Anatomic Considerations

The colon has a complete outer longitudinal muscle coat, less than half the thickness of the inner circular muscle.2,6 The outer longitudinal layer is thickened by three bands of muscle, the taeniae coli, each of 0.5-1.0

cm in width. They are most distinct in the ascending and transverse colon. In the lower descending and sig-moid colon, they increase at the expense of the rest of the outer longitudinal muscle coat and at the level of the rectum become merged into broad diffuse bands (Fig. 15-4).

Figure 15-5a shows that each of the taeniae is named according to its topographic situation relative to the transverse colon:

1. The taenia mesocolica (TM) is situated on the pos-terosuperior surface of the transverse colon at the line of attachment of the transverse mesocolon.

2. The taenia omentalis (TO) runs along the antero-superior surface of the transverse colon and is in relation to the line of attachment of the greater omentum extending inferiorly and of the gastrocolic ligament above.

3. The taenia libera (TL), so called because it is free and not related to any mesenteric or omental attach-

Taenia Libera Coli Picture

Fig. 15—4. General anatomy of the colon.

(From William and Bannister,7)

Fig. 15—4. General anatomy of the colon.

(From William and Bannister,7)

Taenia Omentalis Taenia Mesocolon

Fig. 15—5. Position and relationships of the taeniae and haustra of the colon.

(a) Sagittal diagram of transverse colon. P = pancreas; S = stomach.

(b) Horizontal diagram of ascending colon. The peritoneal reflections (dashed line) are shown in relation to the haustra. In the descending colon, the relationships are mirrorlike.

(Reproduced from Meyers et al.1)

Fig. 15—5. Position and relationships of the taeniae and haustra of the colon.

(a) Sagittal diagram of transverse colon. P = pancreas; S = stomach.

(b) Horizontal diagram of ascending colon. The peritoneal reflections (dashed line) are shown in relation to the haustra. In the descending colon, the relationships are mirrorlike.

(Reproduced from Meyers et al.1)

Taenia Libera

Fig. 15-6. (a) Colon in situ, colon uplifted, demonstrating continuity of the taenia libera from the ventral surface of the ascending and descending colon to the undersurface of the transverse colon.

(b) Position of the three taeniae in the uplifted transverse colon and the anterior rotation (indicated by arrow) that occurs when it assumes its normal position in the body. The taeniae and haustral rows then have the relationships shown in Fig. 10-5a. (Reproduced from Meyers et al.1)

Fig. 15-6. (a) Colon in situ, colon uplifted, demonstrating continuity of the taenia libera from the ventral surface of the ascending and descending colon to the undersurface of the transverse colon.

(b) Position of the three taeniae in the uplifted transverse colon and the anterior rotation (indicated by arrow) that occurs when it assumes its normal position in the body. The taeniae and haustral rows then have the relationships shown in Fig. 10-5a. (Reproduced from Meyers et al.1)

ment, is found on the posteroinferior aspect of the transverse colon.

These relationships of the taeniae are not maintained on the ascending and descending portions of the colon (Fig. 15-5b). Here the TM lies posteromedial, the TO posterolateral, and the TL anterior. The changing relationships of the taeniae are most simply understood if it is recalled that there is some anterior rotation of the transverse colon on its mesocolon relative to the flexures (Figs. 15-6 and 15-7). Nevertheless, continuity of the taeniae and thereby of the haustral rows can be easily traced.

Was this article helpful?

+1 0
Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

Get My Free Ebook


Post a comment