The arterial supply to the descending colon (Fig. 4.90) includes the left colic artery from the inferior mesenteric artery.
The arterial supply to the sigmoid colon (Fig. 4.90) includes sigmoidal arteries from the inferior mesenteric artery.
Anastomotic connections between arteries supplying the colon can result in a marginal artery that courses along the ascending, transverse, and descending parts of the large bowel (Fig. 4.90).
Extending from the sigmoid colon is the rectum (Fig. 4.91). The rectosigmoid junction is usually described as being at the level of vertebra SIII or at the end of the sigmoid mesocolon because the rectum is a retroperitoneal structure.
The anal canal is the continuation of the large intestine inferior to the rectum.
The arterial supply to the rectum and anal canal (Fig. 4.92) includes: the superior rectal artery from the inferior mesenteric artery, the middle rectal artery from the internal iliac artery, and the inferior rectal artery from the internal pudendal artery (from the internal iliac artery).
The liver is the largest visceral organ in the body and is primarily in the right hypochondrium and epigastric region, extending into the left hypochondrium (or in the right upper quadrant, extending into the left upper quadrant) (Fig. 4.101).
Surfaces of the liver include: a diaphragmatic surface in the anterior, superior, and posterior directions; and a visceral surface in the inferior direction (Fig. 4.102).
The diaphragmatic surface of the liver, which is smooth and domed, lies against the inferior surface of the diaphragm (Fig. 4.103). Associated with it are the subphrenic and hepatorenal recesses (Fig. 4.102):
The subphrenic recess separates the diaphragmatic surface of the liver from the diaphragm and is divided into right and left areas by the falciform ligament, a structure derived from the ventral mesentery in the embryo.
The hepatorenal recess is a part of the peritoneal cavity on the right side between the liver and the right kidney and right suprarenal gland.
The subphrenic and hepatorenal recesses are continuous anteriorly.
The visceral surface of the liver is covered with visceral peritoneum except in the fossa for the gallbladder and at the porta hepatis (gateway to the liver; Fig. 4.104), and structures related to it include the following (Fig. 4.105): esophagus, right anterior part of the stomach, superior part of the duodenum, lesser omentum, gallbladder, right colic flexure, right transverse colon, right kidney, and right suprarenal gland.
The porta hepatis serves as the point of entry into the liver for the hepatic arteries and the portal vein, and the exit point for the hepatic ducts (Fig. 4.104).
The liver is attached to the anterior abdominal wall by the falciform ligament and, except for a small area of the liver against the diaphragm (the bare area), the liver is almost completely surrounded by visceral peritoneum (Fig. 4.105). Additional folds of peritoneum connect the liver to the stomach (hepatogastric ligament), the duodenum (hepatoduodenal ligament), and the diaphragm (right and left triangular ligaments and anterior and posterior coronary ligaments).
The bare area of the liver is a part of the liver on the diaphragmatic surface where there is no intervening peritoneum between the liver and the diaphragm (Fig. 4.105):
The anterior boundary of the bare area is indicated by a reflection of peritoneum—the anterior coronary ligament.
The posterior boundary of the bare area is indicated by a reflection of peritoneum—the posterior coronary ligament.