Inguinal triangle

Boundaries and shapes of the inguinal interval

Anatomically, the inguinal interval is bounded superiorly by the lower edges of the internal oblique and transverse abdominal muscles, and medially by the lateral margin of the rectus abdominis muscle. Topographically, it forms the posterior wall of the inguinal canal. Depending on the degree of development and attachment features of the abdominal muscles, two main shapes of this space are distinguished:

1. Slit-like oval shape. In this case, the internal oblique abdominal muscle is well developed and reliably covers the area of the deep inguinal ring. During physical exertion and muscle contraction, it compresses the spermatic cord in an arch-like manner. This is the so-called valve function, which provides reliable physiological protection against the formation of hernia protrusions.
2. Triangular shape. Characterized by the fact that the muscle bundles of the internal oblique muscle do not form a protective arch, but run horizontally straight toward the rectus sheath. As a result, the inguinal interval becomes high, acquires a triangular shape, and the posterior wall of the inguinal canal remains uncovered by muscle tissue for a considerable extent. The valve function is completely absent, which creates ideal anatomical prerequisites for the development of inguinal hernias.

Classification of inguinal hernias by emergence site

The type of forming hernia strictly depends on which specific fossa on the inner surface of the anterior abdominal wall the hernial sac penetrates through:

• Indirect inguinal hernia. The hernia protrusion begins in the region of the lateral inguinal fossa, penetrates into the deep inguinal ring, and passes through the entire inguinal canal.
• Direct inguinal hernia. The mechanism of formation is associated with the medial inguinal fossa. The feature of this type is that the hernial sac protrudes directly through the superficial ring, bypassing the passage through the entire length of the inguinal canal.
• Internal oblique (supravesical) hernias. This is an extremely rare clinical form. It forms when intra-abdominal organs herniate into the supravesical fossa (fossa supravesicalis).

Descent of the testes (Descensus testiculorum)

Understanding the topography of the inguinal region is impossible without knowing embryogenesis. Testicular descent is a complex multi-stage process that can be divided into four key stages:

1. Testicular rudiment (III–IV month). Occurs in the retroperitoneal space of the lumbar region, in close proximity to the pronephros. During the same period, the scrotum and the vaginal process of the peritoneum (processus vaginalis) begin to form.
2. Displacement into the lesser pelvis (V month). The testis performs a caudal displacement, descending toward the area of the deep inguinal ring.
3. Passage through the inguinal canal (VII month). The organ overcomes the musculo-aponeurotic layers.
4. Descent into the scrotum (VIII–IX month). Final movement to its anatomical location.

The primary role in this process is played by the testicular gubernaculum (gubernaculum testis). At the lower pole of the developing testis, a special strip of embryonic connective tissue appears. It includes the lig. testis (which is a derivative of the outer layer of the processus vaginalis) and a fibrous cord running to the scrotum — lig. scroti. Fusing together, these two ligaments form the gubernaculum.

Formation of tunicae and congenital pathologies

During its advance through the inguinal canal, the testis moves extraperitoneally, strictly following the vaginal process of the peritoneum. As it descends, it literally 'wraps' the peritoneal layer around itself. Thus, the tunicae are formed:

• Visceral layer: tightly adheres to the tunica albuginea of the testis itself.
• Parietal layer: formed from the severed part of the processus vaginalis.

Under normal conditions, the communication between the vaginal process and the free peritoneal cavity completely obliterates. The serous cavity of the testis becomes absolutely airtight and closed.

Pathological anatomy: If physiological obliteration of the processus vaginalis does not occur for some reason, the scrotal cavity continues to communicate directly with the abdominal cavity. This anomaly creates direct conditions for the formation of a congenital inguinal-scrotal hernia. Important clinical note: even with an open vaginal process, a hernia may never form if the patient has a slit-like oval shape of the inguinal interval, and the deep ring is reliably protected by contracting muscles.

Briefly: answers to topical questions

What else to study on this topic

• Topography of the walls of the inguinal canal and its contents
• Surgical anatomy of the superficial and deep inguinal rings
• Detailed structure of the testis tunicae and spermatic cord
• Surgical approaches and repair principles for indirect and direct herniae

Other topics in the section "Topographic Anatomy of the Abdomen"

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