BIOL 2404: chapter 10 Blood
Blood Composition
Main Components:
Formed Elements
Refers to the type of cells found in blood, which includes:
Red Blood Cells (erythrocytes)
White Blood Cells (leukocytes)
Different types categorized later
Platelets (not full cells, fragments of cells)
Plasma
Non-cellular component of blood
Mainly consists of water and its dissolved contents
Proteins, hormones, respiratory gases
Blood Separation
Process of Blood Separation:
Blood samples drawn for testing
Sample is placed in a centrifuge to separate layers:
Erythrocytes (Red Blood Cells) sink to the bottom, which occupies about 45% of the volume.
This layer also referred to as Hematocrit.
Buffy Coat is the middle layer containing:
Leukocytes (White Blood Cells)
Platelets (clotting cell fragments)
Represents around 1% of total volume.
Plasma is the liquid top layer, approximately 55% of the total volume:
Mainly water (about 90% of plasma).
Clinical Relevance:
Hematocrit Value: A hematocrit level of <45% indicates insufficient red blood cells, suggesting potential oxygen delivery issues and overall body dysfunction.
Plasma Level: If plasma volume drops below 55%, it may indicate dehydration.
Blood Characteristics
Color:
Normal blood is scarlet red (well oxygenated).
If blood appears bluish/purplish, it indicates deoxygenation.
Taste:
Blood has a metallic taste due to iron (important for oxygen transport).
pH Level:
Blood should be maintained between 7.35 and 7.45 (slightly alkaline).
Levels above or below this range cause sickness and indicate issues needing health intervention.
Body Temperature:
Blood temperature is slightly higher than normal body temperature; typically around 100°F.
Volume of Blood in Adults:
An average adult has 5 to 6 liters of blood.
Plasma Composition
Plasma makes up 55% of blood:
Consists mostly of:
Water - about 90% of plasma volume.
Nutrients, salts, electrolytes (e.g., sodium, potassium).
Hormones - carried from glands to tissues.
Proteins:
Antibodies - for immune system function.
Albumin - helps maintain osmotic pressure (blood pressure).
Clotting Proteins - prevent blood loss during injury.
Waste Products - materials the body must eliminate.
Formed Elements of Blood
Types of Cells in Formed Elements:
Erythrocytes (Red Blood Cells):
Function: Carry oxygen throughout the body.
Unique characteristics:
Anucleate (no nucleus)
Filled with hemoglobin (protein that binds oxygen).
Life span: Approximately 100-120 days.
Count: 5 million cells/mm³ (normal).
Conditions related to erythrocytes:
Anemia: Capacity to carry oxygen is reduced, leading to energy deficits and potential organ failure.
Types of Anemia:
Sickle Cell Anemia: Abnormal hemoglobin causes red cells to change shape, restricting oxygen transport.
Hemorrhagic Anemia: Resulting from blood loss; blood transfusion is treatment.
Iron Deficiency Anemia: Lacking iron affects hemoglobin production.
Aplastic Anemia: Bone marrow issues affect production.
Polycythemia: Excessive red blood cells, which may indicate health issues or adaptation to high altitudes.
Leukocytes (White Blood Cells):
Function: Protect the body against pathogens (bacteria, viruses, etc.).
Characteristics:
Complete cells with organelles and nuclei.
Capable of exiting blood to combat infection through a process called chemotaxis (migration towards chemical signals).
Count: Ranges between 4,800 - 10,800 cells/mm³.
Types of White Blood Cells:
Neutrophils: First responders to infection, most abundant (3,000 - 7,000 cells/mm³); indicate infection if elevated.
Eosinophils: Involved in combating parasites and allergic responses (100 - 400 cells/mm³).
Basophils: Release heparin as an anticoagulant, aiding in preventing excessive clotting during injuries (under 1%).
Monocytes: Transform into macrophages to fight long-term infections (700 cells/mm³); higher levels indicate chronic infections.
Lymphocytes: Critical for the immune response, including the formation of antibodies and memory cells for pathogens (1,500 - 3,000 cells/mm³).
Platelets (Thrombocytes):
Fragments involved in blood clotting:
Count: 300,000 cells/mm³.
Involved in hemostasis: preventing blood loss through clot formation.
Hematopoiesis
Blood Cell Formation:
Occurs in the red bone marrow from a common stem cell called hemocytoblast. These stem cells differentiate into specific blood cell types based on the body's needs:
Lymphoid cells lead to lymphocytes; Myeloid cells produce platelets, red cells, and other types of white cells.
Erythropoietin hormone stimulates the production of red blood cells, released by the kidneys in response to low oxygen levels.
Thrombopoietin hormone stimulates the production of platelets when the body senses infection or blood loss.
Hemostasis
Definition: Process of stopping bleeding, distinct from homeostasis (maintaining internal stable conditions).
Steps of Hemostasis:
Vascular spasm - Initial constriction of blood vessels.
Platelet plug formation - Temporary aggregation of platelets at the injury site.
Coagulation - Formation of stable blood clots via tissue factors and proteins to ensure long-term sealing of the wound.
Disorders of Hemostasis:
Thrombus: Unbroken clot in a blood vessel leading to blockages.
Embolus: A dislodged thrombus that can travel and block circulation elsewhere.
Thrombocytopenia: Low platelet count leading to excessive bleeding.
Hemophilia: Inability to produce effective clotting proteins leading to dangerous bleeding disorders.
Clinical Implications of Blood Loss
Symptoms of Blood Volume Loss:
Loss of 15 - 30% blood causes weakness due to lack of oxygenation.
Loss of more than 30% can lead to shock and organ failure due to insufficient oxygen supply to organs.
Treatment for Severe Blood Loss:
Blood transfusions are often necessary to restore blood volume and improve oxygenation.
Blood Compatibility and Transfusions
Understanding blood types is critical for safe transfusions:
Different blood types (A, B, AB, O) have specific compatibility rules.
Know why certain blood types can receive from or donate to others, not just the memorization of facts.