A young child has 20 ‘milk’ teeth. A full adult set is made up of 32 teeth. Teeth are arranged in order in the semicircle of each jaw. The teeth in the upper and lower jaws are almost mirror images of one another. The dental formula is a way of describing the sequence and number of different types of teeth in one half of the upper and lower jaw on the same side, from middle front to back. Incisors are noted first, canines second, premolars third and then molars. A full adult set has the following formula:
2.1.2.3 2.1.2.3
That is, two incisors, one canine, two premolars, and three molars on one side of the upper and lower jaw.
2. Oesophagus zz
3. Stomach z z
Learn more about stomach acid in Chemical World 13.3
z z z z
Food is moved through the oesophagus by the wavelike movement of muscles. This continues the physical digestion of food.
The stomach is an expandable muscular bag that physically churns and temporarily stores food.
The stomach releases juices that continue the chemical digestion of food.
Hydrochloric acid in the stomach chemically digests food and kills bacteria.
4. Small intestine zz
z z zz
Food from the stomach enters the small intestine. More enzymes complete the breakdown of food.
The small intestine is densely covered in villi. The villi provide an increased surface area to allow food to be absorbed into the bloodstream.
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Fig. 8.2.4
Villi increase the surface area of the small intestine
