The figure below illustrates a simple model of the human respiratory system. Study it carefully and answer the questions that follow.

Here are the answers to the questions:

a)

*i) Glass tube: Trachea

*ii) Part labelled X: Bronchus

*iii) Inflated balloon: Lung

*iv) Bell jar: Rib cage

*v) Rubber sheet: Diaphragm

b)

*i) The space: increases the volume in the bell jar.

*ii) The pressure: the pressure in the bell jar decreases.

c)

*i) Ribs

*ii) Sternum

*iii) Thoracic vertebrae

d)

Gases	Inhalation (%)	Exhalation (%)
Nitrogen	78	78
Oxygen	21	16
Carbon dioxide	0.04	4
Water vapour	Variable	6 (saturated)

e)

*i) Glucose

*ii) Amino acid

*iii) Fatty acid/Glycerol

f)

Excretory Organ	Metabolic waste products
The kidney	Urea, excess water, salts
The liver	Bile pigments
The lung	Carbon dioxide, water vapour
The skin	Salt, urea, water (as sweat)