Arcuate line (anterior abdominal wall)
Encyclopedia
The arcuate line of the abdomen
, Linea semicircularis or Douglas' line is a horizontal line that demarcates the lower limit of the posterior layer of the rectus sheath
. It is also where the inferior epigastric vessels perforate the rectus abdominus.
Superior to the arcuate line, the internal oblique aponeurosis
splits to envelope the rectus abdominis muscle. Inferior to the arcuate line, the internal oblique and transversus abdominis aponeuroses merge and pass superficial (i.e. anteriorly) to the rectus muscle.
The arcuate line occurs about 1/3 of the distance from the umbilicus
to the pubic crest
, but this varies from person to person. Above the arcuate line, the rectus abdominis is surrounded by an anterior layer of the rectus sheath
and a posterior layer. The anterior layer is derived from the external oblique aponeurosis
and the anterior lamina of the internal oblique aponeurosis. The posterior layer is made up of the posterior lamina of the internal oblique aponeurosis and the tranverse abdominal aponeurosis. Inferior to the arcuate line, all three muscle aponeuroses make up the rectus sheath, that is now only anterior to the rectus abdominis and not posterior to it at all.
Therefore, inferior to the arcuate line, the rectus abdominis rests directly on the transversalis fascia
.
If one dissects the anterolateral abdominal wall, the arcuate line may be difficult to see, since all the aponeuroses are translucent.
Abdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
, Linea semicircularis or Douglas' line is a horizontal line that demarcates the lower limit of the posterior layer of the rectus sheath
Rectus sheath
The Rectus sheath is formed by the aponeuroses of the Obliqui and Transversus. It contains the Rectus abdominis and Pyramidalis muscles.It can be divided into anterior and posterior laminae....
. It is also where the inferior epigastric vessels perforate the rectus abdominus.
Superior to the arcuate line, the internal oblique aponeurosis
Aponeurosis
Aponeuroses are layers of flat broad tendons. They have a shiny, whitish-silvery color, are histologically similar to tendons, and are very sparingly supplied with blood vessels and nerves. When dissected, aponeuroses are papery, and peel off by sections...
splits to envelope the rectus abdominis muscle. Inferior to the arcuate line, the internal oblique and transversus abdominis aponeuroses merge and pass superficial (i.e. anteriorly) to the rectus muscle.
The arcuate line occurs about 1/3 of the distance from the umbilicus
Navel
The navel is a scar on the abdomen caused when the umbilical cord is removed from a newborn baby...
to the pubic crest
Pubic crest
Medial to the pubic tubercle is the pubic crest, which extends from this process to the medial end of the bone.It affords attachment to the inguinal falx, and to the External Abdominal Oblique and Pyramidalis....
, but this varies from person to person. Above the arcuate line, the rectus abdominis is surrounded by an anterior layer of the rectus sheath
Rectus sheath
The Rectus sheath is formed by the aponeuroses of the Obliqui and Transversus. It contains the Rectus abdominis and Pyramidalis muscles.It can be divided into anterior and posterior laminae....
and a posterior layer. The anterior layer is derived from the external oblique aponeurosis
Aponeurosis
Aponeuroses are layers of flat broad tendons. They have a shiny, whitish-silvery color, are histologically similar to tendons, and are very sparingly supplied with blood vessels and nerves. When dissected, aponeuroses are papery, and peel off by sections...
and the anterior lamina of the internal oblique aponeurosis. The posterior layer is made up of the posterior lamina of the internal oblique aponeurosis and the tranverse abdominal aponeurosis. Inferior to the arcuate line, all three muscle aponeuroses make up the rectus sheath, that is now only anterior to the rectus abdominis and not posterior to it at all.
Therefore, inferior to the arcuate line, the rectus abdominis rests directly on the transversalis fascia
Transversalis fascia
The transversalis fascia is a thin aponeurotic membrane which lies between the inner surface of the Transversus abdominis and the extraperitoneal fascia....
.
If one dissects the anterolateral abdominal wall, the arcuate line may be difficult to see, since all the aponeuroses are translucent.