Appendicular Muscles- Lower Extremities Flashcards
What is the fascia lata?
- The deep fascia of the thigh
- Encircles thigh muscles like a supportive stocking and tightly binds them together
- The fascia lata along with the intermuscular septa partition the thigh muscles into compartments, each with its own blood and nerve supply
- Most muscles of the thigh attach proximally to the os coxae and distally to the femur
- They work together to stabilize the highly mobile hip joint and support the body during standing and walking
What do the anterior compartment muscles do? (thigh)
- Either extend the knee or flex the thigh
What do the medial compartment muscles do? (thigh)
- Act as adductors of the thigh
What do the posterior compartment muscles do? (thigh)
- Act as both flexors of the knee and extensors of the thigh
- Some also may abduct the thigh
What are the psoas major and iliacus muscles? (anterior compartment)
- Attach to the anterior femur and flex the thigh at the hip
- Have different proximal attachments but share the same distal attachment to the lesser trochanter of the femur
- Together these muscles merge and attach to the femur as the iliopsoas
- They work synergistically to flex the thigh
What is the sartorius? (anterior compartment)
- A long, thin muscle that crosses over the anterior thigh and helps flex the thigh
- The rectus femoris also does this
What are the medial compartment muscles?
- Adductor longus, adductor brevis, gracilis and pectineus (primary adductors/ thigh flexors)
- Adductor magnus extends laterally and rotates the thigh as well as flexing it
- The obturator externus does not adduct the thigh but laterally rotates it
What is the lateral compartment muscle?
- Single muscle called the tensor fasciae latae
- Attaches to a lateral thickening of the fascia lata, called the iliotibial tract
- Abducts and medially rotates the thigh
- The iliotibial tract extends from the iliac crest to the lateral condyle of the tibia
What are the posterior compartment muscles?
- Includes 3 gluteal muscles and the hamstring muscle group
What is the gluteus maximus?
- The largest of the 3 gluteal muscles and one of the largest muscles in the whole body
- The chief extensor of the thigh
- Laterally rotates the thigh
What is the gluteus medius?
- Deep and lateral to the gluteus maximus
- Powerful abductor of the thigh
- Also medially rotates the thigh
- Intramuscular injections are often given in this muscle
What is the gluteus minimus?
- The smallest of the gluteal muscles
- Lies deep to the gluteus medius
- Abducts and medially rotates the thigh
What posterior compartment muscles are deep to the gluteal muscles?
- Piriformis, superior gemellus, obturator internus, inferior gemellus and quadratus femoris
- Organized from superior to inferior within the posterior thigh
- All laterally rotate the thigh and the hip joint, as when the legs are crossed with one ankle resting on the knee
What are the hamstrings? (posterior compartment)
- Biceps femoris, semimembranosus, and semitendinosus
- Share a common proximal attachment to the ischial tuberosity of the os coxae and distally attach to the leg
- These muscles move the thigh and the knee (primary thigh movement is extension)
What is the anterior (extensor) compartment of the thigh?
- Composed of the large quadriceps femoris
- Agonist of knee extension and the most powerful muscle in the body
- Has 4 heads: rectus femoris, vastus lateralis, vastus medialis and vastus intermedius which all converge into the single tendon
- Extends to the patella and then continues inferiorly as the patellar ligament and attaches to the tibial tuberosity
- Acts with the iliopsoas to flex the hip while the leg is kicking off the ground
What is the rectus femoris? (quadriceps femoris)
- On the anterior surface of the thigh
- Proximally attaches to the os coxae
- Also flexes the thigh
What is the vastus lateralis? (quadriceps femoris)
- Forms the anterolateral surface of the thigh
What is the vastus medialis?
- Forms the anteromedial surface of the thigh
What is the vastus intermedius?
- Positioned deep to the rectus femoris and sandwiched between the other 2 vastus muscles
What is the sartorius? (anterior compartment)
- Projects obliquely across the anterior surface of the thigh from the superolateral to the inferomedial side
- Acts on both the hip and knee joints, flexing and laterally rotating the thigh while flexing the leg
- Longest muscle in the body (used when crossing our legs)
What is the gracilis? (medial compartment)
- Adducts the thigh
- Also flexes the leg, as it spans the knee joint
What is the biceps femoris? (posterior compartment)
- 2 headed muscle that attaches to the lateral side of the leg
- Can laterally rotate the leg while it’s being flexed
- The long head proximally attaches to the ischial tuberosity with the semimembranosus and semitendinosus
- The short head attaches proximally to the linea aspera of the femur (cannot move the thigh but assists in flexing the leg)
What is the semimembranosus? (posterior compartment)
- Deep to the semitendinosus
- Extends from the ischial tuberosity to the medial side of the leg
- Medially rotate the leg while flexed
What is the semitendinosus? (posterior compartment)
- Superficial to the semimembranosus
- Attached to the medial leg
- Medially rotate the leg while flexed
What are the crural muscles?
- Muscles that move the ankle, foot and toes
- Some of these muscles also help to flex the leg
- Deep fascia partitions the leg musculature into 3 compartments (anterior, lateral and posterior)
What is the extensor digitorum longus? (anterior compartment)
- Sends 4 long tendons to attach to the dorsal surface of toes 2-5
- Dorsiflexes the foot and extends toes 2-5
What is the extensor hallucis longus? (anterior compartment)
- Sends a tendon to the dorsum of the great toe (hallux)
- Dorsiflexes the foot and extends the great toe
What is the fibularis tertius? (anterior compartment)
- Extends from the extensor digitorum longus muscle
- It dorsiflexes and weakly everts the foot
- The presence of this muscle varies among populations and individuals
What is the tibialis anterior? (anterior compartment)
- The primary dorsiflexor of the foot and ankle
- Attaches to the medial plantar side of the foot
- Also inverts the foot
What is extensor retinaculum? (anterior compartment)
- Holds tendons of the muscles within the anterior compartment tightly against the ankle
- Are multiple deep fascia thickenings
What is the fibularis longus? (lateral compartment)
- Long and flat muscle that is superficial and lateral
- Covers the fibula
- Its tendon attaches to the plantar side of the foot on the base of metatarsal I and the medial cuneiform
- Powerful evertor of the foot and weak plantar flexor
What is the fibularis brevis? (lateral compartment)
- Lies deep to the fibularis longus
- Its tendon attaches to the base of the fifth metatarsal
- Powerful evertor of the foot and weak plantar flexor that works synergistically with the fibularis longus
What is the superficial layer of the posterior compartment?
- Contains 3 muscles: gastrocnemius, soleus and plantaris
What is the gastrocnemius? (superficial posterior compartment)
- The most superficial muscle
- Has 2 thick bellies (lateral and medial heads)
- Collectively form the prominence of the posterior part of the leg (referred to as the calf)
- Spans both the knee and ankle joints
- Flexes the leg and plantar flexes the foot
- Tendon of the lateral head may have a normal variant sesamoid bone or cartilage called fabella
What is the soleus? (superficial posterior compartment)
- Deep to the gastrocnemius
- Broad and flat muscle that resembles a flat fish
- Muscle plantar that flexes the foot
What is the plantaris? (superficial posterior compartment)
- Small muscle that is absent in some individuals
- Projects obliquely between the gastrocnemius and soleus muscles
- Weak leg flexor and plantar flexor of the foot
What is the triceps surae? (superficial posterior compartment)
- Gastrocnemius and soleus collectively form this muscle group
- Most powerful plantar flexors of all the leg muscles
- Share a common distal tendon called the calcaneal tendon or achilles tendon
What is the deep layer of the posterior compartment?
- Contains 4 muscles: flexor digitorum longus, flexor hallucis longus, tibialis posterior and popliteus
What is the flexor digitorum longus? (deep posterior compartment)
- Attaches to the distal phalanges of toes 2-5
- Plantar flexes the foot
- Flexes the MP, PIP and DIP joints of does 2-5
What is the flexor hallucis longus? (deep posterior compartment)
- Proximally attaches to the fibula
- Tendon travels medially and runs along the plantar side of the foot to attach to the distal phalanx of the great toe
- Plantar flexes the foot and flexes the great toe
What is the tibialis posterior? (deep posterior compartment)
- The deepest posterior compartment muscle
- It plantar flexes and inverts the foot
What is the popliteus? (deep posterior compartment)
- Forms the floor of the popliteal fossa and acts to flex the leg
- Medially rotates the tibia slightly to “unlock” the fully extended knee joint
- Attaches both proximally and distally in the popliteal region so it only moves the knee and not the foot
What do the intrinsic muscles of the foot do?
- Support the arches and move the toes to aid locomotion
- Most of these muscles are comparable to the intrinsic muscles of the hand (not as precise movements can be made with the foot however)
- Made up of a dorsal and plantar group of muscles
What is the extensor hallucis brevis? (dorsal foot muscle)
- Extends the MP joint of the great toe
What is the extensor digitorum brevis? (dorsal foot muscle)
- Deep to the tendons of the extensor digitorum longus
- Extends the MP, PIP and DIP joints of toes 2-4
What is the plantar aponeurosis? (plantar foot muscle)
- Supports the plantar surface of the foot
- Formed from deep fascia of the foot
- Extends between the phalanges of the toes and the calcaneus
- Also encloses plantar muscles of the foot
What is flexor digitorum brevis? (superficial plantar foot muscle)
- Attaches to the middle phalanges of the toes so it can flex MP and PIP joints (not DIP joints though) of toes 2-5
What is the abductor hallucis? (superficial plantar foot muscle)
- Abducts the great toe
What is the abductor digiti minimi? (superficial plantar foot muscle)
- Abducts the small toe
What is the quadratus plantae? (deep plantar foot muscle)
- Thick, medial muscle that attaches to the tendons of the digitorum longus
- Pulls the slanted flexor digitorum longus tendons in a posterior fashion so that toes 25 may be flexed properly and not at an angle
What are the lumbrical muscles? (deep plantar foot muscle)
- Small muscles that attach to the tendons of the flexor digitorum longus
- Serve to flex MP joints and extend DIP and PIP joints of toes 2-5
What is the adductor hallucis? (deeper plantar foot muscle)
- Adducts the great toe
What are the flexor hallucis brevis? (deeper plantar foot muscle)
- Medial muscle that flexes the great toe
What is the flexor digiti minimi brevis? (deeper plantar foot muscle)
- Lateral muscle which flexes the small toe
What are the dorsal and plantar interossei? (deepest plantar foot muscle)
- Dorsal: abduct the totes
- Plantar: adduct the toes
