Circulatory System Overview

Circulatory System

• The circulatory system is a transport system that contributes to the body's defenses, coagulation process, and temperature control.
• It is made up of blood, blood vessels, and the heart.

Blood

• Blood is a type of connective tissue that consists of cells, chemicals, and fluid.
• Its function is to transport substances through the body and maintain a stable internal environment.
• Blood's formed elements include red blood cells, white blood cells, and platelets, while the rest is plasma.

Blood Plasma

• It is a straw-colored, sticky liquid portion of blood.
• About 90% of plasma is water.
• Plasma contains:
  • Ions: Sodium and Chloride
  • Nutrients: Sugars, amino acids, lipids, cholesterol, vitamins, and trace elements
  • Three main proteins: Albumin (60%), globulin (35%), and fibrinogen (4%)
  • Dissolved Gases: Oxygen and Carbon Dioxide
  • Waste Products: Protein wastes such as urea and bilirubin

Red Blood Cells (RBCs)

• The most abundant blood cells (99%).

• Structure:

  • Biconcave, lacking a nucleus, 8 µm in diameter
  • Contains:
    • Hemoglobin
    • Lipids, ATP, Carbonic Anhydrase

• Function:

  • Transport of oxygen and carbon dioxide – majority of CO2 is transported as bicarbonate (HCO3-)
  • pH homeostasis – Carbonic anhydrase facilitates CO2 conversion to HCO3- and H+

• RBCs bend to pass through small capillaries

• Destroyed primarily in the spleen.

• Phagocytic white blood cells remove the debris.

Hematocrit

• The percentage of red blood cells in the blood.
• Typical values:
  • Men: 5 million cells/mm3
  • Women: 4.5 million cells/mm3

Regulation of Red Blood Cells

• The total number of red blood cells is regulated by a negative feedback mechanism involving erythropoietin.
• The kidneys and liver release erythropoietin in response to low oxygen levels.

Dietary Factors Affecting Red Blood Cell Production

• Vitamin B12 and folic acid are needed for DNA synthesis, crucial for cell reproduction, especially in hematopoietic tissue.
• Iron is necessary for hemoglobin synthesis.

Red Blood Cell Diseases

• Anemia: A reduction in hemoglobin or red blood cell concentration in the blood.
• Polycythemia: An excess of erythrocytes, usually caused by cancer, tissue hypoxia, or dehydration but can occur naturally at high elevations.

Explore the essential components and functions of the circulatory system, including blood, blood vessels, and the heart. Learn about the different elements of blood, its plasma composition, and the vital role it plays in maintaining homeostasis in the body.