Digestion Breakdown of large insoluble food molecules into

• Digestion: Break-down of large, insoluble food molecules into small, water-soluble molecules using mechanical and chemical processes. This occurs in the Alimentary Canal…

Alimentary canal – long muscular tube that runs from the mouth to the anus. Peristalsis – muscular movement of food

• 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 does absorption take place…?

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

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

Ingestion • Is the taking in of food into the mouth and swallowing it • Teeth and jaws grind the food into smaller bits • The saliva in the mouth contains enzyme (Amylase) which helps break up food chemically. The oesophagus is the tube which connects the mouth to the stomach

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

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)

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.