These cards cover digestion and the digestive tract.

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Stages in Digestion

Ingestion - taking large pieces of food into the body

Digestion - breaking down the food by mechanicall or chemical means i.e. chewing, enzymes (mouth, stomach)

Absorbtion - taking up the soluble products of digestion (small intestine)

Assimilation - using the absorbed materials (glucose in respiration)

Egestion - eliminating the undigested materials

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The ailimentary Canal

Mucosa - sectretes digestive juices, folded into villi to increase S.A.

Submucosa - contains blood vessels and lymph vessels. Also secretes digestive enzymes.

Muscle layer - made up of circular and longitudinal smooth muscle. Moves muscle through the ailimentary canal via peristalsis.

Serosa - tough connective tissue which holds the gut together and attatches it to the abdomen.

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Teeth and tounge physically break food into small pieces, to increase S.A and form a ball of food which can easily be swallowed.

The salivary glands secrete saliva, which contains - water, mucus, lysosomes and amylase

Water dissolves soluble substances.

Mucus for lubrication

Lysosomes to kill bacteria

Amylase partially digests starch

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Connects the mouth to the rest of the gut.

Glands secrete mucus to lubricate the foods passage down.

Food is moved down by peristalsis (an involuntary muscle contraction)

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This is an expandable bag where food is churned up into a liquid called chyme.

Gastric pits in the stomach release gastric juice, ehich contains - HCl, mucus and pepsin.

HCl kills bacteria.

Mucus lines the epithelium to protect it from the acid.

Pepsin digests proteins.

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Small intestine - Duodenum

Pancreatic juice secreated from the pancrease contains enzymes ( carbohydrase, protease, and lipase)

Bile, secreated by the liver stored in the gall bladder, contains bile salts to help with lipid digestion, and sodium hydrogen caronate to neutralise the HCl.

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Small intestine - illeum

Mucosa and sub mucosa secrete more enzymes, mucus and sodium hydrogen carbonate.

The S.A i increased by folds called villi and also cells with microvilli. These increase the rate of absorbtion.

The illeum is extremely long, which increases S.A. for the absorbtion of food.

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Large Intestine - Colon

Water is absorbed from the undigested materials to form semi-solid faeces. This is then pushed towards the **** via peristalsis, where it is released by the anul sphincter in excretion.

Mucus is secreted in the colon to lubricate the foods movement along the colon.

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