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Anatomy Other:

In horseshoe kidney, both kidneys are fused together at the poles in early embryonic life. The isthmusof horseshoe kidney usually lies anterior to the aorta and inferior vena cava and posterior to theinferior mesenteric artery. This centrally located isthmus gets trapped behind the inferior mesentericartery during the relative ascent of the kidney

The inferior vena cava courses through the abdomen and inferior thorax in a location anterior to theright half of the vertebral bodies. The renal veins join the IVC at the level of L1/L2, and the commoniliac veins merge to become the IVC at the level of L4.

The left ventricle forms the apex of the heart and reaches as far as the fifth intercostal space in the leftmidclavicular line. The other chambers of the heart lie to the right of the left midclavicular line andwould not be affected by penetrating injury in this location.

The right atrium receives venous blood from both the superior vena cava and the inferior vena cava.The right atrium makes up the majority of the right border of the heart on PA chest films. The rightventricle forms the anterior wall of the heart and is best seen on lateral chest X-rays . The SVC andIVC compose the superior and inferior borders of the cardiac silhouette on the right side

A penetrating injury at the left sternal border in the fourth intercostal space would puncture theanterior surface of the heart. The right ventricle composes most of the hearts anterior surface.

Prolonged exposure to loud noises causes hearing loss due to damage of the stereociliated hair cells ofthe organ of Corti.

The recurrent laryngeal nerve travels in close approximation to the inferior thyroid artery and can beinjured in surgical procedures of the anterior neck (e.g. thyroidectomy), resulting in laryngeal muscle

paralysis, hoarseness and dyspnea. The coronary sinus communicates freely with the right atrium and therefore may become dilated

secondary to any factor that causes right atrial dilatation. The most common such factor is pulmonaryartery hypertension which leads to elevated right heart pressures.

The brachiocephalic vein drains the ipsilateral jugular and subclavian veins. The bilateral brachiocephalic veins combine to form the SVC. Brachiocephalic vein obstruction causes symptomssimilar to those seen in SVC syndrome but on just one side of the body.

Blunt trauma to the globe can cause orbital blow out fractures. These fractures most commonlyinvolve the medial or inferior orbital walls, because the bone bordering the ethmoid and maxillarysinuses is thin.

The inferior vena cava courses through the abdomen and inferior thorax in a location anterior to theright half of the vertebral bodies. The renal veins join the IVC at the level of L1/L2, and the commoniliac veins merge to become the IVC at the level of L4.

The external branch of the superior laryngeal nerve is at risk of injury during thyroidectomy due to its proximity to the superior thyroid artery and vein. This nerve innervates the cricothyroid muscle.

Low-frequency sound is best detected at the apex of the cochlea near the helicotrema. High-frequencysound is best detected at the base of the cochlea near the oval and round windows.

A branch of the mandibular division of the trigeminal nerve (CN V3) provides somatic sensoryinnervation to the anterior 2/3 of the tongue. The chorda tympani branch of the facial nerve providestaste sensation from the anterior 2/3 of the tongue. The glossopharyngeal nerve (CN IX) providessomatic sensory and taste innervation to the posterior portion of the tongue.

The oculomotor nerve (CN Ill), ophthalmic nerve (CN VI) branches, trochlear nerve (CN IV),abducens nerve (CN VI), and superior ophthalmic vein enter the orbit via the superior orbital fissure.

Apical lung tumors are called Pancoast tumors. Pancoast tumors can cause Homer syndrome, SVCsyndrome, arm weakness, arm paresthesias, and hoarseness.

A pudendal nerve block can be performed by injecting anesthetic intravaginally in the region of theischial spine. Blocking the pudental nerve provides anesthesia to the majority of the perineum;additional blockade of the genitofemoral and ilioinguinal nerves would provide complete perineal andgenital anesthesia.

Lymph from the testes drains through lymph channels directly back to the retroperitoneal (paraaortic)lymph nodes. On the other hand lymph from the scrotum drains to the inguinal lymph nodes

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Aortic rupture is most commonly due to motor vehicle accidents and the most common site of injury isthe aortic isthmus, which is the connection between the ascending and descending aorta distal to wherethe left subclavian artery branches off the aorta.

The middle meningeal artery is a branch of the maxillary artery that enters the skull at the foramenspinosum and courses intracranially deep to the pterion. Skull fractures at this site may causelaceration of this vessel leading to an epidural hematoma.

The inferior wall of the left ventricle forms most of the diaphragmatic surface of the heart. The posterior descending artery supplies this area. In 85-90% of individuals the posterior descending arteryderives from the right coronary artery.

The lung apices extend above the level of the clavicle and first rib through the superior thoracicaperture. Penetrating injury in this area may lead to pneumothorax.

Aspirated or inhaled particles are most likely to become lodged in the right main bronchus or its branches because this bronchus is shorter, wider and more vertically oriented than the left main bronchus.

Thoracocentesis should be performed above the 7th rib in midclavicular line, the 9th rib alongmidaxillary line and the 11th rib along posterior scapular line. Insertion of a needle lower than these

points increases the risk of penetrating abdominal structures, and insertion of the needle on the inferiormargin of the rib risks striking the subcostal neurovascular bundle.

Irritation of the mediastinal or diaphragmatic parietal pleura will cause sharp pain, worse oninspiration, in the C3-C5 distribution. Pain sensation from these areas is carried by the phrenic nerve.Pleuritic chest pain can result from any condition that causes inflammation of the pleura. The pleura isdivided into following segments, as follows:

1. Visceral pleura: The visceral pleura, or pulmonary pleura, covers all surfaces of the lungs,including the surfaces within the pulmonaryfissures.

2. Parietal pleura: This represents the remainder of the pleura that is not in contact with thelungs and can be subdivided as follows:- Costal pleura: Covers the thoracic wall including the ribs sternum intercostal spaces costalcartilages and the sides of the thoracic vertebrae- Mediastinal pleura: Covers the mediastinum- Diaphragmatic pleura: Covers the surface of the diaphragm located within the thoraciccavity- Cervical pleura: Extends with the apices of the lung into the neck

The left kidney lies immediately deep to the tip of the 12 th rib on the left. The portal vein can be identified on cross-sectional scans lying in or near the right side of the liver and

anterior to the inferior vena cava. The pressure in the portal system is elevated in liver cirrhosis. The great saphenous vein is a superficial vein of the leg that collects blood from the foot near the

medial malleolus before coursing up the medial aspect of the leg and thigh to drain into the femoralvein within the femoral triangle immediately inferior to the pubic tubercle.