Comprehensive Muscle Innervation Study Guide

Innervation of the Upper Limb: Shoulder and Scapular Regions

• Deltoid: Innervated by the axillary nerve.

• Teres minor: Innervated by the axillary nerve.

• Supraspinatus: Innervated by the suprascapular nerve.

• Infraspinatus: Innervated by the suprascapular nerve.

• Subscapularis: Innervated by both the upper and lower subscapular nerves.

• Teres major: Innervated by the lower subscapular nerve.

• Latissimus dorsi: Innervated by the thoracodorsal nerve.

• Trapezius: Innervated by the spinal accessory nerve ($CN XI$).

• Levator scapulae: Innervated by the dorsal scapular nerve, receiving assistance from the $C_3-C_4$ spinal nerves.

• Rhomboids: Innervated by the dorsal scapular nerve.

• Serratus anterior: Innervated by the long thoracic nerve.

• Pectoralis major: Innervated by both the medial and lateral pectoral nerves.

• Pectoralis minor: Innervated by the medial pectoral nerve.
  

Innervation of the Arm, Forearm, and Hand

• Anterior Arm (Brachium):
  

  • The muscles of the anterior compartment, consisting of the Biceps brachii, Brachialis, and Coracobrachialis, are all innervated by the musculocutaneous nerve.

• Posterior Arm (Brachium):
  

  • The muscles of the posterior compartment, including the Triceps brachii and the Anconeus, are innervated by the radial nerve.

• Forearm Flexors (Anterior Compartment):
  

  • The majority of the flexor muscles in the forearm are innervated by the median nerve.

  • Exceptions: The Flexor carpi ulnaris (FCU) and the medial half (medial side) of the Flexor digitorum profundus (FDP) are innervated by the ulnar nerve.

• Forearm Extensors (Posterior Compartment):
  

  • These muscles are supplied by the radial nerve or the posterior interosseous nerve.

• Hand Muscles:
  

  • LOAF Muscles: The first and second Lumbricals, Opponens pollicis, Abductor pollicis brevis, and Flexor pollicis brevis are innervated by the median nerve.

  • Remaining Intrinsic Muscles: All other intrinsic muscles of the hand are innervated by the ulnar nerve.
    

Innervation of the Lower Limb: Gluteal Region and Thigh

• Gluteus maximus: Innervated by the inferior gluteal nerve.

• Gluteus medius, Gluteus minimus, and Tensor fasciae latae (TFL): All three are innervated by the superior gluteal nerve.

• Anterior Thigh Compartment: The Quadriceps, Sartorius, and Iliacus are innervated by the femoral nerve.

• Adductor (Medial) Compartment of the Thigh: These muscles are innervated by the obturator nerve.

• Posterior Thigh (Hamstrings):
  

  • Generally innervated by the tibial division of the sciatic nerve.

  • Exception: The short head of the biceps femoris is innervated by the common fibular (peroneal) division of the sciatic nerve.
    

Innervation of the Lower Limb: Leg (Crus)

• Anterior Leg Compartment: Innervated by the deep fibular nerve.

• Lateral Leg Compartment: Innervated by the superficial fibular nerve.

• Posterior Leg Compartment: Innervated by the tibial nerve.
  

High-Yield Mnemonics and Summary Guides

• LOAF (Hand Muscles - Median Nerve):
  

  • L: Lumbricals $1-2$.

  • O: Opponens pollicis.

  • A: Abductor pollicis brevis.

  • F: Flexor pollicis brevis.

• SITS (Rotator Cuff Muscles):
  

  • S: Supraspinatus.

  • I: Infraspinatus.

  • T: Teres minor.

  • S: Subscapularis.

• Compartmental Nerve Summary:
  

  • Anterior Arm: Musculocutaneous nerve.

  • Posterior Arm: Radial nerve.

  • Anterior Thigh: Femoral nerve.

  • Medial Thigh: Obturator nerve.

  • Posterior Thigh: Sciatic nerve (Specifically the tibial division).

  • Anterior Leg: Deep fibular nerve.

  • Lateral Leg: Superficial fibular nerve.

  • Posterior Leg: Tibial nerve.