7.2 Digestive system
- Syllabus
- 0610–2026–2027
- Topic
- 7.2
- Level
- —
Learning objectives
7.2.1Main organs of the digestive system• Identify in diagrams and images the main organs of the digestive system, limited to: (a) alimentary canal: mouth, oesophagus, stomach, small intestine (duodenum and ileum) and large intestine (colon, rectum, anus) (b) associated organs: salivary glands, pancreas, liver and gall bladder7.2.2Functions of the organs• Describe the functions of the organs of the digestive system listed in 7.2.1, in relation to: (a) ingestion – the taking of substances, e.g. food and drink, into the body (b) digestion – the breakdown of food (c) absorption – the movement of nutrients from the intestines into the blood (d) assimilation – uptake and use of nutrients by cells (e) egestion – the removal of undigested food from the body as faeces
Identify the organs of the digestive system
The digestive system consists of the alimentary canal—a continuous tube through which food passes—and associated organs that add substances or process absorbed nutrients.
Trace the alimentary canal in order: mouth → oesophagus → stomach → small intestine (duodenum, then ileum) → large intestine (colon, then rectum) → anus.
| Structure | How to identify it in a diagram |
|---|---|
| mouth | opening where the canal begins |
| oesophagus | narrow tube leading from the mouth to the stomach |
| stomach | muscular sac below the oesophagus |
| duodenum | first, short curved part of the small intestine leaving the stomach |
| ileum | long, coiled remainder of the small intestine |
| colon | wider large intestine that frames the coils of the small intestine |
| rectum | final straight storage region of the large intestine |
| anus | opening at the end of the alimentary canal |
| Associated organ | Diagram landmark |
|---|---|
| salivary glands | glands around the mouth |
| liver | large organ above and beside the stomach |
| gall bladder | small sac beneath the liver |
| pancreas | elongated gland below or behind the stomach, beside the duodenum |
The liver, gall bladder, pancreas and salivary glands are associated organs, not sections of the alimentary canal. The duodenum and ileum are both parts of the small intestine; the colon and rectum are parts of the large intestine.
Map digestive processes to organ functions
Follow food through the system and separate five processes by what moves, where it moves and what happens to it.
| Process | Precise meaning | Main site or outcome |
|---|---|---|
| ingestion | taking substances such as food and drink into the body | through the mouth |
| digestion | breakdown of food | begins in the mouth, continues in the stomach and small intestine |
| absorption | movement of nutrients from the intestines into the blood | mainly through the small-intestine wall; water is also absorbed in the colon |
| assimilation | uptake and use of absorbed nutrients by cells | body cells, including liver cells |
| egestion | removal of undigested food from the body as faeces | through the anus |
| Organ | Function in the digestive system |
|---|---|
| mouth and salivary glands | ingest food; saliva mixes with food and digestion begins |
| oesophagus | transports swallowed food to the stomach |
| stomach | stores and mixes food; digestion continues |
| duodenum | receives food from the stomach and digestive secretions; digestion continues |
| ileum | completes much digestion and is the main site of nutrient absorption |
| colon | absorbs water and forms faeces from undigested material |
| rectum and anus | rectum stores faeces; anus releases them during egestion |
| pancreas | releases digestive secretions into the duodenum |
| liver and gall bladder | liver makes bile and assimilates absorbed nutrients; gall bladder stores and releases bile |
A useful chain is: ingest food → digest it → absorb nutrients into blood → assimilate nutrients in cells → egest what remains undigested.
Absorption is movement into the blood; assimilation is uptake and use by cells. Egestion removes undigested food, whereas excretion removes metabolic waste. Detailed physical digestion, bile action and enzyme chemistry belong to later objectives.