11.7 Appendicular Muscles of the Pelvic Girdle and Lower Limbs

Lindsay M. Biga; Staci Bronson; Sierra Dawson; Amy Harwell; Robin Hopkins; Joel Kaufmann; Mike LeMaster; Philip Matern; Katie Morrison-Graham; Kristen Oja; Devon Quick; Jon Runyeon; OSU OERU; OpenStax; Wendy Pomponio

Learning Objectives

By the end of this section, you will be able to:

Identify the following muscles and give their origins, insertions, actions and innervations:

Appendicular muscles of the pelvic girdle and lower limbs

APPENDICULAR MUSCLES OF THE PELVIC GIRDLE AND LOWER LIMBS

The appendicular muscles of the lower body position and stabilize the pelvic girdle, which serves as a foundation for the lower limbs. Comparatively, there is much more movement at the pectoral girdle than at the pelvic girdle. There is very little movement of the pelvic girdle because of its connection with the sacrum at the base of the axial skeleton and because the deep acetabulum provides a stable point of articulation with the head of the femur. The pelvic girdle’s lack of range of motion allows it to stabilize and support the body. The body’s center of gravity is in the area of the pelvis. If the center of gravity were not to remain fixed, standing up would be difficult. Therefore, what the leg muscles lack in range of motion and versatility, they make up for in size and power, facilitating the body’s stabilization, posture, and movement.

Gluteal Region Muscles That Move the Thigh

Most muscles that insert on the femur (the thigh bone) and move it, originate on the pelvic girdle. The major flexors of the hip are the psoas major and iliac which make up the iliopsoas group. Some of the largest and most powerful muscles in the body are the gluteal muscles or gluteal group. The gluteus maximus, one of the major extensors of the thigh at the hip, is the largest; deep to the gluteus maximus is the gluteus medius, and deep to the gluteus medius is the gluteus minimus, the smallest of the trio (Figure 11.4.22 and Figure 11.4.23).

The left panel shows the superficial pelvic and thigh muscles, the center panel shows the deep pelvic and thigh muscles. The right panel shows the posterior view of the pelvic and thigh muscles. — **Figure 11.4.22 –** **Hip and Thigh Muscles:** The large and powerful muscles of the hip that move the femur generally originate on the pelvic girdle and insert into the femur. The muscles that move the lower leg typically originate on the femur and insert into the bones of the knee joint. The anterior muscles of the femur extend the lower leg but also aid in flexing the thigh. The posterior muscles of the femur flex the lower leg but also aid in extending the thigh. A combination of gluteal and thigh muscles also adduct, abduct, and rotate the thigh and lower leg.

This table describes gluteal region muscles that move the femur. These muscles make up the iliopsoas group. The psoas major raises the knee at the hip, as if performing a knee attack; it also assists the lateral rotators in twisting the thigh (and lower leg) outward, and assists with bending over and maintaining posture. It originates in the lumbar vertebrae (L1 through L5) and thoracic vertebra (T12). The iliacus raises the knee at the hip, as if performing a knee attack; it also assists the lateral rotators in twisting the thigh (and lower leg) outward, and assists with bending over and maintaining posture. It originates in the iliac fossa, iliac crest, and lateral sacrum. These muscles make up the gluteal group. The gluteous maximus lowers the knee and moves the thigh back, as when getting ready to kick a ball. It originates in the dorsal ilium, sacrum, and coccyx. The gluteus medius opens the thigh, as when doing a split. It originates in the lateral surface of the ilium. The gluteus minimus brings the thighs back together. It originates in the external surface of the ilium. The tensor fascia lata assists with raising the knee at the hip and opening the thighs; it also maintains posture by stabilizing the iliotibial track, which connects to the knee. It originates in the anterior aspect of the iliac crest and the anterior superior iliac spine. These muscles make up the lateral rotators. The piriformis twists the thigh (and lower leg) outward; it also maintains posture by stabilizing the hip joint. It originates in the anterolateral surface of the sacrum. The obturator internus twists the thigh (and lower leg) outward; it also maintains posture by stabilizing the hip joint. It originates in the inner surface of the obturator membrane, the greater sciatic notch, and the margins of the obturator foramen. The superior gemellus twists the thigh (and lower leg) outward; it also maintains posture by stabilizing the hip joint. It originates in the ischial spine. The inferior gemellus twists the thigh (and lower leg) outward; it also maintains posture by stabilizing the hip joint. It originates in the ischial tuberosity. The quatratus femoris twists the thigh (and lower leg) outward; it also maints posture by stabilizing the hip joint. It originates in the ischial tuberosity. These muscles are adductors. The adductor longus brings the thighs back together; it also assists with raising the knee. It originates in the pubis near the pubic symphysis. The adductor brevis brings the thighs back together; it also assists with raising the knee. It originates in teh body of the pubis and in the inferior ramus of the pubis. The adductor magnus brings the thighs back together; it also assists with raising the knee and moving the thigh back. It originates in the ischial rami, the pubic rami, and the ischial tuberosity. The pectineus opens the thigh; it also assists with raising the knee and turning the thigh (and lower leg) inward. It originates in the pectineal line of the pubis. — **Figure 11.4.23** Gluteal Region Muscles That Move the Femur

The tensor fascia latae is a thick, squarish muscle in the superior aspect of the lateral thigh. It acts as a synergist of the gluteus medius and iliopsoas in flexing and abducting the thigh. It also helps stabilize the lateral aspect of the knee by pulling on the iliotibial tract (band), making it taut. Deep to the gluteus maximus, the piriformis, obturator internus, obturator externus, superior gemellus, inferior gemellus, and quadratus femoris laterally rotate the thigh at the hip.

Deep fascia in the thigh separates it into medial, anterior, and posterior compartments. The muscles in the medial compartment of the thigh responsible for adducting the femur at the hip are the adductor group including the adductor longus, adductor brevis, and adductor magnus which all adduct and medially rotate the thigh. The adductor longus also flexes the thigh, whereas the adductor magnus extends it. Like the adductor longs, the pectineus adducts and flexes the femur at the hip. The pectineus is located in the femoral triangle, which is formed at the junction between the hip and the leg and includes the femoral nerve, the femoral artery, the femoral vein, and the deep inguinal lymph nodes. The strap-like gracilis adducts the thigh in addition to flexing the leg at the knee

Thigh Muscles That Move the Femur, Tibia, and Fibula

The muscles of the anterior compartment of the thigh flex the thigh and extend the leg. This compartment contains the quadriceps femoris group, which is comprised of four muscles that extend the leg and stabilize the knee. Within the compartment the rectus femoris is on the anterior aspect of the thigh, the vastus lateralis is on the lateral aspect of the thigh, the vastus medialis is on the medial aspect of the thigh, and the vastus intermedius is between the vastus lateralis and vastus medialis and deep to the rectus femoris. The tendon common to all four is the quadriceps tendon (patellar tendon), which inserts into the patella and continues below it as the patellar ligament. The patellar ligament attaches to the tibial tuberosity. In addition to the quadriceps femoris, the sartorius is a band-like muscle that extends from the anterior superior iliac spine to the medial side of the proximal tibia. This versatile muscle flexes the leg at the knee and flexes, abducts, and laterally rotates the thigh at the hip. This muscle allows us to sit cross-legged.

The posterior compartment of the thigh includes muscles that flex the leg and extend the thigh. The three long muscles on the back of the thigh are the hamstring group, which flexes the knee. These are the biceps femoris, semitendinosus, and semimembranosus. The tendons of these muscles form the upper border of the popliteal fossa, the diamond-shaped space at the back of the knee.

Muscles That Move the Feet and Toes

Similar to the thigh muscles, the muscles of the leg are divided by deep fascia into compartments, although the leg has three: anterior, lateral, and posterior.

The left panel shows the superficial muscles that move the feet and the center panel shows the posterior view of the same muscles. The right panel shows the deep muscles of the right lower leg. — **Figure 11.4.25 – Muscles of the Lower Leg:** The muscles of the anterior compartment of the lower leg are generally responsible for dorsiflexion, and the muscles of the posterior compartment of the lower leg are generally responsible for plantar flexion. The lateral and medial muscles in both compartments invert, evert, and rotate the foot.

This tables describes the muscles that move the feet and toes. These muscles make up the anterior compartment of the leg. The tibialis anterior raises the sole of the foot off the ground, as when preparing to foot-tap; it also bends the inside of the foot upwards, as when catching your balance while falling laterally toward the opposite side as the balancing foot. It originates in the lateral condyle and upper tibial shaft and in the interosseous membrane. The extensor hallucis longus raises the sole of the foot off the ground, as when preparing to foot-tap; it also extends the big toe. It originates in the anteromedial fibula shaft and interosseous membrane. The extensor digitorum longus raises the sole of the foot off the ground, as when preparing to foot-tap; it also extends the toes. It originates in the lateral condyle of the tibia, the proximal portion of the fibula, and the interosseous membrane. These muscles make up the lateral compartment of the leg. The fibularis longus lowers the sole of the foot to the ground, as when foot-tapping or jumping; it also bends the inside of the foot downwards, as when catching your balance while falling laterally toward the same side as the balancing foot. It originates in the upper portion of the lateral fibula. The fibularis (peroneus) brevis lowers the side of the foot to the ground, as when foot-tapping or jumping; it also bends the inside of the foot downward, as when catching your balance while falling laterally toward the same side as the balancing foot. It originates in the distal fibula shaft. These superficial muscles make up the posterior compartment of the leg. The gastrocnemius lowers the sole of the foot to the ground, as when foot-tapping or jumping; it also assists in moving the back of the lower legs up and back toward the buttocks. It originates in the medial and lateral condyles of the femur. The soleus lowers the sole of the foot the ground, as when foot-tapping or jumping; it also maintains posture while walking. It originates in the superior tibia, fibula, and interosseous membrane. The plantaris lowers the sole of the foot to the ground, as when foot-tapping or jumping; it also assists in moving the back of the lower legs up and back toward the buttocks. It originates in the posterior femur above the lateral condyle. The tibialis posterior lowers the sole of the foot to the ground, as when foot-tapping or jumping. It originates in the superior tibia and fibula and in the interosseous membrane. These deep muscles also make up the posterior compartment of the leg. The popliteus moves the back of the lower legs up and back toward the buttocks; it also assists in rotation of the leg at the knee and thigh. It originates in the lateral condyle of the femur and the lateral meniscus. The flexor digitorum longus lowers the sole of the foot to the ground, as when foot-tapping or jumping; it also bends the inside of the foot upward and flexes the toes. It originates in the posterior tibia. The flexor hallicis longus flexes the big toe. It originates in the midshaft of the fibula and in the interosseous membrane. — **Figure 11.4.26** Muscles That Move the Feet and Toes

The muscles in the anterior compartment of the leg all contribute to dorsiflexion: the tibialis anterior, a long and thick muscle on the lateral surface of the tibia, the extensor hallucis longus, deep under it, and the extensor digitorum longus, lateral to it. The fibularis tertius, a small muscle that originates on the anterior surface of the fibula, is associated with the extensor digitorum longus and sometimes fused to it, but is not present in all people. Thick bands of connective tissue called the superior extensor retinaculum (transverse ligament of the ankle) and the inferior extensor retinaculum, hold the tendons of these muscles in place during dorsiflexion.

The lateral compartment of the leg includes two muscles which contribute to eversion and plantar flexion: the fibularis longus (peroneus longus) and the fibularis brevis (peroneus brevis). The superficial muscles in the posterior compartment of the leg all insert onto the calcaneal tendon (Achilles tendon), a strong tendon that inserts into the calcaneal bone of the ankle, all contribute to plantar flexion. The muscles in this compartment are large and strong and keep humans upright. The most superficial and visible muscle of the calf is the gastrocnemius. Deep to the gastrocnemius is the wide, flat soleus. The plantaris runs obliquely between the two; some people may have two of these muscles, whereas no plantaris is observed in about seven percent of other cadaver dissections. The plantaris tendon is a desirable substitute for the fascia lata in hernia repair, tendon transplants, and repair of ligaments. There are four deep muscles in the posterior compartment of the leg as well: the popliteus, flexor digitorum longus, flexor hallucis longus, and tibialis posterior all contribute to plantar flexion or inversion of the foot.

The foot also has intrinsic muscles, which originate and insert within it (similar to the intrinsic muscles of the hand). These muscles primarily provide support for the foot and its arch, and contribute to movements of the toes (Figure 11.4.27 and Figure 11.4.28). The principal support for the longitudinal arch of the foot is a deep fascia called plantar aponeurosis, which runs from the calcaneus bone to the toes (inflammation of this tissue is the cause of “plantar fasciitis,” which can affect runners. The intrinsic muscles of the foot include the extensor digitorum brevis on the dorsal aspect and a plantar group, which consists of four layers.

This figure shows the muscles of the foot. The top panel shows the lateral view of the dorsal muscles. The bottom left panel shows the superficial muscles of the left sole, the center panel shows the intermediate muscles of the left sole, and the right panel shows the deep muscles of the left sole. — **Figure 11.4.27 –** **Intrinsic Muscles of the Foot:** The muscles along the dorsal side of the foot (a) generally extend the toes while the muscles of the plantar side of the foot (b, c, d) generally flex the toes. The plantar muscles exist in three layers, providing the foot the strength to counterbalance the weight of the body. In this diagram, these three layers are shown from a plantar view beginning with the bottom-most layer just under the plantar skin of the foot (b) and ending with the top-most layer (d) located just inferior to the foot and toe bones.

This table describes intrinsic muscles in the foot. The dorsal group consists of the extensor digitorum brevis, which extends toes 2 through 5. It originates in the calcaneus and the extensor retinaculum. These muscles make up layer 1 of the plantar group. The abductor hallucis abducts and flexes the big toe. It originates in the calcaneal tuberosity and flexor retinaculum. The flexor digitorum brevis flexes toes 2 through 4. It originates in the calcaneal tuberosity. The abductor digiti minimi abducts and flexes the small toe. It originates in the calcaneal tuberosity. These muscles make up layer 2 of the plantar group. The quadratus plantae assists in flexing toes 2 through 5. It originates in the medial and lateral sides of the calcaneus. The lumbricals extend toes 2 through 5 at the interphalangeal joints; they also flex the small toes at the metatarsophalangeal joints. They originate in the tendons of the flexor digitorum longus. These muscles make up layer 3 of the plantar group. The flexor hallucis brevis flexes the big toe. It originates in the lateral cuneiform and in the cuboid bones. The adductor hallucis adducts and flexes the big toe. It originates in the bases of metatarsals 2 through 4, in the fibularis longus tendon sheath, and in the ligament across the metatarsophalangeal joints. The flexor digiti minimi brevis flexes the small toe. It originates in the base of metatarsal 5 and in the tendon sheath of the fibularis longus. These muscles make up layer 4 of the plantar group. The dorsal interossei abducts and flexes the middle toes at the metatarsophalangeal joints; it also extends the middle toes at the interphalangeal joints. It originates in the sides of the metatarsals. The plantar interossei abducts toes 3 through 5; it also flexes the proximal phalanges and extends the distal phalanges. It originates in the side of each metatarsal that faces metatarsal 2 (absent from metatarsal 2). — **Figure 11.4.28** Intrinsic Muscles in the Foot

Chapter Review

The pelvic girdle attaches the legs to the axial skeleton. The hip joint is where the pelvic girdle and the leg come together. The hip is joined to the pelvic girdle by many muscles. In the gluteal region, the psoas major and iliacus form the iliopsoas. The large and strong gluteus maximus, gluteus medius, and gluteus minimus extend and abduct the femur. Along with the gluteus maximus, the tensor fascia lata muscle forms the iliotibial tract. The lateral rotators of the femur at the hip are the piriformis, obturator internus, obturator externus, superior gemellus, inferior gemellus, and quadratus femoris. On the medial part of the thigh, the adductor longus, adductor brevis, and adductor magnus adduct the thigh and medially rotate it. The pectineus muscle adducts and flexes the femur at the hip.

The thigh muscles that move the femur, tibia, and fibula are divided into medial, anterior, and posterior compartments. The medial compartment includes the adductors, pectineus, and the gracilis. The anterior compartment comprises the quadriceps femoris, quadriceps tendon, patellar ligament, and the sartorius. The quadriceps femoris is made of four muscles: the rectus femoris, the vastus lateralis, the vastus medius, and the vastus intermedius, which together extend the knee. The posterior compartment of the thigh includes the hamstrings: the biceps femoris, semitendinosus, and the semimembranosus, which all flex the knee.

The muscles of the leg that move the foot and toes are divided into anterior, lateral, superficial- and deep-posterior compartments. The anterior compartment includes the tibialis anterior, the extensor hallucis longus, the extensor digitorum longus, and the fibularis (peroneus) tertius. The lateral compartment houses the fibularis (peroneus) longus and the fibularis (peroneus) brevis. The superficial posterior compartment has the gastrocnemius, soleus, and plantaris; and the deep posterior compartment has the popliteus, tibialis posterior, flexor digitorum longus, and flexor hallucis longus.

Review Questions

Critical Thinking Questions

Which muscles form the hamstrings? How do they function together?
Which muscles form the quadriceps? How do they function together?

Glossary

adductor brevis: muscle that adducts and medially rotates the thigh

adductor longus: muscle that adducts, medially rotates, and flexes the thigh

adductor magnus: muscle with an anterior fascicle that adducts, medially rotates and flexes the thigh, and a posterior fascicle that assists in thigh extension

anterior compartment of the leg: region that includes muscles that dorsiflex the foot

anterior compartment of the thigh: region that includes muscles that flex the thigh and extend the leg

biceps femoris: hamstring muscle

calcaneal tendon: (also, Achilles tendon) strong tendon that inserts into the calcaneal bone of the ankle

extensor digitorum brevis: muscle that extends the toes

extensor digitorum longus: muscle that is lateral to the tibialis anterior

extensor hallucis longus: muscle that is partly deep to the tibialis anterior and extensor digitorum longus

femoral triangle: region formed at the junction between the hip and the leg and includes the pectineus, femoral nerve, femoral artery, femoral vein, and deep inguinal lymph nodes

fibularis brevis: (also, peroneus brevis) muscle that plantar flexes the foot at the ankle and everts it at the intertarsal joints

fibularis longus: (also, peroneus longus) muscle that plantar flexes the foot at the ankle and everts it at the intertarsal joints

fibularis tertius: small muscle that is associated with the extensor digitorum longus

flexor digitorum longus: muscle that flexes the four small toes

flexor hallucis longus: muscle that flexes the big toe

gastrocnemius: most superficial muscle of the calf

gluteal group: muscle group that extends, flexes, rotates, adducts, and abducts the femur

gluteus maximus: largest of the gluteus muscles that extends the femur

gluteus medius: muscle deep to the gluteus maximus that abducts the femur at the hip

gluteus minimus: smallest of the gluteal muscles and deep to the gluteus medius

gracilis: muscle that adducts the thigh and flexes the leg at the knee

hamstring group: three long muscles on the back of the leg

iliacus: muscle that, along with the psoas major, makes up the iliopsoas

iliopsoas group: muscle group consisting of iliacus and psoas major muscles, that flexes the thigh at the hip, rotates it laterally, and flexes the trunk of the body onto the hip

iliotibial tract: muscle that inserts onto the tibia; made up of the gluteus maximus and connective tissues of the tensor fasciae latae

inferior extensor retinaculum: cruciate ligament of the ankle

inferior gemellus: muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip

lateral compartment of the leg: region that includes the fibularis (peroneus) longus and the fibularis (peroneus) brevis and their associated blood vessels and nerves

medial compartment of the thigh: a region that includes the adductor longus, adductor brevis, adductor magnus, pectineus, gracilis, and their associated blood vessels and nerves

obturator externus: muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip

obturator internus: muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip

patellar ligament: extension of the quadriceps tendon below the patella

pectineus: muscle that abducts and flexes the femur at the hip

pelvic girdle: hips, a foundation for the lower limb

piriformis: muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip

plantar aponeurosis: muscle that supports the longitudinal arch of the foot

plantar group: four-layered group of intrinsic foot muscles

plantaris: muscle that runs obliquely between the gastrocnemius and the soleus

popliteal fossa: diamond-shaped space at the back of the knee

popliteus: muscle that flexes the leg at the knee and creates the floor of the popliteal fossa

posterior compartment of the leg: region that includes the superficial gastrocnemius, soleus, and plantaris, and the deep popliteus, flexor digitorum longus, flexor hallucis longus, and tibialis posterior

posterior compartment of the thigh: region that includes muscles that flex the leg and extend the thigh

psoas major: muscle that, along with the iliacus, makes up the iliopsoas

quadratus femoris: muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip

quadriceps femoris group: four muscles, that extend and stabilize the knee

quadriceps tendon: (also, patellar tendon) tendon common to all four quadriceps muscles, inserts into the patella

rectus femoris: quadricep muscle on the anterior aspect of the thigh

sartorius: band-like muscle that flexes, abducts, and laterally rotates the leg at the hip

semimembranosus: hamstring muscle

semitendinosus: hamstring muscle

soleus: wide, flat muscle deep to the gastrocnemius

superior extensor retinaculum: transverse ligament of the ankle

superior gemellus: muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip

tensor fascia lata: muscle that flexes and abducts the thigh

tibialis anterior: muscle located on the lateral surface of the tibia

tibialis posterior: muscle that plantar flexes and inverts the foot

vastus intermedius: quadricep muscle that is between the vastus lateralis and vastus medialis and is deep to the rectus femoris

vastus lateralis: quadricep muscle on the lateral aspect of the thigh

vastus medialis: quadricep muscle on the medial aspect of the thigh

Solutions

Answers for Critical Thinking Questions

Arranged into layers, the muscles of the abdominal wall are the internal and external obliques, which run on diagonals, the rectus abdominis, which runs straight down the midline of the body, and the transversus abdominis, which wraps across the trunk of the body.
Both diaphragms are thin sheets of skeletal muscle that horizontally span areas of the trunk. The diaphragm separating the thoracic and abdominal cavities is the primary muscle of breathing. The pelvic diaphragm, consisting of two paired muscles, the coccygeus and the levator ani, forms the pelvic floor at the inferior end of the trunk

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Mohawk - PN Structure & Function of the Human Body Copyright © 2019 by Lindsay M. Biga, Staci Bronson, Sierra Dawson, Amy Harwell, Robin Hopkins, Joel Kaufmann, Mike LeMaster, Philip Matern, Katie Morrison-Graham, Kristen Oja, Devon Quick, Jon Runyeon, OSU OERU, and OpenStax is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License, except where otherwise noted.