Human Blood and Erythrocytes Overview

Blood

• Blood circulates through vessels, carrying oxygen and nutrients to cells and removing waste products.
• Total adult blood volume is approximately 5 liters.
• Blood is divided into two main components: plasma (55%) and blood cells (45%).
• Plasma is the liquid portion, composed of 90% water and 10% proteins, salts, nutrients, vitamins, hormones, enzymes, gases, electrolytes, and excretory products.
• Plasma pH remains stable at around 7.4.
• Blood cells are produced in red bone marrow; some white blood cells multiply in lymphoid tissue.
• Blood cells types include red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes).

Erythrocytes (Red Blood Cells, RBCs)

• Main function is carrying oxygen to cells; oxygen binds to hemoglobin, an iron-containing pigment.
• Small, disk-shaped, and lack a nucleus.
• Concentration: approximately 5 million per µL of blood.
• Hemoglobin concentration averages 15 g per dL of blood.
• Life span is about 120 days, requiring constant replacement.
• Production occurs in bone marrow and is regulated by erythropoietin (EPO), a hormone produced in the kidneys.

Leukocytes (White Blood Cells, WBCs)

• Lack hemoglobin and are colorless.
• Varying shapes, with prominent nuclei.
• Total count is approximately 5,000-10,000 per µL, but increases during infection.
• Classified into two groups based on presence of granules: granular leukocytes (granulocytes) and agranulocytes.
• Granulocytes have visible granules, include neutrophils, eosinophils, and basophils.
  • Neutrophils are the most numerous WBC, identified by various-shaped nuclei.
  • Eosinophils and basophils respond to allergic reactions and parasites.
• Agranulocytes lack visible granules, include lymphocytes and monocytes.
  • Lymphocytes are involved in immunity.
  • Monocytes are involved in phagocytosis.

Platelets (Thrombocytes)

• Not cells but small, round or oval fragments.
• Count numbers from 200,000 to 400,000 per µL of blood.
• Important in hemostasis (blood clotting), which prevents blood loss.
• Platelets stick together when a vessel is injured, forming a plug at the site.

Blood Type

• Genetically inherited proteins on the surface of red blood cells.
• ABO and Rh are important groups.
• ABO system includes A, B, AB, and O types; each type has corresponding antibodies.
• Rh system includes Rh-positive (+) and Rh-negative (-) types.
• Blood type matching is crucial for blood transfusions to avoid immune reactions.
• Compatible blood types are determined by cross-matching.
• Whole blood, packed red cells, platelets, plasma, or specific clotting factors may be used in transfusions.

The Immune System

• The body's defense system against foreign matter.

• Nonspecific defenses include unbroken skin, blood-filtering lymphoid tissue, cilia with mucus, bactericidal secretions, and reflexes like coughing/sneezing.

• Specific defenses are mounted by the immune system to attack pathogens.

• Immune response involves interactions between parts of the lymphatic system and the blood.

• Antigens (foreign particles) trigger an immune response involving lymphocytes (a type of WBC.).

• T cells mature in the thymus gland and directly attack foreign cells, while macrophages process antigens.

• B cells mature in lymphoid tissue and produce antibodies (immunoglobulins) to inactivate antigens.

• Antibodies provide long-term immunity to specific organisms.

Medical Terminology Suffixes & Roots

• Suffixes:
  • emia/hemia: Condition of blood.
  • penia: Decrease/deficiency.
  • poiesis: Formation/production.
• Roots:
  • hem/o, hemat/o: Blood.
  • erythr/o, erythrocyt/o: Red blood cell.
  • leuk/o, leukocyt/o: White blood cell.
  • thromb/o, thrombocyte: Blood clot/platelet.
  • immun/o: Immunity.
  • azot/o: Nitrogen compounds.
  • calc/i: Calcium.
  • ferr/o, ferr/i: Iron.
  • sider/o: Iron.
  • kali: Potassium.
  • natri: Sodium.
  • ox/y: Oxygen.

Common Blood Tests

• Measures of red blood cells, white blood cells, hemoglobin, hematocrit, and erythrocyte sedimentation rates.
• CBC, a comprehensive blood count used for various diagnostic purposes.