Fasciae and Ligaments of the Abdominal Wall
The abdomen is the region of the trunk between the thorax and the pelvis. It is a flexible dynamic container, housing most of the organs of the digestive system and part of the urogenital system. Those structures are contained in its cavity, the abdominal cavity.
The abdominal cavity is bounded superiorly by the thoracic diaphragm. Inferiorly, it has no floor of its own as it is continuous with the pelvic cavity. The inferior boundary of the abdominal cavity is considered to be the pelvic inlet. The cavity is defined by the musculoaponeurotic anterolateral abdominal walls, and posteriorly, by a posterior abdominal wall, which includes the lumbar vertebral column.
The musculoaponeurotic abdominal walls are composed of several layers of abdominal muscles, e.g., the external oblique, internal oblique, and transverse abdominal muscles, which are partitioned into layers by investing (or deep) fascia.
There are also superficial fasciae overlying the muscular layers of the abdominal wall. These superficial fasciae are superficial fatty layers of subcutaneous tissue, for example, the Camper’s fascia of the anterolateral abdominal wall.
Investing the internal surfaces of the muscular layer is a third group of abdominal fascia called the endoabdominal (or intra-abdominal) fascia which is of important clinical significance, forming an important landmark in surgery.
Completing the abdominal wall, after the intra-abdominal fascia layer, is a layer of extraperitoneal fat and finally the parietal peritoneum which lines the abdominal cavity and contains the abdominal viscera. Various folds or reflections of the peritoneum connect viscera to the abdominal walls or to one another. Some of these are properly called folds, for example the omentum (greater and lesser omentum), some are called mesenteries and others ligaments. A peritoneal ligament consists of a double layer of peritoneum (serous membrane lining the abdominal cavity) that connects an organ with another organ to the abdominal wall.
Overlying the muscular layers of the abdominal wall are two layers of fatty tissue, forming the subcutaneous tissue. These subcutaneous tissues make up the superficial fascia of the abdominal wall, but change their names at the level of the umbilicus to Camper’s fascia (superficially) and Scarpa’s fascia. The latter is a deep membranous layer closely opposing the deep or investing fascia which continues inferiorly into the perineal region as the superficial perineal fascia (or Colles’ fascia) and terminates before reaching the thigh.
The deep or investing fasciae of the abdominal walls are made up of three layers:
They respectively invest each of the three muscular layers of the abdominal wall directly. They attach to the external aspects of the muscle layers and their aponeuroses, making the separation from one another difficult.
The intra-abdominal or the endoabdominal fascia is a membranous sheet of varying thickness lining the internal aspect of the deep muscular layer of the abdominal wall. It has two layers, a relatively firm one lining the deep surface of the deepest muscular layer of abdominal wall, called the transversalis fascia and a second layer which blends with the parietal peritoneum. The second one is more flexible than the transversalis fascia. Between these two layers there is a variable amount of adipose tissue, the extraperitoneal fat.
Attached to the parietal peritoneum of the abdominal wall are double layered folds called peritoneal ligaments. These ligaments hold viscera to the abdominal walls and two or more viscera together. These abdominal ligaments are mostly named according to the structures they hold.
They include the suspensory ligaments of the liver (right and left triangular ligaments, falciform ligament) and the peritoneal ligaments of the stomach (splenorenal ligament, gastrosplenic ligament, greater omentum, and lesser omentum.