Block 6 Anatomy Abdom Wall Umich W Expl

Explanation
The ilioinguinal nerves supply motor and sensory fibers to the abdominal wall inferior to the umbilicus. What differentiates these nerves from the iliohypogastric nerves is that the ilioinguinal nerves also innervate the scrotum or labia by passing through the inguinal canal. These branches are called the anterior scrotal or labial nerves. Anterior cutaneous branches pretty much describes what these branches are, but there's an answer here that is a little more specific. The genital branch of the genitofemoral nerve innervates the cremaster muscle.

Explanation
Since the appendix is located in the right lower quadrant, you would probably want to make your incision there to remove it! The appendix is the terminal portion of the cecum which has a small, dead-end lumen. It is located just behind the cecum in the right internal iliac fossa.
Where are incisions made for other procedures? For a cholecystectomy (gall bladder removal), there is an incision in the right upper quadrant. (Or, this surgery can be performed laproscopically.) For a caesarian, a transverse suprapubic incision (also called a Pfannenstiel incision) is used. A midline incision, through the linea alba, may be used to repair an aortic aneurysm.

Explanation
The rectus sheath is a tough, tendinous sheath over the rectus abdominis muscle. It covers the entire anterior surface of the rectus abdominis. However, on the posterior side of the muscle, the sheath is incomplete-- it ends inferiorly at the arcuate line. Below the arcuate line, the rectus abdominis is covered by transversalis fascia, not the rectus sheath! The linea alba is also related to the rectus abdominis--it is a ligament that runs down the middle of the abdomen, bisecting the rectus abdominis. It is made by the intermingling of the aponeuroses of the external oblique, internal oblique, and transversus abdominis. It's a good place to make a vertical incision.
All of the other answer choices are related to the inguinal canal. The falx inguinalis (sometimes called the inguinal falx or conjoint tendon), is the inferomedial attachment of transversus abdominis with some fibers of internal abdominal oblique--it contributes to the posterior wall of the inguinal canal. The inguinal ligament is the ligament that connects the anterior superior iliac spine with the pubic tubercle--it makes the floor of the inguinal canal. The internal (deep) inguinal ring is the entrance to the inguinal canal, where the transversalis fascia pouches out and creates an opening through which structures can leave the abdominal cavity.

Explanation
The pubic tubercle is a bony process that would be felt lateral to the edge of the spermatic cord at the superficial inguinal ring. (This is really the only answer choice that could feel like a bony prominence when palpated.)The pubic tubercle serves as the point of attachment for the inguinal ligament, which makes up the floor of the inguinal canal. The pubic pecten is the ridge on the superior surface of the superior pubic ramus. This is the place where you find the pectineal ligament, a thickening of fascia on the pecten of the pubis. The pectineal ligament is a good place to put sutures when doing surgery. The pubic symphysis is the joint between the two pubic bones. The iliopubic eminence is a bony process on the pubis found near its articulation with the ilium. The iliopectineal line is a line formed by the arcuate line of the ilium and the pectineal line of the pubis. This line forms a plane that marks the transition between the abdominal and pelvic cavity.

Explanation
The epigastric region is one of the nine regions of the abdomen. It contains the duodenum, part of the stomach, part of the liver, and the pancreas. This is the region that the surgeon would need to enter to reach the ulcer in the first part of the duodenum. The left inguinal region contains the sigmoid colon. The left lumbar region contains the descending colon and kidney. The right hypochondrial region contains part of the liver and the gall bladder. Finally, the hypogastric region contains the bladder and rectum. For a good picture of this, see the dissector answer 1 for this lab.

Explanation
The iliohypogastric nerve is a branch of the lumbar plexus. It provides sensory innervation to the skin of the lower abdominal wall, upper hip and upper thigh. This is the region where the patient is experiencing paresthesia, so this nerve must be injured. The genitofemoral nerve is another nerve from the lumbar plexus. It provides sensory innervation to the skin of the anterior scrotum or labia majora and upper medial thigh. The subcostal nerve is the ventral primary ramus of T12--it is the equivalent of an intercostal nerve at a higher thoracic level. It provides sensory innervation to the anterolateral abdominal wall, but in an area superior to the pubic region. A spinal nerve would not have been injured in the operation. Remember--the spinal nerve is just that small segment of nerve that exists once the dorsal and ventral rootlets come together, before the dorsal and ventral primary rami branch off. In any case, the T9 and T10 dermatomes are superior to the area where the patient is experiencing paresthesia.

Explanation
Remember - the transverse suprapubic incision (also called the Pfannenstiel incision) is made below the arcuate line. So, there is no longer a posterior layer of the rectus sheath, and the inner surface of the rectus abdominis is lined only with transversalis fascia. When making this incision, the abdominal wall layers are incised as follows: skin, superficial fascia (fatty and membranous), deep fascia, anterior rectus sheath, rectus abdominis muscle, transversalis fascia, extraperitoneal connective tissue, and peritoneum.

Explanation
The inferior epigastric vessels are found in the preperitoneal fat of the abdomen. They lie just superficial to the peritoneum and form the lateral umbilical fold. Hernias may pass lateral or medial to these vessels. If the hernia is lateral to the vessels (which is what happened in this case), it is an indirect inguinal hernia. If the hernia is medial to these vessels, it is a direct inguinal hernia.
The deep circumflex artery courses along the iliac crest on the inner surface of the abdominal wall. This artery is very lateral on the abdominal wall, and hernias would pass medial to this vessel. The superficial circumflex iliac, superficial epigastric, and superficial external pudendal arteries are all superficial arteries that arise from the femoral artery. They are all found in the superficial fascia--not in the preperitoneal fat.

Explanation
The arcuate line is an anatomical feature on the inner surface of the abdominal wall. It is the point at which the posterior lamina of the rectus sheath ends and transversalis fascia lines the inner surface of rectus abdominis. The intercrestal line is an imaginary line drawn in the horizontal plane at the upper margin of the iliac crests. It is a landmark used to find the L4 vertebra, which is useful when performing a spinal tap. Linea alba is an aponeurotic band on the midline of the anterior abdominal wall, which extends from the xiphoid process to the pubic symphysis. It is formed by the combined abdominal muscle aponeuroses, and it provides a useful site for a midline incision in the abdomen. The pectineal line is a structural feature of the pubic bone. It is an oblique ridge on the lateral part of the superior ramus. Finally, the semilunar line is the lateral margin of the rectus abdominis, formed by the fused aponeuroses of the abdominal wall muscles at the lateral margin of the rectus sheath.

Explanation
The linea alba is an aponeurotic band on the midline of the anterior abdominal wall, which extends from the xiphoid process to the pubic symphysis. It is formed by the combined abdominal muscle aponeuroses. Because there are no major arteries or nerves running in the linea alba, it provides a useful site for a midline incision in the abdomen. The linea aspera is a vertical ridge on posterior surface of the femur. The arcuate line is the point at which the posterior lamina of the rectus sheath ends, and transversalis fascia lines the inner surface of rectus abdominis. The semilunar line is the lateral margin of the rectus abdominus, formed by the fused aponeuroses of the abdominal wall muscles. The iliopectineal line is a line on the pelvic bones, formed by the arcuate line of the ilium and the pectineal line of the pubis. (Note--the arcuate line of the ilium is totally different than the arcuate line of the rectus sheath!) This line is important because it marks the boundary between the abdominal cavity and the pelvic cavity.

Explanation
If the internal thoracic artery was ligated, blood would no longer flow to the superior epigastric artery, which is the branch of the internal thoracic that supplies blood to rectus abdominis. However, the superior epigastric artery communicates with the inferior epigastric artery, a branch of the external iliac artery. This means that blood could flow from the external iliac, to the inferior epigastric, to the superior epigastric and the rectus abdominis. The superficial epigastric and superficial circumflex iliac arteries are two superficial branches of the femoral artery. They do not supply deep structures in the abdomen. The distal portions of the umbilical arteries are obliterated in adults--they are the medial umbilical ligaments that form the medial umbilical folds. The deep circumflex iliac artery courses along the iliac crest on the inner surface of the abdominal wall. It is too lateral to supply blood to rectus abdominis.

Explanation
The umbilicus is an important landmark for venous and lymphatic drainage of the abdominal wall. Above the umbilicus, lymphatics drain into the axillary lymph nodes and the venous blood drains into the superior epigastric vein, which drains to the internal thoracic vein. Below the umbilicus, lymphatics drain into the superficial inguinal lymph nodes, while venous blood drains into the inferior epigastric vein and the external iliac vein