Overview
Blood is a fluid connective tissue comprising cells scattered in a liquid matrix, making up approximately 8% of body weight with an average volume of 5 liters. It circulates continuously, delivering gases, nutrients, and performing regulatory functions throughout the body.
Blood as Connective Tissue
- Classified as connective tissue with cells distributed in a matrix
- Matrix is fluid (plasma) rather than solid
- Contains formed elements (cells) suspended in the liquid portion
- Continuously circulates throughout the body
Blood Composition
When blood is centrifuged (hematocrit test), it separates into distinct layers:
| Component | Percentage | Contents |
|---|
| Plasma | ~55% | Fluid matrix containing solutes, proteins, ions, dissolved gases |
| Buffy Coat | ~1% | White blood cells and platelets |
| Red Blood Cells | 40-45% | Erythrocytes (red portion) |
- Hematocrit test will be performed in lab this week
- Plasma percentage can change based on water content
- Red blood cells occupy the largest cellular portion
Plasma Components
- Solutes include ions, dissolved gases, glucose, and amino acids
- Proteins: albumin, globulins, transport proteins, clotting proteins
- Hormones circulate dissolved or bound to proteins
- Immunoglobulins (antibodies) provide immune function
- Most solute transport occurs within plasma
Functions of Blood
- Gas exchange: Gases dissolve in plasma and bind to red blood cells
- Solute transport: Nutrients, hormones, and waste products move through plasma
- Immune functions: White blood cells and antibodies (immunoglobulins) defend against pathogens
- Temperature regulation: Blood is warmer than surrounding tissues and distributes heat
- Adjusting blood flow to regions helps maintain body temperature
- Hemostasis: Clotting mechanisms prevent blood loss
- Acid-base balance: Maintains pH within 7.35 to 7.45 range
- CO2, bicarbonate, and hemoglobin participate in buffering systems
- Blood pressure: Volume and composition affect pressure for effective delivery
Key Terms & Definitions
- Hematocrit: Test that measures percentage of red blood cells by centrifuging blood
- Buffy coat: Thin layer containing white blood cells and platelets between plasma and red blood cells
- Formed elements: Cellular components of blood (red cells, white cells, platelets)
- Plasma: Liquid matrix portion of blood (approximately 55% of volume)
- Hemostasis: Process of blood clotting to stop bleeding
Action Items / Next Steps
- Review hematocrit test procedure before lab session this week
- Memorize normal blood pH range: 7.35 to 7.45
- Prepare for next lecture focusing on plasma functions and components