1. Distinguish between ventilation, gas exchange, & cell respiration.

ventilation = breathing, or the bulk movement of air into and out of the lungs, by:

• inhalation, which occurs when muscular contractions increase the volume of the lungs thus decreasing the pressure so air enters the lungs,
• exhalation, when muscular relaxation decreases the volume of the lungs thus increasing pressure so gases exit the lungs
• gas exchange = the process whereby O2 is acquired and CO2 is removed between respiring cells and the environment; the gas exchange surface = alveoli
• cell respiration = breakdown of glucose and other molecules in the mitochondria of cells creating a constant demand for O2 and a need to eliminate CO2

Click to view an animation showing gas exchange: http://www.airinfonow.org/html/lungattack/lungplay.htm

2. Explain: the need for a ventilation system.

• adequate lung ventilation is essential to gas exchange which is turn essential to cell respiration and the energy needs of cells, tissues, organs and organisms
• ventilation provides a continual supply of fresh air to the lungs and helps to maintain a large diffusion gradient for respiratory gases across the gas exchange surface of the alveoli
• O2 must be delivered regularly to supply the needs of respiring cells
• CO2 must be quickly eliminated from the body to reduce its toxic effects

3. Describe the features of alveoli that adapt them for gas exchange.

alveoli = the millions of thin-walled, dead-ends of the bronchioles forming clusters of air sacs acting as the respiratory surface with features of:

• large surface area: surface area of the alveolar epithelium - 100 m2
• thin: single cell layer of epithelium across which diffusion occurs
• moist: gasses need to dissolve before passing membranes
• rich blood supply: extensive net of capillaries for transport of gasses to and from alveoli

Click to view an animation showing gas exchange: http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter44/animations.html#

4. Draw and label a diagram: trachea, bronchi, bronchioles, lungs

Click to view an animation showing lung anatomy: http://sprojects.mmi.mcgill.ca/resp/anatomy.swf

5. Explain the mechanism of ventilation of the lungs in terms of volume and pressure changes caused by the internal and external intercostal muscles, the diaphragm and the abdominal muscles.

6.5: Lecture Notes