Our Digestive System

Objectives The structure of the gut - names of the parts What happens in each part Stages in food processing How food is moved

Task 1- Gut Structure Fill in the names of the parts of the gut using p.31 Do the flow chart at the bottom (note that the small intestine starts with the Duodenum, then has the Ileum)

What happens in the GUT Ingestion Taking in food Physical digestion Digestion=biting/chewing/churning food into small pieces Chemical digestion Enzymes breaking big chains into small molecules…….. Absorption These pass through gut wall into the blood Assimilation: Using the food in the body Egestion Undigested fibre + bacteria pass out as faeces

Peristalsis Muscles in the gut wall squeeze food along – like toothpaste in a tube

Copy and complete the worksheet to the right

Oesophagus Mouth Where does our food go when we swallow it?

What is Digestion? Why is it necessary? What does each part of the digestive system do?

Mouth Physical digestion Teeth Saliva Lubricate Chemical digestion

Starchy foods like bread are carbohydrates made of long chains of identical small sugar molecules. Starch 1 Sugar molecule

Food is taken in (INGESTED) and first broken down into smaller parts by the teeth in the mouth. = PHYSICAL DIGESTION It is mixed with saliva which -starts CHEMICAL DIGESTION of starch -lubricates food for swallowing. Mouth

Oesophagus peristalsis. epiglottis  Can you swallow while upside down?

Stomach hydrochloric acid microbes  Have you noticed that vomit tastes sour? That’s the hydrochloric acid. proteins

AMINO ACIDS small enough to pass into the blood for…. Growth and repair Protein AMINO ACIDS. Digestion

Stomach Hydrochloric acid Microbes Proteins Amino acids Mucus  What stops the stomach digesting itself?

Food enters the stomach - a muscular bag, containing gastric juice and hydrochloric acid (HCl). 3 things happen here: Physical breakdown of the food - by churning Chemical breakdown of the proteins starts Microbes are destroyed by the acid. food enters from the gullet cross section of stomach digested food leaves muscle tissue The stomach

After 4 hours the stomach pushes the food out through this hole, the pyloric sphincter.

DUODENUM Is where digestion is finished GALL BLADDER PANCREAS oesophagus

Gall bladder liver bile gall bladder bile duct emulsify neutralise

Pancreas pancreatic juice carbohydrates, proteins, fats glucose amino acids digested fats

Digestion breaks large molecules up into small molecules so.. they can fit through the wall of the gut and pass into the blood Gut wall Gut contents blood

Small intestine = DUODENUM + ILEUM ILEUM Products of digestion ABSORBED into blood Ileum Pancreas Gall bladder Duodenum

Ileum wall looks like this. Why? Inside your ileum! Villi

Why breakdown large molecules into smaller ones? Ileum wall looks like this. Why?

Villi create a huge surface area so small molecules are absorbed quickly into our blood stream… Glucose Amino acids Digested fats What is left passes into the large intestine Vitamins Minerals

Ileum (small intestine) absorption villi surface area Moist thin walls

Colon (large intestine)

All that is left is waste material and water. WATER is re- absorbed into the blood WASTE MATERIAL ( fibre ) is left It passes to the rectum where it is stored until it leaves the body through the anus (EGESTION). Water

Rectum waste stored You have probably noticed that, once you have had a meal you often need to go to the toilet – to make room for the next lot of food!

Check this out! If your faeces float this should mean that you are eating enough fibre!

The Digestive System The whole point of digestion is… to break down our food into molecules that are SMALL enough to fit through the walls of our small intestine and go into the BLOOD so that we can use it in our CELLS to keep us alive

Products of digestion and their uses NutrientWhere digestedProduct of digestionUse Mouth Glucose (Sugar) Duodenum Protein Built back into proteins for ………….. + repair Fat Fatty acids + glycerol Built back into fat for energy store and ……………….. Digestion not necessary Small enough to be a………………….. unchanged To stay healthy NOT digestedUnchanged Keeps food ……………. through gut

Products of digestion and their uses NutrientWhere digestedProduct of digestionUse Carbohydrate Mouth Glucose (Sugar) Energy store Duodenum Protein stomach Amino acids Built back into proteins for growth + repair Duodenum FatDuodenumFatty acids + glycerol Built back into fat for energy store and insulation Vitamins Digestion not necessary Small enough to be absorbed unchanged To stay healthy Minerals FibreNOT digestedUnchanged Keeps food moving through gut

Ileum Pancreas Gall bladder Rectum

Digestion quiz