cardiovascular system pt. 1
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.