The Abdomen and Pelvis

The fasciae and muscles of theabdominal wall

Fasciae of the abdominal wall• forms a superficial fatty layer (of Camper) and a deeper fibrous layer (of Scarpa). The fatty

layer is continuous with the superficial fat of the rest of the body, but the fibrous layer blends with the deep fascia of the upper thigh, extends into the penis and scrotum (or labia majora) and into the perineum as Colles’ fascia.

The muscles of the anterior abdominal wall

• The rectus abdominis

The muscles of the anterior abdominal wall

• obliquus externus abdominis

The muscles of the anterior abdominal wall

• obliquus internus abdominis

The muscles of the anterior abdominal wall

• transversus abdominis

The anatomy of abdominal incisions

• Midline incisionParamedian incisionThe transrectus incisionSubcostal incisionThe muscle split or gridiron approach to the appendixMcBurney’s point

The inguinal canal • This canal represents the oblique passage taken through the lower abdominal wall by

the testis and cord (the round ligament in the female). Questions on the anatomy of this region are probably asked more often than any other in examinations because of its importance in the diagnosis and treatment of hernias. • The canal is 1.5in (4cm) long. It passes downwards and medially from the internal to

the external inguinal rings and lies parallel to, and immediately above, the inguinal ligament.

Relations

• Anteriorly – the skin, superficial fascia and the external oblique aponeurosis cover the full length of the canal; the internal oblique covers its lateral one-third.• Posteriorly – the conjoint tendon forms the posterior wall of the canal medially, the transversalis fascia laterally. (The conjoint tendon represents the fused common insertion of the internal oblique and transversus into the pubic crest and pectineal line. The transversalis fascia is the name given to the extraperitoneal fascia which, in the lower abdomen, is much thickened.

• The internal (or deep) ring represents the point at which the spermatic cord pushes through the transversalis fascia, dragging from it a covering which forms the internal spermatic fascia. This ring is demarcated medially by the inferior epigastric vessels passing upwards from the external iliac artery and vein.

• The external (or superficial) ring is a V-shaped defect in the externaloblique aponeurosis and lies immediately above and medial to the pubictubercle. As the cord traverses this opening, it carries the external spermatic fascia from the ring’s margins.

• In the male, the inguinal canal transmits the spermatic cord and the ilioinguinal nerve.

• In the female, the canal is a much smaller affair – it is still made up of the three layers of fascia described below, but transmits only the round ligament of the uterus together with the ilio-inguinal nerve.

• The spermatic cord comprises: • three layers of fascia – the external spermatic, from the external oblique aponeurosis; the cremasteric, from the internal oblique aponeurosis (containing muscle fibres termed the cremaster muscle); the internal spermatic,

The Gastrointestinal Tract

• Abdominal viscera: • 1, liver; 2, oesophagus; • 3, stomach; 4, spleen; • 5, gallbladder; • 6, first part of duodenum; • 7, head of pancreas; • 8, duodenojejunal flexure; 9,

transverse colon;10, ascending colon;

11, descending colon; 12, sigmoid colon;

13, terminal ileum; 14, appendix

The stomach

• The stomach is roughly J-shaped, although its size and shape vary considerably. It tends to be high and transverse in the obese short subject and to be elongated in the asthenic individual; even in the same person, its shape depends on whether it is full or empty, on the position of the body and on the phase of respiration. The stomach has two surfaces – the anterior and posterior; two curvatures – the greater and lesser; and two orifices – the cardia and pylorus

• The stomach projects to the left, above the level of the cardiac orifice (or cardia), to form the dome-like gastric fundus. Along the lesser curve is a distinct notch, the incisura angularis. Between the cardiac orifice and the incisura is the body of the stomach, while the area between the incisura and the pylorus is the pyloric antrum. The junction of the pylorus with the duodenum is marked by a constriction externally and also by a constant vein that crosses it, the vein of Mayo.

• It is the body of the stomach that bears the HCl-secreting parietal cells.The antrum secretes the enzyme gastrin and its secretion is alkaline.The thickened pyloric sphincter is easily felt and surrounds the lumen ofthe pyloric canal. The pyloric sphincter is an anatomical structure as wellas a physiological mechanism. The cardia, on the other hand, althoughcompetent (gastric contents do not flow out of your mouth if you standon your head), is not demarcated by a distinct anatomical sphincter. Theexact nature of the cardiac sphincter action is still not fully understood,but the following mechanisms have been suggested, each supported bysome experimental and clinical evidence.

•Relations• Anteriorly – the abdominal wall, the left costal margin, the diaphragmand the left lobe of the liver.• Posteriorly – the lesser sac, which separates the stomach from the pancreas, transverse mesocolon, left kidney, left suprarenal, the spleen and the splenic artery.• Superiorly – the left dome of the diaphragm. The lesser omentum is attached along the lesser curvature of the stomach; the greater omentum along the greater curvature. These omenta contain the vascular and lymphatic supply of the stomach.

• stomach can be divided into three drainage zones • Area I – the superior two-thirds of the stomach drain along the left andright gastric vessels to the aortic nodes.• Area II – the right two-thirds of the inferior one-third of the stomach drain along

the right gastro-epiploic vessels to the subpyloric nodes and thence to the aortic nodes.• Area III – the left one-third of the greater curvature of the stomach drains along the short gastric and splenic vessels lying in the gastrosplenic and splenorenal ligaments, then, via the suprapancreatic nodes, to the aortic group.

CLINICAL FEATURES

• A posterior gastric ulcer or cancer may erode the pancreas, giving pain referred to the back. Ulceration into the splenic artery – a direct posterior relation – may cause torrential haemorrhage.There may be adhesions across the lesser sac that bring the transverse mesocolon into intimate relationship with the stomach or greater omentum. In these circumstances, the middle colic vessels are in danger of damage during mobilization of the stomach for gastrectomy.

The duodenum• The duodenum curves in a C around the head of the pancreas and is

10in (25cm) long. At its origin from the pylorus it is completely covered with peritoneum for approximately 1 in (2.5cm), but then becomes a retroperitoneal organ, only partially covered by serous membrane.

• Relations (Figs 55, 56)

• For descriptive purposes, the duodenum is divided into four sections.

• The first part (2 in (5 cm)) ascends from the gastroduodenal junction, overlapped by the liver and gall bladder. Immediately posterior to it lie the portal vein, common bile duct and gastroduodenal artery, which separate it from the inferior vena cava.

• The second part (3in (7.5cm)) descends in a curve around the head of the pancreas. It is crossed by the transverse colon and lies on the right kidney and ureter. Halfway along, its posteromedial aspect enters the common opening of the bile duct and the main pancreatic duct (of Wirsung) onto an eminence called the duodenal papilla. This common opening is guarded by the sphincter of Oddi. The accessory pancreatic duct (of Santorini) opens into the duodenum a little above the papilla.

• The third part (4in (10cm)) runs transversely to the left, crossing the

• inferior vena cava, the aorta and the third lumbar vertebra. It is itself crossed anteriorly by the root of the mesentery and the superior mesenteric

• vessels. Its upper border hugs the pancreatic head.

• The fourth part (1in (2.5 cm)) ascends upwards and to the left to end at

• the duodenojejunal junction. It is surprisingly easy for the surgeon to

• confuse this with the ileocaecal junction, a mistake which may be disastrous.

• CLINICAL FEATURES1 The first part of the duodenum is overlapped by the liver and gallbladder, either of which may adhere to, or even be eroded by, a duodenalulcer. Moreover, a gallstone may be extruded from the fundus of a chronically inflamed gall bladder into the duodenum. The gallstone may thenimpact in the lower ileum as it traverses the gut to produce intestinalobstruction (gallstone ileus).2 The pancreas, as the duodenum’s most intimate relation, is readilyinvaded by a posterior duodenal ulcer. This should be suspected if thepatient’s pain radiates into the dorsolumbar region. Erosion of the gastroduodenal artery by such an ulcer results in severe haemorrhage.3 Extensive dissection of a duodenum, scarred by severe ulceration, maydamage the common bile duct, which passes behind the first part of theduodenum approximately 1in (2.5cm) from the pylorus.4 The hepatic flexure of the colon crosses the second part of the duodenumand the latter may be damaged during a right hemicolectomy. Similarly,the right kidney lies directly behind this part of the duodenum, whichmay be injured in performing a right nephrectomy.

5 Radiology of the duodenum. Within a few minutes of swallowing a barium meal, the first part of the duodenum becomes visible as a triangular The gastrointestinal tract shadow termed the duodenal cap. Every few seconds the duodenum contracts, emptying this cap, which promptly proceeds to fill again. It is in this region that the great majority of duodenal ulcers occur; an actual ulcer crater may be visualized, filled with barium, or deformity of the cap, produced by scar tissue, may be evident. The rest of the duodenum can also be seen, the shadow being floccular owing to the rugose arrangement of the mucosa.6 Mobilization of the duodenum, together with the head of the pancreas and termination of the common bile duct, is performed by incising the peritoneum lateral to the second part of the duodenum and developing the avascular plane between these structures and the posterior abdominal wall – Kocher’s manoeuvre.

Small intestine

Large intestine

• The large intestine is subdivided, for descriptive purposes, into:• caecum with the appendix vermiformis;• ascending colon (5–8in (12–20 cm));• hepatic flexure;• transverse colon (18in (45cm));• splenic flexure;• descending colon (9–12 in (22–30cm));• sigmoid colon (5–30in (12–76 cm), average 15in (38cm));• rectum (5 in (12 cm));• anal canal (1.5in (4cm)).

The appendix

The rectum