Anatomy of the Anterior Abdominal Wall

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Questions and Answers

What is the origin of the transversus abdominus muscle?

The lumbar fascia only

The lateral two-thirds of the upper concave surface of the inguinal ligament

The anterior two-thirds of the inner lip of the iliac crest

The lateral one-third of the upper concave surface of the inguinal ligament (correct)

What is the direction of the fibers of the transversus abdominus muscle?

Obliquely backwards

Transversely forwards (correct)

Circumferentially

Longitudinally forwards

What is the insertion of the transversus abdominus muscle?

Into the pubic crest, pectineal line, and lower six costal cartilages

Into the lower six costal cartilages only

Into the xiphoid process, linea alba, and pubic crest only

Into the xiphoid process, linea alba, pubic crest, and pectineal line (correct)

What forms the conjoint tendon?

The lower muscle fibers of the internal oblique and transversus abdominus muscles Signup and view all the answers

What is the purpose of the tendinous intersections in the rectus abdominus muscle?

To provide additional strength to the muscle Signup and view all the answers

How many tendinous heads arise from the pubic crest and tubercle?

One large head and one smaller head Signup and view all the answers

What is the name of the curved lower margin of the posterior wall of the rectus sheath?

The arcuate line Signup and view all the answers

What fascia is in direct contact with the lower quarter of the rectus abdominus muscle?

The transversalis fascia Signup and view all the answers

What forms the boundary of the abdomen above?

Xiphoid process of the sternum Signup and view all the answers

Which of the following is NOT a layer of the anterior abdominal wall?

Muscle of the lower limb Signup and view all the answers

What is the direction of fibers in the external oblique muscle?

Downwards, forwards, and medially Signup and view all the answers

What is the origin of the internal oblique muscle?

Lateral 2/3 of the upper inner surface of the inguinal ligament Signup and view all the answers

What is the insertion of the aponeurosis of the external oblique muscle?

Xiphoid process, linea alba, pubic crest, and tubercle Signup and view all the answers

What is the inguinal ligament formed from?

Free lower border of the aponeurosis of the external oblique muscle Signup and view all the answers

What is the function of the superficial inguinal ring?

Allows transmission of the spermatic cord or round ligament of the uterus Signup and view all the answers

What is the insertion of the internal oblique muscle?

Linea alba, pubic crest, and pectineal line Signup and view all the answers

Which of the following muscles originates from the pubic crest?

Pyramidalis Signup and view all the answers

Which nerve supplies the pyramidalis muscle?

Subcostal nerve (T12) Signup and view all the answers

Which of the following actions is NOT a function of the muscles of the anterior abdominal wall?

Flexion of the hip joint Signup and view all the answers

What is the main action of the quadratus lumborum muscle?

Lateral flexion of the vertebral column Signup and view all the answers

Which nerve supplies the external oblique muscle?

Ventral rami of 7-12th thoracic nerve Signup and view all the answers

What is the insertion of the quadratus lumborum muscle?

All of the above Signup and view all the answers

Which of the following muscles is involved in compressing the abdominal contents?

All of the above Signup and view all the answers

What is the result of the contraction of the muscles of the anterior abdominal wall during expiration?

Increased intra-abdominal pressure Signup and view all the answers

Study Notes

Abdominal Wall

Bounded above by the xiphoid process of the sternum and costal margin, and below by the upper parts of the pelvic bones and the upper margins of the lower limbs.

Anterior Abdominal Wall Layers

1. Skin
1. Superficial fatty layer
1. Deep membranous layer
1. External oblique muscle
1. Internal oblique muscle
1. Transversus abdominis
1. Fascia transversalis
1. Extraperitoneal fat
1. Parietal peritoneum

External Oblique Muscle

Origin: Eight fleshy muscular digitations from the lower eight ribs close to their costal cartilage.
Direction of fibers: Downwards, forwards, and medially.
Insertion: Aponeurosis inserted into the xiphoid process, linea alba, pubic crest and tubercle, and ASIS.
Particular features:
- Free borders: Upper horizontal border, posterior vertical border, and lower free border.
- Inguinal ligament: Forms from the free lower border of the aponeurosis of E.O.M. between the anterior superior iliac spine laterally and the pubic tubercle medially.
- Superficial inguinal ring: A perforation in the lower medial part of the aponeurosis allowing transmission of the spermatic cord or the round ligament of the uterus.

Internal Oblique Muscle

Origin: Lateral 2/3 of the upper inner surface of the inguinal ligament, anterior 2/3 of the intermediate line of the iliac crest, and lumbar fascia.
Direction of fibers: Upwards, forwards, and medially.
Insertion: Aponeurosis into the lower six costal cartilages, xiphoid process, linea alba, pubic crest, and pectineal line.

Transversus Abdominis Muscle

Origin: Lateral one-third of the upper concave surface of the inguinal ligament, anterior two-thirds of the inner lip of the iliac crest, lumbar fascia, and inner surfaces of the lower six costal cartilages.
Direction of fibers: Transversely forwards.
Insertion: Aponeurosis into the xiphoid process, linea alba, pubic crest, and pectineal line.
Conjoint tendon: Formed by the lower muscle fibers of internal oblique and transversus abdominus passing medially and forming an arch from their origin to their insertion, crossing over the spermatic cord to gain insertion into the pubic crest and pectineal line.

Rectus Abdominis Muscle

Origin: By two narrow tendinous heads; one large head arising from the pubic crest and tubercle, and the other smaller head from the symphysis pubis.
Insertion: By fleshy slips into the fifth, sixth, and seventh costal cartilages.
Tendinous intersections:
- 1-3 or 4 intersections along the course of the muscle.
- Levels: One at the level of the xiphoid process, one at the level of the umbilicus, one midway between the xiphoid process and the umbilicus, and the 4th one may be present in some people below the level of the umbilicus.
- Seen on the anterior surface and absent on the posterior surface.

Rectus Sheath

Has an anterior wall and a posterior wall that meet at the lateral margin of the rectus muscle.
Anterior wall covers the whole anterior surface of the muscle.
Posterior wall of the sheath covers only the upper three-quarters of the posterior surface of the muscle, leaving the lower quarter in direct contact with the transversalis fascia.
Contents:
- Two muscles (rectus abdominus and the pyramidalis when present).
- Epigastric arteries and veins.
- Terminal parts of the lower five intercostal and subcostal nerves.

Pyramidalis Muscle

Origin: From the pubic crest.
Insertion: Into the lower part of the linea alba.

Nerve Supply of Muscles of the Anterior Abdominal Wall

External Oblique muscle: Ventral rami of 7-12th thoracic nerves.
Internal Oblique muscle and Transverse Abdominus: Lower 6 thoracic nerves and 1st lumbar (iliohypogastric and ilioinguinal nerves).
Rectus Abdominis: Lower 6 thoracic nerves.
Pyramidalis: Subcostal nerve (T12).

Actions of Muscles of the Anterior Abdominal Wall

Movements of the trunk.
Respiratory actions.
Expulsive actions.
Supportive actions.
Protective actions.
Compression of the abdominal contents and keeping them in position.
Assist in the process of expiration during breathing.
Contraction of abdominal muscles and diaphragm to compress abdominal contents, increasing intra-abdominal pressure to assist in urination, defecation, and labor.
Both oblique muscles help in laterally flex and rotate the trunk.
Rectus abdominus muscle flex the trunk forwards.

Quadratus Lumborum Muscle

Origin: Posterior 1/3 of the iliac crest.
Insertion: Medial half of the lower border of the 12th rib and tips of transverse processes of upper 4 lumbar vertebrae.
Nerve supply: Subcostal nerve (T12) and upper 4 lumbar nerves.
Action: Lateral flexion of the vertebral column and extension of lumbar vertebrae.

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Description

Explore the layers and boundaries of the anterior abdominal wall, including the skin, muscles, and fascia. Learn about the anatomy of the abdomen and its surrounding structures.