Muscles Reference Guide: Upper and Lower Limb

Comprehensive flashcards covering origin, insertion, innervation, and action for muscles of the anterior and posterior forearm, intrinsic hand, gluteal region, anterior thigh, and medial thigh from Lectures 12–21.

Pronator teres

An anterior forearm muscle (superficial layer) originating from the medial epicondyle of humerus and coronoid process of ulna, inserting into the lateral surface of radius (middle), innervated by the median nerve, and acting to pronate the forearm and assist elbow flexion.

Flexor carpi radialis

A superficial anterior forearm muscle originating from the medial epicondyle of humerus (common flexor origin), inserting into the bases of 2nd–3rd metacarpals, innervated by the median nerve, and acting to flex and abduct the wrist.

Palmaris longus

A superficial anterior forearm muscle originating from the medial epicondyle of humerus (common flexor origin), inserting into the palmar aponeurosis (and flexor retinaculum), innervated by the median nerve, and acting to flex the wrist and tense the palmar aponeurosis.

Flexor carpi ulnaris

A superficial anterior forearm muscle originating from the medial epicondyle of humerus, olecranon, and posterior border of ulna, inserting into the pisiform, innervated by the ulnar nerve, and acting to flex and adduct the wrist.

Flexor digitorum superficialis

An intermediate anterior forearm muscle originating from the medial epicondyle of humerus, coronoid process of ulna, and radius, inserting into the sides of middle phalanges of digits 2–5, innervated by the median nerve, and acting to flex PIP joints and assist MCP and wrist flexion.

Flexor digitorum profundus

A deep anterior forearm muscle originating from the proximal anterior ulna and interosseous membrane, inserting into the bases of distal phalanges of digits 2–5, innervated by the anterior interosseous nerve (median) for its lateral half and the ulnar nerve for its medial half, and acting to flex DIP joints and assist MCP and wrist flexion.

Flexor pollicis longus

A deep anterior forearm muscle originating from the anterior surface of radius and interosseous membrane, inserting into the base of distal phalanx of thumb, innervated by the anterior interosseous nerve (median), and acting to flex the thumb IP joint and assist thumb MCP flexion.

Pronator quadratus

A deep anterior forearm muscle originating from the distal anterior ulna, inserting into the distal anterior radius, innervated by the anterior interosseous nerve (median), and acting to pronate the forearm.

Brachioradialis

A superficial posterior forearm muscle originating from the proximal $\frac{2}{3}$ of lateral supracondylar ridge of humerus, inserting into the lateral distal radius proximal to styloid process, innervated by the radial nerve, and acting to flex the elbow and return forearm to mid-position.

Extensor carpi radialis longus

A superficial posterior forearm muscle originating from the lateral supracondylar ridge of humerus, inserting into the base of 2nd metacarpal, innervated by the radial nerve, and acting to extend and abduct the wrist.

Extensor carpi radialis brevis

A superficial posterior forearm muscle originating from the lateral epicondyle of humerus (common extensor origin), inserting into the base of 3rd metacarpal, innervated by the deep branch of radial nerve / posterior interosseous nerve, and acting to extend and abduct the wrist.

Extensor digitorum

A superficial posterior forearm muscle originating from the lateral epicondyle of humerus (common extensor origin), inserting into the extensor expansions of medial 4 fingers (digits 2–5), innervated by the posterior interosseous nerve, and acting to extend the wrist, MCP, and IP joints (extends fingers).

Extensor digiti minimi

A superficial posterior forearm muscle originating from the lateral epicondyle of humerus (common extensor origin), inserting into the extensor expansion of 5th finger (middle and distal phalanges), innervated by the posterior interosseous nerve, and acting to extend the little finger and assist wrist extension.

Extensor carpi ulnaris

A superficial posterior forearm muscle originating from the lateral epicondyle of humerus (common extensor origin) and posterior border of ulna, inserting into the base of 5th metacarpal, innervated by the posterior interosseous nerve, and acting to extend and adduct the wrist.

Anconeus

A superficial posterior forearm muscle originating from the posterior aspect of lateral epicondyle of humerus, inserting into the lateral olecranon and proximal posterior surface of ulna, innervated by the radial nerve, and acting to assist elbow extension and stabilize the elbow joint.

Supinator

A deep posterior forearm muscle originating from the lateral epicondyle of humerus and supinator crest of ulna, inserting into the proximal shaft of radius, innervated by the posterior interosseous nerve, and acting to supinate the forearm.

Abductor pollicis longus

A deep posterior forearm muscle originating from the posterior surfaces of radius and ulna, inserting into the base of 1st metacarpal, innervated by the posterior interosseous nerve, and acting to abduct the thumb and assist thumb extension at the CMC joint.

Extensor pollicis brevis

A deep posterior forearm muscle originating from the posterior surface of radius and interosseous membrane, inserting into the base of proximal phalanx of thumb, innervated by the posterior interosseous nerve, and acting to extend the thumb at the MCP joint.

Extensor pollicis longus

A deep posterior forearm muscle originating from the posterior surface of ulna and interosseous membrane, inserting into the base of distal phalanx of thumb, innervated by the posterior interosseous nerve, and acting to extend the thumb at the IP joint.

Extensor indicis

A deep posterior forearm muscle originating from the posterior surface of ulna and interosseous membrane, inserting into the extensor expansion of index finger, innervated by the posterior interosseous nerve, and acting to extend the index finger.

Abductor pollicis brevis

A thenar muscle of the hand originating from the flexor retinaculum, scaphoid, and trapezium, inserting into the base of proximal phalanx of thumb, innervated by the median nerve (recurrent branch), and acting to abduct the thumb.

Flexor pollicis brevis

A thenar muscle of the hand originating from the flexor retinaculum and trapezium, inserting into the base of proximal phalanx of thumb, innervated by the median nerve (and deep branch of ulnar nerve), and acting to flex the thumb.

Opponens pollicis

A thenar muscle of the hand originating from the flexor retinaculum (transverse carpal ligament) and trapezium, inserting into the lateral side of 1st metacarpal, innervated by the median nerve (recurrent branch), and acting to oppose the thumb.

Adductor pollicis

An adductor compartment muscle of the hand originating via two heads from the capitate, trapezoid, and metacarpals (2nd and 3rd), inserting into the base of proximal phalanx of thumb, innervated by the ulnar nerve (deep branch), and acting to adduct the thumb toward the palm.

Abductor digiti minimi (hand)

A hypothenar muscle originating from the pisiform (and flexor retinaculum), inserting into the base of proximal phalanx of 5th digit (little finger), innervated by the ulnar nerve (deep branch), and acting to abduct the little finger.

Flexor digiti minimi brevis

A hypothenar muscle originating from the flexor retinaculum and hook of hamate, inserting into the base of proximal phalanx of 5th digit (little finger), innervated by the ulnar nerve (deep branch), and acting to flex the little finger.

Opponens digiti minimi

A hypothenar muscle originating from the flexor retinaculum and hook of hamate, inserting into the medial border of 5th metacarpal / proximal phalanx, innervated by the ulnar nerve (deep branch), and acting to oppose the little finger.

Palmaris brevis

A hypothenar muscle originating from the palmar aponeurosis and flexor retinaculum, inserting into the skin of medial border of palm (hypothenar skin), innervated by the ulnar nerve (superficial branch), and acting to wrinkle hypothenar skin.

Lumbricals (4 muscles)

Intrinsic central hand muscles originating from the flexor digitorum profundus tendons, inserting into extensor expansions of digits 2–5, innervated by the median nerve (1st & 2nd) and deep branch of ulnar nerve (3rd & 4th), which flex MCP joints and extend IP joints.

Dorsal interossei (4 muscles)

Intrinsic hand muscles originating from adjacent sides of metacarpals, inserting into extensor expansions and proximal phalanges of digits, innervated by the deep branch of ulnar nerve, which abduct fingers away from middle finger, flex MCP joints, and extend IP joints.

Palmar interossei (3 muscles)

Intrinsic hand muscles originating from metacarpals of respective digits, inserting into extensor expansions and proximal phalanges of digits, innervated by the ulnar nerve (deep branch), which adduct fingers toward middle finger, flex MCP joints, and extend IP joints.

Gluteus maximus

A superficial gluteal muscle originating from the posterior surface of ilium (posterior to posterior gluteal line), dorsal surface of sacrum, coccyx, and sacrotuberous ligament; inserting via superficial fibers to the iliotibial tract and deep fibers to the gluteal tuberosity of femur; innervated by the inferior gluteal nerve ($L5\text{--}S2$); producing powerful extension and lateral rotation of thigh, adduction assistance via lower fibers, and stabilization of hip and extended knee.

Gluteus medius

A superficial gluteal muscle originating from the external surface of ilium (from iliac crest), inserting into the lateral surface of greater trochanter of femur, innervated by the superior gluteal nerve ($L4\text{--}S1$), and acting to abduct the thigh, medially rotate thigh via anterior fibers, and stabilize the pelvis.

Gluteus minimus

A superficial gluteal muscle originating from the external surface of ilium, inserting into the anterior surface of greater trochanter of femur, innervated by the superior gluteal nerve ($L4\text{--}S1$), and acting to abduct and medially rotate the thigh and stabilize the pelvis.

Tensor fasciae latae

A superficial gluteal muscle originating from the anterior part of iliac crest (outer lip) and ASIS, inserting into the iliotibial tract (attaching inferiorly to lateral tibial condyle), innervated by the superior gluteal nerve ($L4\text{--}S1$), and acting in thigh abduction, medial rotation, and stabilization of hip and extended knee via the IT tract.

Piriformis

A deep gluteal muscle originating from the anterior surface of sacrum, inserting into the top of greater trochanter of femur, innervated by the nerve to piriformis ($S1\text{--}S2$), and acting to laterally rotate the thigh.

Superior gemellus

A deep gluteal muscle originating from the ischial spine, inserting into the obturator internus tendon, innervated by the nerve to obturator internus ($L5\text{--}S1$ / $L5\text{--}S2$), and acting to laterally rotate the thigh.

Obturator internus

A deep gluteal muscle originating from the pelvic surface of obturator membrane, inserting into the medial surface of greater trochanter of femur, innervated by the nerve to obturator internus ($L5\text{--}S2$), and acting to laterally rotate the extended thigh.

Inferior gemellus

A deep gluteal muscle originating from the ischial tuberosity, inserting into the obturator internus tendon, innervated by the nerve to quadratus femoris ($L4\text{--}S1$), and acting to laterally rotate the thigh.

Quadratus femoris

A deep gluteal muscle originating from the ischial tuberosity, inserting into the quadrate tubercle of femur, innervated by the nerve to quadratus femoris ($L4\text{--}S1$), and acting to laterally rotate the thigh.

Sartorius

An anterior thigh muscle originating from the anterior superior iliac spine (ASIS), inserting into the superior medial surface of proximal tibia (pes anserinus), innervated by the femoral nerve ($L2\text{--}L3$), and acting to flex, abduct, and laterally rotate the hip, and flex the knee.

Rectus femoris

A quadriceps muscle originating from the anterior inferior iliac spine (AIIS) and ilium superior to acetabulum, inserting into the base of patella via quadriceps tendon and tibial tuberosity via patellar ligament, innervated by the femoral nerve ($L2\text{--}L4$), and acting to extend the knee and flex the hip.

Vastus lateralis

A quadriceps muscle originating from the greater trochanter, gluteal tuberosity, and linea aspera of femur, inserting into the base of patella via quadriceps tendon and tibial tuberosity via patellar ligament, innervated by the femoral nerve ($L2\text{--}L4$), and acting to extend the knee.

Vastus medialis

A quadriceps muscle originating from the intertrochanteric line and medial lip of linea aspera of femur, inserting into the base of patella via quadriceps tendon and tibial tuberosity via patellar ligament, innervated by the femoral nerve ($L2\text{--}L4$) via nerve to vastus medialis, and acting to extend the knee.

Vastus intermedius

A quadriceps muscle originating from the anterior and lateral surfaces of femoral shaft, inserting into the base of patella via quadriceps tendon and tibial tuberosity via patellar ligament, innervated by the femoral nerve ($L2\text{--}L4$), and acting to extend the knee.

Articularis genus

An anterior thigh muscle originating from the distal anterior surface of femur, inserting into the suprapatellar synovial membrane and bursa, innervated by the femoral nerve, and acting to pull (retract) the synovial membrane superiorly during knee extension.

Psoas major

An iliopsoas group muscle originating from the bodies and intervertebral discs of $T12\text{--}L5$ vertebrae, inserting into the lesser trochanter of femur via iliopsoas tendon, innervated by anterior rami of $L1\text{--}L3$ spinal nerves, and acting to flex the hip.

Iliacus

An iliopsoas group muscle originating from the iliac fossa and iliac crest, inserting into the lesser trochanter of femur via iliopsoas tendon, innervated by the femoral nerve ($L2\text{--}L4$), and acting to flex the hip.

Pectineus

A medial thigh muscle originating from the superior pubic ramus (pubis), inserting into the pectineal line of femur, innervated by the femoral nerve ($L2\text{--}L3$), and acting to adduct and flex the thigh.

Adductor longus

A medial thigh muscle originating from the body of pubis inferior to pubic crest, inserting into the middle third of linea aspera of femur, innervated by the obturator nerve ($L2\text{--}L4$), and acting to adduct the thigh.

Adductor brevis

A medial thigh muscle originating from the body and inferior ramus of pubis, inserting into the pectineal line and proximal linea aspera of femur, innervated by the obturator nerve, and acting to adduct the thigh.

Gracilis

A medial thigh muscle originating from the body and inferior ramus of pubis, inserting into the medial surface of proximal tibia (pes anserinus — shared with sartorius and semitendinosus), innervated by the obturator nerve, and acting to adduct the thigh and flex the leg (knee flexion).

Adductor magnus

A medial thigh muscle consisting of two parts: an adductor part originating from ischiopubic rami, inserting on gluteal tuberosity, linea aspera, and medial supracondylar line, innervated by the posterior division of obturator nerve ($L2\text{--}L4$), which adducts thigh; and a hamstring part originating from ischial tuberosity, inserting on the adductor tubercle of femur, innervated by the tibial division of sciatic nerve ($L4$), which adducts and extends thigh.

Obturator externus

A medial thigh muscle originating from the external surface of obturator membrane (and margins of obturator foramen), inserting into the trochanteric fossa of femur, innervated by the obturator nerve, and acting to laterally rotate the thigh.