Blood
Explore the fluid that carries gases, nutrients, hormones, waste products, cells, and proteins throughout the body.
More than a red liquid
Blood is a specialized connective tissue made of cells and cell fragments suspended in plasma. It provides a transport system while also contributing to immunity, clotting, and homeostasis.
The liquid component
Plasma contains water, proteins, electrolytes, nutrients, gases, hormones, and other dissolved substances.
Oxygen transport
Red blood cells contain hemoglobin and are specialized for transporting oxygen through the circulation.
Immune defense
White blood cells participate in the body's immune responses and help defend against pathogens.
Clotting
Platelets are cell fragments that participate in the formation of blood clots and help limit blood loss after injury.
Blood is both transport and protection.
The cardiovascular system does more than deliver oxygen. Blood also carries hormones and nutrients, removes wastes, supports immune defense, and participates in clotting.
What blood carries
Blood transports many different materials between tissues. Some are dissolved directly in plasma, while others are carried by specialized cells or blood proteins.
Red blood cells
Red blood cells have a distinctive flexible, biconcave shape that provides a large surface area relative to their volume. Their hemoglobin allows them to transport large amounts of oxygen.
The blood is a delivery system.
The heart creates the flow, the vessels provide the routes, and the blood carries much of the cargo.