Physiology Ch. 2 Blood

Study Notes

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

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.

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).

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

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

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

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.