Test 2 Flashcards
General principles of the GI tract
- The major portion of the GI tract is contained within the abdominopelvic cavity (part of esophagus in thoracic cavity)
- principle functions of the GI tract are digestion and nutrient absorption
- The motor innervation of the GI tract is via the autonomic nervous system. (can’t control)
ESOPHAGUS
- approximately 25-30 cm long (10 inches)
- extends from the lower part of the laryngopharynx and passes through the esophageal hiatus of the diaphragm. It makes an abrupt turn to the left from the esophageal hiatus and enters the cardiac opening of the stomach (LES (Lower esophageal sphincter) or cardiac sphincter)
- The cardiac sphincter is well developed circular muscle fibers, that prevent the regurgitation of food from the stomach. It is not a true sphinter.
ESOPHAGEAL FUNCTION
- tube that connects the larynx with the stomach
- acts as a passage between the two structures, so that the food can reach the stomach.
VASCULATURE of the Esophagus
- Arteries:
- upper third= inferior thyroid artery
- middle third= branches from the descending thoracic aorta.
- lower third= left gastric artery
- Veins:
- upper third portion= inferior thyroid veins
- middle third= azygous vein
- lower third= left gastric vein
LYMPHATIC DRAINAGE of the esophagus
- upper third drain into the deep cervical nodes
- middle third drain into the superior and posterior Mediastinal nodes
- lower third drain into the celiac nodes
Esophageal Varices
- In the event of portal hypertension, the development of esophageal varices can occur
- These veins dilate due to high pressure directly beneath the mucosa, and into the lumen.
- They are subjected to mechanical trauma during swallowing, vomiting, or the passage of diagnostic instrumentation.
Treatment for Varices?
- Varices banding
- EGD, grab varices and snap a rubberband around them
- helps with bleeding
Hiatal Hernia
- Herniation of the stomach through the esophageal hiatus produces a sac-like dilation above the diaphragm
- Gastric reflux may cause tissue changes in the distal esophagus
- Stomach tissue may begin to grow into the esophagus– Barrett’s esophagus – 10% chance of turning into cancer.
GERD & diagnosis & Treatment
- Gastric esophageal reflux disease (heartburn)
- Esophagitis – Gastric contents reflux into the esophagus, burning and inflaming the unprotected esophageal mucosa.
- diagnosis is made by: Manometry; Esophagoscopy; 24 hour pH measurements; cineradiography
- Tx: Antacids; Histamine2-receptor antagonists to reduce acidity; wt. reduction; Stop Smoking and drinking alcohol; elevation of the head at night.
- Surgical: Nissen fundoplicaion
Laparoscopic Nissen Fundoplication
- Surgical treatment for GERD
- wrap crus of stomach around esophagus
- stronger cardiac sphincter
Achalasia (symptoms, diagnosis, treatment)
- It consists of abnormal peristalsis in the body of the esophagus (stenosis (narrowing) of the esophagus)
- Symptoms: dysphagia, regurgitation, wt. loss and frequently respiratory symptoms due to aspiration
- Dx: X-ray studies; Esophageal manometry; Esophagoscopy
- Tx: palliative (releiving pain without fixing problem) dilation of stricture (with bougies); esophagomyotomy with care not to damage the vagus nerve
Tumors of the esophagus
- Benign tumors
- major problem is dysphagia, occasionally regurgitation and wt. loss
- Tx. is enucleation of tumor without violating mucosa. (ie. Snare)
- Malignant tumors
- Exact cause is unknown
- Dx: History of dysphagia and wt. loss; Contrast study; esophagoscopy; bronchoscopy; CT scan
- Tx: Surgical. Total thoracic esophagectomy with replacement with colon.
STOMACH
- located in the left hypochondriac and epigastric regions of the abdomen
- Because it is suspended by mesenteries, it is a mobile and easily displaced organ with no fixed position
- Empty, the stomach is almost tubular or J-shaped; except for the bulge of the fundus, it may be almost entirely under the rib cage for protection
- holds 2L of food
External Structure stomach
- composed of two sides, two curvatures, and two orifices
- The greater curvature, The lesser curvature
- The cardiac sphincter (LES) is connecting the esophagus to the stomach and pyloric sphincter connects the stomach to the duodenum
Internal Structure of the stomach
- The mucous membrane lining the stomach is thick and vascular. It is thrown into numerous folds, known as rugae, which are predominantly longitudinal in direction. On distention of the stomach, these folds flatten out. It contains the glands and the gastric pits.
Fibers of the stomach
- Longitudinal fibers
- Circular fibers
- Oblique fibers
Divisions of the stomach (regions, parts)
- The cardia
- The fundus
- The corpus or body
- The pylorus
FUNCTION of the stomach
- Trituration (mixing)
- formation of chyme
- acid enzymatic digestion and some absorption
- serving as a reservoir
VASCULATURE of the stomach
- Arterial supply-the celiac artery through its three branches:
- left gastric artery
- splenic artery
- common hepatic artery
Venous return and Lymphatic system of the stomach
- Veins generally parallel the arterial supply, but diverge significantly to join the hepatic portal system
- Lymphatic routes generally follow the arteries and are so named
COMMON PROBLEMS of the stomach
- Gastritis – excessive vagal activity may stimulate the acid secreting gland too much. Aspirin and steroids may also produce gastritis
- Peptic ulceration– occur in the non-acid secreting region of the upper GI tract. May cause severe bleeding, obstruction from edema or scarring and peritonitis from rupture. May be treated with drugs that block acid secretion or selective vagotomy (reduces peptic secretions) H. pylori can also cause pepric ulcers
-
Gastric Ulcers– Classified by location (stomach). More common in men
- Etiology: thought to be reflux of bile into stomach changing mucosal barrier and allowing gastric juices to damage mucosa; Drugs.
- Malignant Metastases – the venous and lymphatic drainage of the stomach is such that malignant cancer at this site can spread to other organs and regions.
Greater Omentum
- Apron like structure that is a double fold of double layer peritoneum
- It attaches to the greater curvature of the stomach and to the anterior surface of the transverse colon to cover the intestines
- Contains adipose tissue and provides infection control and helps prevent spread of peritoneal infection
Mesentery
- Double layered fold of peritoneum that contains the blood vessels, nerves, and lymphatic vessels that supply the intestinal wall.
SMALL INTESTINE
- divided into three parts but the differences are slight
- Duodenum
- Jejunum
- Ileum
Layers of the small intestine:
- Mucosa
- Submucosa
- Muscularis
- Serosa
DUODENUM
- shortest portion of the small intestine
- 10 inches in length from the pyloric sphincter to the duodenojejunal flexure
- Loops in a C shape to the right
- The suspensory ligament (of Treitz) is a surgical landmark – it basically denotes where it changes from duodenum to jejunum.
FUNCTIONS of duodenum
-
Primarily digestion
- The chyme is mixed with the products of the liver and pancreas and absorbs toward the distal portion
VASCULATURE of the duodenum
- Arterial supply – two sources
- celiac artery supplies the proximal and the
- superior mesenteric artery supplies the distal duodenum
- Venous supply –
- hepatic portal vein by way of the
- common hepatic vein and the
- superior mesenteric vein.
CLINICAL CONSIDERATIONS (duodenum)
- Since the venous and lymphatic route anastomose with those of the dorsal body wall, carcinoma of the duodenum and pancreas frequently has poor prognosis
- Most tumors are benign and most are polyps
- Duodenal ulcers (peptic) are four times more frequent than gastric ulcers and may require a Bilroth I gastroduodenal resection (small bowel resection) Complications include perforation, hemorrhage and obstruction. Dx and Tx similar to gastric ulcers.
JEJUNUM AND ILEUM
- The small bowel is supported by the mesentery proper. The jejunal loops tend to be in the left lateral region and the ileum tends to be in the pelvis. They are highly mobile (for peristalsis)
EXTERNAL STRUCTURES of Jejunum and Ileum
- Averages about 22 feet ( 15-34 feet). There is no distinct boundary
- Function is absorption. Villi increase the surface area.
VASCULATURE of Jejunum and Ileum
- Arterial supply
- superior mesenteric artery
- Venous return
- hepatic portal system via the superior mesenteric vein
- Lymphatic drainage
- absorb and transport triglycerides and well as lymph to the circulation via the thoracic duct
FUNCTION of Jejunum and Ileum
- Propel chyme through the gut. Segmentation occurs at the rate of about 10 contractions a minute and corresponds to the frequency of borborygmi (stomach rumble). Peristalsis is not very forceful in the jejunum but becomes very pronounced in the ileum
- Absorption of carbohydrates, triglycerides, and fatty acids, amino acids, vitamins, electrolytes, and water
How much of the small intestine can you excise and live a normal life?
- up to 1/3
- survival is possible with as little as 18 inches
Meckels diverticulum
- A true congenital diverticulum, is a slight bulge in the small intestine present at birth and a vestigial remnant of the vitelline duct
Intestinal Obstruction
(Mechanical or Paralytic obstruction)
- Mechanical: hernia, adhesions; tumor; intussusception; volvulus
-
Paralytic: most commonly seen after surgery
- don’t paristalse, bowel paralyzed, take drugs for it
- Effects of both: abdominal distention; loss of fluids and electrolytes; strangulation; gangrene perforation
- Cardinal symptoms: pain, absolute constipation, abdominal distention, and vomiting.
Inflammatory Bowel Disease
- Crohn’s Disease
- Ulcerative Colitis
- Etiology: Unknown – same for both
- Infectious agents
- Immunologic mechanism
- Genetic
- Psychological factors
Crohn’s disease
- A chronic recurrent granulomatous disease involving small and large intestine (either or both)
- Involves the entire thickness of the bowel
- Intestinal wall is thickened, edematous and fibrotic. Mesentery is thickened and infiltrated with fat. Lymph nodes enlarged
- The mucosal layer is “cobblestoned”.
- segmented can jump around
Crohn’s Disease Signs and Symptoms
- Perirectal abscess
- Occasional attacks of diarrhea
- Progressive malaise
- Low grade fever
- Weight loss (10-20 lbs)
- Abdominal pain
- Intestinal obstruction
- Massive bleeding
- Acute perforation pain mimicking appendicitis
- Fever
- arthritis
Crohn’s Disease Diagnosis
- Tenderness in right lower quadrant
- Palpable abdominal mass
- Anal fistula
- Stools may have occult blood
- Sigmoidoscopy is usually normal
STRUCTURE colon
- Approx. 5 feet long. Fat filled tags are scattered over the surface. Longitudinal bands, teniae coli are about 1 cm wide and most obvious on the cecum and ascending colon. Muscle tone in the teniae coli results in sacculations (haustra) along the intestine.
Ulcerative Colitis
- A diffuse inflammatory disease of unknown etiology involving the mucosa and submucosa of the large intestine
- Begins in rectum and proceeds proximal to involve entire colon. (no skip lesions like Crohn’s), continuous
- May lead to strictures.
Ulcerative Colitis Signs and Symptoms
- Bloody diarrhea
- Abdominal pain
- Fever
- Anorexia
- Weight loss
- 30-40 BM’s/day
- Weakness
- May lead to megacolon
- Cramping
- Fatigue
- Nocturnal diarrhea
Ulcerative Colitis Diagnosis
- Rule out other causes of bloody diarrhea
- Sigmoidoscopy
- Barium enema
- Endoscopic mucosal biopsy
- Colonoscopy
Complications of ulcerative Colitis
- toxic megacolon
- dilatation of colon
- systemic toxicity
- contributing factors to megacolon
- use of laxatives
- narcotics
- anticholingeric drugs
- hypokalemia
- colon cancer
Tx of Ulcerative Colitis
- depends on extent of disease and severity of symptoms
- control acute manifestations
- prevent recurrence
- avoid certain foods
- caffeine
- lactose
- spicy foods
- gas-forming foods
- fiber supplements (decrease diarrhea and rectal symptoms)
- medication
- surgical removal of rectum and entire colon
- ileostomy
- ileoanal anastomosis
similarities between Crohn’s Disease and Ulcerative Colitis
- inflammation of the bowel
- lack of known cause
- autoimmune reaction?
- infectious origin? ie. Chlamydia, atypical bacteria, mycobacteria
- pattern of familial occurrence; heredity component
- accompanied by systemic manifestations
- periods of remission and exacerbation
- diarrhea
- fecal urgency
- weight loss
- intestinal obstruction
What are 3 types of ostomies?
- ascending colostomy
- transverse colostomy
- descending colostomy
- bonus
- ileostomy
ASCENDING COLON
- Three parts: cecum, appendix and ascending colon proper.
- Its role is formation, transport, and evacuation of the feces. Its principle function is to convert liquid chyme into semisolid feces.
CECUM
- first part of the ascending colon. The ileocecal junction is the location which the ileum terminates by entering the colon
- ARTERIAL SUPPLY – iliocolic artery, the terminal branch of the superior mesenteric artery.
VERMIFORM (worm-like) APPENDIX
- A narrow, hollow, muscular structure that arises from the posteriomedial aspect of the cecum about 2-3 cm below the ileocecal orifice. Suspended by the mesoappendix from the dorsal body wall which contains the appendicular artery, a terminal branch of the iliocolic artery
- no function
ASCENDING COLON PROPER
- Located along the right side of the abdominal cavity. The right colic flexure (hepatic flexure) marks the transition between the ascending colon and the transverse colon.
- VASCULATURE
- Arterial supply is from the middle colic, right colic and ileocolic branches of the superior mesenteric artery
- Venous return is via the superior mesenteric vein to the hepatic portal vein.
TRANSVERSE COLON
- The second and longest segment begins at the hepatic flexure and traverses to the splenic flexure. Approx. 18-20 inches and suspended by mesentery
- VASCULATURE
- Arterial supply-middle colic artery
- Venous return-via superior mesenteric vein and hepatic portal vein.
DESCENDING COLON
- The initial segment is located along the left side of the abdominal cavity. Approx 10 inches. It is usually smaller in diameter due to the decreased size of the feces
- VASCULATURE
- Arterial supply – left colic branch of the inferior mesenteric artery
- Venous return – inferior mesenteric vein to the splenic vein or superior mesenteric vein.
SIGMOID COLON
- The colon becomes peritoneal again. Approx. 10-15 inches. mucosa is primarily mucous cells. The primary function of the sigmoid colon is storage of feces
- VASCULATURE
- Arterial supply – sigmoid arteries AND the rectosigmoid artery that arise from the inferior mesenteric artery
- Venous return– inferior mesenteric vein to the splenic vein or superior mesenteric vein
Lymphatics of the colon
- Lymphatic system is of considerable importance due to high frequency of colon cancer. The major drainage from the descending and sigmoid via the left colic nodes which drain into the inferior mesenteric nodes, the para-aortic nodes and the thoracic duct. Cancer may spread to the liver and to the lymph nodes of the abdomen and pelvis
RECTUM
- Approx. 5 inches long. The ampulla lies just above the pelvic floor and is the widest part of the rectum
- VASCULATURE
- Arterial supply – superior rectal (hemorrhoidal) artery , middle rectal (hemorrhoidal artery) and the inferior rectal (hemorrhoidal) artery
- Venous return – same but veins
- Lymphatics – parallel the arteries making metastasis wide within the abdomen and pelvis
CLINICAL CONSIDERATIONS OF RECTUM
- Prolapse of the rectum (turns inside out)
- Hemorrhoids– compression of the inferior mesenteric artery (protrussion of vessels)
- Polyps- removed by snare