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Anatomy Of Arm And Forearm
Dr. Fadel Naim
Orthopedic Surgeon
Faculty of Medicine
IUG
Muscles of the Arm
 4 arm (brachial) muscles:
– 3 flexors in the anterior
compartment
• Supplied by the
musculocutaneous nerve
– Biceps brachii
– Brachialis
– Coracobrachialis
– 1 extensor in the
posterior compartment
• Triceps brachii
– Supplied by the radial
nerve.
BICEPS BRACHII
 ORIGIN
– Long head:
• supraglenoid tubercle of scapula.
– Short head:
• coracoid process of scapula with
coracobrachialis
 INSERTION
– posterior border of bicipital
tuberosity of radius (over bursa)
– bicipital aponeurosis to deep fascia
and subcutaneous ulna
 ACTION
– Supinator of the forearm
– Flexion of the elbow
– weakly flexes shoulder
 NERVE
– Musculocutaneous nerve (C5, 6)
(from lateral cord)
 When the elbow is extended
 The biceps is a simple flexor of the forearm
 When the elbow is flexed and more power is
needed against resistance
 The biceps is the primary (most powerful) supinator of
the forearm
 When right-handed persons drive a screw into hard
wood
 Inserting a corkscrew and pulling the cork from bottle.
 The biceps barely operates during flexion of the
prone forearm.
BRACHIALIS
 ORIGIN
– Anterior lower half of humerus
– medial and lateral intermuscular
septa
 INSERTION
– Coronoid process and
tuberosity of ulna
 ACTION
– Flexes elbow
 NERVE
– Musculocutaneous nerve (C5, 6)
( from lateral cord).
– Also small supply from radial
nerve (C7)
 The brachialis is the main flexor of the forearm
 Flexes the forearm in all positions and during slow
and quick movements.
 When the forearm is extended slowly, the brachialis
steadies the movement by slowly relaxing
(picking up and put down a teacup carefully)
 The brachialis always contracts during flexion of
the elbow joint and is primarily responsible for
maintaining flexion
 Because of its many functions, it is regarded as the
workhorse of the elbow flexors
CORACOBRACHIALIS
 ORIGIN
– Coracoid process of scapula with biceps
brachii
 INSERTION
– Upper half medial border of humerus
 ACTION
– Flexes and weakly adducts arm
 NERVE
– Musculocutaneous nerve (C5, 6, 7) (from
lateral cord)
•Biceps
brachii
•Long
head
•Shor
t head
•Coracobrachialis
•Biceps
tendon
•Aponeurosis of
biceps brachii
•Acromion process
•Coracoid process
•Humerus
•Coracobrachialis
•Musculocutaneous
n.
•Brachialis
•Radius
•Ulna
TRICEPS
 ORIGIN
– Long head:
• infraglenoid tubercle of scapula.
– lateral head:
• upper half posterior humerus (linear origin).
– medial head:
• lies deep on lower half posterior humerus inferomedial to spiral groove and
both intermuscular septa
 INSERTION
– Posterior part of upper surface of olecranon process of ulna and posterior
capsule
 ACTION
– Extends elbow
– Long head stabilizes shoulder joint
– medial head retracts capsule of elbow joint on extension
 NERVE
– Radial nerve (C7, 8) (from posterior cord ), four branches
•Deltoid
(cut)
•Long
head
•Lateral
head
•Olecranon
•Anconeus
•Triceps brachii
•Dorsal scapular
nerve
•Suprascapular nerve
•Axillary nerve
•Triceps
brachii
•Long head
•Medial
head
•Anconeus
•Lateral
head
•Radial
nerve
Cubital Fossa
The cubital fossa is the triangular hollow
area on the anterior aspect of the elbow
The boundaries of the cubital fossa are:


–
Superiorly
1.
–
An imaginary line connecting the medial and
lateral epicondyles
Medially
2.
–
The pronator teres
Laterally
3.
•1
The brachioradialis
•3
•2
The contents of the cubital fossa
1.
2.
3.
4.
5.
Median nerve
Terminal part of the brachial artery and
bifurcation into
–
The radial artery
–
The ulnar artery
(Deep) accompanying veins of the arteries
Biceps brachii tendon
The deep and superficial branches of the radial
nerve are within the floor of the fossa.
Median cubital vein, lying anterior to the
brachial artery

•

Superficially, in the subcutaneous tissue overlying
the fossa
Medial and lateral antebrachial cutaneous
nerves related to the basilic and cephalic veins.
Articulation of the Elbow Joint


A hinge type of synovial joint
Articulation:
– The humerus
• The spool shaped trochlea
• The spheroidal capitulum
– The trochlear notch of the ulna
– The slightly concave superior
aspect of the head of the radius
 Humeroulnar articulation
 Humeroradial articulation
Articulation of the Elbow Joint

Fully congruent when the forearm is in a
position midway between pronation and
supination and is flexed to a right
angle.
Ligaments of the Elbow Joint

The collateral ligaments of the elbow joint are
strong triangular bands
– Medial and lateral thickenings of the fibrous capsule
Ligaments of the Elbow Joint

The lateral, fanlike radial
collateral ligament
– Extends from the lateral epicondyle of
the humerus and blends distally
with the anular ligament of the
radius
Ligaments of the Elbow Joint

The medial, triangular ulnar collateral ligament
– Extends from the medial epicondyle of the humerus
to the of the ulna
– Consists of three bands:
1. The anterior cordlike band is the strongest
2. The posterior fanlike band is the weakest
3. The slender oblique band deepens the socket for the
trochlea of the humerus
Muscles Moving the Elbow Joint


Several muscles cross the
elbow and extend to the
forearm and hand:
Chief flexors of the elbow
joint
– Brachialis
– Biceps brachii
– Brachioradialis

Chief extensors of the
elbow joint
– Triceps brachii
Bursae Around the Elbow Joint

The three olecranon bursae are the:
1. Intratendinous olecmnon bursa
2. Subtendinous olecranon bursa
3. Subcutaneous olecranon bursa
Proximal Radioulnar Joint

The proximal radioulnar joint is a pivot type of synovial joint
– allows movement of the head of the radius on the ulna


The head of the radius articulates with the radial notch of
the ulna.
The radial head is held in position by the anular ligament.
Movements of the Proximal Radioulnar Joint


During pronation and
supination of the forearm, the
head of the radius rotates
within the ring formed by the
anular ligament and the radial
notch of the ulna.
The axis for these movements
passes:
– Proximally through the center of
the head of the radius
– Distally through the ulna.
Muscles Moving the Proximal Radioulnar Joint

Supination:
– The supinator (when resistance is
absent)
– The biceps brachii (when power is
required because of resistance)
– With some assistance from the: EPL (
Extensor Policis Longus ) and ECRL (
Extensor Carpi Radialis Longus )

Pronation
– The pronator quadratus (primarily)
– Pronator teres (secondarily)
– With some assistance from the FCR, PL,
and brachioradialis
• (when the forearm is in the midprone
position)
Distal Radioulnar Joint




A pivot type of synovial joint.
The radius moves around the relatively fixed distal end of
the ulna.
The head of the ulna articulates with the ulnar notch on
the medial side of the distal end of the radius.
During pronation and supination,the distal end of the radius
moves anteriorly and medially, crossing the ulna
anteriorly.
Triangular Ligament


A fibrocartilaginous articular disc ("triangular
ligament") binds the ends of the ulna and radius
together
The main uniting structure of the joint
– The base is attached to the medial edge of the ulnar
notch of the radius,
– The apex is attached to the lateral side of the base of the
styloid process of the ulna.

The articular disc separates the cavity of the distal
radioulnar joint from the cavity of the wrist joint.
Ligaments of the Distal Radioulnar Joint

Anterior and posterior
ligaments.
– These relatively weak
transverse bands extend
from the radius to the
ulna across the anterior
and posterior surfaces of
the joint
Fascial Compartment Of The Forearm

4 compartments of the
forearm
(1) superficial volar
(2) deep volar
(3) the dorsal
(4) Lateral containing the
mobile wad of henry
• Brachioradialis
• Extensor carpi radialis
longus (ECRL)
• Extensor carpi radialis
brevis (ECRB)

These fascial compartments are separated by
an interosseous membrane connecting the
radius and ulna.
– The flexors and pronators of the forearm are in the anterior
compartment and are served mainly by the median nerve;
– The one and a half exceptions are innervated by the ulnar
nerve.
– The extensors and supinators of the forearm are in the
posterior compartment and are all served by the radial
nerve
Flexor-Pronator Muscles of the Forearm
A.
A superficial group of five muscles
1.
2.
3.
4.
5.

Pronator teres
Flexor carpi radialis
Palmaris longus
Flexor carpi ulnaris
Flexor digitorum superficialis [FDS]
(intermediate)
These muscles all attach, at least in
part, by a common flexor tendon from
the medial epicondyle of the
humerus the common flexor
attachment
Flexor-Pronator Muscles of the Forearm
A deep group of three muscles:
B.
1.
2.
3.
Flexor digitorum profundus [FDP]
Flexor pollicis longus
Pronator quadratus
1. Pronator Teres

Origin:
– Humeral head:
• Medial epicondyle
• Medial supracondylar ridge
• Medial intermuscular septum
– Ulnar head:
• Medial border of coronoid process



Insertion:
– Middle of lateral surface of radius
– Just posterior to most prominent
part of lateral convexity of radius
Innervatlon:
– Median nerve (C6 and C7)
Action:
– Pronator of the forearm and a
flexor of the elbow joint.
2. Flexor Carpi Radialis

Origin:
– Medial epicondyle of humerus

Insertion:
– Base of 2nd and 3rd metacarpal bone

Innervation:
– Median nerve (C6 and C7)

Action:
– Flexion (when acting with the flexor
carpi ulnaris)
– Abduction of the wrist (when acting
with the extensors carpi radialis
longus and brevis)
– A combination of flexion and
abduction at the wrist ( when acting
alone )
3. Palmaris Longus
 Origin:
– Medial epicondyle of
humerus
 Insertion:
– Distal half of flexor
retinaculum and palmar
aponeurosis
 Innervation:
– Median nerve (C7 and C8)
 Action:
– Flexes hand (at wrist)
– Tightens palmar
aponeurosis
Palmaris Longus

This small fusiform muscle is absent on
one or both sides (usually the left) in
approximately 10% of people, but its
actions are not missed.

The palmaris longus tendon is a useful
guide to the median nerve at the wrist.

The tendon lies deep and slightly
medial to this nerve before it passes
deep to the flexor retinaculum.

To test the palmaris longus:
– The wrist is flexed and the pads of the little
finger and thumb are pinched together.
– If present and acting normally, the tendon can
be easily seen and palpated.
4. Flexor Carpi Ulnaris

Origin:
– Humeral head:
• medial epicondyle of humerus
– Ulnar head:
• olecranon and posterior border of ulna

Insertion:
– Pisiform bone
– Hook of hamate bone
– 5th metacarpal bone

Innervation:
– Ulnar nerve (C7 and C8)

Action:
– Flexes and adducts the hand at the wrist simultaneously if
acting alone.
– Flexes the wrist when it acts with the flexor carpi radialis
– Adducts it when acting with the extensor carpi ulnaris.
1. Flexor Digitorum Superficialis

Origin:
– Humeroulnar head:
• Medial epicondyle of humerus
• Ulnar collateral ligament,
• Coronoid process of ulna
– Radial head:
• Superior half of anterior border of radius

Insertion:
– Bodies of middle phalanges of medial four digits

Innervation:
– Median nerve (C7, C8, and T1 )

Action:
– Flexes middle phalanges at proximal
interphalangeal joints of medial four digits
– Acting more strongly, it also flexes proximal
phalanges at metacarpophalangeal joints and hand
Flexor Digitorum Profundus

Origin:
– Proximal three-fourths of medial and anterior
surfaces of ulna
– Interosseous membrane

Insertion:
– Bases of distal phalanges of medial four digits

Innervation:
– Medial part ( the muscle serving digits 4 and
5)
• Ulnar nerve (C8 and T1)
– Lateral part: ( the muscle serving digits 2
and 3 )
• Median nerve (C8 and T1 )

Action:
– Flexes distal phalanges at distal
interphalangeal joints of medial four digits
– Assists with flexion of hand
Flexor Pollicis Longus

Origin
– Anterior surface of radius and adjacent
interosseous membrane

Insertion
– Base of distal phalanx of thumb

Action
– Flexes phalanges of 1st digit (thumb

Innervation
– Anterior interosseous nerve from median
nerve (C8 and T1)
Pronator Quadratus

Origin
– Distal 1/4 of anterior surface of ulna

Insertion
– Distal 1/4 of anterior surface of
radius

Action
– Pronates forearm; deep fibers bind
radius and ulna together
– The prime mover in pronation.
– Initiates pronation

Innervation
– Anterior interosseous nerve from
median nerve (C8 and T1)
Extensor Muscles of the Forearm



In the posterior (extensor-supinator) compartment of
the forearm
All are innervated by the radial nerve
Three functional groups:
1. Muscles that extend and abduct or adduct the hand at
the wrist joint
• Extensor carpi radialis longus
• Extensor carpi radialis brevis
• Extensor carpi ulnaris
2. Muscles that extend the medial four digits
• Extensor digitorum
• Extensor indicis
• Extensor digiti minimi
3. Muscles that extend or abduct the thumb
• Abductor pollicis longus [APL]
• Extensor pollicis brevis [EPB]
• Extensor pollicis longus [EPL]
Brachioradialis

Origin
– Proximal two-thirds of lateral
supracondylar ridge of humerus

Insertion
– Lateral surface of distal end of
radius

Action
– Flexes forearm

Innervation
– Radial nerve (C5, C6, and C7)
Extensor Carpi Radialis Longus

Origin
– Lateral supracondyle ridge of
humerus

Insertion
– Base of 2nd metacarpal

Action
– Extend and abduct hand at wrist
joint

Innervation
– Radial nerve (C6 and C7)
Extensor Carpi Radialis Brevis

Origin
– Lateral epicondyle of humerus

Insertion
– Base of 3rd metacarpal

Action
– Extend and abduct hand at wrist
joint

Innervation
– Deep branch of radial nerve (C7
and C8)

The extensor carpi radialis brevis and
longus act together to steady the wrist
during flexion of the medial four digits.
•
•
1.
2.
3.
4.
Posterior
compartment:
Superficial group
Extensor digitorum
Extensor digiti minimi
Extensor carpi
ulnaris
Anconeus muscle
•
•
1.
2.
3.
4.
Posterior compartment:
Deep group
Supinator
Abductor pollicis longus
Extensor pollicis brevis
Extensor indicis
•Attached by a common
extensor tendon to the
lateral epicondyle
Extensor Digitorum

Origin
– Lateral epicondyle of humerus

Insertion
– Extensor expansions of medial four
digits

Action
– Extends medial four digits at
metacarpophalangeal joints;
Extends hand at wrist joint

Innervation
– Posterior interosseous nerve (C7 and
C8), the continuation of the deep branch
of the radial nerve
Extensor Digitorum

The principal extensor of the medial four digits

Adjacent tendons are linked by intertendinous
connections.

Because of presence of the intertendinous
connections extension of one finger is
impossible

The index finger has greater freedom because
its tendon is not connected to the other tendons
Extensor Digiti Minimi

Origin
– Lateral epicondyle of humerus

Insertion
– Extensor expansion of 5th digit

Action
– Extends 5th digit at
metacarpophalangeal and
interphalangeal joints

Innervation
– Posterior interosseous nerve (C7
and C8), the continuation of the
deep branch of the radial nerve
Extensor Carpi Ulnaris

Origin
– Lateral epicondyle of humerus and
posterior border of ulna

Insertion
– Base of 5th metacarpal

Action
– Extends and adducts hand at wrist
joint

Innervation
– Posterior interosseous nerve (C7
and C8), the continuation of the
deep branch of the radial nerve
Supinator

Origin
– Lateral epicondyle of humerus
– radial collateral and annular
ligaments
– supinator fossa and crest of ulna

Insertion
– surface of proximal 1/3 of radius
• Lateral
• Posterior
• Anterior

Action
– Supinates forearm

Innervation
– Deep branch of radial nerve (C5
and C6)
Abductor pollicis Longus

Origin:
– Posterior surfaces of
• Ulna
• Radius
• Interosseous membrane

Insertion:
– Base of 1st metacarpal

Action:
– Abducts thumb
– Extends it at carpometacarpal joint

Innervation:
– Posterior interosseous nerve (C7
and C8), the continuation of deep
branch of radial nerve
Extensor Pollicis Brevis

Origin
– Posterior sufraces of radius
and interosseous membrane

Insertion
– Base of proximal phalanx of
thumb

Action
– Extends proximal phalanx of
thumb at carpometacarpal joint

Innervation
– Posterior interosseous nerve
(C7 and C8), the continuation of
the deep branch of the radial
nerve
Extensor Pollicis Longus

Origin
– Posterior surface of middle 1/3 of ulna
and interosseous membrane

Insertion
– Base of distal phalanx of thumb

Action
– Extends distal phalanx of thumb at
carpometacarpal and interphalangeal
joints
– Adducts the extended thumb and
rotates it laterally

Innervation
– Posterior interosseous nerve (C7 and
C8), the continuation of the deep
branch of the radial nerve
Extensor Indicis

Origin
– Posterior sufrace of ulna
– interosseous membrane

Insertion
– Extensor expansion of 2nd digit

Action
– Extends 2nd digit and helps to
extend hand

Innervation
– Posterior interosseous nerve (C7
and C8), the continuation of the
deep branch of the radial nerve