Human Circulatory System

Arteries carry oxygenated (pure) blood away from the heart to body tissues, except for the pulmonary artery. Veins typically carry deoxygenated blood back to the heart. The heart pumps blood but doesn't carry it - it's the pumping organ.

Pulmonary veins are unique - they're the only veins that carry oxygenated (pure) blood from the lungs to the left atrium of the heart. All other veins carry deoxygenated blood. This exceptional nature is because they're returning blood from where oxygenation occurred.

The heart is the muscular organ that acts as a pump, continuously circulating blood throughout the body. It delivers oxygen and nutrients to all body cells and removes waste products. The brain controls functions, kidneys filter waste, and lungs exchange gases but none pump blood like the heart does.

Blood clotting (coagulation) is the process that stops bleeding from injured blood vessels. Platelets and clotting factors work together to form a clot at the injury site. Transfusion is transferring blood, disorder refers to disease, and blood-supply is not a biological process.

Blood transfusion is the medical procedure of transferring blood or blood components from one person (donor) to another (recipient). This is done to replace lost blood, treat certain diseases, or during surgery. Clotting is the process of stopping bleeding, and disorder refers to a disease.

The heart is the muscular organ that functions as the body's circulatory pump. It continuously pumps blood through blood vessels to deliver oxygen, nutrients, and hormones to body cells while removing carbon dioxide and metabolic wastes. The heart beats approximately 100,000 times per day.

Blood clotting (coagulation) is the process that prevents excessive blood loss when a vessel is injured. Platelets accumulate at the injury site and release clotting factors that form a fibrin mesh to seal the wound. Transfusion is transferring blood between persons, not preventing loss.

Blood transfusion is the medical procedure of transferring blood or blood components from a donor to a recipient. This is done to replace lost blood during surgery, injury, or to treat certain blood disorders. Clotting is coagulation within a vessel, not transfer between bodies.

The heart's right side pumps deoxygenated blood to the lungs via pulmonary circulation for oxygenation. The left side then pumps oxygenated blood to the entire body through systemic circulation.

The cornea is the only tissue in the human body that completely lacks blood vessels. It must remain transparent to allow light to pass through to the retina, so it receives oxygen and nutrients through diffusion from tears and the aqueous humor (fluid inside the eye). This avascular nature is crucial for maintaining clear vision.

The brain contains approximately 100,000 miles of blood vessels. This extensive network of capillaries, arteries, and veins is necessary to deliver oxygen and nutrients to every part of the brain and remove waste products.

The aorta is the largest artery in the human body, originating from the left ventricle and carrying oxygenated blood to the systemic circulation. The jugular and carotid are veins/arteries in the neck, and renal refers to kidney-related blood vessels. The aorta is the major artery.

In biology and medicine, BBB stands for the blood-brain barrier. It is a highly selective semipermeable border that prevents solutes in the circulating blood from non-selectively crossing into the central nervous system.

The human body contains approximately 60,000 miles (97,000 km) of blood vessels including arteries, veins, and capillaries. This extensive network supplies blood to every part of the body.

The cornea is the only living tissue in the human body that does not contain blood vessels - it receives oxygen directly from the air through diffusion, making option C correct. This unique adaptation is necessary for maintaining optical transparency.