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Tuesday, September 21, 2021

Motility of Small Intestine

Motility of Small Intestine

Motility of Small Intestine

MOTILITY AND DYSMOTILITY OF SMALL INTESTINE
MOTILITY AND DYSMOTILITY OF SMALL INTESTINE


The digestive status (fed versus fasting) is a key component of small bowel motility. Fasting small intestinal motility follows four cyclic phases, referred to as the migratory motor complex. The migratory motor complex consists of waves of electrical activity that sweep through the intestine every 90 to 120 minutes. In addition to facilitating the transport of indigestible substances from the stomach to the colon, the migratory motor complex also transports bacteria from the small intestine to the large intestine and inhibits the reflux of colonic bacteria to the terminal ileum. It has thereby been termed the “intestinal housekeeper.”

Lymph Drainage of Small Intestine

Lymph Drainage of Small Intestine

Lymph Drainage of Small Intestine

Lymph Drainage of Small Intestine


The lymph vessels of the small intestine begin with the central lacteals of the villi. At the base of the villi, each central lacteal joins with lymph capillaries, draining the nearby intestinal crypts. These lymph capillaries form a fine network within the lamina propria, in which the first lymphatic valves are already encountered. Many minute branches emerge from this network, penetrating through the muscularis mucosae into the submucosa, which hosts a sizable network of lymphatic vessels. The vessels of this network have conspicuous valves that prevent retrograde motion of the lymphatic fluid once it is inside the vessels. Progressively larger lymph vessels, receiving additional lymph from the layers of the muscularis mucosae and from the serosa and subserosa, pass toward the attachment of the mesentery to the small intestine. Within the mesentery, the lymph vessels travel alongside arteries and veins. These larger lymph vessels have been referred to as chyliferous vessels or lacteals because they transport emulsified fat absorbed from the intestines and appear as milky-white threads after the ingestion of fat-containing food. Lymph fluid traveling through these vessels encounters several juxtaintestinal (within the mesentery, alongside the intestines) superior mesenteric lymph nodes, which number some 100 to 200 and constitute the largest aggregate of lymph nodes in the body. They increase in number and size toward the root of the mesentery. In the root of the mesentery, larger lymphatic branches are situated, which lead into the central group of superior mesenteric nodes in the area where the superior mesenteric artery arises from the aorta.

Blood Supply of Small Intestine

Blood Supply of Small Intestine

Blood Supply of Small Intestine

Blood Supply of Small Intestine


For the typical pattern of arterial branching of the small intestines, please refer to Plates 1-1 and 1-2. In this section, we will describe the variations concerning the origin, course, anastomoses, and distribution of the vessels supplying the small intestine. These variations are so frequent that conventional textbook descriptions are inadequate for anyone attempting procedures in the area. Typically, the superior mesenteric artery supplies almost all of the small intestine aside from the proximal duodenum, which receives blood from the supraduodenal and superior pancreaticoduodenal arteries. These arteries are branches of the gastroduodenal artery, a branch of the common hepatic artery, which is itself a branch of the celiac trunk.

Structure of Small Intestine

Structure of Small Intestine

Structure of Small Intestine

MUCOSA AND MUSCULATURE OF DUODENUM
MUCOSA AND MUSCULATURE OF DUODENUM


The freely mobile portion of the small intestine, which is attached to the mesentery, extends from the duodenojejunal flexure to the ileocolic orifice, where the small intestine joins the large intestine. This portion of the small intestine consists of the jejunum and the ileum. They run imperceptibly into each other, the transition being marked by a gradual change in the diameter of the lumen and by several structural alterations.

Topography and Relations of Small Bowel

Topography and Relations of Small Bowel

Topography and Relations of Small Bowel

Topography and Relations of Small Bowel


The small intestine consists of a retroperitoneal portion, the duodenum, and a mesenteric portion made up of the coils of the jejunum and ileum. The total length of the mesenteric portion of the small intestine varies considerably. The average for adults is roughly 5 m. The proximal jejunum forms approximately two fifths of the mesenteric portion, and the ileum forms the remaining three fifths. The jejunum commences at the duodenojejunal flexure on the left side of the second lumbar vertebra or, occasionally, somewhat more cranially. The ileum terminates when it joins the large intestine in the right iliac fossa. Although the division between the jejunum and ileum is not grossly visible (the appearance of the arteries and histologic structure can be used to distinguish the two regions), the coils of the jejunum tend to be on the superior left side of the abdomen and those of the ileum on the inferior right side.

Development of Small Intestine

Development of Small Intestine

Development of Small Intestine

Development of Small Intestine


The small intestine includes the duodenum, jejunum, and ileum. During development of the gastrointestinal system, the duodenum comes from the distal portion of the foregut, whereas the jejunum and ileum come entirely from the midgut. The duodenum moves to the right of the midline as the stomach rotates and shifts to the left side of the abdomen during weeks 4 to 6 of fetal life. As development proceeds, the common bile duct moves to the posterior side of the gut tube as the stomach rotates and the liver enlarges. One aspect of duodenal development that is clinically important is that during weeks 5 and 6, the epithelial lining of the duodenum, derived from the endoderm, proliferates to the point that it completely blocks the lumen of the duodenum. However, the lumen of the duodenum typically recanalizes so that the fetus can begin swallowing amniotic fluid. If the lumen of the duodenum does not recanalize or opens incompletely, duodenal atresia or stenosis will occur. As a region of gut that links the foregut and midgut, the duodenum is supplied by branches of both the celiac and superior mesenteric arteries. The descending and horizontal portions of the duodenum are the regions where this anastomosis occurs, and these are also the regions in which atresia or stenosis is most likely to be manifested.

Physiology of Gastroenteric Stomas

Physiology of Gastroenteric Stomas

Physiology of Gastroenteric Stomas

Physiology of Gastroenteric Stomas


Creation of a well-constructed ostomy by a highly skilled surgeon at the site of an anastomosis or as a cutaneous stoma that preserves normal digestive functions can result in an excellent quality of life for a patient undergoing resection of portions of the digestive system. Technical risks associated with the creation of any stoma include anastomotic leak, dehiscence, and stricture. The size of the anastomosis varies with the organs involved and the desired outcome of the procedure, but it is important to note that while stricture-related closure is always a risk, larger stomas are not always better. Cutaneous ostomies have an additional risk of prolapse, bleeding, and peristomal ulceration. Evaluation of ostomy function and anatomy may require skilled radiologic assessment with barium studies, CT studies, or endoscopy, or a combination of these studies. Endoscopic evaluation also provides the potential for therapeutic interventions to correct stomal problems, including dilatation and placement of self-expanding stents.

Abdominal Wounds: Blast Injuries

Abdominal Wounds: Blast Injuries

Abdominal Wounds: Blast Injuries

Abdominal Wounds: Blast Injuries


Abdominal wounds and blunt trauma are common acute injuries encountered in emergency settings. The depth and severity of a penetrating wound cannot be determined by history or physical examination alone. After stabilizing the airway, breathing and circulation, emergency cross-sectional imaging is essential as the operating room is being prepared and surgical expertise recruited. Broad-spectrum intravenous antibiotics should be hung on admission as the patient is prepped for operation. If extensive intraabdominal bleeding is occurring, laparotomy should be done as early as possible. Exploration must be thorough, and all perforations must be closed. Diversion of the fecal stream is often advised when there has been peritoneal soiling. In extensive damage, resection is necessary. In addition to customary preoperative and postoperative measures, oxygen, continuous gastroduodenal suction, multiple drains, and broad-spectrum antibiotic therapy are essential.

Cancer of Peritoneum

Cancer of Peritoneum

Cancer of Peritoneum

Cancer of Peritoneum


Primary malignant tumors of the peritoneum (meso-theliomas or endotheliomas) are rare, but secondary malignant tumors are relatively common. Tumor cell spread into the peritoneum occurs by direct extension, hematogenous spread, or lymphatic spread. Once the peritoneum has been invaded, dissemination of malignant cells throughout the peritoneal cavity and implantation diffusely throughout the peritoneal surfaces can occur rapidly. Epithelial primary carcinomas commonly metastasize to the peritoneum (e.g., adenocarcinomas of the stomach, intestine, ovaries, and, less commonly, lung and breast). Melanomas also frequently metastasize to the digestive system, including the mesentery. Malignant neoplasms of the retroperitoneal connective, nervous, or muscular tissue, as well as sarcomas and teratomas, although rare, invade the peritoneum or become metastasized within it.

Chronic Peritonitis

Chronic Peritonitis

Chronic Peritonitis

Chronic Peritonitis


Tuberculous peritonitis can occur at any age but is seen more commonly in young adults and children, patients undergoing dialysis, or immunocompromised patients such as those with acquired immunodeficiency syndrome. It is practically always secondary to some other focus in the body, the most frequent sources of infection being tuberculous lesions in the bowel, mesenteric glands, and fallopian tubes. In the course of general miliary tuberculosis, the tuberculous peritonitis may occur as an acute infection; much more commonly, however, it appears as a chronic condition that manifests itself in one of two main forms: (1) exudative or moist and (2) plastic or dry. In the first variety, the exudation is marked and the abdominal cavity becomes filled with a thin ascitic fluid; numerous tubercles, about the size of a pinhead or larger, appear on the peritoneal surfaces. In the second variety, the exudate is dense and rich in fibrin, formation of adhesions occurs most readily, and the viscera become matted together; the peritoneum is studded with tubercles, which, however, may be covered by deposits of fibrin; the omentum is often greatly thickened and rolled up. Caseous necrosis of tuberculous lesions may lead to formation of fistulous tracts. The two varieties may occur together, giving rise to the so-called encysted or encapsulated form characterized by loculated collections of fluid encysted by the dense adhesions.

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