Blood is categorized into four different types (A, B, AB, and O) based on the type of antigens found on the outside of the red blood cells. Additionally, each type can be negative or positive based on whether or not the cells have an antigen called the Rh factor.

Vitamin D helps calcium strengthen bones while also aiding muscle, nerve, and immune system function.

Anemia, which may cause weakness, dizziness, and headaches is caused by a lack of iron in the diet.

Blood is created in bone marrow and is made up of cells suspended in liquid plasma. Red blood cells carry oxygen, white blood cells fight infection, and platelets are cell fragments that allow blood to clot.

An element is matter than cannot be separated into different types of matter by ordinary chemical methods.