Digestive System
ICSE · Class 9 · Biology
Quick revision notes for Digestive System — ICSE Class 9 Biology. Key concepts, formulas, and definitions for last-minute revision.
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1. Digestive System and Alimentary Canal
- The digestive system has two main parts: the alimentary canal and digestive glands.
- The alimentary canal is a muscular tube about 9 metres long.
- It starts at the mouth and ends at the anus.
2. Teeth and Dentition
- An adult human normally has 32 teeth.
- Teeth help in biting, tearing, grinding, crushing, and speaking.
- Human or mammalian teeth are heterodont, which means they are different in shape.
3. Saliva and Salivary Glands
- Three pairs of salivary glands secrete saliva into the mouth: parotid, submandibular, and sublingual glands.
- A person normally produces 1000 to 1500 ml of saliva daily.
- Saliva has a pH of 6.8.
4. Swallowing, Peristalsis, and Oesophagus
- Swallowing moves food from the mouth into the pharynx and then into the oesophagus.
- Peristalsis is the wave of constrictions caused by the circular muscles of the gut pushing the food along.
- Peristalsis occurs through all regions of the gut.
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