Digestive System Part 1 Flashcards
What is nutrition
Process which organisms obtain food and energy for growth repair and maintenance of the body
What is digestion
Process that breaks down complex food substances into simple, soluble molecules that are small enough to be absorbed into the body cells
Where does digestion take place
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
Physical digestion
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
Chemical digestion
Breakdown of large food molecules into small soluble molecules catalysed by digestive enzymes through hydrolysis reactions
Digestion in the mouth
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
Digestion in stomach
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
Small intestine
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
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absorption in the small intestine
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
