Erythrocytes

What is the function of RBC’s?

• Oxygen-transporting, iron-containing cells

• Transports carbon dioxide as well

What is the most numerous/abundant of the formed elements?

Erthyrocytes; RBCs

Describe the structure of erythrocytes (3):

• Biconcave disc

• No nucleus or organelles

• Uniform-size; 7.5 uM diameter

What special protein within erythrocytes contains iron and helps with carrying oxygen?

Hemoglobin

What causes the red color of blood?

Oxidation of iron atoms in hemoglobin

How many oxygen molecules can hemoglobin molecule carry?

4 oxygen molecules

Where does CO2 bind on an RBC?

CO2 can bind to the globin part of hemoglobin

What enzyme within RBCs is critical for the formation of bicarbonate ions?

Carbonic anhydrase

• Catalyze conversion of CO2 and H2O into carbonic acid (H2CO3)

• Then converts H2CO3 → HCO3-

What else is hemoglobin involved with other than carrying gases?

• Regulating blood flow and blood pressure via the release of nitric oxide

  • Causes vasodilation, improving blood flow and enhances oxygen delivery

What are some structural characteristics that contribute to the respiratory function of RBC’s? (3)

• Biconcave shape - 30% more surface area than spherical cells of the same volume

• 97% hemoglobin - massive O2 carrying capacity

• Lack of mitochondria - does not use the O2 it picks up

Life span of Red Blood Cells?

• 100-120 days

  • 2.5 million RBCs destroyed/created every second

What happens to dead red blood cells?

• They are removed from the circulation by the spleen and liver

• Breakdown products from the cells are recycled and reused

What is the ratio of RBC’s to WBC’s

1000:1

How is RBC production stimulated?

• RBC production is stimulated by hypoxia (low O2 levels)

• Hormone released by kidneys: Erythropoietin stimulates RBC production in red marrow until enough is formed

What is Erythropoietin

A hormone released by the kidneys in response to lowered oxygen concentration to stimulate RBC production in red bone marrow until enough is made; negative feedback loop

Conditions that cause hypoxia (5)

• decreased RBC count

• decreased/defective hemoglobin

• COPD (chronic obstructive pulmonary diseases)

• high altitudes

• Insufficient oxygen delivery to tissues

• Increased tissue demands for oxygen