Physiology Ch. 16

• Ventilation
• Gas Exchange
• 02 Utilization

• The act of breathing
• The mechanical process that moves air into and out of the lungs

• occurs at two locations
• between air and capillaries in the lungs
• between systemic capillaries and tissues of the body

known as cellular respiration

• Polyhedral in shape and clustered like units of honeycomb
• 300 million air sacs
• Each alveolus is 1 cell layer thick

• Alveolar type I: Structural cells
• Alveolar type II: Secrete surfactant

• Respiratory Zone
• Conducting Zone

• Region of gas exchange between air and blood (alveoli & capillaries)
• Respiratory bronchioles and alveolar sacs
• Must contain alveoli

• Includes all of the anatomical structures through which air passes before reaching the respiratory zone
• Trachea---> Terminal Bronchioles (No gas exchange)

• Space between visceral and parietal pleurae
• Visceral pleura: covers the organ
• Parietal pleura: lines the cavity wall
• Contains only a film of fluid secreted by the membranes

Intra alveolar pressure (pressure in the alveoli)

• Pressure in the intrapleural space
• This pressure is negative, due to lack of air in the intrapleural space

Pressure difference across the wall of the lung (inside vs outside)

Atmospheric pressire is > intrapulmonary pressure (-3 mmHg) high to low

Intrapulmonary pressure(+3 mm Hg) is > atmospheric pressure

Changes in intrapulmonary pressure ocur as a result of changes in lung volume because of gas is inversely proportinal to its volume

• decreases
• Air goes in

• raises
• air goes out

differences; lung volume

• Compliance
• Elasticity
• Surface tension

Stretchability: Ease with which the lungs can expand

• Tendency to return to initial size after distension
• High content of elastin proteins
• Has recoil ability
• Elastic tension increases during inspiration and is reduced by recoil during expiration

• Force exerted by fluid in alveoli to resist distension
• Lungs secrete and absorb fluid, leaving a very thin film of fluid
• This film of fluid causes surface tension

• Directly proportional to surface tension
• ^ increase ST ^ increase pressure in alveoli
• Inversely proportional to radius of alveoli
• decrease radius ^increase pressure

• Plays a vitale role in newborns
• A phospholipid produced by alveolar type II cells
• Lowers surface tension
• As alveoli radius decreases, surfactant's abilty to lower surface tension

Contraction of diaphragm, increases thoracic volume vertically

raising ribs; increasing thoracic volume laterally

• Quiet expiration is a passive process
• Decrease in lung volume raises the pressure within alveoli above atmosphere and pushes air out