The conjoint longitudinal muscle is a muscle layer in the wall of the

anal canal The anal canal is the part that connects the rectum to the anus, located below the level of the pelvic diaphragm. It is located within the anal triangle of the perineum, between the right and left ischioanal fossa. As the final functional s ...

between the

internal anal sphincter The internal anal sphincter, IAS, or sphincter ani internus is a ring of smooth muscle that surrounds about 2.5–4.0 cm of the anal canal. It is about 5 mm thick, and is formed by an aggregation of the smooth (involuntary) circular musc ...

(deep to CLM) and

external anal sphincter The external anal sphincter (or sphincter ani externus) is an oval tube of skeletal muscle fibers. Distally, it is adherent to the skin surrounding the margin of the anus. It exhibits a resting state of tonical contraction and also contracts duri ...

(superficial to CLM). It is continuous proximally with the longitudinal (outer) smooth muscle layer of the rectum. It receives autonomic innervation in common with the

Anatomy

Distally, the muscle detaches and extends in three directions. The projections of the muscle represent pathways for the spread of infections.

Development

The CLM is especially prominent in the foetus, but is gradually replaced by connective tissue with age.

Function

Contraction of the CLM shortens and widens the anal canal, and everts the anal orifice.

References

External links

* () {{Authority control Perineum Anus