http://www.youtube.com/watch?v=Uzl6M1YlU3w http://www.youtube.com/watch?v=1nFwO-9iU5Y&feature=related

Chapter 6: Nutrition in Humans

Digestion The apple is too complex for your body to absorb directly. It needs to be digested first. Digestion is the physical and chemical breaking up of food into smaller components. http://www.youtube.com/watch?v=Uzl6M1YlU3w http://www.youtube.com/watch?v=1nFwO-9iU5Y&feature=related

Physical Digestion Physical digestion: mechanical break-up of food into smaller particles. Achieved through Chewing action of the teeth and tongue Churning action in the stomach What is the purpose? Increases surface area to volume ratio so that digestive enzymes can act on food more efficiently.

Chemical Digestion Chemical digestion: break-up of large molecules in food into smaller soluble molecules which can be absorbed. Achieved through Digestive enzymes in digestive system Eg. Starch Maltose What is the purpose? To get smaller soluble molecules which the body can absorbed. Amylase

Digestion What will be the consequences if a dog swallow a whole hot dog without chewing? The hot dog will not be digested completely even when it is goes through the dog’s digestive system. You may find traces of the hot dog in the dog’s fecaes. http://oboerista.files.wordpress.com/2007/11/hotdog.jpg

Passage of food 1. Mouth 2. Oesophagus 3. Stomach 4. Small Intestine 5. Large Intestine 6. Anus

Mouth and buccal cavity Ingestion is the taking in of food into the body through the mouth Mastication or chewing is the process by which food is crushed and ground by teeth.

Mouth and buccal cavity Purposes of chewing Reduced food sizes for swallowing Increases surface area for enzymes to work on Chewing stimulates salivary glands to secrete saliva Saliva contains salivary amylase Salivary amylase digests starch to maltose Digestion is the process of breaking down complex insoluble food substances into simple soluble food substances.

Pharynx Air Pharynx Epiglottis Oesophagus Glottis Larynx During swallowing, the larynx is raised and the glottis is covered by the epiglottis. During breathing, the larynx is lowered and the glottis is open.

Question- Can we eat food upside down? Yes, the muscles in our body push the food to where it should go. Yes, but we cannot drink upside down. No, gravity will pull the food out. Dick Harry Tom

Answer - Can we eat food upside down? Muth Answer - Can we eat food upside down? Video as proof: http://www.youtube.com/watch?v=ggRmedgQIL0&feature=related Yes, Dick is correct - we can eat and drink upside down!! Peristalsis is the rhythmic contraction of smooth muscles to propel contents through the digestive tract

Muth Oesophagus 1. Mouth 2. Oesphagus Oesophagus - Organ which consists of a muscular tube through which food passes from the pharynx to the stomach

Muth Oesophagus Peristalsis in oesophagus Longitudinal muscles Wall here dilates Circular muscles Wall here constricts (circular muscles contract and longitudinal muscles relax) Circular muscles relax Longitudinal muscles constract http://www.gastrointestinalatlas.com/English/Esophagus/Barrett_s_Esophagus_II/barrett_s_esophagus_ii.html

Digestion of different food Muth Digestion of different food Region of digestion Secretion Source Enzyme Action Mouth Saliva Salivary glands Salivary amylase Starch to maltose Stomach Gastric juice Gastric glands Pepsin Proteins to polypeptides Rennin caseinogen to casein

Digestion of different food Small intestine Bile Liver - Bile salts emulsify (NOT chemically digest) fats Pancreatic juice pancreas Amylase Starch to maltose Trypsin Proteins to polypeptides Lipase Fats to fatty acids and glycerol Intestinal juice Intestinal glands Enterokinase Trypsinogen to trypsin Maltase Maltose to glucose Lactase Lactose to glucose and galactose Surcase Sucrose to glucose and fructose Erepsin Polypeptides to amino acids

Muth Summary Ingestion Mastication Digestion Peristalsis 1. Mouth 2. Oesophagus 3. Stomach 4. Small Intestine 5. Large Intestine 6. Anus

Muth Absorption Products of digestion are absorbed throughout the small intestine. Epithelium Lacteal Blood capillaries Highly magnified epithelial cell fold To liver Microvilli Circular muscles Small intestine with portions cut off to show folds and villi Longitudinal muscles Magnified section of a villi

Absorption Jejunum Q. How is the small intestine adapted for absorption of digested food substances? Large surface area. Inner walls have numerous folds. Inner walls have villi – small finger-like projections. Microvilli found on villi. Thin walls for digested food substances to diffuse through (epithelium is only one cell thick) Lacteal transport fats and blood capillaries transport sugars and amino acids away from intestine to maintain concentration gradient for absorption. Ileum

Absorption Q. How does absorption take place in the intestines? Sugars and amino acids diffuse or actively transported into blood capillaries Glycerol and fatty acids diffuse into epithelium where they combine to form minute fat globules which enter the lacteals. Water enters by osmosis Water is mainly absorbed in ileum, partly in colon. Mineral salts either diffuse or are actively transported into blood capillaries in ileum and colon

Absorption Q. What is the difference between active transport and diffusion? Active transport uses energy from respiration to transport substances against a concentration gradient, BUT diffusion is an energy-free process as transport of substances is down a concentration gradient.

Undigested and unabsorbed food Q. What happens to undigested and unabsorbed food? The undigested and unabsorbed matter is stored temporarily in rectum before it is discharged as faeces through the anus. Egestion or defecation is the process of removing undigested food from the body. Rectum Anus

Inv 6.1 – How are carbohydrates absorbed? Visking tubing represents the small intestine epithelial. Distilled water represents the blood which carries away absorbed food substances away from intestine. Expected result is that starch will remain in the visking tubing as the starch molecules are too big. Glucose will diffuse through the visking tubing into the distilled water due to presence of concentration gradient. Cotton thread Visking tubing Boiling tube Solution of starch and glucose Distilled water

Summary Questions Q1. Mastication of food takes place in the buccal cavity. T/F Q2. Chewing stimulates the salivary glands to release salivary maltase. T/F Q3. Starch is the only food substance that is digested in the mouth. T/F Q4. Peristalsis is the rhythmic, wave-like contractions of the gut walls. It only take place along the oesophagus. T/F Q5. Bile contains lipase for the digestion of fats. T/F Q6. The abundant blood capillaries found in the small intestine transport away glucose, starch, amino acids and water away from the small intestine. T/F Q7. Most of the water in our body is absorbed along the large intestine. T/F

Transport and utilization of sugars What happens to glucose and amino acids absorbed in the small intestine? Carried by blood to the liver through the hepatic portal vein. Then carried by blood away from the liver to other parts of the body when glucose and amino acids are needed through the hepatic vein. Excess glucose is converted by liver and stored as glycogen. Excess amino acids are deaminated. Hepatic artery Hepatic vein Liver Hepatic portal vein Mainly sugars and amino acids Blood capillaries Small intestine

Functions of Liver 1. Regulation of blood glucose concentration 2. Production of bile 3. Iron storage 4. Protein synthesis 5.Deamination of amino acids 6. Detoxification

Functions of Liver 1. Regulation of blood glucose concentration 2. Production of bile 3. Iron storage 4. Protein synthesis 5.Deamination of amino acids 6. Detoxification

Functions of Liver 1. Regulation of blood glucose concentration 2. Production of bile 3. Iron storage 4. Protein synthesis 5.Deamination of amino acids 6. Detoxification Note that gall bladder stores bile but does not produce bile.

Functions of Liver Spleen RBC is destroyed where Brought to Haemoglobin transported to 1. Regulation of blood glucose concentration 2. Production of bile 3. Iron storage 4. Protein synthesis 5.Deamination of amino acids 6. Detoxification Haemoglobin is broken down in liver and iron released is stored.

Functions of Liver Amino group Carbon residue An amino acid Ammonium ion R 1. Regulation of blood glucose concentration 2. Production of bile 3. Iron storage 4. Protein synthesis 5.Deamination of amino acids 6. Detoxification NH2 – CH - COOH Amino group Carbon residue Ammonia (toxic) Glucose Urea (non-toxic) Glycogen

Functions of Liver This process of converting harmful substances into harmless ones is called detoxification. Harmful substances include benzoic acid and picric acid. Liver also contains an enzyme (alcohol dehydrogenase) to break down alcohol. Excess alcohol consumption may lead to gastric ulcers and cirrhosis. 1. Regulation of blood glucose concentration 2. Production of bile 3. Iron storage 4. Protein synthesis 5.Deamination of amino acids 6. Detoxification