Chapter 7 Self-check questions and answers

Q1. Why do we have two waves of tooth eruption?

A. Only smaller teeth will fit into the small jaws of young children. As the jaw expands with growth, more deciduous teeth erupt. Teeth develop from tooth buds deep in the jaw and the enamel is laid down by ameloblasts outside the developing tooth. Once the tooth has erupted, no further enamel can be added and therefore the tooth cannot be enlarged. Thus, the small deciduous teeth are shed and replaced with the larger permanent dentition as the jaw approaches its final size at the end of puberty.

Q2. Explain why few people can eat more than 5–8 dry cheese biscuits (or crackers) without drinking.

A. The rate of absorption of saliva exceeds production. Saliva is essential to create a lubricated food bolus that can be swallowed

Q3. The five main sensations do not explain the great variety of taste and flavours we experience. Why is that?

A. The more subtle sensations of flavour are related to smell. As a practical example, attempt to identify different foods by taste when holding your nose and blindfolded.

Q4. Explain the functional basis of the physiological risk of prolonged diarrhoea.

A. As faeces passes very quickly through the large intestine, there is insufficient time for water absorption to take place. Furthermore, the mucosal lining may also be damaged by inflammation in severe cases, further limiting the amount of water absorption that can take place. Thus, the risk to the individual is of life-threatening dehydration, a situation made so terribly clear in outbreaks of cholera following the breakdown of good sanitation.

Q5. One noted feature of the gut mucosa is its high rate of cellular turnover. Why is this important for the proper functioning of the gut?

A. The “inside” external environment of the gut is a harsh one and the attrition of cells through damage might be expected to be high. The constant renewal of cells from the transit amplifying compartments ensures that the integrity of the mucosa is maintained and that any major damage is repaired quickly.