chapter 19 notes

Chapter Overview

• Focus: Blood and its functions in human anatomy and physiology

• Text adapted from Human Anatomy and Physiology, Third Edition by Pearson Education

• Lectures created by Karen L. Keller at Frostburg State University

19.1 Overview of Blood

Composition of Blood

• Blood: Fluid connective tissue, approximately 5 liters in total volume, about 8% body weight.

• *Components:

  • Plasma: Liquid extracellular matrix (about 55% of blood volume).

  • Formed Elements:

    • Erythrocytes (Red Blood Cells) - responsible for gas exchange.

    • Leukocytes (White Blood Cells) - involved in immune functions.

    • Platelets - cell fragments crucial for blood clotting.

Separation of Blood Components

• Upon centrifugation, blood separates into three layers:

  • Top Layer (Plasma): 55% of blood volume.

  • Middle Layer (Buffy Coat): ~1% of blood volume; contains leukocytes and platelets.

  • Bottom Layer: ~44% of blood volume; consists of erythrocytes.

• Hematocrit: Percentage of blood volume composed of erythrocytes.

19.1 Functions of Blood

Major Functions

• Gas Exchange:

  • Oxygen delivery from lungs to tissues via erythrocytes.

  • Transport of carbon dioxide from tissues to lungs via erythrocytes and plasma.

• Nutrient Distribution: Transports nutrients, hormones, ions, and waste.

• Immune Response: Leukocytes and immune proteins operate within blood to defend against pathogens.

• Temperature Regulation: Carries heat away from tissues to maintain stable body temperature.

• Clotting and Vascular Integrity:

  • Platelets and plasma proteins form clots to seal damaged blood vessels.

• Acid-Base Balance: Maintains pH within the range of 7.35-7.45 through buffer systems.

• Blood Pressure Regulation: Blood volume impacts blood pressure, necessitating volume maintenance.

19.1 Plasma

Characteristics of Plasma

• Slightly yellow liquid comprised mainly of water (90%); it dictates blood viscosity.

• Contains approximately 1% various small solutes including glucose, amino acids, nitrogenous wastes, ions, and gases.

• Plasma Proteins: Make up about 9% of plasma volume; produced mainly in the liver. Examples of these include:

  • Albumin: Responsible for colloid osmotic pressure, drawing water into blood.

  • Immune Proteins (Antibodies): Produced by leukocytes.

  • Clotting Proteins: Form blood clots to stem bleeding.

  • Transport Proteins: Help transport hydrophobic molecules through the blood (e.g., lipoproteins).

Plasma Components Functions

• Water: Primary solvent for solutes and maintains osmotic pressure.

• Plasma Proteins:

  • Albumin: Maintains osmotic pressure.

  • Immune Proteins: Function in immunity.

  • Transport Proteins: Bind and transport hydrophobic compounds.

  • Clotting Proteins: Prevent blood loss.

  • Other Solutes: Supports nutrition, homeostasis, and gas transport.

Cirrhosis

• Definition: Liver disease with various causes (e.g., cancer, alcoholism).

• Consequences: Decrease in plasma proteins leading to complications like edema and coagulopathy.

19.2 Erythrocytes and Oxygen Transport

Erythrocyte Overview

• Constitute ~44% of hematocrit; variance noted between genders (males: 40-50%, females: 36-44%).

• Increased muscle/bone mass, along with higher testosterone levels in males contributes to higher erythrocyte production.

• Erythropoietin (EPO): Hormone stimulating erythrocyte production in response to low oxygen levels in tissues.

Erythrocyte Structure

• Biconcave shape provides a high surface-to-volume ratio crucial for gas exchange.

• Lack nuclei and organelles; primarily composed of hemoglobin (Hb), about 1 billion molecules per cell.

• Hemoglobin Structure: Composed of four polypeptide chains, each with an iron-containing heme group.

• Oxygen Transport: Formation of oxyhemoglobin in oxygen-rich areas (lungs) and deoxyhemoglobin in low-oxygen areas (tissues).

Erythrocyte Lifespan and Production

• Lifespan: 100-120 days due to mechanical stresses as they traverse the circulatory system.

• Hematopoiesis: Formed elements produced from hematopoietic stem cells in the red bone marrow.

• Erythropoiesis: Takes 5-7 days to produce approximately 250 billion cells daily.

• Proerythroblast to reticulocyte differentiation involves erythropoietin and includes hemoglobin synthesis and organelle ejection.

19.2 Anemia

Definition and Causes

• Anemia: Reduced oxygen-carrying capacity of blood; symptoms may include pallor, fatigue, and dyspnea.

• Causes include:

  • Decreased hemoglobin (e.g., Iron-Deficiency Anemia).

  • Decreased hematocrit (e.g., blood loss and pernicious anemia).

  • Abnormal hemoglobin (e.g., Sickle Cell Disease).

Anemia Types

• Iron-Deficiency: Resulting from inadequate iron intake, absorption, or blood loss.

• Pernicious Anemia: Vitamin B12 deficiency affecting DNA synthesis for hematopoiesis.

• Hemolytic Anemia: Caused by excessive erythrocyte destruction (e.g., infections, immune disorders).

• Sickle-Cell Disease: Abnormal hemoglobin leads to sickle-shaped erythrocytes causing blockages and anemia.

Diagnosis

• Complete Blood Count (CBC): Evaluates number and characteristics of blood cells, identifies various anemia types.

19.6 Blood Typing and Matching

Blood Transfusion Basics

• Blood group determination involves antigens present on erythrocytes, crucial for transfusion compatibility.

• ABO Blood Group: Consists of A and B antigens leading to four possible blood types (A, B, AB, O).

• Rh Blood Group: Positive if Rh antigens are present; negative otherwise.

Importance of Cross-Matching

• Agglutination: Occurs when mismatched blood types are transfused, leading to severe reactions.

• Universal Donor: Type O- blood, as it lacks A and B antigens.

• Universal Recipient: AB+ blood allows for maximal compatibility in transfusions.

• Erythroblastosis Fetalis: Immunological condition arising from Rh incompatibility during pregnancy. Preventive measure: Rho(D) immune globulin injection.

19.5 Hemostasis

Overview of Hemostasis

• The process of stopping blood loss, involving five major steps: vascular spasm, platelet plug formation, coagulation, clot retraction, and thrombolysis.

• Mechanism: Vasoconstriction decreases blood flow; platelets aggregate at the injury site forming a temporary plug activated by the von Willebrand factor.

Coagulation Process

• Fibrin Formation: Thrombin converts fibrinogen into fibrin, creating a stable clot.

• Coagulation Cascade: Involves intrinsic and extrinsic pathways converging into a common pathway to activate prothrombin to thrombin, leading to fibrin formation.

Clot Regulation

• Anticoagulants: regulate clot formation through substances like antithrombin and protein C, maintained by endothelial cell activity.

Disorders of Clotting

• Bleeding Disorders: Hemophilia and deficiencies in clotting factors.

• Hypercoagulable Conditions: Conditions leading to abnormal clotting, such as thrombosis and its complications.