Four Digestion processes Before the body can make use of the food you eat, the food has to be broken down to release the nutrients (digested). The nutrients are then absorbed into the bloodstream and taken to the cells where they can be used. Four Digestion processes Ingestion Digestion Absorption Egestion

Overview!

Not All food needs digesting! Simple sugars, water, vitamins & minerals are small molecules and can be absorbed as they are – they do not need to be digested! Where & HOW does absorption take place…?

Food group Mechanical -Teeth / stomach… Specific enzymes do their bit… End product & absorbed where… ?

Main regions of the alimentary canal and associated organs Mechanical Digestion? Chemical Digestion?

Digestion Is the breaking-up of food into small soluble pieces. Food in the stomach is mixed up and stored (turned into a soup-like liquid) Stomach cells make enzymes (Pepsin) and hydrochloric acid are released to aid digestion This acid also kills bacteria present in food. Stomach – bag with lots of muscle in its walls… Food held ~ 1-4 hours, liquids ~ a few minutes

Food is then slowly released into the small intestine (gut) where most of the digestion happens. First part – Duodenum Where pancreas & bile fluids added joins

Small intestine ~ 6 meters long

Gall bladder stores bile In the duodenum (enzymes ~ amylase, trypsin, lipase) from the pancreas are added and bile which is made in the liver is also added. The bile helps to neutralize the acid from the stomach and also helps to break the fat into little droplets.

Absorption: the movement of digested food molecules through the wall of the intestine into the blood

Absorption Is when food nutrients pass through the gut wall and into the blood stream. The lining of the small intestine is folded and has little finger-like projections called villi which increase the area for absorption. The surface is only one cell thick which speeds up the absorption of nutrients. Cells covering the villi make enzymes eg Lactase (breaks down lactose in milk)

By this stage most carbs – broken to simple sugars, proteins Discussion: What is the small intestine for? Why are there villi on the inner surface of the small intestine? By this stage most carbs – broken to simple sugars, proteins to amino acids and fats to fatty acids & glycerol

What about the Liver? Blood from the digestive system must first filter through the liver before it travels anywhere else in the body. The principal roles of the liver include removing toxins from the body, processing food nutrients and helping to regulate body metabolism (how your body gets its energy). Also produces bile…

In the Large Intestine (colon & Rectum), water and any remaining minerals are absorbed What is left consists of remnants of fibre, other undigested material and bacteria. Egestion The remains are formed into solid wastes (faeces / poo) and stored in rectum. They are removed from the body through the anus.