Erythrocytes, or red blood cells (RBCs), are the most abundant formed elements in blood. Their specialized structure enables them to carry respiratory gases and travel through very narrow vessels.
A single drop of blood contains millions of erythrocytes but only thousands of leukocytes. Typical counts are about 5.4 million RBCs per microliter of blood in males and about 4.8 million per microliter in females. Erythrocytes make up an estimated 25 percent of the body's total cells.
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What is a reticulocyte?
A newly circulating, immature erythrocyte that may retain organelle remnants for a day or two. Reticulocytes usually account for about 1–2 percent of the RBC count.
What does spectrin do in an erythrocyte?
Spectrin is a flexible cytoskeletal protein that helps maintain erythrocyte structure and allows the cell to bend through narrow capillaries.
How does the biconcave shape benefit an erythrocyte?
It provides a high surface-area-to-volume ratio for gas exchange and room for hemoglobin.
What is hemoglobin made of?
Hemoglobin consists of four globin protein chains, two alpha and two beta, each associated with a heme group containing an iron ion.
What are oxyhemoglobin and deoxyhemoglobin?
Oxyhemoglobin has oxygen bound and appears bright red. Deoxyhemoglobin has released some oxygen and appears darker red.
Quiz questions
What are the main gas-transport roles of erythrocytes?Answer: Carry oxygen to tissues and return some carbon dioxide to the lungs.
What is a reticulocyte?Answer: An immature circulating erythrocyte that may retain organelle remnants.
Why do mature erythrocytes rely on anaerobic respiration?Answer: They lack mitochondria and therefore do not use transported oxygen for aerobic respiration.
How many oxygen molecules can one hemoglobin molecule bind at most?Answer: Four, because each of its four heme iron ions can bind one oxygen molecule.
How do the kidneys respond when their tissues have low oxygen availability?Answer: They release erythropoietin, which stimulates red bone marrow to produce more erythrocytes.
Based on Anatomy and Physiology 2e by J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.