RB

A_P_Week_1_Blood

Blood: Chapter 18 Overview

Learning Objectives

  • 4.1 Functions of cardiovascular system components

  • 4.2 General characteristics of blood (color, volume, pH, viscosity)

  • 4.3 Roles of blood plasma and formed elements

  • 4.4 Define hematocrit; normal ranges in adults

  • 4.5 Major plasma proteins, their functions, site of production

  • 4.6 Structure and function of erythrocytes

  • 4.7 Chemical structure and function of hemoglobin

  • 4.8 Life cycle of red blood cells and destruction products

  • 4.9 Stimulation and process of erythropoiesis

  • 4.10 ABO and Rh blood types

  • 4.11 Five types of leukocytes and their functions

  • 4.12 Three major stages of hemostasis

  • 4.13 Factors promoting or preventing coagulation

Overview of Blood

  • Connective tissue with:

    • Extracellular matrix: Plasma

    • Cellular elements: Formed elements

      • Erythrocytes: Red blood cells

      • Leukocytes: White blood cells

      • Platelets: Thrombocytes

Functions of Blood

  • Transportation: Nutrients, gases, hormones, and waste

  • Protection: Immune response and clotting

  • Homeostasis maintenance: Regulating temperature, pH, and fluid balance

Composition of Blood

  • Plasma: 55% of blood; contains water, proteins, nutrients, hormones, electrolytes

  • Formed Elements: 45% of blood; includes erythrocytes, leukocytes, and platelets

  • Hematocrit: Measures the percentage of red blood cells in total blood volume

    • Normal adult males: 42%-52%

    • Normal adult females: 37%-47%

    • Anemia: low hematocrit

    • Polycythemia: high hematocrit

Characteristics of Blood

  • Color: Varies with oxygen saturation

  • Viscosity: ~5 times that of water

  • Temperature: ~38°C (higher than body temperature)

  • pH: 7.35-7.45 (average 7.4)

  • Volume: About 8% of body weight (5-6L in males, 4-5L in females)

Plasma Proteins and Their Functions

  • Albumin: 54-60% of proteins; maintains osmotic pressure, transports molecules (Liver)

  • Globulins: 35-38% of proteins; transport (Alpha, Beta, Gamma) - immune responses (Plasma cells)

  • Fibrinogen: 4-7%; critical for blood clotting (Liver)

Formed Elements of Blood

  • Erythrocytes: Transport oxygen and some carbon dioxide

    • Lifespan: ~120 days

    • Structure: Biconcave disc, no nucleus, contains hemoglobin

  • Leukocytes: Immune defenses, categorized into granulocytes and agranulocytes

    • Types: Neutrophils, eosinophils, basophils (granulocytes); lymphocytes, monocytes (agranulocytes)

  • Platelets: Cytoplasmic fragments aiding in hemostasis

Erythropoiesis

  • Formation of erythrocytes from hematopoietic stem cells in red bone marrow

  • Regulated by erythropoietin (EPO) released in response to low oxygen levels

  • Requires essential nutrients: Iron, Vitamin B12, folic acid

Life Cycle of Erythrocytes

  1. Produced in bone marrow; released into circulation.

  2. Circulate for about 120 days.

  3. Old erythrocytes are phagocytized by macrophages in various organs.

  4. Components (heme, globin) are recycled; iron stored in liver as ferritin.

Disorders of Erythrocytes

  • Anemia: Decreased RBCs, leading to reduced oxygen carrying capacity.

    • Types include: Iron-deficient anemia, sickle cell disease, aplastic anemia

Leukocytes

  • Protect against disease, have a shorter lifespan than RBCs.

  • Granulocytes: Neutrophils (first responders, phagocytosis), eosinophils (combat parasites), basophils (inflammation).

  • Agranulocytes: Lymphocytes (adaptive immunity), monocytes (become macrophages).

Hemostasis: Stopping of Bleeding

  1. Vascular Spasm: Initial constriction of blood vessels.

  2. Platelet Plug Formation: Platelets adhere to injury site and activate each other.

  3. Coagulation: Fibrin mesh forms to stabilize the clot, trapping erythrocytes and more platelets.

Blood Typing and Rh Factor

  • Blood types determined by antigens on RBC surfaces (A, B, AB, O).

  • ABO Group: Antigens A and B determine compatibility.

  • Rh Factor: Presence (positive) or absence (negative) of Rh antigens; important in transfusions and pregnancy (Rh incompatibility).

Conclusion

  • Understanding blood components, functions, and disorders is critical for studying the cardiovascular system and its health implications.