The Musculoskeletal System Flashcards
Function of the Pectoral Girdle
Protraction and retraction via the horizontal anticlockwise/clockwise rotation of the clavicles about sternoclavicular joint .
Elevation and depression via the clockwise/anticlockwise of the clavicles about SCJ in the vertical plane.
Superior and inferior rotation- angles the glenoid superiorly and inferiorly. Clockwise and anticlockwise rotation of scapula about acromioclavicular joint.
Function of the clavicle
Strut between scapula and axial skeleton that prevents tonal contraction of muscles from pushing it hard up against the thorax. This allows free gliding movement. along the ribcage.
Pathology of the Fractured Clavicle
All force moving up the upper loose limb will eventually be conducted to the clavicles. Since it is a weak bone, it will readily fracture at the midline- FOOSH injury.
Symptoms: sunken upper limb. Palpable raised ledge formed from the fracture.
Features of the scapula
Three angles: Superior, inferior, and glenoid fossa.
Three edges: thick lateral border, superior border, inferior border.
Three protuberances: Spine, acromion, coracle.
Three fossa: Subscapular fossa (anterior), supraspinous fossa, infraspinous fossa.
Features of the sternoclavicular joint
Saddle-shaped.
Stabilised by anterior and posterior sternoclavicular lig.
Joint capsule contains a full circular fibrocartilage disc- independent articulation of the two bones of the SCJ.
Stabilised externally by the subclavius m (subclavian groove & manubrium) and costoclavicular lig (coracoclavicular roughened area & first rib)
Features of the acromioclavicular joint
Arthrodial/plane joint, allowing only gliding.
Stabilised by superior and inferior AC lig. and the tendons of trapezius and deltoids running superior to the lig.
Joint protected by coracoclavicular ligaments, which bear weight of the free limb instead of the ACJ.
Features of the conceptual joint
Lubricated muscle-on-muscle interface between the subscapular fossa and the posterior surface of the thorax. Allows for smooth gliding movement when needed, but is a point at which the scapula can be braced to lock the girdle.
Pectoralis major
Anterior.
O: Sternum and clavicle.
I: Lateral lip of the intertubercular groove.
N: Lateral pectoral (clavicular head) and medial pectoral (sternocostal)
F: adduction and internal rotation of humerus. Protraction of unlocked scapula.
Pectoralis minor
Anterior.
O: Ribs 3-5.
I: Coracoid process.
N: Medial pectoral.
F: Unlocked scapula-depression of scapula.
Locked scapula- Locked scapula- active breathing by moving the ribcage.
Subclavius
O: Costal cartilage of rib 1.
I: Clavicles.
N: C5
F: Braces arm by resisting dislocating forces.
Serratus anterior
O: Medial border of the scapula on the anterior side.
I: Ribs 1-9. Sawtooth pattern at the anterior side.
N: Long thoracic nerve.
F: Contraction holds the scapula close to the thoracic. Division between upper and lower fibres.
- Lower: superior rotation at glenoid fossa- only lower section
- Entire: protraction of entire scapula.
Trapezius
Divided into superior, middle and inferior sections.
O: Sup- Nuchal line, mid- ligamentum nuchae, inf- Spinous processes of lower vertebrae.
I: Sup- Pos. face of clavicles, mid- acromion, pos- spine of scapula.
N: Accessory nerve.
F: Sup- Elevation of scapula. Mid- Retraction of scapula. Inf- Depression of scapula. Sup +inf: Superior rotation of the glenoid.
Latissimus dorsi
O: Transverse processes of the vertebra of the lower spine and sacrum. Muscle does not connect directly but via a thin, broad, aponeurosis.
I: Floor of intertubercular groove.
N: Thoracodorsal nerve
F: Adduction of humerus. Internal rotation of humerus.
Levator Scapulae
O: Transverse processes of C1-C4 (four ‘separate’ heads)
I: Superior angle of scapula.
N: Dorsal scapular
F: Elevation of scapula. Flexion of neck when scapula locked.
Rhomboid major and minor
O: Spinous process of C7-T5.
I: Medial border of the scapula- spine at superiormost point.
N: Dorsal scapular (Direct branch off C4).
F: Active- Retraction of scapula. Passive: Tonal contraction maintains position of scapula.
Dura Mater
Dense irregular connective tissue. Forms epidural space with vertebral column which is filled with fat and CT for mechanical protection.
Arachnoid mater
Thin avascular cell layer with network of collagen and elastic fibres. Forms subdural space with dura mater which contain interstitial fluid.
Pia mater
Highly vascularised inner layer of cuboidal/squamous epithelium. Forms denticulate ligaments with the other meninges which anchor the spinal cord.
Forms subarachnoid space with arachnoid mater- contains CSF.
Filum Terminale
A fibre of connective tissue made of all three layers of the meninges in order to anchor the spinal cord to the coccyx to avoid unnecessary movement.
Interna: Section inside the central canal of the spinal cord and the middle of the cauda equina.
Externa: Exposed section.
Borders of the Axilla Apex
Anterior: Clavicles
Medial: First rib.
Posterior: Superior border of the scapula.
Anterior wall of the Axilla
Superior to Inferior
Clavicle, subclavius, Costocoracoid lig, Pectoralis minor, suspensory ligament of the axilla.
Second layer: Pectoralis major.
Posterior wall of the Axilla
Supraspinatus, scapula, subscapularis, teres major, latissimus dorsi,
Medial wall of the Axilla
Serratus anterior and ribs.
Division pattern between spinal cord to anterior ramus
Nerves leave and enter the spinal cord as roots and converge to form a spinal nerve to leave the intervertebral foramen.
Spinal nerve divides into rami communicans (–> ANS), posterior rami (–> posterior structures), and anterior rami, which enter nerve plexi.
Divisions within the Brachial plexus.
Consists of the spinal nerves from C5-T1.
C5 and C6 forms the superior trunk. C7 forms the middle trunk. C8 and T1 forms the inferior trunk.
Superior trunk and middle trunk forms the lateral cord .
All three trunks form the posterior cord. Inferior trunk alone forms the medial cord.
Lateral cord alone forms musculocutaneous nerve.
Posterior cord alone forms the axillary nerve and the radial nerve.
Lateral cord and medial cord forms the median nerve.
Medial cord alone forms the ulnar nerve.
Clinical means to identify the nerves of the Axillary Plexus
The musculocutaneous nerve is identifiable as the nerve running between the biceps brachii and brachialis.
Tracing that nerve back will reach a point of division for the lateral cord. Following the other branch will lead to the median nerve.
Tracing the other branch leading to the median nerve will lead to the medial cord.
Tracing the other branch of the medial cord will lead to the ulna nerve.
Posterior cord is found posterior to the large axillary artery and forms a small branch called the axillary nerve which travels posteriorly through the quadrangular space. The rest of the posterior cord continues as the radial nerve.
Minor nerves of the Lateral Cord
Lateral pectoral nerve: Innervates clavicular head of pectoralis major.
Suprascapular nerve: Innervates supraspinatus and infraspinatus.
Minor nerves of the medial cord
Medial pectoral nerve: Innervates the sternocostal head and pectoralis minor.
Medial cutaneous nerves of the arm and forearm.
Minor nerves of the posterior cord
Upper subscapular nerve: Innervates subscapularis.
Thoracodorsal nerve: travels down posterior axillary wall and innervates latissimus dorsi.
Inferior subscapular nerve: Travels down posterior axillary wall and innervates subscapularis.
Musculocutaneous Nerve Innervation
Travels along groove between deltoid and pectoralis major.
Penetrates coracobrachialis and moves between Brachialis and biceps brachii. Becomes cutaneous at the lateral epicondyle to form lateral cutaneous nerve of forearm.
Median nerve innervation
List forearm muscles innervated
Moves from median side of humerus to lateral, then innervates 2/3 of muscles in the forearm.
Pronator teres, flexor carpi radialis, palmaris longus, lateral head of flexor digitorum profundus, flexor digitorum superficialis, pronator quadratus, flexor pollicis longus and thenar muscles.
Cutaneous innervation of the first 3.5 digits of the hand via the proper palmar digital nerves of the median nerve.
Ulnar nerve innervation
Moves down the medial side of the arm and behind the medial epicondyle. Innervates flexor carpi ulnaris and the ulnar head of the flexor digitorum profundus.
- Dorsal cutaneous branch provides cutaneous innervation to ulnar side of the posterior face of forearm.
- Deep branch ulnar nerve: Supplies 15/20 intrinsic muscles of the hand.
- Proper palmar digital nerves of the ulnar nerve provides cutaneous innervation of the 1.5 digits not innervated by the median nerve.
Deltoid Muscle
Ant/pos fibres are unipennate- tendon runs down one side of muscle. Mid fibres are multipennate- unipennate like structure but muscle found on both sides of tendon.
O: The anatomical horseshoe. Ant- clavicle, mid- acromion, pos- Spine of scapular.
I: Deltoid tuberosity of humerus.
N: Axillary nerve
F: Ant- Shoulder flexion. Internal rotation of arm.
Pos: Shoulder extension. External rotation of arm.
Mid: Abduction of arm.
Teres major
O: Inferior angle of the scapula in the infraspinous fossa.
I: Medial lip of intertubercular groove.
N: Inferior subscapular.
F: Internal rotation of the arm and extension of shoulder.
Teres minor
Part of the rotator cuff. O: Lateral border of the scapula. I: Inferior facet, greater tubercle. N: Axillary. F: Exteral rotation of humerus. Barrier against posterior dislocation of shoulder joint.
Brachialis
O: Lower half of the anterior face of humerus, including the intermuscular septa.
I: Ulnar tuberosity.
N: Musculocutaneous
F: Flexion of the elbow joint.
Biceps brachii
O: Long- Supraglenoid tubercle, after travelling up intertubercular septum and through the glenohumeral joint. Short- Coracoid process.
I: Radial tuberosity on the medial side of radius. Splits to form bicipital aponeuroses to blend with deep fascia of skin.
N: Musculocutaneous
F: Flexion of elbow joint. Supination of hand. Long head tendon provides tension against dislocation of the glenohumeral joint by pulling the humeral head into the glenoid fossa.
Short head can also act as a shunt muscle to reduce unnecessary movement.
How is the biceps brachii involved in the supination of the hand.
Pronation causes inserting tendon to wrap around the radius and build up tension. Contraction of biceps will pull on the tendon and ‘unwind’ it from around the humerus.
Coracobrachialis
O: Coracoid process.
I: Tuberosity opposite the deltoid tuberosity on the medial face of humerus.
N: Musculocutaneous
F: Adduction of humerus. Shunt muscle.
Mechanism of action of coracobrachialis as a shunt muscle
Role is to reduce unnecessary movement at a joint.
When load is applied to the glenohumeral joint, the there is a downward force pulling on the humerus which can lead to inferior dislocation. Coracobrachialis will contract to maintain the position of the humerus , hence functionally transferring tension to itself.
Triceps brachialis
Posterior extensor compartment of forearm.
O: Long- Infraglenoid tubercle. Lateral + Medial- Posterior face of humerous,
I: Olecranon of the ulna.
N: Radial
F: Elbow extensor. Long head is a shunt muscle.
Most of extensor function carried out by the medial head.
Axillary nerve innervation and path
Exits the axilla via the quadrangular space. Innervates the deltoid and teres minor. Becomes the lateral cutaneous nerve of the arm.
Radial nerve path in the arm
Travels posteriorly alongside the brachial profundus artery. Moves along radial groove of the posterior humerus.
Branches of the Axillary artery
Deep artery running medial to the humerus. Becomes brachial artery when inferior to the teres minor.
Forms collaterals which return to the brachial artery at the cubital fossa- backup blood supply via anastomosis.
Anterior and posterior cirumflex: Bends around the surgical neck of the humerus.
The posterior circumflex exits via the quadrangular interval.
Profunda brachii artery runs posteriorly and supplies the posterior of the arm.
Parameters of the cubital fossa
Medial border: Lateral border of pronator teres.
Lateral border: Medial border of brachioradialis
Roof: Bicipital aponeuroses.
Floor: Anterior face of brachialis.
Superior border: Arbitrary line between the two epicondyles.
Vasculature at the Cubital Fossa
Arteries: Brachial artery splits into ulnar and radial artery.
Veins: Basilic vein runs down the medial side and cephalic vein runs down the lateral side. Basilic vein forms median cubital vein, which moves medially to join the cephalic vein.
Median antebrachial vein form from the median cubital vein.
Venae comitantes: Runs adjacent to the deep brachial artery. Uses rhythmic distension of the arteries to push venous blood up.
Clinical significant of Cubital Fossa Veins
Basilic vein is the site of IV injections and where blood is taken from.
Tourniquet is applied above the fossa to limit venous return of blood, without cutting off arterial supply. Leads to accumulation of blood in the veins, which makes them bulge and easily visible.
Coracoacromial ligament
Connects coracoid and acromion. Forms roof of the glenohumeral joint to prevent superior dislocation.
Extracapsular ligament
Coracohumeral ligament
Capsular ligament connecting the coracoid with the lesser tubercle of the humerus.
Function: Suspension of the humerus in the anatomical position. When the arm is adducted, the ligament stretches over the top of the joint. This tightens it and creates tension in the ligament which holds it up.
Transverse humeral ligament
Connects the two lips of the intertubercular groove. Acts as a roof over the long head tendon of biceps brachii.
The glenohumeral ligaments
Weak, lateral thickenings found at the anterior of the joint capsule
Supraspinatus `
O: Spine of the spine of the scapula.
I: Superior facet of the greater tubercle.
N: Suprascapular nerve of the superior trunk.
F: Initiates humerus abduction.
Infraspinatus
O: Infraspinous fossa
I: Middle facet of greater tubercle.
N: Suprascapular nerve
F: External rotation of humerus.
Subscapularis
O: Subscapular fossa.
I: Lesser tubercle.
N: Subscapular nerves
F: Internal rotation of humerus.
Function of the Rotator Cuff
Physical barrier against dislocating motion.
Contracts to pull the head of the humerus medially into the glenoid fossa to prevent dislocation.
Abductors of Humerus
Supraspinatus. Middle fibres of deltoid.
Adductors of Humerus
Pectoralis Major, Latissimus Dorsi, Teres major, long head of triceps, anterior and posterior fibres of the deltoid, coracobrachialis.
Flexors of Humerus
Anterior fibres of the deltoid, coracobrachialis, clavicular head of pec major. biceps brachii
Extensors of the Humerus
Posterior deltoid, long head of triceps, teres major, sternocostal head of pec major, latissmus dorsi.
Humeroradial joint
Ball and socket like joint formed between the capitulum and the spherical indentation at the head of the humerus. Allows flexion and extension.
Held together by the collateral radial ligament, which attaches to the anular ligament of the radius in order to not limit rotatory movement.
Anular ligament padded from bone by sacciform recess of synovial membrane.
Radial fossa located above capitulum to allow full extent of motion by provide a hole for the head to fit.
Humeroulnar joint
Formed between the trochlea of the humerus and the trochlea notch on the head of the ulnar. This notch is formed by the coronoid process inferiorly, and the olecranon posteriorly.
Olecranon fossa located posteriorly above the trochlea . Allows full range of motion by providing a hole for the olecranon to fit into.
Held together by the ulnar collateral ligament/
Radioulnar joint
Lateral joint formed between the head of the radius and the radial notch on the ulna. Allows rotatory articulation of the radius around the ulna.
Bursae of the glenohumeral joint
Synovial membranes containing slippery synovial fluid.
Function: Provide interface between ligament and bone to prevent damage and rupture of the ligament by the roughened bone.
Subdeltoid: Protects middle fibres of deltoid from the greater tubercle.
Subacromial: Joined to subdeltoid bursa. Protects supraspinatus and infraspinatus tendons from the acromion.
Subscapular : Protects subscaprularis tendon from the humerus.
Subcoracoid: reduce friction between the tendons of the coracobrachialis, subscapularis and the short head of biceps (ie: any tendons which pass by the coracoid.)
Sacciform synovial membrane: Protects the tendon of the long head against the roughened intertubercular groove.
Why is the articular capsule of the glenohumeral joint loose?
Allows for full range of abduction/adducting movements. When abducted, the inferior section of the capsule is loose to provide room for extension.
Loose capsule provides limited resistance against dislocation, hence the need for the rotator cuff.
Distal radioulnar joint
Radioulnar notch formed from fibrous cartilage floor and the ulnar notch, Ulna head fits into the notch. Lateral hinge-like joint allowing only pronation/supination motion.
Pathology of the Elbow Joint
Posterior dislocation: Excessive force exerted on the forearm. If the humerus is locked, the olecranon will act as a lever to lift the humerus out of the trochlear notch.
Damage to olecranon fossa: Force is transmitted around the olecranon fossa, which are narrow strips of bone which will be easily fractured.
Interosseous membrane.
Sits between the radius and the ulna and separates the forearm into posterior and anterior compartments.
Fibres are obliquely and inferiorly angled.
Means of force transmission- if force is applied to the radius superiorly, the tension in the sheet of CT will drag the ulna along- hence force transmission occurs and the force applied over a wider area.
Hinge during supination/pronation.
Muscle attachment.
Carpal bones- clockwise from scaphoid- anatomical position.
Scaphoid, lunate, triquetrium, pisiform, hamate, capitate, trapezoid, trapezium
Anatomy of the Carpal Tunnel and Pathology of the Carpal Tunnel Syndrome
Passage formed over the wrist and positioned at the base of the thenar and hypothenar muscle masses.
Roof: Flexor retinaculum formed between the trapezium and the hook of the hamate.
Floor: Proximal carpals.
Carpal tunnel syndrome is when infection leads to the accumulation of exudate. Exudate accumulation leads to pressure buildup inside the carpal tunnel, which causes impingement on vasculature and innervation.
Retinaculum must be removed to relieve pressure if chronic.
Pronator teres
Superficial pronator
O: Medial supraepicondylar ridge. (Humeral head)
Medial side of coronoid process (ulnar head)
I: Lateral surface of the radius
N: Median nerve
F: Pulls the lateral face of the radius medially- internally rotates radius over the ‘top’ of the ulna.
Flexor Carpi Radialis
Superficial flexor O: Common tendon of the anterior compartment- medial epicondyle. I: Base of the second metacarpal. N: Median F: Flexion and abduction of wrist
Palmaris longus
Superficial flexor
O: Common tendon of the anterior compartment- medial epicondyle.
I: Palmar aponeurosis
N: Median nerve.
F: Flexion of the wrist joint. Tenses the palmar aponeurosis during contraction to resist shearing forces.
Flexor Carpi Ulnaris
Superficial flexor O: Common tendon of the anterior compartment- medial epicondyle. I: Base of the fifth metacarpal. N: ULNAR nerve F: Flexion and adduction of the wrist.
Flexor digitorum superficialis
Intermediate flexor.
O: Medial epicondyle and medial edge of the coronoid process. (Humeroulnar head)
Anterior oblique line of radius (radial head)
I: The end of the middle phalanx of all fingers.
N: Median- anterior interosseous
F: Flexion of the proximal interphalangeal joint and the metacarpophalangeal joint of the fingers.
Flexor digitorum profundus
Deep flexor
O: Complex, but stretches obliquely from the interosseous membrane superiorly and posteriorly towards the medial face of the ulnar head.
I: Palmar face of the distal phalanges of the fingers.
N: Lateral half- Anterior interosseous branch of the median nerve
Posterior half- ulnar nerve.
F: Flexion of the DIP joint and the MP joint.
Flexor pollicis longus
Deep flexor
O: Anterior surface of the radius and adjacent interosseous membrane- lateral to the FDP on the interosseous membrane.
I: Palmar surface of the distal phalanx of the thumb
N: Median- anterior interosseous
F: Flexion of the thumb at the IPJ and the MPJ.
Pronator Quadratus
Deep pronator O: Distal anterior surface of the ulna. I: Distal anterior surface of radius. N: Median- anterior interosseous F: Aids pronation.
Path and branching of the median nerve in the anterior compartment of the forearm
Forms a large branch called the anterior interosseous nerve which runs between the forearm bones, alongside the anterior interosseous artery.
Forms a palmar cutaneous branch just before the retinaculum which passes superficially to the retinaculum to provide cutaneous innervation to the lateral two thirds of the palm.
Past the retinaculum, the median nerve forms the common digital palmar nerves, which further divide into proper digital palmar nerves which innervate the first 3.5 digits.
A recurrent branch is also formed at the same level which innervates the thenar muscle mass.
Path and branching of the ulnar nerve in the anterior compartment of the forearm
Runs down the forearm on the medial side. Forms the palmar cutaneous branch halfway down the forearm which passes over the retinaculum to innervate the medial third of the palm.
Superficial ulnar branch forms similar digital divisions which lead to the innervation of the medial 1.5 digits.
Deep ulnar branch moves deeper into the palm via the hypothenar muscle mass.
Dorsal cutaneous branch forms before the retinaclum and provides cutaneous innervation to the medial third of the back of the hand.
Vasculature of the Anterior Compartment of the Forearm
Brachial artery branches into radial and ulnar branches after the cubital fossa.
The radial artery runs down the lateral side and joins with the radial recurrent artery. Forms no divisions until at the carpals where it splits into a superficial branch, with the main branch moving deeper .
The ulnar artery runs down the medial side and receives the anterior and posterior ulnar recurrent arteries. Forms a common interosseous branch which receives the interosseous recurrent before splitting coronally into anterior and posterior interosseous ulnar arteries which join posteriorly.
The proper ulnar branch proceeds down the median side until the carpals, where they split into a deep branch and the main superficial branch.
Properties of carpometacarpal joints
Fingers: Plane like joints, allowing only limited gliding movement.
Thumb: Saddle joint allowing flex/ext and abd/add, as well as limited rotational.
Describe the articulate movements of the thumb
Abduction/Adduction: Raising the thumb above the plane of the palm/ Returning the thumb to the plane of the palm.
Flexion/extension: Movement of the thumb towards/away from the palm.
Opposition: Rotation and adduction of the thumb to reach the other digits.
Properties of the metacarpophalangeal joints
Fingers: Condyloid joint that resembles a limited ball-and-socket joint. Allows a wider range of rotational and adduction/abduction.
Thumb: A kind of hinge joint consisting of two condyles. Allows only flexion and extension. Lateral movement further prevented by collateral ligaments.
THE METACARPOPHALANGEAL JOINT OF THE THUMB IS THE SAME AS THE IPJ OF THE FINGERS.
Ligaments of the phalanges
Collateral ligaments: to limit lateral movement at the IPJs.
Palmar ligaments: Connects collateral ligaments and provides a floor to the fibrous tunnel which houses the flexor ligaments.
Deep transverse metacarpal ligaments: Links the heads of the metacarpals. Prevents the over splaying of the fingers. NOT CONNECTED TO THE THUMB BECAUSE DUH.
Interaction between the tendons of the FDS and FDP.
The FPS tendon splits around the FDP tendon at the head of the middle phalanx and reconnects under the FDP tendon.
Dorsal interossei muscles.
O: The metacarpals of two adjacent fingers.
I: The base of the proximal phalanx, and the dorsal digital expansion hood of the more medial finger (out of two that the muscle originated from)
N: Deep ulnar branch.
F: Abduction of the digits II, II and IV at the MCPJs.
Palmar interossei muscles
O: Sides of the metacarpals.
I: DDEH of the same finger.
N: Deep ulnar branch.
F: Adduction of all digits except III- the third digit always abducts as it is the midline.
Adductor Pollicis
O: Lateral head- proximal phalanx of the third digit.
Oblique head- Base of the third metacarpal and the capitate.
I: DDEH of the thumb.
N: Deep ulnar branch.
F: Adduction of the thumb.
Lumbricles
O: The tendon of the FDP.
Bipennate (IV/V): Adjacent FDP tendons.
Unipennate (II/III): FDP tendon of the second and third digit.
I: DDEH.
N: Medial- Deep ulnar
Lateral- Digital branches of the median nerve
F: Contracts to extend IP joint in order to achieve a fine grip
Anatomy and Functions of the Dorsal digital extension hood
Fibrous sheet formed from the tendons of extensor digitorum and extensor pollicis, and attached to the middle phalanx.
Consists of lateral bands running down the sides up to the base of the distal phalanx, and the central band which runs on the posterior and up to the base of the middle phalanx.
Extensors will pull on the DDEH, which is attached to the phalanges and hence cause extension at the IPJs.
Allows for flexion at the MCPJ but extension at the IPJs to form a fine grip.