Anterior abdominal wall

From IKE

Surface anatomy of the front of the thorax and abdomen.

The anterior abdominal wall is the anterior wall covering the abdominal cavity.

• See Hernias, inguinal region and spermatic cord

Bony landmarks

• superiorly - right and left costal margins, meeting at the infrasternal angle where the xiphoid process is located
• inferiorly - right and left pubic crests, pubic tubercles, and more laterally, the anterior superior iliac spines and iliac crests.
• Source: [1]

Surface Features

• Umbilicus: lies in the midline at roughly the L_3-4 vertebral level, although its position varies, depending on the amount of subcutaneous fat
• The following linear surface landmarks are caused by underlying structures, and are particularly noticeable in muscular people with little body fat:
  1. linea alba: vertically, in the midline
  2. linea semilunaris: more lateral
  3. transversely, between the umbilicus and the xiphoid process, there are 3 tendinous intersections

Layers

1. Skin (Superficial)
2. Superficial fascia
   • Camper's fascia - fatty
   • Scarpa's fascia - membranous layer deep to the fatty layer allowing the skin in the lower part of the abdominal wall to move more freely. Inferiorly attached to the thigh (fascia lata) and medially continuous with Colle's fascia
3. Deep fascia - almost non-existent and may be disregarded
4. Rectus sheath
   • Consists of material from the external oblique, internal oblique, and transversus abdominus
   • Above the Arcuate line [2]:
     • transversus abdominus goes posterior of rectus abdominis
     • internal oblique splits to go both posterior and anterior of rectus abdominis
     • external oblique goes anterior of rectus abdominis
   • Below the Arcuate line [3]:
     • transversus abdominus, internal oblique, and external oblique go posterior of rectus abdominis
5. Rectus abdominis muscles
6. Transversalis fascia
7. Extraperitoneal tissue
8. Parietal peritoneum (Deep)

The Obliquus externus abdominis

Muscles

• External oblique
• Internal oblique
• Transversus abdominus
• Cremaster
• Rectus abdominis

Blood Supply

• Superior epigastric (from internal thoracic) artery
• Inferior epigastric (from external iliac) artery - supplies much of the area below the umbilicus
• musculophrenic
• subcostal
• intercostal
• lumbar

Innervation

• Thoracoabdominal (T₇-T₉) - enters rectus sheath
• subcostal (T₁₂) - enters rectus sheath
• Iliohypogastric (L₁)
  • does not enter sheath
  • suprapubic
• Ilioinguinal (L₁) - Enters superficial inguinal ring

Lymphatics

• From the region above the umbilicus:
  • superficial lymphatics drain to axillary lymph nodes
• below the umbilicus:
  • Superficial lymphatics drain to superficial inguinal nodes
• The deep lymph vessels of the abdominal wall follow the arteries and drain into three main groups of lymph nodes:
  1. (para)sternal nodes - from above the umbilicus
  2. external iliac nodes - from below the umbilicus
  3. lumbar (para-aortic) nodes - more laterally