Variations in Anatomy and Physiology Related to the Hematologic System

Question 1

Red Blood Cell Production

Answer 1

1. The production of red blood cells in the embryo begin at 8 weeks gestation
2. In the embryo, blood cells primarily form in the liver; this continues until a few weeks before delivery
3. Lymphoid cells take place in the spleen of the embryo and the thymus is a site for some transient lymphocyte production
4. EPO (hormone that regulates RBC production) is derived from the liver in the fetus
5. After birth, the kidney take over this production

Question 2

Hemoglobin

Answer 2

1. Three types of Hemoglobin
   a. Hgb A
   b. Hgb F or fetal
   c. Hbg A2
2. After six months of age, Hgb is the predominant type
3. In the neonatal period, the largest difference is with the RBCs. Fetal hemoglobin, which has a much shorter cell life is present in higher qualities, putting the infant at risk for anemia and leading to problems with the oxygen carrying capacity of blood.
4. As the production of the cells transfers from the liver to the bone marrow of the long and flat bones, the balance between oxygenation and production is affected

Question 3

Iron

Answer 3

1. The fetus receives iron through the placenta from the mother
2. The preterm infant misses out on the final weeks or months of transplacental iron transfer, putting them at risk for an increased risk of anemia
3. In the term infant, a period of physiologic anemia occurs between the age of 2 and 6 months
   > Due to the fact that the infant demonstrates rapid growth and an increase in blood volume over the first several months of life, and maternally derived iron stores are depleted by 4 to 6 months of age
4. Sufficient iron intake is critical for the appropriate development of hemoglobin and RBCs
5. Infant must ingest adequate quantities of either from breast milk or from iron-fortified formula in early infancy and other food sources in later infancy
6. Adolescence is also a time of rapid growth, and intake of iron must increase