Cardiovascular System Overview

Introduction

• Functions:

  • Transport nutrients, oxygen, carbon dioxide, and metabolic wastes.

  • Deliver hormones and enzymes throughout the body.

  • Convey leukocytes to combat infections.

• Additional Functions:

  • Stabilization of body temperature.

  • Clotting process to prevent fluid loss.

  • Maintenance of pH and electrolyte balance.

Functions and Composition of Blood

Components

• Blood consists of:

  • Plasma: Liquid matrix of blood, making up about 55% of blood volume.

  • Formed Elements: Blood cells and fragments, suspended in plasma, including:

    • Erythrocytes (Red Blood Cells): Transport oxygen and carbon dioxide.

    • Leukocytes (White Blood Cells): Immune function.

    • Platelets: Involved in clotting.

Blood Composition

• Plasma Composition:

  • 92% water

  • 7% plasma proteins:

    • Albumins: 60% - contribute to osmotic pressure and transport substances.

    • Globulins: 35% - transport ions and immune functions.

    • Fibrinogen: 4% - essential for clotting, converts to fibrin.

  • 1% other solutes (electrolytes, nutrients, wastes).

Viscosities of Blood

• Whole blood has a viscosity that contributes to its flow properties.

• Blood can be fractionated into:

  • Plasma

  • Packed Cells (primarily erythrocytes)

  • Platelets

Normal Blood Volume

• Approximately 7% of body weight:

  • Males: 4–6 liters

  • Females: 4–5 liters

• Blood pH: 7.35–7.45

Blood Components

Formed Elements

• Comprise about 45% of whole blood.

• Found in blood:

  • Erythrocytes: >99.9% of formed elements.

  • Leukocytes: <0.1% (neutrophils, eosinophils, basophils, lymphocytes, monocytes).

  • Platelets: <0.1%.

Red Blood Cells (RBCs)

• Structure:

  • Biconcave disc, about 7.7 microns in diameter, without organelles or nucleus.

  • Contain hemoglobin (up to 95% of protein content).

• Life Span: About 120 days; do not repair themselves.

Hemoglobin Function

• Consists of:

  • 4 polypeptide subunits (2 alpha, 2 beta chains) with heme groups that bind iron and thus oxygen.

  • Responsible for oxygen and carbon dioxide transport without competition for binding sites.

Blood Types

• Determined by surface antigens (agglutinogens) on erythrocytes:

  • Type A: A agglutinogen, b agglutinin.

  • Type B: B agglutinogen, a agglutinin.

  • Type AB: Both A and B agglutinogens, no agglutinin.

  • Type O: No A or B agglutinogens, both a and b agglutinins.

  • Rh Factor: Presence of D antigen (Rh positive) versus absence (Rh negative).

White Blood Cells (Leukocytes)

• Comprised of:

  • Granulocytes: Neutrophils, eosinophils, basophils.

  • Agranulocytes: Monocytes and lymphocytes.

• Total count: 6000 to 9000 per microliter of blood, with short life spans typically resolved within days.

• Can perform diapedesis and follow chemicals released to infection sites (chemotaxis).

Platelets

• Function in hemostasis (clotting); derived from megakaryocytes.

• Approximately 350,000 per microliter of blood; involved in clotting by forming a plug and initiating the clotting process.

Hemopoiesis (Blood Formation)

Overview of Hemopoiesis

• Process begins with hematopoietic stem cells differentiating into myeloid and lymphatic stem cells.

Erythropoiesis (RBC Formation)

• Occurs primarily in red bone marrow, stimulated by erythropoietin from kidneys/liver during hypoxia.

• Key nutrients include vitamin B12.

• Steps include:

  • Pluripotential stem cells to myeloid stem cells, to progenitor cells, then to erythroblast stages and finally to erythrocytes.

Leukopoiesis (WBC Formation)

• Occurs within red bone marrow and peripheral lymphatic tissues; differentiation leads to various types of leukocytes.

Conclusion

• Understanding the cardiovascular system components, functions, and the life cycle of blood cells is crucial for a comprehensive grasp of human physiology and overall health.