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18 Cards in this Set
- Front
- Back
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define nutrition |
nutrition is the process by which organisms obtain food and energy for growth, repair and maintenance of the body |
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what does the human digestive system consist of? |
the alimentary canal and the organs associated with it (liver and pancreas) |
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digestion in the buccal cavity |
physical: chewing breaks up good into smaller pieces, hence increasing surface area to volume ratio of food to saliva chemical: salivary amylase in saliva breaks down some starch into maltose tongue mixes food with saliva |
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pharynx and larynx order |
pharynx then larynx |
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what does pharynx lead to |
leads to both trachea + larynx and oesophagus. during swallowing, the larynx moves upwards and epiglottis moves downwards, so that the larynx is covered by the epiglottis and no food particles can enter the trachea |
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antagonistic movement in the oesophagus |
-longitudinal muscles outer layer -circular muscles inner layer when the LM contract and CM relax, the gut dilates, becoming wider and shorter. this widens the lumen to allow food to entee when the CM contracts and LM relax, the gut constricts, becoming narrower and longer, squeezing and pushing the food forward |
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what: stomach |
is a distensible muscular bag with thick and well-developed muscular walls.
when the stomach is fully distended, it sends signals to the brain that it is full or sated.
the stomach has numerous pits which lead to gastric glands. the gastric glands secrete gastric juice into the stomach cavity |
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digestion in the stomach |
chemical: hydrochloric acid converts pepsinogen into its active form, pepsin. the pepsin digests proteins into polypeptides. physical: peristalsis in the stomach wall churns and breaks up the food into smaller pieces, and also mixes the food well with gastric juice for chemical digestion |
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digestion in the small intestine |
physical digestion: bile salts emulsify fats by lowering the surface tension of the fat (reduce the attractive forces between the fat molecules). this causes the fat to break into tiny fat droplets, increasing surface area to volume ratio of the fats and speeding up the digestion by lipase.
chemical digestion: -emulsified fats are digested by lipase to fatty acids and glycerol -starch is digested to maltose by pancreatic amylase -maltose is digested to glucose by maltase -lactose is digested to glucose and galactose by lactase -sucrose is digested to glucose and fructose by sucrase -proteins are digested to polypeptides by trypsin -polypeptides are digested to amino acids by peptidases |
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adaptations of the small intestine |
long - provides sufficient time for absorption inner walls are folded and have minute finger like projections called villi which in turn have microvilli - increase surface area of small intestine for efficient absorption one cell thick epithelium - short diffusion distance allows increased and faster absorption well supplied with capillaries and lacteals - allows digested food to be quickly absorbed and carried away, hence maintaining the concentration gradient and allowing efficient diffusion |
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define assimilation |
assimilation is the process whereby some of the absorbed food substances are converted into new protoplasm or used to provide energy |
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what: hepatic portal vein, hepatic vein and hepatic artery |
HPV: carries nutrient-rich blood to liver HV: carries remaining glucose and amino acids away from the liver to the rest of the body HA: carries oxygenated blood from tje heart to the liver |
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liver: regulation of blood glucose concentration |
too much glucose: insulin produced in the islets of langerhan is secreted, stimulating the liver to convert excess glucose into glycogen for storage. too little glucose: glucagon produced in the islets of langerhan is secreted, stimulating the liver to convert glycogen reserves to glucose to be released into the bloodstream. |
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liver: iron storage |
red blood cells are destroyed in the spleen, a gland found near the liver. their haemoglobin is brought to the liver which breaks down the haemoglobin to produce bile pigments and iron. the iron is stored in the liver |
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liver: protein synthesis |
the liver synthesises proteins found in blood plasma (prothrombin, fibrinogen) from amino acids in the diet |
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liver: deamination of amino acids |
excess amino acids are transported to the liver. their amino groups are removed and converted into ammonia then converted into harmless urea, which is removed from the body in our urine. the remains of the deaminated amino acids are converted to glucose. excess glucose is converted into glycogen and stored. |
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liver: detoxification |
the process of converting harmful substances absorbed into the system (eg. benzoic acid) into harmless substances is known as detoxification. liver cells contain an enzyme called alcohol dehydrogenase and it breaks down alcohol into acetaldehyde. it can be further broken down into compounds which can be used in respiration to provide energy for cell activities |
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harmful effects of excessive alcohol consumption |
liver cirrhosis: liver cells are destroyed and replaced by fibrous tissues, making the liver less able to function. patients suffering from liver cirrhosis may have haemorrhage or have bleeding in the liver. -reduces self-control -causes symptoms of drunkedness -depressant which slows down brain functions -increases risk of gastric ulcers -lead to addiction -reaction time lengthens |
