ADAPTATIONS OF THE RESPIRATORY SYSTEM TO GASEOUS EXCHANGE (20 mks)

                     Adaptations of the Respiratory System to Gaseous Exchange

• The nostrils & inner passages of air are lined with ciliated epithelial cells; the cilia movements cause a sweeping action of mucus containing dust & pathogens; towards the pharynx for swallowing hence preventing their entry into the air ways;
• The nostrils & inner air passages have goblet cells which secrete mucus to trap dust particles, therefore cleaning the air;
• The lining of nostrils and air passages has a rich supply of blood, which keeps the incoming air warm and moist for faster diffusion in the lungs;
• The epiglottis  on top of the trachea prevent food, drinks and other solid particles from going in the trachea during swallowing;
• Lungs provide numerous alveoli; to provide a large surface area; for efficient gaseous exchange;
• Alveoli wall and blood capillary wall are made of squamous epithelium cells which are thin; to provide a shorter diffusion distance; for faster gaseous exchange
• The lung is spongy; and has numerous alveoli; that accommodates large volume of gases (oxygen);
•  The lungs are highly vascularised to enhance transport of oxygen and carbon  (IV) oxide to and from the body tissues respectively;
• High vascularization increases the oxygen and carbon (IV) oxide concentration gradient between the blood and alveoli air space,
• The alveoli inner surfaces are covered by a thin layer of moisture/water films; to dissolve oxygen; for faster diffusion into the blood solution;
• The lung is connected to tree-like system of tubes; (the trachea, bronchi/bronchioles); that supply oxygen and removes carbon  (IV) oxide from the lungs;
• The whole lung is covered with the pleural membrane; which secretes a lubricant to lubricate and allow free movement of the lungs.