The Digestive System

DIGESTION – the process of changing complex solid foods into simpler soluble forms which can be absorbed by body cells. ENZYMES – chemical substances that promote chemical reactions in living things.

ALIMENTARY CANAL digestive tract or gastrointestinal tract (GI Tract). A 30 ft. tube from mouth to anus. Accessory organs of digestion: Tongue Teeth Salivary glands Pancreas Liver Gall bladder

PERITONEUM Lining of the Digestive System – double-layered serous membrane that lines the abdominal cavity

Functions of the Digestive System Physical breakdown of food Chemical digestion of food into the end products of fat, carbohydrates and protein. Absorb nutrients into blood capillaries of the small intestines Eliminate waste products of digestion

Structure of Organs of Digestion MOUTH Food enters digestive system through mouth Inside of mouth covered with mucous membrane Roof of mouth is HARD PALATE (bone) and soft palate

UVULA flap that hangs off the soft palate prevents food from going up the nose when you swallow

TONGUE Attached to floor of mouth Helps in chewing and swallowing Made of skeletal muscle attached to four bones Taste buds on the surface

SALIVARY GLANDS Three pairs of glands PAROTID – largest salivary glands, they become inflamed during mumps Secrete saliva Acids, secreted by bacteria in the mouth to break down sugar, cause tooth decay An adult secretes about 2 pints of saliva a day

TEETH GINGIVA – gums, support and protect teeth MASTICATION – chewing, teeth help in mechanical digestion DECIDUOUS teeth – baby teeth (#20) Adult mouth has 32 teeth Some people never develop the back four molars (wisdom teeth)

Some people never develop the back four molars (wisdom teeth) A baby’s first teeth start to appear when it is about 6 months old By the age of 5, most children have 20 milk teeth, which later fall out to make room for adult teeth Adults usually have 16 teeth in each of the upper and lower jaws At the front of the mouth, in the upper & lower jaw, there are four incisors for cutting food

At each side of the incisors, there is a canine tooth (4 in all) which are for piercing the food Behind each canine there are two premolars & 3 molars, which are designed for grinding food. The enamel that covers teeth is the hardest substance in the body Molars have up to 4 roots, which anchor them securely in the jawbone. The nerves & blood vessels pass out through tiny holes in the base of each root The crown is broad & flat for crushing.

ESOPHAGUS ESOPHAGUS Muscular tube, 10” long Connects pharynx and stomach

STOMACH Upper part of abdominal cavity CARDIAC SPHINCTER – circular layer of muscle, controls passage of food into stomach PYLORIC SPHINCTER – valve, regulates the entrance of food into duodenum RUGAE – mucous coat lining of stomach in folds when the stomach is empty Stomach has muscular coat that allows it to contract (peristalsis) and push food into the small intestine

-The stomach can stretch to hold 4 pints of fluid -gastric glands produce about 6 pints of acidic fluid each day - Food spends 2-4 hrs. in the stomach

SMALL INTESTINE DUODENUM – first segment, curves around pancreas, 12” long JEJUNUM – next section, 8 ft. long ILEUM – final portion, 10-12 feet long ABSORPTION – in small intestine, digested food passes into bloodstream and on to body cells, indigestible passes on to large intestine

The small intestine is about 112 in. long The small intestine doubles in length when a person dies

Accessory Organs of Digestion PANCREAS Located behind stomach Exocrine function – secretes digestive enzymes Also has endocrine function

LIVER Largest organ in the body Located below the diaphragm, upper right quadrant Connected to gallbladder and small intestine by ducts

Functions: Produce and store glucose in the form of GLYCOGEN Detoxify alcohol, drugs and other harmful substances Manufacture blood proteins Manufactures bile Store Vitamins A, D and B complex

GALL BLADDER Stores and concentrates bile until needed by the body Small green organ, inferior surface of the liver When fatty foods digested, bile released by gallbladder

LARGE INTESTINE CHYME – semi-liquid food Approx 2” in diameter Also called the colon CECUM – lower right portion of large intestine Food usually spends at least 10 hrs. in the large intestine. It can be there for up to several days.

APPENDIX is finger-like projection off cecum RECTUM – last portion of large intestine ANUS – external opening

DIGESTION BOLUS – soft, pliable ball – creating from chewing and addition of saliva – it slides down esophagus PERISTALSIS – wavelike motions, moves food along esophagus, stomach and intestines

In the mouth… saliva softens food to make it easier to swallow PTYALIN in saliva converts starches into simple sugar under nervous control – just thinking of food can cause your mouth to water

In the stomach… gastric (digestive) juices are released stomach walls churn and mix (This mixture is chyme) small amount of chyme enters duodenum at a time - controlled by pyloric sphincter takes 2-4 hours for stomach to empty

In the small intestine… where digestion is completed and absorption occurs addition of enzymes from pancreas and bile from liver/gallbladder

In the large intestine… regulation of H2O balance by absorbing large quantities back into bloodstream bacterial action on undigested food – decomposed products excreted through colon – bacteria form moderate amounts of B complex and Vitamin K gas formation – 1-3 pints/day, pass it through rectum (FLATULENCE) 14 times a day, bacteria produces the gas

FECES undigested semi-solid consisting of bacteria, waste products, mucous and cellulose About 75%of feces is made up of water. The rest is mainly undigested plant fibers and germs Feces reach the rectum between 20 -44 hrs. after swallowing

DEFECATION when large intestine fills, defecation reflex triggered – colon and rectal muscles contract while internal sphincter relaxes – external anal sphincter under conscious control

Some people may have a bowel movement several times a day; some only twice a week. Both levels of activity are normal.

Digestive Disorders

HEARTBURN Acid reflux Symp – burning sensation Rx – avoid chocolate and peppermint, coffee, citris, fried or fatty foods, tomato products – stop smoking – take antacids – don’t lay down 2-3 hours after eating

GASTROENTERITIS Inflammation of mucous membrane lining of stomach and intestine Common cause = virus Symps – diarrhea and vomiting for 24-36 hours Complication = dehydration

ULCER Sore or lesion that forms in the mucosal lining of the stomach Gastric ulcers in the stomach and duodenal ulcers in the duodenum Cause – H. pylori (bacteria) is primary cause Lifestyle factors that contribute: cigarette smoking, alcohol, stress, certain drugs Symp – burning pain in abdomen, between meals and early morning, may be relieved by eating or taking antacid Diagnosis – x-ray, presence of bacteria Rx – H2 blockers (drugs) that block release of histamine ULCER

APPENDICITIS When appendix becomes inflamed If it ruptures, bacteria from appendix can spread to peritoneal cavity

HEPATITIS A Infectious hepatitis Cause – virus Spread through contaminated food or H2O Goes away on its own in most cases Does not lead to long term liver problems

How is hepatitis A spread? The disease is caused by the hepatitis A virus. The virus is found in the stool of an infected person. It is spread when a person eats food or drinks water that has come in contact with infected stool. Sometimes a group of people who eat at the same restaurant can get hepatitis A. This can happen when an employee with hepatitis A doesn't wash his or her hands well after using the bathroom and then prepares food. The disease can also spread in day care centers. Workers can spread the virus if they don't wash their hands well after changing a diaper. Some things can raise your risk of getting hepatitis A, such as eating raw oysters or undercooked clams. If you're traveling in a country where hepatitis A is common, you can lower your chances of getting the disease by avoiding uncooked foods and tap water.

Can hepatitis A be prevented? You can protect yourself from hepatitis A by getting a vaccine (Havrix or Vaqta). You will get it in a series of two shots. It is usually 100% effective if you get both shots before you are exposed to the virus. The U.S. Centers for Disease Control and Prevention advises that all children get the hepatitis A vaccine when they are at least 1 year old. If you have been around someone who you know has hepatitis A, the hepatitis A vaccine or an injection of immune globulin (IG) may prevent you from getting the disease. It’s important for you to get the shot within 2 weeks of being exposed to the virus.

How is it treated? Hepatitis A goes away on its own in most cases. You can help yourself get better faster by drinking lots of water and eating a healthy mix of foods. Unlike other forms of hepatitis, the hepatitis A virus does not lead to long-term illness or serious liver damage. Most people get well within a few months. While you have hepatitis A, cut back on daily activities until all of your energy returns. As you start to feel better, take your time in getting back to your regular activities. If you try to meet your regular pace too soon, you may get sick again. You can only get the hepatitis A virus once. After that, your body builds up a defense against it.

HEPATITIS B (Serum Hepatitis) Caused by virus found in blood Transmitted by blood transfusion or being stuck with contaminated needles (drug addicts) Health care workers at risk and should be vaccinated Use standard precautions for prevention Virus can live outside the body on a dry surface for up to 10 days Once infected, may take 1to 6 months for the infection and symptoms to develop

CIRRHOSIS Chronic, progressive disease of liver Normal tissue replaced by fibrous connective tissue 75% caused by excessive alcohol consumption

CHOLECYSTITIS Inflammation of gallbladder CHOLELITHIASIS Gallstones Can block the bile duct causing pain and digestive disorders Small ones may pass on their own, large ones surgically removed Surgical removal of gallbladder = CHOLECYSTECTOMY

DIARRHEA Loose, watery, frequent bowel movements when feces pass along colon too rapidly Caused by infection, poor diet, nervousness, toxic substances or irritants in food

CONSTIPATION When defecation delayed, feces become dry and hard Rx – diet with cereals, fruits, vegetables, (roughage), drinking plenty of fluids, exercise, and avoiding tension

JAUNDICE Yellow color of the skin