The Inguinal Region
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Abdominal walls | Main Anatomy Index | Peritoneum
and peritoneal cavity
Last updated 30 March 2006
The Inguinal Region
- The inguinal region is very important surgically because it is the site of inguinal hernias.
- Although both sexes may get these, it is much more common in males.
- The inguinal region is an area of weakness in the anterior abdominal wall because
of the prenatal penetration of the wall by the testis and the spermatic
cord.
The Inguinal Canal
- Owing to the obliquity of the inguinal canal, the deep and
superficial inguinal rings do not coincide.
- Increases in intra-abdominal pressure act on the deep
inguinal ring, which forces the posterior wall of the canal against the anterior wall.
- During coughing and straining, the raise intra-abdominal pressure threatens to force
some of the abdominal contents through the canal, producing a hernia.
- However, vigorous contraction of the arched fleshy
fibres of the internal oblique and transversus abdominis muscles "clamp down".
- The action is like a half-sphincter that helps prevent
herniation.
- The conjoint tendon and rectus abdominis muscle also reinforce the
superficial inguinal ring (as the external oblique aponeurosis pushes against these when
intra-abdominal pressure rises).
The Anterior
Wall of the Inguinal Canal
The Posterior
Wall of the Inguinal Canal
- Formed throughout by the transversalis fascia, which is
reinforced medially by the conjoint tendon.
The Floor of the
Inguinal Canal
- This is formed by the superior surface of the inguinal ligament
and the lacunar ligament.
The Roof of the Inguinal
Canal
The
Superficial Ring of the Inguinal Canal
- Emerging from the superficial inguinal ring is the spermatic
cord in the male and the round ligament of the uterus
in the female.
- In addition, the ilioinguinal nerve makes its exit
through the ring to supply skin on the superomedial aspect of the thigh.
- The central point of the superficial inguinal ring is superior to the pubic
tubercle.
- The superficial inguinal ring is just palpable superior and
lateral to the pubic tubercle.
The Lateral Crus of
the Superficial Inguinal Ring
- This is formed by the part of the external oblique aponeurosis
that is attached to the pubic tubercle via the inguinal ligament.
- The spermatic cord rests on the inferior part of this
crus.
The Medial Crus of
the Superficial Inguinal Ring
- This is formed by the part of the external oblique aponeurosis
that diverges to attach to the pubic bone and pubic crest, medial to the pubic tubercle.
- Intercrural fibres from the inguinal ligament arch
superomedially across the superficial inguinal ring.
- These prevent the crura from spreading apart.
The Deep Ring of the
Inguinal Canal
- This slit-like opening in the transversalis fascia is
located just lateral to the inferior epigastric artery.
- The deep ring is immediately superior to the midpoint of the inguinal ligament.
- The margins of the deep ring are not sharply defined, as are those in the superficial
ring.
The Spermatic Cord
- This cord suspends the testis in the scrotum and consists of the structures running to
and from the testis.
- They are surrounded by protective coverings derived from the anterior abdominal wall.
- The spermatic cord begins at the deep inguinal
ring, lateral to the inferior epigastric artery,
where its constituents assemble, and ends at the posterior border of the testis.
Constituents of
the Spermatic Cord
1. The Ductus Deferens
- This is the large duct of the testis, formerly called the vas
deferens.
- It lies in the posterior part of the spermatic cord and is easily palpable because of
its thick wall of smooth muscle.
2. Arteries
- The testicular artery arises from the anterior aspect
of the aorta at the level of L2 vertebrae.
- This is the main artery supplying the testis and the epididymis.
- The artery of the ductus deferens is a slender vessel
that arises from the inferior vesical artery.
- It accompanies the ductus deferens throughout its course
and anastomoses with the testicular artery near the testis.
- The cremasteric artery is a small vessel that arises
from the inferior epigastric artery.
- It supplies the cremaster muscle and other
coverings of the spermatic cord.
3. Veins
- Up to 12 veins leaving the posterior surface of the
testis anastomose to form a pampiniform plexus (L. pampinus,
tendril).
- This large vine-like plexus forms a large part of the
spermatic cord, surrounding the ductus deferens and
arteries in the spermatic cord.
4. Nerves
- There are sympathetic fibres on the arteries and both sympathetic and parasympathetic
fibres on the ductus deferens.
- The genital branch of the genitofemoral nerve passes
into the spermatic cord and supplies the cremaster
muscle.
5. Lymph Vessels
- Lymph vessels draining the testis and immediately associated structures pass superiorly
in the spermatic cord.
- These vessels end in the lumbar and preaortic lymph nodes.
Coverings of the
Spermatic Cord
The Internal Spermatic
Fascia
- As the processus vaginalis (embryological) evaginated the transversalis fascia at the deep inguinal ring, it carried a thin layer of
fascia that became the internal spermatic fascia.
- It constitutes the filmy innermost covering of the
spermatic cord.
The Cremaster Muscle and
Cremasteric Fascia
- As the processus vaginalis, with its covering of transversalis fascia evaginated under
the edge of the internal oblique muscle,
it acquired some of this muscle's fibres and its investing fascia.
- These fibres form the cremaster muscle and cremasteric fascia.
- The cremasteric fascia forms the middle covering of the spermatic cord, which contains
loops of the cremaster muscle.
- The cremaster muscle, which is continuous with the internal oblique muscle, reflexly
draws the testis to a more superior position in the scrotum (cremasteric
reflex), particularly in cold temperatures.
The External Spermatic
Fascia
- As the external oblique muscle was
evaginated by the processus vaginalis, it formed the superficial inguinal ring and an
extension of its aponeurosis was carried outward.
- This layer became the external spermatic fascia, the thin
outermost covering of the spermatic cord.