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Rectus Sheath - want to learn more about it?

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Rectus Sheath

The rectus sheath is a tendon sheath (aponeurosis) which encloses the rectus abdominis and pyramidalis muscles. It is an extension of the tendons of the external abdominal oblique, internal abdominal oblique, and transversus abdominis muscles. In addition to these muscles, the rectus sheath also contains neurovasculature of the anterior abdominal wall. Its function is to protect the contents it encloses. 

This article will explain the definition, anatomy, and function of the rectus sheath.

Key facts about the rectus sheath
Definition Multilayered aponeurosis that encloses the rectus abdominis and pyramidalis muscles
Walls of upper three-quarters Anterior wall:
- Aponeurosis of external abdominal oblique muscle
- Aponeurosis of internal abdominal oblique muscle
Posterior wall:
- Aponeurosis of internal abdominal oblique muscle
- Aponeurosis of transversus abdominis muscle
Walls of lower quarter Anterior wall:
- Aponeurosis of external abdominal oblique muscle
- Aponeurosis of internal abdominal oblique muscle
- Aponeurosis of transversus abdominis muscle
Posterior wall:
- Absent
Function Protection of anterior abdominal muscles and vessels.
Provides maximal compression and support of abdominal organs.
Clinical relations Spigelian hernia, rectus sheath hematoma

Definition

The rectus sheath is a multilayered aponeurosis, a fibrous sheath of dense regular connective tissue. However, the rectus sheath doesn’t completely enclose its contents. 

It covers the anterior and posterior surfaces of the upper three-quarters of the rectus abdominis muscle, and the lower quarter of its anterior surface. The lower quarter of the posterior surface of the rectus abdominis muscle isn’t covered with rectus sheath at all, but rather lays directly on the transversalis fascia.

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Anatomy

The rectus sheath has an anterior and posterior wall. The walls are composed of a fusion of the aponeuroses of the external abdominal oblique, internal abdominal oblique, and transversus abdominis muscles. 

Besides the rectus abdominis and pyramidalis muscles, the rectus sheath contains the superior and inferior epigastric arteries and veins, lymphatic vessels, termination parts of lower five intercostal nerves (T7-T11), and the termination of the 12th thoracic nerve (T12). The superior and inferior epigastric arteries anastomose with each other at the level of umbilicus after entering into the rectus sheath. The space between the right and left rectus abdominis muscles is filled with the thickening of the anterior wall of the rectus sheath. This entire thickening which extends from the xiphoid process of the sternum to the pubic symphysis is called the linea alba.

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From superior to inferior, the composition of the rectus sheath walls changes. Superior to the costal margin, the anterior wall is made of aponeurosis of the external abdominal oblique muscle only, and there is no posterior wall at all. 

From the costal margin to the lower quarter of the rectus abdominis muscle, both walls completely wrap the upper three-quarters of the rectus abdominis muscle. Here, the anterior wall is comprised of aponeuroses of the external abdominal oblique and internal abdominal oblique muscles, whereas the posterior wall is made of aponeuroses of the internal abdominal oblique and transversus abdominis muscles. The line between the upper three quarters and the lower quarter of the rectus abdominis muscle is called the arcuate line

Inferior to the arcuate line, the lower quarter of the rectus abdominis muscle is covered by the rectus sheath on its anterior surface only, while the posterior surface is in direct contact with the transversalis fascia. The rectus sheath here is made of aponeuroses of all three above mentioned muscles – external and internal abdominal oblique muscles and the transversus abdominis muscle. Knowing this anatomy is very significant in surgery, as the arcuate line and linea alba are used as sites for accessing abdominal viscera and for orientation while performing a surgery.

Function

The function of the rectus sheath is to protect the muscles and vessels which it encloses. In addition, keeping the rectus abdominis and pyramidalis muscle together helps in providing maximal compression of and support to abdominal viscera.

Learn more about the rectus abdominis and pyramidalis muscles with our great video tutorials.

Clinical relations

Spigelian hernia

Spigelian hernia occurs when the fascia of the linea semilunaris (Spigelian line) is weak, and segments of intestines and peritoneum surrounding it to protrude through (herniate). As the weak spots are usually narrow, there is a high risk of strangulation and infarction of the herniated part of the intestines. Strangulation happens when a part of the tissue herniates through the narrow opening which in turn cuts off the blood supply to the herniated tissue and causes local death of that tissue (infarction). Spigelian hernias are in most cases associated with obesity, and are usually treated surgically.

Rectus sheath hematoma

Collection of blood within tissues is called a hematoma. Any bleeding from the superior and inferior epigastric vessels contained in the rectus sheath can easily spread into and accumulate in the abdomen. This is because there is no strong aponeurosis that will stop blood spreading below the arcuate line; there is only the transversalis fascia. Rectus sheath hematomas usually self-resolve without any treatment.

Rectus Sheath - want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

Sign up for your free Kenhub account today and join over 1,074,267 successful anatomy students.

“I would honestly say that Kenhub cut my study time in half.” – Read more. Kim Bengochea Kim Bengochea, Regis University, Denver

Show references

References:

  • Moore, K. L., Dalley, A. F., & Agur, A. M. R. (2014). Clinically Oriented Anatomy (7th ed.). Philadelphia, PA: Lippincott Williams & Wilkins.
  • Drake, R. L., Vogl, A. W., & Mitchell, A. W. M. (2015). Gray’s Anatomy for Students (3rd ed.). Philadelphia, PA: Churchill Livingstone.

Article, review and layout:

  • Jana Vaskovic
  • Alexandra Osika
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