Block 12 Week 1 Flashcards
Axilla = Armpit
Apex – also known as the axillary inlet, it is formed by lateral border of the first rib, superior border of scapula, and the posterior border of the clavicle.
Lateral wall – formed by intertubercular groove of the humerus.
Medial wall – consists of the serratus anterior and the thoracic wall (ribs and intercostal muscles).
Anterior wall – contains the pectoralis major and the underlying pectoralis minor and the subclavius muscles.
Posterior wall – formed by the subscapularis, teres major and latissimus dorsi.
Anterior Wall:
- Pectoralis minor
- Pectoralis major
Posterior Wall:
- Scapula
- Subscapularis
- Teres Major
- Lattismus Dorsi
Medial Wall:
- Serratous Anterior over 1st -4th ribs
- Intercostal Muscles
Lateral Wall:
- Intertubecular Sulcus of the Humerus
Axillary Sheath
- Covers the axillary veins, arteries and lymph nodes
- Axillary artery
- Axillary vein - main tributaries cephalic and basilic
- Brachial Plexus
- Axillary Lymph nodes
- Biceps brachii (short head) and coracobrachialis – these muscle tendons move through the axilla, where they attach to the coracoid process of the scapula.
Passageways of the axilla
- There are three main routes by which structures leave the axilla:
- Inferiorly, Laterally into upper limb
- Quadrangular space - gap in posterior wall of axilla.
Structures passing through: axillary nerve, posterior circumflex humeral artery - Clavipectoral triangle - opening in the anterior wall of axilla.
Structures passing through:
- cephalic vein enters
- medial and lateral pectoral nerves leave.
Where does Axillary Artery sit ?
- Continuation of the subclavian artery
- Divided into 3 parts and sits in different sections.
First part: The first part is between the lateral border of the first rib and the medial border of the pectoralis minor, and is contained within the axillary sheath.
Second part: posterior to the pectoralis minor
Third part: extends from the lateral border of the pectoralis minor to the inferior border of teres major.
Branches of the axillary artery:
- First part - one branch: superior thoracic artery
- Second part - 2 branches: thoracoacromial artery and lateral thoracic artery
- Third part - 3 branches: subscapular artery (largest branch of axillary artery) , anterior circumflex humeral, posterior circumflex humeral.
Pharmacology of NSAID’s
The main mechanism of action of NSAIDs is the inhibition of the enzyme cyclooxygenase (COX
Where do prostglandins come from?
-Phospholipids make up the cell membrane. Phospholipids have a glycerol chain.
-The last 20 carbons are called Arachidonic Acid.
- Arachidonic acid produces prostaglandins and leukotrienes.
- Both of these are inflammatory they cause vasodilation and endothelial constriction.
What is the role of prostaglandins?
- Inflammation
- Pain
- Fever
- Some prostaglandins also promote/increase GIT INTEGRITY. So they help produce a mucus around our stomach to stop it from digesting itself and getting stomach ulcers.
- Some prostaglandins also produce THROMBOXANE (TXA2) - they increase platelet aggregation so blood clotting.
- Whereas other prostaglandins decrease platelet aggregation.
COX enzymes
- So the COX- 1 enzyme produce the prostglandin which produce the symptoms in the first list and the COX-2 enzyme produces the second prostglandin and its associated symptoms.
- By inhibiting the COX enzymes we can inhibit he prostaglandin symptoms.
We can categorize prostaglandins into 2 main subtypes, what are the properties of each ?
Type 1:
- Increases inflammation
- Increases pain
- Increases fever
- Increases GIT (gastrointestinal tract) integrity. Helps maintain mucus barrier between stomach and strong HCL.
- Produce Thromboxane (TXA2) which promotes platelet aggregation therefore clotting. – Increases platelet aggregation - this promotes clotting
Type 2:
- Increases inflammation
- Increases pain
- Increases fever
- This type of prostaglandin is in high quantities in synovial fluid. Synovial fluid is found around synovial joints and more synovial fluid will increase inflammation of pain.
- This can lead to rheumatoid arthritis
- Decreases platelet aggregation
Which inflammatory inhibitor do NSAIDs affect ?
Which enzymes do NSAIDs inhibit?
Prostaglandins
COX-1
COX-2
Which prostaglandin enzyme does Aspirin inhibit more?
Why do doctors say take Aspirin on a full stomach?
COX-1
Aspirin decreases GIT(gastrointestinal tract) integrity. To reduce irritation to the stomach lining you should eat Aspin with a meal.
Which COX - enzyme does CELECOXIB inhibit?
- Is a COX-2 specific inhibitor
- Is a good anti-inflammatory, analgesic and antipyretic
- It decreases prostaglandins in synovial fluid so is good in treating Rheumatoid Arthritis
- However it increase platelet aggregation so increases the likelihood of clotting -> which is going to increase the risk of Myocardial infarction and stroke. This is theoretical so far Celecoxib has not been shown to have this effect.
What do leukotrienes do?
- Increase inflammation
- Increase mucous (in airways)
- Increase bronchoconstriction
These symptoms cause ASTHMA
- LRA are used to treat this. Leuokotrine Receptor Antagonists.
- Normally Leukotrines bind to leukotrine receptors to carry out their effects
-LRAs competivley inhibit leukotrines so they cant bind to their receptors and cause asthma causing effects.
Pharmacology of steroids
Brachial plexus
The cervical and thoracic nerves: C5-T1
- Then the brachial plexus is divided into: —ROOTs
-TRUNKs
-DIVISIONs
-CORDs - (Terminal) BRANCHES
‘remember to drink cold beer’
Roots:
C5-T1
C5- Dorsal Scapular Nerve (innervates the rhomboid muscles’
C5,C6,C7- Long thoracic nerve (innervates the serratus anterior)
Phrenic nerve is contributed to by C5 (innervates diaphragm)
Trunk:
Superior Trunk: C5, C6
Middle Trunk: C7
Inferior Trunk: C8, T1
Superior trunk (2):
- SUPRASCAPULAR NERVE branches off the ST (C5, C6). It innervates supraspinatus, infraspinatus, acromioclavicular, glenohumeral joints.
- SUBCLAVIAN NERVE - supplies the subclavius muscle (ST: C5, C6)
Divisions:
- Each trunk is split into a anterior and posterior division.
Cords:
- We have a lateral (superior and middle trunk anterior division), posterior (all 3 trunk posterior divisions) and medial cord (inferior trunk anterior division).
Lateral Chord:
- gives rise to Lateral pectoral nerve (pectoralis major (mostly) and pectoralis minor)
Posterior Chord:
- Upper, middle and lower subscapular nerve
Medial Chord:
- Medial cutaneous nerves of arm and forearm
- Medial pectoral nerve branch off from the medial cord (pectoralis minor and the sternocostal head of the pectoralis major)
Terminal Branches (5):
- Musculocutaneous
- Axillary
- Radial
- Median
- Ulnar
SUBSCAPULARIS MUSCLE
SUBCLAVIUS MUSCLE
Brachial Plexus
The brachial plexus is a network of nerves that innervates the shoulder, arm, and hand, by supplying afferent or sensory nerve fibers from the skin, as well as EFFERENT or motor nerve fibers to the muscles
The plexus is really important because it can get injured during sports injuries, industrial accidents, surgical procedures and other traumatic injuries to the upper limbs. And the resulting functional deficit can be significant.
Brachial Plexus
- 5 roots
- 3 trunks
- 6 divisions (3 anterior and 3 posterior)
- 3 cords
- 5 terminal branches
Additionally, there are pre-terminal or collateral branches that leave the plexus at various points along its length.
DIVISIONS (6)
Then, each trunk splits into an anterior and a POSTERIOR division - giving rise to a total of six divisions.
The six divisions then regroup with each other to form three cords.
The cords are named for their relationship to the AXILLARY artery, so there’s the lateral cord - formed by the anterior divisions of the superior and middle trunks - the POSTERIOR cord - formed by the POSTERIOR divisions of the superior, middle, and inferior trunks - and the medial cord - formed by the anterior division of the inferior trunk.
CORDS
The lateral cord gives rise to the lateral pectoral nerve.
The POSTERIOR cord gives rise to the upper, middle, and lower subscapular nerves, which help innervate the muscles that move the scapula.
And the medial cord gives rise to the medial cutaneous nerve of the arm and the medial cutaneous nerve of the forearm - which give sensory innervation to the medial skin of the arm and forearm - as well as to the medial pectoral nerve, which gives motor innervation to the PECTORALIS minor and major muscles.
Terminal branches
- The lateral cord divides into two terminal branches:
-which are the median nerve - which is formed by merging with the medial cord and is made up of contributions from C5, C6, C7, C8, and T1
- and the musculocutaneous nerve, which is made up of contributions from C5, C6, and C7.
-The POSTERIOR cord divides into two terminal branches:
-which are the AXILLARY nerve – which is made up of contributions from C5 and C6
-the radial nerve, which is made up of contributions from C5, C6, C7, C8, and T1.
the medial cord gives rise to two terminal branches, which are the:
- median nerve - which is formed by merging with lateral cord
- and the ulnar nerve, which is made up of contributions from C8, T1, and occasionally C7.
CLINICAL BRACHIAL PLEXUS
- The brachial plexus supplies all the muscles of the upper extremities so injuries to it can have devastating effects on arm and hand function
- The two most common type of injuries is upper brachial plexus injury and lower branchial plexus injury.
-
Upper brachial plexus injury
- Erb’s palsy refers to an injury to the upper roots of the brachial plexus (typically C5-6)
- Occurs during extreme lateral flexion of the head
- This happens typically to baby’s who are pulled out of the birth canal while his shoulders are stuck in the mothers pelvis
- Adults: when an oblique force pushes the head and shoulder in opposite directions such as fall from a motorcycle
- This often results in a deficit known an Erb-Duchenne paralysis - arm hangs limply at side and internally rotated, the forearm is also pronated which slightly flexes the wrist.
- This produces the characteristic waiters tip position of the arm.
Muscles affected – supraspinatus, infraspinatus, subclavius, biceps brachii, brachialis, coracobrachialis, deltoid and teres minor.
Motor functions affected – abduction at shoulder, lateral rotation of arm, supination of forearm, and flexion at shoulder.
Lower Brachial Plexus Injury
-Klumpke’s palsy is an injury of the lower roots of the brachial plexus (C8-T1).
- Occurs during extreme abduction of the arm
- Eg. someone falling off a ladder or tree trying to grab onto something
- Eg. can also occur during delivery when a baby is pulled by the arm from the birth canal
- This can result in Klumpkes paralysis which typically is represented by CLAW hand where the fingers are flexed.
- The primary feature of Klumpke’s palsy is a clawed hand. This occurs due to paralysis of the lumbrical muscles, which normally act to flex the metacarpophalangeal joints (MCPJs) and extend the interphalangeal joints (IPJs). When paralysed, the fingers subsequently become extended at the MCPJs and flexed at the IPJs, producing a clawed appearance.
Shoulder
FRACTURE AT THE NECK OF THE HUMEROUS
- Most of these fractures result from a fall on an outstretched arm; less often, a direct blow is involved.
- Often occurs in older patients
- The key neurovascular structures at risk here are the axillary nerve and posterior circumflex artery.
Axillary nerve damage will result in paralysis to the deltoid and teres minor muscles. The patient will have difficulty performing abduction of the affected limb. The nerve also innervates the skin over the lower deltoid (regimental badge area), and therefore sensation in this region may be impaired
- CORACOACROMIAL LIGAMENT
- TRAPEZOID LIGAMENT
- CONOID LIGAMENT
- STERNOCLAVICULAR LIGAMENTS
- COSTOCLAVICULAR LIGAMENT
SHOULDER JOINT
- glenohumeral joint (synovial joint) (ball and socket)
- articulation between the head of the humerus and the glenoid cavity (or fossa) of the scapula
Ligaments of the glenohumeral joint
- Glenohumeral ligaments (superior, middle and inferior) extend from the humerus to the glenoid fossa, reinforcing the joint capsule. They act to stabilise the anterior aspect of the joint.
- Coracohumeral ligament- extends from the base of the coracoid process to the greater tubercle of the humerus. It supports the superior part of the joint capsule.
- Transverse humeral ligament – extends between the two tubercles of the humerus. It holds the tendon of the long head of the biceps in the intertubercular groove.
- Coracoacromial ligament – extends between the acromion and coracoid process of the scapula, forming an arch-like structure over the shoulder joint (coracoacromial arch). This resists superior displacement of the humeral head.
Bursae of the shoulder joint
A bursa is a sac-like structure containing a small amount of synovial fluid. It functions to decrease friction between tendons, bone, and skin during movement. There are several bursae present in the shoulder joint:
- SUBACROMIAL - located deep to the deltoid and acromion, and superficial to the supraspinatus tendon and joint capsule.
It reduces friction beneath the deltoid, promoting free motion of the rotator cuff tendons. - SUBSCAPULAR- Subscapular – located between the subscapularis tendon and the scapula.
It reduces friction on the tendon during movement at the shoulder joint. - You have other minor bursae
DISLOCATION OF THE SHOULDER
- Dislocations at the shoulder are described by where the humeral head lies in relation to the glenoid fossa.
- Anterior dislocations are the most prevalent (95%)
- Posterior Dislocations (4%)
Anterior dislocation:
- caused by excessive extension and lateral rotation of the humerus
- The humeral head is forced anteriorly and inferiorly – into the weakest part of the joint capsule
-Tearing of the joint capsule is associated with an increased risk of future dislocations
- axillary nerve can be damaged in a dislocation- cause paralysis of deltoid
SHOULDER DISLOCATION
Brachial Plexus Identification
AXILLARY NERVE
Spinal roots: C5 and C6
Sensory functions: Gives rise to the upper lateral cutaneous nerve of arm, which innervates the skin over the lower deltoid (‘regimental badge area’).
Motor functions: Innervates the teres minor and deltoid muscles.
Journey of the axilla
Anatomical Course
The axillary nerve is formed within the axilla area of the upper limb. It is a direct continuation of the posterior cord from the brachial plexus – and therefore contains fibres from the C5 and C6 nerve roots.
In the axilla, the axillary nerve is located posterior to the axillary artery and anterior to the subscapularis muscle. It exits the axilla at the inferior border of subscapularis via the quadrangular space, often accompanied by the posterior circumflex humeral artery and vein.
The axillary nerve then passes medially to the surgical neck of the humerus, where it divides into three terminal branches:
POSTERIOR TERMINAL BRANCH – provides motor innervation to the posterior aspect of the deltoid muscle and teres minor. It also innervates the skin over the inferior part of the deltoid as the upper lateral cutaneous nerve of the arm.
ANTERIOR TERMINAL BRANCH– winds around the surgical neck of the humerus and provides motor innervation to the anterior aspect of the deltoid muscle. It terminates with cutaneous branches to the anterior and anterolateral shoulder.
ARTICULAR BRANCH– supplies the glenohumeral joint
SENSORY FUNCTION OF TEH AXILLARY NERVE
The sensory component of the axillary nerve is delivered via its posterior terminal branch.
After the posterior terminal branch of the axillary nerve has innervated the teres minor, it continues as the upper lateral cutaneous nerve of the arm. It innervates the skin over the inferior portion of the deltoid (the ‘regimental badge area’).
In a patient with axillary nerve damage, sensation at the regimental badge area may be impaired or absent. The patient may also report paraesthesia (pins and needles) in the distribution of the axillary nerve.
QUADRNAGULAR SPACE
Structures which pass through quadrangular space:
- axillary nerve
- posterior circumflex humeral artery
- posterior circumflex humeral vein
Borders:
Superior – inferior aspect of teres minor
Inferior – superior aspect of teres major
Lateral – surgical neck of humerus.
Medial – long head of triceps brachii
Anterior – subscapularis
These structures can be compressed as a result of trauma, muscle hypertrophy or space occupying lesion; resulting in weakness of the deltoid and teres minor.
ERBS PALSY
- Erb’s palsy is muscle weakness in the arm or shoulder that can occur as a result of an injury sustained during birth or later in life.
- It’s most common in infants who injured their shoulders during delivery.
- Erb’s palsy is a nerve condition in the shoulder and arm that results in weakness or loss of muscle function. The brachial plexus is a group of five nerves that connect the spine to the arm and hand. These nerves allow your shoulder, arms and hands to feel and move. If these brachial plexus nerves don’t work well due to stretching or tearing, the condition is called a brachial plexus palsy.
- Erb’s palsy is the most common type of brachial plexus palsy.
SIGNS AND SYMPTOMS OF ERBS PALSY:
-Paralysis or limpness of the shoulder, arm and elbow. You can’t lift your arm away from your body or bend your elbow.
- Numbness or tingling in your arm or hand. These are also known as “burners and stingers.”
- A hand position known as ‘the waiter’s tip’ position. The palm of your hand points toward the back, and the fingers curl.
JOURNEY OF MUSCULOCUTANOEUS NERVE
The musculocutaneous nerve is the terminal branch of the lateral cord of the brachial plexus (C5, C6 and C7) and emerges at the inferior border of pectoralis minor muscle.
It leaves the axilla and pierces the coracobrachialis muscle near its point of insertion on the humerus. It gives a branch to this muscle. The musculocutaneous nerve then passes down the flexor compartment of the upper arm, superficial to brachialis but deep to the biceps brachii muscle. It innervates both these muscles and gives articular branches to the humerus and the elbow.
The nerve then pierces the deep fascia lateral to biceps brachii to emerge lateral to the biceps tendon and brachioradialis. It continues into the forearm as the lateral cutaneous nerve and provides sensory innervation to the lateral aspect of the forearm.
MUSCULOCUTAENEOUS NERVE SENSORY/CUTANEOUS FUNCTION
The musculocutaneous nerve gives rise to the lateral cutaneous nerve of forearm.
This nerve initially enters the deep forearm, but then pierces the deep fascia to become subcutaneous. In this region, it can be found close to the cephalic vein.
The lateral cutaneous nerve of forearm innervates the skin of the anterolateral aspect of the forearm.
JOURNEY OF THE MEDIAN NERVE
The median nerve is derived from the medial and lateral cords of the brachial plexus. It contains fibres from roots C6-T1 and can contain fibres from C5 in some individuals.
After originating from the brachial plexus in the axilla, the median nerve descends down the arm, initially lateral to the brachial artery. Halfway down the arm, the nerve crosses over the brachial artery, and becomes situated medially. The median nerve enters the anterior compartment of the forearm via the cubital fossa.
In the forearm, the nerve travels between the flexor digitorum profundus and flexor digitorum superficialis muscles. The median nerve gives off two major branches in the forearm:
Anterior interosseous nerve – supplies the deep muscles in the anterior forearm.
Palmar cutaneous nerve – innervates the skin of the lateral palm.
(The functions of these nerves are explored in more detail later in the article).
After giving off the anterior interosseous and palmar cutaneous branches, the median nerve enters the hand via the carpal tunnel – where it terminates by dividing into two branches:
Recurrent branch – innervates the thenar muscles.
Palmar digital branch – innervates the palmar surface and fingertips of the lateral three and half digits. Also innervates the lateral two lumbrical muscles.
THE MEDIAN NERVE MOTOR FUNCTIONS
The median nerve innervates the majority of the muscles in the anterior forearm, and some intrinsic hand muscles.
Anterior Forearm
In the forearm, the median nerve directly innervates muscles in the superficial and intermediate layers:
Superficial layer – pronator teres, flexor carpi radialis and palmaris longus.
Intermediate layer – flexor digitorum superficialis.
The median nerve also gives rise to the anterior interosseous nerve, which supplies the deep flexors:
Deep layer – flexor pollicis longus, pronator quadratus, and the lateral half of the flexor digitorum profundus (the medial half of the muscle is innervated by the ulnar nerve).
In general, these muscles perform pronation of the forearm, flexion of the wrist and flexion of the digits of the hand.
Hand
The median nerve innervates some of the muscles in the hand via two branches.
The recurrent branch of the median nerve innervates the thenar muscles – muscles associated with movements of the thumb. The palmar digital branch innervates the lateral two lumbricals – these muscles perform flexion at the metacarpophalangeal joints and extension at the interphalangeal joints of the index and middle fingers
THE MEDIAN NERVE SENSORY FUNCTIONS
The median nerve is responsible for the cutaneous innervation of part of the hand. This is achieved via two branches:
Palmar cutaneous branch – arises in the forearm and travels into the hand. It innervates the lateral aspect of the palm. This nerve does not pass through the carpal tunnel, and is spared in carpal tunnel syndrome.
Palmar digital cutaneous branch – arises in the hand. Innervates the palmar surface and fingertips of the lateral three and half digits.
RADIAL NERVE JOURNEY
The radial nerve is the terminal continuation of the posterior cord of the brachial plexus. It therefore contains fibres from nerve roots C5 – T1.
The nerve arises in the axilla region, where it is situated posteriorly to the axillary artery. It exits the axilla inferiorly (via the triangular interval), and supplies branches to the long and lateral heads of the triceps brachii.
The radial nerve then descends down the arm, travelling in a shallow depression within the surface of the humerus, known as the radial groove.
As it descends, the radial nerve wraps around the humerus laterally, and supplies a branch to the medial head of the triceps brachii. During much of its course within the arm, it is accompanied by the deep branch of the brachial artery.
To enter the forearm, the radial nerve travels anterior to the lateral epicondyle of the humerus, through the cubital fossa. The nerve then terminates by dividing into two branches:
DEEP BRANCH (motor) – innervates the muscles in the posterior compartment of the forearm.
SUPERFICIAL BRANCH (sensory) – contributes to the cutaneous innervation of the dorsal hand and fingers.
RADIAL NERVE MOTOR FUNCTIONS
The radial nerve innervates the muscles located in the posterior arm and posterior forearm.
In the arm, it innervates the three heads of the triceps brachii, which acts to extend the arm at the elbow. The radial nerve also gives rise to branches that supply the brachioradialis and extensor carpi radialis longus (muscles of the posterior forearm).
A terminal branch of the radial nerve, the deep branch, innervates the remaining muscles of the posterior forearm. As a generalisation, these muscles act to extend at the wrist and finger joints, and supinate the forearm.
RADIAL NERVE SENSORY FUNCTIONS
There are four branches of the radial nerve that provide cutaneous innervation to the skin of the upper limb. Three of these branches arise in the upper arm:
Lower lateral cutaneous nerve of arm – Innervates the lateral aspect of the arm, inferior to the insertion of the deltoid muscle.
Posterior cutaneous nerve of arm – Innervates the posterior surface of the arm.
Posterior cutaneous nerve of forearm – Innervates a strip of skin down the middle of the posterior forearm.
The fourth branch – the superficial branch – is a terminal division of the radial nerve. It innervates the dorsal surface of the lateral three and half digits and the associated area on the dorsum of the hand.
INJURIES TO DO WITH THE RADIAL NERVE
JOUNRNEY OF THE ULNAR NERVE
The ulnar nerve arises from the brachial plexus within the axilla region. It is a continuation of the medial cord and contains fibres from spinal roots C8 and T1.
After arising from the brachial plexus, the ulnar nerve descends in a plane between the axillary artery (lateral) and the axillary vein (medial). It proceeds down the medial aspect of the arm with the brachial artery located lateral.
At the mid-point of the arm, the ulnar nerve penetrates the medial fascial septum to enter the posterior compartment of the arm. It passes posterior to the elbow through the ulnar tunnel (small space between the medial epicondyle and olecranon). Here, it also gives arise to an articular branch which supplies the elbow joint.
In the forearm, the ulnar nerve pierces the two heads of the flexor carpi ulnaris, and travels deep to the muscle, alongside the ulna. Three main branches arise in the forearm:
Muscular branch – innervates two muscles in the anterior compartment of the forearm.
Palmar cutaneous branch – innervates the medial half of the palm.
Dorsal cutaneous branch – innervates the dorsal surface of the medial one and a half fingers, and the associated dorsal hand area.
At the wrist, the ulnar nerve travels superficially to the flexor retinaculum, and is medial to the ulnar artery. It enters the hand via the ulnar canal (Guyon’s canal). In the hand, the nerve terminates by giving rise to superficial and deep branches.
ULNAR NERVE SENSORY FUNCTIONS
There are three branches of the ulnar nerve that are responsible for its sensory innervation.
Two of these branches arise in the forearm, and travel into the hand:
Palmar cutaneous branch – innervates the medial half of the palm.
Dorsal cutaneous branch – innervates the dorsal surface of the medial one and a half fingers, and the associated dorsal hand area.
The last branch arises in the hand itself:
Superficial branch – innervates the palmar surface of the medial one and a half fingers.
