term 1

• The circulatory system functions to bring nutrients and oxygen to cells and remove waste products for excretion
• Blood is a living tissue that circulates through the body, serving as transportation for oxygen, nutrients, and waste
• Plasma is the liquid part of blood, consisting mainly of water and transporting nutrients, waste products, and gases in dissolved form
• Red blood cells (erythrocytes) are disc-shaped cells formed in the bone marrow, transport oxygen from the lungs to the rest of the body, and have the shortest lifespan
• White blood cells (leucocytes) defend the immune system, protect the body against diseases, and fight germs during infections
• Platelets (thrombocytes) are the smallest particles in the blood, produced in the bone marrow, and play an important role in blood clotting
• Arteries transport oxygen-rich blood from the heart to the cells in the body, with thick, muscled, and elastic walls; the aorta is the main artery
• Veins transport deoxygenated blood back to the lungs via the heart, with thinner, less muscled walls; the pulmonary vein transports oxygen-rich blood from the lungs to the heart
• Capillaries are small, narrow tubes branching from arteries with very thin walls, supplying cells with oxygen and nutrients while removing waste products and carbon dioxide
• The heart, a hollow muscle that contracts and relaxes continuously, pumps deoxygenated blood to the lungs to get rid of carbon dioxide through the pulmonary artery