19/02/07
26/03/07 HUBS1105L8
Blood Vessels and Nerves of the Upper LimbLearning Objectives:1.
Understand the formation & distribution of the brachial
plexus(Identify roots, trunks and cords of brachial plexus
(Identify named nerves: axillary, radial, musculocutaneous,
median & ulnar
(Illustrate the structure of the brachial plexus
diagrammatically
(Describe the distribution of axillary, radial,
musculocutaneous, median & ulnar nn.
(Describe the major courses & relations of these nerves
(Describe segmental innervation of upper limb - dermatomes &
myotomes
(State major effects of damage to:axillary, radial,
musculocutaneous, median & ulnar nn.
(Describe the motor & sensory nerve supply to the hand
(Describe methods of testing nerve integrity
2. Understand the structure of blood vessels to the upper
limb
(Identify arteries: subclavian, axillary, brachial, radial,
ulnar, superficial & deep palmar arches
(Identify superficial veins: cephalic. basilic, median
cubital
(Identify deep veins: brachial, venae comitantes
(Identify main features of arteriograms or venograms
(Describe the course & relations of major arteries &
veins
(Describe the pattern of superficial & deep venous return
(including valves)
(Describe the surface markings of major vessels
(Describe & explain the function of collateral arterial
anastomoses
(Explain the hazard of injection in the cubital fossa
(Demonstrate & describe the palpation of pulses of the
subclavian, axillar, brachial, radial & ulnar arteriesThe
Nervous System
The nervous system is organized into the central nervous system
(brain and spinal chord) and the peripheral nervous system (nerve
fibres that carry information between the CNS and the rest of the
body).
The spinal chord only goes as far as the lumbar region of the
spine. After this point the spinal nerves dangle downwards in a
large lead.NERVES OF THE UPPER LIMB
The Peripheral Nervous System
The link between the neurons of the central nervous system and
the rest of the body.
Nerve cell bodies are clustered into groups called ganglia
Nerve cell axons are bundled together and wrapped in connective
tissue to for the peripheral nerves. These axons carry sensory and
motor commands.
Afferent Nerves: These come from the dorsal roots of the spinal
chord. They send information about the internal and external
environment to the CNS. Visceral afferents carry subconscious
input, whereas sensory afferents carry conscious input. Sensory
information is categorised as either somatic (arising from the
bodys surface) or special (including vision, hearing, taste and
smell) sensation.
Efferent Nerves: These come from the ventral roots of the spinal
chord and are the communication link by which the CNS controls the
activities of muscles and glands, the effector organs that carry
out actions. The CNS regulates these organs by initiating action
potentials in the cell bodies of efferent neurons, whose axons
terminate on these organs. The autonomic nervous system innervates
the involuntary branch of the peripheral efferent division (smooth
and cardiac muscle and glands) and the somatic nervous system
innervates voluntary control (skeletal muscle). The autonomic
nervous system is further divided into the sympathetic and
parasympathetic nervous systems. Nerves can either arise from the
brain stem (12 cranial nerves mainly control the structures of the
head) or the spinal chord (31 pairs of spinal nerve come off the
spinal chord through openings between vertebrae) The spinal chord
has two functions. It is the neuronal link between the brain and
the peripheral nervous system, being organised into ascending and
descending tracts for communication in both directions. It is also
the integrating center for spinal reflexes including the basic
protective and postural reflexes. Afferent and efferent fibres are
bundled together into spinal nerves, which supply specific body
regions and are attached to the spinal chord in a paired fashion
throughout its length.
After the spinal nerves emerge from the spinal chord they
progressively branch to form a network of peripheral nerves that
supply the tissues. The posterior branch* supplies the deep muscles
of the back and skin, whilst the ventral branch is larger and forms
plexuses (nerve networks) and supplies the superficial back,
extremities and the lateral and ventral trunk, except in the
thoracic region where it forms the intercostal nerve. => * Must
remember posterior branch for exam.Root Value: The spinal nerve
from which a nerve is derived (may be more than one). The spinal
chord segments to which sensory and motor neurons attach.
Motor Distribution: The efferent distribution from the CNS to
the muscle (The information going from the brain to the muscles).
The list of muscles supplied by a nerve.
Sensory Distribution: The afferent distributions, from the body
to the CNS. The peripheral nerve. Afferent information is received
from the muscle, connective tissue and jointsCutaneous
Distribution: The afferent distribution of a peripheral nerve to
the skin.Brachial Plexus The brachial plexus is composed of spinal
nerves C5 to T1.
It is the sensory and motor supply to the upper limb, except for
the tip of the shoulder (these are derived from the cervical
plexus) It is an arrangement of nerve fibres running from the spine
through the neck and the axilla and into the arm.
The brachial plexus elements consist of roots, trunks,
divisions, cords and branches (collateral/preterminal and terminal
branches)
Roots The roots are the five anterior rami of the spinal nerves
after they have given off thioer segmental supply to the muscles of
the neck.
Trunks The roots form three trunks: Superior (upper) trunk From
C5 and C6
Middle trunk formed by C7
Inferior (lower) trunk formed by C8 and T1
Each trunk then splits into two, an anterior and posterior
division, to form six divisions
Cords The six divisions regroup to become three cords. These are
named by their position with respect to the axillary artery:
Posterior cord formed by the posterior divisions of the three
trunks
Lateral cord formed by the anterior divisions of the superior
and middle trunks
Medial cord continuation of the inferior trunk
The posterior cord branches into 2 terminal branches of the
brachial plexus, the small axillary nerve and the large radial
nerve The anterior branches of the brachial plexus (lateral and
medial cords) form an M shape. This M gives rise to 3 terminal
branches of the brachial plexus. The musculocutaneous nerve
branches off the lateral cord. The ulnar nerve is a continuation of
the medial cord and the median nerve is formed by the joining of
the medial and lateral cords.
There are also lots of little branches of the brachial plexus
before the terminal branches. These go to the shoulder region.
Posterior Brachial Plexus
Axillary Nerve
A small branch of the posterior brachial plexus
The roots are C5 and C6
Goes straight through to the axilla Supplies the deltoid and
teres minor muscles (all other rotator cuff muscles are supplied by
the suprascapula nerve)Radial Nerve
A large branch of the posterior brachial plexus
The roots are C5 T1
Innervates all muscles at the back of the arm and the back of
the forearm, including the supinator (the posterior compartments of
the arm)
Cutaneous distribution is the posterior arm, posterior forearm
and the lateral part of the back of the hand
It is the most vulnerable at three points, high in the axilla,
against the humerus (sits on back of humerus) and at the neck of
the radius.
Anterior Brachial Plexus
Musculocutaneous Nerve
Roots are C5 C7
Supplies all of the anterior arm muscles (the BBC)
Cutaneous distribution is the anterolateral skin of the
forearm
Median Nerve
Roots are C6 - T1
Bypasses the arm to reach the forearm where it supplies the
anterior forearm muscles (flexors and pronators) except the medial
half of the flexor digitorum profundus and the flexor carpi
ulnaris. It then goes on to supply the lateral two lumbricals and
the thenar muscles of the hand Cutaneous distribution if the skin
on the lateral 3 fingers on the palmar surface and just over the
nail beds.
Ulnar Nerve
Roots values are C7 - T1
Ulnar nerve basically supplies everything the radial nerve does
not. It too bypasses the arm to supply the medial half of the
flexor digitorum profundus, the flexor carpi ulnaris and everything
in the hand except the lateral two lumbricals and the thenar
Supplies the skin on the medial 1 fingers on the front and back
of the hand.
* Note: All nerves can be described in terms of the peripheral
nerve of supply or of the segmental origin of those fibres.
Motor Segmental Distribution: Spinal roots that supply a
particular group of muscles involved in a specific movement (e.g.
elbow flexion is supplied by C5, C6 and elbow extension by C7,
C8)
Myotomes: A group of muscles supplied by a single spinal cord
segment (consists of muscles not nerves). Myotomes are named from
the segment giving origin to motor neurons supplying its muscles
(e.g. T1 myotome is the intrinsic muscles of the hand. The T1
neurons are received via the median and ulnar nerves)
Dermatomes: The region of skin that receives sensory innervation
from a single spinal cord segment (consists of skin, not nerves).
Named in reference to spinal cord segment which gives attachment to
sensory neurons that supply it.
Nerve Lesions* Note: Need to know for exam
Lesions of the brachial plexus are quite common due to the
region and the abundance of compressions, trauma, dislocations and
fractures.
Wherever the point of damage is, effects will be distal to that
pointAfferent (sensory) lesions
Lesions lead to sensory defects, as impulses are unable to reach
the spinal cord (there is a loss of cutaneous sensation)
There is a loss of spinal reflexes as these are also dependent
on afferent impulses (e.g. pain withdrawal reflex)
Damage or pressure of the nerve can cause impulses from the site
and result in tingling, itching or pain (e.g. pain when the funny
bone is hit, due to the ulnar nerves positioning on the elbow)
Efferent (motor) lesions
If impulses are unable to reach the muscles then paralysis
results. This can be either complete or incomplete
There is a loss of spinal reflexes
Muscle will become flaccid and atrophy if no nerve regeneration
occurs
NERVESITE OF INJURYPARALYSISMOTOR LOSSSENSORY LOSS
Axillaryaxilladeltoidhumeral abductionover lower deltoid
Musculocutaneousaxillaarm flexorsweak forearm flex (due to the
brachioradialis) & supinationlateral forearm
Radialaxilla
cubital fossasupinator & extensors
all except tricepsweak supination (biceps brachii is a powerful
supinator, therefore supination is not lost), loss of extension,
the wrist will dropas above except tricepslat. dorsum of hand
Medianelbow
wristpronators, flexors exc. FCU/med. FDP, thenar,
lat 2 lumbricals
(paralysis of most of the forearm muscles)thenar
mm.loss/impaired flexion of wrist
& digits
loss of opposition
& precision grip loss opposition & precision griplat. 3
1/2 digits
lat. 3 1/2 digits
Ulnarabove elbow
at wristFCU, med. FDP, hypothenar, add. poll., med. 2
lumbricals, interossei
(paralysis of the medial forearm muscles and intrinsic hand
muscles)
as above, except FDPimpaired hand function;
claw hand - loss of power grip unimpaired flexion of digits 4, 5
at IP jointspalm & dorsal 1 1/2 digits
BLOOD VESSELS OF THE UPPER LIMB Blood vessels can be
distinguished from nerves because they are hollow. Arteries are
firm, viens are thin and flimsy and nerves feel like calamari.
Arteries
The aorta is the artery through which blood leaves the heart. It
has three branches, the brachiocephalic (which forms the right
common carotid and the right subclavian), the left common carotid
and the left subclavian.
The subclavian arches across the 1st rib and becomes the
axillary, which goes through the axilla and becomes the brachial
artery when it reaches the humerus. The axillary artery begins
medially and comes around to the middle of the humerus and down
into the middle of the cubital fossa. The brachial artery then
comes across the head of the radius and divides into two terminal
branches, the radial artery (small) and the ulnar artery
(large)
The radial artery begins at the cubital fossa and runs down the
lateral side of the forearm. It sits lateral to the flexor carpi
radialis tendon, running down the forearm to sit in the floor of
the anatomical snuffbox. It pierces the 1st dorsal interosseous
muscle then goes deep into the palm to form the deep palmar
arch.
The Ulnar artery becomes more superficial as it travels to the
wrist. It sits on the lateral side of the pisiform on top of the
flexor retinaculum. As it reaches the palm it forms the superficial
palmar arch, which extends more distally than the deep palmar
arch.
Each of the superficial and deep palmar arches are completed
from a branch of the other.
The arches give off digital branches. The superficial arch gives
off branches to the medial 3 fingers only and the deep arch gives
off branches to the lateral 1 fingers only.
Arterial Anastomoses
The arteries of the arm have a collateral circulation. These are
small indirect branches through which blood can flow if the main
vessel is obstructed. They occur in areas where compression of the
arteries is likely (e.g. when grasping objects or clenching the
fist). They are also present in the palm between the superficial
and deep palmar arches and around joints (periarticular
anastomoses).Pulse
Can be palpated at:
The clavicle
The axilla
The brachial artery
Bicipital groove
wy down the humerus
Cubital fossa (used to take blood pressure)
Flexor carpi radialis tendon
The base of the anatomical snuffbox
Superficial to the flexor retinaculum
Veins
Veins are described according to the direction of blood flow.
Therefore the origin is distal and the insertion is proximal, since
the blood flows back to the heart. Veins have valves to prevent the
reverse flow of blood because the blood flow is against gravity and
therefore it is harder for the blood to get up through them. The
valves are formed by folds (1-3 cusps). The circumference of the
vein is thicker at points where there is a valve. Veins have a
wiggly appearance
There are two sets of veins, superficial and deep.
Superficial Veins
These are just under the superficial fascia of the skin
They are very variable
They are very large
Superficial veins sit on top of the muscles
Superficial veins must drain into deep veins before the blood
can drain into the heart.
The back of the hand houses the dorsal venous arch, a network of
veins that continues on as two veins, the basilic vein on the
medial side and the cephalic vein on the lateral side. The basilic
vein comes up the medial side of the forearm and goes deep to joint
the brachial vein somewhere between the elbow and the axilla. The
cephalic vein comes up the lateral side of the forearm and goes
into the gap between the deltoid and the pectoralis major where it
goes deep to join the axillary vein. The medial cubital vein
travels laterally across the cubital fossa. This is the vein that
blood samples are usually taken from. A median antebrachial vein
exists in the area of the cubital fossa. Its position can vary,
either stemming from the median cubital vein or the cephalic
vein.
Other veins may also be present.
Deep Veins
Also known as Venae comitantes they are very small
These are always found in pairs
They are the approximately the size of the brachial vein or
smaller
Have similar names to the arteries
There are two radial, two ulnar, two brachial and two axillary
veins that drain into one axillary vein that then drains into the
subclavian vein. The blood then drains into the internal jugular,
the brachiocephalic vein and eventually the superior vena cava and
the heart.
* Note: The veins are tied up with fascia and the arteries. Need
to know this for an exam. It is often not just the artery that
needs to be identified, but the artery and the vien.
C5, 6, 7, 8, T1
C5, 6
ALL posterior
Arm & Forearm
Muscles
RADIAL NERVE
Sensory
Supinator
All extensors
Brachioradialis
Anconeus
Triceps
Teres
minor
Deltoid
AXILLARY NERVE
C5, 6, 7
(Lateral cutaneous
Nerve of thigh)
Sensory
Anterior
Compartment
Of Arm
Brachialis
Biceps brachii
Coracobrachialis
C6, 7, 8, T1
Sensory
Lumbricals (2 lateral)
Thenar muscles
Anterior
Compartment
of Forearm
All flexors
(except FCU &
Medial half FDP)
Pronators
C7, 8, T1
Anterior
Forearm
Muscles
Most small
Hand muscles
Sensory
Interossei
Lumbricals (2 medial)
Adductor pollicis
Hypothenar muscles
Sensory
Flexor digitorum profundus
(ulnar half)
Flexor carpi ulnaris
Sensory
Pectoral muscles
ULNAR
RADIAL
MEDIAN
MUSCULO-
CUTANEOUS
MUSCULO-
CUTANEOUS
RADIAL
RADIAL
AXILLARY
AXILLARY
POSTERIOR
ANTERIOR
C7
C8
T1
C6
C5
T2
T2
T1
C8
C7
C6
C5
CUTANEOUS NERVE
DISTRIBUTION
DERMATOMES
Digitial Aa.
6
5
6. Deep palmar arch
5. Superficial palmar
arch
4. Ulnar
3. Radial
2. Brachial
1. Axillary
6. Median cephalic
& median basilic
5. Median antebrachial
4. Median cubital
3. Basilic vein
2. Cephalic vein
1. Dorsal venous arch