Digestive System Part 1

Process which organisms obtain food and energy for growth repair and maintenance of the body

Process that breaks down complex food substances into simple, soluble molecules that are small enough to be absorbed into the body cells

Digestion takes place in the alimentary canal, a long muscular tract which extends from the mouth to anus. Soluble products are absorbed and the undigested residue is egested

Mechanical breakdown of food into smaller particles to provide a large surface area to volume ratio for faster rate of chemical digestion by digestive enzymes

Breakdown of large food molecules into small soluble molecules catalysed by digestive enzymes through hydrolysis reactions

Act of taking food into mouth is called ingestion Chewing breaks don food into pieces to increase surface area to volume ration for faster rate of chemical digestion by digestive enzymes Saliva produced by the salivary glands in the mouth would moisten and soften food It also contains the enzyme salivary amylase which digests starch into maltose The thoroughly chewed food is then rolled into a bolus after swallowing bolus enters the oesophagus Digestion of starch continues in the oesophagus Bolus moved along the oesophagus by peristalsis, a rhythmic, wave like muscular contractions of the wall towards the stomach. Peristalsis occurs throughout the alimentary canal

Stomach is elastic muscular bag with thick muscular walls In presence of food,gastric glands in stomach will secrete gastric juice which consist of mainly hydrochloride acid and enzyme pepsin Hydrochloride acid provides an acidic base for the action of enzymes in the stomach It also kills bacteria and converts inactive forms of enzyme into their active form Pepsin is a protease and digests proteins to polypeptides by hydrolysis Food is churned and mixed with gastric juice by the peristaltic contractions of the stomach wall for hours Partly digested food liquefied, forming chyme which passes into duodenum in small amounts

Consist of duodenum, jejunum and highly coiled ileum Lining of the walls of the small intestine contains glands which secrete digestive enzymes Small intestine secretes intestinal juice which contains digestive enzymes needed to complete other digestion of carbohydrates, proteins and fats. At the end of digestive process, all carbohydrates are digested into monosaccharides such as glucose, fructose and galactose Polypeptides are digested into amino acids Fats are digested into fatty acids and glycerol The liver, gall bladder and pancreas are not part of the alimentary canal but are associated with it Pancreas is a gland lying below stomach which produces several digestive enzymes Liver is the largest gland that produces bile. Bile is an alkaline greenish-yellow liquid containing bile salts and bile pigments. Bile is stored in the gall bladder Duodenum receive chyme from stomach and secretions from the gall bladder and pancreas l

products of digestion such as monosaccharides, amino acids, fatty acids, glycerol and water are absorbed throughout the small intestine especially the ileum these products must be transported across the epithelium into the blood stream