Discuss the boundaries (6 directions), contents, and relationships in the lateral compartment of the leg; include muscles, nerves, vasculature, and fascial specializations. Indicate the function of the lateral compartment of the leg, and define the effects of injury to this comparatment on the actions of the foot and support of the arches (10 pts)
General
General comments here.
Fascial specializations
crual fascia - investing fascia making up the lateral boundary of the lateral compartment
Anterior intermuscular septum attaches to fibula - separates the lateral from the anterior compartment
Posterior intermuscular septum attaches to fibula - separates the lateral from the posterior compartment
Boundaries
Superior - crual fascia knee joint capsule
Inferior - continuous with dorsum of foot
Anterior - anterior intermuscular septum
Posterior - posterior intermuscular septum
Lateral - crual fascia between anterior and posterior intermuscular septa
Medial - fibula
Contents and relationships
Muscles
peroneus longus
peroneus brevis
Nerves
Deep peroneal nerve - pierces posterior and anterior intermuscular septa (crual fascia)
crosses lateral aspect of the neck of the fibula prior to entering anterior compartment
supplies a twig to knee joint and, commonly, a motor branch to peroneus longus prior to entering anterior compartment
Superficial peroneal nerve - pierces posterior intermuscular to enter lateral compartment
crosses neck of fibula slightly inferior to deep peroneal nerve and more longitudinal
extends inferior between peroneus longus and brevis and provides motor innervation to peroneus brevis and peroneus longus
pierces the crual fascia to supply a cutaneous distribution on the dorsum of the foot
Vasculature
fibular circumflex artery - superior in compartment
peroneal artery (posterior compartment) - branches pierce posterior intermuscular septum to supply middle of lateral compartment
branches of the malleolar anastomosis supply the inferior aspect of the lateral compartment
Actions at the foot
Peroneus longus and brevis are primarily everters of the foot and secondary for plantar flexion
Support of the arches of the foot
Peroneus longus and brevis support the lateral longitudinal arch as "suspension" elements
Peroneus longus supports the transverse arch as a "tie-beam" element
Peroneus longus supports the medial longitudinal arch as a staple - splays across plantar tarsal joints
Injury
Damage to the lateral compartment would cause the foot to be inverted due to unopposed inverters (tibialis anterior/posterior). The lateral longitudinal arch would weaken due to reduced superior support. The transverse arch would weaken to do reduced transverse support (tie beam). The medial longitudinal arch would be minimally effected.
Discuss the superior gluteal nerve - its location and course in the gluteal region. Explain what may have occur with an intragluteal injection to the right buttock and why there could be a gate problem. Will both extremities be altered insofar as actions? Include the actions of muscles innervated by the superior gluteal nerve, as well as origins and insertions. How would the patient compensate for this injury during walking? (10 pts)
Anatomy of the superior gluteal nerve
Leaves the pelvic cavity by way of the greater sciatic foramen to enter the gluteal region
Enters the gluteal region superior to the piriformis muscle
Extends laterally across gluteal region in a fascial plane deep (anterior) to gluteus medius and superficial (posterior) to gluteus minimus and supplies these two muscles
Extends as far laterally as tensor fascia lata and supplies this muscle
Vasculature supply is largely by the superior gluteal artery and vein
Intragluteal injection
Accidental injection into the upper medial quadrant of the gluteal region puts the superior gluteal nerve at risk
Upper lateral quadrant is preferred for injection because the super gluteal nerve has ramified prior the reaching this location
Origins and insertions based on proximal/distal
Gluteus medius - origin: ala of ilium between anterior and posterior lines, insertion: superior greater trochanter
Gluteus minimus - origin: ala of ilium between anterior and inferior gluteal lines, insertion: superior greater trochanter anterior to gluteus medius
Tensor fascia lata - anterior superior iliac spine, insertion: head of fibula by way of joint capsule and iliotibial tract
Actions
Gluteus medius - abduction of thigh, medial rotation
Gluteus minimus - abduction of thigh, medial rotation
Tensor fascia lata - abduction of thigh
Functional reversal for all three muscles - abduction (stabilization) of pelvis when lower extremity is planted
Disruption of gate - both lower extremities are effected
Paralysis of gluteus medius and minimus causes dropping of the pelvic girdle opposite to the side of injury. Normally, during walking, gluteus minimus and gluteus medius pull downward on the pelvic girdle opposite to the limb in swing phase. This action stabilizes the pelvic girdle. The gluteus minimus and medius mm are viewed as arising from the femur (greater trochanter) and inserting upon the ilium. This demonstrates a reversal of origin and insertion. When gluteus medius and minimus are paralyzed the pelvis drops to the side of swing phase. In order to restore the line of gravity, the patient leans to the side of the injury. The resulting gate is known as Trendelenberg's gate (gluteal waddle).
Discuss the structure of the left ventricle, including the atrioventricular and semilunar valves. Would the pain in her left upper extremity be related to a problem with the heart? (10 pts)
General
Between the left atrium and ventricle is the bicuspid atrioventricular ( Mitral) valve
Between the left ventricle and aorta is aortic semilunar valves
Healthy valves permit little to no back flow
Integrated with the skeleton of the heart
Located in the ventricles (atrioventricular valves) and at the base of the arterial trunks (semilunar valves)
The atrioventricular valves and the semilunar valves are closed by the pressure (they are not closed by muscular contraction applied to the cusps)
Pulmonary veins to left atria to biscupid (mitral) valve to left ventricle to aortic valve to systemic circulation to coronary arteries during diastole
Atrioventricular valves close (lub) during systole whereas the semilunar valves close (dub) during diastole
Structure
Cone shaped having the aortic vestibule as the outflow path toward aortic valve
Myocardial walls are thickest for the left ventricle
Trabeculae carneae are fine and delicate relative to the right ventrical
Interventricular septum - pars muscularis and pars membranacea
Lymph drainage along coronary arteries toward tracheobronchial nodes and then bronchiomediastinal lymph trunks
Branches of the AV bundle run through interventricular septum and outer wall
Atrioventricular valve - Biscuspid (Mitral Valve)
Between the left atria and the left ventricle
Two cusps open into the left ventricle
Two papillary muscles - anterior and posterior
Resists extreme pressure generated by left ventricular contraction
Cusps are stabilized by chorda tendeneae - fibrous cords between cusps and papillary muscles
Ventricular contraction raises pressure - blood pools on ventricular side of cusps causing the cusps to approximate each other and close the valve
Adjustments by the papillary muscles and chorda tendeneae provide support and prevent eversion of the cusps into the atria
Note - contraction of the papillary muscles, in the absence of ventricular contraction, open, not close, the atrioventricular valves
Semilunar valve - aortic valve
Located at the base of the aortic trunk
Prevents reverse flow from the aorta to the left ventricle during diastole
Negative pressure of left ventricle and elastic recoil of systemic arteries move aortic blood toward the valve
Opened by blood flow during systole - cusps move toward aortic wall and block coronary ostia
Three cusps - no papillary muscles or chorda tendeneae
Left and right coronary cusps (feed coronary arteries) and a non-coronary cusp
Nodule - weighted fibrous thicking at the midline of the free edge of each cusp aids in approximating the cusps and closing the valve
Aortic sinus - space between the wall of the aorta and each cusp
Valve closed by pressure - blood pools in the aortic sinuses during diastole and aproximates the nodules
Referred pain to medial aspect of arm
Anatomic pathways for pain sensation (visceral) from the heart (epicardium) follow - cardiac plexuses, splanchnic nerves, rami communicantes, spinal nerve ventral ramus (intercostal nerve), dorsal root (dorsal root ganglion at T2), spinal cord at T2 (T1-4)
Anatomic pathways for pain sensation (somatic) from the medial arm follow - intercostobrachial nerve (T2), intercostal nerve, spinal nerve (ventral ramus), dorsal root (dorsal root ganglion at T2), spinal cord at T2.
Cross talk is thought to occur within the dorsal ganglia or within the spinal cord (CNS).
Comment - Blood flow to the coronary vessels
Coronary arteries are perfused during diastole when heart muscle is relaxed
During systole the coronary ostia are blocked by the open cusps of the aortic valve
During diastole blood pools in the aortic sinuses and closes the aortic valve.
Blood driven into the left and right aortic sinuses enters into the ostia of the coronary arteries.
Primary blood supply to the left ventricle and the interventricular septum is by the left coronary artery
Right coronary artery supplies part of posterior wall of left ventricle on diaphragmatic surface