Upper Limb
Arm & Forearm
Arm Cross Section
The intermuscular septum and the humerus divide
the arm into anterior and posterior compartments
Anterior Compartment:
Flexor’s
“3” muscles
Musculocutaneous nerve
Brachial artery
Posterior Compartment:
Extensor’s
“3” muscles
Radial nerve
Deep brachial artery
Posterior Compartment
Triceps brachii
Lateral head
Posterior surface of humerus –
superior to radial grove
Long head
Infraglenoid tubercle
All three heads have a common
distal attachment on the olecranon
Radial nerve
Deep brachial
a.
Medial head
Posterior surface of humerus –
inferior to radial grove
Muscles of the Arm - Posterior
Long
head:
Power
assist for
elbow
extension
Medial head :
primary
extensor
Active
throughout
elbow
extension
Triceps Brachii
Primary elbow
extensor
Anterior Compartment
Biceps brachii
Long head –
supraglenoid tubercle
coracobrachialis
Corocoid process to mid
way along the medial
humerus
Short headcorocoid process
Common insertion:
tuberosity of the
radius
Brachial a
Musculocutaneous n.
brachialis
Anterior surface of
humerus to
coronoid process
and tuberosity of
the ulna
Muscles of the Arm - Anterior
Biceps Brachii
Primary forearm
supinator
Power assist for
elbow flexion
Brachialis
Primary elbow
flexor
Active throughout
elbow flexion
Coracobrachialis
Action at the GH
joint for flexion &
adduction
Elbow Joint- A “Hinge” Joint
Humeroulnar
joint
Humeroradial
joint
Enclosed in a single joint
capsule (along with the
superior radioulnar joint)
Distal Humerus
In full flexion, the
rim of the radial
head slides in the
capitulotrochlear
groove and enters
the radial fossa
Medial
Lateral
The trochlear ridge of
the olecrenon rides in
the trochlear groove
(right)
Lenangie 8-1
Bones of the Elbow
The lower end of the humerus flairs out as epicondyles. These
provide a mechanical advantage to the forearm muscle groups
that attach at these sites.
Lateral
Medial
extensors
capitulum
trochlea
Attachment
of the biceps
Anterior view
lateral
Medial
flexors
Attachment of
the brachialis
Posterior view
Elbow Xray
• O = olecranon
• T = trochlea of the
humerus
• CP = coronoid
process of the ulna
• HR = head of the
radius
• C = capitulum
Carrying Angle of the Elbow
Formed by the
vertical axis of the
humerus and the
vertical axis of the
forearm
The angulation is due to
the configuration of the
bony articulating
surfaces
Males = 5o
Females = 10o - 15o
Transverse Axis
Includes the humeroulnar
and humeroradial joints
Flexion and extension
Flexors:
Extensors:
Biceps,
brachialis,
brachioradialis
Triceps,
anconeus
Elbow Flexors
In addition to the
biceps and brachialis,
the brachioradialis
also functions as a
flexor of the elbow
Each functions at
differing degrees of
supination and
pronation of the
forearm
Collateral Ligaments
Increase stability and joint apposition
Annular ligament
Ulnar
collateral
“MCL”
medial
Capitulum
Radial head
lateral
Radial
collateral
“LCL”
Annular ligament
Fibers of
the radial
collateral
ligament
attach to the
annular
ligament
Annular Ligament
Annular
ligament acts
like a sling
holding the
radial head
close to the
ulna bone
Radial
collateral
Synovial fold
Annular ligament
offers support but
allows rotation
(spin) as well as
glide of the radial
head during
supination/
pronation
Radioulnar Joint Motion
supination
pronation
Radioulnar Joint
Complex joint with 2
articulations connected
by the interosseous
membrane
Superior (annular ligament)
Inferior – with capsule and disc
Vertical Axis
Humeroradial and radioulnar joints
Forearm supination and pronation
Muscles of
Supination/Pronation
Supinator &
biceps brachii
Pronator teres &
pronator quadratus
Forearm Cross Section
The
interosseus
membrane and
radius and ulna
divide the
forearm in to
anterior and
posterior
compartments
Innervation rule
• All muscles of the anterior compartment are
supplied by the median nerve Or Ulnar
nerve
• All muscles of the posterior compartment
are supplied by the radial nerve.
Superficial Muscles of the
Anterior Forearm
5 superficial muscles
From the common
flexor tendon arising
from the medial
condyle of the
humerus
Cross the elbow but
have minimum function
at that joint
Surface Anatomy - Anterior Forearm
lateral
Thumb = pronator teres
2nd digit =
flexor carpi
radialis
3rd digit =
palmaris
longus
medial
5th digit (tucked
under) = flexor
digitorum
superficialis
4th digit =
flexor carpi
ulnaris
Deep Muscles of the
Anterior Forearm
3 Deep
Muscles
Thumb
Fingers
Wrist
Arise from the
ulna (pronator
quadratus, flexor
digitorum
profundus) and
radius (flexor
pollicis longus)
Superficial muscles of the
posterior forearm
extensor carpi
radialis longus
E
superficial
extensor carpi
radialis brevis
superficial
extensor carpi
ulnaris
Extensor
3 Superficial
Muscles
E
carpi
ulnaris
Extensor carpi
radialis brevis
Extensor carpi
radialis longus
Intermediate muscles of the
posterior forearm
2 Int Muscles
Extensor digiti
minimi muscle
Extensor digitorum
Deep muscles of the posterior
forearm
5 muscles
Abductor pollicis
longus
Extensor pollicis
brevis
Extensor pollicis
longus
Supinator
Extensor indices
Median Nerve
All forearm muscles
are innervated by
the MEDIAN nerve
EXCEPT:
1 ½ muscles
flexor carpi
ulnaris
ulnar side of the
flexor digitorum
profundus
Plus: All thenar
mm except
adductor pollicis
Brachial Artery
in Situ
Posterior circumflex
humeral a. runs with
the axillary nerve
Deep brachial a.
runs with radial nerve
Superior ulnar
collateral a. runs with
the ulnar nerve
Brachial Artery Anastomoses
Radial & Ulnar Arteries
lateral
Radial artery
medial
Ulnar artery
Common interosseous
Dorsal and palmer
carpal branches
Deep (superficial) palmar
arches
Anterior
Posterior
Dorsal and palmer
carpal branches
superficial (deep)palmar arches
Injuries
Stretch of the MCL during throwing
Cubital tunnel
syndrome –
contraction of the
flexor carpi
ulnaris causes
nerve
compression
Loss of IR & ER rotation of the shoulder may lead to excessive
pronation of supination of the forearm and subsequent muscle
strain
Injuries
Fall on the outstretched
hand may lead to fracture
of the elbow
Nursemaid’s
elbow – radial
head subluxed
from the annular
ligament in an
unexpected pull