IGCSE Biology – 2e: Nutrition – Humans
Key Digestion Processes
Ingestion
o Eating – E.g., Putting food in your mouth and swallowing it.
Digestion
o Breaking down large, insoluble molecules into small, soluble molecules.
Absorption
o Diffusion or active transport of small, soluble products of digestion in the blood.
Assimilation
o The soluble products of digestion are incorporated into the body, making new
molecules in cells.
Egestion
o Removal or undigested food from the anus.
o This is NOT excretion.
The Structure of the Digestive System
The Mouth
o Where food enters the alimentary canal and digestion begins.
Salivary Glands
o Their function is the produce saliva containing amylase.
Oesophagus
o The oesophagus is a muscular tube which moves ingested tube to the stomach.
Key Digestion Processes
Ingestion
o Eating – E.g., Putting food in your mouth and swallowing it.
Digestion
o Breaking down large, insoluble molecules into small, soluble molecules.
Absorption
o Diffusion or active transport of small, soluble products of digestion in the blood.
Assimilation
o The soluble products of digestion are incorporated into the body, making new
molecules in cells.
Egestion
o Removal or undigested food from the anus.
o This is NOT excretion.
The Structure of the Digestive System
The Mouth
o Where food enters the alimentary canal and digestion begins.
Salivary Glands
o Their function is the produce saliva containing amylase.
Oesophagus
o The oesophagus is a muscular tube which moves ingested tube to the stomach.
