Download Posterior thigh

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts

Anatomical terminology wikipedia, lookup

Anatomical terms of location wikipedia, lookup

Transcript
Posterior thigh & popliteal fossa (18)
Posterior
thigh
-functions to flex the knee & extend the thigh
-occupied primarily by a group of 3 muscles known collectively as the
hamstrings
*biceps femoris is located laterally & consists of a long head and short
head
*semimembranosus & semitendinosus are located medially 
semimembranosus is located immediately deep to semitendinosus
-origin of hamstrings is the ischial tuberosity (with one exception)  short
head of biceps femoris originates on the linea aspera of the femur
INSERTIONS
-biceps femoris inserts on the head of the fibula
-semitendinosus inserts on the medial surface of the superior tibia
-semimembranosus inserts on the posterior part of the media condyle of
the tibia
ACTIONS
-approaching full knee flexion, hamstrings have been shortened to the
point here hip extension is NOT possible
-when the hip is extended, the hamstring have been shortened to the point
where full knee flexion is NOT possible
-if lower limbs are fixed, the hamstrings help extend the trunk
-mildly rotate the legs when he knees are flexed- semitendinosus &
semimembranosus rotate medially, while biceps femoris rotates laterally
GAIT & POSTURE
-hamstrings help maintain a relaxed standing posture by preventing
forward-falling
*any trunk action that takes the center of gravity in front of the hips
strongly activates the hamstrings in order to restore balance
-during gait, hamstrings are most active when they are contracting
eccentrically in order to decelerate hip flexion and knee extension 
terminal swing
Hamstrin
gs injury
-strains about as twice as common as quadriceps strains
*proper warm up? Strength imbalance? Slight hyperextension of
hamstrings in resting position?
-strains most often occur in sports requiring rapid, or violent muscular
exertion (sprinting)  most occur when muscle is thrown into rapid
lengthening during terminal swing
-with hamstring fully lengthened (thigh flexed & leg extended) an avulsion
fx may occur
Motor
-sciatic nerve (L4-S3) passes through gluteal region but supplies NO
muscles there  supplies all posterior thigh muscles, all leg & foot muscles,
and most of the skin of the leg & foot
-one exception  hamstrings are innervated by the tibial division of the
sciatic nerve – the short head of the biceps femoris is innervated by the
fibular division of the sciatic nerve
Cutaneous
-most via the posterior femoral cutaneous nerve (S1-S3)
*supplies more skin than any other cutaneous nerve
*lateral aspect of posterior thigh is supplied by lateral femoral cutaneous
nerve (L2-L3- from lumbar plexus)
-main part of nerve is deep to fascia lata w/only terminal branches piercing
through the skin
Blood
supply
-NO major artery exclusive to the compartment – served indirectly by major
arteries
-internal iliac artery gives rise to the inferior gluteal artery  supplies
superior part of hamstrings
-profunda femoris gives rise to the medial circumflex femoral artery &
perforating arteries
-perforating arteries  unusual in that they have a transverse,
intercompartmental course
*these large arteries must be detected during surgery
lymphatics
-parallel the major route of venous drainage, femoral vein
-most drainage converges on the superficial inguinal lymph nodes and then
proceeds to the external iliac nodes
Popliteal
fossa
-important area of transition
-mostly fat-filled, diamond shaped, intermuscular space on the posterior
aspect of the knee
*visible when the knee is flexed
-poplitis means ham of the knee  note that in the extended leg, this
“ham” provides protection for fossa contents
-superior border semimembranosus & semitendinosus medially & biceps
femoris laterally
-inferior border  medial & lateral heads of gastrocnemius
*in a living person, the inferior triangle of the diamond is non-existent
until the two heads of the gastrocnemius are retracted from one another
-roof  skin & popliteal (deep) fascia which is continuous with fascia lata
and crural fascia
*fascia provides protection to fossa contents & serves as a weak
retinaculum for hamstrings tendons
-floor  femur, knee joint capsule, and popliteus muscle
Nerves
-sciatic nerve usually ends at the superior angle of the popliteal fossa by
dividing into the tibial & common fibular nerves
*tibial nerve bisects the popliteal fossa, while the common fibular nerve
follows the tendon of biceps femoris
-skin supplied by posterior cutaneous nerve of the thigh
-in the fossa, the tibial nerve gives rise to the medial sural cutaneous nerve,
while the common fibular nerve gives off the lateral sural cutaneous nerve
*lateral sural cutaneous nerve gives off the sural communicating branch
which joins the medial sural cutaneous nerve to form the sural nerve
Vasculature
-inferior border  posterior tibial veins form popliteal vein which in turn
becomes the femoral vein at the adductor hiatus
-on posterior aspect of the leg, small/short saphenous vein pierces the
popliteal fascia to drain into the popliteal vein
*surgical approaches to posterior knee, the small/short saphenous serves
as a superficial landmark (along with the medial sural cutaneous nerve) that
makes it easier to find the tibial nerve
-adductor canal  long, narrow passageway in the middle third of the
thigh, which extends the apex of the femoral triangle to the adductor hiatus
– an opening in the tendon of adductor magnus
*provides an intermuscular passage for the femoral artery & vein, the
nerve to vastus medialis (branch of femoral nerve), and saphenous nerve
-popliteal artery  continuation of the femoral artery; begins at the
adductor hiatus, ends at the inferior border of popliteus where it passes
deep to the tendinous arch of the soleus and divides into anterior &
posterior tibial arteries
*deepest structure in fossa but it can be palpated when compressed
against the tibia in the lower part of the fossa
*gives rise to multiple arterial branches which fall into 2 categories 
muscular branches & genicular branches
-genicular branches supply the capsule & ligaments of the knee joint & are
heavily involved in anastomosis, which provides extensive collateral
circulation around the knee
*5 branches  medial genicular arteries (superior & inferior) lateral
genicular arteries (superior & inferior) and middle genicular artery
Lymphatics
-superficial popliteal lymph nodes lie in the subcutaneous tissue
-deep nodes (~6-7) are located around the blood vessels
-usu. there is one node associated with the small saphenous vein, where it
drains into the popliteal vein
-drainage follows femoral vessels to deep inguinal nodes
Clinical
-popliteal fascia overlying the fossa is strong & resistant to expansion,
consequently the presence of tumors, abscesses, or any disease process
resulting in swelling usually leads to severe pain
-Baker’s (popliteal) cyst  protrusion of the bursa between
semimembranosus tendon and the medial head of gastrocnemius into the
fossa
*usu. result of chronic effusion from the knee joint
*tx  includes aspiration, but also arthroscopy, as intra-articular
pathology is usu. an underlying cause for the cyst
-arteriovenous fistula  combined injury of an artery & vein in close
proximity (as they are in the popliteal fossa) can result in an arteriovenous
fistula (AVF)
*such an injury may occur during procedures involving the knee joint,
such as intracapsular ligament reconstruction (though this is rare)
*in popliteal AVF blood is mostly shunted from artery to vein- with little
flow distally to the knee- necrosis of the leg and foot is possible