Abdominal wall and Mesenteries

18 March 2008

Muscles of the Abdominal Wall

• External abdominal oblique

– Fibers inclined medially from superior to inferior

– Overlaps onto ribcage and interdigitates with serratus

• Internal abdominal oblique

– Fibers inclined laterally

• Transversus abdominis

– Fibers oriented transversely

• Rectus abdominis

– Enclosed in an connective tissue sheath that acts as an aponeurosis for the lateral muscles

– Rectus sheath meets in midline at linea alba

– Muscle segmented by tendinous intersections

see Netter, 1997, pls. 232-237; 2003, pls. 241-246; 2006, pls. 249-255

Clemente, 1997, Fig. 253, 255

Terminology

• Mesentery - a fold of membrane connecting an organ to the body wall

• Meso - prefix denoting a mesentery

• Omentum - a fold of peritoneum extending from the stomach to adjacent organs

• Ligament - a band of connective tissue that connects bones or supports viscera

Cross section of early-stage embryo through developing abdominal cavity

Gut is suspended from dorsal body wall by the dorsal mesentery. The mesentery is the access for blood and nerve supply to the gut.

Note that the lesser omentum forms the anterior wall of the lesser sac (omental bursa).

Rosse & Gaddum-Rosse, 1997; Fig. 23-19; see Moore & Dalley 2006, Figs. 2.19, 2.21, 2.21, 2.23

Development of the gut and mesenteries

• Dorsal mesenteries develop as a continuous membrane from the greater curvature of stomach,

small intestine and colon.

• This will become the greater omentum and mesentery of jejunum and ileum

• A ventral mesentery develops from the lesser curvature of the stomach to the ventral

abdominal wall

• The liver develops within the ventral mesentery, separating the falciform ligament and the

lesser omentum

– Lesser omentum becomes the hepatogastric and hepatoduodenal ligaments

• Liver expands so much that it out-grows the mesenteries and develops bare areas in contact

with the diaphragm.

• These bare areas form the coronary ligaments of the liver.

Sadler, 2000, Langman’s Medical Embryology. Fig. 13-13, 13-14, 13-24

Rosse & Gaddum-Rosse, 1997; Figs. 23-19, 23-24

First peek into the abdomen

Flaciform ligament

Liver

Stomach

Greater omentum

Netter 1997, pl. 252; 2003, pl. 261; 2006, pl. 269

Greater omentum, reflected superiorly

Greater omentum

Transverse colon

Transverse mesocolon

Ascending colon

Jejunum

Ileum

Netter 1997, pl. 252; 2003, pl. 261; 2006, pl. 269

Lesser omentum

Hepatogastric ligament

Hepatoduodenal ligament

Epiploic foramen

This is the entrance into the omental bursa.

The pancreas is on the posterior wall of the omental bursa.

Netter 1997, plate 256, 258; 2003, pl. 264; 2006, pl. 273

Rosse & Gaddum-Rosse, 1997; Fig. 23-19; Fig. 23-24. see Moore & Dalley 2006, Fig. 2.21

Inguinal Canal

•Passage through the abdominal wall for the spermatic cord (or round ligament of uterus in

females)

•Two inguinal rings joined by a passage

-Superficial ring - opening in external abdominal oblique aponeurosis medial to inferior epigastric vessels

-Deep ring - opening under inferior edge of transversus abdominis lateral to inferior epigastric vessels

•Layers of abdominal wall contribute layers to spermatic cord

Netter 1997, plate 242

see Netter 2003, pl. 243, 249; 2006, pl. 259, 260

Walls of Inguinal Canal

•Anterior - external abdominal oblique

•Inferior wall - inguinal ligament

-Formed by external abdominal oblique

•Posterior wall - conjoint tendon

-Fusion of internal abdominal oblique and transversus abdominis

•Roof - fibers of internal abdominal oblique & transversus abdominis

Moore & Dalley 2006, Fig 2.12

Internal Surface of Abdominal Wall

Falciform ligament

Ligamentum teres hepatis

Median umbilical fold

Medial umbilical fold

Lateral umbilical fold

Inferior epigastric a. & v.

Deep inguinal ring

Ductus deferens

Netter 1997, pl. 236; 2003, pl. 245; 2006, pl. 253

Abdominal Wall & layers of Spermatic Cord

Moore & Dalley, 2006, pp. 216, 221, 224

•External ab. Oblique = Ext. spermatic fascia

•*Internal ab. Oblique = Cremasteric muscle

•*Transversus abdominis -- not represented

• (fusion of these two* makes - Conjoint tendon)

•Transversalis fascia = Internal spermatic fascia

References

Clemente, C.D. 1997, Anatomy: A Regional Atlas of the Human Body. 4th Ed. Williams & Wilkins.

Rosse, C and P. Gaddum-Rosse, 1997. Holinshead's Textbook of Anatomy, 5th Ed. Lippincott-Raven.

Sadler, T.W., 2000. Langman's Medical Embryology, 8th Ed. Lippincott, Williams & Wilkins.