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Abdominal Regions and Fasciae

Regiones et fasciae abdominales

For medical students2 min readUpdated 2026-10-10

The anterior abdominal wall is topographically divided into three major levels: superior, middle, and inferior. Each region has distinct boundaries, and the muscular framework is covered by a fascial system that plays a critical role in forming the inguinal canal and the coverings of the external genitalia.

Levels of the abdomenDivided into three main regions: epigastrium, umbilical region (mesogastrium), and hypogastrium.
Superficial fasciaBelow the umbilicus, it splits into two layers: the fatty Camper's fascia and the membranous Scarpa's fascia.
Transversalis fasciaForms the posterior wall of the inguinal canal and the deep inguinal ring.
Key landmarksCostal margins are visualized superiorly, and inguinal folds inferiorly.

Topographic Regions of the Abdomen

For clinical diagnostics, the anterior abdominal wall is divided into three main regions, each containing three sub-regions. This division allows for precise localization of pathological processes.

Superior Region — Epigastrium (epigastrium) Located in the upper part of the abdomen. Visual landmarks include the costal margins and the midline linea alba. The epigastrium includes:

Middle Region — Umbilical Region (mesogastrium) Occupies the central part of the abdominal wall. This zone includes:

Inferior Region — Hypogastrium (hypogastrium) Located in the lower part of the abdomen, where the inguinal folds are clearly visible. It includes:

Important vertical vascular and fascial landmarks run along the midline of the abdomen and must be considered during surgical approaches.

Superficial Fascia of the Abdomen

The superficial fascia of the anterior abdominal wall varies in structure depending on the level. In the upper abdomen, it is represented by a thin layer. However, below the level of the umbilicus, the fascia undergoes changes and splits into two distinct layers:

  1. Superficial (fatty) layer — Camper's fascia (fascia Camper). Consists of a layer containing adipose tissue.
  2. Deep (membranous) layer — Scarpa's fascia (fascia Scarpa). A denser connective tissue layer that extends inferiorly onto the thigh and perineum.

The membranous Scarpa's fascia has significant topographic importance because it contributes to the formation of fascial structures of the external genitalia. Specifically, it forms the fascia of the penis and clitoris (known as Buck's fascia / Colles' fascia) and forms the lig. fundiforme penis/clitoridis.

Transversalis Fascia (*fascia transversalis*)

The transversalis fascia is the internal lining of the abdominal wall. It covers the inner surface of the transversus abdominis muscle (m. transversus abdominis) and fuses tightly with the parietal peritoneum.

The role of the transversalis fascia is especially important in the lower abdomen, where it participates in forming the structure of the inguinal canal. The fascia transversalis specifically forms:

In the region of the deep inguinal ring, the medial margin of the transversalis fascia thickens locally. This thickening is called the interfoveolar ligament (lig. interfoveolare), also known as Hesslich's ligament.

Frequently asked questions

What forms the anterior wall of the inguinal canal?

The anterior wall of the inguinal canal is formed by the aponeurosis of the external oblique muscle. In its lateral part, it is additionally reinforced by muscle fibers of the internal oblique muscle. In large indirect inguinal hernias, this aponeurosis thins out, but the primary cause of herniation is weakness not of the anterior wall, but of the posterior wall of the inguinal canal.

What muscles are covered by the proper fascia of the abdomen?

The proper fascia of the abdomen (fascia propria) covers the external and internal surfaces of the abdominal oblique muscles. Specifically, it covers the outer surface of the external oblique muscle (m. obliquus externus abdominis). Between the internal oblique and transversus abdominis muscles, there is only a single fascial layer containing intercostal nerves and vessels. Posterior to the midaxillary line, the fascial layers fuse into a single sheet, and as the muscles transition into tendons, the fascia fuses tightly with them.

What folds and fossae does the parietal peritoneum form on the posterior surface of the anterior abdominal wall?

On the inner surface of the anterior abdominal wall, the parietal peritoneum forms the following folds and fossae:

  • Median umbilical fold (plica umbilicalis mediana): contains the obliterated urachus.
  • Medial umbilical folds (plicae umbilicales mediales): contain the obliterated umbilical arteries.
  • Lateral umbilical folds (plicae umbilicales laterales): contain the inferior epigastric vessels.
  • Round ligament of the liver (lig. teres hepatis): a fold running from the umbilicus to the liver containing the obliterated umbilical vein.

Fossae (potential weak spots) form between these folds:

  • Supravesical fossae (fossae supravesicales): located above the urinary bladder.
  • Medial inguinal fossae (fossae inguinales mediales): project onto the superficial inguinal ring.
  • Lateral inguinal fossae (fossae inguinales laterales): project onto the deep inguinal ring.
What are the exact anatomical boundaries of the anterior abdominal wall?

The anatomical boundaries of the anterolateral abdominal wall are defined by the following bony and muscular landmarks:

  • Superior boundary: Xiphoid process of the sternum and costal margins (up to the 10th ribs).
  • Inferior boundary: Inguinal ligaments, iliac crests, and pubic symphysis.
  • Lateral boundaries (conventionally): Posterior axillary lines, which separate the anterolateral abdominal wall from the lumbar region.
How is the linea alba anatomically formed?

The linea alba is anatomically formed by the interlacing of tendinous fibers from the aponeuroses of all three pairs of flat abdominal muscles. It is contributed to by:

  • External oblique muscle (m. obliquus abdominis externus);
  • Internal oblique muscle (m. obliquus abdominis internus);
  • Transversus abdominis muscle (m. transversus abdominis).

It is a fibrous band (tendinous plate) running along the midline from the xiphoid process to the pubic symphysis. Below the arcuate line (linea arcuata), the transversus abdominis contributes its aponeurosis to the linea alba while passing anterior to the rectus abdominis muscle.

What two layers does the superficial fascia divide into below the umbilicus?

Below the umbilicus, the superficial abdominal fascia divides into a superficial fatty layer (Camper's fascia) and a deep membranous layer (Scarpa's fascia).

Which structure forms the posterior wall of the inguinal canal?

The posterior wall of the inguinal canal, as well as the deep inguinal ring, is formed by the transversalis fascia (fascia transversalis).

What is Hesslich's ligament?

Hesslich's ligament, or the interfoveolar ligament (lig. interfoveolare), is a thickened medial margin of the transversalis fascia in the area of the deep inguinal ring.

What regions are included in the mesogastrium?

The middle region of the abdomen (mesogastrium) includes the umbilical region, as well as the right and left lateral (lumbar) regions.

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