| Tendinous intersection | |
|---|---|
| Rectus abdominis | |
| Latin | intersectiones tendineae musculi recti abdominis |
| Gray's | subject #118 415 |
The rectus abdominis muscle is crossed by fibrous bands, three in number, which are named the tendinous inscriptions (or tendinous intersections). One is usually situated opposite the umbilicus, one at the extremity of the xiphoid process, and the third about midway between the xiphoid process and the umbilicus.
These inscriptions pass transversely or obliquely across the muscle in a zigzag course; they rarely extend completely through its substance and may pass only halfway across it; they are intimately adherent in front to the sheath of the muscle.
Sometimes one or two additional inscriptions, generally incomplete, are present below the umbilicus.
Contents |
If well-defined, the rectus abdominis is colloquially called a "six-pack". This is due to tendinous intersections within the muscle, usually at the level of the umbilicus (belly-button), the xiphisternum, and about halfway between.
An extremely well defined abdominal section can appear to be an "eight pack", as all eight sections of the abdominal muscle become defined. This definition is prominent among athletes with low body fat percentages, such as bodybuilders, boxers, mixed martial artists and track and field athletes.
The tendinous intersections, in conjunction with the rectus abdominis, function to provide varying degrees of forward flexion to the lumbar region of the vertebral column, producing forward bending at the waist. Forward flexion results in a decreased angle between the trunk and lower body.
The anatomical segmentation of the rectus abdominis into three pairs of muscles and the positioning of these three pairs of muscles at different levels along the lumbar region (which are created by the tendinous intersections) are responsible for the forward flexion of the vertebral column:
The tendinous intersections define the anatomy of the rectus abdominis and assist with physiological movement. If the rectus abdominis did not have tendinous intersections, there would be one large muscle group on each side of the linea alba. This large muscle group would allow the vertebral column to flex forward, but would not permit a large extent of forward flexion.
The forward flexion provided by tendinous intersections makes daily activities like stretching or bending over to pick up an object possible.
This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.
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