Anatomy - Muscles of the Lower Body


Front Back
Pectoralis minor - Description Flat, thin muscle directly beneath and obscured by pectoralis major
Pectoralis minor - Origin anterior surfaces of ribs 3-5 (or 2-4)
Adductor longus - Description Overlies middle aspect of adductor magnus; most anterior of adductor muscles
Quadratus lumborum - Description Fleshy muscle forming part of posterior abdominal wall
Quadratus lumborum - Origin iliac crest and lumbar fascia
Quadratus lumborum - Insertion transverse processes of upper lumbar vertebrae and lower margin of 12th rib
Quadratus lumborum - Action flexes vertebral column laterally when acting separately; when pair acts jointly, lumbar spine is extended and 12th rib is fixed; maintains upright posture, assists in forced inspiration
Quadratus lumborum - Innervation T12 and upper lumbar spinal nerves (ventral rami)
Pectoralis minor - Insertion coracoid process of scapula
Pectoralis minor - Action With ribs fixed, draws scapula forward and downward; with scapula fixed, draws rib cage superiorly
Pectoralis minor - Innervation Medial and lateral pectoral nerves (C6-C8)
Adductor magnus - Innervation obturator nerve and sciatic nerve (L2-L4)
Adductor longus - Origin pubic near pubic symphysis
Adductor longus - Insertion linea aspera
Serratus anterior - Description Fan-shaped muscle; lies deep to scapula, beneath and inferior to pectoral muscles on lateral rib cage; forms medial wall of axilla, orings have serrated or sawtooth, appearance; paralysis results in "winging" of vertebral border of scapula away from chest wall, making arm elevation impossible
Serratus anterior - Origin by a series of muscle slips from ribs 1-8 (or 9)
Serratus anterior - Insertion entire anterior surface of vertebral border of scapula
Serratus anterior - Action Prime movers to protract and hold scapula against chest wall; rotates scapula so that its inferior angle moves laterally and upward; raises point of shoulder; important role in abduction and raising of arm and in horizontal arm movements (pushing, punching); called "boxer's muscle"
Serratus anterior - Innervation Long thoracic nerve (C5-C7)
Pectoralis major - Origin sternal end of clavicle, sternum, cartilage of ribs 1-6 (or 7), and aponeurosis of external oblique muscle
Pectoralis major - Insertion fibers converge to insert by a short tendon into greater tubercle of humerus
Pectoralis major - Action Prime mover of arm flexion; rotates arm medially; adducts arm against resistance; with scapula (and arm) fixed, pulls rib cage upward, thus can help in climbinb, throwing, pushing, and in forced inspiration
Pectoralis major - Innervation lateral and medial pectoral nerves (C5-C6, and T1)
Deltoid - Description thick, multipennate muscle forming rounded shoulder muscle mass; responsible for roundness of shoulder, a site commonly used for intramuscular injection, particularly in males, where it tends to be quite fleshy
Deltoid - Origin embraces insertion of the trapezius; lateral third of clavicle; acromion and spine of scapula
Deltoid - Insertion deltoid tuberosity of humerus
Deltoid - Action Prime mover of arm abduction when all its fibers contract simulataneously; antagonist of pectoralis major and latissimus dorsi, wihch adduct the arm; if only anterior fibers are active, can act powerfully in flexion and medial rotation of humerus, therefore synergist of pectoralis major, if only posterior fibers are active, effects extension and lateral rotation of arm; active during rhythmic arm swinging movements during walking
Deltoid - Innervation Axillary nerve (C5 and C6)
Supraspinatus - Description Named for its location on posterior aspect of scapula; deep to trapezius; a rotator cuff muscle
Supraspinatus - Origin supraspinous fossa of scapula
Supraspinatus - Insertion superior part of greater tubercle of humerus
Supraspinatus - Action stabilizes shoulder joint; helps to prevent downward dislocation of humerus, as when carrying a heavy suitcase; assists in abduction
Supraspinatus - Innervation suprascapular nerve
Teres minor - Description small, elongated muscle; lies inferior to infraspinatus and may be inseparable from that muscle; a rotator cuff muscle
Teres minor - Origin lateral border of dorsal scapular surface
Teres minor - Insertion greater tubercle of humerus inferior to infraspinatus insertion
Teres minor - Action addicts arm
Teres minor - Innervation axillary nerve
Teres major - Description tick, rounded muscle; located inferior to terest minor; helps form posterior wall of axilla (along with latissimus dorsi and subscapularis)
Teres major - Origin posterior surface of scapula at inferior angle
Teres major - Insertion intertubercular sulcus of the humerus; insertion tendon fused with that of latissimu dorsi
Teres major - Action posteromedially extends, medially rotates, and adducts humerus; synergist of latissimus dorsi
Infraspinatus - Description Partially covered by deltoid and trapezius; named for its scapular location; a rotator cuff muscle
Infraspinatus - Origin infraspinous fossa of scapula
Infraspinatus - Insertion greater tubercle of humerus posterior to insertion of supraspinatus
Infraspinatus - Action helps to hold head of humerus in glenoid cavity, strabilizing the shoulder joint; rotates humerus laterally
Infraspinatus - Innervation suprascapular nerve
Psoas major - Description longer, thicker, mroe medial muscle of the pair (butchers refer to this muscle as the tenderloin)
Psoas major - Origin by fleshy slips from tansverse processes, bodies, and discs of lumbar vertebrae and T12
Psoas major - Insertion lesser trochanter of femur via iliopsoas tendon
Psoas major - Action prime mover of flexing thigh or for flexing trunk on thigh during a bow; also effects lateral flexion of vertebral column; important postural muscle
Psoas major - Innervation ventral rami L1-L3
Sartorius - Description Straplike superficial muscle running obliquely across anterior surface of thigh to knee; longest muscle in body; crosses both hip and knee joints
Sartorius - Origin anterior superior iliac spine
Sartorius - Insertion winds around medial aspect of knee and inserts into medial aspect of proximal tibia
Gastrocnemius - Innervation tibial nerve (S1, S2)
Sartorius - Action flexes, abducts, and laterally rotates thigh; flexes knee (weak) as in a soccer kick; known as "tailor's muscle" because it helps effect cross-legged position in which tailors are often depicted
Sartorius - Innervation femoral nerve
Adductor magnus - Description A triangular muscle with a broad insertion; is a composite muscle that is part adductor and part hamstring in action
Adductor magnus - Origin ischial and pubic rami and iscial tuberosity
Adductor magnus - Insertion linea aspera and adductor tubercle of femur
Adductor magnus - Action Anterior part adducts and medially rotates and flexes thigh, posterior part is a synergist of hamstrings in thigh extension
Adductor longus - Action adducts, flexes, and medially rotates thigh
Adductor longus - Innervation anterior division of obturator nerve (L2-L4)
Adductor brevis - Description In contact with obturator externus muscle; largely concealed by adductor longus and pectineus
Adductor longus - Origin body and inferior ramus of pubis
Adductor longus - Insertion linea aspera above adductor longus
Adductor longus - Action adducts and medially rotates thigh
Adductor longus - Innervation obturator nerve
Rectus femoris - Description superficial muscle of anterior thigh; runs straight down thigh; longest head and only muscle of group to cross hip joint
Rectus femoris - Origin anterior inferior iliac spine and superior margin of acetabulum
Rectus femoris - Insertion patella and tibial tuberosity via patellar ligament
Rectus femoris - Action extends knee and flexes thigh at hip
Rectus femoris - Innervation femoral nerve (L2-L4)
Vastus lateralis - Description Largest head of the group, forms lateral aspect of thigh; a common intramuscular injection site, particularly in infants (who have poorly developed buttock and arm muscles)
Vastus lateralis - Origin greater trochanter, intertrochanteric line, linea aspera
Vastus lateralis - Insertion patella and tibial tuberosity via patellar ligament
Vastus lateralis - Action extends and stabilizes knee
Vastus lateralis - Innervation femoral nerve
Vastus medialis - Description Forms inferomedial aspect of thigh
Vastus medialis - Origin linea aspera, intertrochanteric line
Vastus medialis - Insertion as for rectus femoris
Vastus medialis - Action extends knee; inferior fibers stabilize patella
Vastus medialis - Innervation femoral nerve
Gluteus maximus - Description largest and most superficial of gluteus muscles; forms bulk of buttock mass; fibers are thick and coarse; important site of intramuscular injection (dorsal gluteal site); overlies large sciatic nerve; covers ischial tuberosity only when standing; when sitting, moves superiorly, leaving ischial tubersoity exposed in the subcutaneous postion
Gluteus maximus - Origin dorsal ilium, sacrum, and coccyx
Gluteus maximus - Insertion gluteal tuberosity of femur; iliotibial tract
Gluteus maximus - Action major extensor of thigh; complex, powerful, and most effective when thigh is flexed and force is necessary, as in rising from a forward flexed position and in thrusting the thigh posteriorly in climbing stairs and running; generally inactive during standing and walking; laterally rotates and abducts thigh
Gluteus maximus - Innervation inferior gluteal nerve (L5, S1, and S2)
Piriformis - Description pyramidal muscle located on posterior aspect of hip joint; inferior to gluteus minimu; issues from pelvis via greater sciatic notch
Piriformis - Origin anterolateral surface of sacrum (opposite greater sciatic notch)
Piriformis - Insertion superior border of greater trochanter of femur
Piriformis - Action rotates extended thigh laterally; since inserted above head of femur, can also assist in abduction of thigh when hip is flexed; stabilizes hip joint
Piriformis - Innervation S1 and S2, L5
Tibialis posterior - Description thick, flat muscle deep to soleus; placed between posterior flexors
Tibialis posterior - Origin extensive origin from superior tibia and fibula and interosseous membrane
Tibialis posterior - Insertion tendon passes behind medial malleolus and under arch of foot; inserts into several tarsals and metatarsals 2-4
Tibialis posterior - Action prime mover of foot inversion; plantar flexes foot; stabilizes medial longitudinal arch of foot (as during ice skating)
Tibialis posterior - Innervation tibial nerve (L4 and L5)
Fibularis (peroneus) longus - Description superficial lateral muscle; overlies fibula
Fibularis (peroneus) longus - Origin upper portion of lateral fibula
Fibularis (peroneus) longus - Insertion by long tendon that curves under foot to first metatarsal and medial cuneiform
Fibularis (peroneus) longus - Action plantar flexes and everts foot; may help keep foot flat on ground
Fibularis (peroneus) longus - Innervation superficial fibular nerve (L5-S2)
Gastrocnemius - Description superficial muscle of pair; two prominent bellies that form proximal curve of calf
Gastrocnemius - Origin by two heads from medial and lateral condyles of femur
Gastrocnemius - Insertion posterior calcaneus via calcaneal tendon
Gastrocnemius - Action plantar flexes foot when knee is extended; since it also crosses knee joint, it can flex knee when foot is dorsiflexed
Soleus - Description broad, flat muscle, deep to gastrocnemius on posterior surface of calf
Soleus - Origin extensive origin from superior tibia, fibula, and interosseous membrane
Soleus - Insersion posterior calcaneus via calcaneal tendon
Soleus - Action plantar flexes foot; important locomotor and postural muscle during walking, running, and dancing
Soleus - Innervation tibial nerve
Tibialis anterior - Description superficial muscle of anterior leg; laterally parallels sharp anterior margin of tibia
Tibialis anterior - Origin lateral condyle of upper 2/3 of tibial shat; interosseous membrane
Tibialis anterior - Insetion by tendon into inferior surface of medial cuneiform and first metatarsal bone
Tibialis anterior - Action prime move of dorsiflexion, inverts foot; assists in supporting medial longitudinal arch of foot
Tibialis anterior - Innervation deep fibular nerve (L4 and L5)
Vastus intermedius - Description obscurred by rectus femoris; lies between vastus lateralis and vastus medialis on anterior thigh
Vastus intermedius - Origin anteior and lateral surfaces of proximal femur shaft
Vastus intermedius - Insertion patella and tibial tuberosity via patellar ligament
Vastus intermedius - Action extemds knee
Vastus intermedius - Innervation femoral nerve
Tensor fasciae latae - Description enclosed between fascia layers of anterolateral aspect of thigh; functionally associated with medial rotators and flexors of thigh
Tensor fasciae latae - Origin anterior aspect of iliac crest and anterior superior iliac spine
Tensor fasciae latae - Insertion iliotibial tract
Tensor fasciae latae - Action flexes and abducts thigh (thus a synergist of the iliopsoas and gluteus medius and minimus muscles); rotates thigh medially; steadies the knee and trunk on thigh by making iliotibial tract taut
Tensor fasciae latae - Innervation superior gluteal nerve (L 4 and L5)
Rectus abdominis - Description medial superficial muscle pair; extend from pubis to rib cage; ensheathed by aponeuroses of lateral muscles; segmented by 3 tendinous intersections
Rectus abdominis - Origin pubic crest and symphysis
Rectus abdominis - Insertion xiphoid process and costal cartilages of ribs 5-7
Rectus abdominis - Action flex and rotate lumbar gegion of vertrebral column; fix and depress ribs, stabilize pelvis during walking , increase intra-abdominal pressure; used in sit-ups, curles
Rectus abdominis - Innervation intercostal nerves (T6 or T7-T12)
External oblique - Description largest and most superficial of the three lateral muscles; fibers run downward and medially (same direction outstretched fingers take when hands put into pants pockets); aponeurosis turns under inferiorly, forming inguinal ligament
External oblique - Origin by fleshy strips from outer surfaces of lower eight ribs
External oblique - Insertion most fibers insert anteriorly via a broad aponeurosis into linea alba; some into public crest and tubercle and iliac crest
External oblique - Action when pair contract simultaneously, aid rectus abdominis muscles in flexing vertebral column and in compressing abdominal wall and increasing intra-abdominal pressure; acting individually, aid muscles of back in trunk rotation and lateral flexion; used in oblique curls
External oblique - Innervation intercostal nerves (T7-T12)
Internal oblique - Description most fibers run upward and medially; however, the muscle fans so its inferior fibers run downward and medially
Internal oblique - Origin lumbar fascia, iliac crest, and inguinal ligament
Internal oblique - Insertion linea alba, pubic crest, last three or four ribs, and costal margin
Internal oblique - Innervation intercostal nerves (T7-T12) and L1
Biceps femoris - Description most lateral muscle of the group, arises from two head
Biceps femoris - Origin ischial tuberosity (long head); linea aspera and distal femure (short head)
Biceps femoris - Insertion common tendon passes downward and laterally (forming lateral border of popliteal fossa) to insert into head of fibula and lateral condyle of tibia
Biceps femoris - Action extends thigh and flexes knee; laterally rotates leg, especially when knee is flexed
Biceps femoris - Innervation sciatic nerve- tibial nerve to long head, common fibular nerve to short head (L5-S2)
Internal obliques - Action when pair contract simultaneously, aid rectus abdominis muscles in flexing vertebral column and in compressing abdominal wall and increasing intra-abdominal pressure; acting individually, aid muscles of back in trunk rotation and lateral flexion; used in oblique curls