Mechanical barriers, the skin epidermis

Part A: Protective Mechanisms of the Skin and Mucosae Beyond their physical barrier function, the skin and mucosal surfaces employ a variety of biochemical and mechanical defenses:

• Mucus:
  • Locations: Respiratory tract, gastrointestinal tract, and reproductive tract.
  • Importance: Traps microorganisms and foreign particles, preventing their entry into deeper tissues.
• Lysozyme:
  • Locations: Tears, saliva, and mucus secretions.
  • Importance: Enzyme that breaks down bacterial cell walls, aiding in their destruction.
• Keratin:
  • Locations: Skin and hair.
  • Importance: Tough, fibrous protein that provides a physical barrier, resistant to microbial invasion.
• Acid pH:
  • Locations: Skin and vagina.
  • Importance: Inhibits the growth of many microorganisms.
• Cilia:
  • Locations: Respiratory tract.
  • Importance: Hair-like projections that sweep mucus and trapped particles out of the airways.

Part B: Decompression Sickness Mary Ann's symptoms are consistent with decompression sickness, also known as "the bends." This condition occurs when dissolved nitrogen gas, which is more soluble in blood and tissues at higher pressures, forms bubbles as the pressure decreases too rapidly. These bubbles can obstruct blood flow to various organs, causing pain, neurological symptoms, and respiratory distress. During scuba diving, the increased pressure underwater causes more nitrogen to dissolve in the body's tissues. As Mary Ann ascended to the surface, the pressure decreased, and the dissolved nitrogen formed bubbles. The rapid change in cabin pressure during the flight exacerbated this process, leading to the development of decompression sickness. To prevent decompression sickness, divers should ascend slowly, allowing the excess nitrogen to be gradually released through the lungs. Additionally, flying shortly after diving should be avoided, as the reduced cabin pressure can increase the risk of bubble formation.  

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