Abdominal wall

• Layers of abdominal wall


  • Skin
  • Superficial fascia
  • External oblique muscle
  • Internal oblique muscle
  • Transversus abdominis muscle
  • Rectus abdominis, Pyramidalis [inside rectus sheath]
  • Transversalis fascia
  • Extraperitoneal connective tissue
  • Parietal layer of peritoneum
• Opposite the linea alba, the layers are reduced to six in number
• Layers reduced to six in number

  • Superficial fatty layer
  • Deep membranous layer
• Muscles of the anterior abdominal wall

  • Iliac crest
  • Tubercle of the iliac crest
  • Anterior Superior Iliac spine
  • Pubic tubercle
• Iliac crest


  Forms the lower limit of abdominal wall on either side
• Tubercle of the iliac crest


  Present on the outer lip of the iliac crest, 5cm from ASIS at the level of L5
• Anterior Superior Iliac spine


  The part of the pelvis lies at the level of sacral promontory
• Pubic tubercle


  Prominences on the pubic bone, found lateral to the median plane
• External oblique


  • Origin: Outer surface and lower border of the lower eight ribs
  • Insertion: Anterior half of the outer lip of iliac crest
  • Upper and middle fibres end in the anterior aponeurosis
  • Attached by its aponeurosis to xiphoid process, linea alba, pubic symphysis, pubic crest and pectineal line
  • Posterior margin is free and forms the anterior boundary of lumbar triangle
• Inguinal ligament


  Thick ligamentous portion of the lower border of the external oblique aponeurosis which folds inwards
• Inguinal ligament


  • Length: 12 to 14 cm
  • Attachment: Lateral - Anterior superior iliac spine, Medial - Pubic tubercle
  • Expansions: Lacunar ligament, Reflected part of the inguinal ligament, Pectineal ligament
  • Muscles attached: Lateral 2/3 - internal oblique, Lateral 1/3 - transverse abdominis, Middle 1/3 - cremaster muscle
• Internal oblique


  • Origin: Lateral 2/3rd of the inguinal ligament, Anterior 2/3rd of the intermediate area of the iliac crest, Thoracolumbar fascia
  • Insertion: Lower 3 or 4 ribs and their cartilages, Major fibers end in the anterior aponeurosis which is attached to the linea alba and cartilages of 7th, 8th & 9th ribs
  • Forms CONJOINT TENDON along with transverse abdominis
• Transversus abdominis


  • Origin: Lateral 1/3rd of the inguinal ligament, Anterior 2/3rd of the inner lip of the iliac crest, Thoracolumbar fascia, Inner surface of the lower 6 costal cartilages
  • Insertion: Muscle ends in an anterior aponeurosis, which is attached to the linea alba
  • Lower fibers curve downwards and medially to form CONJOINT TENDON along with the aponeurosis of internal oblique
• Conjoint tendon (Falx inguinalis)

  • Formed from the lower fibers of internal oblique and the lower part of the aponeurosis of transversus abdominis
  • Attached to the pubic crest and pectineal line
  • Descends behind the superficial inguinal ring and strengthens the medial part of the posterior wall of inguinal canal
• Transversalis fascia


  • Thin layer of connective tissue lying on the inner surface of the transversus abdominis
  • Presents DEEP INGUINAL RING - oval shaped space in the fascia transversalis situated 1.25 cm above the mid-inguinal point
  • Fascia transversalis forms the anterior wall of the femoral sheath
• Rectus abdominis


  • Long, strap muscle present just by the side of the mid-line
  • Originates by 2 heads - Lateral head from pubic crest & pubic tubercle, Medial head from ligamentous fibers covering the anterior surface of the Pubic symphysis
  • Insertion: By 3 muscular slips to 5th, 6th, & 7th ribs
  • Nerve supply: Lower 5 intercostal nerves and subcostal nerve
• Rectus abdominis


  • Usually shows three tendinous intersections - One at the level of umbilicus, one at the level of the xiphoid process, and the third midway between the two
  • These intersections pass transversely or obliquely across the muscle, rarely extend completely through its substance up to the posterior surface, and are adherent to the anterior wall of the rectus sheath
• Pyramidalis


  • Triangular or pyramidal in shape, sometimes the muscle is absent or duplicated on one or both sides
  • Origin: from the pubic symphysis and the pubic crest
  • Insertion: to the linea alba
  • Nerve supply: subcostal nerve
  • Action: tensor of linea alba
• Nerve supply of muscles of anterior abdominal wall

  • Rectus abdominis - T7 – T11 intercostal nerves & subcostal N
  • Pyramidalis - T12 (subcostal nerve)
  • External oblique - T 7 – T11 intercostal, subcostal, iliohypogastric and ilio-inguinal nerves
  • Internal oblique - T 7 – T11 intercostal, subcostal, iliohypogastric and ilio-inguinal nerves
  • Transversus abdominis - T 7 – T11 intercostal, subcostal, iliohypogastric and ilio-inguinal nerves
• Rectus sheath


  • Aponeurotic sheath derived from the aponeurosis of the three flat muscles of the anterior abdominal wall
  • Function: To maintain the strength of the anterior abdominal wall, To check the bowing of the rectus abdominis muscle during its contraction and hence increasing its efficiency
  • Features: Presents anterior and posterior walls, Anterior wall is complete and covers the entire extent of the rectus abdominis muscle, Anterior wall is firmly adherent to the tendinous intersections of the rectus abdominis, Posterior wall is deficient above and below, and thus the rectus abdominis muscle lies directly on the 5th, 6th and 7th costal cartilages, Below the umbilicus and between the umbilicus and pubic symphysis the posterior wall presents a free curved margin with concavity facing inferiorly called arcuate line of Douglas
• Formation of rectus sheath

  • Above the level of costal margin: Anterior wall - formed by the aponeurosis of external oblique only, Posterior wall - is deficient

  From the costal margin to the level midway between the umbilicus and pubic symphysis: Anterior wall - formed by the fusion of aponeurosis of external oblique and anterior lamina of aponeurosis of internal oblique, Posterior wall - formed by the posterior laminal of internal oblique and transversus abdominis muscle

  Below the level of arcuate line: Anterior wall - formed by the aponeurosis of all the three flat muscles of the anterior abdominal wall, Posterior wall - the aponeurosis of the three flat muscles is deficient, and is formed by the fascia transversalis
• Contents of rectus sheath

  • Muscles - rectus abdominis, pyramidalis
  • Vessels - superior and inferior epigastric vessels
  • Nerves - terminal part of the lower six intercostal and subcostal nerves
• Epigastric hernia


  The linea alba which extends from the xiphoid process to the pubic symphysis is wider above the umbilicus and narrow below the umbilicus. It becomes weak in elderly multiparous women and chronically ill children. When the intra-abdominal pressure is excessively raised, a small amount of extra-peritoneal fat may drag behind it, a small peritoneal sac which may contain a portion of the greater omentum forming the epigastric hernia
• Folds and fossae of anterior abdominal wall

  • Median umbilical fold - contain the remnant of urachus (median umbilical ligament)
  • Medial umbilical fold - contains obliterated umbilical artery (medial umbilical ligament)
  • Lateral umbilical fold - contains the inferior epigastric vessels
  • Supravesical fossa
  • Medial inguinal fossa
  • Lateral inguinal fossa
• Internal surface of the anterior abdominal wall

  • Median Umbilical fold
  • Medial umbilical fold
  • Lateral umbilical fold
  • Falciform ligament
  • Supravesical fossa
  • Medial inguinal fossa
  • Hesselbach triangle (Inguinal triangle) - site for direct inguinal hernia
  • Lateral inguinal fossa - includes the deep inguinal ring which is the site for indirect inguinal hernia
• Inguinal canal


  Definition: It is an musculoaponeurotic tunnel

  Situation: Above and parallel with medial half of the inguinal ligament

  Length: 3.5 to 4 cm

  Extent: DIR, SIR
• Epigastric hernia


  A small peritoneal sac which may contain a portion of the greater omentum, formed when extra-peritoneal fat drags behind excessively raised intra-abdominal pressure
• Folds and fossae of anterior abdominal wall

  • Median umbilical fold
  • Medial umbilical fold
  • Lateral umbilical fold
  • Supravesical fossa
  • Medial inguinal fossa
  • Lateral inguinal fossa
• Median umbilical fold


  Contains the remnant of urachus (median umbilical ligament)
• Medial umbilical fold


  Contains obliterated umbilical artery (medial umbilical ligament)
• Lateral umbilical fold


  Contains the inferior epigastric vessels
• Hesselbach triangle (Inguinal triangle) is the site for direct inguinal hernia
• Inguinal canal


  An musculoaponeurotic tunnel above and parallel with medial half of the inguinal ligament, 3.5 to 4 cm in length, extending from deep inguinal ring to superficial inguinal ring
• Contents of the inguinal canal

  • Spermatic cord with its content in males
  • Round ligament of uterus in females
  • Ilio-inguinal nerve both in males & females
• Boundaries of the inguinal canal

  • Anterior wall: Skin and superficial fascia, Aponeurosis of the external oblique muscle, Muscle fibers of internal oblique
  • Posterior wall: Fascia transversalis, Conjoint tendon, Reflected part of inguinal ligament
  • Roof: Arched fibres of internal oblique and transversus abdominis muscles
  • Floor: Medial half of the Inguinal ligament, Lacunar ligament
• Deep inguinal ring


  Inlet of the inguinal canal
• Superficial inguinal ring


  Outlet of the inguinal canal
• Contents of the spermatic cord

  • Vas Deferens
  • Testicular artery, artery to ductus deferens, cremasteric artery
  • Sympathetic plexus of nerves to testis, and genital branch of the genito-femoral nerve
  • Pampiniform plexus of testicular veins
  • Lymph vessels of the testis
  • Remnants of processes vaginalis and connective tissue
• Inguinal hernia


  Protrusion of part of the contents of the abdomen through the inguinal region of the abdominal wall
• Mechanisms which prevent hernia in the inguinal region

  • Obliquity of the inguinal canal – flap valve mechanism
  • Shutter valve mechanisms of the arched fibers of the internal oblique & transversus abdominis
  • Ball-valve action of the cremaster muscle
  • Presence of internal oblique muscle fibers in front of Hesselbach's triangle
  • Strong conjoint tendon & reflected part of inguinal ligament in front of Hesselbach's triangle
  • Slit-valve mechanism – contraction of external oblique muscle results in approximation of 2 crura of the superficial inguinal ring