SNC4M The Digestive System

SNC4M The Digestive System

What is digestion? Chemical and mechanical breakdown of organic molecules into units small enough for the body to absorb These molecules provide: 1. Energy resources 2. Essential chemical elements 3. Raw materials to build materials for the cell

Your taskshould you accept it Make a chart and fill it in as you go along: Organ Properties Function

Organs to Include Mouth Tongue Esophagus Stomach Small intestine Large intestine Rectum Anus Liver Gall bladder Pancreas

THE MOUTH Physical digestion chewing and teeth break food into smaller pieces Saliva moistens food (produced by salivary glands) Chemical digestion of starch by enzyme amylase, which is dissolved in saliva Canines 1 - Used for tearing Molars Used 2 for crushing Pre-molars 3 Used for grinding Incisors Used 4 for cutting

THE TONGUE Has taste buds that are groups of cells located on the tongue that enable one to recognize different tastes Assists with moving food around mouth while chewing

ESOPHAGUS What is this called? Food going down the esophagus has a new name, bolus. Peristalsis - contraction and relaxation of the smooth muscle down the esophagus moves bolus down to the stomach The cardiac sphincter opens to allow the bolus of food to enter the stomach

THE STOMACH Along with HCl (hydrochloric) acid, enzymes, and muscle contractions, the bolus is churned and broken down further into a solution called chyme The pyloric sphincter, regulates the movement of chyme to the small intestine. Chemical digestion of protein occurs here by the enzyme pepsin

How does it work? The ph of your stomach is about 1-2 (facilitates breakdown of protein) Stomach cells secrete hydrochloric acid (gastric juices) which helps to break down the food and kills pathogens A layer of mucous secreted by cells lining the stomach protects the stomach from damage

Cows have how many stomachs? Cows do not have 4 stomachs; they have one stomach with 4 digestive compartments They rely on micro-organisms (a large amount) to help digest cellulose (which comes from nutrient-poor grass)

SMALL INTESTINE 3 sections: duodenum, jejunum, ileum Digestion is completed here Undigested food (waste) passes on to the large intestine

SMALL INTESTINE 1 st section -duodenummajority of digestion 2 nd section -jejunumabsorption of nutrients such as carbohydrates and proteins occur here 3 rd section ileum-longest section; fats and bile salts are absorbed here

SMALL INTESTINE Contains little finger-like projections called villiwhich increase the surface area Why is this advantageous?

Regions of the Small Intestine Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 24.16a

The Intestinal Wall Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 24.17b, c

THE COLON (LARGE INTESTINE) Undigested food is not needed by the body Waste is stored and eliminated Absorption of water, vitamins, minerals, and inorganic salts Most of the water from food is reabsorbed here Bacteria that reside in the colon produce vitamin B 12

THE RECTUM Warehouse for poop Waste (feces) is stored here until it is ready to be excreted

THE ANUS Opening at the far end of the digestive tract through where stool leaves the body A muscular ring (anal sphincter) keeps the anus closed until a person has a bowel movement.

The Pancreas HCl enters the duodenum triggers the production of digestive enzymes Produces chemicals (bicarbonate) that neutralize stomach acids that pass from the stomach into the small intestine

The Liver The liver produces bile salts which are stored in the Gallbladder Gallbladder Bile salts aid in the physical breakdown, emulsification, and absorption of fats Bileis secreted into the small intestine (duodenum)

Gallbladder Small Intestine The bile salts produced by the liver, are stored in the gallbladder A hormone, CCK, triggers their release into the small intestine

Figure 24.21 The Gallbladder Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 24.21a, b

Review Food moves down the esophagus using muscle contractions, called peristalsis. The liver produces bile salts that break down fats. Bile salts are stored in the gall bladder. The gall bladder, stores the bile salts, and releases them when CCK is present. HOME The colon absorbs the remaining moisture The mouth contains different teeth, used for different purposes. The stomach breaks down the food, and passes it on to the small intestine The pancreas produces enzymes to digest the food The small intestine has three parts. The majority of digestion, and some absorption happens here.

Peristalsis

Peristalsis (contd.)

Peristalsis (contd.)

Intestinal Bacteria good? Scientists estimate that a healthy woman s body is inhabited by 750 trillion bacteria, yeast, and other microorganisms, mostly colonizing the GI tract ~3-5 lbs. of your total body weight! We ve evolved a mutually beneficial, symbiotic relationship with some bacteria

Beneficial Bacteria Many species manufacture B vitamins and vitamin K and help digest foods Good intestinal bacteria helps prevent bloating, gas, and yeast overgrowth by controlling the ph level, or acidity, of the intestines Fermented foods such as miso, tempeh, soy sauce, and yogurt introduce active probiotic cultures that help wedge out unfriendly bacteria

How long does it take? Digestion time varies depending on the individual For healthy adults, it's usually between 24 and 72 hours After you eat, it takes about six to eight hours for food to pass through your stomach and small intestine Elimination of undigested food residue through the large intestine usually begins after 24 hours