Hernias

11 Hernias



Anatomy of the Abdominal Wall



image

Abdominal Wall: Inguinal Region



Abdominal Wall Layers



• Following are layers from the surface in.
image Skin

image Superficial fascia with a variable amount of subdermal fat: Camper’s fascia, overlying membranous Scarpa’s fascia (subumbilical level)

image Muscle bellies and aponeuroses of the rectus abdominis, external and internal obliques, and transversus abdominis muscles

image Transversalis fascia

image Endoabdominal fascia and the peritoneum (greater sac)


External Oblique (EO) Muscle



• Bilateral origins off of the lower ribs, lumbar fascia, and iliac crest

• On each side, the lower border of its aponeurosis attaches to anterior superior iliac spine and pubic tubercle to form the inguinal ligament.

• Distally, a portion of EO aponeurosis fibers arch posteriorly to insert on the superior pubic ramus, forming the lacunar ligament (of Gimbernat).

• Most lateral of these deep (lacunar) fibers continue to run along the pectin of pubis as the pectineal ligament (of Cooper).

• Some of the most distal fibers arch upward, avoid the pubic tubercle, and merge with the opposite side’s fibers as the reflected inguinal ligament.

• Most muscle and aponeurotic fibers run superolateral to inferomedial (“hands in pockets” orientation).

• Medial part of the EO aponeurosis contributes the most anterior fibers of the rectus sheath.

• Superficial (external) inguinal ring: division in the most inferior aponeurosis; spermatic cord or round ligament passes through

• External oblique fascia contributes to external spermatic fascia.

• Fibers of the medial crus (of the superficial ring) attach to the pubic crest.

• Fibers of the lateral crus attach with the rest of the inguinal ligament to the pubic tubercle.

• EO aponeurosis is relatively weak superiorly, very strong inferiorly.

• Innervation: anterior rami T7-T12 (thoracoabdominal and subcostal nerves)


Internal Oblique (IO) Muscle



• Bilateral origins off the lower ribs, lumbar fascia, and iliac crest

• Fibers run deep, approximately perpendicular to the external oblique layer, from the deep lumbar aponeurosis, curving anteriorly then medially.

• Cremaster muscle and fascia: IO layer surrounding internal spermatic fascia

• Medial IO aponeurosis layer splits to pass around the rectus, as the middle layer of the rectus sheath, above the semicircular lines (of Douglas).

• On each side, the inferior triangle of the IO aponeurosis fuses with the transversus aponeurosis to form the conjoined (conjoint) tendon.

• Innervation: anterior rami T7-T12 (thoracoabdominal nerves) and L1


Transversus Abdominis (TA) Muscle



• Bilateral origins off the lower ribs, lumbar fascia, and iliac crest

• Fibers run deep to the internal oblique layer, mostly posteriorly, becoming largely aponeurotic laterally in the deep back.

• Medial aponeurotic fibers pass posterior to the rectus, as the posterior layer of the rectus sheath, above the semicircular lines (of Douglas).

• On each side, the inferior triangle of the TA aponeurosis fuses with the internal oblique aponeurosis to form the conjoined (conjoint) tendon.

• Deep (internal) inguinal ring: gap in the transversus abdominis, lateral to the inferior epigastric arteries

• Innervation: anterior rami T7-T12 (thoracoabdominal nerves) and L1


Rectus Abdominis Muscle



• Parallel segments of muscle with vertically running fibers; segments joined end-to-end by tendinous insertions (inscriptions)

• Upper segments well separated at the midline

• Lower segments close together at midline

• External oblique aponeurosis is always the most superficial (anterior) component of the rectus sheath.

• Internal oblique aponeurosis splits to run in front of and behind rectus in the sheath above the semilunar lines (somewhat above umbilicus).

• External and internal oblique and transversus aponeuroses components of rectus sheath pass anterior to the rectus below the semicircular lines (below the umbilicus).

• Pyramidalis muscle, present in ~80%
image Lies anterior to the inferior part of the rectus

image Attaches to the anterior pubis and anterior pubic ligament

image Inserts on the linea alba and tenses it

• Innervation: anterior rami T7-T12, thoracoabdominal nerves


Linea Alba



• Midline, tendinous junction between right and left portions of the rectus sheath and the underlying midline tendons of the rectus muscle segments

• Tends to be broader, more well developed superiorly

• Umbilical gap lies about 2/3 of the way down from the linea origin at the xiphoid process.


Transversalis Fascia



• Tough fascial layer just deep to the transversus muscle and aponeurosis, rectus sheath, and rectus abdominis anteriorly

• Overlies the endoabdominal fascia (and fat) superficial to the peritoneum

• Male transversalis fascia outpockets through the deep (internal) inguinal ring, a gap in the transversus abdominis, lateral to the inferior epigastric arteries.

• Internal spermatic fascia: transversalis fascia layer surrounding the layers of the tunica vaginalis around the descended testis, its duct, and vessels

• Iliopubic tract: thickened inferior margin of the transversalis fascia, running parallel, posterior, and deep to the inguinal ligament (reinforcing)

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Aug 12, 2016 | Posted by in ANATOMY | Comments Off on Hernias

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