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The Structural Basis of Medical Practice (SBMP) - Human Gross Anatomy, Radiology, and Embryology

The College of Medicine at The Pennsylvania State University

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Answer Guide To Essay Questions - First Anatomy Exam - 08/29/97

Note: This is an outline of items to discuss -- NOT the "Answer"

[ Structural Basis of Medical Practice ]

Part III. Answer in the space provided. (52 pts)
  1. Serving as a resident in emergency medicine a patient is admitted with an aortic aneurysm that appears to impact on the left vagus nerve. Discuss the course of the left vagus nerves in the thorax, and mention how perturbation of this nerve might be manifested in clinical symptoms. (8 pts)
    1. The left vagus nerve enters the superior aperture of the thoracic cavity with the left common carotid artery.
    2. Within the superior mediastinum the nerve crosses lateral to the arch of the aorta near the level of the ligamentum arteriosum.
      1. The left recurrent laryngeal nerve branches at this level and circles the aorta immediately posterior to the ligamentum arteriosum. It then ascends along a groove between the trachea and the esophagus.
      2. Cardiac branches leave the vagus to contribute to the superficial and deep cardiac plexuses and pulmonary plexuses.
    3. Inferior to the arch of the aorta, the left vagus courses inferiorly and posteriorly and passes posterior to the root of the lung.
    4. Upon reaching the esophagus the vagus nerve ramifies and contributes to the esophageal plexus of nerve fibers.
      1. Near the diaphragm the majority of fibers from the left vagus nerve converge to form the anterior vagal trunk. This trunk passes through the esophageal hiatus to enter the abdomen.
  2. Discuss the lines of gravity as it relates to the lower extremity, and the anatomy of relaxed standing. Include consideration of the stabilizing influences upon the hip, knee and ankle joints, with particular reference to ligaments and muscles. (12 pts)
    1. At the hip
      1. bones and articulations - ball and socket joint having synovial cavity
        1. head of femur (ball) fits into the acetabulum (socket)
        2. depth of socket is increased by acetabular labrum
        3. transverse acetabular ligament
      2. ligaments - from ilium, pubis, ischium
        1. pubofemoral - resists abduction
        2. iliofemoral - resists hyperextension
        3. ischiofemoral - resists hyperextension (flexion also)
        4. ligament of head of femur - function is uncertain, may resist adduction
        5. All ligaments stabilize the hip joint by securing the head of the femur in acetabulum
        6. Because of fiber spiral the joint is most stable in extension
      3. movements and muscle stabilization (emphasis on flexion and extension)
        1. flexion
          1. psoas major - lumbar plexus
          2. anterior compartment of thigh - femoral nerve
            1. rectus femoris - long head
            2. sartorius (lateral rotation)
            3. tensor fascia lata
          3. limited by trunk and hamstrings
        2. extension
          1. posterior compartment of thigh (hamstrings) - tibial portion of sciatic
          2. gluteus maximus - inferior gluteal nerve
          3. limited by ligaments of joint capsule (see above)
        3. adduction
          1. medial compartment of thigh and obturator externus - obturator nerve
          2. limited by opposite thigh and ligament to the head of the femur
        4. abduction
          1. gluteus minimus and medius and tensor facia lata - superior gluteal nerve
          2. limited by pubofemoral ligament and adductors
        5. lateral rotation
          1. short rotators of gluteal region - lumbosacral plexus
          2. long head of the biceps - tibial portion of sciatic
          3. sartorius - femoral nerve
          4. relatively free - limited by neck of femur and pubofemoral ligament
        6. medial rotation
          1. anterior part of gluteus minimus (medius) - superior gluteal nerve
          2. gracilis - obturator
          3. semitendonosus and semimembranosus - tibial portion sciatic
          4. limited by joint capsule
    2. At the knee
      1. Bones and Articulations (2 pts)
        1. Synovial hinge joint between the femoral and tibial condyles.
        2. Tibial plateau is cupped by the medial and lateral menisci.
        3. Patella articulates anteriorly as a sesamoid bone in the quadriceps tendon.
      2. ligaments (3 pts)
        1. Medial collateral ligament (attached to medial meniscus).
          1. medial femoral epicondyle to the medial tibial condyle.
          2. resists abduction of tibia.
        2. Lateral collateral ligament (interval between lateral meniscus and ligament transmits popliteus m.
          1. From lateral femoral epicondyle to the head of the fibula
          2. resists adduction of tibia.
        3. Anterior cruciate ligament
          1. from lateral posterior femoral condyle to anterior aspect of tibial intercondyler eminence.
          2. resists forward displacement of the tibia.
        4. Posterior cruciate ligament.
          1. from posterior medial femoral condyle to posterior aspect of tibial intercondyler eminence.
          2. resists posterior displacement of tibia.
        5. Oblique popliteal and arcuate ligaments strengthen the posterior joint capsule.
        6. coronary, transverse genicular, and meniscofemoral ligaments secure the menisci.
        7. because of reflections of the synovial membrane alone the intercondylar fossa of the femur the cruciate ligaments are extrasynovial.
      3. Movements and limitations of movement
        1. Primarily flexion and extension (hinge joint).
        2. Some rotation (30-40 degrees) is possible when the knee is flexed.
        3. Flexion is primarily by the hamstrings, short head of biceps, gracilis, and sartorius.
          1. innervated by tibial portion sciatic, peroneal portion sciatic, obturator, and femoral nerves respectively.
          2. minor flexion by popliteus, gastrocnemius, and plantaris.
          3. flexion is limited by quadriceps, cruciate ligaments, and by opposing soft tissues (calf and thigh).
        4. Extension is primarily by the quadriceps and tensor fascia lata.
          1. innervation by femoral nerve and superior gluteal nerve.
          2. extension is limited by hamstrings, cruciate ligaments, collateral ligaments, posterior joint capsule.
        5. Medial rotation of tibia is primarily by popliteus, semitendonosus, gracilis, and sartorius.
          1. innervation by tibial nerve, tibial portion sciatic, obturator, and femoral nerves respectively.
          2. limitation of movement by collateral ligaments
        6. Lateral rotation of tibia is primarily by biceps femoris.
          1. innervation by tibial and peroneal portions of sciatic nerve.
          2. limitation of movements by collateral ligaments.
        7. Abduction and adduction is limited by the medial and lateral collateral ligaments.
        8. "Screw Home"
          1. Consider when the knee is extended with the foot planted on the ground. In this case, the tibia is fixed by virtue of the planted foot. Thus, rotation of the knee occurs as movement of the femur. The femur rotates medially as the knee "locks" in extension. Notice that the lateral femoral condyle is smaller than the medial femoral condyle. As the knee is extended the smaller condyle moves through its arc before the medial condyle. Thus, movement stops at the lateral condyle while the femoral medial condyle continues to move further posteriorly. This movement results in a medial rotation of the femur. This medial rotation puts a torsion on the joint capsule and its ligamentus specializations (medial and later collateral ligs). The "twisting" of the capsular ligaments causes the region to tighten. This firmly approximates the femoral condyles to the tibial plateau and "locks" the knee. The femur "screws" medially onto the tibial plateau due to the larger medial condyle and the twisting of the capsular ligaments.
      4. Innervation (much of this was optional)
        1. small branches of the femoral, obturator, and sciatic, and tibial nerves pierce the joint capsule.
    3. At the ankle
      1. Bones and Movements - tibiotalar joint (hinge) and subtalar joint (talocalcalcaneo portion)
        1. Medial malleoulus of tibia - prevents lateral and rotational movement of talus
        2. Talus - trochlea fits between medial and lateral malleoli
        3. calcaneous - inferior to and supports much of the talus
          1. sustentaculum tali - provides grove for flexor hallucis longus
      2. ligaments and flexor retinaculum
        1. Deltoid ligament - fans out from the medial malleolus to the navicular, talus, and calcaneous
          1. secures the trochlea of the talus in its lateral relation to the medial malleolus
            1. restricts lateral and rotational movements - ankle is hinge joint
          2. exceptional strong - sprains of the medial ankle are uncommon
        2. Lateral ligaments
          1. weaker than deltoid
      3. Unlike the hip and knee, resistance to gravitational forces are by the triceps surae
        1. Hip and knee extension are maintained mostly by ligaments with little muscular activity
        2. line of gravity leads to dorsiflexon (extension)
  3. A 40-year old female complains of being constantly tired. You suspect problems involving the pericardium. Discuss the anatomy of the pericardial sac. including mention of the layers, relationships, stabilization, vascularization, innervation, and lymphatic drainage. Comment on the clinical ramifications of excessive fluid in the pericardial cavity. (10 pts)
    1. The pericardial cavity is separated from the left pleural cavity by the middle mediastinal wall. An infection beginning in the pericardial sac would erode several fascial barriers before entering the pleural cavity.
      1. fibrous layer of pericardium
      2. serous layer of pericardium
      3. pericardial sac
      4. epicardium
    2. Relations and Support
      1. anterior - pericardiacophrenic ligament and sternum (internal thoracic vessels)
      2. posterior - posterior mediastinum and contents (esophagus, aorta, etc.)
        1. support by venous mesocardium
      3. superior - superior mediastinum and contents (great vessels, thymus)
        1. support by arterial mesocardium
      4. inferior - Diaphragm
        1. support by central tendon of diaphragm
      5. lateral left - left pleural cavity and lung
        1. sternocostal recess
      6. lateral right - right pleural cavity and lung
        1. sternocostal recess
    3. Contents of the mediastinal wall are within endothoracic fascia
      1. phrenic n.
        1. damage could lead to movement deficits at the diaphragm (hic ups)
        2. because the phrenic n, is somatic and carries afferent pain fibers, sever pain is likely
      2. pericardiacophrenic a.v.
        1. damage could disrupt blood supply to the pericardium and cause fibrosis
    4. Blood supply
      1. fibrous pericardium
        1. pericardiacophrenic a.
        2. bronchial and esophageal arteries of aorta
        3. branches of internal thoracic a. and musculophrenic a.
      2. visceral pericardium
        1. coronary arteries to the visceral pericardium
    5. Lymphatic Drainage
      1. mediastinal nodes - bronchopulmonary nodes - paratrachial nodes - bronchomedistinal lymph truncks
      2. right - right lymph duct into brachiocephalic v.
      3. left - thoracid duct or independently into left brachiocephalic v.
    6. innervation
      1. phrenic n. - somatic innervation to fibrous pericardium
      2. intercostal nerves - somatic innervation
      3. superficial and deep cardiac plexus - visceral innervation to visceral pericardium
        1. vagal and sympathetic contributions
  4. As part of your responsibilities as a resident in pulmonary medicine, you are asked to give a consise report on the mechanisms of breathing. Discuss the mechanics of breathing. Include a discussion of joints, rib movements, innervation, and vasculature, and mention how a pneumothorax will alter these mechanics. (10 pts)
    1. Anterior posterior - pump handle and costotransverse joint
      1. cupped tubercle of transverse process results in pump handle of upper ribs
      2. costochondral and sternochondral joints involved
      3. The pump-handle movement of respiration refers to the movements of the upper 6 ribs during breathing. During inspiration there is an increase in the anterior-posterior diameter of the thorax. The sternum moves superiorly and anteriorly in accord with rib movements occurring at the costovertebral, costotransverse, costochondral, and sternochondral joints. Relative to the lower ribs, the costotransverse joint articulation at the transverse process is cupped and accommodates the tubercle of the rib. This articulation permits the rib to rotate on a transverse axis. A slight downward movement at the head of the rib is amplified distally at the sternum. This movement is transferred to the sternum by the costochondral and sternochondral joints. The result is that the sternum raises on inspiration much like the raising of a pump-handle when drawing water from the depths of a well
    2. transverse - bucket handle and costotransverse joint
      1. planar tubercle of transverse process results in bucket handle of lower ribs
      2. costochondral and sternochondral joints involved
    3. vertical - diaphragmatic
      1. phrenic n., pericardiacophrenic vessels, ant. post. intercostal vessels
    4. capillary effect, negative pressure, etc.
      1. pneumothorax - air enters and breaks capillary effect, loss of negative pressure, the lung collapses
  5. A 75-year old female patient complains of problems with walking. You suspect involvement of vessels in the adductor canal. Discuss the contents, boundaries (i.e., superior, inferior, medial, lateral, anterior, posterior), and the relations with respect to the adductor canal. (6 pts)
    1. At the apex of the femoral triangle is the beginning of the adductor canal.
      1. The femoral artery and vein, and the saphenous nerve enter the adductor canal.
    2. The adductor canal is bounded anteromedially by the sartorius muscle. Anterolaterally, it is bounded by the vastus medialis. Posteriorly it is bounded by adductor longus and adductor magnus.
    3. The adductor canal ends inferiorly at the adductor hiatus.
      1. There is an inferior free edge of the adductor magnus insertion on the femur.
      2. Posterior fibers of adductor magnus pass inferior to this free edge and insert on the adductor tubercle of the medial femoral epicondyle.
      3. The adductor hiatus is at this gap in the tendenous insertions of the adductor magnus muscle.
    4. Passing through the adductor hiatus are the femoral artery and vein as they leave the anterior compartment of the thigh to arrive in the popliteal fossa.
    5. The saphenous nerve courses through the adductor canal and occupies the adductor hiatus for part of its course.
      1. The saphenous nerve does not pass posteriorly through the adductor hiatus, but instead, passes anteriorly and inferiorly toward the pes anserinus.
  6. A 37-year old chef complains of problems when standing for long periods of time. Indicate your knowledge of the lateral longitudinal arch (muscles, ligaments, bones, vessels) as you consider a strategy for treatment. (6 pts)
    1. The lateral longitudinal arch is much lower than the medial arch and consists of the calcaneus, cuboid, and last two metatarsals. The long and short plantar ligaments are particularly important structures adding support. The peroneus longus, brevis, and tertius muscles additionally support the longitudinal arch. The intrinsic flexors, plantar aponeurosis, and skin provide additional support. The arches permit blood flow and neural activity to occur on the plantar aspect of the foot by preventing compression of these vessels and nerves. With proper exercise, the muscular contribution to arch support can provide relief. Strengthening of the intrinsic and extrinsic flexors together with strengthening the muscles of the lateral and anterior compartments would enhance support of the lateral longitudinal arch.

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Loren A. Evey, Ph.D.