Human Blood - Key Concepts and Terminology

AP 2 Lab: Human Blood

Blood-Internal Transport System

  • Source: ©2016 Pearson Education, Inc.

Physical Characteristics and Volume

  • Characteristics:

    • Blood is a sticky, opaque fluid with a metallic taste.

    • It is denser and more viscous than water (H2O).

  • pH Level: 7.35-7.45

  • Temperature: 38°C

  • Color Variation:

    • High O2 levels: Scarlet red

    • Low O2 levels: Dark red

  • Volume:

    • Blood makes up approximately 8% of body weight.

    • Average blood volume:

    • Males: 5–6 L

    • Females: 4–5 L

Blood Functions

  • Distribution Functions:

    • Oxygen delivery

    • Nutrient transport

    • Waste removal

    • Hormonal distribution

  • Regulation Functions:

    • Temperature regulation by absorbing and distributing heat.

    • pH maintenance through buffers; alkaline reserve includes bicarbonate ions.

    • Fluid volume regulation in the circulatory system.

  • Protection Functions:

    • Prevention of fluid loss through clotting mechanisms.

    • Prevention of infections by carrying immune agents in blood (e.g., antibodies, complement proteins, white blood cells).

Composition of Blood

  • Blood is classified as the only fluid tissue in the body and is a type of connective tissue.

  • Components:

    • Matrix (nonliving fluid): Plasma

    • Living cells: Formed elements suspended in plasma.

  • Formed Elements:

    • Erythrocytes (Red Blood Cells, RBCs)

    • Leukocytes (White Blood Cells, WBCs)

    • Platelets

Formed Elements of Whole Blood

  • Characteristics of Formed Elements:

    • Comprised of RBCs, WBCs, and platelets.

    • Only WBCs are complete cells; RBCs lack nuclei and organelles, while platelets are cell fragments.

    • Most formed elements have a short lifespan in the bloodstream (a few days).

    • Origination predominantly from bone marrow; formed elements do not divide.

Composition of Whole Blood

  • A spun tube of blood separates into three layers:

    1. Plasma (top, approximately 55%)

    2. Buffy Coat (middle, less than 1%): Contains WBCs and platelets, a thin whitish layer between RBCs and plasma.

    3. Erythrocytes (bottom, about 45% of whole blood).

Major Components of Whole Blood

  • Plasma:

    • Constitutes 55% of whole blood.

    • Least dense component.

  • Buffy Coat:

    • Contains leukocytes and platelets.

    • Less than 1% of whole blood.

  • Erythrocytes:

    • Comprise 45% of whole blood (hematocrit).

    • The most dense component of blood.

Blood Plasma

  • Characteristics of Plasma:

    • Sticky and straw-colored.

    • Composed of 90% water.

  • Plasma Proteins:

    • Albumins: Most abundant protein, constituting 60% of plasma proteins.

    • Globulins

    • Fibrinogen

    • Prothrombin

    • Other Regulatory Proteins: Include enzymes and hormones.

  • Other Solutes Present in Plasma:

    • Electrolytes

    • Organic nutrients

    • Organic wastes

    • Buffers

Hematocrit Measurement

  • Definition: A measure of the percentage of whole blood occupied by RBCs.

  • Hematocrit Values:

    • Average in males: 46% (range of 40-54%).

    • Average in females: 42% (range of 37-47%).

    • Androgens stimulate RBC synthesis; estrogens do not.

  • Clinical Significance:

    • Low hematocrit values may indicate anemia.

    • High hematocrit values may suggest polycythemia.

Microhematocrit Centrifuge

  • Caution: This cover must be locked in place prior to operation.

Microhematocrit Tube Before and After Centrifugation

  • Components Being Measured:

    • Plasma

    • White blood cells and platelets

    • Red blood cells

Erythrocyte Sedimentation Rate (ESR)

  • Definition: ESR measures the rate at which red blood cells sediment over a one-hour period.

  • Nature of the Test: A common hematology test, serving as a non-specific measure of inflammation.

  • Testing Protocol:

    • Anticoagulated blood is placed in a vertical tube (Westergren tube).

    • The rate of sedimentation is reported in mm/h.

ESR and Inflammation

  • Factors Influencing ESR:

    • Governed by pro-sedimentation factors such as fibrinogen and resistance factors like the negative charge of RBCs.

    • Inflammatory processes increase fibrinogen, causing red blood cells to adhere to one another, forming stacks called 'rouleaux formation' which settle more quickly.

    • An increase in ESR may indicate inflammation.

Rouleaux Formation

  • Description: Red blood cells stack together in a coin-like formation.

Hemoglobin (Hb)

  • Definition: Hemoglobin is the protein molecule in RBCs responsible for oxygen transport from the lungs to body tissues and for returning carbon dioxide from tissues back to the lungs.

  • Measurement Context: Hemoglobin levels are part of the complete blood count (CBC).

Hemoglobin Values

  • Measurement Units: Grams (g) per deciliter (dL) of whole blood.

  • Normal ranges for adults:

    • Males: 14 to 18 g/dL

    • Females: 12 to 16 g/dL

    • Males after middle age: 12.4 to 14.9 g/dL

    • Females after middle age: 11.7 to 13.8 g/dL

Blood Types

  • Genetic Determination: Human blood groups are genetically determined; ABO and Rh systems are primarily implicated in transfusion issues.

  • Known Blood Groups: Over 90 different groups based on antigens present on the surface of RBCs.

ABO Blood Group System

  • Antigens: Two antigens (A and B) are present on the RBC surface.

  • Antibody Production: The body naturally produces antibodies against the missing antigen:

    • Group A: A antigen; B antibodies.

    • Group B: B antigen; A antibodies.

    • Group AB: A and B antigens; no antibodies.

    • Group O: No antigens; A and B antibodies.

Agglutination and Hemolysis

  • Impact of ABO Antibodies: These antibodies can cause agglutination (clumping) of red blood cells. D antibodies can result in hemolysis (destruction of RBCs).

  • Related Conditions:

    • Erythroblastosis fetalis (HDN)

    • Transfusion reactions

Rh Factor

  • Rh Blood Type: Identified by C, D, and E antigens (with D being the most antigenic).

  • Rh Status:

    • Rh+: Presence of D antigens.

    • Rh-: Absence of D antigens.

  • Antibody Formation: Antibodies against D develop only post-exposure to the antigen.

Blood Cell Types and Their Counts

  • Formed Elements of Blood: Number of cells per mm³ of blood:

    • Erythrocytes: 4-6 million

    • Leukocytes: 4,000-11,000

    • Neutrophils: 3,000-7,000

    • Lymphocytes: 1,500-3,000

    • Monocytes: 100-700

    • Eosinophils: 100-400

    • Basophils: 20-50

    • Platelets: 250,000-500,000

Visual Identification of Blood Cells

  • Components:

    • Neutrophils

    • Platelets

    • Erythrocytes (RBC)

    • Eosinophils

  • Mnemonic to Remember Cell Types:

    • Never (Neutrophil)

    • Let (Lymphocyte)

    • Monkeys (Monocyte)

    • Eat (Eosinophil)

    • Bananas (Basophil)

White Blood Cells Characteristics

  • Neutrophils: Note three-lobed nucleus.

  • Lymphocytes: Nucleus nearly fills the cytoplasm.

  • Monocytes:

    • Kidney or horse-shoe shaped nucleus.

    • Largest WBC in circulation; migratory to tissues, differentiating into macrophages.

    • Fixed group: alveolar macrophages in lungs, Kupffer cells in liver.

    • Wandering group: Gather at infection sites.

    • Diameter: 12-20 microns; cytoplasm appears a foamy blue-gray.

    • Comprises 3-8% of circulating WBCs.

Eosinophils and Basophils

  • Eosinophils: Characterized by bi-lobed nucleus, around 100-400 cells/mm³.

  • Basophils: Approx. 20-50 cells/mm³, noted for their distinct size and granulation.

Clinical Conditions Related to Blood

  • Acute Myelogenous Leukemia: Characterized by atypical leukocytes.

  • Polycythemia: Condition where red blood cells are elevated (around 20%).

  • Sickle Cell Disease: A genetic disorder affecting hemoglobin.

  • Iron Deficiency Anemia: A condition indicating low hemoglobin levels.

Blood Testing Procedures

  • Blood Testing Kit: Includes blood drawing and typing components.

  • Lancets: For obtaining blood samples; typically used in along with alcohol swabs for sanitation.

Antibody Solutions in Blood Testing

  • Monoclonal Antibodies: Specific antibodies for blood typing:

    • Anti-A

    • Anti-B

    • Anti-D

  • Storage Instructions: Maintain at 2-8°C; do not freeze the solutions.

Blood Test Card

  • Procedure: Mixing Blood Samples:

    • Place serum in blood test card along with corresponding antibodies (Anti-A, Anti-B, Anti-D).

    • Observe for agglutination to determine blood type.