Biology – 7.2 Human nutrition – alimentary canal | e-Consult

Mouth: The mouth is the entry point for food into the alimentary canal. It's involved in mechanical digestion through chewing (mastication) and chemical digestion through the action of salivary amylase, which begins the breakdown of starch.

Oesophagus: The oesophagus is a muscular tube that connects the mouth to the stomach. It transports food via peristalsis, a series of rhythmic muscle contractions, to the stomach.

Stomach: The stomach is a J-shaped organ that stores food and mixes it with gastric juices (hydrochloric acid and pepsin). This initiates chemical digestion of proteins. The stomach also regulates the release of chyme (partially digested food) into the small intestine.

Small Intestine: The small intestine is the primary site of nutrient absorption. It's divided into the duodenum, jejunum, and ileum. Here, enzymes from the pancreas and bile from the liver/gallbladder further digest carbohydrates, proteins, and fats. Nutrients are absorbed into the bloodstream through the intestinal walls.

Large Intestine: The large intestine absorbs water and electrolytes from the undigested material, forming faeces. It also houses bacteria that produce some vitamins. The large intestine then stores the faeces until elimination.