Digestive System of the Upper Torso

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ICD-10 Version:2016
By the end of the fourth week, the developing duodenum begins to spout a small outpouching on its right side, the hepatic diverticulum , which will go on to become the biliary tree. In this manner it prevents food from going into the trachea and instead directs it to the esophagus, which is behind. Lipase starts to work on breaking down fats. What Happens to a Hamburger? A milky fluid called chyle , consisting mainly of the emulsified fats of the chylomicrons, results from the absorbed mix with the lymph in the lacteals.

What Is the Function of the Liver?

Gastrointestinal tract

At the end of the jejunum, the wall of the intestine becomes more muscular, the lumen is narrowed, and an additional mesenteric attachment becomes apparent. The last 18 in. This junction is identified by the attachment of the ileocecal fold from the ileum to the dorsal band of the cecum. This ileocecal fold is used as a landmark to locate the ileum during abdominal surgery. The cecum is 4—5 ft 1. Under the influence of the cecal musculature, the ingesta in the cecum is massaged, mixed with microorganisms capable of digesting cellulose, and eventually passed through the cecocolic opening into the right ventral colon.

The attachment of the cecum to the dorsal body wall is wide, thus minimizing the likelihood the cecum can become displaced or twisted on its own. The right ventral colon is divided into sacculations that help mix and retain plant fibers until they are digested. It is positioned on the ventral aspect of the abdomen, extending from the flank region to the rib cage.

The ventral colon then turns toward the left, becoming the sternal flexure and then the left ventral colon. The left ventral colon, which also is large and sacculated, passes caudally to the left flank area.

Near the pelvic region, the diameter of the colon decreases markedly, and the colon folds back on itself. This region, called the pelvic flexure, is the initial portion of the unsacculated left dorsal colon. Presumably because of the abrupt decrease in diameter, the junction between the left ventral colon and pelvic flexure is the most common location for impactions. Equine GI anatomy relevant to colic, median section. The diameter of the dorsal colon is largest either at its diaphragmatic flexure or in the right dorsal colon.

There are no sacculations in either the left or right portion of the dorsal colon. The right dorsal colon is closely attached to the right ventral colon by a short intercolic fold and to the body wall by a tough, common mesenteric attachment with the base of the cecum. In contrast, neither the left ventral nor left dorsal colons are attached directly to the body wall, allowing these portions of the colon to become displaced or twisted.

The transverse colon is located cranial to the cranial mesenteric artery. Finally, the ingesta enters the sacculated descending colon, which is 10—12 ft 3—3. The celiac and cranial mesenteric arteries branches of the abdominal aorta supply blood to the GI tract.

The celiac artery supplies arterial blood to the stomach, pancreas, liver, spleen, and the first portion of the duodenum. The cranial mesenteric artery supplies arterial blood to the remaining portion of the duodenum; to all of the jejunum, ileum, cecum, large colon, and transverse colon; and to the first portion of the descending colon. Because the large colon is attached to the body wall only in the region near the cranial mesenteric artery, the blood supplying all portions of the colon must traverse the entire length of the colon.

The pelvic flexure receives its blood supply from two branches of the cranial mesenteric artery; one branch supplies the right and left dorsal colons before reaching the pelvic flexure, and the other branch supplies the right and left ventral colons before reaching the pelvic flexure.

Thus, volvulus of the large colon near the junction of the colon and cecum may impede the flow of blood to the entire left colon. The major branches of the cranial mesenteric artery can be damaged by the migrating forms of Strongylus vulgaris see Large Strongyles in Horses.

There are several natural openings or spaces within the abdominal cavity that can be important in conditions causing colic. The inguinal canal provides an opening through which intestine might pass and become trapped. Although inguinal hernias are common in young foals, they rarely cause clinical problems; the situation is considerably different in stallions.

Similarly, if the ventral abdominal wall fails to form properly around the umbilicus, an opening remains and the potential exists for intestinal problems to develop secondary to an umbilical hernia. The epiploic foramen, a natural opening between the portal vein, the caudal vena cava, and the caudate lobe of the liver, can be the site of intestinal incarcerations.

Finally, there is a natural space between the dorsal aspect of the spleen and the left kidney. This space is bounded by the renosplenic ligament, a strong band of tissue that connects the dorsomedial aspect of the spleen with the fibrous capsule of the left kidney.

Normograde peristalsis in the left ventral colon moves ingesta toward the left dorsal colon, and the muscles in the wall of the left dorsal colon contract to move the ingesta toward the diaphragmatic flexure. There is evidence, however, that the muscles in the left ventral colon contract in a retrograde fashion, from the pelvic flexure region toward the sternal flexure. Furthermore, these contractions appear to originate from a pacemaker region in the pelvic flexure.

It has been hypothesized that this pacemaker senses either the size or the consistency of the feed particles in the ingesta and then initiates the appropriate motility pattern. If the ingesta has been digested sufficiently, it is moved in a normograde direction; if additional digestion is necessary, the ingesta is moved in a retrograde direction to retain it in the ventral colon.

This theory has been proposed to help account for the common clinical occurrence of obstruction at or near the pelvic flexure. Numerous clinical signs are associated with colic. The most common include pawing repeatedly with a front foot, looking back at the flank region, curling the upper lip and arching the neck, repeatedly raising a rear leg or kicking at the abdomen, lying down, rolling from side to side, sweating, stretching out as if to urinate, straining to defecate, distention of the abdomen, loss of appetite, depression, and decreased number of bowel movements.

It is uncommon for a horse with colic to exhibit all of these signs. Although they are reliable indicators of abdominal pain, the particular signs do not indicate which portion of the GI tract is involved or whether surgery will be needed. A diagnosis can be made and appropriate treatment begun only after thoroughly examining the horse, considering the history of any previous problems or treatments, determining which part of the intestinal tract is involved, and identifying the cause of the particular episode of colic.

In most instances, colic develops for one of four reasons: This stimulates the stretch-sensitive nerve endings located within the intestinal wall, and pain impulses are transmitted to the brain. Under such circumstances, proinflammatory mediators in the wall of the intestine decrease the threshold for painful stimuli.

The list of possible conditions that cause colic is long, and it is reasonable first to determine the most likely type of disease and begin appropriate treatments and then to make a more specific diagnosis, if possible.

The history of the present colic episode and previous episodes, if any, must be considered to determine whether the horse has had repeated or similar problems or whether this episode is an isolated event. The duration of the present episode, the rate of deterioration of the horse's cardiovascular status, the severity of pain, whether feces have been passed, and the response to any treatments are important pieces of information. The physical examination should include assessment of the cardiopulmonary and GI systems.

The oral mucous membranes should be evaluated for color, moistness, and capillary refill time. The mucous membranes may become cyanotic or pale in horses with acute cardiovascular compromise and eventually hyperemic or muddy as peripheral vasodilation develops later in shock. The membranes become dry as the horse becomes dehydrated.

The heart rate increases due to pain, hemoconcentration, and hypotension; therefore, higher heart rates have been associated with more severe intestinal problems strangulating obstruction. However, it is important to note that not all conditions requiring surgery are accompanied by a high heart rate.

An important aspect of the physical examination is the response to passing a nasogastric tube. Because horses can neither regurgitate nor vomit, adynamic ileus, obstructions involving the small intestine, or distention of the stomach with gas or fluid may result in gastric rupture.

If fluid reflux occurs, the volume and color of the fluid should be noted. In healthy horses, it is common to retrieve The abdomen and thorax should be auscultated and the abdomen percussed. The abdomen should be auscultated over several areas cecum on the right, small intestine high on the left, colon lower on both the right and left. Intestinal sounds associated with episodes of pain may indicate an intraluminal obstruction eg, impaction, enterolith.

Gas sounds may indicate ileus or distention of a viscus. Fluid sounds may indicate impending diarrhea associated with colitis. A complete lack of sounds is usually associated with adynamic ileus or ischemia. Percussion helps identify a grossly distended segment of intestine cecum on right, colon on left that may need to be trocarized.

The respiratory rate may be increased due to fever, pain, acidosis, or an underlying respiratory problem. Diaphragmatic hernia is also a possible cause of colic. The most definitive part of the examination is the rectal examination. The veterinarian should develop a consistent method of palpating for the following: The intestine should be palpated for size, consistency of contents gas, fluid, or impacted ingesta , distention, edematous walls, and pain on palpation.

In healthy horses, the small intestine cannot be palpated; with small-intestinal obstruction, strangulating obstruction, or enteritis, the distended duodenum can be palpated dorsal to the base of the cecum on the right side of the abdomen, and distended loops of jejunum can be identified in the middle of the abdomen.

A sample of peritoneal fluid obtained via paracentesis performed aseptically on midline often reflects the degree of intestinal damage. The color, cell count and differential, and total protein concentration should be evaluated. Normal peritoneal fluid is clear to yellow, contains The age of the horse is important, because a number of age-related conditions cause colic.

The more common of these include the following: Ultrasonographic evaluation of the abdomen may help differentiate between diseases that can be treated medically and those that require surgery. The technique also can be applied transrectally to clarify findings noted on rectal palpation. In foals, echoes from the large colon and small intestine are commonly identified from the ventral abdominal wall, whereas only large-colon echoes are usually seen in adult horses.

The large colon can be identified by its sacculated appearance. The duodenum can be identified in the tenth intercostal space and traced around the caudal aspect of the right kidney.

The jejunum is rarely identified during transabdominal ultrasonographic examination of normal adult horses, whereas the thick-walled ileum can be identified by transrectal examination. The most common abnormalities identified by ultrasonography include inguinal hernia, renosplenic entrapment of the large colon, sand colic, intussusception, enterocolitis, right dorsal colitis, and peritonitis. Stallions with inguinal hernia have incarcerated intestine on the affected side; it is possible to identify the intestine and to obtain information concerning the thickness of its wall as well as the presence or lack of peristalsis.

In horses with renosplenic entrapment of the large colon, the tail of the spleen or the left kidney cannot be imaged, or the gas-filled large colon is present in the caudodorsal aspect of the abdomen in the region of the renosplenic space. Horses with sand colic have granular hyperechoic echoes originating from the affected portion of the colon. Very often the intestine proximal to the intussusception is distended, and the strangulated portion is thickened.

Horses with enterocolitis frequently have evidence of hyperperistalsis, thickened areas of the bowel wall, and fluid distention of the intestine. In contrast, horses with right dorsal colitis commonly have marked thickening of the wall of the right dorsal colon. In horses with peritonitis, the peritoneal fluid may be anechoic, or there may be evidence of flocculent material and fibrin between serosal surfaces of the viscera.

Horses with colic may need either medical or surgical treatments. Almost all require some form of medical treatment, but only those with certain mechanical obstructions of the intestine need surgery. The type of medical treatment is determined by the cause of colic and the severity of the disease.

In some instances, the horse may be treated medically first and the response evaluated; this is particularly appropriate if the horse is mildly painful and the cardiovascular system is functioning normally. Ultrasonography can be used to evaluate the effectiveness of nonsurgical treatment. If necessary, surgery can be used for diagnosis as well as treatment.

If evidence of intestinal obstruction with dry ingesta is found on rectal examination, a primary aim of treatment is to rehydrate and evacuate the intestinal contents. If the horse is severely painful and has clinical signs indicating loss of fluid from the bloodstream high heart rate, prolonged capillary refill time, and discoloration of the mucous membranes , the initial aims of treatment are to relieve pain, restore tissue perfusion, and correct any abnormalities in the composition of the blood and body fluids see Table: If damage to the intestinal wall as a result of either severe inflammation or a displacement or strangulating obstruction is suspected, steps should be taken to prevent or counteract the ill effects of bacterial endotoxins that cross the damaged intestinal wall and enter the bloodstream.

Finally, if there is evidence the colic episode is caused by parasites, one aim of treatment is to eliminate the parasites. Adapted, with permission, from Zimmel DN, Management of pain and dehydration in horses with colic. In most cases of colic, pain is mild, and analgesia is all that is needed.

In these instances, the cause of colic is presumed to be spasm of intestinal muscle or excessive gas in a portion of the intestine.

If, however, the pain is due to an intestinal twist or displacement, some of the stronger analgesics may mask the clinical signs that would be useful in making a diagnosis. For these reasons, a thorough physical examination should be completed before any medications are given. However, because horses with severe colic or pain may hurt themselves and become dangerous to people nearby, analgesics often must be given first.

Additionally, many horses with less severe problems may need pain relief until the other treatments have time to be effective. Medications used commonly for abdominal pain are NSAIDs that reduce the production of prostaglandins.

When these drugs are used as recommended, their toxic effects on the kidneys and GI tract occur infrequently.

Clinical experience suggests that flunixin meglumine may mask the early signs of conditions that require surgery and, therefore, must be used carefully in horses with colic.

Within a few minutes after administration, the horse stands quietly and is less responsive to pain. Unfortunately, the effects of xylazine are short-lived, and it inhibits intestinal muscular activity; it also decreases cardiac output and thus reduces blood flow to the tissues. Of the narcotic analgesics, butorphanol is used most often in horses with colic.

Butorphanol has few adverse effects on the GI tract or heart. However, when given in large doses, narcotics can cause excitement, and the horse may become unstable. Although pain relief usually is provided by analgesics, there are other important ways to reduce the degree of pain. For example, passing a nasogastric tube also an important part of the diagnostic evaluation may remove any fluid that has accumulated in the stomach because of an obstruction of the small intestine.

The removal of this fluid not only relieves pain from gastric distention but also prevents rupture of the stomach. Horses with displacement of the colon over the renosplenic ligament ie, left dorsal displacement of the colon may benefit from administration of phenylephrine.

This drug is given to contract the spleen and often is followed by light exercise on a lunge line in an effort to dislodge the entrapped colon. Many horses with colic benefit from fluid therapy to prevent dehydration and maintain blood supply to the kidneys and other vital organs. The fluids may be given either through the nasogastric tube or IV, depending on the particular intestinal problem see General Concepts Regarding Fluid Needs in Dehydrated Horses. Horses with strangulating obstruction or enteritis must be given fluids IV, because absorption of fluids from the diseased intestine is impaired and fluid may be secreted into the lumen of the intestine.

The latter mechanism causes a buildup of fluid in the intestine, which must be removed from the stomach through a nasogastric tube. This abnormal movement of body fluids into the intestine contributes to the development of circulatory shock, which is often the ultimate cause of death. In healthy horses, most of the fluid in the intestinal tract is reabsorbed in the cecum and colons. Therefore, horses with intestinal obstructions near the pelvic flexure usually require relatively small amounts of IV fluids, whereas horses with small-intestinal obstructions need extremely large amounts.

The volume and type of fluid to be given are determined by the severity and cause of the problem. Laboratory tests to determine the degree of hemoconcentration and whether concentrations of electrolytes are abnormal are critical for accurate treatment of horses with severe colic. The balance of body fluids can be reestablished by administering IV fluids formulated to replenish the deficient electrolyte s.

In most instances, however, fluid therapy must be started before laboratory results are available, particularly when the horse is showing clinical signs of circulatory shock. When IV fluids are needed but the clinical signs are mild to moderate, the horse is usually given 8—10 L of a sterile replacement fluid that contains electrolytes in concentrations similar to those that normally exist in the blood.

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Share your thoughts with other customers. Write a customer review. There was a problem filtering reviews right now. Please try again later. I bought this book for my 5th grade daughter since she had to do a written and oral report on the digestive system. The book is well written for anyone to understand. The pictures are fantastic. This book provided a majority of the information my daughter needed for her report.

The only reason I did not give this book a 5 star rating is because it didn't include very much information on disorders of the digestive system. That information would have been nice to see included, but we were able to get plenty of disorder information on the internet.

I didn't realize this was a children's book. One person found this helpful. The text of the book was perfect. It managed to combine technical words with a serious scientific tone with a certain simplicity and straightforwardness that was comprehensible, but still wonderful to read. I will be the first to admit I learned a great deal about the digestive system and would recommend it to anyone, child or somewhat silly adult like myself.

Initially, the colors and nature of the pictures bothered me somehow--not because of the "gross factor", but because I often had no idea what I was looking at. Sometimes a computer visualization is clearer, so I missed having some of those to help. But the text was so strong, it made up for that. You may not think much about your digestive system but as this book show it's always hard at work!

Guts tells us how the body digest food starting with our teeth and ending with the food beining made into waste. Full color photo are show through out the book to give us a better idea of our insides! What did you like or not like about the book? The information was written with children in mind.

I feel like it explained the topice well. Would you recommend the book? Why or Why not? Yes The content of the book is written in a simplistic manner, but is loaded with facts. I reviewed 10 of his writings for a class project in Children's Literature. He writes about the body in an interesting and informative way and peaks curiosity and leaves you wanting to know more. Seymour Simon is great for readers of all ages.

See all 5 reviews. Amazon Giveaway allows you to run promotional giveaways in order to create buzz, reward your audience, and attract new followers and customers. Learn more about Amazon Giveaway. Set up a giveaway. Customers who bought this item also bought.

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