What are the layers of the abdomen?

From the Guidelines

The abdomen consists of several distinct layers arranged from superficial to deep, including the skin, superficial fascia, muscular layer, transversalis fascia, extraperitoneal fat, and peritoneum. The outermost layer is the skin, followed by the superficial fascia (Camper's fatty layer and Scarpa's fibrous layer) 1. Beneath these lies the muscular layer, which includes the external oblique, internal oblique, and transversus abdominis muscles laterally, and the rectus abdominis muscle anteriorly. The rectus abdominis is enclosed within the rectus sheath, formed by aponeuroses of the lateral abdominal muscles. Deep to the muscles is the transversalis fascia, followed by the extraperitoneal fat. The deepest layer is the peritoneum, which has parietal and visceral components, as noted in the World Journal of Emergency Surgery 1. This layered arrangement provides structural support, protection for internal organs, and facilitates movement. Understanding these layers is essential for surgeons performing abdominal procedures, as each layer must be carefully navigated during surgery to access the abdominal cavity while minimizing trauma to surrounding tissues, and is supported by evidence from the International Journal of Surgery 1. Some key points to consider when navigating these layers include the use of a non-adherent interface layer to protect exposed organs and prevent adhesions between the bowel and abdominal wall, as well as the importance of careful closure of the abdominal wall to prevent complications such as incisional hernia and wound dehiscence. The peritoneum, the deepest layer, has parietal and visceral components, and its closure is not necessary after a midline laparotomy, even in an emergency setting, as it does not provide any short-term or long-term benefits, according to the World Society of Emergency Surgery guidelines 1.

From the Research

Layers of the Abdomen

The abdomen is composed of multiple layers, which can be categorized into internal and external layers.

• Internal layers:
  • The peritoneum 2
  • The deep layer of the subperitoneal fascia 2
  • The superficial layer of the subperitoneal fascia 2
  • The transversalis fascia 2
• External layers:
  • The skin 2
  • The superficial layer of the subcutaneous fascia 2
  • The deep layer of the subcutaneous fascia 2
  • The investing layer of the abdominal fascia 2

Subcutaneous Tissue Layers

The subcutaneous tissue of the abdomen comprises three layers:

• A superficial adipose layer (SAT) 3
• A membranous layer 3
• A deep adipose layer (DAT) 3

Anterior Abdominal Wall

The anterior abdominal wall is composed of multiple layers, including:

• The external oblique aponeurosis 4
• The internal oblique aponeurosis 4
• The transversus abdominis aponeurosis 4
• The rectus sheath, which is trilaminar (plywood-like) 4