Trigonum anale

Trigonum anale is from a topographical point of view, part of the pelvic outlet (exitus pelvis). It extends bilaterally from tubera ischiadica and converges to os sacrum and to os coccygis. The front part of the pelvic outlet is formed by the trigonum urogenitale.

Boundaries
The front border is formed by the course of diaphragma pelvis, posterolateral borders are formed by the course of  'lig. sacrotuberale' on both sides.

Construction
From the surface to the depth, the first layer is the weak skin, movable relative to the base (at the anus of the eyelash). The skin is covered with hair and a pigmented strip runs ventrally from the anus - raphe perinei, the skin also contains small glands, glandulae circumanales, which are of the aprocrine type.

The subcutaneous tissue is without fascia and the high layer of fat continues in depth.

Between the anus, the diaphragma pelvis medially and the lateral wall of the pelvis, the fossa ischiorectalis is formed, which ventrally in the trig. urogenitale forms the reessus pubicus.

Around the anus is a 2 cm thick sphincter m. sphincter ani externus, the dorsal part of which attaches to the coccyx through the fibrous septum anococcygeum.

Ventrally from the sphincter, a muscular-ligamentous strip extends deep into the centrum tendineum perinei, which is the fixed point of the entire perineum. Many structures attach to the centrum tendineum, examples of which are the fascia of the pelvic floor, the fascia of the urogenital diaphragm, and the fibromuscular bands of the walls of the pelvic organs.

In the sagittal section, it is wedge-shaped with the tip oriented upwards, continuing as the septum rectovaginale/rectoprostaticum.

Content

 * fossa ischioanalis (seu ischiorectalis)
 * lig. sacrotuberale
 * lig. sacrospinale
 * n. pudendus
 * canalis analis
 * muscles (also include m. gluteus maximus, m. obturatorius internus, m. levator ani, m. coccygeus)

Related articles

 * Pelvis