Human Nutrition and Digestion: Question 5
Syllabus 7.3
A dentist is explaining to a young patient how different teeth are suited to eating different foods. She describes four teeth found in the patient's mouth without naming them.
Tooth W has a broad, flat biting surface with four rounded bumps, and is one of the two largest teeth found right at the back of the jaw.
Tooth X has a single sharp point and is used for gripping and tearing tougher food, such as meat.
Tooth Y has a thin, flat, chisel-shaped edge and is found at the very front of the jaw, used for cutting food into smaller pieces.
Tooth Z has two rounded bumps on its biting surface and sits between the pointed tooth and the teeth at the very back of the jaw.
(a) Name each tooth, W, X, Y and Z. [4]
(b) Describe how the enamel, dentine and pulp of a tooth are arranged, and state one function of each. [3]
(c) The dentist also explains that the stomach continues to physically break down food after it has been swallowed. Describe how the stomach carries out physical digestion of food. [2]
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Worked solution
Part (a): Naming the teeth
Tooth W, molar
A broad, flat biting surface with several rounded bumps (cusps), found as one of the largest teeth right at the back of the jaw, describes a molar. Molars are used for crushing and grinding food.
Tooth X, canine
A single sharp point used for gripping and tearing tougher food, such as meat, describes a canine.
Tooth Y, incisor
A thin, flat, chisel-shaped edge at the very front of the jaw, used for cutting food into smaller pieces, describes an incisor.
Tooth Z, premolar
Two rounded bumps on the biting surface, positioned between the canine and the molars, describes a premolar. Premolars help crush and chew food, alongside the molars.
Part (b): Structure of a tooth
A tooth is made up of three layers, arranged from the outside in:
- Enamel forms the hard outer covering of the crown of the tooth. Its function is to protect the tooth from wear and damage as it bites and chews hard or fibrous food.
- Dentine lies beneath the enamel and forms the bulk of the tooth. Its function is to support the enamel and cushion the tooth against the force of biting.
- Pulp is the innermost region of the tooth, containing nerves and blood vessels. Its function is to supply the tooth with nutrients and to allow the tooth to detect stimuli such as pain, pressure and temperature.
Part (c): Physical digestion in the stomach
The stomach has thick, muscular walls that contract and relax in a churning action. This physically breaks the swallowed food into smaller pieces and thoroughly mixes it with gastric juice, forming a semi-liquid mixture. Breaking the food into smaller pieces in this way increases its surface area, which will later help enzymes in chemical digestion act more quickly.
Final answers
- (a) W: molar; X: canine; Y: incisor; Z: premolar.
- (b) Enamel (hard outer protective covering), dentine (supports and cushions the tooth) and pulp (contains nerves and blood vessels, innermost layer).
- (c) The stomach’s muscular walls churn the food, breaking it into smaller pieces and mixing it with gastric juice.