta that open when the ventricles contract and close to prevent blood flowing back into the heart.

Left Ventricle

The heart chamber with a much thicker muscle wall than the right ventricle, enabling it to pump blood at high pressure around the entire body.

Oxygen Debt

The extra oxygen required after exercise to break down accumulated lactic acid produced by anaerobic respiration in muscle cells.

Arteries

Blood vessels with thick, muscular walls, elastic fibres, and a narrow lumen that carry blood away from the heart at high pressure.

Veins

Blood vessels with thin walls, a wide lumen, and one-way valves that carry blood towards the heart at low pressure.

Capillaries

Microscopic blood vessels with walls one cell thick and leaky junctions that connect arterioles to venules for exchange of substances with body tissues.

Arterioles

Narrow blood vessels connecting arteries to capillaries as arterial networks divide.

Venules

Narrow blood vessels that collect blood from capillaries and unite to form veins.

Hepatic Artery

The main blood vessel carrying oxygenated blood from the heart to the liver.

Hepatic Vein

The blood vessel carrying deoxygenated blood away from the liver back to the heart.

Hepatic Portal Vein

The blood vessel transporting deoxygenated blood rich in absorbed nutrients directly from the gut to the liver.

Renal Artery

The blood vessel supplying blood from the aorta to the kidneys.

Renal Vein

The blood vessel carrying blood away from the kidneys back to the vena cava.

Plasma

The straw-coloured liquid component of blood ($55\%$ by volume) mainly made of water, transporting blood cells, ions, nutrients, urea, hormones, and carbon dioxide.

Red Blood Cells

Biconcave disc-shaped cells without a nucleus containing high amounts of haemoglobin to transport oxygen as oxyhaemoglobin.

Phagocytes

White blood cells with a multi-lobed nucleus and granular cytoplasm that engulf and digest pathogens through phagocytosis.

Lymphocytes

White blood cells with a large, round nucleus and non-granular cytoplasm that produce antibodies to destroy pathogens and antitoxins to neutralise toxins.

Platelets

Small cell fragments without a nucleus involved in blood clotting and forming scabs at wound sites.

Fibrinogen

A soluble plasma protein converted into insoluble fibrin by chemicals released from activated platelets during blood clotting.

Fibrin

An insoluble protein formed from fibrinogen that forms a mesh across a wound to trap red blood cells and create a clot.