Osmosis Anatomy

The pulmonary arteries carry oxygenated blood. True False

False Main Explanation The pulmonary arteries carry deoxygenated blood away from the heart towards the lungs. Remember the 'A' in artery stands for 'away' from the heart.

The parietal pleura is immediately adjacent to the lung. True False

False Main Explanation The visceral pleura is immediately adjacent to the lung, while the parietal pleura is the outer membrane.

A high school football player suffers a traumatic knee injury after an opposing player dives into the lateral aspect of his knee. Which structure(s) in the knee are most vulnerable in such an injury? A. Anterior cruciate ligament, medial collateral ligament, medial meniscus B. Anterior cruciate ligament, medial collateral ligament, posterior cruciate ligament C. Anterior cruciate ligament, lateral collateral ligament, posterior cruciate ligament D. Anterior cruciate ligament, medial meniscus, posterior cruciate ligament E. Lateral collateral ligament, medial collateral ligament, posterior cruciate ligament

A. Anterior cruciate ligament, medial collateral ligament, medial meniscus. Main Explanation A common injury resulting from lateral-to-medial knee trauma is injury to the "O'Donoghue tear," or "Unhappy Triad", which consists of the medial collateral ligament, the lateral meniscus, and the anterior cruciate ligament. Note: the lateral meniscus is in the refined definition; originally it was the medial meniscus.

An indirect inguinal hernia... A. passes through the deep and superficial inguinal rings AND lateral to the inferior epigastric vessels. B. passes through only the deep and inguinal ring AND lateral to the inferior epigastric vessels. C. passes through the deep and superficial inguinal rings AND medial to the inferior epigastric vessels. D. passes through only the deep inguinal ring AND medial to the inferior epigastric vessels.

A. passes through the deep and superficial inguinal rings AND lateral to the inferior epigastric vessels. Main Explanation In an indirect hernia a pouch of peritoneum and frequently associated bowel follow the course of the spermatic cord into the scrotum. The peritoneal pouch must pass lateral to the inferior epigastric vessels and through the deep then superficial inguinal rings.

Contracting the diaphragm and external intercostal muscles is responsible for _____ whereas contracting the abdominal and internal intercostal muscles is responsible for ______. A. quiet inspiration...forced expiration B. quiet expiration...forced inspiration C. quiet expiration...forced expiration D. forced inspiration...quiet inspiration

A. quiet inspiration...forced expiration Remember that external intercostals are responsible for inspiration whereas internal intercostals contribute to expiration. Main Explanation Inspiration occurs due to the expansion of the chest cavity (thus creating negative pressure, leading to atmospheric air entering the lungs) from the contraction (flattening) of the diaphragm ## (75% of passive inspiration) as well as the lifting of the chest wall by the external intercostals (25% of passive inspiration). Expiration, on the other hand, is usually a ## passive process involving relaxation of these muscles and natural lung elasticity. Forced/active expiration can be accomplished by contracting the abdominals and internal intercostal muscles.

A problem with which of the following embryological derivatives would most affect tooth formation? A. neuroectoderm B. neural crest C. pseudoderm D. surface ectoderm E. mesoderm F. Endoderm

Anwer: (B) Neural crest Main Explanation Neural crest forms the teeth (odontoblasts; remember Crest toothpaste), peripheral nerves (cranial nerves, dorsal root ganglion, celiac ganglion, autonomic nervous system, Schwann cells), cranial bones, arachnoid and pia mater, melanocytes, and Chromaffin cells of the adrenal medulla. A. neuroectoderm Comprises neurons, glial cells, retina, and spinal cord B. neural crest Teeth (odontoblasts; remember Crest toothpaste), peripheral nerves (cranial nerves, dorsal root ganglion, celiac ganglion, autonomic nervous system, Schwann cells), cranial bones, arachnoid and pia mater, melanocytes, and Chromaffin cells of the adrenal medulla. C. pseudoderm pseudo-skin, or an outer-covering in sponges. NOT a germ layer. D. surface ectoderm Forms the epidermis, glands (sweat, salivary, mammary), eye lens, olfactory epithelium, sensory organs of the ear, among others. Associated with craniopharyngioma, which is a benign Rathke's pouch tumor characterized by cholesterol crystals and calcifications. E. mesoderm Develops into muscle, connective tissue, peritoneum (serous linings), bone, heart, lymphatics, kidneys, testes, ovaries, vagina, urethra, spleen, etc. A mnemonic for mesodermal defects is VACTERL: Vertebral defects, Anal atresia, Cardiac defects, TracheoEsophageal fistula, Renal defects, Limb defects. Fendoderm F. Endoderm Forms the gut tube epithelium and derivatives, such as pancreas, thymus, thyroid follicular cells, parathyroid, liver, lungs).

Damage to which of the following nerves will most likely affect the adductor muscles? Aobturator nerve Bsuperior gluteal nerve Cinferior gluteal nerve Dnerve to obturator internus Enerve to quadratus femoris

Aobturator nerve Main Explanation The obturator nerve innervates the adductors muscles of the lower extremity (external obturator, adductor longus/brevis/magnus, and gracilis) and provides sensory innervation to the skin on the medial aspect of the thigh. A. obturator nerve The obturator nerve innervates the adductors muscles of the lower extremity (external obturator, adductor longus/brevis/magnus, and gracilis) and provides sensory innervation to the skin on the medial aspect of the thigh. B. superior gluteal nerve The superior gluteal nerve innervates the gluteus medius, gluteus minimus, and the tensor fascia latae. Damage to the superior gluteal nerve can result in the Trendelenburg gait; a positive Trendelenburg sign is when the pelvis sags towards the normal unsupported side (the swing leg). C. inferior gluteal nerve The inferior gluteal nerve innervates the gluteus maximus. When damaged, one may develop gluteus maximus lurch (lurching backwards to compensate for lack in hip extension). D. nerve to obturator internus The nerve to obturator internus innervates the obturator internus and gemellus superior muscles. E. nerve to quadratus femoris The nerve to quadratus femoris is a sacral plexus nerve that innervates the quadratus femoris and gemellus inferior muscles.

Which cranial nerve provides general somatic efferents to the intrinsic and extrinsic muscles of the tongue? A. Glossopharyngeal nerve (IX) B. Hypoglossal nerve (XII) C. Trochlear (IV) D. Facial (VII)

B. Hypoglossal nerve (XII) The Hypoglossal nerve (CN XII) has the following features: General Somatic Efferent-motor to intrinsic & extrinsic muscles of the tongue Nucleus in medulla.

An infant is born with a nasolacrimal duct that has failed to develop a lumen. Between which two of facial prominences does the nasolacrimal duct develop? A. Lateral nasal and mandibular B. Lateral nasal and maxillary C. Maxillary and mandibular D. Medial nasal and maxillary E. Right and left medial nasal

B. Lateral nasal and maxillary Main Explanation Option B (lateral nasal and maxillary) is correct. The nasolacrimal duct develops from an ectodermal thickening in the floor of the nasolacrimal groove between the lateral nasal and maxillary prominences. The epithelial cord normally canalizes via cell degeneration between the lacrimal sac and inferior nasal meatus. but this degeneration may fail to occur.

A 26 year old dancer is learning some new moves and while practicing, she develops severe pain in her right hip. She is diagnosed with synovitis related to overuse injury, and she ask you to explain more about synovitis and synovial joints. Which of the following is true about synovial joints? A. The synovial membrane encases bursae B. The sternoclavicular joint is a synovial joint C. The synovial membrane encases ligaments D. The synovial membrane encases the joint capsule E. The synovial membrane encases tendons

B. The sternoclavicular joint is a synovial joint Main Explanation Synovial joints, in contrast to solid joints which can be fibrous or cartilaginous, are joints where the involved bones are separated by a narrow articular cavity and usually have an extensive range of motion. Characteristic features include a layer of hyaline cartilage covering the articular surfaces of the involved bones, and a joint capsule consisting of the inner synovial membrane and outer fibrous membrane. Although the sternoclavicular joint does not have an extensive range of motion, is a synovial joint. Synovitis is inflammation of the synovial membrane - a physiologically active layer of tissue surrounding "synovial" joints in order to produce lubricating fluid. Transient synovitis of the hip is an acute and self-limited pediatric diagnosis that is rarely seen in adults and often requires no treatment. Synovitis in adults can have many causes including infection or autoimmune conditions such as lupus, however in a young, healthy, physically active person it's likely due to overuse injury.

Which artery provides blood flow into the ligament of the head of the femur? A. superior gluteal B. medial circumflex femoral C. Inferior gluteal D. obturator E. lateral circumflex femoral

B. medial circumflex femoral Main Explanation Specifically, the acetabular branch of the medial circumflex femoral artery supplies the head of the femur by going through the ligament of the head of the femur.

A(n) ________ inguinal hernia ruptures through the posterior wall of the inguinal canal, leaving the abdominal cavity medial to the deep ring and medial to the inferior epigastric vessels. AIndirect BDirect

BDirect A DIRECT inguinal hernia does not use the deep inguinal ring when entering the inguinal canal; rather, the hernial sac passes through or around the conjoint tendon and directly to the superficial inguinal ring. An INDIRECT inguinal hernia passes through the abdominal wall by entering the deep inguinal ring, passing through the inguinal canal, and emerging through the superficial inguinal ring. This type of hernia follows the course taken by the testis and ductus deferens (or round ligaments in females). Thus, the indirect inguinal hernia leaves the abdominal cavity LATERAL to the inferior epigastric vessels (the epigastric vessels are medial to the deep inguinal ring).

A 33-year-old basketball player presents with severe pain in his right ankle. He tells you that he was running to make a basket and when he stopped and turned to jump and shoot the ball, he felt as though someone struck the back of his ankle "with a sledgehammer." He also heard a "pop." On exam, the patient is able to walk, although he is limping. He is able to dorsiflex and plantar flex both feet. You ask the patient to kneel on a chair and you squeeze the right gastrocnemius muscle belly and notice that there is no resulting plantar flexion. Which of the following is associated with this type of injury? AAge under 10 years old BFluoroquinolone use CMacrolide use DFemale sex ENone of the above

BFluoroquinolone use The mechanisms of injury described in the question (pivoting, jumping) are both associated with rupture of the achilles tendon. Pain in achilles tendon injury tends to occur 2 to 6cm proximal to the tendon's insertion. Patients may still be able to walk and dorsiflex/plantar flex the ankle. The test that the doctor performs is called the Thompson Test. Squeezing the gastrocnemius muscle should lead to plantar flexion. When it does not, this is a positive Thompson test. In one study of 174 patients, the test was found to have over 90% sensitivity and specificity for tendon rupture. Fluoroquinolones (like ciprofloxacin) have been associated with Achilles tendinopathy and tendon rupture, although the risk seems to be very low. For serious athletes, it is recommended that the amount of activity be reduced while the athlete is on fluoroquinolones. http://www.uptodate.com/contents/achilles-tendinopathy-and-tendon-rupture?source=see_link#H27 http://www.ncbi.nlm.nih.gov/pubmed?term=9548122 Age is a risk factor for Achilles tendon rupture, but the risk actually peaks in the 30-to-40-year-old age range. There is no association between macrolide use and Achilles tendon rupture Male sex is actually considered a risk factor of achilles tendon rupture. Note that in addition to fluoroquinolones, glucocorticoids also raise the risk of tendon rupture. The patient in this case is loosely based off of Kobe Bryant since he was likely not using fluoroquinolones prior to the injury. The site of pain in the posterior ankle may help you to narrow your differential diagnosis. With heel pain, you may want to consider bursitis, enthesopathy, and plantar fasciitis. The pain associated with achilles tendonitis or achilles tendon rupture is higher up. Achilles tendon rupture may be obvious on clinical exam, but ultrasound can also be useful to confirm the diagnosis.

Injury to which nerve would result in gluteus medius limp or "pelvic slump"? ASciatic nerve BSuperior gluteal nerve CInferior gluteal nerve DFemoral nerve

BSuperior gluteal nerve A. Sciatic nerve Damage to this nerve would affect the hamstrings and all of the muscles below the knee. This would cause severe impairment of knee flexion and immobilize the foot--> "foot-drop". Additionally, there would be sensory loss to leg, foot, and sole of foot except on the medial side . B. Superior gluteal nerve Abductors and medial rotators of the thigh work to level pelvis when the opposite leg is raised. The abductors and medial rotators of the thigh (gluteus minimus, gluteus medius, and tensor fascia lata) are all innervated by the superior gluteal nerve. C. Inferior gluteal nerve Innervates the gluteus maximus, which extends, laterally rotates, and steadies the thigh. This would impair hip extension and lateral rotation and create difficulty in raising the body from a sitting or stooping position. D. Femoral nerve Damage to this nerve would cause paralysis of the quadriceps femoris, loss of knee extension, and sensory loss to anterior and medial side of thigh, medial side of lower leg, and medial border of foot up to the big toe. Main Explanation Damage to the superior gluteal nerve can result in Trendelenburg's Sign.

What muscle runs between the two sesamoid bones at the distal end of the first metatarsal? A. flexor digitorum longus B. extensor hallucis longus C. flexor hallucis longus D. extensor digitorum longus

C. flexor hallucis longus Main Explanation Flexor hallucis longus runs between the two sesamoid bones so that it can contract even as full body weight is supported on the first metatarsal head at the toe-off phase of gait. Flexor hallucis longus is part of the plantarflexor group of muscles that provide forward and upward acceleration during toe-off.

What are the normal phases of gait, in order? A. flat foot, heel strike, toe off, swing B. swing, heel strike, toe off, flat foot C. heel strike, flat foot, toe off, swing D. heel strike, flat foot, swing, toe off

C. heel strike, flat foot, toe off, swing Main Explanation The two main phases of gait are Stance and Swing. Stance consists of heel strike, flat foot, and finally toe off right into the Swing phase.

Blood supply to the descending colon is provided by the ________. A. superior mesenteric artery B. celiac trunk C. inferior mesenteric artery D. external iliac artery

C. inferior mesenteric artery Main Explanation Oxygenated blood reaches the GI tract via three midline branches. The celiac trunk leaves the aorta around T12 and supplies foregut structures (liver, gallbladder, spleen, pancreas, 1st part of the duodenum). The superior mesenteric artery leaves the aorta near L1 and supplies midgut structures (2nd part of the duodenum to the proximal 2/3 of the transverse colon). The inferior mesenteric artery leaves the aorta near L3 and supplies hindgut structures (distal 1/3 of the transverse colon to the superior rectum).

Which of the following best describes the basic structure of a sympathetic motor nerve? A. Long preganglionic axons & short postganglionic axons, with ganglia very close to the target tissues B. Long preganglionic axons & short postganglionic axons, with ganglia very close to the spinal cord C. Short preganglionic axons & long postganglionic axons, with ganglia very close to the spinal cord D. Short preganglionic axons & long postganglionic axons, with ganglia very close to the target tissues

C. Short preganglionic axons & long postganglionic axons, with ganglia very close to the spinal cord Main Explanation Sympathetic nerves have short preganglionic axons & long postganglionic axons. Thus, their ganglia are found very close to the spinal cord (pre/paravertebral). On the other hand, parasympathetic nerves have very long preganglionic axons & short postganglionic axons. This results in their ganglia lying very close to or within their target tissues. In the image below, sympathetics are shown in red and parasympathetics in blue. Note that most sympathetic ganglia lie close to the spinal cord whereas most parasympathetic preganglionic axons extend to the target tissues.

Gluteus medius and minimus, as well as tensor fascia latae, are abductors of the hip. Which of the following nerves are these hip abductors innervated by? A. nerve to quadratus femoris B. inferior gluteal nerve C. superior gluteal nerve D. obturator nerve E. nerve to obturator internus

C. superior gluteal nerve Main Explanation The superior gluteal nerve innervates the gluteus medius, gluteus minimus, and the tensor fascia latae. Damage to the superior gluteal nerve can result in the Trendelenburg gait; a positive Trendelenburg sign is when the pelvis sags towards the ## normal unsupported side (the swing leg). A. Nerve to the Quadratus femoris: The nerve to quadratus femoris is a sacral plexus nerve that innervates the quadratus femoris and gemellus inferior muscles. B. Inferior gluteal nerve The inferior gluteal nerve innervates the gluteus maximus. When damaged, one may develop ## gluteus maximus lurch (lurching backwards to compensate for lack in hip extension). C. superior gluteal nerve The superior gluteal nerve innervates the gluteus medius, gluteus minimus, and the tensor fascia latae. Damage to the superior gluteal nerve can result in the Trendelenburg gait; a positive Trendelenburg sign is when the pelvis sags towards the normal unsupported side (the swing leg).

A 33-year-old basketball player presents with severe pain in his right ankle. He tells you that he was running to make a basket and when he stopped and turned to jump and shoot the ball, he felt as though someone struck the back of his ankle "with a sledgehammer." He also heard a "pop." On exam, the patient is able to walk, although he is limping. He is able to dorsiflex and plantar flex both feet. You ask the patient to kneel on a chair and you squeeze the right gastrocnemius muscle belly and notice that there is no resulting plantar flexion. Which injury is most likely in this case? ARetrocalcaneal bursitis BAnkle sprain CEnthesopathy DAchilles tendon rupture ENone of the above

D Achilles tendon rupture The mechanisms of injury described in the question (pivoting, jumping) are both associated with rupture of the achilles tendon. Pain in achilles tendon injury tends to occur 2 to 6cm proximal to the tendon's insertion. Keep in mind that, even with an achilles tendon rupture, patients may be able to walk and dorsiflex/plantar flex the ankle. The test that the doctor performs is called the Thompson Test. Squeezing the gastrocnemius muscle should lead to plantar flexion. When it does not, this is a positive Thompson test. In one study of 174 patients, the test was found to have over 90% sensitivity and specificity for tendon rupture. A Retrocalcaneal bursitis This is on the differential diagnosis for posterior heel pain but the pain is lower down than achilles pathology. The retrocalcaneal bursa is located between the calcaneal bone and the Achilles tendon. It cushions impact when walking. It may be confused with Achilles tendonitis. There may be swelling (on the lateral or medial side of the achilles tendon), tenderness or redness of the posterior heel. C Enthesopathy This is on the differential diagnosis for posterior heel pain but the pain is lower down than achilles pathology. You would expect tenderness of the site of insertion of the Achilles tendon.

Which nerve injury would be associated with high "steppage gait" with foot slap and foot drop? A superior gluteal nerve B obturator nerve C superficial fibular nerve D deep peroneal nerve

D Deep peroneal nerve High "steppage gait" with foot slap and foot drop is seen when an individual with weak dorsiflexors attempts to avoid dragging their toes on the ground by lifting up their leg. Weak dorsiflexors suggests that the associated nerve injury would be to the common fibular nerve, or more appropriately, the deep peroneal nerve (aka deep fibular nerve).

A 25-year-old man who has suffered blunt trauma to his head has a suspected injury to his superior rectus muscle. What eye movements might be compromised if this indeed were the case? A. Abduction only B. Abduction and elevation C. Adduction and depression D. Adduction and elevation E. Extorsion and elevation

D. Adduction and elevation Main Explanation Simple definition question but important! The superior rectus muscle is a simple bridge-like muscle above the eye that operates dorsomedially and so results in elevation and adduction of the eye. The superior oblique muscle is responsible for depressing and abducting the eye while the inferior oblique muscle is responsible for elevating and abducting the eye.

A 30-year-old man sustains significant shoulder trauma during a motor vehicle accident. Other than ligamentous damage, x-ray shows only an avulsion fracture of the tip of the coracoid process. Which shoulder movement would be expected to be most impaired? A. Abduction B. Extension C. External rotation D. Flexion E. Inversion

D. Flexion Main Explanation The coracobrachialis and the short head of the biceps brachii originate at the coracoid process. An avulsion fracture (where a small piece of bone is broken off while still attached to tendon or ligament - in this case tendon) of the coracoid process would prevent these muscles from exertion their main action at the shoulder joint, which is flexion (D). Other muscles responsible for shoulder flexion include the anterior deltoid and the pectoralis major. Supraspinatus and deltoid are responsible for shoulder abduction (A). Shoulder extension (B) is mostly due to the latissimus dorsi and the posterior deltoid. External rotation (C) is mostly due to teres minor, infraspinatus, and posterior deltoid. Inversion (E) is not an action that occurs at the shoulder (it occurs in the ankle). Memorizing all of these actions is unnecessary - knowing the location of the coracoid process (palpable on exam near the deltopectoral triangle) is sufficient in this case. The question stem is asking for the effect on the shoulder, so (A), (B), and (C) would not be possible given the anterior location of the coracoid process in relation to the humerus. Shoulder motion can be confusing: Shoulder flexion is the motion where the arm is raised up (toward superior direction, as in lifting a child). Adduction is always a motion towards the body, shoulder adduction occurs when you slapping someone across the face. Abduction is moving away from the body. shoulder abduction is opposite of above - imagine backslapping that person with the same hand.

A 27 year-old woman is brought to the emergency room by ambulance after a car accident. She is complaining of a severe headache and is somewhat disoriented. Her heart rate is 110 and her blood pressure is 134/72. She has several abrasions of her face with some swelling and ecchymosis. She has a dark ecchymosis over her right mastoid process. CT scan of the head shows an intracranial hemorrhage that does not cross suture lines. The anatomic structure that passes through which of the following foramina has most likely been damaged? A. Carotid canal B. Foramen magnum C. Foramen rotundum D. Foramen spinosum E. Optic canal

D. Foramen spinosum Main Explanation This patient has a basilar skull fracture secondary to trauma sustained in a car accident. Battle's sign, ecchymosis over the mastoid process, is consistent with a basilar skull fracture. Also, this patient has an epidural hemorrhage as seen on CT scan ## (does not cross suture lines). This scenario is due to rupture of the middle meningeal artery, which passes through the foramen spinosum. The maxillary nerve (V2) passes through the foramen rotundum. The optic nerve and ophthalmic artery passes through the optic canal. The internal carotid artery passes through the carotid canal. The brainstem (specifically, the medulla), meninges, vertebral arteries, and the spinal roots of the accessory nerve all pass through the foramen magnum.

The renal _____ contains most of the nephron corpuscles and is also the primary site of erythropoietin synthesis. A. pyramids B. medulla C. pelvis D. cortex

D. cortex Main Explanation The peritubular epithelial cells in the renal cortex are primarily responsible for EPO synthesis

Known as the "widow maker," this artery often results in sudden death within minutes to hours when occluded. A. right anterior descending (RAD) coronary artery B. left circumflex artery (LCA) C. left pulmonary artery (LPA) D. left anterior descending (LAD) coronary artery

D. left anterior descending (LAD) coronary artery Main Explanation The LAD supplies about 50 percent of the left ventricle and in the majority of people reaches as far as the apex of the heart.

A 60 year old woman comes to your office for her follow-up visit after being hospitalized for an acute COPD exacerbation. She has a 30 pack year smoking history and complains of a chronic, productive cough. She is able to walk 50 feet before getting short of breath. On physical exam, there are decreased breath sounds bilaterally and crackles heard at both bases. It has been shown that cigarette smoking leads to goblet cell metaplasia and can contribute to the chronic bronchitis experienced by COPD patients. To what level do goblet cells extend in the respiratory tract? Aalveolar ducts Bbronchiole Crespiratory bronchiole Dterminal bronchiole

D. terminal bronchiole Main Explanation Also a characteristic of Barrett's esophagus, goblet cell metaplasia is a useful histological marker. Knowing where goblet cells should, and should not, be can help one make a histopathological diagnosis.

Damage to cranial nerve IV would be likely if a patient could not move his eye in which direction(s)? A. Superiorly B. Superiorly and laterally C. Inferiorly and laterally D. Inferiorly and medially E. Superiorly and medially

Depression, abduction, medial rotation of eyeball. The Trochlear nerve (CN IV) controls the superior oblique muscle that is responsible for movement inferiorly and laterally. The Abducens nerve (CN VI) controls movement laterally. The Oculomotor nerve (CN III) controls all other movements and opening of the upper eyelid. This is very important clinically.

A 75 year old man with no past medical history presents with jaundice, light-colored stools, and weight loss. He denies abdominal pain or irregularity of bowel function, but has felt a bulging lump in his right upper quadrant. You perform RUQ ultrasound but do not find anything. Next, you obtain a non-contrast abdominal CT and notice dilated biliary ducts throughout all of the liver parenchyma. The hepatic ducts, gallbladder, cystic duct, and common biliary duct all appear unremarkable. Which of the following lesions is likely given these findings? A. Cholelithiasis B. Tumor in the head of the pancreas C. Portal hypertension D. Gallstone ileus E. Cholangiocarcinoma

E. Cholangiocarcinoma Main Explanation Cholangiocarcinoma is cancer of the biliary system, excluding the gallbladder and ampulla of Vater. It can occur in three general regions: intrahepatic, peri-hilar, and extrahepatic. Of the three, perihilar cholangiocarcinoma (also referred to as a klatskin tumor) is the ## most difficult to detect on imaging and may require ** contrast-based imaging such as endoscopic retrograde cholangiopancreatography (ERCP) in order to clearly visualize the entire biliary system. This patient's findings, however, can only be described by a klatskin tumor. Dilated bile ducts throughout all of the liver parenchyma suggests that something outside the liver is compressing the biliary system and thereby affecting all upstream branches. Normal appearing hepatic ducts, gallbladder, cystic duct, and common duct implies that there are no masses in these regions. Thus, the obstruction must be exactly at the hilum of the liver. A. Cholelithiasis is Incorrect: This would normally present with pain, and ultrasound would also show the presence of stones. B. Tumor in the head of the pancreas is Incorrect: Tumors in the head of the pancreas would present with dilation of the proximal common bile duct, cystic duct, gallbladder, and hepatic ducts in addition to the biliary ducts within the liver parenchyma. C. Portal hypertension is incorrect. . There is no suggestion of portal hypertension in this patient's history D. Gallstone ileus is incorrect. This patient had no abdominal pain or bowel irregularity aside from light-colored stools, which is explained by limited biliary drainage.

A man falls asleep with his arm draped over a chair, and in the morning is unable to extend his wrist. The sensory deficit expected is: AEntire hand BEntire posterior arm CPalmar and dorsal aspects of the little finger and medial aspect of the ring finger DPalmar aspect and dorsal tips of the index and middle fingers E. Posterior arm and dorsal hand, not including the fingertips, little finger, ring finger, or medial aspect of the middle finger

E. Posterior arm and dorsal hand, not including the fingertips, little finger, ring finger, or medial aspect of the middle finger. Main Explanation This is "Saturday night palsy"! The radial nerve is the "great extensor" and it is important to know its sensory distribution (as well as those of the other nerves of the brachial plexus).

A 67 year-old woman complains of decreasing ability to make it to the bathroom before urinating. She reports that the problem started intermittently "a few years ago," but is now almost a daily occurrence. Past obstetric history is significant for six normal vaginal deliveries. You recommend daily exercises to strengthen muscles of the urogenital diaphragm. Strengthening which of the following muscles will most help the woman's incontinence? A. Gluteus minimus B. Levator ani C. Obturator internus D. Piriformis E. Pubococcygeus

E. Pubococcygeus Main Explanation The pubococcygeus most directly controls urine flow and is the muscle that contracts during orgasm. It surrounds the anus, the bladder opening, and, in women, the vagina. The pubococcygeus extends from the pubic bone to the coccyx.

A patient presents to your clinic with a complaint of visual difficulties. On physical exam, you notice that when the patient looks to the left, only his right eye moves. The rest of the exam was within normal limits. The nerve responsible for this patient's problem travels through which of the following structures? A. Internal auditory meatus B. Foramen ovale C. Foramen rotundum D. Optic canal E. Superior orbital fissure

E. Superior orbital fissure Main Explanation The patient in the question stem presents with lateral rectus palsy on the left side. The nerve responsible for this muscle is the abducens nerve (cranial nerve VI). Due to its long path, this cranial nerve is the most susceptible to injury. During its path from the brainstem to the extraocular muscles, the abducens passes through the superior orbital fissure. Other nerves that pass here include cranial nerves III, IV, and V1. Cranial nerve V2 passes through the foramen rotundum. Cranial nerve V3 passes through foramen ovale. The optic nerve, ophthalmic artery and central retinal vein pass through the optic canal. Cranial nerves VII and VIII pass through the internal auditory meatus.

A 2-year-old infant is brought to your office by his mother, who says she has been noticing copious amounts of blood in his stool for the past 2 days. The patient is tachycardic but has not been experiencing any pain. What embryonic structure is likely to be responsible for this patient's condition? A. Ductus Arteriosus B. Ductus Venosus C. Umbilical Artery D. Urachus E. Vitelline Duct

E. Vitelline Duct This patient likely has a lower GI bleed from a Meckel's Diverticulum. This true diverticulum is a remnant of the vitelline duct and often contains ectopic gastric mucosa which can cause bleeding and perforation. The bleeding is often painless. The ductus venosus is a shunt that bypasses the liver and carries blood from the umbilical vein directly to the IVC. Its remnant is the ligamentum venosum. The ductus arteriosus is a shunt that bypasses the lungs to carry blood from the pulmonary artery to the aortic arch. Its remnant is the ligamentum arteriosum. The urachus becomes the median umbilical ligament. The 2 umbilical arteries becomes the medial umbilical ligaments. The vitelline duct is a connection with the yolk stalk and bowel, but normally obliterates during week 7 of development.

Which of the following ligaments is the strongest? A. tibial collateral B. glenohumeral Ccalcaneofibular Dacromioclavicular Eposterior talotibial Filiofemoral

F. Iliofemoral The iliofemoral, together with the ischiofemoral and pubofemoral ligaments, make the hip joint one of the hardest joints to dislocate in the body. ## These ligaments are tightened during hip extension, which is why the hip is less likely to dislocate in extension but has ## more mobility while flexed. The glenohumeral ligament makes up part of the shoulder joint and is often torn during "shoulder dislocation" One of three ligaments on the lateral side of the ankle joint, the calcaneofibular ligament is susceptible to tear during ## hyperinversion of the foot. The other two ligaments include the anterior and posterior talofibular. The names of each ligament tell you which two bones are connected. The acromioclavicular (AC) ligament, connecting the acromion of the scapula to the clavicle, can be torn by blunt force to the shoulder. This results in "shoulder separation." High grade shoulder separations will also tear the stronger coracoclavicular (CC) ligament The posterior talotibial ligament makes up part of the deltoid ligament on the medial side of the ankle joint. Although stronger than the ligaments on the lateral side of the ankle, ## the deltoid is susceptible to tear during hyper-eversion of the foot. The other ligaments of the deltoid include the anterior talotibial and the calcaneotibial. The names of each ligament tell you which two bones are connected. iliofemoral The iliofemoral, together with the ischiofemoral and pubofemoral ligaments, make the hip joint one of the hardest joints to dislocate in the body. These ligaments are tightened during hip extension, which is why the hip is less likely to dislocate in extension but has more mobility while flexed.

Which muscle helps "unlock" the knee joint after hyperextension? A. pectineus B. plantaris C. piriformis D. pronator teres E. pisiform F. iliopsoas G. popliteus

G. popliteus Main Explanation The popliteus muscle helps "pop" the knee back in place by medially rotating the tibia on the fixed femur.

Three days after having a myocardial infarction, which took more than two hours to revascularize, a 62-year old Caucasian female suffers a mitral valve prolapse. Damage to which muscle most likely resulted in the prolapse? A. pectinate muscles B. cardiac muscle C. papillary muscles D. chordae tendinae

Located in the ventricles of the heart, the papillary muscles contract before systole in order to hold the atrioventricular valves open and prevent prolapse. There are five papillary muscles - one per valve cusp - that are connected to the cusps via chordae tendinae. Pectinate muscles are located in the atria and may contribute to increasing the force of atrial contraction. Damage to chordae tendinae ("heart strings") can lead to valve prolapse; however, these are not muscles and thus the question does not apply to them.

During development, sensory neurons reach the target muscle cells before motor neurons. True False

Main Explanation Sensory neurons are part of the second wave of nerve proliferation while motor neurons are part of the first wave of nerve proliferation. Motor neurons lead the way to the target site and a short while after sensory neurons follow the path used by motor neurons to the target site.

A 22-year-old intoxicated male presents with a painful headache following a bar fight. Head CT reveals a biconvex mass adjacent to a fractured right temporal bone. The artery implicated in the injury passes through the cranium through the same foramen as which of the following nerves? AMaxillary nerve BMeningeal branch of the mandibular nerve CMeningeal branch of the maxillary nerve DMiddle meningeal nerve ENervus intermedius

Main Explanation A biconvex (lens-shaped) mass is strongly indicative of an epidural hematoma, which most commonly results from injury to the middle meningeal artery secondary to temporal bone fracture. The middle meningeal artery enters the cranium through the foramen spinosum together with the meningeal branch of the mandibular nerve (B), which is also called nervus spinosum. The maxillary nerve (A), the V2 division of the trigeminal nerve, courses through the foramen rotundum, not the foramen spinosum. The meningeal branch of the maxillary nerve (C), also called the middle meningeal nerve (D), does not pass through a foramen in the skull. It branches directly off of V2 immediately after its origin from the trigeminal ganglion. The nervus intermedius (E) enters the internal auditory canal, not the foramen spinosum. Nervus intermedius should not be confused with nervus spinosum, which is another name for the meningeal branch of the mandibular nerve.

A 31-year-old G1P1 mother with a three-week-old infant presents to your office because she saw a report on SIDS on her local TV news channel. She tells you that her pregnancy was uncomplicated and she had a normal vaginal birth at a gestational age of 39 weeks. She asks you what steps she can take to help prevent SIDS. Which of the following have been shown to be effective measures to reduce the risk of SIDS? A. Use a home cardiorespiratory monitor to monitor infant B. None of the above C. Place infant in supine position for sleeping D. Place infant on their side for sleeping

Main Explanation Actor Robert Redford recently told the public that he lost a child to sudden infant death syndrome (SIDS) in 1959. SIDS is the top cause of mortality in infants between the ages of one month and one year in the US. However, no one really knows why SIDS occurs. It is thought that SIDS occurs in infants who have a genetic predisposition or brain abnormality. However, it is a diagnosis of exclusion that can only be made after an autopsy has been performed. It is not surprising that a new parent would be concerned about SIDS. One measure that has been shown to reduce the risk of SIDS is placing an infant in a supine (on the back) position for sleep. Side sleeping is no longer recommended. The use of home monitors to monitor the cardiac and respiratory status of the infant have not shown to have any benefit in reducing the incidence of SIDS and they are not recommended by the American Academy of Pediatrics (AAP).

The sacroiliac joint is a synovial joint True False

Main Explanation Although synovial joints are known for their mobility, the sacroiliac joint derives its stability from several strong ligaments crossing the joint (anterior and posterior sacroiliac, interosseus, iliolumbar, sacrotuberous, sacrospinous). Sacroiliitis, or inflammation of this joint, should be on the differential of a patient with unilateral lower back pain.

Which of the following is the first branch of the internal carotid artery distal to the cavernous sinus and provides collateral flow in the case of proximal carotid artery occlusion via an anastomosis with the maxillary artery? APosterior ethmoid artery BTransverse facial artery COpthalmic artery DAnterior ethmoid artery

Main Explanation As can be seen in the image below (cavernous sinus shown in purple), the opthalmic artery branches from the internal carotid just distal to the cavernous sinus. The dorsal nasal branch of the opthalmic artery forms an anastomosis with the external maxillary artery providing collateral blood flow. The posterior ethmoid artery is a branch of the opthalmic artery.

A child presents to the pediatric ER with acute onset of breathing problems after swallowing a nickel. Which bronchus is the foreign body most likely lodged in? A. right B. left C. inferior D. superior

Main Explanation Foreign bodies are usually lodged in the right main bronchus because it is wider and at a steeper angle than the left main bronchus. This is attributed to the fact that the right lung requires more air (three lobes and slightly larger) and does not have the left-sided heart diverting it at a larger angle (as happens to the left bronchus).

Which of the following muscles is not part of the rotator cuff? Asubscapularis Bsupraspinatus Cteres major Dinfraspinatus

Main Explanation Teres minor is the fourth muscle of the rotator cuff. The rotator cuff muscles may be remembered using the acronym SITS: supraspinatus, infraspinatus, teres minor, and subscapularis.

A 33-year-old woman undergoes abdominal surgery to correct a ureteral stricture of unknown origin. Anterior to the psoas at the level of the aortic bifurcation, the surgeon observes three tubular structures: gonadal artery, gonadal vein, and ureter. In the absence of anatomic variations, which description best identifies the ureter? AMost anterior structure at the level described; inferiorly it courses anterior to the iliac bifurcation. BMost anterior structure at the level described; inferiorly it courses posterior to the iliac bifurcation. CMost posterior structure at the level described; inferiorly it courses anterior to the iliac bifurcation. DMost posterior structure at the level described; inferiorly it courses posterior to the iliac bifurcation. ENeither most anterior nor most posterior structure at the level described; inferiorly it courses anterior to the iliac bifurcation.

Main Explanation At the level of the aortic bifurcation, the ureter typically runs posterior to the gonadal artery and vein. When crossing the pelvic brim at the level of the iliac bifurcation, the ureter courses anteriorly. On its way to the urinary bladder, the ureter is typically then posterior to the uterine artery (or vas deferens in men); this final relationship gives rise to the "water [urine] under the bridge" mnemonic.

Due to its _____ renal vein, the _____ kidney is generally taken during living donor transplantation. Alonger...right Bshorter...right Clonger...left Dshorter...left

Main Explanation Because the inferior vena cava is on the right side of the body, the left renal vein is generally longer than the right. Thus, the left kidney is often used as the donor organ.

Regarding collateral circulation of the shoulder, which two arteries allow blood to bypass the second part of the axillary artery by anastomosing with the subscapular and circumflex scapular arteries? AThoracoacromial, anterior circumflex humeral BSuprascapular, thoracoacromial CSuperior thoracic, lateral thoracic DSuprascapular, transverse cervical

Main Explanation Both the suprascapular and the transverse cervical artery come from the thyrocervical trunk of the subclavian. By anastomosing with the subscapular and circumflex scapular arteries (the circumflex scapular is a branch of the subscapular) which come from the 3rd part of the axillary artery, the middle portion of the axillary artery is bypassed.

Which of the following choices is a branch off of the posterior cord in the brachial plexus? Aulnar Baxillary Cmedian Dmusculocutaneous

Main Explanation Branches off the posterior cord include the superior and inferior subscapular nerves, the thoracodorsal nerve, the axillary nerve, and the radial nerve.

When determining the pupillary response it is important to note that ______ is responsible for the afferent pathway and _______ is responsible for the efferent pathway. Also, a blown pupil is significant for in jury on the ______ side. ACN III, CN II, contralateral BCN III, CN II, ipsilateral CCN II, CN III, ipsilateral DCN II, CN III, contralateral

Main Explanation CN II (optic nerve) is an afferent special sense nerve. CN III (oculomotor nerve) is an efferent somatic motor nerve.

Which of the following structures is most likely to be injured by a fracture of the posterior cranial fossa? A. Abducens nerve in cavernous sinus B. Facial nerve at internal acoustic meatus C. Maxillary nerve D. Occipital lobe of cerebral hemisphere E. Temporomandibular joint

Main Explanation Choice B (facial nerve at internal acoustic meatus) is correct. The internal acoustic meatus is a feature of the posterior cranial fossa. It transmits the facial nerve (CN VII) and the vestibulocochlear nerve (CN VIII). Choice A (abducens nerve in cavernous sinus) is incorrect because it is in the middle cranial fossa. Choice C (maxillary nerve) exits the foramen rotundum in the middle cranial fossa. Choice D (Occipital lobe) is unlikely to be injured. Choice E (Temporomandibular joint) is a joint between the temporal bone and mandibular and not part of the posterior cranial fossa

A male infant has a cleft lip on one side that does not involve the alveolar process or the hard palate. A unilateral cleft lip results from the failure of which two facial prominences to merge? ALateral nasal and maxillary BLeft and right medial nasal CMaxillary and mandibular DMedial nasal and maxillary ELateral nasal and Medial nasal

Main Explanation Choice D (medial nasal and maxillary) is correct. The upper lip is formed when the two medial nasal prominences merge with the two maxillary prominences. A unilateral cleft lip results from failure of the union of the medial nasal and maxillary prominences on one side. If the failure is complete, a cleft of the maxillary alveolar process (between the canine and lateral incisor teeth) and a left of the primary palate also are present. Most cleft lips occur in males, whereas cleft palate is more common in females. Choice A (lateral nasal and maxillary)fusion of these structures forms the lacrimal duct

What muscles provide the main kinetic input to gait? Ahamstrings Bplantarflexors Cdorsiflexors Dquadriceps

Main Explanation Contracting just prior to "Toe Off", the plantar flexor muscles provide the main kinetic input to gait. All other muscles mainly function to decelerate the lower limb and stabilize the lower limb and trunk. Plantar flexors include the peroneus longus and peroneus brevis.

A 24 year old Hispanic man is involved in a motorcycle accident and sustains severe trauma to his external genitals. The emergency department physician is concerned that the urethra may be damaged in the bulb of the penis. If this were the case urine will extravasate into which of the following structures? A. Anterior thigh B. Ischioanal fossa C. Peritoneal cavity D. Pudendal canal E. Superficial perineal space

Main Explanation Damage to the urethra in the bulb of penis could result in the extravasation of urine into the superficial perineal space. From there it could gain access to the scrotal sacs and the potential space between the superficial and deep fascias of the penis. Urine could extravasate into the anterior thigh (choice A) if urethral rupture occurred in the superficial peritoneal pouch. Urine could extravasate into the peritoneal cavity (choice C) if the ureter were damaged. Urine would not enter the ischioanal (choice B) or pudendal canal (choice D) during urethral rupture.

What factor is primarily necessary for the development of the cerebellum? A. BMP4 B. Noggin C. FGF-8 D. Reelin

Main Explanation FGF-8 is fibroblast growth factor. The cerebellum develops from the exuberant proliferation of neuroblasts in the first rhombomere, aka the rhombic lip. The midbrain-hindbrain barrier adjacent to the first rhombomere (remember that the hindbrain is divided into rhombomeres) secretes FGF-8, causing this development.

Recall that most cranial nerves originate in the pons and medulla. Genes from what family are differentially expressed in the rhombomeres that eventually become the pons and medulla, enabling the development of the cranial nerves? A. Bcl-2 B. Hox C. FGF D. MHB

Main Explanation Hox, or homeobox, genes are an important family of developmental genes. They are differentially expressed across rhombomeres, resulting in a unique pattern of Hox gene expression in each rhombomere, allowing specialization of cranial nerve nuclei (trigeminal, facial, etc).

What muscle(s) are involved in the "swing" phase of gait? Adorsiflexors and plantarflexors Bplantarflexors and iliopsoas muscle Cdorsiflexors Diliopsoas muscle Eplantarflexors Fdorsiflexors and iliopsoas muscle

Main Explanation In the "swing" phase of gait, dorsiflexors (tibialis anterior, extensor hallucis longus, extensor digitorum longus, and fibularis tertius) lift the foot to clear the ground, while the iliopsoas muscle flexes the hip, assisting in forward acceleration.

A 3-year-old boy presents with a painless bulge in his left side of scrotum that appears with coughing but is reduced when lying down. What is the most likely etiology of his condition? A. Direct inguinal hernia B. Passage of loops of bowel into the femoral canal C. Patent processus vaginalis D. Ventral hernia E. Weakness of the abdominal musculature

Main Explanation Indirect hernias are the most common type of hernias in young children. The testis originates as a primarily retroperitoneal structure and is "pulled" down into the scrotum by the gubernaculum. The processus vaginalis, the connection between the scrotum and the rest of the peritoneal cavity, is eventually obliterated. Failure of obliteration before birth results in the possibility of loops of bowel and or peritoneal fluid to enter into the scrotum. This is known as an indirect inguinal hernia, which is defined anatomically (thus, intraoperatively!) by the passage of the hernia sac lateral to the inferior epigastric vessels.

A 22-year-old man presents to his physician complaining of nasal congestion. Rhinoscopy demonstrates focal inflammation with mucosal edema in the inferior nasal meatus. Drainage from which of the following structures is most likely to be obstructed? AAnterior ethmoidal air cells BFrontonasal duct CMaxillary sinus DNasolacrimal duct EPosterior ethmoidal air cells

Main Explanation Nasolacrimal duct (Choice D) is correct. Tears drain from the conjunctival sac into the lacrimal sac, through the nasolacrimal duct into the inferior nasal meatus. Anterior ethmoidal air cells (Choice A), frontonasal duct (Choice B), and maxillary sinus (Choice C) all typically drain into the middle meatus. They should not be affected by obstruction of the inferior nasal meatus. Posterior ethmoidal air cells (Choice E) usually drain into the superior meatus. They should not be affected by obstruction of the inferior nasal meatus.

The adult kidney develops from the metanephros which has two sources: the ureteric bud and the metanephric mesoderm. If a problem in the development of the ureteric bud occurred, which of the following structures in the adult kidney would be directly affected? A. Collecting duct BConnecting tubule CDistal convoluted tubule DLoop of Henle EProximal convoluted tubule

Main Explanation Of the answer choices, only the collecting duct (choice A) develops from the ureteric bud. Other structures in the adult kidney that developed from the ureteric bud include the minor calyx, major calyx, renal pelvis, and ureter. The connecting tubule (choice B), loop of Henle (choice D), distal convoluted tubule (choice C), and proximal convoluted tubule (choice E) all developed from the metanephric mesoderm.

Parasympathetic innervation to the distal one-third of the descending colon is provided by the _________. Avagus nerve Blesser splanchnic nerve Cpelvic splanchnic nerve Dgreater splanchnic nerve

Main Explanation Parasympathetic innervation of the GI tract is provided by the vagus nerve up to the distal 1/3 of the colon. Near the left colic (splenic) flexure the pelvic splanchnic nerves take over parasympathetic innervation. The greater and lesser splanchnic nerves provide sympathetic innervation.

Which of the following is necessary for the inside-out patterning of the cerebral cortex (older neurons are deeper)? ABMP4 BNoggin CFollistatin DChordin EReelin

Main Explanation Reelin is responsible for inside-out patterning of the cerebral cortex. It is a protein that interacts with the extracellular matrix, permitting new neurons to migrate superficially past older neurons. BMP4 causes ectoderm to become skin. Noggin, follistatin, and chordin are anti-BMP4 factors that allow the default neural development to proceed.

Consider the anatomy of the human eye. Which structure refracts light the most? Avitreous humor Bcornea Canterior surface of the lens Dposterior surface of the lens

Main Explanation Refraction at the three principle surfaces: 1. cornea 2. anterior surface 3. posterior surface The greatest difference in refractive indices across eye structures is between the air and the cornea.

Which of the following is/are retroperitoneal? A kidney B transverse colon C stomach D aorta E ascending colon F two of the above G three of the above H all of the above

Main Explanation Retroperitoneal structures are GI structures that do not have a mesentery as well as non-GI structures. It's important to know which structures are retroperitoneal because injury to them can cause gas or blood accumulation in the retroperitoneal space. A great mnemonics is: SAD PUCKER Suprarenal (adrenal) glands Aorta and IVC Duodenum (2nd, 3rd, and 4th sections) Pancreas (not tail) Ureters Colon (ascending and descending) Kidneys Esophagus (lower 2/3) Rectum (upper 2/3)

Which of the following is a retroperitoneal structure? A. transverse colon B. sigmoid colon C. first part of the duodenum D. descending colon

Main Explanation Retroperitoneal structures including the descending colon are situated between the peritoneum and posterior abdominal wall and are largely immobile. Urinary structures (bladder, ureters, kidneys, suprarenal glands) and vessels (aorta and inferior vena cava) are all retroperitoneal. Some GI structures lose their mesenteric leashes and fuse to the posterior abdominal wall becoming secondarily retroperitoneal (ascending & descending colon, duodenum - 2nd, 3rd, & 4th parts, pancreas - head, neck, & body). Intraperitoneal structures maintain mesenteric leashes and are more mobile (stomach, liver, gall bladder, spleen, jejunum, ileum, transverse colon, and sigmoid colon). A great mnemonic for retroperitoneal structures is: SAD PUCKER. S - suprarenal glands (aka adrenal glands) A - aorta/IVC D - duodenum (parts 2-4) P - pancreas U - ureters C - colon (ascending and descending only) K - kidneys E - esophagus R - rectum

Which cranial nerve originates alongside the medulla and spinal cord and provides motor innervation to the trapezius muscle? A. Oculomotor (III) B. Spinal accessory nerve (XI) C. Olfactory (I) D. Abducens nerve (VI)

Main Explanation The Spinal Accessory nerve (CN XI) has the following features: Special Visceral Efferent: motor to sternomastoid & trapezius Originates alongside medulla & spinal cord.

A 17-year-old male falls on his wrist while playing basketball. After taking a history, you notice on physical exam that he has marked tenderness within the "anatomical snuff box." What is the likely diagnosis? AFracture of the hook of the hamate bone BFracture of the pisiform bone CFracture of the scaphoid bone DTendonitis EWrist sprain

Main Explanation The anatomical snuff box is the triangular space formed by the extensor pollicis longus (medial border), extensor pollicis brevis & abductor pollicis longus (lateral border), and the distal radial styloid. The trapezium and scaphoid bones form the floor or base of the snuff box. Tenderness in the anatomical snuffbox indicates scaphoid fracture until proven otherwise!

An interventional radiologist is performing a procedure in which real-time imaging of the enteric vessels is important. With the catheter, he enters at the femoral artery, traces back up through the aorta, and enters the celiac trunk. If he were to inject contrast at this point while recording a radiograph, which three vessels would he likely see? ALeft gastric artery, short gastric artery, hepatic artery BLeft gastric artery, splenic artery, cystic artery CLeft gastric artery, splenic artery, common hepatic artery DRight gastric artery, splenic artery, hepatic artery ESuperior mesenteric artery, splenic artery, hepatic artery

Main Explanation The branches of the celiac trunk are the left gastric artery, the splenic artery, and the common hepatic artery.

In the abdominal region, arteries supplying non-GI structures branch _____ and arteries supplying GI structures branch _____. Alaterally...posteriorly Banteriorly...laterally Claterally...anteriorly Dposteriorly...laterally

Main Explanation The celiac trunk, superior mesenteric artery, and inferior mesenteric artery supply the foregut, midgut, and hindgut respectively and branch anteriorly off of the abdominal aorta. In contrast, the inferior phrenic arteries (diaphragm), suprarenal arteries (adrenal), renal arteries (kidneys), and testicular/ovarian arteries branch laterally off of the abdominal aorta.

An angiographic study of the distal part of the circle of Willis requires access to the vertebral artery. Access to this artery can be obtained via the A. anterior triangle of the neck B. muscular triangle of the neck C. posterior triangle of the neck D. submental triangle E. suboccipital triangle

Main Explanation The correct answer is E. The suboccipital triangle lies in the neck at the base of the skull. The suboccipital triangle is bounded by the inferior oblique, rectus major, and superior oblique muscles. The vertebral artery can be found within the suboccipital triangle, lying on the posterior arch of the atlas, lateral to the midline, typically at about the level of the lower portion of the ear lobe. Care should be taken in accessing the vessel, since the first cervical nerve lies between the vertebral artery and the posterior arch of the atlas. The anterior triangle of the neck (choice A) is in the anterior neck, and is bounded by the neck midline, the mandible, and the sternocleidomastoid muscle. The anterior triangle of the neck is subdivided into the muscular, carotid, submandibular, and submental triangles. The small muscular triangle (choice B) lies between the superior belly of the omohyoid and the sternohyoid muscle. The posterior triangle of the neck (choice C) is on the side of the neck, and is bounded by the sternocleidomastoid muscle, trapezius, and the middle third of the clavicle. The submental triangle (choice D), also called the suprahyoid triangle, is found below the lower jaw, and is bounded by the hyoid bone and anterior bellies of the digastric muscles.

A 28-year-old G2P1 with gestational diabetes gives birth to a 4490 g baby boy at 40 weeks. The delivery was complicated by shoulder presentation, but the baby was delivered using the McRoberts maneuver and suprapubic pressure. On exam, the baby has a strong cry, but is found to have asymmetric arm movements. On further exam, the baby's left arm is adducted and internally rotated. Which of the following is the most likely diagnosis? A. Clavicular fracture B. Diaphragmatic paralysis C. Erb's palsy D. Humerus fracture E. Klumpke's palsy

Main Explanation The correct answer is Erb's Palsy. This is the most likely diagnosis given the above physical exam and risk factors, including maternal gestational diabetes and macrosomia. Erb's palsy is a C5 and C6 injury that accounts for the majority of obstetrical brachial plexus nerve palsies in newborns. ## The etiology of these nerve palsies may be iatrogenic lateral traction on the fetal head, usually during deliveries in which there is shoulder dystocia. Arm weakness involves the deltoid and infraspinatus muscles (mainly C5) and biceps (mainly C6). On physical exam, the upper arm is adducted and internally rotated with the forearm extended, but the hand and wrist are spared. Klumpke's palsy (C8-T1 nerve injury) is not correct since this is seen much less frequently and often presents with hand paralysis and ipsilateral Horner's syndrome. Clavicular fractures and humerus fractures are less common fetal complications of shoulder dystocia. Diaphragmatic paralysis would occur with injury to the phrenic nerve. However, this would present with signs and symptoms of respiratory distress including tachypnea, mild to severe respiratory distress, cyanosis, apnea, or a weak cry. Neonates with diaphragmatic paralysis may also have a brachial plexus paralysis, however given that this baby has no respiratory symptoms, this is a less likely diagnosis.

Which of the following factors causes ectoderm to become skin? ABMP4 BNoggin CFollistatin DChordin EReelin

Main Explanation The default fate of ectoderm is neural. BMP4 overrides this in favor of skin development. Noggin, follistatin, and chordin are anti-BMP4 factors that allow the default neural development to proceed. Reelin is responsible for inside-out patterning of the cerebral cortex.

The distal 1/3 of the transverse colon to the upper rectum is supplied by the _____ artery and innervated (parasympathetic) by the _____ nerve. A. inferior mesenteric....pelvic B. superior mesenteric...pelvic C. inferior mesenteric...vagus D. superior mesenteric...vagus

Main Explanation The distal 1/3 of the transverse colon to the upper portion of the rectum is derived from the hindgut and supplied by the inferior mesenteric artery and pelvic nerve from L3. The distal duodenum to the proximal 2/3 of the transverse colon is derived from the midgut and supplied by the superior mesenteric artery and vagus nerve from L1. The stomach to the proximal duodenum, liver, gallbladder, pancreas, and spleen are derived from the foregut and supplied by the celiac artery and vagus nerve from T12/L1.

After birth, the foramen ovale closes to become the fossa ovalis. True False

Main Explanation The foramen ovale shunts the fetal blood from the right atrium to the left atrium, thus bypassing the nonfunctional fetal lungs. The closing of the foramen ovale is due to the relatively high pressure in the left atrium (over the right atrium) forcing the septum primum to push against the septum secundum.

Which of the following is NOT a direct opening to the orbit? Asuperior orbital fissure Bforamen rotundum Coptic canal Dlacrimal puncta

Main Explanation The foramen rotundum serves as an exit for the maxillary nerve (V2), which then passes through the inferior orbital fissure to enter the orbit. The foramen rotundum, therefore, is not an opening directly to the orbit. The orbital openings can be seen in the image below: 1. Ethmoidal foramen 2. Optic canal 3. Superior orbital fissure 4. Lacrimal sac 5. Infraorbital groove 6. Inferior orbital fissure 7. Infraorbital foramen A. superior orbital fissure CNs III, IV, VI, and opthalmic nerve (V1) C. optic canal optic nerve, opthalmic artery D. lacrimal puncta lacrimal fluid is distributed with each blink and eventually drains through the lacrimal punta into the lacrimal canaliculae and ultimately to the lacrimal sac

A physician is performing a cranial nerve exam on a patient. While testing the gag reflex, it is noted that when the right side of the pharyngeal mucosa is touched, the patient's uvula deviates to the right. When the left side is touched, the Pt. does not gag. Which of the following is the most likely location of his lesion? A. Left glossopharyngeal n. and left vagus n. B. left glossopharyngeal n. only C. left vagus n. only D. right glossopharyngeal n. and right vagus n. E. right glossopharyngeal n. only

Main Explanation The gag reflex requires the glossopharyngeal n. for the sensory limb of the reflex (unilateral) and the vagus n. for the motor limb of the reflex (bilateral). A lesion of the left glossopharyngeal n. will denervate the sensory receptors on the left side of the pharynx. Thus when the left side is touched, the Pt. does not feel it and does not gag. The gag reflex requires the vagus n. for motor limb of the reflex. If the vagus n. is lesioned, the left side of the soft palate will not elevate during a gag and the uvula will deviate to the right. In this case, the Pt. only feels the touch on the right side and only elevates the right side of the palate. Thus there is a lesion of both the left glossopharyngeal n. and left vagus n. B. If the Pt. had a lesion of the left glossopharyngeal n. only, there would have been no gag when the left side is touched, but there would be a normal gag, without deviation of the uvula, when the either side was touched. C. If the Pt. had a lesion of the left X n. only, the Pt. would have deviation of the uvula to the right when a gag was elicited, but touching either side of the pharynx would elicit a gag. D. If the Pt. had a lesion of the right glossopharyngeal n. and right vagus n., touching the right side of the pharynx would not elicit a gag and touching the left side would elicit a gag with the uvula deviating to the left.

The ________ ligament contains the portal triad (hepatic portal vein, hepatic artery, and common bile duct). Ahepatoduodenal Bfalciform Cgastrocolic Dgastro-portal

Main Explanation The hepatoduodenal ligament is the remnant of the lesser omentum connecting the duodenum to the porta hepatis of the liver. Contents of this ligament include the portal triad in addition to lymphatic vessels and branches of the vagus nerve.

A 27-year-old man is brought to the emergency room after sustaining a knife wound in the back. His vital signs are within normal limits. On exam, you appreciate a 4 cm long laceration that runs parallel to the inferior medial border of the scapula, and is 2cm from the spinous process of T5. The laceration has visibly penetrated at least 1 cm into the muscle tissue. Which muscle is most likely affected? ADeltoid BInfraspinatus CLevator scapulae DRhomboid major ETriceps brachii

Main Explanation The insertion of the rhomboid major (D) is the medial border of the scapula (it arises from the spinous processes of T2 to T5, as well as the supraspinous ligament). The deltoid (A) originates at the spine of the scapula and goes laterally to insert on the humerus. The infraspinatus (B) originates at the posterior scapula and goes laterally to form part of the rotator cuff (remember: SITS). The levator scapulae (C) inserts at the superior medial border of the scapula and goes superiorly. The triceps brachii (E) originates at the lateral scapula and inserts on the humerus.

In the ER, you observe a physician frantically performing a therapeutic thoracentesis (also known as thoracocentesis) in order to decompress a pleural effusion, like the one seen in the chest X-ray below. What structure is the physician trying to avoid by placing the needle immediately above the 10th rib (at the mid-axillary line)? A Right atrium B Lung C Aorta D Neurovascular bundle

Main Explanation The intercostal vein, artery, and nerve run in the intercostal groove on the inferior surface of each rib in the precise orientation of vein-artery-nerve, from top to bottom. The needle during a thoracentesis is therefore positioned directly above the upper margin of the relevant rib in order to avoid these structures. Mnemonic: VAN.

A 25-year-old woman is undergoing a nephrectomy in order to donate her kidney to her older sister, who has renal failure. The surgeon accidentally cuts a vein draining into the inferior aspect of the renal vein on the side of the kidney which is to be removed. What is the most likely identity of this vein? ALeft ovarian vein BLeft suprarenal vein CRight ovarian vein DRight suprarenal vein ESplenic vein

Main Explanation The left ovarian vein (or testicular vein in men) enters the inferior aspect of the left renal vein. The left suprarenal vein (B) also enters the left renal vein, but at its superior aspect. The right ovarian (C) and right suprarenal (D) veins drain directly into the inferior vena cava. The splenic vein (E) joins with the superior mesenteric vein to form the portal vein. Of note, in kidney transplantation, the left kidney is usually preferred because the left renal vein is longer than the right renal vein (the left renal vein has to cross over the vertebral column to get to the inferior vena cava while the right does not).

A 22-year old male presents to your clinic with a characteristic winged scapula. Damage to which of the following nerves results in this anatomical problem? AC5/C6 roots of brachial plexus BVagus nerve CDistal ulnar nerve DLong thoracic nerve

Main Explanation The long thoracic nerve (C5-C7) innervates the serratus anterior muscle, which connects the scapula to the thoracic cage and is used for abducting above the horizontal position. This nerve is sometimes injured during a mastectomy.

Following a circus accident, a man is unable to abduct his left arm from a 90 degree position to 180 degrees. Impairment of which of the following nerves could explain this finding? AAxillary nerve BLong thoracic nerve CMusculocutaneous nerve DRadial nerve EThoracodorsal nerve

Main Explanation The long thoracic nerve innervates the serratus anterior muscle, which- among its other functions- upwardly rotates the scapula allowing the arms to reach a 180 degree position. The thoracodorsal nerve innervates the latissimus dorsi, which has no function in arm abduction. The axillary nerve innervates the deltoid, which abducts the arm to 90 degrees. The radial nerve innervates the posterior muscles of the arm and forearm, which are not involved in arm abduction. The musculocutaneous nerve innervates muscles of the anterior arm, which are not involved in arm abduction.

A 19-year-old construction worker sustains a superficial laceration of the anterior wrist just proximal to the thenar and hypothenar eminences. Sensation is intact. Which of these tendons has most likely been severed? A. Extensor carpi ulnaris B. Flexor digitorum profundus C. Flexor digitorum superficialis D. Flexor pollicis longus E. Palmaris longus

Main Explanation The most superficial of the above tendons is the palmaris longus (E). The extensor carpi ulnaris (A) is not on the anterior wrist. The flexor digitorum profundus (B), flexor digitorum superficialis (C), and flexor pollicis longus (D) tendons are all in the carpal tunnel, and are thus covered by the flexor retinaculum, whereas the palmaris longus is not.

The obturator artery is a branch of the external iliac artery. True False

Main Explanation The obturator artery is a branch of the internal iliac artery, along with the superior and inferior gluteal arteries. The external iliac artery becomes the femoral artery once it passes beneath the inguinal ligament.

Which of the following vessels provides the majority of the blood supply to the liver? Ahepatic arteries Bsuperior mesenteric artery Chepatic portal veins Dsuperior mesenteric vein

Main Explanation The primary blood supply to the liver comes from the hepatic portal veins with important contributions from the hepatic arteries. The portal vein drains the GI tract and spleen, and supplies the liver with a large volume of poorly oxygenated blood. The hepatic arteries, derived from the celiac trunk, make a small but richly oxygenated contribution.

A 25 year old man comes to the emergency room complaining of acute onset of fever and testicular pain. He also noted that his scrotum had begun to swell and had a moderate amount of erythema. On physical exam, he is found to be febrile to 40 degrees Celsius and has significant bilateral swelling of the scrotum and bilateral testicular tenderness on palpation. Lab values were significant for leukopenia with relative lymphocytosis and a slightly elevated amylase. A high degree of suspicion for mumps prompted antibody testing. The patient was found to be IgM positive for the mumps antibody. What is the primary lymphatic drainage of the testes? ACommon iliac nodes BExternal iliac nodes CInguinal nodes DInternal iliac nodes EPara-aortic nodes

Main Explanation The primary lymphatic drainage for the testes and ovaries are the para-aortic lymph nodes (choice E) located in the lumbar region of the abdominal aorta. The para-aortic lymph nodes are sometimes referred to as the retroperitoneal lymph nodes. External iliac lymph nodes (choice B) drain external genitalia, vagina, and cervix. Internal iliac lymph nodes (choice D) drain the cervix, prostate, and rectum. The common iliac lymph nodes (choice A) receive afferents from both external and internal iliac groups. Inguinal lymph nodes (choice C) drains the lower part of the anal canal as well as part of the external genitalia.

The wave of depolarization in the cardiac conduction pathway begins at the _________. A. atrioventricular (AV) node B. Purkinje fibers C. coronary sinus D. sinoatrial (SA) node

Main Explanation The sinoatrial node located in the right atrium near the opening for the superior vena cava initiates depolarization in the conduction system. The wave passes on to the atrioventricular node located near the coronary sinus. The signal moves through right and left bundle branches to purkinje fibers within the ventricular walls before stimulating myocardium.

At which vertebral level(s) does the solid spinal cord terminate into the conus medullaris? AT12 BL3-L4 CS1 DL1-L2

Main Explanation The spinal cord is a solid structure until L1-L2. The inferior-most portion is termed the "cauda equina," literally horse's tail.

The posterior compartment of the leg is innervated by the: Adeep fibular nerve Bsuperficial fibular nerve Cfemoral nerve Dtibial nerve Eobturator nerve

Main Explanation The tibial nerve runs straight down through the popliteal fossa and into the posterior compartment of the leg. The common fibular nerve courses along the lateral aspect of the popliteal fossa, dividing into the superficial and deep fibular nerves to innervate the lateral and anterior compartments, respectively.

Activities such as playing an instrument only expand the cortex on the same side of the brain as the hand that is used. True False

Main Explanation These activities predominantly expand the cortex on the opposite side of the brain as the hand that is used. This is because motor innervation is contralateral; e.g. the right hand is controlled by the left hemisphere's motor cortex.

A 5-year-old boy is brought in by his mother because she is concerned that he might have a mass in his lower abdomen. She says it is usually noticeable, but sometimes completely goes away. On exam, the boy's intestines are palpated protruding through the internal inguinal ring. The protrusion increases with maneuvers that increase intra-abdominal pressure, but is reducible. In surgery, which of the following findings would confirm the likely diagnosis? AHernia sac following the path of the inferior epigastric artery BHernia sac inferior to the origin of inferior epigastric artery CHernia sac lateral to the inferior epigastric artery DHernia sac medial to the inferior epigastric artery EHernia sac posterior (deep) to the inferior epigastric artery

Main Explanation This boy has an indirect inguinal hernia. It is caused by the failure of closure of the processus vaginalis (i.e. a 'patent' processus vaginalis), which allows intra-abdominal contents to enter the inguinal canal. Direct inguinal hernias occur in older patients, and are characterized by a bulge medial to the inferior epigastric artery.

A patient has difficulty climbing stairs and his trunk lurches backward during the heel strike phase of walking. What nerve is most likely injured? Acommon fibular nerve Binferior gluteal nerve Csuperior gluteal nerve Dtibial nerve

Main Explanation When climbing stairs, gluteus maximus is engaged as a strong hip extensor. In addition, gluteus maximus acts with the hamstrings during heel strike to decelerate the limb. In its absence, lurching backward of the trunk occurs.

A 70-year-old man presents to his physician with numbness and tingling in both of his hands. He reports that this has been going on for "a long time" and mentions that he sometimes has aching in his wrists and forearms after playing the guitar for a long time. His symptoms are especially noticeable at night and frequently wake him up. An advanced version of this syndrome is represented in the image below. What is the cause of this condition? A. Entrapment of a nerve originating from the medial cord of the brachial plexus B. Entrapment of a nerve originating from the medial and lateral cords of the brachial plexus C. Entrapment of a nerve originating from the posterior cord of the brachial plexus D. Entrapment of a nerve originating from the lateral cord of the brachial plexus

Main Explanation This patient has carpal tunnel syndrome (CTS), a neuropathy caused by compression of the median nerve in the carpal tunnel of the wrist. Typical symptoms include numbness and tingling mainly in the thumb and radial fingers, aching and pain in the anterior wrist and forearm, and clumsiness in the hand. History and physical exam can help exclude other diagnoses but the most sensitive and specific test is electromyography (EMG). This test can help confirm and localize damage to the median nerve in the carpal tunnel, and can determine the severity of damage to the nerve which helps guide management. Treatment options range from wrist splinting to surgical release, depending on severity of the condition. The patient in the question stem is country music singer Wille Nelson. In 2004 at the age of 70, he had surgery for bilateral carpal tunnel syndrome as he had damaged his wrists by continuously playing the guitar for over six decades. This caused him to cancel several scheduled concerts and he was only able to write songs during his recovery.

A 15 year-old boy presents to your office complaining of a painful mass on the right side of his neck for one week. Last week he had a sore throat and productive, non-bloody cough that has since gone away. He has noticed that the mass usually becomes painful whenever he is sick with a sore throat, but it is never completely gone. He appears anxious because he cannot remember the last time the mass was not present. On physical exam, the mass is immobile and slightly painful to touch and his oropharynx exam is clear. What is the likely etiology of this patient's mass? A. Bacterial abscess B. Ectopic thyroid tissue C. Incomplete involution of branchial cleft one D. Incomplete involution of branchial cleft three E. Neoplasm

Main Explanation This patient's complaint is likely due to a branchial cleft cyst, due to an incomplete involution of branchial clefts two, three or four during the 7th week of embryonic development. Because they are lined with ectoderm, incomplete involution leaves behind an entrapped epithelium-lined cyst that may persist into adulthood, existing as a painless lateral neck mass only painful during infection. Answer choice A, bacterial abscess, would present with a more dire physical exam, perhaps draining pus, and a patient with febrile illness. Answer choice B, ectopic thyroid tissue, may be found at the base of the tongue or as part of a thyroglossal duct cyst, both of which are ruled out by normal physical exam. Incomplete involution of branchial cleft one, answer choice C, would lead to a disruption in the external auditory meatus, the normal derivative of cleft one, but would not result in a cyst. Neoplasm of the lymph nodes, answer choice E, is unlikely given the chronic nature of the cyst and the lack of other symptoms of lymphoma. Branchial cleft cysts can be identified through fistulography.

A 40-year-old, diabetic female patient comes to see you at your clinic. She has recently taken a new job working as the personal assistant of a high-level executive. Her job requires a lot of computer work, and she frequently works overtime. She complains that she has noticed tingling in both hands that is worse on the left. When you ask her to describe the exact location, she indicates that the first three digits are number than the fourth and fifth digits. Irritation of which nerve is the most likely cause of her symptoms? AAxillary nerve BMedian nerve CMusculocutaneous nerve DRadial nerve EUlnar nerve

Main Explanation This patient's symptoms are a classic presentation for carpal tunnel syndrome, in which the median nerve is compressed within the carpal tunnel. This syndrome is frequently caused by overuse, as in this case, with the patient's excess computer use. The median nerve innervates the lateral three and a half digits on each hand, which explains the numbness in digits 1-3 in her hands. The ulnar nerve innervates the medial digit and a half of the hand, but this patient reported that her digits 4-5 were not numb. The radial nerve innervates the back of the hand, but not the muscles within the hand. The other nerves do not innervate the hand.

A 6 year old child is brought into your clinic for evaluation of right hand weakness. The mother is unsure of the onset of the weakness, but has been noticing that her child rarely uses his right hand and that the right arm looks unusually limp. Physical exam reveals atrophy of both the thenar and hypothenar eminences, atrophy of the interosseous muscles, and sensory deficits on the medial side of the forearm and hand. Which of the following is the most likely location of the pathologic finding in this patient? ACarpal tunnel BMedial epicondyle CShaft of humerus DSupracondyle of humerus ECostoclavicular space

Main Explanation Thoracic outlet syndrome (TOS) is most likely to explain all the neurologic findings in this patient. TOS can be present as a congenital anomaly of the costoclavicular space (choice E) which is bordered by the clavicle, first rib, and the superior margin of the scapula. The subclavian vessels and the lower trunk of the brachial plexus (C8, T1) pass through this space and can be compressed by anatomic anomalies such as congenital bands, supernumerary ribs, cervical ribs, or laxity of the costoclavicular joint. An additional finding may include the disappearance of the radial pulse when the patient turns his head to the opposite side. The carpal tunnel (choice A) and the supracondyle of the humerus (choice D) are common sites of injury to the median nerve. Median nerve damage does not explain hypothenar atrophy, interosseous atrophy, or numbness to the medial side of the forearm and hand, all of which are signs of ulnar nerve involvement. Therefore, the location of pathology is more proximal. The medial epicondyle (choice B) is a common site of injury to the ulnar nerve, which may explain most of the neurologic findings except for thenar atrophy which suggests median nerve involvement. Therefore, the location of pathology is more proximal. The shaft of the humerus (choice C) is a common site of injury to the radial nerve which is not implicated in this scenario.

During embryonic development, the heart is initially more cranial than the head itself. True False

Main Explanation Though counterintuitive, the developing heart begins cranial to the head itself.

How many cervical spinal nerves are there? A8 B6 C5 D7

Main Explanation Though there are 7 cervical vertebrae, there are 8 cervical spinal nerves. The first 7 cervical spinal nerves emerge above their corresponding vertebrae. The last cervical spinal nerve (C8) emerges below the C7 vertebra, above T1. A good mnemonic for spinal vertebrae is 7-12-5 (cervical-thoracic-lumbar), or about what time one eats breakfast (7 am), lunch (12 pm), and dinner (5 pm).

Which cranial nerve receives inputs from chemoreceptors in the aortic body? A. Vagus nerve (X) B. Glossopharyngeal nerve (IX) C. Facial nerve (VII) D. Trigeminal nerve (V)

The Vagus nerve (CN X) has the following features: - Special visceral efferent: motor of pharynx, tongue - General visceral efferent: motor smooth muscles of pharynx, & abdominal viscera - Visceral afferent: stretch receptors in larynx, trachea, aortic arch, chemoreceptors in aortic body - General somatic afferent: sensation behind the ear, external auditory meatus, posterior pharynx - Nucleus in the medulla.

During development, which of the following structures marks the future placement of the inguinal canal? AInferior Epigastric Artery BGubernaculum CTransversus DUrachus

The future placement of the inguinal canal is marked in development by the gubernaculum, which in males is attached to the testis and passes from the testis into the inner wall of the scrotum by way of the anterior abdominal wall. A pocket or bubble of peritoneum called the processus vaginalis follows the gubernaculum protruding through the anterior abdominal wall to form the inguinal canal.

Which of the following cranial nerves is a special somatic afferent that mediates vision? AVI (Abducens nerve) BV1 (Ophthalmic nerve) CIII (Oculomotor nerve) DII (Optic nerve)

The second cranial nerve (Optic nerve) crosses in the optic chiasm and projects to the occipital cortex.

While playing squash, a young woman tore one of her right rotator cuff muscles. Which of the following is most likely to have been injured? A. Infraspinatus B. Subscapularis C. Supraspinatus D. Teres major E. Teres minor

The supraspinatus is the most commonly injured rotator cuff muscle. The infraspinatus, teres minor, and subscapularis are the other rotator cuff muscles; they are torn less frequently. The teres major is not part of the rotator cuff. The supraspinatus muscle initiates abduction. The infraspinatus muscle externally rotates the arm. Teres minor adducts and externally rotates the arm, and subscapularis muscle internally rotates and adducts the arm. A common mnemonic is SITS : from counter clockwise to clockwise around glemoral humerus: Supraspinatus (inferior to coracoid and acromion), infraspinatus, teres minor, subscapularis (anterior and inferior to supraspinatus)