8.10 Practical: Blood & Blood Vessels

Objective

• Identify and observe arteries, veins, and various blood cells using prepared microscope slides.
• Create plan diagrams illustrating the layers of blood vessel walls.
• Draw detailed representations of individual blood cells at high magnification.

Materials Needed

• Prepared microscope slides of arteries, veins, and blood cells.
• Microscope with appropriate magnification (preferably high power).
• Drawing paper and pencils.
• Reference materials: Electron micrographs and photomicrographs.
• Ruler and compass for accurate diagrams.

Procedure

1. Preparation and Observation

A. Blood Vessels

1. Identify Arteries and Veins:
   • Examine the prepared slides to distinguish between arteries and veins based on their structural differences.
2. Create Plan Diagrams:
   • Draw the Blood Vessel Walls:
     • Illustrate the three main layers:
       • Endothelium (Tunica Intima): Innermost layer, smooth to reduce friction.
       • Smooth Muscle (Tunica Media): Middle layer, responsible for vasoconstriction and vasodilation.
       • Outer Collagen Layer (Tunica Externa): Provides structural support.
   • Label Each Layer:
     • Clearly mark each layer to highlight their composition and function.

B. Blood Cells

1. Observe Different Blood Cells:
   • Use high-power magnification to view:
     • Red Blood Cells (Erythrocytes): Biconcave shape, no nucleus.
     • Monocytes: Larger cells with a single, kidney-shaped nucleus.
     • Neutrophils: Multi-lobed nucleus with granular cytoplasm.
     • Lymphocytes: Large, round nucleus with scant cytoplasm.
2. Differentiate Based on Features:
   • Note characteristics such as nucleus shape, presence of granules, and cell size to distinguish between cell types.

2. Drawing Techniques

A. Plan Diagrams

1. Reference Practical Activity 7.1:
   • Follow the guidelines provided in Practical Activity 7.1 for creating accurate and proportionate plan diagrams.
2. Focus Areas:
   • Ensure each layer of the blood vessel wall is clearly represented and proportionally accurate.
   • Use shading or color-coding to differentiate between layers if possible.

B. High-Power Cell Drawings

1. Reference Practical Activity 7.1:
   • Utilize instructions from Practical Activity 7.1 to guide your high-power drawings.
2. Accuracy and Detail:
   • Red Blood Cells: Draw their characteristic biconcave shape without a nucleus.
   • Neutrophils: Illustrate the lobed nucleus and granular cytoplasm.
   • Lymphocytes: Depict the large, round nucleus with minimal cytoplasm.
   • Monocytes: Show the kidney-shaped nucleus and larger cell size.
3. Label Key Features:
   • Mark important structures such as the nucleus, granules, and cell membrane.

3. Tips for Successful Observation and Drawing

• Use High-Power Magnification: Ensures clear visibility of detailed structures.
• Distinguish Cell Types:
  • Red Blood Cells: Lack nuclei, biconcave shape.
  • Neutrophils: Multi-lobed nuclei, granules visible.
  • Lymphocytes: Large nuclei, minimal cytoplasm.
  • Monocytes: Larger size, kidney-shaped nuclei.
• Maintain Proportion: Keep diagrams and drawings to scale for accuracy.
• Use Reference Images: Compare your drawings with electron micrographs and photomicrographs for precision.
• Practice Patience: Take time to observe each slide carefully before drawing to capture all necessary details.

Key Terms and Concepts

• Endothelium (Tunica Intima): Inner lining of blood vessels, composed of a single layer of endothelial cells.
• Smooth Muscle (Tunica Media): Middle layer containing smooth muscle fibers that control vessel diameter.
• Tunica Externa: Outer layer made of connective tissue, providing structural support.
• Red Blood Cells (Erythrocytes): Transport oxygen using haemoglobin; lack nuclei.
• Neutrophils: White blood cells with multi-lobed nuclei and granules; part of the immune response.
• Lymphocytes: White blood cells with large nuclei; involved in adaptive immunity.
• Monocytes: Large white blood cells with kidney-shaped nuclei; differentiate into macrophages.
• Plan Diagram: A schematic drawing representing the layers of a blood vessel.
• Dissociation Curve: Graph depicting haemoglobin’s oxygen saturation relative to oxygen partial pressure.
• Chloride Shift: Exchange of chloride ions and bicarbonate ions to maintain ionic balance during CO₂ transport.

Common Errors to Avoid

1. Oxyhaemoglobin Release:
   • Incorrect: Haemoglobin releases O₂ gradually as it moves from the lungs to muscles.
   • Correct: O₂ is primarily released in tissues with low partial pressure of O₂, not simply based on distance.
2. Function of Arteries:
   • Incorrect: Arteries pump blood around the body.
   • Correct: Arteries transport blood away from the heart; the heart is the pump.
3. Red Blood Cells Surface Area:
   • Incorrect: Red blood cells have a large surface area for oxygen attachment.
   • Correct: The biconcave shape increases surface area for diffusion but does not involve direct attachment.
4. CO₂ Transport:
   • Incorrect: Most CO₂ is transported dissolved in plasma.
   • Correct: Most CO₂ is transported as HCO₃⁻ ions; only a small portion is dissolved directly in plasma.

Study Tips

• Visual Learning: Use diagrams and drawings to reinforce the structure and function of blood vessels and cells.
• Labeling Practice: Regularly practice labeling different parts of blood vessels and blood cells to improve retention.
• Compare and Contrast: Understand the differences between arteries and veins, and between various blood cell types.
• Repetition: Repeated observation under the microscope will enhance your ability to identify and draw accurately.
• Use Mnemonics: Create memory aids for the layers of blood vessel walls and the characteristics of different blood cells.