The Human Digestive System (WJEC GCSE Biology)
Revision Note
The Human Digestive System
The human digestive system is made up of the organs that form the alimentary canal and accessory organs
The alimentary canal is the channel or passage through which food flows through the body, starting at the mouth and ending at the anus. Digestion occurs within the alimentary canal
Accessory organs produce substances that are needed for digestion to occur (such as enzymes and bile) but food does not pass directly through these organs
The structure of the human digestive system diagram
The human digestive system includes the organs that form the alimentary canal, and accessory organs that aid the process of digestion
The roles of the organs of the digestive system table
Structure | Function |
|---|---|
Mouth | The mouth is where mechanical digestion takes place Teeth chew food to break it into smaller pieces and increase its surface area to volume ratio Carbohydrase (amylase) enzymes in saliva start breaking down starch The food is shaped into a ball by the tongue and lubricated with saliva so it can be swallowed easily |
Stomach | Food is mechanically digested by churning actions while protease enzymes start to chemically digest proteins Hydrochloric acid is present to kill bacteria in food and provide the optimum pH for protease enzymes to work |
Pancreas | Produces all three types of digestive enzymes: carbohydrases, proteases and lipases Secretes enzymes into the small intestine for digestion |
Small intestine | Food coming out of the stomach finishes being digested by enzymes produced here and also secreted from the pancreas Absorption of digested food molecules takes place. The small intestine is long and lined with villi to increase the surface area over which absorption can take place |
Large intestine | Water is absorbed from the remaining waste material to produce faeces Faeces is stored in the rectum and removed through the anus |
Liver | Produces and secretes bile to emulsify fats |
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