Blood Function and Components

Blood Function and Components

• Oxygen Transport: Red blood cells (RBCs) carry oxygen, bound to hemoglobin. Oxygen is absorbed in the lungs and released in tissues. Anemia results from low RBCs or hemoglobin (leading to hypoxia), while excess RBCs (polycythemia) often stem from conditions like chronic obstructive pulmonary disease (COPD).

• Infection Defense: White blood cells (WBCs) fight infection.

• Neutrophils: Main responders to bacterial infections; elevated counts (neutrophilia) signal acute bacterial infections.

• Eosinophils: Elevations point towards parasitic infections or allergic reactions (e.g., asthma, eczema).

• Basophils: Rarely elevated; relevant to hypersensitivity reactions and chronic myelogenous leukemia.

• Lymphocytes: Include T cells (cytotoxic and helper) and B cells. T cells directly kill infected cells and coordinate the immune response, B cells produce antibodies.

• Monocytes: Differentiate into macrophages to clear debris and present antigens.

• Hemostasis: Blood clotting involves two stages.

• Primary hemostasis: Platelets adhere to exposed collagen; this forms a platelet plug.

• Secondary hemostasis: A clotting cascade activates fibrin to stabilize the plug. von Willebrand disease is a condition related to defective platelet adhesion from decreased von Willebrand factor. Hemophilia is an X-linked bleeding disorder impacting factors VIII (A) or IX (B).

Clinical Clues for Platelet Issues

• Platelet dysfunction can occur with normal platelet counts due to antiplatelet drugs or conditions such as uremia.

• Thrombocytopenia (low platelet count) has causes like immune thrombocytopenia purpura (ITP), an immune-mediated platelet destruction, often linked to viral illnesses or autoimmune conditions. Heparin-induced thrombocytopenia (HIT) occurs due to an adverse heparin response.

Lab Values and Trends

• WBCs (white blood cells): Normal range is 4,500-11,000/μL. Increased counts (leukocytosis) suggest infections, inflammation, or stress, decreased counts (leukopenia) suggest chemotherapy, radiation, or bone marrow failure.

• Platelets: Normal range is 150,000-400,000/μL. Significant departures from this range can indicate potential issues.

• Trend analysis: A "normal" lab value may mask a significant health concern. For example an abrupt decrease in platelet counts from 200,000/µL to 100,000/µL despite being "normal" indicates a potential rapid consumption or destruction of platelets.

Hemoglobin and Hematocrit

• Hemoglobin (Hgb): Measures the oxygen-carrying capacity of blood. Low Hgb can result from blood loss, chronic illnesses, or nutritional deficiencies; high Hgb can be found in dehydration or hypoxia-driven red blood cell production.

• Hematocrit (Hct): Represents the proportion of red blood cells in the blood. Variations in Hct are linked to hemodilution (e.g. from IV fluids, pregnancy) or hemoconcentration (e.g. dehydration).

Types of Anemia

• Microcytic anemia (iron deficiency): Characterized by small, pale red blood cells due to reduced iron, impacting hemoglobin synthesis. Causes include chronic blood loss (menstrual, GI), inadequate iron intake, or malabsorption issues (celiac disease). Symptoms include fatigue, pallor, brittle nails, angular cheilitis, and/or pica.

• Macrocytic anemia (folate or B12 deficiency): Large, immature red blood cells stem from impaired DNA synthesis and cell division.

• Vitamin B12 deficiency: Causes include pernicious anemia, gastric surgery, or malabsorption issues. Signs often include glossitis and potential neurological deficits.

• Folate deficiency: Often arises from insufficient intake or increased demand during pregnancy or hemolysis. Similar symptoms to B12 deficiency, but typically lacking neurological involvement.

Jaundice and Bilirubin

• Bilirubin metabolism: Bilirubin is produced from hemoglobin breakdown. Two forms exist:
• Unconjugated (indirect): Elevated levels indicate hemolysis or Gilbert's syndrome, where bilirubin is not adequately processed by the liver.
• Conjugated (direct): Elevated levels are associated with biliary obstruction, liver diseases like hepatitis, or cholestasis, reflecting impairment in bilirubin processing & excretion.

Transfusion Guidelines

• Transfusion thresholds: Triggers for blood transfusions are largely based on hemoglobin levels.

Explore the vital functions and components of blood including oxygen transport, infection defense, and the roles of various blood cells. Understand how red blood cells, white blood cells, and their subdivisions contribute to overall health and disease. This quiz covers essential concepts found in biology and human physiology.