The inguinal canal is a passage in the lower anterior abdominal wall that extends from the deep inguinal ring to the superficial inguinal ring. It is around 4cm long and directed downward and medially. The walls of the canal include the external and internal oblique muscles. The spermatic cord in males and round ligament of the uterus in females pass through the canal. The posterior wall is weakened at the deep inguinal ring, making it a site for indirect inguinal hernias. Direct hernias occur laterally through Hesselbach's triangle. The internal anatomy and muscle actions help prevent hernias by reinforcing the rings during increased abdominal pressure.
2. Inguinal Canal
This is an oblique intermuscular
passage in the lower part of the
anterior abdominal wall ,
Situated just above the medial
half of the inguinal ligament
4. Length & direction
It is about 4cm(1.5 inches) long, and is
directed downwards, forwards and
medially
5. The inguinal canal extends from
the deep inguinal ring to the
superficial inguinal ring
6. A Box?
Floor
Lateral
Medial
Imagine the right side inguinal canal viewed from the front as a
box with anterior & posterior walls, a roof & floor. The arrow
indicates that structures can run through it from lateral to medial
– e.g. in males it transmits the spermatic cord, and in females, the
round ligament of the uterus.
7. Deep inguinal ring
An oval opening in the fascia
transversalis situated 1.2 cm above the
midinguinal point, and immediately
lateral to the stem of the inferior
epigastric artery
8. Inguinal canal
Deep inguinal ring
Floor
Lateral
Medial
Here are the posterior wall, which has the DEEP inguinal ring
situated laterally, and the floor. (Roof and anterior wall
removed).
9. 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 from the lateral or lower and the medial
or upper margins of the opening. It is 2.5 cm long and
1.2 cm broad at the base these margins are referred as
crura. At and beyond the apex of the triangle 2
crura are united by intercrural fibers
10. Inguinal canal
Superficial inguinal ring Floor
Lateral
Medial
Here are the anterior wall (which has the SUPERFICIAL
inguinal ring situated medially), and the roof.
11.
12. BOUNDARIES OF INGUINAL
CANAL
THE ANTERIOR WALL
1.In its whole extent
a. Skin
b. Superficial fascia
c. External oblique aponeurosis
2.In its lateral one-third
The fleshy fibres of the internal oblique
muscle.
13. Inguinal canal
13
Medial
Superficial inguinal ring
The anterior wall is made up of the external
oblique muscle throughout, and is reinforced by
the
internal oblique m. laterally.
The transversus abdominus m. lies even more
laterally as part of the anterior abdominal wall.
Lateral
14. 1.In its whole extent
a. The fascia transversalis
b. The extra peritoneal tissue
c. The parietal peritoneum.
2.In its medial two-thirds
a. The conjoint tendon
b. At its medial end by the reflected part of
the inguinal ligament.
THE POSTERIOR WALL
15. Posterior wall of the inguinal canal
15
Deep inguinal ring
Medial
The posterior wall is formed by transversalis fascia (orange)
throughout and the conjoint tendon (red) medially. The
wall is particularly weak over the deep inguinal ring
Lateral
Conjoint tendon medially
Posterior wall
16. Inguinal canal
16
Floor
Spermatic cord
Medial
Lateral
The transversus abdominis and
internal oblique mm. combine to
form the CONJOINT tendon that
arches over the contents of the
inguinal canal
The conjoint tendon attaches to
the pubic crest, reinforces the
posterior canal wall medially
and also forms the ROOF of the
canal
Conjoint tendon
17. ROOF OF THE INGUINAL CANAL
It is formed by the arched fibres of
the internal oblique and transverse
abdominis muscles.
18. Roof and anterior wall of the
inguinal canal
18
Medial
The anterior wall of the canal is formed by external oblique muscle
(orange) throughout and by internal oblique muscles
(red/black/white) laterally. This wall is weak medially because of the
“hole” in the external oblique muscle (= superficial inguinal ring).
Lateral
Superficial inguinal ring
19. FLOOR
It is formed by the grooved upper
surface of the inguinal ligament;
and at the medial end by the
lacunae ligament
20. Floor of the inguinal canal
20
Floor
Medial
The floor is formed by an incurving of the inguinal ligament,
which is part of the external oblique muscle, forming a gutter.
(Medially it forms the lacunar ligament which is not
illustrated).
Lateral
22. STRUCTURES PASSING THROUGH
THE CANAL
1.The spermatic cord in males, or the round
ligament of the uterus in females, enters the
inguinal canal through the deep inguinal ring
and passes out through the superficial
inguinal ring.
2.The ilioinguinal nerve enters the canal
through the interval between the external
and internal oblique muscles and passes out
through the superficial inguinal ring.
23. Inguinal canal
Spermatic cord enters the
inguinal canal through the
deep inguinal ring
Floor
Spermatic cord
exits through
the superficial
inguinal ring
Deep inguinal ring
Superficial inguinal ring
Lateral Medial
24. Inguinal canals – why have
them?
Allow contents of the scrotum to
communicate with intra-abdominal
contents
Prevent mobile intra-abdominal contents
(e.g. intestine) from entering the scrotum
and possibly becoming damaged, while at
the same time permitting blood vessels,
nerves, lymphatics, vas deferens etc. to
supply the scrotal contents
25. MECHANISM OF
INGUINAL CANAL
The presence of the inguinal canal is
the cause of weakness in the lower
part of the anterior abdominal wall.
This weakness is compensated by the
following factors
26. Obliquity of the inguinal
canal
The two inguinal rings do not lie opposite to
each other. Therefore, when the intra-
abdominal pressure rises the anterior and
posterior walls of the canal are approximated,
thus obliterating the passage. This is known
as the flap valve mechanism.
27. The superficial inguinal ring is
guarded from behind by the
conjoint tendon and by the reflected
part of the inguinal canal.
28. The deep inguinal ring is guarded
from the front by the fleshy fibres of
the internal oblique.
29. Shutter mechanism of the
internal oblique
This muscle has a triple relation to the
inguinal canal. It forms the anterior wall,
the roof, and the posterior wall of the
canal. When it contracts the roof is
approximated to the floor, like a shutter.
31. Slit valve mechanism
Contraction of the external oblique
results in approximation of the two crura
of the superficial inguinal ring . The
integrity of the superficial inguinal ring is
greatly increased by the intercrural fibres.
32. Hormones
may play a role in maintaining the
tone of the inguinal musculature
33. Whenever, there is a rise in intra
abdominal pressure as in coughing ,
sneezing, lifting heavy weights all these
mechanisms come to play, so that the
inguinal canal is obliterated, its openings
are closed, and herniation of abdominal
viscera is prevented.
34.
35.
36. From within outwards, these are as follows:
1.The internal spermatic fascia , derived from
the fascia transversalis; it covers the cord in its
whole extent .
2.The cremasteric fascia is made up of the
muscle loops costituting the cremaster muscle,
and the intervening areolar tissue. It is derived
from the internal oblique and transversus
abdominis muscles.
37. Round ligament of
uterus
The round ligaments are two fibro
muscular flat bands ,10 to 12 cm long,
which lie between the two layers of
broad ligament , begins at the lateral
angle of the uterus, passes through the
deep inguinal ring ,traverses the
inguinal canal and merges with the
areolar tissue of the labium majus
38. Hesselbach’s (Inguinal) Triangle is an
important structure as it is the site for
direct hernias. The triangle has the
following borders:
1) Medial border of rectus
abdominus(medially)
2) Inguinal ligament (inferiorly)
3) Inferior epigastric vessels(laterally)
HESSELBACH’S TRIANGLE
39.
40. A Brief Mention of Hernias
Hernias are abnormal outpouchings of the
abdominal contents (such as the small intestine)
from the cavity in which they belong. There are two
main types of hernias that occur at the inguinal
region. Direct hernia and indirect hernia.
.
41. The posterior wall of the canal is particularly weak
laterally because of the deep inguinal ring
The anterior wall opposite the deep ring is reinforced
laterally by the internal oblique muscles.
A hernia (e.g. of small bowel) that comes through the
deep inguinal ring will have to travel along the
inguinal canal as it cannot push into the reinforced
layers of muscle in the anterior wall of the canal
directly opposite the deep inguinal ring
42. The anterior wall of the canal is weak medially where
the superficial inguinal ring is situated
The posterior wall, opposite the superficial ring, is
reinforced medially by the conjoint tendon that is
formed by fibres of the internal oblique and
transversus abdominis muscles
Abdominal contents cannot normally force themselves
through the superficial ring directly because of the
reinforced posterior wall medially
43. Indirect or oblique hernia
These are the most common inguinal hernias, in
this the contents of the abdomen enter the deep
inguinal ring and traverse the whole length of the
inguinal canal to come out through the superficial
inguinal ring
44. Coverings of indirect hernias
Peritoneum
Internal spermatic fascia
(from transversalis fascia)
Cremaster muscle & fascia
(from transversus abdominis and
internal oblique mm.)
External spermatic fascia
(from external oblique m.)
Superficial fascia
Skin
44
45. Direct Hernias
Direct hernias occurs lateral to the epigastric vessels.
They do not protrude through any ring, but through
an area of weakness in the posterior wall of the
inguinal canal; this area is likely to be Hesselbach’s
Triangle. The hernia is often parallel to the spermatic
cord, but almost never enters the scrotum
46. Coverings of direct hernias
Peritoneum
Transversalis fascia
Conjoint tendon
External oblique aponeurosis
Superficial fascia
Skin
46
