Anatomy Forearm posterior compartment

How many muscle layers are in the posterior forearm compartment?

Superficial level = 7 muscles

• Radial side = 3 muscles

• Posterior side = 4 muscles

Deep level = 5 muscles

All posterior forearm muscles are innervated by the what nerve?

Radial nerve

Which superficial posterior forearm muscles are on the radial (lateral) side?

• Brachioradialis

• Extensor Carpi Radialis Longus (ECRL)

• Extensor Carpi Radialis Brevis (ECRB)

Which superficial posterior forearm muscles are on the posterior side?

• Extensor Digitorum

• Extensor Digiti Minimi

• Extensor Carpi Ulnaris

• Anconeus

Most posterior superficial muscles have an origin from what muscle?

Lateral Epicondyle of humerus

Most posterior superficial muscles have the same origin EXPECT?

brachioradialis

extensor carpi radialis longus

Brachioradialis ( most superificial/ proximal) Origin

Proximal lateral supraepicondylar ridge of humerus

Brachioradialis Insertion

Radial styloid process of radius

Brachioradialis Innervation

Radial nerve (C5–C6)

Brachioradialis Action

Flexes elbow when forearm is mid-pronated (Accessory elbow flexor)

Extensor Carpi Radialis Longus ( next superficial middle) Origin

Distal lateral supraepicondylar ridge of humerus

Extensor Carpi Radialis Longus Insertion

Base of metacarpal II

Extensor Carpi Radialis Longus Innervation

Radial nerve (C6–C7)

Extensor Carpi Radialis Longus Action

Extend and ABD wrist

Extensor Carpi Radialis Brevis (deepest one) Origin?

Lateral epicondyle of humerus

Extensor Carpi Radialis Brevis insertion

base of metacarpal II and III

Extensor Carpi Radialis Brevis innervation

Radial nerve (C7- C8)

Extensor Carpi Radialis Brevis Action

Extend and ABD wrist

Extensor Carpi Radialis Brevis is deep to what muscle?

Deep to extensor carpi radialis longus

Label cross-section of middle forearm

• Brachioradialis

• Extensor Carpi Radialis Longus

• Extensor Carpi Radialis Brevis

Extensor Digitorum Origin

Lateral epicondyle of humerus

Extensor Digitorum Insertion

4 tendons: EXTENSOR HOOD of bases of middle and distal phalanges of index, middle, ring, and little fingers

Extensor Digitorum Innervation

Radial nerve (POSTERIOR INTEROSSEOUS NERVE, C7-C8)

Extensor Digitorum Action

• Extend wrist

• Extend MCP, PIP, DIP joints of the 4 fingers

What is Extensor Hood?

• Triangular, copper on phalanges

• Attached to all 4 fingers

Extensor Digiti Minimi Origin

(Little finger)

Lateral epicondyle of humerus

Extensor Digiti Minimi Insertion

EXTENSOR HOOD of little finger

Extensor Digiti Minimi Innervation

radial nerve ( POSTERIOR INTEROSSEOUS NERVE, C7-C8)

Extensor Digiti Minimi Action

Extend MCP, PIP and DIP joints of the little finger

Extensor Carpi Ulnaris Origin

• lateral epicondyle of humerus

• posterior boarder of ulna

Extensor Carpi Ulnaris Insertion

base of metacarpal V

Extensor Carpi Ulnaris Innervation

radial nerve ( POSTERIOR INTEROSSEOUS NERVE, C7-C8)

Extensor Carpi Ulnaris Action

Extend and ADD wrist

Anconeus Origin

(cone shaped)

lateral epicondyle of humerus

Anconeus Insertion

olecranon and posterior surface of ulnar

Anconeus Innervation

radial nerve (C6-C8)

Anconeus Action

• accessory elbow extensor

• Stabilize ulna during pronation

Cross Section of middle forearm including posterior side of superficial muscles

• Brachioradialis

• Extensor Carpi Radialis Longus

• Extensor Carpi Radialis Brevis

• Extensor Digitorium

• Extensor Digit Minimi

• Extensor Carpi Ulnaris

What are the deep posterior forearm muscles?

• Supinator

• ABDuctor Pollicis Longus

• Extensor Pollicis Brevis

• Extensor Pollicis Longus

• Extensor Indicis

What do all posterior deep muscles have in common?

Origin from Posterior Surfaces of Radius, Ulna, and Interosseous Membrane

All deep posterior muscles have the same origin EXPECT what muscle?

Supinator

Supinator Origin

• Humeral (superficial) head: lateral EPIcondyle of humerus

• Ulnar (deep) head: SUPINATOR CREST of ulna

Supinator Insertion

anterior oblique line of radius

WRAPS AROUND RADIUS

Supinator Innervation

Radial nerve ( POSTERIOR INTEROSSEOUS NERVE, C6-C7)

Supinator Action

supinate forearm

ABductor Pollicis Longus Origin

posterior surfaces of radius, ulnar, and interosseous membrane

ABductor Pollicis Longus Insertion

base of metacarpal I (lateral side)

ABductor Pollicis Longus Innervation

Radial nerve ( POSTERIOR INTEROSSEOUS NERVE, C7-C8)

ABductor Pollicis Longus Action

• ABD thumb CMC joint

• extend thumb (accessory thumb extensor)

Thumb Movement

do hand movements

• flexion

• extension

• ADDuction

• ABDuction

Extensor Pollicis Brevis Origin

Posterior surfaces of radius, ulnar, and interosseous membrane (more distal)

Extensor Pollicis Brevis Insertion

base of thumb proximal phalange (dorsal side)

Extensor Pollicis Brevis Innervation

Radial nerve ( POSTERIOR INTEROSSEOUS NERVE, C7-C8)

Extensor Pollicis Brevis Action

• Extend thumb CMC joint

• Extend thumb MCP joint

Extensor Pollicis Longus Origin

Posterior surfaces of ulna and interosseous memebrane (even more distal)

Extensor Pollicis Longus Insertion

base of thumb distal phalange (dorsal side)

Extensor Pollicis Longus Innervation

Radial nerve ( POSTERIOR INTEROSSEOUS NERVE, C7-C8)

Extensor Pollicis Longus Action

• Extend thumb CMC joint

• Extend thumb MCP joint

• Extend thumb IP joint

Extensor Indicis Origin

Posterior surfaces of ulna and interosseous membrane (most distal)

Extensor Indicis Insertion

EXTENSOR HOOD of index finger

Extensor Indicis Innervation

Radial nerve ( POSTERIOR INTEROSSEOUS NERVE, C7-C8)

Extensor Indicis Action

• extend MCP, PIP, and DIP joints of index

Cross-section of the Deep posterior muscle

• ABDuctor pollicis Longus

• Extensor Pollicis Brevis

• Extensor Pollicis Longus

• Extensor Indicis

LABEL ALL POSTERIOR MUSCLES CROSS-SECTION

look at image

Most anterior compartment muscles (6.5/8 muscles) are innervated by

Median nerve

All anterior compartment have the same innervation EXPECT?

Flexor Carpi Unlaris

Flexor Digitorum Profundus (medial part) by Ulnar N

All 3 DEEP anterior muscles are innervated by

ANTERIOR INTEROSSEOUS NERVE of Median N

All 12 POSTERIOR COMPARTMENTS are innvervated

Radial N

Posterior compartment

Most (3/4) superficial (posterior side) & ALL 5 DEEP muscles are innervated by

POSTERIOR INTEROSSEOUS NERVE or Radial N

Posterior compartment

Most (3/4) superficial (posterior side) & ALL 5 DEEP muscles are innervated by the same nerve EXECPT

Anconeus

All ANTERIOR COMPARTMENT 4 superficial & 1 intermediate origin is

Medial EPICONDYLE of humerus

Most POSTERIOR COMPARTMENT superficial muscles (5/7) origin is

LATERAL EPICONDYLE of the humerus

Most POSTERIOR COMPARTMENT superficial muscles (5/7) origin is the same EXPECT?

Brachioradialis

Extensor Carpi Radialis Longus

Most the POSTERIOR COMPARTMENT deep muscles (4/5) origin is from

Posterior surfaces of radius, ulna, and interosseous membrane

Most of the POSTERIOR COMPARTMENT deep muscles (4/5) origin is the same EXPECT

Supinator

Nerves

REVIEW BRACHIAL PLEXUS

-root, trunk, division, cord, nerves

• Musculocutaneous nerve

• Median nerve

• Ulnar nerve

• Axillary nerve

• Radial nerve

The median nerve innervates most of what muscles? What are the EXEMPTIONS?

Anterior compartment muscles

EXPECT Flexor carpi Ulnaris, Flexor Digitorum Profundus (medial side) by ULNAR N

Median nerve is deep to

Flexor digitorum superficialis

Median nerve enters hand through?

Carpal Tunnel

Median Nerve Largest Branch is

Anterior interosseous nerve

Anterior interosseous nerve innervates

all 3 anterior deep muscles

• flexor pollicis longus

• flexor digitorum profundus (lateral part)

• Pronator quadratus

Ulnar nerve innervates

Only 2 anterior compartment muscles of forearm

• Flexor Carpi Ulnaris

• Flexor Digitorum Profundus (medial part)

Ulnar nerve enters what structure

The hand SUPERFICIAL to the Carpal Tunnel (flexor retinaculum)

Ulnar Nerve Branches

Palmar branch & dorsal branch

Radial Nerve Innervates what muscles

All 12 posterior compartment muscles of forearm

Radial nerve Branches

• superficial branch (sensory)

• deep branch (predominately motor)

Deep branch of the radial nerve becomes what nerve?

Posterior interosseous nerve

Deep branch of the radial nerve innervates? what are the EXPECTIONS?

• most (3/4) SUPERFICIAL (posterior side) posterior muscles

EXPECTS Anconeus

• All 5 DEEP posterior muscles

Types of arteries

• Subclavian artery

• Axillary Artery

• Brachial artery

• Radial artery

• Ulnar artery

Subclavian artery branch is from

Brachiocephalic Trunk

The subclavian artery becomes what artery?

Axillary artery

Axillary artery begins at

Lateral border of rib 1

Axillary artery ends at?

inferior border of teres major

Axillary artery continues as what artery?

Brachial artery

What divides Axillary artery into 3 parts

Pectoralis Minor

Part 1 of axillary artery

Superior thoracic artery

Superior thoracic artery

supplies upper regions of the medial and anterior walls

Part 2 of axillary artery

• Thoracoacromial artery

• Lateral Thoracic artery

Thoracoacromial artery

4 braches( Thoraco-acromial, Clavicular, Humeral, Acromial, Pectoral)

Supplies anterior axillary walls

Lateral Thoracic artery

Supplies medial and anterior walls