[0:21]Good morning. This is Dr. Adel Bondok, Professor of Anatomy and Neuroscience, Mansoura University, Egypt. Today I will talk about the structure and layers of the anterior abdominal wall. I will talk about the bony landmarks, the surface landmarks, the structure and layers, the arterial supply, venous drainage, nerve supply, and lymph drainage of the anterior abdominal wall. Start by the bony landmarks.
[0:51]Okay. First, this is the Xiphoid process. Okay. And then, this is the costal margin formed by the costal cartilages number seven, number eight, number nine, and number 10. And then, iliac crest, this is the iliac crest and the anterior superior iliac spine, and this is the pubic tubercle and this is the pubic crest. And then, the pubic synthesis. So from above Xiphoid process and costal margin. From below, iliac crest, anterior superior iliac spine, pubic tubercle, pubic crest, and pubic synthesis. Regarding the surface landmarks of the anterior abdominal wall, this is the first landmark, the umbilicus. And then, this line is the second landmark, the linea alba. The linea alba is a tendinous line, formed by the decussation of the aponeurosis of the muscles of the anterior abdominal wall of the two sides. It extends from the xiphoid process to the pubic symphysis. And then, superiorly, this is the costal margin, and again, it is formed by the costal cartilages, number seven, number eight, number nine, and number 10. And then, inferiorly, this is the iliac crest and this is the anterior superior iliac spine. And then, this ligament is the inguinal ligament. The inguinal ligament extends from the anterior superior iliac spine to the pubic tubercle and the pubic crest and this is the spermatic cord. Okay. Start by the structure of the anterior abdominal wall. What are the structures forming the anterior abdominal wall? Of course, the first one is the skin. And then the fascia. Superficial fascia, because actually, we don't have deep fascia in the anterior abdominal wall. The superficial fascia is formed of two layers. Fatty layer. This is the outer fatty layer and inner membranous layer. And then muscles. Talk about them. This is the muscle layer after the fascia. And then, the blood vessels. The nerves. And the lymphatics. So the anterior abdominal wall is formed of the skin, superficial fascia, muscles, vessels, nerves, and lymphatics. Regarding the layers of the anterior abdominal wall, this is a section of the anterior abdominal wall. The layers from outside, of course, the first layer is the skin. This one. Second layer is the superficial fascia. And the superficial fascia is formed of two layers: fatty layer and membranous layer. There is no deep fascia. And after the fascia, the muscle layer. And the muscle layer is formed of three layers. The outer layer is the external oblique. The middle layer is the internal oblique. And the inner layer or the deep layer is the transversus abdominis. Each muscle begins by fleshy fibers and ends by aponeurosis. The aponeurosis of one side, decussates with the aponeurosis of the other side in the midline to form the linea alba. This is the linea alba. After the muscle layer, there is a fascia lining the transversus abdominis. It is the transversalis fascia. And then a layer of fat, extraperitoneal fat, and then the parietal layer of the peritoneum. So six layers: skin, superficial fascia, and then muscle layer formed of three layers: external oblique, internal oblique, and transversus abdominis. Then transversalis fascia, then extraperitoneal fat, and parietal layer of the peritoneum. See another photo. This is the anterior abdominal wall. Okay? So the first layer is the skin. Second layer is the superficial fascia. And the superficial fascia is formed of two layers: superficial fatty layer and deep membranous layer. There is no deep fascia. And after the superficial fascia, the muscle layer. The muscle layer is formed of three layers: external oblique, internal oblique, transversus abdominis. Then a layer of fascia lining the transversus abdominis. It is the transversalis fascia. Then extraperitoneal fat, and then parietal layer of the peritoneum. So in order to open the anterior abdominal wall, you have to cut the skin, then the superficial fascia, then the muscle layer, then the transversalis fascia, the extraperitoneal fat and the parietal layer of the peritoneum. Let us talk about the skin. This is the skin of the anterior abdominal wall and these are Langer's lines or cleavage lines. So the first landmark of the skin is that the cleavage lines or Langer's lines run horizontally. What is the clinical importance of this horizontal direction?
[7:02]Langer's lines first are formed by collagen fibers within the dermis. Incision along the lines heals with a minimal scar. So it is better to open the skin along along or parallel to the cleavage lines or Langer's lines. On the other hand, incision across the cleavage lines leaves an ugly scar.
[7:43]So regarding the skin, the skin has cleavage lines. These cleavage lines run horizontally. And these cleavage lines are formed of collagen fibers in the dermis. The clinical importance of the direction is that incision along or parallel to the cleavage lines leaves a minimal scar. And incision across cleavage lines leaves an ugly scar. Then the superficial fascia is formed of two layers: outer fatty layer, called Camper's fascia, and inner membranous layer, called Scarpa's fascia. This Scarpa's fascia is continuous with Colles' fascia of the perineum. There is no deep fascia. Why the anterior abdominal wall doesn't contain deep fascia? To allow free movement of the anterior abdominal wall during respiration. Then the anterior abdominal wall muscles. There are five anterior abdominal wall muscles. Three oblique and two vertical. So three oblique and two vertical muscles. The three oblique. The outer layer is the external oblique. The middle layer is the internal oblique. The inner layer or the deep layer is the transversus abdominis. These muscles have different directions of fibers. Why?
[9:21]First, the external oblique. The fibers of the external oblique are directed downward and medially. The fibers of the internal oblique are directed upward and medially. So external oblique, downward and medially, internal oblique, upward and medially. The transversus abdominis. The fibers of the transversus abdominis are directed horizontally. Why? To strengthen the anterior abdominal wall and prevent hernia formation. So the three oblique muscles: external oblique, outer layer, internal oblique, middle layer, transversus abdominis, deep layer. Each muscle begins by fleshy fibers and ends by aponeurosis. The aponeurosis of one side decussates with the aponeurosis of the other side to form the linea alba. The three muscles have different direction of fibers. The external oblique, the fibers of the external oblique are directed downward and medially. The internal oblique, directed upward and medially. The transversus abdominis are directed horizontally. Why? To strengthen the anterior abdominal wall and prevent hernia formation. The two vertical muscles. The first one on each side of the midline, the rectus abdominis muscle, the second one is called pyramidalis. And this pyramidalis it may be absent. I will talk about the muscles in another lecture.
[10:57]Let us see some some landmarks in the anterior abdominal wall. This is the first landmark. Okay, this is the costal margin. And this is the linea alba. Linea alba, tendinous line in the midline, extending from the Xiphoid process to the pubic symphysis, and it is formed by the decussating aponeurosis of the abdominal muscles.
[11:21]Linea semilunaris is the lateral margin of the rectus abdominis muscle. Inguinal ligament is the lower border of the external oblique aponeurosis. And then this is the arcuate line. It is the lower border of the internal oblique and transversus abdominis aponeurosis. And it is located midway between the umbilicus and the pubic symphysis. Then McBurney's point and McBurney's incision.
[12:05]Okay. So what are the ribs forming the costal margin? Okay, number seven, number eight, number nine, and number 10. What are Langer's lines? Langer's lines are called cleavage lines. And they correspond to the direction of the collagen fibers within the dermis. What is the clinical importance? Incision parallel to the cleavage lines, okay, leaves minimal scar. Incision across cleavage lines leaves ugly scar. And what is the direction? Horizontal direction. Okay? What is linea alba? It is a tendinous line in the midline, running between the Xiphoid process and pubic symphysis, and it is formed by the decussating aponeurosis of the muscles of the two sides. What is linea semilunaris? It is the lateral border of the rectus abdominis muscle. What is the arcuate line? It is the lower border of the internal oblique and transversus abdominis aponeurosis.
[13:09]Okay. What is McBurney's point and McBurney's incision? This is McBurney's point. It is the surface landmark for the base of the vermiform appendix. What is McBurney's incision? It is incision along McBurney's point for appendectomy. Okay, how do you locate it?
[13:30]Draw a line between the umbilicus and the anterior superior iliac spine. This point is at the junction of the medial two thirds and the lateral one third of this line. Between umbilicus and anterior superior iliac spine. Okay, this is a true fact.
[13:52]Then arterial supply of the anterior abdominal wall. Anterior abdominal wall is supplied by nine arteries. The nine arteries are three superficial arteries and six deep arteries. The three superficial arteries, these are the three superficial arteries. This is the first one. Superficial epigastric artery, running upward towards the umbilicus. This is the second one, superficial. Okay, superficial external pudendal artery. It is running medially to the external genital organs. This is the third one, superficial circumflex iliac artery. It is running laterally to the iliac crest. These three arteries are branches from the femoral artery. So, three superficial arteries: superficial epigastric artery, superficial external pudendal artery, superficial circumflex iliac artery, branches from the femoral artery. Now the six deep arteries. The six deep arteries are two arteries from above, two arteries from below, and two arteries from the side. Okay? Two arteries from above. They are branches from the internal thoracic artery, which is a branch from the subclavian artery. Okay? The two branches are: superior epigastric and musculophrenic artery. The superior epigastric artery enters the rectus sheath. The musculophrenic artery runs along the costal margin. Then two from below. These two are branches from the external iliac artery. Okay? This is the first one: inferior epigastric artery. Entering the rectus sheath. And this one, the deep circumflex iliac artery, going to the iliac crest.
[15:52]And from the side, two: posterior intercostal arteries. Okay, from the aorta, posterior intercostal arteries and lumbar arteries. The superior epigastric artery anastomoses with the inferior epigastric artery. Therefore, the anastomosis between the superior epigastric artery and inferior epigastric artery connects the subclavian artery with the external iliac artery. Again, three superficial arteries and six deep arteries. These are the three superficial arteries from the femoral artery. This is the first one, superficial epigastric artery, going to the umbilicus. This is the second one, superficial circumflex iliac artery, going to the iliac crest. This is the third one, superficial external pudendal artery, going to the external genitalia. Okay?
[17:01]The three arteries are branches from the femoral artery. Then the deep arteries. Two from above, two from below, and two from the side. Two from above. This is the superior epigastric artery entering the rectus sheath. And this is the musculophrenic artery. Two from below, inferior epigastric artery. And deep circumflex iliac artery. And these are branches from the external iliac artery. Look at the anastomosis between the superior epigastric artery and inferior epigastric artery. This anastomosis connects the subclavian artery with the external iliac and femoral arteries. Two from the side: intercostal and lumbar arteries.
[17:53]Regarding the inferior epigastric artery. This inferior epigastric artery is a branch from the external iliac artery. It has a very important relation. It lies medial to the deep inguinal ring. That's why the inferior epigastric artery lies deep to the oblique inguinal hernia. This inferior epigastric artery enters the rectus sheath. And anastomoses with the superior epigastric artery. It has two branches. This is the first branch, called pubic branch. This pubic branch anastomoses with the pubic branch of the obturator artery. In 30% of the population, this pubic branch may enlarge and replaces the obturator artery and is called abnormal obturator artery. So what is the normal obturator artery? The normal obturator artery is the enlarged pubic branch of the inferior epigastric artery. What is the clinical importance of this pubic branch? This pubic branch is related to this ring. This is the femoral ring. And you know that the femoral ring gives the passage to femoral hernia. And this is the lacunar ligament. In operations of the femoral hernia, this artery may be injured leading to severe bleeding. So the clinical importance of the pubic branch of the inferior epigastric artery is that it is related to the femoral canal and femoral ring. And this artery may be injured in operations of the femoral hernia. Second branch is this one. It's called the cremasteric artery. This cremasteric artery passes through the deep inguinal ring to supply the cremasteric muscle. Regarding the venous drainage. Again, we have superficial veins and deep veins. Regarding the superficial veins, these are the superficial veins of the anterior abdominal wall. They drain into three sites or three directions. Upward, superiorly to the lateral thoracic vein. This is the lateral thoracic vein, which drains into the axillary vein. So, the upward termination of the superficial veins to the lateral thoracic vein to the axillary vein.
[20:35]Inferiorly to the superficial epigastric vein. This superficial epigastric vein terminates in the great saphenous vein, and the great saphenous vein terminates into the femoral vein. And then medially. Okay. Before medially, the superficial epigastric vein and the lateral thoracic vein form anastomotic channel. This anastomotic channel, called thoracoepigastric vein. This thoracoepigastric vein connects the axillary vein with the femoral vein. This anastomosis is very important in superior vena cava obstruction because this vein will be dilated. And then medially, medially, it is drained into the paraumbilical veins. These paraumbilical veins drain into the portal vein. Again, the superficial veins drain into three directions: superiorly into the lateral thoracic vein, to the axillary vein. Inferiorly, superficial epigastric vein, great saphenous vein, femoral vein. Medially, paraumbilical veins and then the portal vein. What is the clinical importance of the drainage into the portal vein? In liver cirrhosis and in portal hypertension, this anastomosis, these veins around the umbilicus, become dilated to form what is called Caput Medusae. So Caput Medusae formed of dilated veins radiating from the umbilicus due to portal hypertension, due to liver cirrhosis. Then regarding the deep veins. These are the superficial veins and these are the deep veins. Regarding the deep veins again, six deep veins, similar to the six deep arteries. Superiorly, we have two veins here. So superior epigastric vein and musculophrenic vein. They drain into the internal thoracic vein. This is the internal thoracic vein, and the internal thoracic vein drains into the brachiocephalic vein. So superiorly, superior epigastric vein and musculophrenic vein drain into the internal thoracic vein. Inferiorly, the inferior epigastric vein and the deep circumflex iliac vein drain into the external iliac vein. And then posterior intercostal veins drain into the azygos vein and the lumbar veins drain into the inferior vena cava. Regarding the nerve supply of the skin and muscles of the anterior abdominal wall. The anterior abdominal wall is supplied by the lower six thoracic nerves from T7 to T12 and two branches from L1, iliohypogastric and ilioinguinal nerves. So nerve supply lower six thoracic nerves from T7 to T12 and iliohypogastric and ilioinguinal nerves L1. Regarding the dermatomes of the anterior abdominal wall. The level of the Xiphoid process is supplied by T7. The level of the umbilicus is supplied by T10. And the level the suprapubic region, the level of the suprapubic region, L1. So the dermatome of the area of the Xiphoid process is T7. The dermatome of the umbilicus is T10. The suprapubic region is L1.
[24:30]And finally, lymph drainage of the anterior abdominal wall. Lymph drainage of the anterior abdominal wall, skin and deep structures. Regarding the skin, this is the umbilicus. So we have lymph drainage above the umbilicus and below the umbilicus. Above the umbilicus, drain into the axillary lymph nodes, the pectoral group or the anterior group of the axillary lymph nodes. Below the umbilicus, they drain into the superficial inguinal lymph nodes. Regarding the deep structures, along the arteries.
[25:42]So along the branches of the internal thoracic artery to the internal thoracic lymph nodes. And drain along the branches of the external iliac artery to the external iliac lymph nodes. And drain along the branches of the aorta to the paraaortic lymph nodes. So lymph drainage of the anterior abdominal wall. Skin and deep structures. Skin, above the umbilicus, pectoral group of the axillary lymph nodes. Below the umbilicus, superficial inguinal lymph nodes. Regarding the deep structures, along the branches of the internal thoracic artery to the internal thoracic lymph nodes. Along the branches of the external iliac artery to the external iliac lymph nodes. And drain along the branches of the aorta to the paraaortic lymph nodes. And thank you very much. Best wishes and good luck.
