The Digestive SystemChapter 15, pages 422-428

Digestion• Digestion is the breaking

down of food into simpler substances to be carried in the blood to the body cells

• Mechanical Process – involves the chewing, mashing, and breaking food into smaller pieces

• Chemical Process – involves changing food into simpler substances

Function of the Digestive System

• Digestion – the mechanical and chemical breakdown of food for use by the body’s cells

• Absorption – the passage of digested food from the digestive tract into the circulatory system.

• Elimination – the expulsion of undigested food or body wastes.

Function of the Digestive System

• Food is moved through the digestive system by a process called peristalsis, which are a series of involuntary muscle contractions.

Structures of the Digestive System

• The Teeth – the primary function of teeth is to break the food into smaller pieces through mastication (chewing) to prepare the food to be swallowed.

Structures of the Digestive System

• The Salivary Glands – they are activated by the aroma of food.

• They secrete saliva which is a watery solution containing an enzyme that starts the digestion of carbohydrates by converting them into a soluble form of sugar

• It also lubricates your food making it easier to swallow.

Structures of the Digestive System

• The Tongue – forms the food into a ball (bolus) to prepare for swallowing and muscle contractions force the food into the pharynx (throat)

Structures of the Digestive System

• The uvula – a small, muscular flap of tissue suspended at the back of the mouth which closes over the opening of the nasal passages.

Structures of the Digestive System

• The Epiglottis – the flap of tissue that covers the trachea which closes to keep food from entering into the respiratory system.

Structures of the Digestive System

• The Esophagus – a 10 inch long, muscular tube that extends from the pharynx to the stomach. It is situated behind the trachea and the heart.

• Solid food takes about 9 seconds to travel through the esophagus.

Structures of the Digestive System• Sphincter Muscles – a

series of circular muscles, located along the digestive tract which prevents food from backing up as it moves through the digestive process.

• When relaxed, it forms an opening, and when contracted, it closes the opening.

Structures of the Digestive System

• The Stomach – A hollow, flexible, saclike organ, which is enclosed in three sets of muscles (longitudinal, circular, and oblique), which moves the stomach in different directions.

Structures of the Digestive System

• This action produces rhythmic contractions that churn the food and gastric juices together to produce chyme ( a creamy, fluid mixture of food and gastric juices).

• Peristalsis moves the chyme into the small intestine.

Structures of the Digestive System

• Gastric Juices – – Pepsin – an enzyme

that breaks down protein

– Hydrochloric Acid – the hydrochloric acid is strong enough to dissolve metal, but your stomach lining is protected by mucus

• Despite the stomach’s protective mucus, 500,000 cells of the lining are destroyed every minute and must be replaced.• Your entire stomach

lining is replaced every three days.

Structures of the Digestive System

• Small Intestine – consists of three parts (duodenum, jejunum, and the ileum)

• It is 20-23 feet in length and 1 inch in diameter

• It is where the major part of digestion and absorption occurs.

Structures of the Digestive System

• Chyme is moved through the small intestine at a relatively slow rate of approximately 3-5 hours.

• Chyme that enters includes partially digested carbohydrates, proteins, and undigested fat.

• Intestinal juices produced by glands in the small intestine, along with secretions from the liver and pancreas, complete the chemical breakdown of all food.

Structures of the Digestive System

• The small intestine is lined with millions of fingerlike projections called villi.

• Villi absorb digested food particles where it enters the capillaries of the villi into the bloodstream to be carried throughout the body.

Structures of the Digestive System

• Unabsorbed material leaves the small intestine in the form of liquid and fiber into the large intestine.

Structures of the Digestive System• The Large Intestine

(Colon) – a 5-6 foot and 2 ½ inch organ that forms the lowest part of the digestive system.

• Movement of undigested food materials through the large intestine is very slow.

• The main functions are to absorb water and eliminate undigested food.

Structures of the Digestive System

• As unabsorbed material from the small intestine passes through the large intestine, water, vitamins, and mineral salts are absorbed into the bloodstream to help maintain the water balance in your body.

• Many harmless bacteria live in your large intestine to change the consistency of undigested food to a semisolid waste (feces), which pass from your body through the anus and are excreted as a bowel movement.

Organs that Aid Digestion

• The Liver – the second largest organ in your body which functions as your body’s chemical factory and regulates the levels of most of the main chemicals in your blood.

Organs that Aid Digestion

• It clears the blood of drugs and poisonous substances by absorbing the substances and changing their chemical structure (making them water soluble).

• It then excretes them in bile (a yellowish-green, bitter fluid important in the breakdown of fats) through the hepatic duct to the gallbladder where it is stored.

Organs that Aid Digestion

• The gallbladder – a small pear-shaped sac about 3-4 inches long and located under the liver.

• The neck of the gallbadder forms a duct (bile duct) leading to the duodenum

Organs that Aid Digestion

• The gallbladder stores bile until food moves into the duodenum.

• A hormone produced in the small intestine then stimulates the release of the bile to break down fats contained in the food.

Organs that Aid Digestion

• The pancreas – as part of the endocrine system, the pancreas produce the hormone insulin.

• As part of the digestive system, the pancreas produces 3 digestive enzymes:– Trypsin which digests

proteins.– Amylase which digests

carbohydrates.– Lipase which digests fat

Care and Problems of the Digestive System

Lifestyle Habits• Follow a well-balanced

diet that includes a variety of foods that are low in fat and high in fiber.

• Eat slowly and chew your food thoroughly

• Do not wash your food down with liquid. Wait until you are finished chewing, swallow, and then take a sip of liquid.

• Drink at least eight 8-oz. glasses of water each day to help your digestive system function properly.

• Avoid using food as a way of dealing with your emotions. Instead, take a walk or write in a journal when you are stressed.

Functional Digestive System Problems

Indigestion

• A burning discomfort in the upper abdomen. It is a feeling of fullness, sometimes accompanied by gas and nausea.

• It can be caused from eating too much food, eating too quickly, and eating foods that are spicy and high in fat.

• Stomach disorders and stress can contribute to indigestion.

Heartburn

• A burning sensation in the center of the chest that may rise from the bottom, or tip, of the breastbone up to the throat.

Heartburn

• It results from acid reflux, or a backflow of stomach acid into the esophagus.

• As the acid enters the esophagus, it irritates the tissues causing a burning feeling

Heartburn

• Heartburn can also be a symptom of a hiatal hernia, a condition in which part of the stomach pushes through an opening in the diaphragm.

Heartburn

• Because frequent or prolonged heartburn can be an indication of more serious digestive disorders, it is important to discuss the symptoms with a medical professional

• They may recommend the use of an antacid or prescribe medications to help relieve symptoms.

Gas

• Although a certain amount of gas in the stomach and intestines produced from the breakdown of food is normal, excessive gas can result in cramps or an uncomfortable feeling of fullness in the stomach.

Gas

• Most foods that contain carbohydrates or complex sugars, such as beans, cabbage, broccoli, onions, and starches, can cause gas.

• Fats and proteins produce less gas than carbohydrates.

Nausea

• A feeling of distress, fullness, and weakness that often precedes vomiting.

• Motion sickness, pathogens (germs), some medications, and dehydration can cause nausea.

Nausea• Vomiting is a reflex

response that provides a built-in protection if you swallow a foreign substance.

• Powerful contractions of the abdominal muscles compress the stomach, while the esophageal sphincter relaxes to allow the contents of the stomach to exit

Diarrhea

• A frequent passage of watery feces.

• When digested food passes too quickly through the large intestine, water cannot be absorbed and diarrhea results.

Diarrhea

• Diarrhea may result from changes in eating style, overeating, emotional turmoil, or nutritional deficiencies.

• Bacterial or viral infections, and certain medications can also cause diarrhea.

Diarrhea• One of the greatest

concerns about diarrhea, especially in young infants and young children is dehydration.

• To avoid dehydration, drink plenty of fluids.

• Fluids containing electrolytes help maintain the body’s fluid and chemical balance

• Medical attention should be sought if symptoms persist for more than 48 hours.

Constipation

• A condition in which the feces become dry and hard and bowel movements are difficult.

• Constipation can be caused by not drinking enough water or not consuming enough fiber to move wastes through the digestive system.

• Some medications can also cause constipation.

Constipation

• Following a diet that includes fruits and vegetables, drinking at least eight 8 oz. glasses of water each day, and getting regular physical activity are the best ways to avoid constipation.

Structural Digestive System Problems

Gallstones

• Gallstones are formed when cholesterol in bile crystallizes and blocks the bile duct between the duodenum of the small intestine and the gallbladder

Gallstones

• Symptoms include pain in the upper right portion of the abdomen, nausea, vomiting, and fever.

Gallstones

• Treatment includes taking medications that dissolve the stones or having the stones broken down by high-intensity ultrasound waves.

• Surgical removal of the stones and possibly the gallbladder itself is an option when symptoms are severe.

Appendicitis• An inflammation of the

appendix, a tube about 3-4 inches long that extends from the beginning portion of the large intestine.

• The appendix becomes swollen and inflamed if it is blocked or clogged by bacteria or other foreign matter that prevents the release of its secretions.

Appendicitis

• Symptoms include pain in the lower right portion of the abdomen, fever, loss of appetite, nausea, and vomiting.

• The appendix may burst, spreading infection throughout the abdomen, making the condition extremely serious.

Appendicitis

• Medical care is essential and treatment involves surgical removal of the appendix.

Gastritis

• An inflammation of the mucous membrane that lines the stomach and is the most common disorder of the digestive system.

Gastritis

• An increase in the production of stomach acid, the use of tobacco or alcohol, infections caused by bacteria or viruses, and medications such as aspirin can irritate the stomach lining.

• Symptoms include pain, indigestion, decreased appetite, nausea and vomiting.

• Treatment includes avoiding irritants and taking medications or antibiotics to eliminate infection.

Lactose Intolerance

• Lactose, a type of sugar found in milk and other dairy products, is normally broken down by the enzyme lactase.

• People who are lactose intolerant do not produce enough lactase, so undigested lactose remains in the small intestine.

Lactose Intolerance

• Bacteria in the digestive tract ferment ingested lactose, producing symptoms such as abdominal cramps, bloating, gas and diarrhea.

• Chewing lactase enzyme tablets can reduce symptoms.

• People who are lactose intolerant should choose alternate sources of calcium including dark green vegetables such as broccoli and kale, fortified soymilk, and yogurt with active cultures.

Peptic Ulcer• A sore in the lining of the

digestive tract which can occur in the esophagus, stomach (gastric ulcer), or duodenum.

• They can be caused by regular use of anti-inflammatory drugs and by a bacterial infection caused by Helicobacter pylori (H. pylori)

Peptic Ulcer• Symptoms include

nausea, vomiting, and abdominal pain that worsens when the stomach is empty.

• Ulcers can cause bleeding in the stomach, and without treatment, they may perforate, or break through the stomach wall.

Peptic Ulcer

• Treatment includes medications that neutralize acid or eliminate infection and avoiding irritants such as aspirin, cigarette smoke, and alcohol.

Colitis

• An inflammation of the colon caused by a virus, an amoeba, a bacterium such as the one that causes ulcers, or stress.

• Symptoms include diarrhea (usually with blood and mucus), abdominal pain, and sometimes fever.

Hemorrhoids

• Swollen veins in the lower rectum and anus, as a result of increased pressure in the veins of the anus.

• They are most common in people with constipation, or who sit alot, pregnant women, and following childbirth

Hemorrhoids• Symptoms include

itching, pain, and bleeding.

• Eating fiber-rich foods and getting regular exercise can help reduce the risk of developing hemorrhoids.

• They can be treated with a variety of over-the-counter medications.

Cirrhosis

• Destruction of liver tissue, usually caused by prolonged and heavy alcohol use, resulting in a scarring of the liver tissue.

• Alcohol interferes with the liver’s ability to break down fats which blocks the flow of blood in liver cells.

Cirrhosis

• Liver tissue is destroyed and replaced with useless scar tissue, preventing normal liver function.

• Cirrhosis can lead to liver failure and may cause death unless a liver transplant is performed.

Crohn’s Disease

• A disease associated with problems of the immune system which causes inflammation of the lining of the digestive tract.

• Symptoms include diarrhea, weight loss, fever, and abdominal pain.

Colon Cancer

• Cancer of the colon and rectum is the second leading cause of cancer deaths in the United States.

• This cancer usually develops in the lowest part of colon, near the rectum

Colon Cancer

• As the cancer grows larger, it either blocks the colon or causes bleeding, often during elimination.

• Cancers of this type are usually slow to spread, so seeking early medical help greatly increases a person’s chance for survival.

Tooth Decay

• Tooth decay weakens a tooth and affects the way a person bites and chews food.

• Brushing and flossing daily is the best way to prevent tooth decay and to keep your teeth healthy.