Erythrocyte (RBC) structure, activities, and hereditary alterations. A Erythrocyte (RBC) structure, activities, and hereditary alterations. A. RBCs (normal blood smear). The biconcave disc shape normally results in a lighter density in the middle of the cells, known as central pallor (arrow). B. RBC membrane. Multiprotein, integral membrane complexes that include band 3 and glycophorin serve as attachment sites for a specialized cytoskeleton, which consists of short actin fibers stabilized by tropomyosin, which interacts with tetramers of spectrin. These membrane-cytoskeletal interactions stabilize the RBC membrane and are responsible for maintaining the biconcave disc shape of these cells. C. RBCs and gas transport. In the lungs, the high concentration of O2 and the relatively high pH favor O2 entering the blood and binding to hemoglobin, whereas the low CO2 concentration favors the production of CO2 from carbonate by carbonic anhydrase, its diffusion into alveoli, and exhalation (left). In the tissues, the reduced pH and O2 levels favor the release of O2 and the uptake of CO2 (right). D. RBCs from a patient with sickle cell disease. A distorted sickle-shaped cell is indicated by the arrow. E. RBCs from a patient with hereditary spherocytosis. Note the many small cells that lack central pallor. Samples D and E courtesy of Dr. Mohamed Salama, University of Utah School of Medicine, Salt Lake City, Utah. (A, D, and E Wright stain) Source: BLOOD AND HEMATOPOIESIS, The Big Picture: Histology Citation: Ash R, Morton DA, Scott SA. The Big Picture: Histology; 2017 Available at: https://accessphysiotherapy.mhmedical.com/DownloadImage.aspx?image=/data/books/2058/ashhist_ch8_f002bc.png&sec=155784335&BookID=2058&ChapterSecID=155784313&imagename= Accessed: September 27, 2017 Copyright © 2017 McGraw-Hill Education. All rights reserved