Topic Summaries

• The digestive system is an organ system.

• Digestion is the breakdown of large, insoluble food into small, soluble molecules, which are absorbed into the bloodstream.

• The products of digestion are used to build new carbohydrates, lipids and proteins. Some glucose is used in respiration.

Structures of the digestive system:

• Mouth: ingests food; teeth break food into smaller pieces to increase surface area for digestive enzyme action.

• Salivary glands: produce slightly alkaline saliva containing enzymes that break down starch.

• Oesophagus: peristalsis (contraction and relaxation of circular and longitudinal muscles) moves food into the stomach.

• Stomach: churns food with hydrochloric acid, killing microorganisms. Stomach acids break down proteins.

• Small intestine: contains enzymes to break down food and villi to absorb products of digestion (e.g. glucose and amino acids absorbed into the capillaries/bloodstream, fatty acids and glycerol absorbed into the lymph (lacteal)).

• Large intestine: absorbs remaining water, forming faeces.

• Rectum and anus: stores and egests faeces.

• Liver: produces bile.

• Gall bladder: stores bile.

• Pancreas: produces digestive enzymes.