Digestive System

It’s responsible for chemically and physically digesting large insoluble molecules into smaller soluble molecules, which can be absorbed into the blood stream, And used for bodily processes (e.g. respiration, protein synthesis).

Amylase breaks down starch and glycogen into maltose

Moistens food and maintains pH (for enzyme activity)

The tongue moves food to the cutting and grinding surfaces of the teeth Tongue rolls food into a bolus which is swallowed

a ball like mixture of food and saliva that forms during chewing (mechanical digestion) which is swallowed into the stomach It’s the same colour as the food eaten, and saliva gives it an alkaline pH

A long tube which extends from the buccal cavity to the stomach. It’s responsible for pushing the bolus into the stomach using peristaltic waves of muscle contraction. It’s also lubricated with mucus.

Serosa (outermost) Muscle Layers Sub-mucosa Mucosa Lumen

The outer most layer of the gut made of a thick tough connective tissue to provide protection.

The second outer most layer of the gut. Used to contract in waves and squeeze food down (peristalsis)

The second inner most layer of the gut. Contains connective tissue, nerves, blood & lymph capillaries

Inner most layer of the gut. This area secretes mucus and can secrete digestive juices. In the ileum it’s covered with microvilli to increase SA

A J shaped organ found at the end of the oesophagus which physically churns up food using muscles from the stomach wall It also chemically breaks down food by releasing gastric juices

Produced by goblet cells throughout the digestive system (e.g. stomach) to lubricate food and protect organ walls from self digestion via enzymes

A digestive fluid produced within the stomach lining with an acidic pH made up of mainly HCl, mucus, endopeptidase (pepsin), lipase

Gastric glands in the mucosa

Produce hydrochloric acid (HCl) in the stomach which kills bacteria and lowers pH down to 2 (for optimum pepsin enzyme activity)

The inactive form of endopeptidase (pepsin) which is activated by HCl to break down polypeptides into peptides

Produces Bile

Stores Bile and releases it to the duodenum from the bile duct

Emulsifies lipids to maximise the SA for lipase enzyme action & digestion/absorption Alkaline in pH to neutralise stomach acid and form slightly alkaline (food)

Produces enzymes that are released into the duodenum via the pancreatic duct

The pancreatic enzymes produced by the pancreas and released into the duodenum by the pancreatic duct (slightly alkaline in pH)

Carbohydrase (pancreatic amylase) Lipase endo & exopeptidase

The start of the small intestine (connected to the stomach) where food is further digested on the epithelial cells of the villi