BIOL 1720: Fluid Exchange

Overview of Fluid Exchange in the Body

Forces Involved in Fluid Exchange

  • Driving Force: Blood pressure in capillaries driving fluid out into the interstitial space.

  • Opposing Force: Osmotic pressure pulling fluid back into capillaries.

    • Definition of Osmotic Pressure: Caused by the presence of proteins in the blood that are not found in interstitial fluid. Only a minimal amount of protein leaks into the interstitial space.

Interstitial Space

  • Definition: The space between cells, filled with fluid.

  • Fluid Composition: Similar to blood but lacks significant protein and blood cells, except possibly at sites of infection or injury.

Fluid Dynamics and Edema

  • Fluid Loss: Body normally loses 4 to 8 liters of fluid from blood into interstitial space daily.

  • Lymphatic System:

    • Role: Returns fluid back to blood and prevents edema.

    • Connection: Lymphatic vessels return fluid to the blood at the base of the neck.

Mechanism of Lymphatic Fluid Movement

  • Pressure Gradients: Fluid moves into lymphatic vessels due to hydrostatic pressure from water accumulation in interstitial space.

  • Permeability: Lymphatic vessels allow free movement of water due to their high permeability.

Composition of Blood

Cellular Components

  • Red Blood Cells (Erythrocytes): Main component responsible for oxygen transport.

  • White Blood Cells (Leukocytes): Include various types involved in immune responses.

  • Platelets: Cellular fragments crucial for blood clotting.

    • Origin: Derived from megakaryocytes in the bone marrow.

Liquid Matrix

  • Plasma Composition:

    • Proteins: Albumin, antibodies, hormones

    • Nutrients

    • Electrolytes: Sodium, potassium, calcium, bicarbonate

Function of Blood Components

  • Albumin: Maintains osmolarity and pH balance in blood.

  • Calcium: Serves as a second messenger and is vital for muscle contraction.

  • Sodium and Potassium: Help maintain membrane potential.

  • Fibrinogen: Precursor to fibrin, important in clot formation.

Red Blood Cell Production and Lifecycle

  • Erythropoiesis: Stimulated by erythropoietin (EPO), produced in kidneys.

    • Significance: Patients with kidney failure can suffer from anemia due to lack of EPO.

  • Lifespan: Red blood cells live for approximately 120 days and must be continuously produced.

  • Anemia Causes:

    • Insufficient hemoglobin production (iron deficiency)

    • Excessive destruction of red blood cells

Sickle Cell Disease

  • Cause: Genetic mutation changes one amino acid in hemoglobin, altering red blood cell shape and function.

  • Implications: The sickle shape can lead to red blood cell destruction and anemia, reducing oxygen transport.

Clotting Mechanism

Importance of Clots

  • Function: Clots prevent blood loss when vessels are damaged.

  • Process: Collection of platelets form a temporary plug over the injury site.

Pathways of Clotting

  • Intrinsic Pathway: Triggered by exposed collagen and involves factors 12, 11, 9, 8, and ultimately activates factor 10, converting prothrombin to thrombin.

  • Extrinsic Pathway: Triggered by tissue factor (factor 3) which interacts with factor 7 to also activate factor 10.

    • Pathways converge at the activation of factor 10.

Clot Formation and Resolution

  • Role of Thrombin: Converts fibrinogen to fibrin, which reinforces the platelet plug and traps blood cells to form a stable clot.

  • Anti-Clotting Factors:

    • Plasminogen, activated to plasmin, dissolves clots post-healing to prevent excessive clotting.

Thrombus Formation and Implications

  • Risks: Thrombus can block blood flow in coronary arteries (causing myocardial infarction) or in the brain (causing strokes).

Management of Clotting Issues

Treatments for Clot Formation

  • Thrombolytics: e.g., tissue plasminogen activator (TPA), dissolves clots by converting plasminogen to plasmin.

  • Aspirin: Inhibits thromboxane synthesis, reducing platelet aggregation.

Cardiovascular Health and Risk Factors

Common Risk Factors for Cardiovascular Disease

  • Hypertension: Primary risk factor causing chronic damage to blood vessels leading to atherosclerosis.

  • Obesity and Diabetes: Major contributing factors to cardiovascular disease.

Treatment for Hypertension

  • Statins: Lower LDL cholesterol levels.

  • Beta Blockers: Reduce heart rate and overall cardiac output.

  • Calcium Channel Blockers: Cause vasodilation, reducing blood pressure.

  • Diuretics: Help remove excess fluids, reducing blood volume and pressure.

Brief Overview of the Respiratory System

  • Function: Gas exchange of oxygen and carbon dioxide occurring in the alveoli of the lungs.

  • Ventilation Mechanism: Air flow is driven by pressure gradients created by lung volume changes during inhalation and exhalation.

  • Negative Pressure Breathing: Lung expansion creates lower pressure, drawing air in when inhaling.

Partial Pressure Calculations

  • Equation: Partial pressure of oxygen in air can be calculated by the formula:

    extPartialPressureofO<em>2=extFractionofO</em>2imesextAtmosphericPressureext{Partial Pressure of O}<em>2 = ext{Fraction of O}</em>2 imes ext{Atmospheric Pressure}

    • Example: At atmospheric pressure of 760 mmHg, the partial pressure of oxygen would be 0.21imes7600.21 imes 760 which equals approximately 160 mmHg.

Conclusion

  • Understanding of Cardiovascular and Respiratory Systems: Essential knowledge for managing health and diseases related to these systems.