Two types of blood vessels carry blood throughout our bodies:
1.Arteries carry oxygenated blood (blood that has received oxygen from the lungs) from the heart to the rest of the body.
2.Blood then travels through veins back to the heart and lungs, where it receives more oxygen.
As the heart beats, you can feel blood traveling through the body at pulse points — like the neck and the wrist — where large, blood-filled arteries run close to the surface of the skin.
The blood that flows through this network of veins and arteries is whole blood, which contains three types of blood cells:
1.red blood cells (RBCs)
2.white blood cells (WBCs)
3.platelets
In babies and young kids, blood cells are made within the bone marrow (the soft tissue inside of bones) of many bones throughout the body. But, as kids get older, blood cells are made mostly in the bone marrow of the vertebrae (the bones of the spine), ribs, pelvis, skull, sternum (the breastbone), and parts of the humerus (the upper arm bone) and femur (the thigh bone).
The cells travel through the circulatory system suspended in a yellowish fluid called plasma, which is 90% water and contains nutrients, proteins, hormones, and waste products. Whole blood is a mixture of blood cells and plasma.
Nutrients in the Blood
Blood contains other important substances, such as nutrients from food that has been processed by the digestive system. Blood also carries hormones released by the endocrine glands and carries them to the body parts that need them.
Blood is essential for good health because the body depends on a steady supply of fuel and oxygen to reach its billions of cells. Even the heart couldn't survive without blood flowing through the vessels that bring nourishment to its muscular walls.
Blood also carries carbon dioxide and other waste materials to the lungs, kidneys, and digestive system to be removed from the body.
Blood cells and some of the special proteins blood contains can be replaced or supplemented by giving a person blood from someone else via a transfusion. In addition to receiving whole-blood transfusions, people can also receive transfusions of a particular component of blood, such as platelets, RBCs, or a clotting factor. When someone donates blood, the whole blood can be separated into its different parts to be used in this way.
