Inguinal canal-anatomy|contents & Hernias
Inguinal canal-anatomy|contents & hernias. This is an oblique intermuscular passage in the lower
part of the anterior abdominal wall, it is situated just above the medial half of the inguinal ligament.
Length and direction; It is about 4 cm (1.5 inches) long and is directed downwards, forwards and medially.
The inguinal canal enlarge from the deep inguinal
rings to the superficial inguinal ring. The deep inguinal ring is an oval opening in fascia
transversalis, situated 1.2 cm above the midinguinal
point, and lateral to the stem of the inferior epigastric artery.
The superficial inguinal ring is a triangular gap in the external oblique aponeurosis. It is shaped like an obtuse angled triangle. The base of the triangle is formed by the pubic crest. The two sides of the triangle form the lateral or lower and the medial or upper margins of the opening. It is 2.5 cm in length and 1.2 cm in width at the base. These margins are referred to as crura. At and beyond the apex of the triangle, the two crura are united by intercrural fibres.
Inguinal canal-anatomy|contents & Hernias
Boundaries of Inguinal canal
The Anterior wall
I. ln its whole extent:
b. Superficial fascia
c. External oblique aponeurosis.
2. In its lateral one-third: The fleshy fibres of the internal oblique muscle
The posterior wall
- In its whole extent:
a. The fascia transversalis
b. The extraperitoneal tissue
c. The parietal peritoneum.
- In its medial two-thirds:
a. The conjoint tendon
b. At itss medial end by the reflected part of the
- It is formed by the arched fibres of the internal oblique and transversus abdominis muscles.
It is formed by the grooved upper surface of the inguinal ligament & at the medial end by the lacunar ligament.
- Sex difference
The inguinal canal is shorter in females than in males.
Structures passing through inguinal canal
1. The spermatic cord in males, or the round ligament of the uterus in females , enters the inguinal canal by the deep inguinal ring and passes out through the superficial inguinal ring.
2. The ilioinguinal nerve enters in canal through the
interval between the external and internal oblique
muscles and passes out through the superficial
CONSTITUENTS OF THE SPERMATIC CORD
These are as follows.
1. The ductus deferens.
2. The testicular and cremasteric arteries, and the artery of the ductus deferens.
3. The pampiniform plexus of veins.
4. Lymph vessels from the testis.
5. The ilioinguinal nerve, genital branch of the
genitofemoral nerve, and the plexus of sympathetic
nerves around the artery to the ductus deferens and
visceral afferent nerve fibres.
6. Remains of the processus vaginalis.
COVERINGS OF SPERMATIC CORD
From within outwards, these are as follows.
- The internal spermatic fascia, derived from the fascia transversalis and it covers the cord in its whole extent.
2. The cremasteric fascia is made of the muscle loops constituting the cremaster muscle, and the intervening areolar tissue. It is derived from the internal oblique and transversus abdominis muscles, and therefore covers the cord below the level of these muscles
3. The external spermatic fascia is gain from the
external oblique aponeurosis. It covers the cord
below the superficial inguinal ring.
Mechanism of Inguinal canal
The presence of the inguinal canal is a cause of weakness in the lower part of the anterior abdominal wall. This weakness is compensated by the following factors.
1. Obliquity of the inguinal canal: The two inguinal rings do not lie opposite each other. Therefore, when the intra-abdominal pressure increases the anterior and posterior walls of the canal are approximated, thus obliterating the passage. This is also called as the flap valve mechanism.
2. The superficial inguinal ring is guarded from behind by the conjoint tendon and by the reflected part of the inguinal ligament.
3. The deep inguinal ring is guarded from the front by the fleshy fibres of the internal oblique.
4. Shutter mechanism of the internal oblique: This muscle has a triple relation to the inguinal canal. It forms the dorsal wall, the roof, and the ventral wall of the canal. When it contracts the roof is approximated to the floor, like a shutter. The arching fibres of the transversus also take part in the shutter mechanism.
5. Contraction of the cremaster provides the spermatic cord to plug the superficial inguinal ring.
6. Contraction of the external oblique results in
approximation of the 2 crura of the superficial
inguinal ring (slit valve mechanism). The integrity of
the superficial inguinal ring is increased by
the intercrural fibres.
7. Hormones play role in maintaining the tone of the inguinal musculature.
Whenever, there is a rise in intra-abdominal pressure as in coughing, sneezing, lifting heavy weights all these mechanisms come into play, so that the inguinal canal is obliterated, its openings are closed, and herniation of abdominal viscera is prevented.
Development of Inguinal canal
Inguinal canal represents the passage of gubernaculum through the abdominal wall. It extends from the caudal end of the developing gonad (in lumbar region) to the labioscrotal swelling.In early life, the canal is very short.
As the pelvis increases in width, the deep inguinal ring is shifted laterally and the adult dimensions of the canal are attained.
Hernia is a protrusion of any of the abdominal
contents through any of its walls. This is called
external hernia. At times the intestine or omentum
protrudes into the “no entry” zone within the
abdominal cavity itself. The condition is called as
Hernia consists of a sac, contents and coverings.
Sac is the protrusion of the peritoneum. It comprises
a neck, the narrowed part; and a body, the bigger
Contents are mostly the long motile, keen to move
out coils of small intestine or omentum or any other
Coverings are the layers of abdominal wall which
are covering the hernial sac.
In the beginning, the loop of intestine
herniates out but comes back to the abdomen. At
times, the loop goes out but does not return, leading
to irreducible hernia.
The loop may get narrowed in part,
so that contents of the loop cannot move forwards,
leading to obstruction.
When the arterial supply is blocked,
the loop gets necrosed.
Types of abdominal hernia
• Protrusion of loop of intestine within a “no entry”
zone of peritoneum.
• Internal hernia mostly occurs in epiploic foramen
or opening into the lesser sac or foramen of
Winslow. The loop mostly gets strangulated. It
may also occur in the “paraduodenal fossae”.
• Divarication of recti