This is usually due to atrophy of the glandular mucosa of the stomach, which normally secretes a protein called intrinsic factor. In pernicious anemia there is an inadequate amount of vitamin B12, which is needed for red blood cell production.

The most common type is iron-deficiency anemia, caused by a deficiency of iron, which is an essential component of the hemoglobin molecule. Notice the shape of the red blood cells, sometimes described as a 'biconcave disc.'ДЄnemia refers to any condition in which there is an abnormally low hemoglobin concentration and/or red blood cell count. As seen here, they are clinging to a hypodermic needle. в– Figure 13.2 A scanning electron micrograph of red blood cells. The iron group of heme is able to combine with oxygen in the lungs and release oxygen in the tissues. Each hemoglobin molecule consists of four protein chains called globins, each of which is bound to one heme, a red-pigmented molecule that contains iron. Older erythrocytes are removed from the circulation by phagocytic cells in the liver, spleen, and bone marrow.Д®ach erythrocyte contains approximately 280 million hemoglobin molecules, which give blood its red color. Partly because of these deficiencies, erythrocytes have a relatively short circulating life span of only about 120 days. Erythrocytes lack nuclei and mitochondria (they obtain energy through anaerobic respiration). Their unique shape relates to their function of transporting oxygen it provides an increased surface area through which gas can diffuse (fig.

ErythrocytesД®rythrocytes are flattened, biconcave discs, about 7 |im in diameter and 2.2 |im thick. The same volume of blood, by contrast, contains only 5,000 to 9,000 leukocytes. A cubic millimeter of blood contains 5.1 million to 5.8 million erythrocytes in males and 4.3 million to 5.2 million erythrocytes in females. Erythrocytes are by far the more numerous of the two. The formed elements of blood include two types of blood cells: erythrocytes, or red blood cells, and leukocytes, or white blood cells.

Formed elements of blood