The primary function: transport oxygen (O₂) and carbon dioxide (CO₂) throughout the body.
Key interaction point between the pulmonary system and the cardiovascular system.
Erythrocyte Formation and Structure
Formation Process:
Erythrocytes are formed in the bone marrow through a process called erythropoiesis.
Structure:
Erythrocytes are described as biconcave discs, which increases their surface area for better gas exchange.
Mature red blood cells lack organelles:
No nucleus
No Golgi apparatus
No mitochondria
No smooth endoplasmic reticulum
Lack of organelles limits cellular functions but allows for energy generation through glycolysis, which occurs in the cytosol (does not require organelles).
Essentially, erythrocytes are "bags of hemoglobin".
Hemoglobin:
The protein responsible for carrying oxygen in the blood.
Lifespan and Repair of Red Blood Cells
Erythrocytes have a short lifespan of approximately 120 days due to the inability to repair themselves when damaged (lack of organelles).
Interaction Between Kidney and Bone Marrow
The kidneys secrete a hormone called erythropoietin (EPO), which stimulates erythropoiesis in the bone marrow.
In patients with chronic kidney disease, there is often a reduced number of red blood cells due to decreased secretion of erythropoietin.
Blood Composition and Hematocrit
Blood Components:
Blood consists of cellular components (including erythrocytes and leukocytes) suspended in a liquid portion known as plasma.
Centrifugation:
When a tube of blood is centrifuged, it separates into layers:
Cellular components
Liquid components (plasma)
The percentage of blood volume composed of red blood cells is referred to as hematocrit.
Typical hematocrit level in males: approximately 44-45%.
Males generally have higher hematocrit than females, primarily due to the influence of testosterone and the effects of menstrual blood loss in females.
Structure and Function of Hemoglobin
Hemoglobin is comprised of four subunits, each containing an iron molecule (heme) at its center.
Iron's Role:
Iron is essential for proper hemoglobin formation.
Dietary iron is transported in the blood via a protein called transferrin to the liver and bone marrow.
In the liver, iron is stored as ferritin, while in the bone marrow, it is incorporated into hemoglobin during erythrocyte formation.
Breakdown of Red Blood Cells and Bilirubin Formation
Erythrocytes undergo damage and will eventually be removed from circulation, primarily occurring in the spleen.
The spleen identifies and breaks down damaged red blood cells.
The breakdown of hemoglobin produces a byproduct known as bilirubin.
Bilirubin is transported to the liver for processing into bile, which is secreted into the intestine or excreted via the kidneys, contributing to the yellow tint of plasma and urine.
Conditions causing excessive bilirubin can lead to clinical manifestations such as jaundice (icterus), characterized by a yellowish hue in the sclera of the eyes.
Anemia and Contributing Factors
Anemia Definition:
A reduction in the oxygen-carrying capacity of the blood.
Common Causes of Anemia:
Most common cause: Iron deficiency anemia, resulting from insufficient iron for erythropoiesis.
Another cause: Deficiency of vitamin B12 or folate, leading to a specific type of anemia known as pernicious anemia.
Importance of supplementation with iron, vitamin B12, and folate in daily vitamins due to their critical role in erythropoiesis.