Video: Blood vessels of the abdominal wall
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Have you ever heard about Medusa? Yes -- that somewhat monstrous Greek mythological lady who had scales for skin and snakes for hair and used to turn people into stone just by looking at them. Pret... Read more
Have you ever heard about Medusa? Yes -- that somewhat monstrous Greek mythological lady who had scales for skin and snakes for hair and used to turn people into stone just by looking at them. Pretty scary. Well, Medusa might be long gone into the past but her name lives on -- well, at least in anatomy. Find out more as we explore the vessels of the abdominal wall.
First, let's take a run-through of what we're going to cover in this tutorial. We'll start by looking at the abdominal wall and explore its functions and subdivisions. Then we're going to move into the main topic of this tutorial which is the vessels of the abdominal wall, starting with the anterolateral wall. Here we're going to describe first the arteries and then the veins of this subdivision of the abdominal wall. After that, we're going to describe the vessels of the posterior wall following the same format -- first the arteries and then the veins. Finally, we'll take a look at the clinical sign named after Medusa that usually indicates that something is wrong with our liver.
So without further ado, let's start talking about the abdominal wall.
So we know that the abdomen is the region of the trunk that lies between the thorax and pelvis. It consists of the abdominal wall, a multi-layered structure that consists partly of bone but mainly of muscle which surrounds and encloses the second compartment of the abdomen -- the abdominal cavity. This cavity is limited above by the diaphragm and below by the pelvic inlet. The abdominal cavity is, of course, literally packed with major organs and other structures.
The abdomen is primarily a soft tissue region with very little bony framework. Therefore, an intact abdominal wall is essential for protecting and supporting the abdominal viscera. The abdominal wall is also critical for the stabilization and rotation of the trunk. In addition, when the muscles of the abdominal wall contract, they increase intraabdominal pressure which is essential for physiological processes like voiding of the urinary bladder and rectum, in giving birth, as well as coughing and vomiting.
As you can see in this cross-section of the abdomen, the abdominal wall can be divided into two main subdivisions -- the anterolateral wall and posterior abdominal wall. The anterolateral abdominal wall spans the anterior and lateral sides of the abdomen. This wall consists of four main layers from superficial to deep -- skin, superficial fascia or subcutaneous tissue, muscles and associated deep fascia, and parietal peritoneum. If you remove the anterolateral wall and the abdominal contents, you'll find the posterior abdominal wall. This wall is formed by the lumbar vertebrae, pelvic girdle, posterior abdominal muscles, and their associated fascia.
Now that we have a general picture of the abdominal wall structure, function, and subdivisions, it's time to get to the main subject of this tutorial -- the blood vessels of the abdominal wall. But before we dive in to take a look at the intricate branches and tributaries that supply and drain the abdominal wall, let's take a quick look at the main parent arteries which supply this region.
All the blood vessels in the abdominal wall can be traced back or forward to one of a few major blood vessels or one of their larger branches. So before we look at a specific region, let's learn about these vessels.
The arterial supply of the abdominal wall stems from a number of parent arteries; namely, the aorta, the subclavian artery, the common iliac and external iliac arteries, and finally, the femoral artery.
The aorta is the largest artery in the body and through its numerous branches provides the arterial supply to the abdominal wall. It originates directly from the heart and consists of three parts -- the ascending aorta, the arch of the aorta, and the descending aorta. Part of the descending portion is located in the thorax and is named the thoracic aorta, and part is located in the abdomen and is thus named the abdominal aorta. The abdominal aorta gives off a number of branches that provide arterial supply to both the anterior and posterior abdominal wall.
Arising from the arch of the aorta directly on the left and indirectly via the brachiocephalic trunk on the right is the subclavian artery. The subclavian artery mainly provides an arterial supply to both the thoracic and cervical regions; however, it gives off a branch known as the internal thoracic artery which contributes to the arterial supply of the abdominal wall via its branches. At the lower level of vertebra L4, the descending aorta divides into the right and left common iliac arteries. The common iliac arteries further bifurcate to form internal and external iliac arteries. The external iliac artery descends towards the thigh where it becomes known as the femoral artery at the level of the inguinal ligament. The external iliac and femoral arteries provide numerous branches which supply the lower portion of the abdominal wall.
Moving on to the major veins of the abdominal wall, we meet the inferior vena cava. The inferior vena cava is the largest vein of the human body. It is located at the posterior abdominal wall to the right of the aorta. The inferior vena cava returns venous blood from the lower limbs and abdominopelvic region to the heart. It receives tributaries from the femoral vein and external iliac vein via the common iliac vein.
From this lateral view, we can see that the superior vena cava also receives venous drainage from the regions of the abdomen via the azygos and brachiocephalic veins. The azygos and brachiocephalic veins receive venous blood from the abdominal wall through the ascending lumbar and internal thoracic veins which we'll meet later on. The superior vena cava is contained in the superior thorax and ends at the level of the third costal cartilage.
Now that we have identified the origins of the arterial supply and terminal veins of the thoracic wall, let's explore the branches and tributaries that supply this region of the human body, starting with the anterolateral abdominal wall.
The branches and vascular supply of the anterolateral abdominal wall can be divided up according to three regions or zones. Zone 1 constitutes the epigastrium and central portion of the anterior abdominal wall, overlying the rectus abdominis muscle. Vessels that supply Zone 1 includes the superior and inferior epigastric arteries. Zone 2 lies just below Zone 1 and is made up of the lower portion of the anterior abdominal wall below the umbilicus. The region of the anterolateral abdominal wall is mainly supplied by the superficial epigastric, superficial external pudendal, superficial circumflex iliac, and deep circumflex iliac arteries. Finally, Zone 3 is located lateral to Zone 1 and is mainly supplied by the musculophrenic artery, lower intercostal, subcostal, and lumbar arteries. We'll take a closer look at the arteries which supply each of these zones next, beginning with Zone 1.
The superior epigastric artery is a terminal branch of the internal thoracic artery. It runs within the rectus sheath behind the rectus muscle which was removed from this image and supplies the superior part of the deep anterolateral abdominal wall of Zone 1. Perforating branches pierce through the anterior rectus sheath to provide cutaneous supply to the abdominal skin. From this right lateral perspective, we can see this artery branching from the internal thoracic artery and descending along the anterior abdominal wall.
Next we meet the inferior epigastric artery, a branch of the external iliac artery, which supplies the inferior part of this wall. Similar to its superior counterpart, it also gives off perforating branches which provide cutaneous supply to skin of the abdominal wall from the most inferior portion of Zone 1 up to the umbilicus. The inferior epigastric artery enters the rectus sheath and ends by anastomosing with the superior epigastric artery.
Now that we've met the arteries that supply Zone 1, let's take a look at the arterial supply of Zone 2, beginning with the three most proximal branches of the femoral artery.
The first is the superficial epigastric artery. From its origin point, it travels anteriorly and pierces the cribriform fascia before ascending anterior to the inguinal ligament. It travels within the subcutaneous tissue of the anterior abdominal wall to reach and supply the inferior part of the superficial anterolateral abdominal wall below the umbilicus. This vessel terminates by anastomosing with the branches of the inferior epigastric artery.
Moving on to the second branch of the femoral artery, we come to the superficial external pudendal artery. This artery travels in an anteromedial direction anterior to the spermatic cord in males or the round ligament of the uterus in females to supply the skin of the lower anterolateral abdominal wall at the base of Zone 2.
The third and final branch of the femoral artery of interest to us today is the superficial circumflex iliac artery. This vessel travels parallel to the inguinal ligament from its origin to supply the inferior portion of the superficial anterolateral abdominal wall. It often arises via a common trunk with the superficial epigastric artery which we just looked at.
The final artery supplying Zone 2 of the anterolateral abdominal wall is the deep circumflex iliac artery. This paired artery arises from the external iliac artery and runs laterally towards the anterior superior iliac spine and ascends in an anterolateral direction. About halfway along the iliac crest, the deep circumflex iliac artery pierces the aponeurosis of the transversus abdominis muscle and runs deep to the internal oblique muscle to supply the inferior portion of the deep anterolateral abdominal wall.
Moving on to the arteries which supply Zone 3 of the anterolateral abdominal wall, we meet the musculophrenic artery, which is visible from this lateral view. This artery supplies the superior part of the superficial lateral abdominal wall. It originates as one of the terminal branches from the internal thoracic artery which you can see better in this image here. It runs inferiorly along the anterior chest wall and gives off anterior intercostal arteries to the 7th to 9th intercostal spaces as well as fine branches to the superior part of the rectus abdominis muscle.
Supplying the superior part of the anterolateral abdominal wall are the 10th and 11th posterior intercostal arteries, which we can see from this posterior view. These arteries arise directly from the posterolateral surface of the thoracic aorta, as we can see here from this lateral perspective. They course along the inferior border of their numerically equivalent rib before continuing medially to the anterolateral abdominal wall between the transversus abdominis and internal abdominal oblique muscles after they pass the sternal end of the ribs.
The subcostal artery similarly branches from the posterior surface of the thoracic aorta and travels below the 12th rib to supply the lateral part of the abdominal wall. As it extends anteriorly around the rib cage, the paired arteries traverse the posterior edge of the transversus abdominis muscle and pierce through its aponeurosis. The subcostal artery continues between the internal abdominal oblique and transversus abdominis muscles terminating close to the rectus abdominis muscle.
The final group of arteries which supply the anterolateral abdominal wall are the lumbar arteries. The four lumbar arteries originate from each posterolateral side of the abdominal aorta. These arteries arise in series and travel alongside the lower posterior intercostal and subcostal arteries. They pierce the aponeurosis of the transverse abdominis muscle before giving off several muscular branches which supply structures of the lateral portion of the anterolateral abdominal wall.
Now let's take a look at the venous drainage of the anterolateral abdominal wall, starting with the superficial veins.
The superficial veins form a network known as the subcutaneous venous plexus that radiates out from the umbilicus. This subcutaneous venous plexus drains regions of the thoracic wall superiorly and medially to the axillary vein via the thoracoepigastric and lateral thoracic veins and regions of the abdominal wall inferiorly and laterally to the femoral vein via the superficial epigastric vein. As we can guess by its location, it collects blood from the lower and medial parts of the anterior abdominal wall and empties into the femoral vein or great saphenous vein.
The superficial circumflex iliac vein originates superficially within the superficial fascia of the inguinal region. It collects blood from the inguinal region and lower portion of the anterolateral abdominal wall. From its origin point, it extends along the inguinal ligament and descends to drain into the great saphenous or femoral vein.
The thoracoepigastric vein runs along the lateral aspect of the trunk between the lateral thoracic vein above and the superficial epigastric vein below. This vein functions to drain regions of the thoracic wall; however, as we saw a moment ago, the lateral thoracic vein is a tributary of the axillary vein and the superficial epigastric vein is a tributary of the femoral vein. So the thoracoepigastric vein is a relatively direct superficial anastomotic channel that establishes important communication between the axillary vein, a tributary of the superior vena cava, and the femoral vein, a tributary of the inferior vena cava. It therefore also plays a role in draining regions of the abdominal wall by connecting regions drained by both the inferior and superior vena cava. This may provide a collateral circulation pathway during obstruction or compression of either vena cava.
So imagine that your inferior vena cava becomes obstructed or maybe just compressed due to an abdominal malignancy. The venous blood can return to the superior vena cava and then the heart through this venous communication. That's why this is called a cavocaval anastomosis.
The deep veins of the abdominal wall follow their associated arteries. The superior epigastric vein carries venous blood from the superior part of the anterior abdominal wall and part of the diaphragm and drains into the internal thoracic vein. The inferior epigastric vein carries venous blood from the inferior part of the anterior abdominal wall. This vein is a tributary of the external iliac vein. There is an anastomosis or connection between the superior and inferior epigastric veins, as is visible here. This anastomosis also provides a place of collateral circulation in case of either vena cava obstruction.
In this superior view of the abdominal cavity, we can see the deep circumflex iliac vein. This vein collects blood from the lower part of the lateral abdominal wall. It courses medially with its companion artery, the deep circumflex iliac artery, parallel to the inguinal ligament and empties into the external iliac vein.
The last two posterior intercostal veins and the subcostal vein also contribute to the venous drainage of the lateral part of the abdominal wall. They empty into the azygos vein on the right and the hemiazygos vein on the left which are these vessels here ascending through the posterior thoracic wall and ultimately emptying into the superior vena cava.
Okay, now that you know everything about the vessels of the anterior abdominal wall, it's time to move on to the vessels of the posterior abdominal wall.
Most of the arterial branches that supply the posterior abdominal wall are derived from the abdominal aorta. An exception to this rule is the subcostal artery which is derived from the thoracic aorta being the lowest of its branches. We've actually already mentioned this artery when discussing the arteries of the anterolateral wall; however, this artery also contributes to the vascularization of the posterior abdominal wall.
Finally, let's talk about the lumbar arteries which we already met at the anterolateral abdominal wall. There are usually four in number on either side and arise from the posterolateral aspect of the aorta opposite the bodies of the upper four lumbar vertebrae. As we have already seen, these arteries arise in series with the posterior intercostal arteries and their main function is to provide the blood supply for the lumbar segments of the spinal cord, posterior abdominal wall, and the lumbar structures of the back.
All right, it's time to look at the veins of the posterior abdominal wall.
The lumbar veins are four pairs of blood vessels that drain the posterolateral abdominal wall as well as the lumbar segments of the spinal cord and lumbar structures of the back. They usually empty into the inferior vena cava. In this posterior perspective, we can have a better view of anatomy and course of the lumbar veins. Ipsilateral lumbar veins are interconnected by ascending lumbar veins, one on each side of the vertebral column. The ascending lumbar veins drain regions of the posterolateral abdominal wall and unite with the ipsilateral subcostal veins to form the azygos vein on the right and hemiazygos vein on the left, which ultimately drain into the superior vena cava. The ascending lumbar veins also communicate inferiorly with the common iliac veins thus establishing an alternative pathway for the drainage of the pelvis, spinal cord, and lower limbs in case of an inferior vena cava obstruction.
All right, it's time to find more about that clinical pathology named after Medusa.
Cutaneous veins surrounding the umbilicus anastomose or connect with paraumbilical veins and we can see this in our image here. These paraumbilical veins are small tributaries of the hepatic portal vein which run within the round ligament of the liver which in turn runs from the umbilicus. As you may already know, the portal venous system transmits deoxygenated blood from most of the gastrointestinal tract and gastrointestinal organs to the liver and onto the inferior vena cava. So this connection between the paraumbilical veins and the superficial veins around the umbilicus forms an important collateral communication channel between the portal and the systemic venous system called the portosystemic or portocaval venous anastomosis.
This anastomosis provides a bypass for venous blood from the portal venous system through the liver allowing venous blood from the gastrointestinal tract to still reach the heart through the inferior vena cava without going through the liver. When blood is redirected from the hepatic portal system, and we will see why this happens in a moment, the superficial veins around the umbilicus and the paraumbilical veins become grossly distended or varicosed. The distended subcutaneous veins radiate out from the umbilicus producing, in severe cases, the clinical sign referred to as caput medusae. The name caput medusae, Latin for head of Medusa, originates from the apparent similarity to Medusa's head which we know bore venomous snakes in place of hair.
Caput medusae is a sign of portal hypertension, an abnormally increased pressure in the portal vein and its tributaries that can be a result of various disorders. The most common cause of portal hypertension is cirrhosis, a late stage of scarring or fibrosis of the liver caused by many forms of liver diseases and conditions such as hepatitis and chronic alcoholism. Treatment options depend on the underlying disease.
Thanks so much for sticking with me throughout this tutorial. To finish off, let's review what we've covered today.
We started by looking at the structure of the abdominal wall, a layered structure that consists partly of bone but mainly of muscle. Its functions include protection and support of the abdominal viscera, stabilization and rotation of the trunk, and increasing intraabdominal pressure during micturition, defecation, childbirth, coughing, and vomiting. We also saw that the abdominal wall can be divided into two main subdivisions -- the anterolateral and the posterior abdominal wall.
Then we moved on to the main topic of this tutorial -- the vessels of the abdominal wall -- starting with the anterolateral wall. We divided the arterial supply of the anterolateral abdominal wall into zones. Arteries supplying Zone 1 of the anterolateral abdominal wall include the superior and inferior epigastric vessels. Arteries supplying Zone 2 of the anterolateral abdominal wall include the superficial epigastric, superficial circumflex iliac, and superficial external pudendal arteries. Onto Zone 3, we met the musculophrenic, lower intercostal, subcostal, and lumbar arteries.
We then described the veins draining the anterolateral abdominal wall; most of them have the same name as their companion arteries. At a more superficial level, we looked at the superficial epigastric vein, the superficial circumflex iliac vein, and the thoracoepigastric vein. Moving deeper, we discussed the superior epigastric vein, the inferior epigastric vein, the deep circumflex iliac vein from this anterior view, the posterior intercostal veins, and the subcostal vein.
Next we examined the vessels of the posterior abdominal wall, starting with the arteries. Here, the arterial supply comes from the abdominal aorta and some of its branches, namely, the subcostal arteries and the lumbar arteries. Finally, we looked into the veins of the posterior abdominal wall where we identified the lumbar veins which are interconnected by the ascending lumbar veins.
At the end of our tutorial, we discussed the clinical sign known as caput medusae, a sign of an abnormally increased venous pressure in the portal venous system that can be observed in patients with liver disease.
And that's it for today. Hope you enjoyed this video. Happy studying and see you next time.