Arm Muscle Function and Innervation

Question 1

Arm Muscle Compartments
muscles
innervation
function

Answer 1

1. Anterior Compartment:
   Muscles: Coracobrachialis, Biceps brachii, Brachialis.
   Innervation: Musculocutaneous nerve, radial nerve (partial).
   Function: Flexion, supination.
2. Posterior Compartment:
   Muscles: Triceps brachii.
   Innervation: Radial nerve.
   Function: Extension.

Question 2

Coracobrachialis Muscle
origin
insertion
function
innervation
key fact

Answer 2

Origin: Coracoid process.
Insertion: Medial shaft of humerus.
Function: Flexion and adduction of the shoulder.
Innervation: Musculocutaneous nerve.
Key Fact: Penetrated by musculocutaneous nerve; passes through axilla.

Question 3

Biceps Brachii Muscle
heads
insertion
function
innervation
key fact

Answer 3

Heads: Short head (coracoid process), Long head (supraglenoid tubercle).
Insertion: Radial tuberosity and bicipital aponeurosis.
Function: Flexion (elbow), supination (forearm).
Innervation: Musculocutaneous nerve.
Key Fact: Long head tendon passes through glenohumeral joint and intertubercular sulcus.

Question 4

Brachialis Muscle
origin
insertion
function
innervation

Answer 4

Origin: Anterior surface of humerus.
Insertion: Ulnar tuberosity and coronoid process.
Function: Primary forearm flexor (at the elbow joint).
Innervation: Musculocutaneous nerve.

Question 5

Triceps Brachii Muscle
heads
insertion
function
innervation

Answer 5

Heads:
1. Long head (infraglenoid tubercle of scapula).
2. Medial head (posterior humerus, below radial groove).
3. Lateral head (posterior humerus, above radial groove).
Insertion: Olecranon process of ulna.
Function: Extension of elbow.
Innervation: Radial nerve.

Question 6

Arm Muscle Function Summary
anterior & posterior compartments

Answer 6

Anterior Compartment:
Flexion (shoulder/elbow) and supination (forearm).

Posterior Compartment:
Extension (elbow).

Question 7

tendon of the Biceps Brachii (Long Head)
passes through ___ joint
runs through ___ sulcus
stabilizes ___ joint

Answer 7

Passes through the glenohumeral joint (superior to humeral head).
Runs through the intertubercular sulcus.
Stabilizes shoulder joint.

Question 8

Biceps Tendon Rupture (Long Head)
cause
sx
tx

Answer 8

Cause: Heavy lifting, overuse, or trauma.
Symptoms: “Popeye sign,” pain, weak elbow flexion and forearm supination.
Treatment: Conservative (rest) or surgical repai

Question 9

Triceps Brachii Tendon Rupture
cause
sx
risk

Answer 9

Cause: Trauma or overuse.
Symptoms: Weak elbow extension, visible gap above olecranon process.
Risk Factor: Steroid use or chronic overuse.

Question 10

Radial Nerve Injury in the Arm
cause
sx
muscles affected

Answer 10

Cause: Midshaft humerus fracture or prolonged compression (“Saturday night palsy”).
Symptoms: Wrist drop, weak extension (elbow, wrist, fingers), sensory loss on dorsal hand.
Muscles Affected: Triceps brachii (partial), wrist and finger extensors

Question 11

Compartment Syndrome of the Arm
caise
sx
tx

Answer 11

Cause: Trauma, fracture, or hemorrhage increasing pressure.
Symptoms: Pain, swelling, reduced pulses, weakness in arm muscles.
Treatment: Fasciotomy to relieve pressure.

Question 12

Brachialis Muscle in Elbow Dislocation
relevance
sx
tx

Answer 12

Relevance: Often strained or torn in posterior elbow dislocations.
Symptoms: Pain and reduced elbow flexion.
Treatment: Reduction of dislocation and physical therapy.

Question 13

Humeral Fractures and Nerve Injuries

Answer 13

Midshaft fracture: Radial nerve → Wrist drop.
Surgical neck fracture: Axillary nerve → Weak shoulder abduction.
Supracondylar fracture: Median nerve → Weak wrist/finger flexion.

Question 14

Biceps Reflex Testing (C5-C6)
test
normal response
clinical use

Answer 14

Test: Tap biceps tendon with reflex hammer.
Normal Response: Elbow flexion.
Clinical Use: Assess function of musculocutaneous nerve and C5-C6 spinal roots.

Question 15

Triceps Reflex Testing (C7)
test
normal response
clinical use

Answer 15

Test: Tap triceps tendon above olecranon process.
Normal Response: Elbow extension.
Clinical Use: Assess function of radial nerve and C7 spinal root

Question 16

Golfer’s Elbow vs. Tennis Elbow
actual name
affects which muscles and causes pain near what structure

Answer 16

Golfer’s Elbow (Medial Epicondylitis): Affects flexor muscles. Pain near medial epicondyle.
Tennis Elbow (Lateral Epicondylitis): Affects extensor muscles. Pain near lateral epicondyle.