The skin covering the anterior abdominal wall is thin, in comparison with that of the back, and is relatively mobile over the underlying structural layers except at the umbilical region, where it is fixed. The thickness of the abdominal skin seems to augment when approaching the midline and especially around the umbilicus. Natural elastic traction lines of the skin (also known as skin tension lines or Kraissl’s lines) of the anterior abdominal wall are disposed transversely. Above the level of the umbilicus, these tension lines extend mostly in a horizontal direction, while below this level, they continue along with a slight inferomedial oblique direction. Incisions made along, or parallel to, these lines tend to heal without much scarring, whereas incisions that cross these lines tend to result in wide or heaped-up scars [1].

Superficial fat, just under the dermis, is formed of large fat lobes encased between fibrous septa in a honeycomb-like structure and presents nearly constant characteristics throughout. These septa (retinacula cutis superficialis or Camper`s fascia) appear well defined. They are mostly oriented perpendicular to the surface and are mechanically strong, anchoring the dermis to the deeper planes (Fig. 1.2).

Stronger attachments to the dermis in the midline and above the umbilicus have been reported [4]. This is the reason why liposuction performed above the umbilicus and close to the midline is more prone to result in irregularities. The attachments of the retinacula cutis superficialis to the skin at 5–7 cm above the umbilicus can occasionally be stronger than usual and create a deep horizontal line. This deformity cannot be corrected by classical or scarpa-saving undermining – more superficial interventions are necessary (Fig. 1.3).

The superficial fascia comprises two distinct layers: an outer, adipose layer lying subjacent to the dermis and an inner fibroelastic layer termed Scarpa’s fascia, the membranous layer of superficial fascia [1]. The fibrous layer with a membranous appearance –the fascia superficialis – is continuous and well organized. It separates the superficial and deep adipose tissues (Fig. 1.4).

This layer can be followed as a dissection plane from the thorax to the inguinal ligament. It does not appear uniform in thickness. Being a well-defined white layer in the lower abdomen, thickening toward the inguinal ligament where a multilayered structure of multidirectional collagen bundles is perceptible. The Scarpa’s fascia loses consistency in the upper abdomen, where it can be identified as a much thinner translucid collagen layer through which adipose tissue can be seen [4]. This membrane, which is strongly fused medially to the linea alba and caudally to the inguinal ligament and the osseous prominence of the iliac crest, cranially continues into the thorax. The membranous layer (Scarpa’s fascia) is an important structure, which is strong enough to diminish the tension of sutures when identified and sutured in continuity during closure of the abdominal flap [5].

Deep adipose tissue appears very different from the superficial adipose tissue, as its fat lobes are smaller, flatter, and less well defined (Fig. 1.5). This adipose layer shows significant variations in terms of thickness between different areas. Towards the points, at which the membranous layer of the subcutaneous tissue adheres to salient structures (e.g., the inguinal ligament, bony prominences, linea alba), they become thinner and tend to progressively reduce the fat component. However, the network of collagen fibres (retinacula cutis profunda) become stronger and more tightly packed and connects the deep aspect of the membranous layer to the deep fascia.

In the deep adipose layer, the fibrous septa are predominantly obliquely and horizontally oriented (retinacula cutis profunda) and connect the membranous layer (Scarpa’s fascia) to the fascia of the rectus abdominis or external oblique muscle [4]. The membranous layers DAT and SAT create a sliding system that absorb the mechanical stimulations applied to the skin or that are generated by muscular contractions.

In this way the subcutaneous tissue ensures autonomy between the skin and the muscles. If any scarring creates adhesion between the skin, membranous layer, and deep fascia, every muscular contraction could also affect the skin, activating the cutaneous receptors – also vice versa: every stimulation of the skin could be transmitted to the underlying structures. This may explain the importance of the correct layered reconstruction of the subcutaneous tissue in avoiding complications after closure of the abdominal surgery wounds [4].