1. Digestive System The digestive system is a group of organs working together to convert food into energy and basic nutrients to feed the entire body

2. Food passes through a long tube inside the body known as the alimentary canal or the gastrointestinal tract (GI tract). The alimentary canal is made up of the oral cavity, pharynx, esophagus, stomach, small intestines, and large intestines. It is about 9 yards in length. In addition to the alimentary canal, there are several important accessory organs that help your body to digest food but do not have food pass through them.

3. Accessory Organs Teeth Tongue Salivary glands Liver Gallbladder Pancreas

4. 2 forms of digestion Mechanical digestion—the breaking down of food into progressively smaller and smaller particles through tearing, cutting, grinding, and the moving of food along the digestive tract. Chemical digestion– the process where food is converted to substances usable by the body. Substances called enzymes speed up this process.

5. 1. Oral Cavity/Mouth Receives food and begins the preparation of food for digestion. Food is torn and ground into smaller pieces through mastication (chewing).--Mechanical Saliva from the salivary glands is added to the food as it is being broken down.—Chemical Teeth: Front teeth (incisors) have thin, sharp edges and tear and cut chunks of food from the main portion; Premolars and molars grind the food into even smaller pieces, increasing surface area so enzymes can contact food.

6. Salivary Glands. There are 3 sets of salivary glands that produce a watery secretion known as saliva that helps to moisten food and begins the digestion of carbohydrates. The body also uses saliva to lubricate food as it passes through the mouth, pharynx, and esophagus. 3 Salivary Glands: Parotid—largest, in front of the ear, produce large amounts of amylase, enzyme that digests carbohydrates. Submandiubular—in the floor of the mouth; secretes thick fluid. Sublingual—smallest, makes thick, stringy fluid. Right before you swallow food, it is called a bolus, mushed-up moist food.

7. Pharynx The pharynx, or throat, is a funnel-shaped tube that is responsible for the passing of masses of chewed food from the mouth to the esophagus. The pharynx also plays an important role in the respiratory system, as air from the nasal cavity passes through the pharynx on its way to the larynx and eventually the lungs.lungs Because the pharynx serves two different functions, it contains a flap of tissue known as the epiglottis that acts as a switch to route food to the esophagus and air to the larynx.epiglottislarynx

8. Swallowing The bolus is pushed into the pharynx with the aid of your tongue. Uvula—closes off the nasal cavity during swallowing (the soft, bag-shaped mass hanging from back of throat). Voluntary—forces food into pharynx with the tongue Peristalsis—food moves from esophagus into stomach by involuntary wave-like muscular contraction.

9. Esophagus The esophagus is a flexible, muscular tube 9-10 inches long, connecting the pharynx to the stomach.esophagus Once food has entered the esophagus, it doesn't just drop right into your stomach. Instead, muscles in the walls of the esophagus move in a wavy way to slowly squeeze the food through the esophagus. This takes about 2 or 3 seconds. At the inferior end of the esophagus is a muscular ring called the cardiac sphincter, which closes off the end of the esophagus and traps food in the stomach.

10. Stomach The stomach is a muscular sac shaped like the letter “J” that is located on the left side of the abdominal cavity, just inferior to the diaphragm.stomachdiaphragm In an average person, the stomach is about the size of their two fists placed next to each other. This major organ acts as a storage tank for food so that the body has time to digest large meals properly. The stomach also contains gastric juices and digestive enzymes (mucus) that continue the digestion of food that began in the mouth. Gastric juice is an acidic substance composed mainly of pepsin that breaks down proteins. HCl destroys bacteria, breaks down food, and helps absorb iron.

11. The stomach makes a churning action by way of muscle contractions, increasing the effectiveness of the gastric juices. The cardiac sphincter prevents them from flowing backwards and squirting up your throat. Stomach regions—cardiac, fundic, pyloric In the stomach, food becomes a semiliquid, creamy, homogeneous substance called chyme. Chyme leaves the bottom of the stomach through the pyloric sphincter.

12. Small Intestine (3-5 hours) The small intestine is a long, thin tube about 1 inch in diameter and about 20 feet long.small intestine It is located just inferior to the stomach and takes up most of the space in the abdominal cavity. The entire small intestine is coiled like a hose and the inside surface is full of many ridges and folds called villi. These folds are used to maximize the digestion of food and absorption of nutrients. By the time food leaves the small intestine, around 90% of all nutrients have been extracted from the food that entered it.

13. The small intestine has 3 subdivisions: duodenum (12 inches long)- this is where the pancreas and liver empty in; chemical digestion. jejunum (8 ft) ileum (twisted intestine)

14. Liver The liver is a roughly triangular accessory organ. The liver weighs about 3-4 pounds and is the second largest organ in the body.liver Functions of the liver: 1.Maintains correct blood sugar (glucose) levels. 2.Filters out and destroys old red blood cells and saves the iron to be used again. 3.Produced bile, which is needed for the digestion and utilization of fats. 4.Acts as a storehouse for a variety of vitamins (K, A, D, E, and B12). 5.Produces prothrombin which is needed for blood clotting. 6.Filters out harmful toxins that may be swallowed.

15. Gallbladder Bile made by the liver goes to the gallbladder. The gallbladder can store about 50 milliliters of bile. When fatty foods are eaten, this 7-10 cm long, pear- shaped organ is signaled to release bile to the duodenum via the common bile duct. Some of the bile used comes directly from the liver via the hepatic ducts. Bile breaks down fat like soap breaks down grease. After its broken down, the fat can be stored by the lacteals of the villi in the intestinal wall and used by the body.

16. Pancreas The pancreas is a large gland located in the U- turn between the stomach and small intestine.pancreas It is about 6 inches long and shaped like short, lumpy snake with its “head” connected to the duodenum and its “tail” pointing to the left wall of the abdominal cavity. The pancreas secretes hormones (insulin) and digestive enzymes into the small intestine to complete the chemical digestion of foods. They digest proteins and fats.

17. Stomach, Gall Bladder, & Pancreas

19. Large Intestine The large intestine is a long, thick tube about 2 inches in diameter and about 5 feet long.large intestine The large intestine absorbs water and salt contains many symbiotic bacteria that aid in the breaking down of wastes to extract some small amounts of nutrients. E. coli synthesizes vitamins (K and B complex) and works on undigested substances. Enters in the form of chyme, but exits the body in the form of feces through the anal canal through defacation.

20. Large Intestine or Colon

21. The digestive system has 6 main functions: The digestive system is responsible for taking whole foods and turning them into energy and nutrients to allow the body to function, grow, and repair itself. The six primary processes of the digestive system include: 1.Ingestion of food 2.Secretion of fluids and digestive enzymes 3.Mixing and movement of food and wastes through the body 4. Digestion of food into smaller pieces 5. Absorption of nutrients 6. Excretion of wastes

22. Ingestion The first function of the digestive system is ingestion, or the intake of food. The mouth is responsible for this function. The mouth and stomach are also responsible for the storage of food as it is waiting to be digested. This storage capacity allows the body to eat only a few times each day and to ingest more food than it can process at one time.

23. Secretion In the course of a day, the digestive system secretes around 7 liters of fluids. These fluids include saliva, mucus, hydrochloric acid, enzymes, and bile. Saliva moistens dry food and contains salivary amylase, a digestive enzyme that begins the digestion of carbohydrates. Mucus serves as a protective barrier and lubricant inside of the GI tract. Hydrochloric acid helps to digest food chemically and protects the body by killing bacteria present in our food. Enzymes are like tiny biochemical machines that disassemble large macromolecules like proteins, carbohydrates, and lipids into their smaller components.proteins, carbohydrates, and lipids Finally, bile is used to emulsify large masses of lipids into tiny globules for easy digestion.

24. The digestive system uses 3 main processes to move and mix food: Swallowing. Swallowing is the process of using smooth and skeletal muscles in the mouth, tongue, and pharynx to push food out of the mouth, through the pharynx, and into the esophagus. Peristalsis. Peristalsis is a muscular wave that travels the length of the GI tract, moving partially digested food a short distance down the tract. It takes many waves of peristalsis for food to travel from the esophagus, through the stomach and intestines, and reach the end of the GI tract. Segmentation. Segmentation occurs only in the small intestine as short segments of intestine contract like hands squeezing a toothpaste tube. Segmentation helps to increase the absorption of nutrients by mixing food and increasing its contact with the walls of the intestine. intestines

25. Digestion Digestion is the process of turning large pieces of food into its component chemicals. Mechanical digestion is the physical breakdown of large pieces of food into smaller pieces. This mode of digestion begins with the chewing of food by the teeth and is continued through the muscular mixing of food by the stomach and intestines. Bile produced by the liver is also used to mechanically break fats into smaller globules. While food is being mechanically digested it is also being chemically digested as larger and more complex molecules are being broken down into smaller molecules that are easier to absorb. Chemical digestion begins in the mouth with salivary amylase in saliva splitting complex carbohydrates into simple carbohydrates. The enzymes and acid in the stomach continue chemical digestion, but the bulk of chemical digestion takes place in the small intestine thanks to the action of the pancreas. The pancreas secretes an incredibly strong digestive cocktail known as pancreatic juice, which is capable of digesting lipids, carbohydrates, proteins and nucleic acids. By the time food has left the duodenum, it has been reduced to its chemical building blocks—fatty acids, amino acids, monosaccharides, and nucleotides.duodenum

26. Absorption Once food has been reduced to its building blocks, it is ready for the body to absorb. Absorption begins in the stomach with simple molecules like water and alcohol being absorbed directly into the bloodstream. Most absorption takes place in the walls of the small intestine, which are densely folded to maximize the surface area in contact with digested food. Small blood and lymphatic vessels in the intestinal wall pick up the molecules and carry them to the rest of the body. The large intestine is also involved in the absorption of water and vitamins B and K before feces leave the body.water

27. Excretion The final function of the digestive system is the excretion of waste in a process known as defecation. Defecation removes indigestible substances from the body so that they do not accumulate inside the gut. The timing of defecation is controlled voluntarily by the conscious part of the brain, but must be accomplished on a regular basis to prevent a backup of indigestible materials.