Digestive System

Digestive System

Human alimentary canal:

• Mouth
• Salivary glands
• Liver
• Oesophagus
• Pancreas
• Large intestine
• Small intestine
• Stomach
• Gall bladder

Egestion

Remaining material:

• Indigestible substances such as cellulose from plant cell walls
• Cells from lining of gut
• Water
• Bacteria (living and dead)

Absorption

Absorption is the movement of digested food through the wall of the intestine into the blood or lymph.

Important features of villi:

• Tiny, finger-shaped structures that increase the surface area
• Wall just one cell thick for short diffusion distance
• Network of blood capilliaries to transport glucose and amino acids away from the small intestine in the blood
• Internal structure called a lacteal which transports fatty accids and glycerol away from the small intestine in the lymph

Ingestion

Food enters the digestive system by mouth. This is called ingestion.

Peristalsis is where food is moved through the digestive system.

There are two sets of muscles in the gut wall. They work together to produce wave-like contractions:

• Circular muscles which reduce the diameter of the gut when they contract.
• Longitudinal muscles which reduce the length of the gut when they contract.

Digestive enzymes.

Digestion is the breakdown of large insoluble food molecules into…