Human Anatomy
Anterior Abdominal Wall
Anterior abdominal wall for MBBS: muscles, rectus sheath, inguinal canal, direct and indirect hernia and fascial layers, mapped to NMC codes AN44.1 to AN44.7.
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Anterior Abdominal Wall
Anterior abdominal wall for MBBS: muscles, rectus sheath, inguinal canal, direct and indirect hernia and fascial layers, mapped to NMC codes AN44.1 to AN44.7.
The anterior abdominal wall chapter covers the flat and vertical muscles, the rectus sheath, the inguinal canal and the layers of superficial fascia. It is the anatomical basis for abdominal incisions and the different types of inguinal hernia.
High-yield: Anterior Abdominal Wall
- The anterior abdominal wall has three flat muscles, the external oblique, internal oblique and transversus abdominis, and the vertical rectus abdominis.
- The rectus abdominis lies in the rectus sheath, formed by the aponeuroses of the three flat muscles.
- Above the arcuate line the posterior wall of the rectus sheath is present, but below it the rectus lies directly on the fascia transversalis.
- The linea alba is the midline fibrous raphe formed by the interlacing aponeuroses of the two sides.
- The inguinal canal is an oblique passage above the medial half of the inguinal ligament.
- The deep inguinal ring lies lateral to the inferior epigastric artery and the superficial ring lies above the pubic tubercle.
- The inguinal canal transmits the spermatic cord in the male and the round ligament of the uterus in the female.
- An indirect inguinal hernia enters through the deep ring lateral to the inferior epigastric artery.
- A direct inguinal hernia pushes through the weak posterior wall medial to the inferior epigastric artery.
- Hesselbach's triangle is bounded by the inferior epigastric artery, the rectus abdominis and the inguinal ligament, and is the site of direct hernia.
- The nerve supply of the abdominal wall is by the lower intercostal nerves and the subcostal, iliohypogastric and ilioinguinal nerves.
- The dermatome at the umbilicus is the tenth thoracic segment, a useful landmark.
- The superficial fascia of the lower abdomen has a fatty Camper's layer and a membranous Scarpa's layer.
- Scarpa's fascia continues into the perineum as Colles' fascia, which limits the spread of extravasated urine.
Inguinal hernia at a glance
- **Indirect hernia:** Enters the deep ring lateral to the inferior epigastric artery, follows the canal, more common and often congenital.
- **Direct hernia:** Pushes through the weak posterior wall medial to the inferior epigastric artery, within Hesselbach's triangle.
- **Canal contents:** Spermatic cord in the male, round ligament of the uterus in the female.
- **Rectus sheath:** Complete around rectus above the arcuate line; deficient behind below it.
NMC competencies in this chapter
- **AN44.1:** Muscles of the anterior abdominal wall and the rectus sheath
- **AN44.2:** Superficial fascia and nerves and vessels of the abdominal wall
- **AN44.3:** Inguinal canal: boundaries, contents and deep and superficial rings
- **AN44.4:** Types of inguinal hernia and their anatomical basis
- **AN44.5:** Descent of the testis and the coverings of the spermatic cord
- **AN44.6:** Abdominal incisions and the anterior abdominal wall
- **AN44.7:** Applied anatomy of the anterior abdominal wall
Frequently Asked Questions
How do you tell a direct from an indirect inguinal hernia?
An indirect hernia enters the deep ring lateral to the inferior epigastric artery and passes down the canal, while a direct hernia pushes through the weak posterior wall medial to that artery.
What is the rectus sheath and why does the arcuate line matter?
The sheath is formed by the flat muscle aponeuroses around rectus abdominis. Below the arcuate line all the aponeuroses pass in front, leaving the posterior wall deficient.
Why is the umbilicus a useful landmark?
It lies at the tenth thoracic dermatome, so it helps map sensory levels on the abdominal wall during clinical examination.
How does this chapter help in NEET-PG?
Hernia anatomy, the rectus sheath and abdominal incisions are core general surgery topics, so this wall is directly high-yield for PG preparation.
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