CBSE Class 10 Answered

In babies and young children, blood cells are made in the bone marrow 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 that make up the spine), ribs, pelvis, skull, sternum (the breastbone), and parts of the humerus (the upper arm bone) and femur (the thigh bone).

Blood cells travel through the circulatory system suspended in a yellowish fluid called plasma. Plasma is 90% water and contains nutrients, proteins, hormones, and waste products. Whole blood is a mixture of blood cells and plasma.