Topographical regions of the abdomen
For the convenience of clinical diagnosis, the anterior abdominal wall is divided into three main regions, each including three subregions. This division allows for the precise localization of pathological processes.
Upper region — epigastrium (epigastrium) This zone is located in the upper part of the abdomen. The visual landmarks here are the costal margins and the linea alba running centrally (linea alba). The epigastrium includes:
- The epigastric region proper.
- The right hypochondriac region.
- The left hypochondriac region.
Middle region — umbilical region (mesogastrium) Occupies the central part of the abdominal wall. In this zone, the following are distinguished:
- The umbilical region (located centrally).
- The right lateral (lumbar) region.
- The left lateral (lumbar) region.
Lower region — hypogastrium (hypogastrium) Located in the lower part of the abdomen, where the inguinal folds are clearly visible. Includes the following zones:
- The pubic region (centrally).
- The right inguinal (or iliac) region.
- The left inguinal (or iliac) region.
It should be noted that important vertical vascular and fascial landmarks run along the midline of the abdomen, which must be taken into account during surgical approaches.
Superficial fascia of the abdomen
The superficial fascia of the anterior abdominal wall has a varying 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 separate layers.
- Superficial (fatty) layer — Camper's fascia (Camperi). It is a layer containing adipose tissue.
- Deep (membranous) layer — Scarpa's fascia (Scarpae). This is a denser connective tissue layer that continues inferiorly, passing onto the thigh and perineum.
Scarpa's membranous layer is of great topographical importance as it participates in the formation of the fascial structures of the external genitalia. In particular, it forms the fascia of the penis and clitoris (known as Buck's/Colles' fascia — Buck/Colles), and also forms the fundiform ligament (lig. fundiforme penis/clitoridis).
Transversalis fascia (fascia transversalis)
The transversalis fascia is the internal lining of the abdominal wall. It covers the transversus abdominis muscle (m. transversus) from the inside and tightly fuses with the parietal peritoneum.
The role of the transversalis fascia is especially important in the lower abdomen, where it participates in the formation of the structure of the inguinal canal. It is precisely the fascia transversalis that forms:
- The posterior wall of the inguinal canal.
- The deep inguinal ring (anulus inguinalis profundus).
In the region of the deep inguinal ring, the medial edge of the transversalis fascia locally thickens. This thickening is called the interfoveolar ligament (lig. interfoveolare), also known as Hesslich's ligament.
Briefly: answers to topical 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 abdominal muscle. In its lateral part, it is additionally reinforced by the muscle fibers of the internal oblique abdominal muscle. In large indirect inguinal hernias, thinning of this aponeurosis occurs, but the root cause of hernia formation is the weakness not of the anterior, but of the posterior wall of the inguinal canal.
What muscles does the proper fascia of the abdomen cover?
The proper fascia of the abdomen (fascia propria) covers the outer and inner surfaces of the oblique abdominal muscles. In particular, it covers the external oblique abdominal muscle externally (m. obliquus externus abdominis). Between the internal oblique and transversus muscles, there is only a single fascia through which intercostal nerves and vessels pass. Posterior to the midaxillary line, the fascial layers merge into a single one, and where the muscles transition into tendons, the fascia tightly fuses 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 from the umbilicus to the liver with the obliterated umbilical vein.
Between the folds, fossae (weak spots) are formed:
- Supravesical fossae (fossae supravesicales) — 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 precise 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 (conventional) — posterior axillary lines, which separate the anterolateral abdominal wall from the lumbar region.
What is the linea alba anatomically formed by?
The linea alba (linea alba) is anatomically formed by the intertwining of tendinous fibers of the aponeuroses of all three pairs of broad abdominal muscles. Its formation involves:
- External oblique abdominal muscle (m. obliquus abdominis externus);
- Internal oblique abdominal muscle (m. obliquus abdominis internus);
- Transversus abdominis muscle (m. transversus abdominis).
It is a fibrous cord (tendinous plate) extending along the midline from the xiphoid process to the pubic symphysis. Below the arcuate line (linea arcuata), the transversus muscle weaves its aponeurosis into the linea alba, passing anterior to the rectus abdominis muscle.
Class and exam questions
Into what two layers is the superficial fascia divided below the umbilicus?
Below the umbilicus, the superficial fascia of the abdomen divides into a superficial fatty layer (Camper's) and a deep membranous layer (Scarpa's).
What 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 Hesselbach's ligament?
Hesslich's ligament, or the interfoveolare ligament (lig. interfoveolare), is the thickened medial edge of the transversalis fascia in the region of the deep inguinal ring.
Which regions are part of the mesogastrium?
The middle section of the abdomen (mesogastrium) includes the umbilical region, as well as the right and left lateral (lumbar) regions.
What else to study on this topic
- Formation of the deep inguinal ring (anulus inguinalis profundus)
- Topography of the interxfoveolar ligament (lig. interfoveolare)
- Derivatives of Scarpa's fascia in the perineum (Buck's/Colles' fasciae)
- Connection of the transversalis fascia with the parietal peritoneum
- Vertical vascular and fascial landmarks of the linea alba
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