Page 135 - Biology Form Two

Biology for Secondary Schools

Gas exchange is process that enables mammals to obtain oxygen gas in their
body for respiration. Gas exchange is possible through the respiratory system.
The components of the respiratory system of mammals include the nostril, nasal
cavity, pharynx, trachea, bronchi, lungs, bronchioles, alveoli, intercostal muscles,
diaphragm and ribs, as shown in Figure 6.1.
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Nasal cavity

Nose Pharynx
Nostril Epiglottis
Larynx
Bronchus Trachea

Rib

Lung

Bronchiole
Diaphragm
Alveoli

Figure 6.1: Human respiratory system
Each component of the mammalian respiratory system performs a particular
function and has various adaptive features that enable its functions, as shown in
Table 6.2.

Table 6.2: Adaptations and functions of parts of the mammalian respiratory
system

Part Adaptive features Functions
Nose and nasal Mucus lining and hairs (cilia) Traps dust and micro-
cavity organisms

Glottis Presence of epiglottis Closes the trachea during
swallowing to prevent food
from entering the respiratory
system

Trachea, bronchus Blood vessels near the surface Warm the air
and bronchioles
Have rings of cartilage tissue Prevent collapse of the
along their length respiratory tract

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