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