Block 6 Anatomy Kidney Retrperitneum Umich W Expl

Preganglionic fibers from the greater thoracic splanchnic nerve directly innervate the suprarenal medulla, causing a systemic sympathetic response. Postganglionic sympathetic axons from the celiac plexus distribute along branches of the celiac trunk to supply the vascular smooth muscle of those arteries. Preganglionic fibers from the lesser thoracic splanchnic nerve travel to the aorticorenal ganglia; postganglionic fibers from the aorticorenal ganglia supply the vascular smooth muscle of the branches of the renal arteries. The postgangionic fibers from the renal plexus provide sympathetic innervation to smooth muscle to the blood vessels supplying the kidney, renal pelvis and upper ureter.

The obturator nerve lies along the medial border of the psoas major muscle. The femoral nerve lies along the lateral border of the psoas major muscle, between psoas major and iliacus. The genitofemoral nerve pierces psoas major then lies on top of that muscle. The ilioinguinal nerve emerges at the lateral border of psoas major, then travels laterally.

The suprarenal medulla is directly innervated by preganglionic sympathetic fibers from the greater thoracic nerve. These fibers synapse on the cells in the adrenal medulla, causing a systemic sympathetic response. Other preganglionic fibers from the greater thoracic nerve synapse in the celiac ganglion; the postganglionic fibers from this ganglion distribute along branches of the celiac trunk. The preganglionic fibers from the lesser thoracic splanchnic nerve synapse in the aorticorenal ganglion--postganglionic processes from this ganglion supply vascular smooth muscle of branches of the renal artery and suprarenal arteries. The preganglionic fibers of the least thoracic splanchnic nerve synapse in the renal plexus.
The anterior vagal trunk has a gastric and hepatic branch, supplying parasympathetic fibers to the stomach and liver. The posterior vagal trunk supplies some parasympathetic fibers to the stomach, but it also sends a celiac branch to the celiac plexus. The fibers from the posterior vagal trunk which pass to the celiac plexus eventually distribute to the organs of the abdomen, all the way to the last third of transverse colon.

The suprarenal medulla is directly innervated by preganglionic sympathetic fibers from the greater thoracic splanchnic nerve. These preganglionic fibers synapse on the cells of the adrenal medulla, causing the cells in the adrenal medulla to release norepinephrine and/or epinephrine. The preganglionic fibers can synapse on these cells of the adrenal medulla because they are modified nervous tissue. The epinephrine and norepinepherine enters the blood stream to cause a systemic response.

This patient has Pott's disease, which is tuberculosis of the spine. Tuberculosis of the spine frequently occurs in untreated tuberculosis in young individuals, especially those on a poor diet. The tubercle bacilli enter through the respiratory tract and pass from lungs to systemic circulation. The bacilli tend to lodge in the bone marrow of the spine, including the lumbar vertebrae. An infection in the lumbar vertebrae may pass to the psoas major muscle, since psoas major takes origin from the lumbar vertebrae. This infection can cause an abscess in psoas major, which will be contained by the fascial sheath of the muscle. The psoas major muscle arises from the bodies of the lumbar vertebrae, passes under the inguinal ligament, and joins with the iliacus to insert on the lesser trochanter of the femur as the iliopsoas tendon. Psoas major passes through the superomedial part of the thigh, so an infection in this muscle matches with the location of the pus. None of the other muscles are closely associated with the lumbar vertebrae or found in the superomedial thigh, so they could not have been ones infected.

Remember back to the thorax--the vagus joins the esophageal plexus and covers the esophagus. The anterior and posterior vagal trunks form from the esophageal plexus-- they pass into the abdomen through the esophageal hiatus, on the anterior and posterior surfaces of the esophagus. The aortic hiatus is deep to the median arcuate ligament--it transmits the aorta and the thoracic duct. The caval foramen is found in the central tendon of the diaphragm; it transmits the inferior vena cava. Psoas major is deep to the medial arcuate ligament, and quadratus lumborum is deep to the lateral arcuate ligament.

The kidney is surrounded by a perirenal fatty capsule, the renal (Gerota's) fascia and pararenal fat. The fat offers no resistance to hemorrhage, but blood is contained in the renal fascia. This means that blood would not flow toward the body wall, other kidney, or toward the diaphragm. However, a kidney injury might involve part of the urinary collecting system, and blood from such damage would travel into the ureters and bladder.

The suprarenal medulla is directly innervated by preganglionic sympathetic fibers from the greater thoracic splanchnic nerve. These preganglionic fibers synapse on the cells of the adrenal medulla, causing the cells in the adrenal medulla to release norepinephrine and/or epinephrine. The preganglionic fibers can synapse on these cells of the adrenal medulla because they are modified nervous tissue. The epinephrine and norepinepherine enters the blood stream to cause a systemic response. The superior suprarenal arteries branch from the inferior phrenic, the middle suprarenal artery is a direct branch of the abdominal aorta, and the inferior suprarenal arteries are branches of the renal artery. Although the vein from the right gland drains into the inferior vena cava, the vein from the left suprarenal gland drains into the left renal vein. Finally, the pararenal space is the space outside the renal fascia, covered with the pararenal fat. The suprarenal gland is covered by the renal fascia, so it's in the perirenal space, not in the pararenal space.

During open abdominal surgeries (i.e., hysterectomy), retractor blades are used to keep the abdominal cavity open. The blade may come to rest on the femoral nerve as it lies between the iliacus and the lateral side of the psoas major muscle. So, the femoral nerve can be easily injured or crushed during abdominal surgery. If this nerve is injured, the patient will experience some numbness on her leg, and she will be unable to extend her knee. In this case, both the symptoms and the history of abdominal surgery point to damage to the femoral nerve.
The genitofemoral nerve pierces the psoas major muscle before entering the pelvis. The iliohypogastric nerve and lateral femoral cutaneous nerve emerge at the lateral border of psoas major and then travel laterally. The obturator nerve is at the medial border of psoas major. None of these other nerves are in the right position to be injured by the retractor blades. For a picture of these nerves of the lumbar plexus, see Netter Plate 464.

Each kidney is embedded in two layers of fat, with a membrane (the renal fascia), in between the layers. Inside the renal fascia, and directly atop the kidney, is the perirenal fat. Outside the renal fascia, you will find the pararenal fat, which is an elaboration of extraperitoneal connective tissue. Although the kidney is not peritonealized, the peritoneum from the posterior body wall lies over the anterior surface of the pararenal fat. The kidney is not a secondarily retroperitoneal organ--it began development in the retroperitoneum. So, it does not have a fusion fascia.

Remember that the inferior vena cava is a little off center, on the right side of the abdomen. This means that structures on the right might be closely associated with this vessel, while structures on the left will need to have longer venous channels to connect with the IVC and drain into it. In the case of the suprarenal glands, you can see that the IVC is laying over the right suprarenal gland and is very far from the left gland. (This means that the right gland is draining directly into the inferior vena cava, while the left gland is draining into the renal vein.) As far as the other structures in the question go... The aorta lies fairly evenly between the suprarenal glands--it is not overlying either gland. The left hepatic vein, which drains blood from the liver to the inferior vena cava, is superior to the kidneys and not really involved with this area. The right crus of the diaphram is a set of fibers that splits to make the esophageal hiatus, and the right renal artery is a branch off the aorta to the kidney which enters the kidney below the level of the suprarenal gland.

In 25-50% of cases, the inferior portion of the thoracic duct includes a dilated portion called the cisterna chyli. When present, all of the lymph trunks draining the abdomen and lower limbs dump into it, as well as the most inferior intercostal lymph trunks. When it is not present, these trunks simply empty into the thoracic duct. So, the cisterna chyli is a portion of the thoracic duct, and the thoracic duct passes through the diaphragm with the aorta at the T12 level. The inferior vena cava passes through the central tendon of the diaphragm at the T8 level. The esophagus and vagal branches pass through the right crus of the diaphragm at the T10 level. The greater thoracic splanchnic nerves pass through the fibers of the left and right crus.

The right crus is the part of the diaphragm that takes origin from L1-L3. It splits to enclose the esophagus. So, in the case of an esophageal hernia, the herniating stomach would be entirely surrounded by the fibers of the right crus. The left crus is the part of diaphragm that takes origin from L1 and L2. It is smaller and shorter than the right crus, and it intermingles with the right crus around the aortic hiatus. It does not contribute to the esophageal hiatus. The central tendon is the tendon in the middle of the diaphragm where all the fibers of the diaphragm attach. It provides an opening for the inferior vena cava. Finally, sternal and costal fibers refer to muscle fibers in the diaphragm that take origin from the xyphoid process or the ribcage. This could not refer to the right crus, since it originates on the lumbar vertebrae.

The sympathetic fibers in the greater thoracic splanchnic nerve are preganglionic sympathetic fibers that have left the sympathetic chain and are going to synapse in abdominal ganglia. These preganglionic sympathetic fibers originate in the lateral horn of the spinal cord grey matter. The celiac ganglia and the superior mesenteric ganglia are the two ganglia where the fibers from the greater thoracic splanchnic nerve can go to synapse. Finally, remember that these fibers did not originate in the chain ganglia--the fibers from there are the postganglionic sympathetic fibers.

The aortic hiatus is not in the central tendon of the diaphragm--the caval opening, for the inferior vena cava, is found in the central tendon of the diaphragm. The aortic hiatus is formed by the median arcuate ligament, which unites the two crura of the diaphragm. The vertebrocostal trigone is an area of the diaphragm superior to the lateral arcuate ligament. Here, the diaphragmatic muscle is deficient and the trigone is closed primarily by the inferior and superior fascia of the diaphragm. It is a significant area for hernias. The esophageal hiatus is formed entirely by the fibers of the right crus. The psoas major muscle passes behind the medial arcuate ligament. Finally, the right phrenic nerve passes through the central tendon of the diaphragm, near the vena caval foramen. See Netter Plate 181 for a picture of all these structures and their relationships.

Since the inferior vena cava is on the right side of the abdomen, structures on the left will need to have longer venous channels to connect to the IVC and drain into it. Consequently, some of the paired retroperitoneal structures that drain directly into the IVC on the right side cannot do that on the left. Instead, they must drain into the renal vein, which crosses over the aorta and under the superior mesenteric artery to connect to the inferior vena cava. The left inferior phrenic vein, left suprarenal vein, and left ovarian/testicular vein all drain into the left renal vein (although their analogs on the right side drain directly into the IVC). If the left renal vein was ligated as it crosses the aorta, blood from the left diaphragm, ovary, and suprarenal gland would have to drain posteriorly - into the left second lumbar vein, which connects to the posterior aspect of the left renal vein. The pancreas drains into the portal venous system and would not be affected by this ligation.

The obturator nerve runs along the medial border of the psoas major muscle, eventually passing through the obturator canal to innervate muscles of the medial thigh. So, it might be damaged by an injury to the medial portion of psoas major. The femoral nerve runs along the lateral border of psoas major, where psoas major contacts iliacus. The genitofemoral nerve pierces through psoas major at the level of L3 or L4. The iliohypogastric and ilioinguinal nerves run under psoas major, emerging at the lateral border of psoas major to run over quadratus lumborum. The way to distinguish between these two nerves is to remember that the iliohypogastric is superior to the ilioinguinal nerve.

The celiac plexus of nerves contains fibers from the greater thoracic splanchnic nerves, which are synapsing in the celiac ganglia. This plexus also contains vagal fibers. Even though the vagus does not synapse in the celiac ganglia, it passes through the ganglia and contributes to the celiac plexus. This allows the vagal fibers to travel on arteries to reach their eventual targets. The lesser thoracic splanchnic nerves are not part of the celiac ganglia--these nerves synapse in the aorticorenal ganglia and contribute to the renal plexus. The first lumbar splanchnic nerve may occasionally contribute to the celiac plexus.