Overview
This lecture covers the anatomy of the inguinal canal, differences between types of hernias, and the anatomical features that prevent hernia formation.
Inguinal Canal Anatomy
- The inguinal canal is a 4 cm long fibromuscular canal in the lower anterior abdominal wall, above the medial half of the inguinal ligament.
- It is directed downward and medially, extending from the deep inguinal ring to the superficial inguinal ring.
- The deep inguinal ring is an opening in the transversalis fascia, located lateral to the inferior epigastric artery.
- The superficial inguinal ring is an opening in the external oblique aponeurosis, above the pubic tubercle.
Boundaries and Walls of the Inguinal Canal
- Anterior wall: external oblique aponeurosis (entire length) and internal oblique muscle fibers (lateral half).
- Posterior wall: transversalis fascia (entire length) and conjoined tendon (medial third).
- Floor: upper surface of the inguinal ligament.
- Roof: arched lower fibers of the internal oblique and transversus abdominis muscles.
Contents of the Inguinal Canal
- Contains the spermatic cord in males, the round ligament of the uterus in females, and the ilio-inguinal nerve.
Types of Inguinal Hernias
- Oblique (indirect) inguinal hernia passes through the deep ring, canal, and superficial ring, and can enter the scrotum; it is lateral to the inferior epigastric artery.
- Direct inguinal hernia passes through the inguinal triangle, is medial to the inferior epigastric artery, and does not descend into the scrotum.
Inguinal Triangle
- Bounded medially by rectus abdominis, laterally by the inferior epigastric artery, and the base by the inguinal ligament.
- Provides a potential passage for direct inguinal hernia.
Comparison with Femoral Hernia
- Inguinal hernia is located above the pubic tubercle and inguinal ligament.
- Femoral hernia is located below the pubic tubercle and inguinal ligament.
Mechanics Preventing Hernia Formation
- Oblique direction of the canal.
- Distance between deep and superficial rings.
- Superficial ring is reinforced by the conjoined tendon (posterior wall).
- Deep ring is reinforced by the internal oblique muscle (anterior wall).
- Contraction of abdominal muscles compresses the canal's roof against the floor, closing the canal.
Key Terms & Definitions
- Inguinal Canal — fibromuscular passage in the lower anterior abdominal wall.
- Inguinal Ligament — ligament forming the lower border of the inguinal region.
- Deep Inguinal Ring — opening in transversalis fascia, entry to canal.
- Superficial Inguinal Ring — opening in external oblique aponeurosis, canal exit.
- Oblique (Indirect) Inguinal Hernia — hernia passing through the canal, lateral to the inferior epigastric artery.
- Direct Inguinal Hernia — hernia passing through the inguinal triangle, medial to the inferior epigastric artery.
- Conjoined Tendon — fusion of the internal oblique and transversus abdominis aponeuroses.
Action Items / Next Steps
- Review the anatomical locations and relations for the inguinal canal and hernia types.
- Study boundaries and contents of the inguinal triangle for clinical significance.