Page 302 - Biology_F5

Gas exchange and respiration

Connective tissue cell
Epithelial cell which produces surfactant

Macrophage Alveolar air space

Epithelial cell
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Alveolar barriers
White blood cell
Blood plasma Blood capillary

Red blood cells

Figure 6.3: Structure of the alveolus

Surface tension of the lungs Activity 6.1: Observation of the
The surface tension provided by surfactant structure of the mammalian lungs
stabilizes the alveoli during inflation
and dilation resulting from inhalation Materials
and exhalation of gases. The surfactant Mouse or rat, dissection kit, dissecting
is a phospholipid and a protein chemical tray, chloroform, and cotton wool
produced in early development stage
of foetus. This chemical helps to lower Procedure
the surface tension and promotes lungs’ (a) Use your dissection knowledge to
expansion during inspiration (inhalation), open up the body cavity of a mouse
preventing alveolar collapse. It is also in the usual way to display the
lungs.
believed to protect the lungs from (b) Use a hand lens to observe the
infections. thoracic and abdominal cavities as
well as the diaphragm.
The proteins and lipids that make up the
surfactant have both hydrophobic and Questions
hydrophilic regions that are important in 1. Draw a well labelled diagram of
lowering the surface tension by adsorbing your dissection.
the air–water surface interface, with 2. Explain the functions of each part of
hydrophobic head groups in water and the mammalian lungs.
hydrophobic tail facing towards the air.
Safety precautions
1. Laboratory rules and regulations
should be adhered to.
2. Rat or mouse may bite and also
their fur may cause allergy to a
human being.

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