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Written Examination Part IV. (36 pts) - Essay: Lower Limb and Thorax (August 30, 2007)

Note: This is an answer guide. An outline of topics to discuss. It is not "the answer."

Popliteal Fossa - August 30, 2007

Discuss the anatomy of the popliteal fossa, and include an account the boundaries, structures entering and leaving at each boundary, vascular supply, innervation, ligaments, bones, contents, lymphatics, muscles, and relationships. (12 pts)

General comments

  • Posterior to knee, diamond shaped, fat filled, passage of key structures to the lower limb

Boundaries, bones, ligaments, crossing structures, vasculature

  • Superior boundary - apex of diamond formed by semimembranosus and semitendinosus diverging from biceps femoris
    • sciatic n. - enters from posterior thigh deep to hamstrings, divides into tibial (medial) and common peroneal (lateral) nn.
  • Superior lateral boundary - biceps femoris
    • superior lateral genicular a.v. - leaves popliteal fossa femur at lateral femoral epicondyle superior to origin of gastrocnemius and deep to biceps femoris
  • Superior medial boundary - semitendinosus and semimembranosus
    • superior medial genicular a.v. - leaves popliteal fossa at medial femoral epicondyle superior to adductor tubercle and deep to semimembranosus
  • Inferior lateral boundary - lateral head of gastrocnemius
    • inferior lateral genicular a.v. - leaves popliteal fossa crossing posterior surface of popliteus fascia and arcuate ligament, deep to head of gastrocnemius
    • common peroneal n. - leaves popliteal posterior to lateral head gastrocnemius and lateral to neck of fibula
  • Inferior medial boundary - medial head of gastrocnemius
    • inferior medial genicular a.v. - leaves popliteal fossa posterior surface of tibia near the plateau, deep to head of gastrocnemius
  • Inferior boundary - apex of diamond formed by convergence of the two heads of gastrocnemius
    • posterior tibial a.v. - leaves popliteal fossa deep to the heads of origin of soleus
    • sural aa. - leaves popliteal fossa by entering the bellies of gastrocnemius
    • branches of tibial n. to the gastrocnemius
  • Posterior boundary - popliteal fascia (deep fascia), tranisition from fascia lata to crural fascia
    • medial and lateral sural nn. - branches for tibial and common peroneal nn.
    • short saphenous v. - pierces popliteal fascia to enter the popliteal v.
  • Anterior boundary - femur, tibial plateau, joint capsule, oblique popliteal lig., arcuate lig., popliteus m.
    • popliteal a.v. - enter through adductor hiatus (superior medial anterior in the fossa) as continuation of the femoral vessels; artery deep to vein.
    • middle genicular a. leaves popliteal fossa through the posterior aspect of the joint capsule


  • branches of the sciatic, tibial, and common peroneal provide sensory innervation to the region
  • posterior femoral cutaneous nerve provides cutaneous innervation
  • femoral and obturator nerves may, in part, supply the anterior reaches

Key Relations within the fossa

  • superficial to deep: sciatic n and branches, femoral v., femoral a.
  • arteries of genicular anastomosis applied to capsule and bone

Lymphatic drainage - popliteal lymph nodes

  • superficial drainage of leg enters popliteal fossa along with the lesser saphenous v.
  • deep drainage of leg enters popliteal fossa along with posterior tibial vessels
  • lymph from popliteal fossa ascend along femoral vessels to deep inquinal nodes


Posterior Mediastinum - August 30, 2007

Define the posterior mediastinum and discuss contents (nerves, viscera, lymphatics, vasculature), relationships and boundaries. (12pts)

Definition and Boundaries

  • superior - line from T4 toward jugular notch (only that part of line posterior to middle mediastinum)
  • inferior - diaphragm posterior to middle mediastinum; T12
  • lateral - fibrous layer of mediastinal parietal pleura
  • anterior - posterior to middle mediastinum
  • posterior - lateral aspects of vertebral bodies (includes sympathetic trunk)
  • medial - the middle of the posterior mediastinum is also midsaggital, i.e., a medial boundary does not exist


  • deep cardiac plexus
  • esophageal plexus (right and left vagus)
  • ventral rami of thoracic spinal nerves (intercostals nerves)
  • Sympathetic truck and related structures


  • right posterior intercostal arteries
  • esophageal arteries
  • bronchial arteries
  • aorta


  • azygos system of veins
  • arch of the azygos (subject to interpretation)
  • right superior intercostal vein (subject to interpretation)
  • right posterior intercostal veins


  • thoracic duct


  • bifurcation of trachea (Subject to interpretation)
  • esophagus


  • right posterior intercostal aa. - immediately deep to azygos system and sympathetic trunk
  • azygos system - azygos v. and hemiazygos v., cross anterior vertebral bodies superficial to right intercostal aa and deep to splanchnic nn.
  • thoracic sympathetic trunk - immediately superficial (lateral) to intercostal vessels
  • splanchnic nerves - coursing inferior medial and anterior from sympathetic trunk ganglia
  • ramus communican - branching posterior from sympathetic trunk ganglia and connecting to spinal nerve at intervertebral foramen
  • thoracic duct - superficial to azygos v. between esophagus and aorta, deviates to the left in superior region
  • esophagus and esophageal plexus - deviates to the right superiorly and left inferiorly; site of constrictions
  • aorta - left of vertebral bodies and esophagus
  • vagus n. - enters posterior to root of lung
  • bifurcation of trachea - immediately anterior to esophagus in superior region of posterior mediastinum
  • deep cardiac plexus and nerves - anterior to tracheal bifurcation


Medial Longitudinal Arch - August 30, 2007

Discuss the medial longitudinal arch and indicate your understanding of the bones, ligaments, muscles, and fascial specialization, and relate your anatomical knowledge to the consequences of damage to these structures. (12 pts)


  • calcaneus, head of talus, navicular, cuneiforms, and first 3 metatarsals (heads of) - labeled drawing was helpful (with discussion)
  • talocalcaneonavicular joint has the head of the talus of as the "keystone" wedged between the calcaneus and navicular
  • spring ligament is the floor of the talocalcaneonavicular joint and acts as a "staple" to approxmate the navicular to the calcaneus


  • Spring ligament - plantar calcaneonavicular ligament
    • maintains the head of talus at the peak of the medial longitudinal arch
    • stretching of this ligament allows the navicular bone to move away from the calcaneus; if stretched, the talus falls
  • minor support by long and short plantar


* Suspends the arch
    • tibialis posterior - suspends the arch
    • tibialis anterior - suspends the arch
    • extensor hallucis longus - suspends the arch
  • Staples the arch
    • peroneus longus - tendinous insertions staple the arch
      • note: peroneus longus is a tie beam for the transverse arch, a vertical support for the lateral longitudinal arch, and a staple for the medial longitudinal arch
    • tibialis posterior - tendinous insertions staple the arch
    • tibialis anterior - tendinous insertions staple the arch
  • "Tie beam" support - structures serving to approximate the bones of the arch
    • intrinsic mm - adductor hallucis oblique head, flexor hallucis, abductor hallucis, flexor digitorum brevis, quadratus plantae, lumbricals
    • extrinsic mm - flexor hallucis longus is key, tibialis posterior, flexor digitorum longus
    • fascia - plantar aponeurosis and skin

Fascial Specializations

  • fascia - plantar aponeurosis and skin; tie beam
  • skin

Neural and Vascular Relationships

  • Tibial nerve and posterior tibial artery elaborate medial and lateral plantar arteries and nerves
  • Medial and lateral plantar nerves and vessels pass deep to abductor hallucis to enter plantar region
  • Lateral planter nerve and vessels pass superior to flexor hallucis brevis and inferior to quadratus plantae to reach lateral aspect of sole.

Consequences of Damage

  • A fallen medial arch indicates failure of the spring ligament to approximate the navicular bone to the calcaneus. As a result, the head of the talus moves inferiorly into the region traversed by the medial and lateral plantar vessels and nerves. Compression of these structures could lead to cold feet (poor circulation) and paraesthesias (compressed nerves).





-- LorenEvey - 02 Sep 2007

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Topic revision: r1 - 30 Aug 2011, UnknownUser
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