Upper Limb Muscles
Pectoral Region
Pectoralis Major
Origin: medial 2/3 clavicle + sternum + upper 6 costal cartilages
Insert: Lateral lip of bicipital groove
Insert: Lateral lip of bicipital groove
Medial + lateral pectoral nn.
Adduction + medial rotation + flexion of arm
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Pectoralis Minor
Origin: ribs 3, 4, 5 · Insert: Coracoid process of scapula
Medial pectoral n.
Protraction of scapula + depresses shoulder
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Serratus Anterior
Origin: lateral ribs 1–8 · Insert: medial border of scapula
Long thoracic nerve
Protraction + upward rotation of scapula
⚠️ Paralysis → Winging of Scapula
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Back Muscles
Trapezius
Origin: occiput + C7–T12 · Insert: lateral clavicle + acromion + scapular spine
Spinal accessory n. (CN XI)
Elevates shoulder
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Latissimus Dorsi
Origin: T7–L5 + iliac crest · Insert: floor of bicipital groove (medial lip)
Thoracodorsal nerve
Adduction + medial rotation + extension of arm
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Rhomboids Major & Minor
Origin: C7–T5 · Insert: medial border of scapula
Dorsal scapular nerve
Retraction + elevation of scapula
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Levator Scapulae
Origin: C1–C4 transverse processes · Insert: superior angle of scapula
Dorsal scapular nerve
Elevates scapula
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Shoulder (Scapula → Humerus)
Deltoid
Origin: lateral clavicle + acromion + scapular spine · Insert: deltoid tuberosity
Axillary nerve
Middle fibers: abduction 15–90°
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Rotator Cuff = SITS — Supraspinatus · Infraspinatus · Teres minor · Subscapularis
Supraspinatus [S]
Origin: supraspinous fossa · Insert: greater tubercle (superior facet)
Suprascapular nerve
Initiates abduction 0–15°
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Infraspinatus [I]
Origin: infraspinous fossa · Insert: greater tubercle (middle facet)
Suprascapular nerve
Lateral rotation of arm
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Teres Minor [T]
Origin: lateral border of scapula · Insert: greater tubercle (inferior facet)
Axillary nerve
Lateral rotation of arm
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Subscapularis [S]
Origin: subscapular fossa · Insert: lesser tubercle of humerus
Upper + lower subscapular nn.
Adduction + medial rotation of arm
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Teres Major
Origin: lower lateral border of scapula · Insert: medial lip of bicipital groove
Lower subscapular nerve
Adduction + medial rotation + extension
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Arm — Anterior "BBC" (all → Musculocutaneous n.)
Coracobrachialis [C]
Origin: coracoid process · Insert: middle medial humerus
Musculocutaneous nerve
Flexion of arm
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Biceps Brachii [B]
Short head: coracoid · Long head: supraglenoid tubercle (intracapsular ⚠️)
Musculocutaneous nerve
Flexion arm + elbow + supination of semi-flexed forearm
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Brachialis [B]
Origin: lower anterior humerus · Insert: coronoid process + ulnar tuberosity
Musculocutaneous n. (+ radial n. for lateral fibers)
MAIN flexor of forearm
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Arm — Posterior (→ Radial n.)
Triceps Brachii (Long, Lateral, Medial heads)
Insert: olecranon of ulna
Radial nerve
MAIN extensor of forearm
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Anterior Forearm — Flexors
⚠️ All → Median nerve EXCEPT Flexor carpi ulnaris → Ulnar nerve
Pronator Teres
Origin: medial epicondyle + coronoid · Insert: lateral radius (middle)
Median nerve
Pronation of forearm
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Flexor Carpi Radialis
Origin: medial epicondyle · Insert: base of 2nd metacarpal
Median nerve
Wrist flexion + abduction of hand
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Flexor Carpi Ulnaris ⚠️
Origin: medial epicondyle + olecranon · Insert: pisiform + hamate + 5th metacarpal
ULNAR nerve (exception!)
Wrist flexion + adduction of hand
⚠️
Flexor Digitorum Superficialis
Insert: middle phalanges of fingers 2–5
Median nerve
Flexes medial 4 fingers + wrist
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Pronator Quadratus
Origin: distal ulna · Insert: distal radius
Median nerve
MAIN pronator of forearm
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Posterior/Lateral Forearm — Extensors
Lateral compartment → Radial n. · Posterior compartment → Deep branch of radial n.
Brachioradialis
Origin: lateral supracondylar ridge · Insert: styloid process of radius
Radial nerve
Elbow flexion in midprone position
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Extensor Digitorum
Origin: lateral epicondyle · Insert: dorsal expansions fingers 2–5
Deep branch of radial nerve
Extends medial 4 fingers + wrist
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Extensor Carpi Ulnaris
Origin: lateral epicondyle · Insert: base of 5th metacarpal
Deep branch of radial nerve
Wrist extension + adduction
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Hand Muscles (20 total)
⚠️ ALL → Ulnar nerve EXCEPT Thenar + 1st & 2nd Lumbricals → Median nerve
| Group | Muscles | Nerve | Action |
|---|---|---|---|
| Thenar | Abd. pollicis brevis · Flex. pollicis brevis · Opponens pollicis | Median | Thumb movements |
| Adductor pollicis | Adductor pollicis | Ulnar | Adducts thumb |
| Hypothenar | Abd. digiti minimi · Flex. digiti minimi · Opponens digiti minimi | Ulnar | Little finger |
| Lumbricals 1&2 | 1st & 2nd lumbrical | Median | Writing: flex MCP + extend IP |
| Lumbricals 3&4 | 3rd & 4th lumbrical | Ulnar | |
| Palmar interossei (4) | All 4 | Ulnar | PAD = ADduction toward middle |
| Dorsal interossei (4) | All 4 | Ulnar | DAB = ABduction from middle |
⚡ Quick-fire — Upper Limb
Serratus anterior paralysisWinging of scapula
Abduction 0–15°Supraspinatus
Abduction 15–90°Deltoid
Long head of bicepsINTRAcapsular
Main forearm flexorBrachialis
Main forearm pronatorPronator quadratus
Flexor carpi ulnaris nerveUlnar (exception!)
ALL hand muscles nerveUlnar (except thenar + 1st/2nd lumbr = Median)
PAD / DABPalmar=ADduction / Dorsal=ABduction
Lower Limb Muscles
| Anterior | Medial | Posterior | |
|---|---|---|---|
| Muscles | Quadriceps + Iliopsoas + Sartorius + Pectineus | Adductors + Gracilis | Hamstrings |
| Movement | Flexion of thigh, Extension of leg | Adduction of thigh | Extension of thigh, Flexion of leg |
| Nerve | Femoral n. | Obturator n. | Sciatic n. |
Anterior Compartment
All → Femoral nerve EXCEPT Psoas major → L1, 2, 3
Iliopsoas
Iliacus (iliac fossa) + Psoas major (T12–L5) · Insert: lesser trochanter
Femoral n. + L1,2,3 (psoas)
Flexes thigh
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Sartorius — longest muscle in the body
Origin: ASIS · Insert: upper medial tibia (pes anserinus)
Femoral nerve
Tailor position: flexion + abduction + lateral rotation of thigh
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Quadriceps Femoris (4 heads)
Insert: patella → tibial tuberosity via patellar ligament
Femoral nerve
Extends knee · Rectus femoris also flexes thigh
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Pectineus
Origin: superior pubic ramus · Insert: linea aspera of femur
Femoral nerve
Flexes + adducts thigh
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Medial Compartment — Adductors
All → Obturator nerve
Adductors (Longus, Brevis, Magnus)
Origin: pubis · Insert: linea aspera of femur
Obturator nerve
Adducts thigh
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Gracilis
Origin: pubis · Insert: upper medial tibia (pes anserinus)
Obturator nerve
Adducts thigh + flexes + medially rotates leg
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Posterior Compartment — Hamstrings
⚠️ All → Tibial branch of sciatic n. EXCEPT short head of biceps femoris → Common peroneal branch
Biceps Femoris ⚠️
Long head: ischial tuberosity · Short head: linea aspera · Insert: head of fibula
Long: Tibial n.Short: Common peroneal ⚠️
Extends hip + flexes knee + lateral rotation
⚠️
Semitendinosus
Origin: ischial tuberosity · Insert: upper medial tibia (pes anserinus)
Tibial branch of sciatic n.
Extends hip + flexes knee + medial rotation
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Semimembranosus
Origin: ischial tuberosity · Insert: posterior medial tibial condyle
Tibial branch of sciatic n.
Extends hip + flexes knee + medial rotation
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Gluteal Region
⚠️ All → Superior gluteal nerve EXCEPT Gluteus maximus → Inferior gluteal nerve
Gluteus Maximus ⚠️
Origin: ilium + sacrum + coccyx · Insert: gluteal tuberosity + iliotibial tract
Inferior gluteal nerve ⚠️
Extension + lateral rotation of thigh
⚠️
Gluteus Medius
Origin: outer ilium · Insert: greater trochanter of femur
Superior gluteal nerve
Abduction + prevents pelvic tilt
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Gluteus Minimus
Origin: outer ilium · Insert: greater trochanter (anterior surface)
Superior gluteal nerve
Abduction + prevents pelvic tilt
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IM injection → Upper lateral quadrant of gluteal region (avoids sciatic nerve!)
6 Lateral Rotators of Thigh
| Muscle | Nerve |
|---|---|
| Piriformis | S1, S2 |
| Obturator internus | Nerve to obturator internus |
| Superior gemellus | Nerve to obturator internus |
| Quadratus femoris | Nerve to quadratus femoris |
| Inferior gemellus | Nerve to quadratus femoris |
| Obturator externus | Obturator nerve |
Leg Compartments
Peroneus = Eversion · Tibialis = Inversion
Tibialis Anterior
Origin: lateral tibia · Insert: medial cuneiform + 1st metatarsal
Deep fibular (peroneal) nerve
Dorsiflexion + inversion
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Extensor Hallucis Longus
Origin: middle fibula · Insert: distal phalanx of big toe
Deep fibular (peroneal) nerve
Dorsiflexion + extends big toe
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Extensor Digitorum Longus
Insert: dorsal expansions toes 2–5
Deep fibular (peroneal) nerve
Dorsiflexion + extends 4 toes
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Fibularis (Peroneus) Longus & Brevis
Lateral compartment
Superficial fibular (peroneal) nerve
Plantarflexion + eversion of foot
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Gastrocnemius + Soleus + Plantaris
Insert: all via Achilles tendon → calcaneus
Tibial nerve
Plantarflexion · Gastroc also weakly flexes knee
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Popliteus
Origin: lateral femoral condyle · Insert: posterior tibia
Tibial nerve
Flexes + UNLOCKS the knee
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Tibialis Posterior
Origin: posterior tibia + fibula · Insert: navicular + cuneiforms + cuboid
Tibial nerve
Plantarflexion + inversion
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Flexor Hallucis Longus
Origin: posterior fibula · Insert: distal phalanx big toe
Tibial nerve
Plantarflexion + flexes big toe
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Flexor Digitorum Longus
Origin: posterior tibia · Insert: distal phalanges toes 2–5
Tibial nerve
Plantarflexion + flexes 4 toes
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Sole of the Foot — 4 Layers
⚠️ All → Lateral plantar n. EXCEPT Abd hallucis + FDB + FHB + 1st lumbrical → Medial plantar n.
| Layer | Contents |
|---|---|
| 1st (superficial) | Abductor hallucis · Flexor digitorum brevis · Abductor digiti minimi |
| 2nd | Quadratus plantae · Lumbricals (4) · FDL tendon · FHL tendon |
| 3rd | Flexor hallucis brevis · Adductor hallucis · Flexor digiti minimi brevis |
| 4th (deep) | Interossei (4 dorsal + 3 plantar) · Peroneus longus tendon · Tibialis posterior tendon |
2nd and 4th layers contain TENDONS from leg muscles — not intrinsic foot muscles
⚡ Quick-fire — Lower Limb
Longest muscle in bodySartorius
Only quad head crossing hipRectus femoris (also flexes thigh)
Short head of biceps femorisCommon peroneal (not tibial!)
Gluteus maximus nerveInferior gluteal
Gluteus medius + minimusSuperior gluteal
IM injection siteUpper lateral quadrant
Anterior leg nerveDeep fibular/peroneal
Lateral leg nerveSuperficial fibular/peroneal
Posterior leg nerveTibial
Popliteus actionFlexes + unlocks knee
Peroneus / TibialisEversion / Inversion
Medial plantar nerve (foot)Abd hallucis, FDB, FHB, 1st lumbrical