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ANA 534 T2 AAW
learning objective answers to anterior abdominal wall
| Question | Answer |
|---|---|
| What are the 3 muscle layers of the anterolateral abdominal wall - list them in order from superficial to deep | External oblique, internal oblique and transversus abdominis. |
| What is the orientation of their fibers? | External oblique are directed inferior and medially (hands-in-pockets); internal oblique go upward and medially (opposite to the externals), and the transversus abdominis are oriented transversely. |
| Which attach posteriorly to the lumbar fascia? | The internal oblique and the transversus abdominis are attached posteriorly to the lumbar fascia. |
| What is the innervation of these muscle layers? | Intercostal nn. (referred to a thoracoabdominal nn. as they extend from the intercostal space down into the abdominal musculature. |
| How does each layer of the anterior abdominal wall contribute to the formation of the rectus sheath above the level of the umbilicus? | anterior sheath of rectus is composed of aponeurosis of external oblique and half aponeurosis of internal oblique; posterior sheath of rectus is composed of other half of aponeurosis of internal oblique and the aponeurosis of the transversus abdominis |
| What is the arcuate line? | The discontinuance of the posterior sheath of the rectus - approximately the level of L2. |
| What forms the posterior aspect of the rectus sheath below this line? | Only the fascia transversalis and peritoneum. |
| Where does the inferior epigastric artery arise? | External iliac artery. |
| Where does the inferior epigastric artery run within the rectus sheath? | Between the posterior sheath and posterior aspect of the rectus abdominis muscle. |
| How does the inferior epigastric artery pass the tendinous intersections of the rectus abdominis? | The tendinous intersection of the rectus abdominis only attach to the anterior sheath of the rectus so the pathway up the posterior aspect is unimpeded. |
| With what vessel does the inferior epigastric artery anastomose? | With the superior epigastric artery (one of the terminal br. of the internal thoracic artery). |
| What action results from the ipsilateral contraction of the anterolateral wall muscles? | Lateral trunk flexion. |
| What action results from the contralateral contraction of this group? | Torsion/twisting of the trunk. |
| Why is compression of the abdominal contents functionally important? | To increase intra-abdominal pressure to facilitate defecation/micuration (urination). |
| Which muscles are involved in quiet inspiration? Which diameters of the thorax do the muscles increase? | The intercostal mm. elevate the ribs increasing the transverse and anteroposterior diameters. |
| What is forced inspiration and which additional muscles are called on to act in this state? | Heavy breathing due to exertion. The scalenus anterior, scalenus medius and sternocleidomastoid. |
| Which muscles are used in respiratory distress? | Primarily the pectoralis major. The serratus anterior and pectoralis minor also participate in forced inspiration but to a more minor degree. |
| How do these muscles "change" their function to act in this capacity? | They reverse their origin/insertions so that they pull on the rib cage rather than anchor the limbs to it. |
| How is expiration accomplished? | Passively - through elastic recoil of the lung tissue. |
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