 Digestive System – also known as gastrointestinal system  Function: Physical and chemical breakdown of food so it can be taken into the bloodstream and used by the body’s cells and tissues.

 Digestive Systems consists of the Alimentary Canal and accessory organs:  Alimentary canal – long, muscular tube that includes the mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anus.  Accessory organs – salivary glands, tongue, teeth, liver, gallbladder and pancreas

Parts of Alimentary Canal  Mouth - also called buccal cavity or oral cavity  Food intake  Tasted  Broken down physically (teeth)  Lubricated and partially digested by saliva  swallowed

Teeth  Teeth - physically break down food by mastication (chewing and grinding).

Tongue  Tongue – muscular organ containing special receptors called taste buds. Taste buds allow a person to taste sweet, sour, salty, bitter sensations  Aids in chewing and swallowing food.

Hard Palate  Bony structure that forms the roof of the mouth and separates the mouth from the nasal cavities

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Soft Palate  Separates the mouth from the nasopharynx  Uvula – cone shaped muscular structure that hangs from the middle of the soft palate  Function of uvula – to prevent food from entering nasopharynx during swallowing

Salivary Glands and Saliva  3 Pairs of Salivary Glands (parotid, sublingual, submandibular) produce saliva.  Saliva – lubricates mouth during speech and chewing, and moistens food so it can be easily swallowed.  Saliva contains enzyme (a substance that speeds up a chemical reaction) called salivary amylase. This begins the chemical breakdown of carbohydrates, or starches, into sugars that can be taken into the body.

 After food is chewed and mixed with saliva it forms a bolus.  When bolus swallowed – enters the pharynx

Pharynx  Pharynx is a tube that carries both air and food  Carries air to the trachea (windpipe)  Food to the esophagus  When bolus is swallowed, muscle action causes epiglottis to close over the larynx to prevent bolus from entering respiratory system and causes it to enter esophagus.

Esophagus  Esophagus – approx. 10 inch long muscular tube dorsal (behind) the trachea.  Receives bolus from mouth and carries it to the stomach  Food is moved in a forward direction through the alimentary canal by peristalsis  Peristalsis – rhythmic, wavelike, involuntary movements

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Stomach  J-shaped muscular organ that acts as a bag or sac to collect, churn, digest and store food.  Receives food from the esophagus  Composed of 3 parts: fundus (upper region), body (main portion), antrum (lower region).  Mucous membrane lining of stomach contains folds called rugae. Rugae disappear as the stomach fills with food and expands.  Stomach is about the size of your fist, but can expand to hold up to a quart of food.

Sphincters of Stomach  Stomach contains muscular valves called sphincters.  Sphincters control the flow of food in one direction only.  Cardiac sphincter (or lower esophageal sphincter) – circular muscle between esophagus and stomach. Closes after food enters stomach and prevents food from going back into esophagus. Prevents regurgitation.

Stomach Sphincters cont’d  Pyloric sphincter – located at lower end of stomach and controls passage of food into duodenum of small intestine.  Keeps food in stomach while being mixed with gastric juices that aid digestion until ready to be released into small intestine.  Food remains in stomach for 1-4 hours

Med Tip  When the pyloric sphincter becomes abnormally narrow, a condition called pyloric stenosis results in which food is unable to pass from the stomach to the small intestine. Emesis (vomiting) is the main symptom.

Chemical Digestion in Stomach  While food is in stomach, chemical digestion occurs. Gastric juices are produced by gastric glands in the stomach.  Gastric juices such as hydrochloric acid and enzymes are released to convert the food into a semifluid substance called chyme.

Functions of Gastric Juices  Hydrochloric acid – kills bacteria, facilitates iron absorption, actives the enzyme pepsin.  Enzymes in gastric juices – lipase helps break down fats and pepsin starts protein digestion.  In infants, the enzyme rennin is released to aid in the digestion of milk. Rennin is not present in adults.

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Myth or Fact about your Stomach?  1. Myth or Fact: Digestion takes place primarily in the stomach.

Answer: Myth. The major part of the digestive process takes place in the small intestine. The stomach takes in the food, then churns it and breaks it into tiny particles called "chyme." The chyme are then released in small batches into the small intestine, where most digestion occurs, he says. Contrary to popular belief, foods do not digest in the order they are eaten. Everything lands in the stomach where it's all churned together, and when it's ready it's released into the small intestines together.

2. Myth or Fact: If you cut down on your food intake, you'll eventually shrink your stomach so you won't be as hungry

Answer: Myth Once you’re an adult, your stomach remains the same size.

 3. Myth or Fact: Thin people have naturally smaller stomachs than people who are heavy.

 Answer: Myth. While it may seem hard to believe, the size of the stomach does not correlate with weight or weight control. People who are naturally thin can have the same size or even larger stomachs than people who battle their weight throughout a lifetime. Weight has nothing to do with the size of the stomach. In fact, even people who have had stomach- reducing surgeries, making their tummy no larger than a walnut, can override the small size and still gain weight.

 4. Myth or Fact: Exercises like sit-ups or abdominal crunches can reduce the size of your stomach

 Answer: Myth. No exercise can change the size of an organ, but it can help burn the layers of fat that can accumulate on the outside of your body. Plus it can help tighten the muscles in the abdomen, the area of the body lying just south of the diaphragm, that houses the stomach and many other internal organs.  Interestingly, the part of your "belly fat" that can do you the most harm may actually be the fat you don't see. It resides in the "omentum," a kind of internal sheet that lies over and around your internal organs.

 5. Myth or Fact: One way to reduce acid reflux is to lose as little as 2 to 3 pounds.

 Answer: Fact. The less acid that flows back up into your esophagus, the fewer problems you will have clearing it. And believe it or not, losing just 2 pounds of weight from the abdominal area can make a difference -- and pregnancy is about the best example of this. As the baby grows and pushes against the internal organs, heartburn increases; but once the baby is born and the pressure is relieved, the heartburn is, too. In much the same way, losing even a little bit of belly fat can provide similar relief

 6. Myth or Fact: Beans cause everyone to make excess gas, and there's nothing you can do about it.

 Answer: Myth... sort of! Beans are high in a kind of sugar that requires a certain enzyme to properly digest. Some people have more if it, some people less. And the less you have, the more gas that will be produced during digestion of beans. What can help: Studies show that over-the-counter products that add more of the enzyme needed to break down the sugar in beans as well as other traditionally gassy vegetables can help if taken before you eat. After the fact, you can reduce the gas that forms by taking a product containing simethicone, which is a true bubble buster, releasing the surface tension on gas bubbles that form as a result of eating foods that are hard to digest.

Small Intestine  Food in the form of chyme enters the small intestine.  Small intestine  Coiled  Approx. 20 feet long and 1 inch in diameter  Divided into 3 sections: duodenum, jejunum, and ileum

Duodenum  First 10 inches of small intestine  Bile from gallbladder and liver and pancreatic juice from pancreas enter small intestine through ducts, or tubes.

Jejunum  Middle portion of small intestine  About 8 feet long

Ileum  Last portion of small intestine  12 feet long and is the longest portion of small intestine  Joins the large intestine at the ileocecal valve  Ileocecal valve is a muscular valve which prevents food from returning to the ileum  Attaches to cecum of large intestine

Digestive Process of Small Intestine  Process of digestion is completed in small intestine  Products of digestion absorbed into bloodstream for use by body’s cells  Walls of small intestine are lined with villi which contain blood capillaries and lacteals.  Blood capillaries carry digested nutrients to liver where they are stored or released to body cells  Lacteals absorb most digested fats into lymphatic system released to circulatory system

Large Intestine  Final section of alimentary canal  Approx 5 feet and 2 inches in diameter  Only waste, indigestible materials, and excess water go to large intestine

Functions of Large Intestine  Absorption of water and any remaining nutrients  Storage of indigestible material before eliminated by body  Synthesis (formation) and absorption of some B-complex vitamins and vitamin K  Transportation of waste products out

Sections of Large Intestine  Cecum  Connected to ileum of SI  Contains vermiform appendix  Colon  Ascending colon  Transverse colon  Descending colon  Sigmoid colon  Rectum  Final 6-8 inches of LI  Storage for indigestables and waste

 Rectum – Anal Canal – Anus  Fecal material (stool, waste, feces) - the final waste product of digestion is expelled through this opening (bowel movement - BM)

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Accessory Organs  Pancreas  Gallbladder  Liver

Liver  Largest gland in body  Located in RUQ  Function:  secretes bile which aids in digestion of fats  Stores sugar in form of glycogen  Stores iron and vitamins  Produces heparin – prevents blood clotting  Detoxifies substances such as alcohol, pesticides, and destroys bacteria

Gallbladder  Small, muscular sac located under liver  Stores and concentrates bile which it receives from the liver  When the bile is needed to emulsify fats in the digestive tract, the gallbladder contracts and pushes the bile through the common bile duct and into the duodenum.

Pancreas  Glandular organ behind the stomach  Produces pancreatic juices which contain enzymes to digest food  Juices enter duodenum through pancreatic duct  Amylase or amylopsin – sugar  Trypsin and chymotrypsin – proteins  Lipase and steapsin – fats

Pancreas  Produces insulin  Insulin: Regulates the metabolism, or burning of carbohydrates to convert glucose (sugar) to energy.

What happens to a hamburger?  You are getting ready to eat a hamburger which contains a buttered bread bun, a meat patty, and cheese.  What will happen to the hamburger at each stage of the digestive process: mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum