Abdominal Vasculature and Viscera

Anatomy of Abdominal Vasculature and Viscera


Intraperitoneal vs. Retroperitoneal Structures

*Note from an M2: You must memorize these two lists, unfortunately. 

  • Intraperitoneal Organs:

    • Stomach
    • Liver
    • Spleen
    • Part of the duodenum
    • Jejunum
    • Ileum
    • Transverse and sigmoid colon

  • Retroperitoneal Structures:

    • Suprarenal glands
    • Aorta and IVC
    • Duodenum (2nd-4th parts)
    • Pancreas (except tail)
    • Ureters
    • Ascending and descending colon
    • Kidneys
    • Esophagus
    • Rectum (partial)

Esophagus

*Note from an M2: This isn't high yield. I would just know roughly where the aorta is, where the arteries are in relation to each other, which arteries are impacted if an organ anterior to it is inflamed etc... 

  • Constrictions:
    • Cervical constriction
    • Thoracic (aortobronchial) constriction
    • Diaphragmatic constriction
  • Anatomical Features:
    • The transition from skeletal to smooth muscle in the middle third
    • Gastroesophageal junction transition of mucosal lining
    • Anterior and posterior vagal trunks accompany the esophagus


    Stomach

    Anatomical Features

    • Regions:
      • Cardiac
      • Fundic
      • Body
      • Pyloric
    • Curvatures:
      • Greater curvature
      • Lesser curvature
    • Notable Structures:
      • Cardiac notch
      • Angular incisure
      • Pyloric sphincter
      • Gastric folds (rugae)
    • Muscle Layers:
      • Inner circular layer
      • Outer longitudinal layer


      Small Intestine

      Sections

      1. Duodenum:

        • Duodenojejunal junction
        • First few centimeters are smooth muscle
        • Major and minor duodenal papillae

      1. Jejunum:

        • Occupies the upper left quadrant
        • Less fat in mesentery
        • Long, straight arteries and veins
        • Abundant circular folds

      1. Ileum:

        • Occupies the lower right quadrant
        • More fat in mesentery
        • Shorter, straight arteries and veins
        • Fewer circular folds

      Functional Aspects

      • Absorption of nutrients and water
      • Total length is approximately 6 to 7 meters (22 feet)

      Large Intestine

      Features

      • Larger diameter compared to the small intestine
      • Retroperitoneal and Intraperitoneal Parts:
        • Sacculation (haustra)
        • Omental appendices (fat accumulations)
        • Three longitudinal muscle bands (tenia coli)

      Specific Regions

      • Ileocecal Region:
        • Contains the ileocecal junction
        • Vermiform appendix with its own arterial supply (appendicular artery)

        *Note from an M2: Know the arterial supply of different parts of the colon. They love anastomosis questions. 


        • Paracolic Gutters:
          • Lateral to ascending and descending colon
          • Blood-free mobilization possible by cutting peritoneum along these gutters


        Blood Supply of Abdominal Viscera

        Major Arteries

        1. Celiac Trunk (Foregut):

          • Supplies abdominal esophagus, stomach, duodenum (up to major duodenal papilla), liver, pancreas, gallbladder, and spleen

        2. Superior Mesenteric Artery (Midgut):

          • Supplies duodenum (part), jejunum, ileum, cecum, appendix, ascending colon, and transverse colon

        3. Inferior Mesenteric Artery (Hindgut):

          • Supplies descending colon, sigmoid colon, rectum, and upper part of the anal canal

          Note from an M2: You will need to know the blood supply to different parts of the digestive system.


          Anastomoses

          • Marginal Artery:
            • Formed by anastomoses between right, middle, and left colic arteries
            • Provides collateral circulation in case of inferior mesenteric artery stenosis


          Nerve Supply of Abdominal Viscera

          • Autonomic Nerve Fibers:
            • Course with arteries
            • Include both sympathetic and parasympathetic fibers


          Specific Plexuses

          • Aortic Plexus
          • Superior Hypogastric Plexus
          • Hypogastric Nerve
          • Pelvic Splanchnic Nerves
          • Inferior Hypogastric Plexus


          Clinical Considerations

          • Duodenal Ulcers:
            • Often occur in the superior part (duodenal cap)
            • Posterior ulcers may erode onto major arteries, causing severe bleeding