3 3 4 Human Digestive System Macrostructure and

3. 3. 4 Human Digestive System Macrostructure and basic function of the alimentary canal and associated glands in the digestion and transport of nutrients

Parts of the Human Digestive System 8. 3 M long

Mouth Contains a muscular tongue and a set of teeth. Secretes a juice called saliva from the salivary glands. Saliva contains an enzyme called amylase. Chemical ( enzymes) and mechanical (teeth) digestion of food takes place in the mouth

Functions of the Oesophagus Muscular Tube – 25 cm long Connects back of the mouth (pharnyx) to stomach Moves food along by waves of muscular contractions known as peristalsis – helps break food into smaller pieces http: //www. westga. edu/~lkral/peristalsis/

Stomach Food is stored J shaped muscular bag Food is churned and mixed with acidic secretions (Gastric juice ) to form chyme. Chemical digestion takes place in the stomach Mechanical digestion takes place in the stomach peristalsis http: //www. bbc. co. uk/science/humanb ody/body/factfiles/skeletalsmoothandc ardiac/stomach_peristalsis. shtml

Small Intestine A tube 5 -6 M long Divided into duodenum, jejenum, ileum Secretes enzymes which help in digestion. Contains infoldings called villi which increase the surface area available for the absorption of food

Large Intestine (Colon) Colon is about 1 M long Functions in the absorption of water Contains symbiotic bacteria Materials remain for about 12 hours and then moves to the rectum.

Rectum Undigested waste known as faeces is stored in the rectum Faeces consists of bacteria, unabsorbed food, cells from the intestine wall, bile pigments and mucus Faeces is egested through the anus

Liver Largest gland in the body Functions in the assimilation of digested foods Produces bile Bile is stored in the gall bladder

Pancreas Produces pancreatic juice Contains digestive enzymes Produces the hormone insulin