1. Organization of the antero-lateral abdominal wall
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2. Anterolateral Abdominal Wall
Although the abdominal wall is continuous, it is subdivided into the anterior wall, right and left lateral walls (flanks), and posterior wall for descriptive purposes.
Layers of anterior abdominal wall
Skin
Subcutaneous (Superficial fascia): Fatty and membranous
Deep fascia
Muscles and their aponeurosis:
Extra peritoneal tissue
Peritoneum.
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4. Skin
The skin attaches loosely to the subcutaneous tissue, except at the umbilicus, where it adheres firmly.
Shows ‘creases' which represent the lines of orientation of collagen fibres in the dermis- Langer's lines.
These lines are surgically important – incisions along them heal better leaving a thin scar; while those across them leave big scars.
In pregnant women, obese people and those with abdominal distention from whatever cause, there are dark elongate lines called striae gravidara.
The skin is very sensitive to touch, and quickly when touched, the muscles contract.
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5. Fascia of the Anterolateral Abdominal Wall
Consists of two layers;
Superficial fatty layer (Camper's fascia) containing variable amounts of fat, more in females and in the lower abdomen.
Deep membranous layer (Scarpa's fascia). (+) Contains fibrous tissue and very little fat. (+) Fuses with fascia lata below inguinal ligament) (+) Continuous with the superficial perineal fascia (Colle's fascia) and with that investing the scrotum and penis. Note: Deep fascia is Unremarkable
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8. Applied anatomy
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9. There are 4 main muscles to note:
External oblique; Internal oblique; Transversus abdominis; Rectus abdominis
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10. Compresses and supports abdominal viscera
Transverse abdominal
Internal surfaces of 7 and 12th costal cartilages, thoracolumbar fascia, iliac crest, and lateral third of inguinal ligament
Linea alba with aponeurosis of internal oblique, pubic crest, and pecten pubis via conjoint tendon
Thoracoabdominal nerves (anterior rami of inferior 6 thoracic nerves) and first lumbar nerves
Compresses and supports abdominal viscera
Internal oblique
Thoracolumbar fascia, anterior two-thirds of iliac crest, and lateral half of inguinal ligament
Inferior borders of 10 and 12th ribs, linea alba, and pecten pubis via conjoint tendon
Compress and support abdominal viscera, flex and rotate trunk
External oblique
External surfaces of 5 and 12th ribs
Linea and alba, pubic tubercle, and anterior half of iliac crest
Thoracoabdominal nerves (inferior 5 [T7 and T11] thoracic nerves) and subcostal nerve
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11. The Rectus Sheath
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12. Rectus sheath
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13. Location
Fibrous compartment for rectus abdominis muscle in the paramedian abdominal wall.
Formation
Formed of the aponeurosis of abdominal muscles.
It has a posterior layer and anterior layer. Proximal 1/3rd
The anterior layer joins the aponeurosis of the external oblique to form the anterior wall of the rectus sheath.
The posterior layer joins with the aponeurosis of the transversus abdominis to form the posterior wall of the rectus sheath.
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14. Location…
Middle 1/3 rd
Aponeurosis of internal oblique joins external oblique aponeurosis to form anterior wall.
Posterior wall is formed by aponeurosis of transversus abdominis muscle
Distal 1/3 rd
Mid way between umbilicus and pubic crest all three aponeurosis form the anterior layer
The posterior layer is formed only by fascia transversalis
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15. Location…
The anterior and posterior layers fuse in the midline to form the linear alba, a fibrous intersection extending from the xiphoid process to the pubic symphysis.
The inferior ¼ of the rectus sheath is deficient posteriorly. The limit of the posterior wall is marked by the arcuate line
The lateral margin of rectus sheath is called linea semilunaris
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16. Contents of Rectus Sheath
Rectus abdominis muscle
Inferior and superior epigastric vessels
Terminal parts of the lower five intercostal nerves, and the Subcostal nerve.
Fibro fatty connective tissue
Occasionally lymph node(s)
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17. Extra peritoneal fascia
Transparent ‘membrane' which lines the inside of the abdominal wall.
Its parts are named according to what it lines e.g. (+) diaphragmatic fascia; (+) iliac fascia; (+) psoas fascia. (+) fascia transversalis ( part covering the muscle transversus abdominis ).
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18. Blood supply to the anterior abdominal wall
Arteries
Inferior epigastric : External iliac
Superficial circumflex iliac : Femoral arterty
Deep circumflex iliac : femoral artery
Superior epigastric : internal thoracic
Lower intercostal : Abdominal Aorta
Subcostal arteries : Abdominal aorta
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20. Veins The veins correspond to the arteries,
but: Inferior epigastric vein anastomoses with lateral thoracic vein.
Superficial epigastric vein anastomoses with lateral thoracic vein.
These two unite the veins of the upper and lower halves of the body (of the azygous system).
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21. Lymphatic Drainage Superior to the umbilical level: Axillary nodes
Parasternal nodes
Inferior to the umbilical level:
Superficial Inguinal lymph nodes
Deep inguinal nodes
External iliac nodes
Lumbar nodes
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22. Innervation
The skin and muscles of the anterolateral abdominal wall are supplied mainly by the following nerves
Thoracoabdominal nerves: the distal, the anterior rami of the inferior six thoracic spinal nerves; Lateral (thoracic) cutaneous branches: of the thoracic spinal nerves T7 and T9 or T10.
Subcostal nerve: the large anterior ramus of spinal nerve T12.
Iliohypogastric and ilioinguinal nerves: terminal branches of the anterior ramus of spinal nerve L1.
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23. The internal surface of anterior abdominal wall
Inferior to the umbilicus, there are 5 folds:
The median umbilical fold is due to median umbilical ligament, the remnant of the urachus, which develops from the allantois. It attaches to the urinary bladder.
2 medial umbilical folds formed by medial umbilical ligaments – the obliterated umbilical arteries.
2 lateral umbilical folds – formed by the inferior epigastric vessels
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25. INGUINAL REGION
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26. The inguinal canal
Canal represents path taken by testis out of the abdomen.
Boundaries
Floor: Inguinal ligament and lacunar ligament Roof: Arching fibres of internal oblique and transversus abdominis.
Antero lateral:Aponeurosis of external oblique
Posterior: Fascia transversalis laterally and conjoint tendon medially (of transversus and internal oblique abdominal muscles)
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32. Applied anatomy Direct hernia
Less common type
more likely in older men (over 40).
Protrudes anteriorly through the posterior wall of inguinal canal
Medial to inferior epigastric artery.
passes through inferior part of inguinal triangle.
Does not pass through the deep inguinal ring, but pass through superficial ring.
Usually results from weakening of the Conjoint tendon
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34. Indirect hernia More common type, makes 75% of all.
more common in male children,
Takes the path taken by testis through inguinal canal
Leaves lateral to inferior epigastric artery.
Passes outside inguinal triangle.
Passes through the deep inguinal ring and superficial ring to enter the scrotum
More likely in patent processus vaginalis
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36. Review Questions
Describe the muscles, blood supply, lymphatic drainage and sensory innervation of the anterior abdominal wall
Discuss the formation and contents of the inguinal canal. Add notes on the distinction between direct and indirect inguinal hernias. List six structures that must be safeguarded during hernial repair
Describe the formation and contents of the rectus sheath
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37. Review Questions
Outline the general organization of the superficial fascia of the anterior abdominal wall, and the perineum. Add clinical notes on the implication of this organization
Describe in detail the pattern and clinical significance of the blood supply of the anterior abdominal wall.
State the advantages and disadvantages of the various incisions in the anterior abdominal wall.
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