Respiratory System

Question 1

Describe the functions and highlight any differences between the conducting and respiring zones of the mammalian body:

Answer 1

• Can be divided into roughly two zones:
o Conducting zone encompasses all the respiratory passages: rigid tubes providing passages for air & function to cleanse, warm and humidify incoming air
 Consists of the nasal cavity, pharynx, trachea, bronchi and bronchioles
o Respiratory zone- refers to the actual site of gas exchange
 The respiratory bronchioles, alveolar ducts and the alveoli
 Within this zone, the alveolar epithelium encompasses cells for gas exchange and the secretion of surfactant to reduce surface tension

Question 2

Highlight differences in ventilation between and gas exchange between water and air breathing mammals:

Answer 2

• Birds have a relatively small, simple lungs together in a series of interconnected air sacs, rather than inspiration and exhalation with mammals the circuit means oxygen rich air is always in contact with respiratory surfaces.
• Amphibians lack mobile ribs and a diaphragm, thus pump air into the lungs under positive pressure. Additionally, amphibians have cutaneous gas exchange, whereby oxygen and carbon dioxide can pass across their most skin.
• Fish, extract oxygen from water by gills which are richly supplied with blood vessels to act as a respiratory organ.
• Extracting oxygen from water is energetically much more expensive than extracting oxygen from the air, and water contains much less oxygen per unit volume than air
• Fish gills are structured in such a way as to provide a very large surface area for gaseous exchange and a very short diffusion distance, thus increasing efficiency of gas exchange