Digestive System Digestive System Disorders Overview of Key

Digestive System & Digestive System Disorders

Overview of Key Idea 2 2. The digestion and metabolism of food influences the absorption and use of nutrients. • Explore the digestion of food and how process enables nutrients to be absorbed • Investigate factors that interfere with nutrient absorption • Investigate malabsorption syndromes and analyse strategies to manage the symptoms of these disorders through diet. • • Understand the importance of metabolism Identify how excess nutrients are stored Identify factors that determine BMR Understand how EER is calculated

What is Digestion? �‘Digestion is the process by which food and drink are broken down into their basic chemical structures in the gastrointestinal tract…’ (Magee & Oliver 2010) �‘Digestion is the mechanical and chemical breakdown of food to its smaller nutritional components…’ (Burnett- Fell et al 2011) �‘Digestion means breaking down foods in to smaller substances so that the body can absorb them…’ (Home Economics Association, 2008) �There are two key parts: Ingestion – process of taking food in to the digestive system Digestion – the mechanical and chemical breakdown of food

Functions of the Digestive System �The main tasks of the Digestive System are: Mechanical processing: � Movements Secretion � Release of digestive enzymes and other substances Digestion � Breakdown of food into nutrient molecules to enable absorption Absorption � Passage lymph that break up, mix and propel food material of digested nutrients and fluids into blood stream and Elimination � Undigested and unabsorbed food residue is expelled from the gut

Human Digestion involves a long chain of processes with different organs doing their individual jobs along the way.

Video – The Journey of the Digestive System http: //www. youtube. com/watch? v=e 3 O 1 Adl. C 8 b. I

What happens in the mouth? �Teeth shred the food into smaller pieces by a process called mastication. �Saliva is stimulated by the sight and smell of food. �Salivary glands secrete saliva into the mouth to moisten the food and help swallowing. �Saliva is a watery mixture of mucin and amylase. �These enzymes interact with food and begin the chemical digestion process.

What happens in the Oesophagus? �The oesophagus is the tube that joins the mouth to the stomach. �Peristalsis moves food a long the digestive tract Peristalsis is a series of involuntary wave-like muscle contracts �Takes 5 -10 seconds for food to pass from the mouth to the stomach �No breakdown of food �Its main function is to prevent acidic mixture in the stomach from splashing back up into the mouth.

What happens in the stomach? � The stomach is a large bag-like organ � The muscles lining the stomach grind the food and mix it with gastric juices and acid to produce chyme, a watery paste. � Small quantities of glucose, water soluble vitamins and minerals are absorbed in the stomach. � Nature of the food and degree of muscle action can affect the emptying of the stomach

What are the functions of the Stomach? � The stomach has three main functions: Food storage � An empty stomach has a volume of one fifth of a cup, but can expand to more than 8 cups after eating a large meal (http: //kidshealth. org/teen/your_body/body_basics/digestive_system. html# ) Disinfect food � Hydrochloric Acid kills bacteria Chemical Digestion � Pepsin is released to breakdown protein � When each function is complete the stomach empties its contents into the small intestine (duodenum).

What are the functions of the small intestine? �Approximately 6 meters long in an adult �Most digestion and absorption occurs here �The small intestine is divided into three distinct areas: Duodenum Jejunum Ileum

Small Intestine - Duodenum �Links the stomach to the small intestine �Food is digested here in small amounts �Gall bladder, liver and pancreas release bile and enzymes to complete the chemical breakdown of acidic stomach contents. Trypsin converts protein to amino acids Amylase breaks down starch Lipase breaks converts fats to fatty acids or glycerol.

Small intestine – Jejunum & Ileum �Jejunum is the coiled mid section �Ileum is the final section that leads to the large intestine. �Increase of villi and micro villi. �Fats are absorbed through the intestinal wall and carried to the liver via the bloodstream.

Liver & Gallbladder The liver produces bile: �Bile is an alkaline fluid stored in the gallbladder, which is discharged into the duodenum upon eating. �Breaks up fats by acting like detergents Bile emulsifies fats �The gall bladder, a small sac that is attached to the undersurface of the liver, holds bile.

Pancreas �The pancreas �Produces enzymes (pancreatase) to digest protein, starch and fat. �Pancreatic secretions neutralise stomach acids.

The lining of the small intestine contains finger like projections called villi. Through these villi nutrients are absorbed.

What are the functions of the large intestine? �Large intestine and rectum make up 1. 5 m of the gastrointestinal tract � 4 X thicker than the small intestine �Contains no digestive juices and all food has been absorbed by this time. �Main function is to remove food residue and waste from the body. �The residue includes cellulose, digestive juices, excess water soluble vitamins and bacteria.

What are the functions of the large intestine? �Large intestine produces no enzymes, but digestion still occurs due to bacteria. �Soluble fibre is digested by bacteria in large intestine. This provides nourishment for the cells in the walls of the intestines and helps protect against diseases.

What is the function of the rectum? 20 �Last section of colon (Large intestines) Mucus is secreted to aid the passage of faces to the rectum Eliminate faeces 12 to 24 hours after eating. �Undigested materials which is mainly cellulose from plants (fibre) �Masses of dead bacteria

Summary of where nutrients are absorbed Mouth Digestion of cooked starchy carbohydrates Stomach Digestion of protein Absorption of glucose, alcohol and water soluble vitamins and minerals Small Intestine Digestion of protein, carbohydrate, and fat Absorption of all nutrients except fibre Large Intestine Digestion of Fiber Absorption of Water Bowel (Rectum & Anus) Elimination of faecal matter

Summary of Macronutrient Absorption Macronutrient Carbohydrate Protein Lipids Site of Digestion Digestive chemicals involved Product(s) of Digestion Mouth Small Intestine Amylase Glucose Fructose Galactose (Monosaccharides) Stomach Small Intestine Hydrochloric Acid Pepsin Amino Acids Fatty Acids and Glycerol Small Intestine Bile Lipase

Digestive System Disorder - Ulcers �‘A stomach or gastric ulcer is a break in the tissue lining of the stomach. The term 'peptic ulcer' refers to those that occur in either the stomach or… the duodenum. ’ (Betterhealth Channel 2011) �Commonly thought stress, smoking and diet were responsible for stomach ulcers; however Helicobacter pylori (H. pylori) bacterium is now known to be responsible for most duodenal ulcers and 60 per cent of stomach ulcers. (Betterhealth Channel 2011)

Digestive System Disorder - Constipation �‘Constipation is the passing of hard, dry bowel motions (stools) that may be infrequent or difficult to pass. ’ (Betterhealth Channel 2011) �Occurs when food stays in the intestine too long; thus, too much water is absorbed. �The most common causes of constipation include a change in routine, not enough fibre in the daily diet, not enough fluids and lack of exercise.

Digestive System Disorder – Diarrhoea �Diarrhoea is the frequent passing of loose, watery and unformed faeces. �The most common cause of diarrhoea is an infection of the intestines, such as gastroenteritis or food poisoning. �The intestinal lining becomes irritated and inflamed, which hinders the absorption of water from food waste. �Can result in severe dehydration, especially in infants

Video – Poo Analysis http: //www. youtube. com/watch? v=tw 6 eme 3 oz. QU

Digestive System Disorder – Gall Stones �‘Gallstones (biliary calculi) are small stones made from cholesterol, bile pigment and calcium salts…’ (Betterhealth Channel 2011) �Treatment depends on the size and location of the gallstones, but may include: Surgery Limiting fatty products and dairy products

Digestive System Disorder – Heartburn �Heartburn or reflux happens when the contents of the stomach back up into the oesophagus, causing a burning sensation.