Recognise arteries, veins and capillaries from microscope slides, photomicrographs and electron micrographs and make plan diagrams showing the structure of arteries and veins in transverse section (TS) and longitudinal section (LS)

SouravOctober 29, 2024

Answered step-by-step

When examining the structure of arteries, veins, and capillaries under the microscope or through photomicrographs, you can recognize their distinctive features. Here’s how to identify them, along with a description of how to create plan diagrams for arteries and veins in both transverse and longitudinal sections.

Identifying Arteries, Veins, and Capillaries

1. Arteries:
   • Appearance: Thick, muscular walls that are elastic and have a narrow lumen (the inner space of the vessel).
   • Layers: Composed of three layers:
     • Tunica intima: The inner endothelial layer.
     • Tunica media: A thick middle layer made up of smooth muscle and elastic fibers.
     • Tunica externa: The outer layer made of connective tissue.
   • Function: Carry oxygenated blood away from the heart (except for the pulmonary artery).
2. Veins:
   • Appearance: Thinner walls compared to arteries, with a wider lumen and less muscle and elastic tissue.
   • Layers: Similar to arteries, but the tunica media is much thinner.
   • Valves: Veins often contain valves to prevent backflow of blood.
   • Function: Carry deoxygenated blood back to the heart (except for the pulmonary vein).
3. Capillaries:
   • Appearance: Microscopic vessels with walls that are only one cell thick, allowing for efficient gas and nutrient exchange.
   • Structure: Composed only of endothelial cells, no smooth muscle or connective tissue.
   • Function: Facilitate the exchange of oxygen, carbon dioxide, nutrients, and waste products between blood and tissues.

Plan Diagrams of Arteries and Veins

1. Transverse Section (TS) Diagrams

• Artery TS Diagram:
  • Label:
    • Tunica intima (inner layer)
    • Tunica media (thick middle layer)
    • Tunica externa (outer layer)
    • Narrow lumen
  • Visual Representation: Show the three layers with the thick tunica media.
• Vein TS Diagram:
  • Label:
    • Tunica intima (inner layer)
    • Tunica media (thinner middle layer)
    • Tunica externa (outer layer)
    • Wide lumen
    • Valves (if visible)
  • Visual Representation: Illustrate the thinner walls and wider lumen, including valves.

2. Longitudinal Section (LS) Diagrams

• Artery LS Diagram:
  • Label:
    • Lumen
    • Tunica intima
    • Tunica media (showing layers of smooth muscle)
    • Tunica externa
  • Visual Representation: Show the elongated structure of the artery, emphasizing the thick tunica media.
• Vein LS Diagram:
  • Label:
    • Lumen
    • Tunica intima
    • Tunica media
    • Tunica externa
    • Valves (illustrating their position)
  • Visual Representation: Highlight the thinner walls and wider lumen, showing the valves’ position.

Summary of Diagram Features

• Thickness of Walls: Arteries have thick walls, while veins have thinner walls.
• Lumen Size: Arteries have a narrow lumen, while veins have a wider lumen.
• Valves: Present in veins but absent in arteries.
• Layering: Both have three layers, but the composition varies significantly, particularly in the tunica media.