A Tour of the Digestive System

A note about the small intestine… Most of digestion and absorption of nutrients occur here How long is your small intestine? About 6m (20 feet!)

Small intestine zones 3 Zones: Liquids enter duodenum from: Duodenum (first 25 cm) Jejenum Ilium Liquids enter duodenum from: 1. Liver 2. Pancreas 3. Gall Bladder

How it all fits together…

You can’t LIVE without it! (The liver) produces bile (up to 1.5L per day!), stored in the Gall Bladder a thick green liquid breaks fat into droplets What kind of digestion does bile perform? Mechanical or Chemical?

Gall bladder problems… Gall stones usually from hardened cholesterol pieces

Surgical removal is sometimes necessary… Q: How can you prevent gall stones from forming? A: Q: If you didn’t have a gall bladder, how would your diet need to change?

http://www.youtube.com/watch?v=1ZIK6Ua20JA&feature=channel_page

What else does the liver do? Keeps blood concentrations (of nutrients, hormones, glucose etc.) constant Changing nutrients (e.g. carbohydrates into fats, amino acids into carbohydrates and fats). Removes toxins from the blood

Destroys old red blood cells. Makes urea (from the breakdown of amino acids) Makes proteins in the blood Makes cholesterol Stores iron and vitamins

The Pancreas Connected to the duodenum by a duct Pancreatic juice has: Sodium bicarbonate  neutralizes the acidic chyme Enzymes to further break down food Pancreatic amylase Starch  maltose Trypsin Protein  peptides Lipase Fats  glycerol and 3 fatty acids

Fats break down to molecular level! Lipase Fatty Acid Glycerol Fatty Acid Glycerol Fatty Acid Fatty Acid Fatty Acid Fatty Acid Fatty Acids and Glycerol Fat

More Important pancreatic functions Regulation of blood sugar! How long do you typically go without eating in 24 hours? But your cells need a steady supply of blood glucose to function… not too much, not too little. How do you manage this?

Puzzle Time! Blood sugar rises to normal (90mg/100mL) Blood sugar falls to normal (90mg/100mL) Insulin is released from the beta cells of the pancreas Glucagon is released from the alpha cells of the pancreas Cells intake of glucose is enhanced Glycogen from the liver is broken down and released into the blood You eat a meal and blood sugar rises above normal You have not eaten for several hours and blood sugar lowers below normal The liver stores some of the glucose as glycogen Use the puzzle pieces to create the story of blood glucose regulation Hint: This story is not a linear one!

Key points: When you eat, your blood glucose level rises Between meals, your blood glucose is used up and levels fall Your pancreas releases two hormones into the blood: Insulin and Glucagon Insulin makes cells permeable to glucose Insulin sticks glucose molecules together to be stored in the liver as glycogen Glucagon breaks down glycogen (releasing glucose) Insulin Glucagon

What if you didn’t have insulin? Diabetes mellitus A few early symptoms: Increased thirst Large volume of dilute urine (Sugar present) Unexplained weight loss Increased fatigue Blurry vision (Type II) Cuts that are slow to heal (Type II)

Diabetes isn’t so sweet… Some secondary and long-term effects of untreated diabetes: Loss of vision Skin lesions (sores) Damage to gums Loss of limbs (amputation could be necessary) Chest pains / increased chance of heart failure Kidney disease

(usually juvenile onset) Type I diabetes (usually juvenile onset) Autoimmune disorder The beta cells of the pancreas are destroyed Must be controlled via regular insulin injections

Type II Diabetes (usually adult onset) Less insulin or it does not work as well Often controlled by diet and exercise Some people take drugs to increase sensitivity to insulin Blood sugar monitoring is essential