Surface tension

Examples of Surface tension in the following topics:

• Factors Affecting Pulmonary Ventilation: Surface Tension of Alveolar Fluid

  • The surface tension of alveolar fluid is regulated by pulmonary surfactant, allowing efficient respiration.
  • Surface tension is the force exerted by water molecules on the surface of the lung tissue as those water molecules pull together.
  • As the air inside the lungs is moist, there is considerable surface tension within the tissue of the lungs.
  • The force of surface tension in the lungs is so great that without something to reduce the surface tension, the airways would collapse after exhalation, making re-inflation during inhalation much more difficult and less effective.
  • The net result is that the surface tension of the lungs from water is reduced so that the lungs can still inflate and deflate properly without the possibility of collapse from surface tension alone.

• Factors Affecting Pulmonary Ventilation: Compliance of the Lungs

  • Compliance depends on the elasticity and surface tension of the lungs.
  • The lungs must also be able to overcome the force of surface tension from water on lung tissue during inflation in order to be compliant, and greater surface tension causes lower lung compliance.
  • Therefore, surfactant secreted by type II epithelial cells increases lung compliance by reducing the force of surface tension.

• Development of the Respiratory System

  • This surfactant is important in reducing the surface tension at the air-alveolar surface, allowing expansion of the terminal saccules.
  • The lungs of pre-term infants therefore may not function well because the lack of surfactant leads to increased surface tension within the alveoli leading to alveoli collapse and no gas exchange, a condition known as respiratory distress syndrome.

• Alveoli

  • The alveolar membrane is the gas-exchange surface.
  • There are approximately 700 million alveoli in the lungs, which cover a total surface area of about 70 m2, which is a considerably larger surface area relative to volume.
  • The high surface area makes gas exchange with the bloodstream more efficient.
  • It is a lipoprotein with hydrophilic and hydrophobic ends that reduces the amount of surface tension from water in the lungs.
  • Without surfactant, the surface tension in the would cause the lungs to collapse during exhalation, making normal breathing impossible.

• Functional Anatomy of the Respiratory System

  • The reason for the elastic recoil of the lung is the surface tension from water molecules on the epithelium of the lungs.
  • A molecule called surfactant (secreted by the alveoli) prevents the surface tension from becoming too great and collapsing the lungs.

• Stability and Range of Motion at Synovial Joints

  • These include the shape of articular surfaces (how close they fit); strength and tension of capsule and ligaments (dependent on position); arrangement and tension of muscles; contact with soft parts such as adipose tissue; hormones; disuse causing decrease in synovial fluid, flexibility of ligaments and tendons, and muscle atrophy; gravity; and atmospheric pressure.

• Sciatic Nerve Injury

  • Pseudosciatic pain can also be caused by compression of peripheral sections of the nerve, usually from soft tissue tension in the piriformis or related muscles.
  • Left gluteal region, showing surface markings for arteries and the sciatic nerve

• How Skeletal Muscles Are Named

  • Convergent muscles have a common point of attachment, from which the muscle fascicles extend outward, not necessarily in a specific spatial pattern, allowing the muscle to cover a broad surface.
  • Covering a broad surface these fibers allow for more versatile types of movement.
  • Despite this they generate greater tension because they possess a greater amount of muscle fibers than similarly sized parallel muscles.
  • However, these muscles tend to have relatively more muscle fibers than similarly sized parallel muscles, and thus carry more tension.

• Bursae and Tendon Sheaths

  • The synovial lining in the bursae and tendon sheaths is similar to that within joints, with a slippery non-adherent surface allowing movement between planes of tissue.
  • A tendon (or sinew) is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension.

• Tactile Sensation

  • It is believed to be useful for monitoring slippage of objects along the surface of the skin, allowing modulation of grip on an object.
  • The vibrational role may be used to detect surface texture, e.g., rough versus smooth.