Page 241 - Biology_F5

Biology for Advanced Level Secondary Schools

Olfactory bulb

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Bone
Olfactory nerve
fibre
Olfactory
cell
Olfactory hair
(receptors)
Mucus layer

Figure 4.24: Structure of the olfactory lobe

Taste buds are located on the upper surface of the tongue. Each bud contains about
25 sensory receptor cells with tiny taste hairs exposed to drink and food dissolved in
saliva (Figure 4.25). Such buds sense the five basic tastes: bitter, sour, salty, sweet, and
umami (a savoury, meaty taste). A combination of odours and the basic tastes produce
subtler tastes.

Basal cells Taste
cells
Taste pore
Vallate
Foliate papillae
papillae

Gustatory
afferent
axons Synapse Microvilli
(c)
Papilla

Fungiform
papillae Tongue
(a) (b) Taste buds

Figure 4.25: Structure of the taste receptors

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