The digestive system

The digestive system is concerned with the intake, breakdown and absorption of food substances. Carbohydrates, fats (lipids) and proteins are broken down into small molecules that can pass through the walls of the digestive tract into the bloodstream and then into body cells. Here they are used for energy, growth and repair of tissues.

Mouth Tongue

Submandibular salivary gland

Diaphragm

Liver Gall bladder Bile duct

Pancreas Ascending colon

Appendix

Figure 2.17 The digestive system.

Mouth Tongue

Submandibular salivary gland

Diaphragm

Liver Gall bladder Bile duct

Pancreas Ascending colon

Duodenum

Jejunum

Ileum

Descending colon Rectum

Anal canal

Anus

Parotid salivary gland

Sublingual salivary gland Pharynx Epiglottis

Oesophagus

Cardiac sphincter

Stomach Pyloric sphincter

Duodenum

Jejunum

Ileum

Small intestine

Descending colon Rectum

Anal canal

Anus

The digestive system is divisible into two main parts:

^^ Gastro-intestinal tract or alimentary canal: this is a tube approximately 7 m in length. It starts at the mouth and ends at the anus. The parts of the gastro-intestinal tract are: ® mouth ® pharynx ® oesophagus ® stomach

® small intestine, divided into duodenum, jejunum and ileum ® large intestine, divided into caecum, colon, rectum and anal canal.

^^ Accessory structures and organs connect with the tract and play an important role in the digestive process. They are: ® teeth ® tongue ® salivary glands ® gall bladder ® pancreas ® liver.

Substances move along the tract by a series of muscle contractions known as peristalsis.

Massage stimulates peristalsis and also aids the movement through the tract.

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