Anterior Abdominal Wall, Inguinal Canal and Peritoneum Flashcards
Click on Answer for transverse section images of the abdomen.
List the surface landmarks of the abdomen.
Bony landmarks:
costal margins, xiphoid process, iliac crest, pubic symphysis
Soft tissue landmarks:
groove of groin, midline furrow/groove, umbilicus, linea semilunaris, spermatic cord, McBurney’s point, Murphy’s point
[Diagram 1] [Diagram 2] [Diagram 3]
Further notes:
costal margins: the cartilages of the 7th, 8th, 9th, and 10th ribs form the costal margins. The 7th costal cartilage is the lowest cartilage to reach the sternum. The right and left costal margins run upward and medially toward the side of the xiphoid process and enclose between them an infrasternal angle. The costal margin reaches its lowest level in the midaxillary line.
xiphoid process: it lies at the level of the T9 vertebra
groove of groin: it is a curved linear horizontal groove which extends downward and medially from the ASIS to the pubic tubercle. It is convex downward and overlies the inguinal/Poupart’s ligament, hence it is also called the inguinal/Poupart’s line. It is placed at the junction of the anterior abdominal wall and the front of the thigh.
midline furrow/groove: It is a linear furrow/groove, which extends from the xiphoid process above to the pubic symphysis below. It corresponds to the linea alba — a tendinous raphe, which separates the two rectus muscles from each other. The midline linear furrow divides the anterior abdominal wall into right and left halves.
umbilicus: It is an irregular, depressed scarred area in the linear midline
furrow, a little below its midpoint.
linea semilunaris: It is a curved furrow, which extends from tip of the 9th costal cartilage to the pubic tubercle. It lies few centimeters away from the median furrow and corresponds to the lateral margin of the rectus abdominis.
spermatic cord: It is a soft rounded cord present in the males. It can be palpated through skin as it passes downward just above the medial end of inguinal ligament to enter the scrotum.
McBurney’s point: It is a point at the junction of medial 2/3rd and lateral 1/3rd of the line extending from the umbilicus to the anterior superior iliac spine (spinoumbilical line). The base of appendix lies deep to this point.
Murphy’s point: It is a point where linea semilunaris meets the right subcostal margin. It corresponds to the tip of the 9th costal cartilage. The fundus of gall bladder lies deep to this point.
Describe the sensory innervation of the abdominal wall.
The skin of the anterior abdominal wall is supplied by the six lower intercostal and subcostal nerves. The most inferior part is supplied by the first lumbar nerve through the iliohypogastric and ilioinguinal nerves. [Diagram]
State the boundaries of the abdominal wall.
Superiorly: xiphoid process, costal cartilages of the 7th to 10th ribs
Inferiorly: iliac crest, anterior superior iliac spine, inguinal ligament, pubic tubercle, pubic crest and pubic symphysis
List the layers of the anterolateral abdominal wall from the most superficial.
✓ skin
✓ Camper’s fascia (fatty part of superficial fascia of anterior abdominal wall)
✓ Scarpa’s fascia (membranous part of superficial fascia of anterior abdominal wall)
✓ external oblique abdominis
✓ internal oblique abdominis
✓ transversus abdominis
✓ fascia transversalis
✓ parietal peritoneum
[Diagram: Layers of the anterior abdominal wall]
♌︎ The arcuate line is an area of demarcation visible from the peritoneal surface of the abdominal wall, residing one-third the distance between the umbilicus and the pubis. The arcuate line can be a sharp demarcation, or it can be a gradual transition zone where the fibers of the posterior sheath gradually disappear. In addition, the arcuate line is the location where the inferior epigastric vessels perforate the rectus sheath, to supply blood to the inferior portion of the anterior abdominal wall.
Further notes:
Extraperitoneal fat may be found between fascia transversalis and the parietal peritoneum.
[6-minute video]: applied anatomy - Appendectomy
List the layers of the paramedian anterior abdominal wall starting with the most superficial.
✓ skin
✓ Camper’s fascia
✓ Scarpa’s fascia
✓ anterior layer of the rectus sheath (formed by aponeurosis of external abdominal oblique muscle and anterior lamina of internal abdominal oblique muscle)
✓ rectus abdominis muscle
✓ posterior layer of the rectus sheath (formed by posterior lamina of internal abdominal oblique muscle and aponeurosis of transversus abdominis muscle)
✓ fascia transversalis
✓ parietal peritoneum
[Diagram: Layers of the anterior abdominal wall]
♌︎ The arcuate line is an area of demarcation visible from the peritoneal surface of the abdominal wall, residing one-third the distance between the umbilicus and the pubis. The arcuate line can be a sharp demarcation, or it can be a gradual transition zone where the fibers of the posterior sheath gradually disappear. In addition, the arcuate line is the location where the inferior epigastric vessels perforate the rectus sheath, to supply blood to the inferior portion of the anterior abdominal wall.
List the structures that a needle piercing the midline of the anterior abdominal wall would pass through.
✓ skin
✓ Camper’s fascia
✓ Scarpa’s fascia
✓ linea alba (formed by crisscrossing fibers of rectus sheath)
✓ fascia transversalis
✓ parietal peritoneum
List the extensions/expansions of the inguinal ligament.
(a) Lacunar ligament aka. Gimbernat’s ligament
(b) Pectineal ligament (ligament of Cooper)
(c) Reflected part [The superficial fibres from the medial end of the inguinal ligament expand upward and medially to form this ligament. It lies behind the superficial inguinal ring and in front of the conjoint tendon. Its fibres interlace with those of its counterpart of the opposite side at the linea alba.]
State the contents of the rectus sheath.
Muscles: rectus abdominis, pyramidalis
Vessels: superior epigastric and inferior epigastric vessels
Nerves: lower 6 thoracic nerves
Briefly discuss the cutaneous lymphatic drainage of the abdominal wall.
(a) Above the umbilicus, the lymph vessels run upward to drain into the axillary lymph nodes (anterior/pectoral group).
(b) Below the umbilicus, the lymph vessels run downward and laterally to drain into the superficial inguinal lymph nodes.
State the following regarding the external oblique:
Origin, Insertion, Actions, Vascular supply, Innervation
Origin: external surface of the 5-12th ribs.
Insertion: linea alba, pubic tubercle and anterior half of iliac crest.
Actions: The external oblique muscle causes ipsilateral lateral flexion of the trunk and contralateral rotation of the trunk when it contracts unilaterally. Bilateral contraction flexes the trunk anteriorly, increasing intra-abdominal pressure, which is useful in processes such as breathing, singing and defecation.
Vascular supply: intercostal, subcostal and deep circumflex iliac arteries.
Innervation: intercostal nerves (T7-T11), subcostal nerve (T12) [or simply: anterior primary rami of lower six thoracic spinal nerves], and sensory innervation is provided by the iliohypogastric nerve (L1)
Further notes:
The fibres of the external oblique muscle run diagonally downward from the middle of the rib cage.
State the following regarding the internal oblique:
Origin, Insertion, Actions, Vascular supply, Innervation
Origin: thoracolumbar fascia, iliac crest, iliopectineal arch.
Insertion: 9-12th ribs (aponeurosis as high as 7th costal cartilage), linea alba, pubic crest.
Actions: Upon bilateral contraction, the internal abdominal oblique flexes the trunk and causes compression of the intra-abdominal viscera thereby increasing the intra-abdominal pressure. When it contracts unilaterally, it causes ipsilateral lateral flexion and ipsilateral rotation of the torso.
Vascular supply: intercostal, subcostal, inferior epigastric and deep circumflex iliac artery.
Innervation: by the anterior primary rami of lower six thoracic nerves (T7-T12) and first lumbar nerve (L1) via iliohypogastric and ilioinguinal nerves.
Further notes:
The fibres of the internal oblique muscle are obliquely oriented, running diagonally upward from the pelvis. This orientation is perpendicular to that of the external oblique. [Diagram]
State the following regarding the transversus abdominis muscle.
Origin, Insertion, Actions, Vascular supply, Innervation
Origin: 7-12th ribs, thoracolumbar fascia, iliac crest, inguinal ligament.
Insertion: linea alba, pubic crest, pectineal line.
Actions: when it contracts bilaterally, it compresses the abdominal contents, which is useful in processes such as breathing, singing, and defecation. This action also aids in expiration. When it contracts unilaterally, it causes ipsilateral trunk rotation.
Vascular supply: intercostal, subcostal, superior/inferior epigastric, superficial/deep circumflex iliac and posterior lumbar arteries.
Innervation: By the anterior primary rami of lower six thoracic nerves (T7–T12), and first lumbar (L1) nerve via iliohypogastric and ilioinguinal nerves.
Further notes:
The fibres of the transversus abdominis muscle run horizontally, except the lowest ones, which run obliquely downwards.