Digestive System Chapter 11 Unit 10 Digestive System

Digestive System Chapter 11 Unit 10

Digestive System • The digestive system is the group of organs that changes food into a form that can be used by the body’s cells • The system is also known as the gastrointestinal(GI) tract or system • The digestive process can be divided into four phases: • 1. Ingestion: food is taken in • 2. Digestion: preformed by all the organs of the digestive tract • 3. Absorption: by the small intestines • 4. Elimination: by the large intestines, colon, and rectum

Digestive System • The main organs of the system are those through which the food passes • These organs form a continuous tube from the entrance to the exit of the body • They are the mouth, pharynx, esophagus, stomach, small intestine, and large intestine

The Mouth • Food enters the body through the mouth • Teeth break up food into small pieces to make it easier to swallow and also to prepare it for more effective action by digestive enzymes • The tongue contains taste buds and papillae projections

The Mouth • The salivary glands excrete the fluid known as saliva • It is released from three pairs of glands: the parotid, the submandibular, and the sublingual • Certain foods cause the glands to secret profusely often producing some discomfort, as when eating something sour

The Esophagus • Once food is swallowed, its movement through the body is maintained by the smooth, involuntary muscles called peristalsis • When food enters the esophagus, the muscles alternately contract and relax, squeezing the bolus(is a mass of food that has been chewed at the point of swallowing) • This moves the bolus to the stomach(only takes 5 seconds)

The Stomach • The upper opening to the stomach is controlled by a circular muscle called the cardiac sphincter • As the peristaltic wave approaches, the sphincter dilates, allowing the food to enter • Once the food is inside, the one-way “gate” closes to prevent its escape

• • • The Stomach The stomach is a 10 -inch-long, J shaped organ constructed of three layers of strong muscle tissue It lies just beneath the diaphragm It can hold about half a gallon of food and liquid The stomach continues the digestive process that began in the mouth The stomach lining is formed of mucous membrane, whose glands secret mucus The stomach has 35 million gastric glands, which secretes mostly hydrochloric acids(page 508 lists more enzymes) Hydrochloric acid can burn holes in things, and can destroy the stomach lining and cause ulcers An ulcer in the stomach is called a gastric or peptic ulcer The partially digested food in the stomach is changed into a semi-liquid state called chyme in 3 to 5 hours Liquids will pass through the stomach in minutes When the consistency of the chyme is right, the pyloric sphincter, at the end of the stomach, allows the chyme to spurt through the sphincter into the small intestine

The Stomach • Because of the two sphincters, food is held in the stomach until it is properly prepared to leave • But occasionally, when you suffer from nausea and vomiting, it is obvious the material did not go in the right direction • This action is accomplished by the contraction of the abdominal muscles, forcefully squeezing the stomach as it is pushed downward by the diaphragm • With this pressure and reverse peristaltic waves, the contents of the stomach are forced out and emesis(vomiting) occurs

The Small Intestine • The small intestine is a tube about 1 inch in diameter and about 20 feet in length • It completes the digestive process and absorbs the nutrients from the chyme • The small intestine is divided into three sections • The first is a C-shaped segment, about 9 inches long, called the duodenum • The next is the jejunum, and is about 8 feet in length • The last segment, about 12 feet long, is called the ileum

Small Intestine • The ileum is reduced to about half an inch in diameter by the time it joins the large intestine in the right lower quadrant of the abdomen • The small intestine completes the digestive process with the aid of accessory organs and sections by the glands of the small intestine

The Liver • The liver is the largest gland in the body • Its lies below diaphragm in the upper right quadrant of the abdomen extending into the upper left quadrant • The liver is a vital organ, that performs several functions • The liver secretes bile(water and pigments of rbc’s), this gives fecal material its yellowbrown color • The iron from destroyed cells in the liver are reabsorbed into the body

The Liver • The liver also stores glycogen, needed for blood sugar • Toxins (poisons) are pulled from the blood by the liver where for the most part are rendered harmless • The liver is a storage for area for blood and bodily fluids because of its large size

The Gallbladder • The gallbladder is a small sac attached to the underside of the liver(right side) • Its sole purpose is the concentration and storage of bile • When the body needs bile to digest food, the gallbladder releases bile to supplement that being produced by the liver • The common duct of the gallbladder empties the bile into the duodenum

The Gallbladder • Obstruction of the bile ducts from gallstones in the gallbladder is not uncommon • Frequently the stones will be expelled into the duct where they become logged, causing pain and inadequate supply of bile and requiring surgical removal • Medical term for gallstones is cholelithiasis(coliolathysis) • All stones are of mixed content to some extent. Those classified as mixed, however, contain between 30% and 70% of cholesterol. In most cases the other majority constituent is calcium salts.

The Pancreas • The pancreas lies behind the stomach, with the head in curve of the duodenum • If pancreatic juices are absent, serious digestive problems occur • The pancreas secretes directly into the bloodstream a substance called insulin • After you eat a meal, any carbohydrates you’ve eaten are broken down into glucose and passed into the bloodstream • The pancreas detects this rise in blood glucose and starts to secrete insulin.

The Absorption Function • When all the digestive juices and enzymes have been added and the chyme passes into the jejunum, digestion has progressed to the point where absorption of some nutrients and other substances can begin

Duodenum • It should be clear now why the duodenum is such a critical segment of the digestive tract, because it receives products from four organs - the stomach, liver, gallbladder, and pancreas • Any ulceration or tumors may interfere drastically with the digestive system and is a cause for concern

The Large Intestine • With digestion completed and the useful nutrients and other substances absorbed from the chyme, the waste products, and the excess water are sent into the large intestine • The large intestine is about 5 feet and approximately 2 inches in diameter • The colon as it is also called, frames the abdomen

The Large Intestine • The large intestine absorbs the liquid from the chyme • Some salts and proteins, are later filtered by the kidneys to be eliminated in the urine • The remaining fibrous waste materials are formed into feces to be eliminated through the rectum

The Appendix • The appendix is a wormshaped structure about the size of the little finger • It tends to become filed easily but drains rather slowly • Occasionally, a substance(stool)causes irritation to the lining, resulting in a painful, inflammatory process known as appendicitis • Appendicitis is a medical emergency that requires prompt surgery to remove the appendix. Left untreated, an inflamed appendix will eventually burst, or perforate, spilling infectious materials into the abdominal cavity

The Ascending, Transverse, And Descending Colon • The large intestine is divided into ascending, transverse, and descending sections as a means of identification • The first part of large bowel is the right colon or otherwise known as the ascending colon(leading upward) • Smallest of the colon • In the ascending bowel, the liquid stool is acted upon by bacteria(gut flora)

The Ascending, Transverse, And Descending Colon • The transverse colon begins at the hepatic flexure and extends in a loop across the abdominal cavity to the point below the spleen • This is the longest and most movable part of the colon • Cancers form more frequently here, as the contents become more solid (water is removed) in order to form feces

The Ascending, Transverse, And Descending Colon • The descending section extends downward along the left side of the abdomen until it reaches the edge of the pelvic cavity • It is firmly anchored to the abdominal wall to maintain its position • The function of the descending colon is to store food that will be emptied into the rectum.

The Sigmoid, Rectum, And Anal Canal • After the large intestine enters the pelvic cavity, it makes two bends suggestive of an S and is therefore labeled the sigmoid section of the colon • This extends from the left iliac crest over the back to join the rectum • The rectum serves as a collecting area for the remains of digestion, and is 6 to 8 inches long • When enough material is accumulated, sensors are activated, and the urge to defecate is felt

The Sigmoid, Rectum, And Anal Canal • The anal canal is a narrow passageway about an inch long, extending from the rectum to the anus (opening from the body)

Diagnostic Examinations • Colonoscopy: is the endoscopic examination of the large bowel and the distal part of the small bowel with a fiber optic camera on a flexible tube passed through the anus. • It may provide a visual diagnosis (ulceration, polyps) and grants the opportunity for biopsy or removal of suspected lesions.

Diagnostic Examinations • Barium swallow: is a test that may be used to determine the cause of painful swallowing, difficulty with swallowing, abdominal pain bloodstained vomit or unexplained weight loss • Compound that shows up on x-ray and is used to help see abnormalities in the esophagus and stomach

Diagnostic Examinations • • Esophagogastroduodeoscopy (EGD): is an examination of the lining of the esophagus, stomach, and upper duodenum with a small camera (flexible endoscope) which is inserted down the throat The endoscope is advanced through the esophagus (food pipe) to the stomach and duodenum Air is introduced through the endoscope to enhance viewing The lining of the esophagus, stomach, and upper duodenum is examined, and biopsies can be taken through the endoscope Biopsies are tissue samples that are reviewed under the microscope

Diseases And Disorders • Appendicitis: is swelling (inflammation) of the appendix. • Appendicitis is one of the most common causes of emergency abdominal surgery • It usually occurs when the appendix becomes blocked by feces, a foreign object(tumor) • Colitis: is swelling (inflammation) of the large intestine (colon) • Symptoms can include: abdominal pain and bloating bloody stools; or dehydration

Diseases And Disorders • Cirrhosis: is scarring of the liver and poor liver function. It is the final phase of chronic liver disease. • Symptoms may develop gradually, or there may be no symptoms (hepatitis or alcohol)

Diseases And Disorders • Colostomy: is a surgical procedure in which a stoma is formed by drawing the healthy end of the large intestine or colon through an incision in the anterior abdominal wall and suturing it into place

Diseases And Disorders • Crohn’s disease: is a type of inflammatory bowel disease that may affect any part of the gastrointestinal tract from mouth to anus, causing a wide variety of symptoms • It primarily causes abdominal pain, diarrhea, vomiting or weight loss

Diseases And Disorders • Diverticulitis: is the condition of having diverticula in the colon, which are outpocketings of the colonic mucosa and submucosa through weaknesses of muscle layers in the colon wall • Without fiber to add bulk to the stool, the colon has to work harder than normal to push the stool forward. The pressure from this may cause pouches to form in weak spots along the colon.

Diseases And Disorders • Gastroesophageal reflux disease(GERD): is a condition in which the stomach contents (food or liquid) leak backwards from the stomach into the esophagus • This action can irritate the esophagus, causing heartburn and other symptoms.

Diseases And Disorders • Hemorrhoids: are painful, swollen veins in the lower portion of the rectum or anus • Hernia: a sac formed by the lining of the abdominal cavity (peritoneum) • The sac comes through a hole or weak area in the fascia, the strong layer of the abdominal wall that surrounds the muscle.

Diseases And Disorders • Irritable Bowel Syndrome(IBS): is a disorder that leads to abdominal pain and cramping, changes in bowel movements, and other symptoms • In IBS, the structure of the bowel is not abnormal(not like chron’s dx) • Peptic ulcer: is a defect in the lining of the stomach or the first part of the small intestine, an area called the duodenum • Caused by alcohol, smoking, or regular use of aspirin or ibuprofen