Blood Composition & RBCs

Blood composition consists of:
- Formed elements (cellular components)
- Plasma (liquid component)

Definition: The proportion of blood volume that is composed of red blood cells (RBCs).
Hematocrit Values:
- Typical percentages of RBCs:
- Males: 47% ± 5%
- Females: 42% ± 5%

**Composition of Formed Elements in Blood:
- Erythrocytes (RBCs): 4-6 trillion /L
- Leukocytes (WBCs): 4-11 billion /L
- Thrombocytes (Platelets): 150-450 billion /L**

Physical Characteristics of Blood:
- Sticky, opaque fluid with a metallic taste due to iron.
- Viscosity: 3-4 times thicker than water.
- Color:
- High O₂: Ruby red
- Low O₂: Dark red
- pH: Not explicitly mentioned in the provided data.
Average blood volume:
- Males: 5-6 L
- Females: 4-5 L
- Note: Blood donors typically provide 1 pint (~500 mL).

Composition:
- Consists of 90% water and over 100 dissolved solutes, including:
- Inorganic ions
- Nutrients
- Gases
- Hormones
- Wastes
- Proteins
Significant Ions in Plasma (mOsmol/L):
- Na⁺: 144
- Cl⁻: 107
- HCO₃⁻: 27
- K⁺: 5
- Ca²⁺: 2.5
- Total Plasma Osmolarity: 295.7 mOsmol/L
Plasma Proteins: Most abundant solutes by weight, produced mostly by the liver, include:
- Albumin (~60%): Affects osmotic pressure and serves as a carrier for ions and hydrophobic molecules.
- Globulins (~36%): Includes antibodies and blood clotting factors.
- Fibrinogen (~4%): Inactive blood clotting factor.
Serum: Defined as plasma without clotting factor proteins.

Major Functions of Blood:
- Distribution: Carries oxygen, nutrients, and hormones to cells and removes carbon dioxide and waste products.
- Regulation: Maintains body temperature, pH, and fluid balance.
- Protection: Hemostasis (clotting) and immune defense against pathogens.

Common Blood Analyte Tests:
- Glucose, electrolytes (Na⁺, K⁺, Ca²⁺), hormones, blood proteins.
Comprehensive Metabolic Profile (CMP): A blood chemistry analysis used for diagnosing liver and kidney disorders.
Erythrocyte Tests: Hematocrit measurement for anemia (low) or polycythemia (high).
Microscopy: Assessment of variations in size (Mean Cellular Volume, MCV) and shape of RBCs.
Leukocyte Tests: Differential WBC count used in diagnosing leukemia or infections.
Thrombocyte Tests: Platelet counts assess hemostasis (blood clotting).
Complete Blood Count (CBC): Evaluates all formed elements and hemoglobin levels.

Physical Characteristics:
- Shape: Biconcave discs, anucleate (lack a nucleus), and contain no organelles, including mitochondria.
- Function: Transport O₂, CO₂, and H⁺ ions, and inadvertently CO (carbon monoxide).
- Hemoglobin Content: >97% hemoglobin, crucial for gas transport and contributes to blood viscosity.

Adult Hemoglobin: Composed of globin polypeptides (2 alpha and 2 beta chains) and heme.
- Each RBC contains approximately 250 million hemoglobin molecules.
Fetal Hemoglobin: Contains 2 alpha and 2 gamma globin polypeptides.

O₂ Loading and Unloading:
- O₂ loading occurs in the lungs forming oxyhemoglobin (ruby red, transmits more red light).
- O₂ unloading occurs in tissues, resulting in deoxyhemoglobin (dark red, absorbs more red light).
CO₂ Binding in Tissues:
- 20-30% of CO₂ in blood binds to globin proteins, forming carbaminohemoglobin.
Carbon Monoxide (CO): Binds to iron in heme, posing a poisoning risk, discussed in relation to the respiratory system in further detail.

Concepts relating to blood composition, functions, and test diagnostics provide foundational knowledge for understanding physiological processes and related pathologies amid a clinical context.