Physiology Ch. 2 Blood

Physiology (0603302) Ch.2 Blood

• Blood is a liquid connective tissue that circulates through blood vessels, driven by the heart's pumping action.

Functions

• Transportation:
  • Transports nutrients (amino acids, lipids, glucose), hormones, and oxygen to cells.
  • Transports waste products and carbon dioxide away from cells.
• Regulation:
  • pH buffering (7.35-7.45): maintaining the balance of hydrogen and bicarbonate ions.
  • Body temperature regulation: through mechanisms like water and vasodilation.
• Protection:
  • Clot formation: minimizes blood loss when a vessel is damaged.
  • Protection against foreign substances (pathogens): Antibodies and white blood cells (WBCs) play a critical role.

Blood Volume

• Males: 5-6 liters
• Females: 4-5 liters
• Volume varies based on individual size and gender.

Blood Color

• Arterial blood is bright red (high oxygen level).
• Venous blood is a darker red (less oxygen). Tissues absorb oxygen.

Blood pH

• Arterial blood: 7.35-7.45
• Venous blood: 7.32-7.42 (slightly lower due to CO2 buildup)

Blood Composition

• Cellular portion (formed elements):
  • Lower portion of a blood sample (Buffy coat + RBCs)
• Fluid portion (plasma):
  • Upper portion of a blood sample
  • 55% of total blood volume
  • ~ 91-92% water
  • ~ 6-8% proteins
    • Albumin: 60%; maintains blood volume and blood pressure; transports proteins and steroid hormones
    • Globulins: 35%; transports hydrophobic lipids, fat-soluble vitamins, ions, and hormones
    • Fibrinogen: 4%; coagulation protein
    • Regulatory proteins: less than 1%; Enzymes, proenzymes, and hormones.
  • ~ 1-2% other solutes (electrolytes, nutrients, waste products, and gases).

Components of Blood

• Erythrocytes (red blood cells):
  • 4.6-6.2 million cells/mm³ (males) and 4.5-5.1 million/mm³ (females)
  • Flat, bi-concave discs, lack a nucleus and mitochondrion; anaerobic respiration
  • Importance of their shape: increased surface area for gas exchange.
  • Function:
    • Transporting oxygen from lungs to tissues
    • Contain carbonic anhydrase to catalyze CO2 hydration.
    • Hemoglobin: excellent buffer for maintaining blood pH
  • Life span: 70-150 days
    • Macrophages in liver and spleen break them down.
    • Heme is broken down into iron (recycled) for rbc production, and bilirubin (excreted in bile/urine)
• Leukocytes (white blood cells):
  • Primarily involved in the immune response.
  • Number: 4000-11,000 per mm³
  • Types:
    • Granulocytes: neutrophils, eosinophils, basophils
    • Agranulocytes: monocytes, lymphocytes (B cells, T cells)
  • Lifespan: 13-20 days
• Thrombocytes (Platelets):
  • Cellular fragments, lack a nucleus
  • Essential for hemostasis (stopping bleeding)
  • Critical for vessel integrity by forming a plug and activating coagulation factors
  • Life span: 7-14 days
  • Number: 150,000-350,000 per mm³

Blood Cell Production

• Erythrocytes (red blood cells):
  • Produced in bone marrow throughout life
• Leukocytes (white blood cells):
  • Mostly in bone marrow
  • Some formed in lymph tissue
• Thrombocytes (platelets):
  • Developed in bone marrow

Hematocrit

• Percentage of blood volume occupied by red blood cells.
• Normal range: Men (42–52%), Women (37–47%).

Anemia

• Lower than normal oxygen-carrying capacity.
  • Nutritional Anemia: dietary deficiencies.
  • Pernicious Anemia: inability to absorb vitamin B12.
  • Aplastic Anemia: bone marrow failure.

Polycythemia

• Excess of circulating red blood cells.
• Primary vs Secondary (possible causes include high altitudes).

Clinical Applications

• Blood flow: essential for normal tissue function.
  • Reduced blood flow leads to decreased oxygenation -> ischemia -> necrosis.
• Mucous membranes: color indicates oxygenation status.
  • Pink (well-oxygenated), Blue (poorly oxygenated).
• Capillary refill time (CRT): assesses perfusion (blood flow).
  • Normal CRT is less than 2 seconds.