The alimentary canal of the GI tract consists of a hollow, muscular tube that begins in the mouth and ends at the anus. It includes the:

Accessory glands and organs that aid GI function include the:

Hunger is controlled by the lateral hypothalamus in the brain. A fall in blood nutrients, a rise or fall in hormones governing metabolism, hunger contractions from the stomach, and emotional input signal the hypothalamus to stimulate hunger. Fullness of the stomach, blood levels of nutrients and hormones, and emotions or habits stimulate the satiety center in the ventromedial area of the hypothalamus to decrease hunger.

The tongue provides the sense of taste and is the strongest muscle in the body. Saliva secreted from the salivary glands moistens the mouth and lubricates the food bolus to ease swallowing.

When a person swallows a food bolus:

The upper esophageal sphincter relaxes, allowing food to enter the esophagus.

The epiglottis closes with swallowing to prevent food from being aspirated into the trachea.

As food moves through the esophagus, glands in the esophageal mucosal layer secrete mucus, which lubricates the food and protects the esophageal mucosal layer from being damaged by poorly chewed foods. (See Choking hazards.)

Lower esophageal contractions (called peristalsis) gradually push the food down the esophagus and through the lower esophageal sphincter into the stomach.

The secretory cells in the lining of the stomach are believed to be functional at birth. The lining of the stomach secretes gastrin in response to stomach wall distention. In turn, gastrin stimulates the release of highly acidic digestive secretions consisting mainly of pepsinogen, which is converted to pepsin, hydrochloric acid, intrinsic factor, and proteolytic enzymes. Limited amounts of water, alcohol, and some drugs are absorbed in the stomach. Intrinsic factor is necessary for vitamin B₁₂ absorption.

The stomach’s three functions are to store food, mix food with gastric juices via peristaltic contractions, and slowly distribute this food (now called chyme) into the small intestine through the pyloric opening for further digestion and absorption.

Peristaltic contractions and various digestive secretions break down carbohydrates, proteins, and fats, enabling the intestinal mucosa to absorb these nutrients, along with water and electrolytes. Secretin and cholecystokinin are the hormones that affect intestinal secretions and gastric motility.

The surface area of the small intestine is increased by millions of villi in the mucous membrane lining. Digested food is absorbed through the mucosal walls and into the blood for distribution throughout the body. Failure to feed, malnutrition, ischemia, and infections affect the small intestine’s ability to absorb nutrients, resulting in growth delays.

From the ascending colon, chyme passes through the transverse colon and descending colon to the rectum, and finally into the anal canal, where it’s expelled. The anal sphincter voluntarily controls defecation except in infants and patients with spinal cord injuries.

The large intestine doesn’t produce hormones or digestive enzymes; it is, however, the site of water and sodium and potassium absorption. The mucosa produces alkaline secretions that lubricate the intestinal wall as chyme pushes through and protect the mucosa from acidic bacterial actions. The large intestine also harbors bacteria, such as Escherichia coli and Enterobacter aerogenes, which help to break down cellulose into usable carbohydrates and synthesize vitamin K. Vitamin K is needed by humans for blood clotting. Older children and adults get most of their vitamin K from bacteria in the gut, and some from their diet. Babies have very little vitamin K in their bodies at birth. Vitamin K does not cross the placenta to the developing baby, and the gut does not have any bacteria to make vitamin K before birth. After birth, there is little vitamin K in breast milk and breast-fed babies can be low in vitamin K for several weeks until the normal gut bacteria start making it. Infant formula has added vitamin K, but even formula-fed babies have very low levels of vitamin K for several days. With low levels of vitamin K, some babies can have very severe bleeding—sometimes into the brain, causing significant brain damage. This bleeding is called hemorrhagic disease of the newborn (HDN). As a preventive measure, babies are routinely given vitamin K injections at birth.

The liver is located in the right upper quadrant (RUQ) of the abdomen and is the body’s largest gland. It plays an important role in carbohydrate metabolism, detoxifies various endogenous and exogenous toxins in plasma, and synthesizes plasma proteins, nonessential amino acids, and vitamin A.

Bile is a greenish fluid that aids the small intestine to emulsify and absorb fats and fat-soluble vitamins and also neutralizes stomach acids. Bile exits through bile ducts that merge into the right and left hepatic ducts to form the common hepatic duct. This common duct joins the cystic duct from the gallbladder to form the common bile duct to the duodenum.

The pancreas is a large gland located behind the stomach and attached to the duodenum. The pancreas performs exocrine and endocrine functions. Its exocrine function involves cells that secrete digestive enzymes, bicarbonate, and hormones into the small intestine to aid in digestion.

Explain the procedure to the child and his parents. Prepare the child for insertion of the barium, and explain that he may be slightly uncomfortable as he changes positions on the X-ray table. Also explain that the child will have to wait until the test is over to go to the bathroom and that his bowel movements may look whitish until the barium has passed through his system.

A series of X-rays is taken while the swallowed barium or Gastrografin moves into the esophagus, stomach, and duodenum to reveal abnormalities. The barium outlines the stomach walls and delineates ulcer craters and filling defects. Gastrografin and barium facilitate imaging through X-rays, but Gastrografin is less toxic if it escapes from the GI tract.

A small bowel series is an extension of the upper GI series; additional imaging is done as the barium or Gastrografin flows farther down the GI tract through the small intestine to the ileocecal valve.

Obtain written, informed consent after explaining the procedure to the child and his parents. In addition:

Fiber-optic testing allows direct visualization of the GI tract. Different types of fiber-optic testing are used to examine different portions of the GI tract:

Nursing interventions focus on proper collection and handling of the specimen.

Explain to the child and his parents why the alternative feeding method is needed, and prepare the child for insertion of the feeding tube.

TPN is a highly concentrated solution of protein, glucose, vitamins, and minerals. It’s infused through I.V. tubing with a special filter to remove particulate matter and microorganisms. Lowglucose solutions may be administered through a peripheral I.V. line. High-glucose solutions are administered through central I.V. lines. Some medications, such as heparin and ranitidine (Zantac), may be added to the TPN solution and, therefore, shouldn’t be administered separately.

TPN is typically administered with an intralipid infusion that provides necessary lipids and calories.

Prepare the child for insertion of the NG tube with a simple, age-appropriate explanation. Because many children panic at the sight of the tube, it’s important to maintain a calm and reassuring manner and provide emotional support.

In addition, follow these steps:

An ostomy is created to correct an anatomical defect, relieve an obstruction, or permit treatment of an infection or injury to the intestinal tract. The most common reasons for an ostomy in infants and children are imperforate anus, necrotizing enterocolitis, Hirschsprung’s disease, and inflammatory bowel diseases.

An ileostomy is placed in the ileum portion of the small intestine. A colostomy is placed in the large intestine and may be ascending, transverse, or descending, depending on where it’s placed.

For older children and adolescents who are already concerned with appearance and acceptance by their peers, concerns about body image and, for the adolescent, sexuality are likely. Encourage the child to express these concerns and ask questions. (A same-gender nurse may be easier for the child to talk with.)

If possible, introduce the child to a peer who has had the procedure and is handling it well. Refer the child to other health care professionals who can help him deal with his body image issue. Also note the following: