The CEA test measures the level of carcinoembryonic antigen (CEA) in the blood.CEA is a protein normally found in the tissue of a developing baby in the womb. The blood level of this protein disappears or becomes very low after birth.he CEA test measures the level of carcinoembryonic antigen (CEA) in the blood.
Blood is made up of cells in a watery base, called plasma. There are three major types of cells blood made up of â red blood cells (RBCs), while blood cells (WBCs) and platelets. 1  They are also known as erythrocytes, carry oxygen to various parts of the body.  They are the most in number, constituting about 40-45% of blood. Their structure is like that of dough nuts.
Blood is a constantly circulating fluid providing the body with nutrition, oxygen, and waste removal. Blood is mostly liquid, with numerous cells and proteins suspended in it, making blood thicker than pure water. The average person has about 5 liters (more than a gallon) of blood. A liquid called plasma makes up about half of the content of blood. Plasma contains proteins that help blood to clot, transport substances through the blood, and perform other functions. Blood plasma also contains glucose and other dissolved nutrients. About half of blood volume is composed of blood cells: