The Abdominal Wall

The Abdominal Wall Inguinal and Posterior Abdominal Wall Lectured by Bien Eli Nillos, MD

Inguinal Canal ► An

oblique passage through the lower part of the anterior abdominal wall ► Present in both sexes ► Males: spermatic cord and ilioinguinal nerve ► Females: round ligament of the uterus and ilioinguinal nerve ► About 1 and ¼ inches long in the adult

► Extends

from the deep inguinal ring which is a hole in the transversalis fascia, downward and medially to the superficial inguinal ring which is a hole in the aponeurosis of the external oblique muscle. ► Lies parallel to and immediately above the inguinal ligament

► In

the newborn, the deep ring lies almost directly posterior to the superficial ring, thus the canal is considerably short at this age. ► As one grows up, the deep ring moves laterally

Deep Inguinal Ring ► Oval

opening ► ½ inch above the inguinal ligament midway betwee the anterior superior iliac spine and the symphysis pubis ► Medially are the inferior epigastric vessels

Superficial Inguinal Ring ► Triangular

shaped defect ► Base is formed by the pubic crest ► The crura – margins of the ring, give origin to the external spermatic fascia

► Anterior

wall of the canal – formed by the aponeurosis of the external oblique muscle, reinforced in its lateral third by the fibers of origin of the internal oblique. ► This wall is therefore strongest where it lies opposite the weakest part of the posterior wall --- the deep inguinal ring

► Posterior

Wall of the Canal – formed by the transversalis fascia, reinforced in its medial third by the conjoint tendon (the common tendon of insertion of the internal oblique and transversus muscles) ► The wall is therefore strongest where it lies opposite the weakest part of the anterior wall --- superficial inguinal ring.

► Inferior

wall or floor of the canal – formed by the rolled-under inferior edge of the aponeurosis of the external oblique muscle (the inguinal ligament) and at its medial end the lacunar ligament

► Superior

wall or roof of the canal – formed by the arching lowest fibers of the internal oblique and transversus abdominis muscle.

► On

coughing or straining, the arching lowest fibers of the internal oblique and transversus abdominis muscles contract  flattening out the arched roof so that it is lowered toward the floor  making the canal virtually closed.

The Spermatic Cord ► Vas

Deferens ► Testicular artery ► Cremasteric Artery ► Genital branch of the Genitofemoral nerve ► Pampiniform plexus ► Lymphatic vessels ► Processus vaginalis

► The

spermatic cord is sensitive to torsion, in which the testicle rotates within its sac and kinks off its own blood supply. Testicular torsion may result in irreversible damage to the testicle within hours.

Coverings of the Spermatic Cord ► Internal

spermatic fascia – derived from the transversalis fascia ► Cremasteric Fascia – derived from the internal oblique muscle ► External spermatic fascia – derived from the external oblique aponeurosis

Scrotum ► Outpouching

of the lower part of the anterior abdominal wall ► Contains the testes, epididymes and the lower ends of the spermatic cord ► The skin is wrinkled and pigmented and forms a single pouch ► The slightly raised ridge in the midline indicates the line of fusion of the two lateral labioscrotal swellings.

► The

superficial fascia is continuous with the fatty and membranous layers of the anterior abdominal wall: the fat is replaced by a smooth muscle  Dartos muscle ► The Cremaster muscle can be made to contract by stroking the skin on the medial aspect of the thigh  cremasteric reflex

► Tunica

vaginalis  lies within the spermatic fasciae and covers the anterior, medial and lateral surfaces of each testis. ► It is a closed sac, invaginated from behind by the testis.

Posterior Abdominal Wall ► Formed

in the midline by the five lumbar vertebrae and their intervetebral discs; laterally by the 12th ribs, the upper part of the bony pelvis, psoas muscles, the quadratos lumborum, aponeurosis of origin of the transversus abdominis muscles. ► The iliacus muscles lie in the upper part of the bony pelvis

Psoas Muscle ► Origin:

transverse process, bodies and intervertebral discs of 12th thoracic and five lumbar vertebrae ► Insertion: with iliacus into lesser trochanter of the femur ► Nerve supply: lumbar plexus ► Action: flexes thigh on trunk

Quadratus Lumborum ► Origin:

iliolumbar ligament, iliac crest, tips of the transverse processes of the lower lumbar vertebrae ► Insertion: 12th rib ► Nerve supply: Lumbar plexus ► Action: Fixes 12th rib during inspiration; laterally flexes vertebral column same side

Iliacus ► Origin:

iliac fossa ► Insertion: with psoas into lesser trochanter of femur ► Nerve supply: femoral nerve ► Action: Flexes thigh on trunk