Year 9 – What lies within (Biology) The Digestive system Aim: name and describe function of main organs of digestive system

Year 9 – What lies within (Biology) Define term digestion. Explain the process of digestion in simple steps Identify and explain function of digestive enzymes. By the end of this lesson we should be able to:

Year 9 – What lies within (Biology) Digestion is the chemical and physical breakdown of large insoluble molecules into small soluble molecules. Let’s take a close look at how this happens… Open wide!

Year 9 – What lies within (Biology) Teeth mechanically break down the food. (physical) Saliva is added from the salivary glands – it contains an enzyme that starts digestion. (chemical ) Digestion starts in the mouth: Amylase = starts break down of carbohydrates

Year 9 – What lies within (Biology) Question???? What is the difference between physical and chemical digestion?

Year 9 – What lies within (Biology) All food enters our digestive system through the mouth and waste material leaves through the anus. If we stretch the digestive system out, we can see that it is really one long tube with an opening at each end. However, it is a 9m tube! Anus Mouth

Year 9 – What lies within (Biology) The ball of food is squeezed down through the gullet by the contraction of muscles lining the pipe. The process is known as Peristalsis. swallowing food bolus The Oesophagus/gullet

Year 9 – What lies within (Biology) Questions???? What is the scientific name of the food pipe? What is peristalsis?

Year 9 – What lies within (Biology) The stomach is basically a muscular bag, filled with Hydrochloric Acid (HCl) and enzymes that digest protein (proteases). food enters from the gullet Digested food leaves Muscle tissue protease enzyme mix with the food The Stomach

Year 9 – What lies within (Biology) Question Describe in detail the structure and function of the stomach?

Year 9 – What lies within (Biology) Although it is called small, it can stretch up to 6 meters in length. The small intestine contains all 3 enzymes to complete digestion: Carbohydrase Protease Lipase (fats) The Small Intestine

Year 9 – What lies within (Biology) Small Intestine Bile Duct Pancreatic duct Gall Bladder Pancreas and gall bladder: Pancreas adds all 3 enzymes to the small intestine. The gall bladder adds bile into the small int. which emulsifies fat (breaks up)/ alkali

Year 9 – What lies within (Biology) Questions?? Name the enzymes present in the small intestine – what do they do? Where do they originate from?

Year 9 – What lies within (Biology) Summarise -The function of bile Bile is made in the liver and stored in the gall bladder. It is added to the small intestine (alkali) to neutralise the acid from the stomach. Enzymes in the Small Int. work best in alkali conditions. Bile also starts emulsifying the fat. (break up into droplets) to give a big surface area for Lipase enzymes to work on. The small intestine is the first point fat is digested.

Year 9 – What lies within (Biology) Digestion is completed. Food is absorbed from the small intestine into the blood. A S B R O T P N O I BLOODBLOOD Any indigestible food will leave the small intestine without having been absorbed

Year 9 – What lies within (Biology) Large intestine (colon). LARGE INTESTINE BLOODBLOOD As the food enters this organ, all that is left is waste material and water. Water is reabsorbed into the blood..

Year 9 – What lies within (Biology) Question What is the function of the large intestine?

Year 9 – What lies within (Biology) Mouth Stomach Liver Large Intestine Rectum Gullet Pancreas Small Intestine Anus Here is a diagram of the system.

Year 9 – What lies within (Biology)