1. Structure of the abdominal wall The abdomen is the region of the trunk that lies between the diaphragm above which separate it from the thoracic wall and the inlet of the pelvis below which communicates it with the pelvis. Anteriorly, the abdominal wall is formed above by the lower part of the thoracic cage & below by the rectus abdominis ;external oblique ; internal oblique and transversus abdominis muscles and fasciae. Posteriorly, the abdominal wall is formed in the midline by the 5 lumbar vertebrae & their intervetebral discs. Laterally,it is formed by the 12 th rib ; the upper part of bony pelvis with the iliacus muscles; psoas muscles; quadratus lumborum muscles and the aponeuroses of origin of the transversus abdominis muscles. The abdominal wall are lined by a fascial envelope & the parietal peritoneum.

2. Anterior abdominal wall It is made up of skin; superficial fascia; deep fascia; muscles; extraperitoneal fascia and parietal peritoneum. Skin It is loosely attached to the underlying structures except at the umbilicus where it is tethered to the scar tissue. The natural lines of cleavage rows of the skin are constant and run downward & forward almost horizontally around the trunk. Superficial Fascia It can be divided into a superficial fatty layer ( fascia of Camper ) & a deep membranous layer ( Scarpa’s fascia ). The fatty layer is continuous with the superficial fat over the rest of the body and may be thick 8cm ( 3 inch ) or more in obese patients. In the scrotum, it is represented as a thin layer of smooth muscle ( Dartos muscle ).

3. The membranous layer It is thin & fades out laterally and above where it becomes continuous with the superficial fascia of the back and thorax. Inferiorly, it passes onto the front of the thigh where it fuses with the deep fascia one fingerbreadth below the inguinal ligament. In the midline inferiorly, it is not attached to the pubis but forms a tubular sheath for the penis or clitoris. Below, in the perineum, it enters the wall of the scrotum or labia majora. From there it passes to be attached on each side to the margins of the pubic arch. It is here referred to as Colles’s fascia. Posteriorly, it fuses with the perineal body & the posterior margin of the perineal membrane In the scrotum, it persists as a separate layer. Deep fascia: It is a thin layer of connective tissue covering the muscles. It lies immediately deep to the membranous layer of superficial fascia.

4. Clinical Notes 1- Surgical Incisions All surgical incisions should be made in the line of cleavage ( direction of the rows of the collagen fibers ) in the dermis. These fibers run in parallel rows. An incision along a cleavage line will heal as a narrow scar, whereas one that crosses the lines will heal as wide or heaped- up scars ( ugly ). 2- Extravasation of urine Rupture of penile urethra may be followed by extravasation of urine into the scrotum, perineum and penis and then up into the lower part of the anterior abdominal wall deep to the membranous layer of fascia. The urine is excluded from the thigh because of the attachment of the fascia to the fascia lata.

6. Muscles of the Anterior Abdominal Wall They are 3 broad thin sheets that are aponeurotic in front. From exterior to interior they are the external oblique ; internal oblique and transversus abdominis. The rectus abdominis,a wide vertical muscle that lies on either side of the midline. Anteriorly, as the aponeuroses of the 3 muscles sheets pass forward, they enclose the rectus abdominis to form the rectus sheath. The lower part of the rectus sheath contains pyramidalis muscle.

7. External oblique It is a broad ; thin ; muscular sheet that arises from the outer surfaces of the lower 8 th ribs and fans out to be inserted into the xiphoid process ; linea alba ; pubic crest; pubic tubercle and the anterior half of the iliac crest. Most of the fibers are inserted by means of a broad aponeurosis. A triangular- shaped defect in the external oblique aponeurosis lies above & medial to the pubic tubercle (Superficial inguinal ring ) The spermatic cord or round ligament of the uterus passes through this opening and carries the external spermatic fascia or the external covering of the round ligament of the uterus from the margins of the ring. Between the anterior superior iliac spine & the pubic tubercle, the lower border of the aponeurosis is folded backward on itself, forming the inguinal ligament

8. From the medial end of the inguinal ligament, the lacunar ligament extends backward & upward to the pectineal line on the superior ramus of the pubis. The sharp, free crescentric edge of the lacunar ligament forms the medial margin of the femoral ring. On reaching the pectineal line, the lacunar ligament becomes continuous with a thickening of the periosteum called the pectineal ligament. The lateral part of the posterior edge of the inguinal ligament gives origin to part of the internal oblique & transversus abdominis muscles. The inferior rounded border of the inguinal ligament is attached to the deep fascia of the thigh ( fascia lata ).

9. Internal Oblique It is a broad, thin, muscular sheet that lies deep to the external oblique. It arises from the lumbar fascia, the anterior two thirds of the iliac crest and the lateral two thirds of the inguinal ligament. Its fibers radiate as they pass upward & forward. It is inserted into the lower borders of the lower 3 ribs & their costal cartilages ( lower 5 ribs ); the xiphoid process; the linea alba and the symphysis pubis. It has a lower free border that arches over the spermatic cord or the round ligament and then descends behind it to be attached to the pubic crest & the pectineal line.

10. Near their insertion, the lowest tendinous fibers are joint by similar fibers from the transversus abdominis to form the conjoint tendon. The conjoint tendon is attached medially to the linea alba. It has a lateral free border. As the spermatic cord or round ligament passes under the lower border of the internal oblique,it carries with it some of the muscle fibers that are called the cremaster muscle.This muscle passes inferiorly as a covering of the spermatic cord and enters the scrotum. The cremasteric fascia is the term used to describe the cremaster muscle & its fascia.

11. Transversus muscle It is a thin sheet of muscle that lies deep to the internal oblique. Its fibers run horizontal forward. It arises from the deep surface of the lower 6 costal cartilages. ( interdigitating with the diaphragm ); the lumbar fascia ; anterior two thirds of the iliac crest and the lateral third of the inguinal ligament. It is inserted into the xiphoid process ; linea alba and the symphysis pubis. N.B. The posterior border of the internal oblique & transversus muscles are attached to the lumbar vertebrae by the lumbar fascia.

12. Rectus Abdominis It is a long strap muscle that extends along the whole length of the anterior abdominal wall. It is broader above and lies close to the midline which it is separated from it by the linea alba ( strong avascular fibrous tissue ). It arises by 2 heads from the front of the symphysis pubis & from the pubic crest. It is inserted into the 5 th 6 th and 7 th costal catilages & xiphoid process. N.B. pyramidalis muscle lies in front of the lower part of the rectus abdominis. It arises by its base from the anterior surface of the pubis and is inserted into the linea alba.

13. Its lateral margin forms a curved ridge that can be palpated and often seen when it contracts ; it is termed the linea semilunaris which extends from the tip of the 9 th costal cartilage to the pubic tubercle. The rectus abdominis muscle is divided into distinct segments by 3 transverse tendinous intersections. One at the level of the xiphoid process ; one at the level of the umbilicus and one halfway between these two. These intersections are strongly attached to the anterior wall of the rectus sheath. The rectus abdominis is enclosed between the aponeuroses of the external & internal oblique and transversus muscles which form the rectus sheath.

14. Rectus Sheath It is a long fibrous sheath that encloses the rectus abdominis muscle & pyramidalis and contains the anterior rami of the lower 6 thoracic nerves & the superior and inferior epigastric vessels & lymph vessels. It is formed by the aponeuroses of the 3 lateral abdominal muscles. It has 3 levels for the description: 1- Above the costal margin, the anterior wall is formed by the aponeurosis of the external oblique. The posterior wall is formed by the thoracic wall ( 5 th ; 6 th and 7 th costal cartilages & the intercostal spaces ). 2- Between the costal margin & the anterior superior iliac spine, the aponeurosis of the internal oblique splits to enclose the rectus muscle & the external oblique aponeurosis is directed in front of the muscle & the transversus abdominis is directed behind the muscle.

15. 3- Between the level of the anterosuperior iliac spine & the pubis, the aponeurosis of all 3 muscles form the anterior wall. The posterior wall is absent & the rectus muscle lies in contact with the fascia transversalis. Its posterior wall has a free curved lower border called the arcuate line. At this site, the inferior epigastric vessels enter the rectus sheath & pass upward to anastomose with the superior epigastric vessels. It is separated from its fellow on the opposite side by a fibrous band called the linea alba which extends from the xiphoid process down to the symphysis pubis & is formed by the fusion of the aponeurosis of the lateral 3 muscles of the 2 sides. Its posterior wall is not attached to the rectus abdominis muscle but its anterior wall is firmly attached to it by the muscle’s tendinous intersections.

16. Function of the Anterior Abdominal Wall 1- The oblique muscles laterally flex & rotate the trunk. 2- The rectus abdominis flexes the trunk & stabilizes the pelvis. 3- The pyramidalis keeps the linea alba taut during the process. 4- The muscles of the anterior & lateral abdominal walls assist the diaphragm during inspiration by relaxing as the diaphragm descends. 5- They assist in the act of forced expiration that occurs during coughing and sneezing by pulling down the ribs & sternum. 6- Their tone plays an important part in supporting the abdominal viscera. 7-They increase the intra-abdominal pressure & help in micturition, defecation, vomiting and parturition.

17. Nerve Supply of Anterior Abdominal Wall Muscles 1- The oblique & transversus abdominis muscles are supplied by the lower 6 thoracic nerves & ilioinguinal and iliohypogastric nerves. 2- The rectus abdominis is supplied by the lower 6 thoracic nerves. 3- The pyramidalis is supplied by the 12 th thoracic nerve.

18. Fascia Transversalis It is a thin layer of fascia that lines the transversus abdominis muscle and is continuous with a similar layer lining the diaphragm and the iliacus muscle. Extraperitoneal Fat It is a thin layer of connective tissue that contains fat and lies between the fascia transversalis and the parietal peritoneum. Parietal Peritoneum It is a serous membrane that lines the walls of the abdomen and is continuous below with the parietal peritoneum lining the pelvis. N.B. 1- The fascia transversalis, the diaphragmatic fascia, the iliacus fascia and the pelvic fascia form one continuous lining to the abdomen and pelvis. 2- The femoral sheath is formed from the fascia transversalis & fascia iliaca.

19. Nerves of the Anterior Abdominal Wall They are the anterior rami of the lower 6 thoracic & the first lumbar nerves. The 6 th thoracic nerve is called the subcostal nerve while the other 5 nerves are called intercostal nerves. The 1 st lumbar is the iliohypogastric & ilioinguinal nerves. They pass forward in the interval between the internal oblique & the transversus muscles. They supply the skin of the anterior abdominal wall & the muscles and the parietal peritoneum. The lower 6 thoracic nerves pierce the posterior wall of the rectus sheath to supply the rectus & pyramidalis muscles. They terminate by piercing the anterior wall of the sheath and supplying the skin.

20. The 1 st lumbar nerve does not enter the rectus sheath. The iliohypogastric nerve, pierces the external obligue aponeurosis above the superficial inguinal ring. The ilioinguinal nerve emerges through the ring. They end by supplying the skin just above the inguinal ligament & symphysis pubis. The dermatome of T7 is located in the epigastrium over the xiphoid process. The dermatome of T10 includes the umbilicus and that of L1 lies just above the inguinal ligament & the symphysis pubis.

21. Arteries of the Anterior Abdominal Wall 1-The superior epigastric artery, is one of the terminal branches of the internal thoracic artery that enters the upper part of the rectus sheath between the sternal & costal origins of the diaphragm. It descends behind the rectus muscle supplying the upper central part of the anterior abdominal wall and anastomoses with the inferior epigastric artery. 2-The inferior epigastric artery, is a branch of the external iliac artery just above the inguinal ligament. It runs upward & medially along the medial side of the deep inguinal ring. It pierces the fascia transversalis to enter the rectus sheath anterior to the arcuate line. It ascends behind the rectus muscle, supplying the lower central part of the anterior abdominal wall & anastomoses with the superior epigastric artery.

22. 3- The deep circumflex iliac artery, is a branch of the external iliac artery just above the inguinal ligament. It runs upward & laterally toward the anterior superior iliac spine and then continues along the iliac crest. It supplies the lower lateral part of the abdominal wall. 4- The lower 2 posterior intercostal arteries, are branches of the descending thoracic aorta, 5- The 4 lumbar arteries, are branches of the abdominal aorta. They pass forward between the muscle layers and supply the lateral part of the abdominal wall. N.B. The Umbilicus is a consolidated scar representing the site of attachment of the umbilical cord in the fetus. It is situated in the linea alba slight below it.

23. Veins of the Anterior Abdominal wall Superficial Veins They form a network that radiates out from the umbilicus. Above, the network is drained into the axillary vein via the lateral thoracic vein. Below, the network is drained into the femoral vein via the superficial epigastric & great saphenous veins. A few small veins, the paraumbilical veins connect the network through the umbilicus & along the ligamentum teres to the portal vein. This forms an important portal – systemic venous anastomosis. Deep veins They are the superior epigastric, inferior epigastric and deep circumflex iliac veins. They drains into the internal thoracic & external iliac veins. The posterior intercostal veins drain into the azygos veins. The lumbar veins drain into inferior vena cava.

24. Lymph Drainage of the Anterior Abdominal Wall The skin above the level of the umbilicus is drained upward to the anterior axillary ( pectoral ) group of nodes which can be palpated just beneath the lower border of the pectoralis major muscle. Below the level of the umbilicus, the lymph drains downward & laterally to the superficial inguinal nodes. The lymph of the skin of the back above the level of the iliac crests drains upward to the posterior axillary nodes which are palpated on the posterior wall of the axilla. Below the level of the iliac crests, they drain downward to the superficial inguinal ns Deep Lymph Vessels They drain into the internal thoracic, external iliac, posterior mediastinal and para- aortic.

25. Clinical Notes 1- Umbilical Herniae A- Congenital hernia ( exomphalos) or omphalocele: It is caused by a failure of part of the midgut to return to the abdominal cavity from the extraembryonic coleom during fetal life. B- Acquired infantile hernia it is caused by a weakness in the scar of the umbilicus in the linea alba. Most disappear as the abdominal cavity enlarges without treatment. C- Acquired umbilical of adults (paraumbilical hernia) The hernial sac protrudes through the linea alba in the region of the umbilicus. It gradually increase in size and hang downward. The neck of the sac may be narrow but the body of the sac contains coils of small and large intestine and omentum. It is more common in female than male 2- Incisional Hernia A- It is caused to cut one of the segmental nerves supplying the muscles of the anterior abdominal wall. B- Infection with death( necrosis) of the abdominal musculature. The neck of the sac is large and adhesion & strangulation of its contents are rare. c c

26. Clinical notes 3- Epigastric Hernia It occurs through the widest part of the linea alba, any where between the xiphoid process & umbilicus. It starts off as a small protrusion of the extraperitoneal fat between the fibers of the linea alba. Then fat is forced through the linea alba and trags behind it a small peritoneal sac. The body of the sac contains a small piece of greater omentum. 4- Separation of the recti abdominis It occurs in elderly multiparous women with weak abdominal muscles. The aponeuroses forming the rectus sheath become stretched. The hernial sac, containing abdominal viscera bulges forward between the medial margins of the recti during cough or strains. This can be corrected by wearing a suitable abdominal belt.

27. 5- Hernia of the Linea Semilunaris ( SPIGELIAN Hernia ) It is uncommon. It occurs through the aponeurosis of the transversus abdominis just lateral to the edge of the rectus sheath. It occurs just below the level of the umbilicus. The neck of the sac is narrow, so that the adhesion and strangulation of its contents are common complications. 6- Lumbar Hernia It occurs through the lumbar triangle ( Petit’s triangle ) and is rare. It is bounded anteriorly by the posterior margin of the external obligue muscle and posteriorly by the anterior border of latissimus dorsi muscle and inferiorly by the iliac crest. The floor is formed by the internal oblique and transversus abdominis muscles. The neck of the hernia is large and the incidence of strangulation low.

28. Anterior Abdominal Nerve Block Area of Anesthesia : The skin of the anterior abdominal wall. Indications : Repair of laceration of the anterior abdominal wall ---- Procedure : see figure 4- 16. Abdominal Pain – Muscle Rigidity and Referred Pain The rigidity of the muscles may be due to inflammation of the parietal peritoneum or due to physician’s hand is cold. The patient lies supine and rest the arms by the sides and draw up the knees to flex the hip joints. Dermatomes over: the xiphoid process T7 the umbilicus T10 the pubis L1