lecture_notes_29_(ta)_2

lecture_notes_29_(ta)_2 - Lecture 29: Respiratory...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Lecture 29: Respiratory Physiology II Reading: ch 13, section: intro, mechanics, pgs 464-472; 475-484 (pgs 473-480; 483-492, if using 5 rd edition) ( QUESTIONS : WHAT STRUCTURES ARE COMMON TO BOTH THE RESPIRATORY AND DIGESTIVE SYSTEMS ) ( WHEN AVEOLAR PRESSURE IS GREATER THAT ATMOSPHERIC PRESSURE , WHERE DOES AIR GO ? ) Elastic recoil - this is the ( PASSIVE ) force that restores the lungs to their preinspiratory volume after the inspiratory muscles relax at the end of inspiration. It is similar to the force that restores the shape of a balloon when the air within it is released. It is determined by two factors: ( 1 ) elastic properties of pulmonary tissue - pulmonary tissue contains large quantities of elastin fibers. They are arranged in a meshwork that provides the tissue with a high degree of elasticity. ( RESPONSIBLE IN PART FOR DECREASED INTERPLURAL SAC PRESSURE. W HAT’S THE OTHER FACTOR RESPONSIBLE (BESIDES FLUID COHESION) ? ) ( 2 ) alveolar surface tension - this is the force exerted at the interface between a liquid and a gas that tends to minimize the surface area at the interface. It results from the preferential attraction of water molecules for each other. In the alveoli, surface tension acts to resist any increases in alveolar surface area and thereby oppose alveolar expansion during inspiration. Similarly, surface tension acts to minimize alveolar surface area and thereby reduce the size of the alveoli. This force is so strong that it must be counteracted in order to prevent alveolar collapse. This is achieved by the production of a pulmonary surfactant ( THIS EQUALIZES SURFACE TENSION ACROSS ALL ALVEOLI ) that is synthesized by the type II cells and released into the alveoli (Figure 13-16 . ( PREMATURE BABIES DON T HAVE ENOUGH TIPE II CELLS AND THUS ARE IN DANGER OF HAVING THEIR LUNGS COLLAPSE ) Law of LaPlace - Magnitude of inward-directed pressure (P) in a bubble = 2 x surface tension (T)
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 4

lecture_notes_29_(ta)_2 - Lecture 29: Respiratory...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online