DIGESTION Yeo Yu Kheng Chua Cheng Leong Wang Jia Tan Tham Kit Win Matthew Lim
Parts of a Digestive System • Mouth • Gullet • Stomach • Small intestine • Pancreas • Liver • Gallbladder • Large intestine • Rectum
Before we start on the presentation, we shall watch a video to recap on the topic … http://www.youtube.com/watch?v=DtdSd9MUhik&feature=related
Let’s Recap! Mouth • Beginning of the digestive tract • Chewing breaks the food into pieces that are more easily digested • Saliva mixes with food to begin the process of breaking it down into a form your body can absorb and use Gullet • Receives food from your mouth when you swallow • Uses a series of muscular contractions to deliver food to your stomach
Let’s Recap! (II) Stomach • Holds food while it is being mixed with enzymes that continue the process of breaking down food into a usable form • Cells in the lining of the stomach secrete a strong acid and powerful enzymes that are responsible for the breakdown process Small intestine • 22-foot long muscular tube that breaks down food using enzymes released by the pancreas and bile from the liver. • Many tiny blood vessels used for the absorption of food after it has been completely broken down into the blood stream for daily life processes.
Let’s Recap! (III) Large intestine • Broader but shorter than the small intestine • Water and mineral salts absorbed through walls of small intestine • Undigested/ unabsorbed food turns semi-solid and hardens as water has been absorbed otherwise known as faeces Rectum • Faeces are temporarily stored in the rectum until it is ready to be passed out of the body through the anus
The liver The pancreas The gallbladder
Pancreas • Secretes digestive enzymes into the small intestine • Enzymes break down protein, fats, and carbohydrates • Makes insulin, secreting it directly into the bloodstream • Insulin is the chief hormone in metabolizing sugar in the body
Liver • Main function within the digestive system is to process the nutrients absorbed from the small intestine • Bile from the liver secreted into the small intestine also plays an important role in digesting fat • Takes the raw materials absorbed by the intestine and makes all the various chemicals the body needs to function • Detoxifies potentially harmful chemicals. It breaks down and secretes many drugs.
Gallbladder • Gallbladder stores and concentrates bile from the liver, and then releases it into the small intestine to help absorb and digest fats through bile ducts
Peristalsis Peristalsis is a series of wave-like muscle contractions that moves food to different processing stations in the digestive tract. It can defy gravity too (standing on your head). Small intestine Gullet Large intestine
Did you know… • Every day the salivary glands--small glands found in the mouth--produce approximately 1.7 litres of saliva each day • An adult's stomach can hold approximately 1 litre of food. The stomach is a sac-like structure surrounded by a muscular wall that provides elasticity. The stomach can expand to hold four times its normal volume • After you eat, it takes usually between 24 and 72 hours in healthy adults for the complete process of digestion to occur
References http://www.cchs.net/health/health-info/docs/1600/1699.asp?index=7041 Unit 1 Animal System -- Your Companion to Science, A complete guide to PSLE www.livestrong.com/article/130205-interesting-digestive-system/