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Esophagus, Stomach, Duodenum and Intestines Medical Notes by Konstantin Ravvin

Posted in Medical Notes with tags , , , , , , , on February 25, 2016 by Konstantin

 

Esophagus

 

  • Associated with the esophagus, as it enters the abdominal cavity, are the anterior are the anterior and posterior vagal trunks
    • Anterior vagal trunk: consists of vagal trunks that mainly come from the left vagus
    • Posterior vagal trunk: consists of vagal trunks that mainly come from the right vagus
  • Arterial supply of the esophagus includes:
    • Esophageal branch of left gastric artery (from celiac trunk)
    • Esophageal branch of left inferior phrenic artery (from abdominal aorta)

 

Stomach

 

  • Divided into four regions:
    • Cardia: surrounds the opening of the esophagus into the stomach
    • Fundus: area above the level of the cardial orifice
    • Body of stomach: largest region of the stomach
    • Pyloric part: divided into antrum and canal at the distal end of the stomach (all below the angular incisures)
  • Most distal portion of the pyloric part is called the pylorus – marked by the pyloric constriction and contains a thickened ring of gastric circular muscle, the pyloric sphincter that surrounds the distal opening of the stomach, the pyloric orifice.
  • Other features of the stomach include:
    • Greater curvature, lesser curvature, cardiac notch (created from esophagus entering the stomach), and angular incisure (bend on the lesser curvature)
  • Arterial supply of the stomach
    • Left gastric artery from the celiac trunk
    • Right gastric artery from the hepatic artery proper
    • Right gastro-omental artery from gastro-duodenal artery
    • Left gastro-omental artery from splenic artery
    • Posterior gastric artery from gastric artery

 

Small Intestine

 

  • Extends from gastrointestinal tract to ileocecal fold
  • Approximately 6-7 m long
  • Duodenum: adjacent to the head of the pancreas and above the umbilicus; its lumen is the widest of the small intestine
    • Is retroperitoneal with the exception of its beginning, which is connected to the liver by the hepatoduodenal ligament (part of lesser omentum).
    • Divided into four parts:
      • Superior part: pyloric orifice à neck of gallbladder. Is just to the right of the body of vertebra LI, and passes anteriorly to the bile duct, gastroduodenal artery, portal vein, and inferior vena cava
        • Clinical Note: most duodenal ulcers occur here.
      • Descending part: right of the midline. Extends from neck of gallbladder to the lower border of L3. Anterior surface is crossed by the transverse colon, posterior to it is the right kidney, and medial to it is the head of the pancreas.
        • Contains the entrance of the bile duct (duodenal papilla) and the pancreatic ducts (minor duodenal papilla)
      • Inferior part: longest section, crossing the inferior vena cava, the aorta and the vertebral column. Crossed anteriorly by the superior mesenteric artery and vein.
      • Ascending part: passes upward on, or to the left of, the aorta to approximately the upper border of L2 and terminates and the duodenojejunal flexure
    • Arterial supply of duodenum:
      • Branches of the gastroduodenal artery
      • Supraduodenal artery from the gastroduodenal artery
      • Duodenal branches from the anterior superior pancreaticuduodenal artery.
      • Duodenal branches from the posterior superior pancreaticuduodenal artery.
      • Duodenal branches from the anterior inferior pancreaticuduodenal artery.
      • First jejunal branch from the superior mesenteric artery.
    • Jejunum: proximal two-fifths of the small intestine and is larger in diameter and has a thicker wall than the ileum.
    • Arterial supply of jejunum: jejunal arteries from the superior mesenteric artery
    • Ileum: makes up the distal three-fifths of the small intestine. Smller in diameter and thinner walls than jejunum with more mesenteric fat and more arterial arcades (connections)
      • Two flaps projecting into the lumen of the large intestine (the ileocecal fold) surround the opening. They come together to form ridges. Musculature from the ileum continues into each flap, forming a sphincter.
        • Possible function of iliocecal fold includes preventing reflux from the cecum to the ileum.
      • Arteries supplying the ileum:
        • Ileal arteries of superior mesenteric artery
        • Ileal branch of the ileocolic artery
      • Clinical note: differences in epithelial cells exists between the stomach and the esophagus at the gastroesophageal junction. Absence of this difference may predispose the region to adenocarcinoma.
    • Clinical Note: duodenal ulcers can be posterior or anterior.
      • Posterior ulcers: erode onto the gastroduodenal artery or onto the posterior superior pancreaticoduodenal artery, which can produce hemorrhage.
      • Anterior duodenal artery erode into the peritoneal cavity, causing peritonitis. This can cause the ileus to adhere to the greater omentum — attempting to seal off the perforation
    • Clinical Note: Meckel’s diverticulum
      • Proximal part of the yolk stalk (vitelline duct) remains. Can cause hemorrhage, diverticulitis, ulceration and obstruction
    • Clinical Note: Carcinoma of the stomach
      • Can be caused by chronic gastric inflammation, pernicious anemia, and polyps.

 

Large Intestine

 

  • Extends from the distal end of the ileum to the anus ( ~1.5 m)
  • Aborbs fluids and salts from the gut contents and forms feces.
  • Cecum à Ascending colon à right colic flexure à transverse colon à left colic flexure à discending colon àsigmoid colon
  • Larger diameter compared to that of the small intestine
  • Omental appendices: peritoneal-covered accumulations of fat
  • Longitudinal muscle in its walls are segmented into three narrow bands called the taenaie coli (primarily in the cecum and colon)
  • The sacculations of the colon are called huastra
  • Cecum and Appendix:
    • Cecum is intraperitoneal and is usually in contact with anterior abdominal wall
    • Appendix is attached to the posterior medial wall and it is suspended from the terminal ileum by the mesoappendix.
  • Clinical Note: Appendix
    • The surface projection of the base of the appendix is at the junction of the lateral and middle one-third of a line from the anterior superior iliac spine to the umbilicus (McBurney’s Point), where people with appendicitis describe the pain
    • Arterial supply to appendix: not high yield
  • Colon:
    • Ascending and descending sequences are retroperitoneal
    • Transverse and sigmoid segments are intraperitoneal.
    • Left colic flexure between ascending and transverse colon is inferior to the spleen
    • Right colic flexure between transverse and descending colon is just inferior lobe of the liver
    • Immediately lateral to the ascending and descending colons are the right and left paracolic gutters
      • Clinical Note: Because major vessels and lymphatics are on the medial to the ascending/descending colon, a relatively blood-free mobilization of the ascending/descending colon is possible by cutting the peritoneum along these lateral paracolic gutters.
    • Blood supply to ascending colon (ileocolic and superior mesenteric):
      • Colic branch of iloecolic artery
      • Anterior cecal artery from the ileocolic artery
      • Posterior cecal artery from the ileocolic artery
      • Right colic artery from the superior mesenteric artery
    • Blood supply to the transverse colon: (superior mesenteric artery)
      • Right colic artery from the superior mesenteric artery
      • Middle colic artery from the superior mesenteric artery
      • Left colic artery from the superior mesenteric artery
    • Blood supply to the descending colon: (inferior mesenteric artery)
      • Left colic artery from inferior mesenteric artery
    • Blood supply to the sigmoid colon: (inferior mesenteric artery)
      • Sigmoidal arteries from inferior mesenteric artery
    • Rectum and Anal Canal
      • Rectum is a retroperitoneal structure
      • The anal canal is a continuation of the large intestine inferior to the rectum
      • Arterial supply: low yield
    • Clinical note: Malrotation is incomplete rotation and fixation of the midgut after it has passed from the umbilical sac and returned to the abdominal coelom
      • If the duodenojejunal flexure or the cecum does not end up in its usual site, the origin of the small bowel mesentery shortens, which permits twisting of the small bowel around the axis of the superior mesenteric artery. Twisting of the bowel is termed volvulus, which may lead to lead to reduction of blood flow and infarction.
    • Clinical Note: Bowel obstruction
      • Mechanical obstruction is caused by intraluminal, mural or extrinsic mass which can be secondary to a foreign body, obstructing tumor in the wall or extrinsic compression from an adhesion.
      • Functional obstruction is usually due to an inability of the bowel to perstalse and is mostly likely caused by a postsrugcial state due to excessive intraoperative bowel handling.