Unit 2 Flashcards
Brachial plexus
A complex of nerves which innervate the muscles of the upper limb, and the skin that overlies them.
Named nerves
Sorted from plexuses, these nerves come from multiple levels of the spinal cord to deliver motor and sensory innervation within a particular compartment of the limb.
What areas of the spinal cord are brachial plexus formed from?
Ventral rami C5-T1
When do plexuses form in embryos?
5-8 weeks gestation
The bone of the upper limb forms an axis which divides the limb transversely into two portions called:
- Preaxial portion
2. Postaxial portion
Describe the preaxial portion of the upper limb
The portion of the limb which lies on the cranial side of the long axis through the limb. (Thumb side)
Describe the postaxial portion of the upper limb
The portion of the limb which lies caudal to the long axis through the limb. (Pinky side)
During development, the preaxial and postaxial portions of the limb will each be further divided coronally into two compartments called:
- Anterior compartment
2. Posterior compartment
Anterior compartment is also considered to be ___ (flexor OR extensor) compartment.
Flexor compartment. Most of muscles in the anterior half of the limb flex the joints that they cross; when they contract, the angle between the bones decreases.
Posterior compartment is also considered to be ___ (flexor OR extensor) compartment.
Extensor compartment. Most of the muscles of the posterior aspect of the limb share the ability to extend at the joints (increase the angle between the bones).
What is a nerve plexus?
A collection of nerve fibers.
Which spinal nerves innervate the preaxial upper limb?
C5-C7
Which spinal nerves innervate the postaxial upper limb?
C8-T1
When is innervation established in upper limbs?
Innervation is established BEFORE the limb grows.
When the limbs grow longer during limb development, what happens to the innervation?
No matter how the limb’s shape changes, the innervation remains the same.
Each root of the brachial plexus branch from…
Ventral rami of spinal nerves from C5-T1.
They’re not the same thing as dorsal/ventral roots.
Roots of brachial plexus contain which fibers: Flexor (anterior), extensor (posterior), or both?
All 5 roots contain BOTH flexor (anterior) and extensor (posterior)
What are the 5 components of the brachial plexus?
- Roots
- Trunks
- Divisions
- Cords
- Named nerves
Roots C5-T1 branch into…
- Upper trunk: roots C5 and C6
- Middle trunk: root C7
- Lower trunk: roots C8 and T1
Trunks of brachial plexus contain which fibers: Flexor (anterior), extensor (posterior), or both?
All 3 trunks contain BOTH flexor (anterior) and extensor (posterior)
Each trunk branches into…
- Anterior division (3)
2. Posterior division (3)
Divisions of brachial plexus contain which fibers: Flexor (anterior), extensor (posterior), or both?
All 3 anterior divisions are ONLY flexor (anterior);
All 3 posterior divisions are ONLY extensor (posterior).
Each division branches into…
- Posterior cord: all posterior division fibers (C5-T1); lies posterior to axillary artery
- Lateral cord: anterior division fibers from upper and middle trunks (C5-C7); lateral to axillary artery
- Medial cord: anterior division fibers from lower trunk (C8-T1); medial to axillary artery
Cords of brachial plexus contain which fibers: Flexor (anterior), extensor (posterior), or both?
Posterior cord is ONLY extensor (posterior);
Lateral cord is ONLY flexor (anterior) from upper and middle trunks;
Medial cord is ONLY flexor (anterior) from lower lower trunk
Where are named nerves found in the brachial plexus?
Most named nerves branch from cords, but some branch directly from roots and trunks.
True/False: Named nerves can contain EITHER posterior division (extensor) OR anterior division (flexor) fibers, not both.
True
Draw the brachial plexus.
DO IT
Dorsal scapular nerve
Anterior or posterior division fibers?
What muscle(s) does it innervate?
Posterior division fibers from C5
Innervates rhomboid minor/major and levator scapulae
Long thoracic nerve
Anterior or posterior division fibers?
What muscle(s) does it innervate?
Posterior division fibers from C5-C7
Innervates serratus anterior muscle
Subclavian nerve
Anterior or posterior division fibers?
What muscle(s) does it innervate?
Anterior division fibers from C5-C6
Innervates subclavius muscle
Suprascapular nerve
Anterior or posterior division fibers?
What muscle(s) does it innervate?
Posterior division fibers from C5-C6
Innervates supraspinatus and infraspinatus
Lateral pectoral nerve
Anterior or posterior division fibers?
What muscle(s) does it innervate?
Anterior division fibers from C5-C6
Innervates pectoralis major
Medial pectoral nerve
Anterior or posterior division fibers?
What muscle(s) does it innervate?
Anterior division fibers from C8-T1
Innervates pectoralis minor/major
Upper subscapular nerve
Anterior or posterior division fibers?
What muscle(s) does it innervate?
Posterior division fibers from C5-C6
Innervates subscapularis
Thoracodorsal (middle subscapular) nerve
Anterior or posterior division fibers?
What muscle(s) does it innervate?
Posterior divisoin fibers from C6-C8
Innervates latissimus dorsi
Lower subscapular nerve
Anterior or posterior division fibers?
What muscle(s) does it innervate?
Posterior division fibers from C5-C6
Innervates subscapularis and teres major
Axillary nerve
Anterior or posterior division fibers?
What muscle(s) does it innervate?
Posterior division fibers from C5-C6
Innervates deltoid, teres minor, axilla
Musculocutaneous nerve
Anterior or posterior division fibers?
What muscle(s) does it innervate?
Anterior division fibers from C5-C7
Innervates anterior compartment of the arm
Radial nerve
Anterior or posterior division fibers?
What muscle(s) does it innervate?
Posterior division fibers from C5-T1
Innervates posterior compartment of the arm and forearm
Median nerve
Anterior or posterior division fibers?
What muscle(s) does it innervate?
Anterior divisoin fibers from C5-T1
Innervates anterior compartment of the forearm
Ulnar nerve
Anterior or posterior division fibers?
What muscle(s) does it innervate?
Anterior division from C8-T1
Innervates forearm and hand (hella muscles; should probably know which ones)
Medial cutaneous (antebrachial) nerve Anterior or posterior division fibers?
Anterior division fibers from C8-T1
Medial cutaneous (brachial) nerve of the arm Anterior or posterior division fibers?
What muscle(s) does it innervate?
Anterior division fibers from C8-T1
Hilton’s Law
In general, a joint is innervated by branches from all of the named nerves that supply muscles which cross that joint and which produce movement at the joint.
If C8 root is damaged, which function(s) would be affected?
Motor and sensory function
Segmental innervation
A given muscle is usually innervated by fibers from only one or two of the spinal cord levels that are contained within a given named nerve.
Describe the general segmental innervation pattern for the upper limb
Muscles that move more proximal parts of the limb are innervated by cranially higher spinal levels.
Dermatomal pattern of cutaneous innervation v. Named nerves pattern of cutaneous innervation
Dermatome cutaneous segments are innervated by one spinal nerve level; Named nerve cutaneous segments are innervated by more than one spinal nerve levels.
The cutaneous territory of named nerves will span multiple dermatomes.
Dermatome for thumb
C6
Dermatome for middle finger
C7
Dermatome for digit 5 (pinky)
C8
Outline on yourself (or someone else!) the 7 areas of skin innervated by specific named cutaneous nerves.
- Area innervated by branches of the axillary nerve.
- Area in arm and forearm innervated by branches of the radial nerve (find superficial radial nerve).
- Lateral antebrachial cutaneous nerve.
- Medial brachial cutaneous and medial antebrachial cutaneous nerves.
- Cutaneous distribution of branches of the median nerve in the hand.
- Cutaneous distribution of branches of the ulnar nerve in the hand.
- Cutaneous distribution of branches of the radial nerve in the hand.
Clinical significance of dermatomes and named cutaneous nerves.
An individual who damages their median nerve at the wrist (as in carpal tunnel syndrome) would likely show an area of sensory change consistent with the median nerve’s sensory territory in the hand. An individual who has a tumor involving spinal nerve C5 or C6, or any other level, would show sensory deficits consistent with patterns of dermatomes.
Find and identify the 4 major cutaneous veins on yourself (or someone else!)
- Cephalic vein (preaxial vein)
- Basilic vein (postaxial vein)
- Median cubital vein
- Dorsal venous arch or network
The main structures in the anterior neck consists of…
Branches from roots and trunks of brachial plexus (supraclavicular brachial plexus);
Subclavian artery
Located superior to clavicle.
The main structures in the axilla consists of…
Branches from cords and named nerves of brachial plexus (infraclavicular brachial plexus);
Axillary artery
Located inferior to clavicle.
What does the brachial plexus pass through to get from the anterior neck to the axilla? What are the muscular/bony boundaries of this space?
Cervicoaxillary canal/triangle (bounded by neck muscles laterally, the clavicle anteriorly, and the scapula posteriorly).
Axillary sheath
Connective tissue sheath that encases thee fat-filled space that the axillary artery and brachial plexus run through.
Name and identify the 6 main branches and their sub-branches of the axillary artery.
- Supreme thoracic artery
- Thoracoacromial trunk (Pectoral, deltoid, acromial, and clavicular branches)
- Lateral thoracic artery
- Subscapular artery (Thoracodorsal artery and Circumflex scapular artery)
- Anterior humeral circumflex artery
- Posterior humeral circumflex artery
Scapular arterial anastomosis
Collateral pathways (via arteries that supply posterior scapula) for if there is a blockage in the axillary artery in the axilla region between the thyrocervical trunk and the subscapular artery.
Arteries do not have valves, so they can flow backwards if needed!
What happens if there is a blockage in the artery proximal to the thyrocervical trunk or distal to the subscapular artery?
It would interrupt blood flow to the upper limb with no way around the blockage in those regions.
Explain the blood flow directions for scapular arterial anastomosis.
- Blood flow goes to posterior side of the scapula through either dorsal scapular artery OR the suprascapular artery.
- Within and deep to the muscles on the posterior scapula, branches of the above mentioned blood vessels anastomose with branches of the circumflex scapular artery.
- These will lead to the subscapular artery and then back into the axillary artery to reach the upper limb.
Postaxial polydactyly
Congenital physical anomaly of having an extra digit on postaxial side.
How are cords named in the brachial plexus?
Cords (lateral, medial, and posterior) are named in relation to the axillary artery.
What kind of fibers do named cutaneous nerves carry?
Sensory and sympathetic
Thoracic outlet syndrome and 3 ways for how it may occur.
Compression of nerves, arteries, or veins in the passageway of the cervicoaxillary canal/triangle. May occur when:
- Extra rib in cervical vertebrae
- Tumor in apex of lung
- Overdeveloped scalene muscles
The brachial plexus is located in the axilla. The 4 walls of the axillary fossa are:
- Humerus (lateral wall)
- Latissimus dorsi (posterior wall)
- Serratus anterior and ribs (medial wall)
- Pectoralis major (anterior wall)
Which vein is located on the preaxial muscle masses?
Cephalic vein
Which vein is located on the postaxial muscle masses?
Basilic vein
3 joints of shoulder
- Glenohumeral
- Acromioclavicular
- Sternoclavicular
3 joints of elbow (all within same joint capsule)
- Humeroulnar
- Humeroradial
- Proximal radioulnar
The 4 supraclavicular branches (that can be found on the diagram for our class) of the brachial plexus are…
- Dorsal scapular nerve
- Long thoracic nerve
- Subclavius nerive
- Supraspinatus nerve
Which spinal cord levels generally innervate hand joints?
C8-T1
Which spinal cord levels generally innervate elbow joints?
C6-C7
Which spinal cord levels generally innervate shoulder joints?
C5-C6
Which spinal cord levels generally innervate wrist joints?
C7-C8
What are the 3 bones of the shoulder joints?
- Clavicle
- Scapula
- Humerus
Sternoclavicular joints and acromioclavicular joints of the shoulder girdle are __axial joints.
Multiaxial
What is the name of the only bony articulation between the shoulder girdle and the axial skeleton?
Sternoclavicular joint
What are anterior and posterior sternoclavicular ligaments and what movement direction do they limit?
Capsular ligaments (thickenings of the joint capsule itself) of sternoclavicular joint located on anterior and posterior side.
Limits movement in all directions
What are interclavicular ligaments, what joint are they associated with, and what movement direction do they limit?
Extracapsular ligaments (located outside of joint capsule) of sternoclavicular joint that extend btwn sternal ends of two clavicles across the jugular (sternal) notch.
Limits excessive depression of shoulder girdle (good for not hitting brachial plexus)
What are costoclavicular ligaments, what joint are they associated with, and what movement direction do they limit?
Extracapsular ligament (located outside of joint capsule) of sternoclavicular joint that extends btwn first rib and clavicle bilaterally.
Limits unwanted superior movement (elevation) of clavicle, which occurs as a component of shoulder girdle elevation. It’s the fulcrum of many movements at SC joint.
What are coracoclavicular ligaments, what joint are they associated with, and what movement direction do they limit? What are the name of its parts?
Extracapsular ligament (located outside of joint capsule) of acromioclavicular joint that unites acromion of scapula and clavicle with its 2 ligaments: conoid and trapezoid.
Limits upward movement (elevation) of clavicle for STABILIZING clavicle.
Shoulder separation
Dislocation of acromioclavicular joint (usually due to trauma or tearing of acromioclavicular joint capsule and/or coracoclavicular ligament.
Which bone is the most frequently fractured bone in the body?
Clavicle
What are coracoacromial ligaments, what joint are they associated with, and what movement direction do they limit?
Extracapsular ligament (located outside of joint capsule) of glenohumeral joint that extends btwn coracoid process and acromion of scapula.
Limits upward dislocation of humeral head ( like a “roof”).
Shoulder girdle movements occur at which joints?
Sternoclavicular and acromioclavicular joints.
Elevation and depression of shoulder girdle occurs in what axis and what plane?
AP axis through SC joint
Coronal plane
Protraction and retraction of shoulder girdle occurs in what axis and what plane? What other name do these movements go by?
Vertical axis through SC joint
Horizontal plane
Also called abduction and adduction of scapula.
Shoulder girdle rotation (scapular, clavicular, and glenoid fossa rotation) occurs in what axis and what plane?
Upward rotation of glenoid fossa (lateral movement of inferior angle); downward rotation of glenoid fossa (medial movement of inferior angle).
Oblique axis through SC joint and scapular notch
Oblique plane
Scapulothoracic joint
Not a true joint, but rather an important plane of movement for the movements of the scapula (at AC and SC joints) along the body wall.
Rotational movements of scapula occur in a gliding plane between serratus anterior and subscapularis.
Which joint is commonly referred to as the “shoulder joint”?
Glenohumeral joint. It has the greatest ROM of any joint in the body (and also most unstable).
Glenohumeral joint articulation
Glenoid fossa of scapula and head of humerus
Glenohumeral ligaments, what type they are, and their functions
Capsular ligaments.
Limits movement when arm is aDducted.
What is the most frequently dislocated joint in the body?
Glenohumeral joint
What is the glenoid labrum and what does it do?
A fibrocartilaginous ring that attaches at the circumference of the glenoid fossa.
It deepens concavity of glenoid fossa by 50% which increases congruity and helps maintain a uniform film of synovial fluid across the joint surface.
What tendon unusually passes through the glenohumeral joint space to reach its attachment? Why?
Biceps brachii passes through on its way to the supraglenoid tubercle of the scapula.
This positioning of tendon helps prevent superior movement of the humeral head.
Shoulder dislocation
A displacement of the head of the humerus from the glenoid fossa, usually in an anterior or inferior direction. This may stretch or tear the shoulder joint capsule.
Scapulohumeral rhythm
Movements at the GH joint occur in concert with movements of the shoulder girdle, at the SC and AC joints for full aBduction.
Note: position of glenoid fossa shifts with EVERY movement of the shoulder girdle.
What movements does the scapulohumeral rhythm make significant contributions to? Breakdown the degree of movement btwn scapula rotation and glenohumeral joint.
Full abduction and full flexion of the arm (180°)
60° (scapula and clavicle rotation) + 120° (humerus aBduction at GH joint) = 180° (full abduction and flexion)
Accessory movements of shoulder joint necessary for full ROM at GH joint
An inferior gliding and lateral rotation of the humeral head that occurs as a component of aBduction.
These movements help prevent collision of head/tubercles of humerus and acromion during full aBduction.
3 passive (static) stabilizers of GH joint
- Glenoid labrum
- Glenohumeral ligaments
- Coracohumeral ligaments
3 dynamic stabilizers of GH joint
- Rotator cuff muscles
- Deltoid
- Tendon of long head of biceps brachii
What direction do dynamic stabilizers pull the head of humerus?
Medially to maintain good contact w/ articular surface of glenoid fossa.
What are bursae, where are they found, and what do they do?
A flattened sac of connective tissue lined by synovial membrane; the sac contains a small amount of synovial fluid.
Found btwn structures that are in close contact w/ each other and where movements occurs btwn structures.
Prevents friction and facilitates free movement btwn adjacent moving structures.
Subacromial bursa location
Btwn acromion process of scapula and superior surface of shoulder joint capsule. Allows the tendon of supraspinatus to slide freely under the acromion.
Subdeltoid bursa
Btwn deltoid muscle and humeral head, allowing deltoid muscle to freely glide over bone.
Bursitis
Condition associated with inflammation of a bursa.
Which shoulder joints have interarticular discs?
Sternoclavicular and acromioclavicular joints.
Which muscle mainly helps with maintaining stability of the GH joint?
Musculotendinous (rotator) cuff
Subclavian artery changes its name twice. At what points does it change its name and what names does it change to?
Subclavian artery passes under clavicle and into arm –> axillary artery passes pec minor –> brachial artery
What are the two major arteries that branch off the axillary artery underneath the pec minor muscle?
Thoracoacromial trunk and lateral thoracic artery
What are the fiber types of the brachial plexus and where are the cell bodies located?
Sensory (in DRG) Voluntary motor (Ventral horn) Postganglionic sympathetic (Sympathetic chain)
Axillary lymph nodes
Extensive lymph nodes and vessels surround the axillary vessels and their branches.
Shoulder girdle (or pectoral girdle) consists of these two bones
Scapula and clavicle
Main function of acromioclavicular joint
To link scapula and clavicle together form a functional unit (so shoulder girdle can move as a unit).
What kind of functional joint is the acromioclavicular joint?
Synovial joint (gliding movement of about 15 degrees; moves when scapula moves/acromion rotates on clavicle)
What are superior and inferior acromioclavicular ligaments, what joint are they associated with, and what movement direction do they limit?
Connects lateral end of clavicle to the upper surface of acromion in acromioclavicular joint.
Link bones together.
Effects of paralysis of trapezius
- Exaggerated shoulder girdle depression, at rest.
- Some weakness in shoulder girdle elevation.
- Weakened retraction of shoulder girdle.
- Diminished ability to fully aBduct and flex the arm bc of weakness in ability to upwardly rotate glenoid fossa (scapulohumeral rhythm).
Effects of paralysis of rhomboids
- Scapula has tendency to protract or move anteriorly around body wall as a result of weight of free limb.
- Loss of rhomboid function weakens ability to extend and aDduct arm against resistance.
Effects of paralysis of levator scapulae
Hard to discern bc other muscles can almost completely assume its function.
Effects of paralysis of serratus anterior
- Downward rotation of glenoid fossa from weight of arm (affects aBduction and flexion)
- Posterior movement of medial border of scapula (“winging” scapula)
Effects of paralysis of pectoralis minor
Weakness in downward rotation of glenoid fossa (during extension and aDduction of shoulder against resistance).
Effects of paralysis of deltoid
Significantly limit shoulder joint aBduction.
Rotator cuff can do it, but it’s not as strong.
Rotator cuff consists of these 4 muscles
- Supraspinatus
- Infraspinatus
- Teres minor
- Subscapularis
3 functions of interarticular discs at SC joint
- Increases congruity
- Shock absorber
- Creates 2 separate joint spaces = increased ROM
Name the muscles
Axial skeleton –> scapula/clavicle
(Crosses SC and AC joints)
- Trapezius
- Serratus anterior
- Levator scapulae
- Rhomboid major/minor
- Pectoralis minor
- Subclavius
Name the muscles
Scapula/clavicle –> proximal humerus
(Crosses GH joints)
- Deltoid
- Teres major
- Supraspinatus
- Infraspinatus
- Teres minor
- Subscapularis
Name the muscles
Axial skeleton (big muscles) –> humerus
- Pectoralis major
2. Latissimus dorsi
Name the muscles
Scapula –> (distal) humerus/forearm
- Biceps brachii
- Coracobrachialis
- Triceps brachii
Which rotator cuff is most likely the first to be torn?
Supraspinatus
2 neurovascular spaces in posterior shoulder, their boundaries, and what travels through
Triangular space:
- Bordered superiorly by Teres minor, inferiorly by Teres major, and laterally by Triceps LH
- Contains scapular circumflex artery
Quadrangular space:
- Bordered medially by Triceps LH, superiorly by Tmin, inferiorly by Tmaj, laterally by humerus
- Contains posterior humeral circumflex artery and axillary nerve
2 types of shoulder joint dislocations
- Tears in anterior component of rotator cuff (subscapularis tendon) as a result of violent anterior movement of humeral head.
- Weakness or paralysis of rotator cuff muscles and muscles that maintain normal position of shoulder girdle (like traps and serratus anterior) can result in chronic displacement of humeral head in inferior direction (there’s no rotator cuff muscle that strengthens inferior component of joint capsule).
Which 2 muscles cause upward rotation of glenoid fossa? Which directions are they pulling?
Trapezius pulls:
- Lateral spine and clavicle superiorly (upper fibers)
- Medial spine inferiorly (lower fibers)
Serratus anterior pulls:
- Inferior angle laterally
Describe the deltoid’s role in shoulder abduction
Pull changes w/ position of humerus.
- From 0-90°, deltoid aBducts (pulls superiorly on humerus)
- Past 90°, deltoid holds head of humerus against glenoid fossa (pulls medially on humerus)
Describe the rotator cuff muscles’ role as musculotendinous cuffs
- Dynamic stabilizers of GH joint
- Tendons blend w/ and reinforce joint capsule
- Hold humerus head in glenoid fossa
- Contract as a unit
- Resist dislocation of joint
Effects of paralysis of pectoralis major
No significant disabilities associated with paralysis of the muscle.
Extensors of GH joint
- Deltoid (posterior)
- Teres major
- Latissimus dorsi
- Triceps (long head)
- Pec major (sternal portion)
Flexors of GH joint
- Deltoid (anterior)
- Pec major (clavicular portion)
- Coracobrachialis
- Biceps brachii (both heads)
Downward rotators of scapula
- Levator scapulae
- Rhomboids
- Pec minor (lower)
Upward rotators of scapula
- Traps (upper and lower fibers)
- Serratus anterior
Depressors of shoulder girdle
- Subclavius
- Pec minor (lower)
- Traps (lower)
- Serratus anterior (lower)
- Lats (lower)
Elevators of shoulder girdle
- Traps (upper)
- Levator scapulae
Retractors of shoulder girdle
- Rhomboids
- Traps (middle fibers)
- Lats (upper fibers)
Protractors of shoulder girdle
- Pec minor
- Pec major
- Serratus anterior
Humeroulnar joint
An elbow joint whose articulation is btwn trochlea of humerus and trochear notch of ulna. Hinge joint, which moves around transverse axis only.
Stabilizes elbow joint and limits side-to-side movements.
Humeroradial joint
A biaxial elbow joint whose articulation is btwn capitulum of humerus and head of radius. Hinge joint when humeroulnar joint is moving; pivot joint when proximal radioulnar joint is moving.
Collateral ligaments
Two ligaments at the sides of humeroradial joint: radial (or lateral) collateral ligament and ulnar (or medial) collateral ligament.
Limits side-to-side (aBduction and aDduction) and hyperextension movements at elbow joint.
Radioulnar joints
3 articulations (proximal, middle, and distal) which articulates between radial head and radial notch of ulna. They’re all uniaxial, pivot joints that move all together and functionally considered to be one joint.
Helps change position of palm of hand (pronation and supination).
What kind of joint is the proximal radioulnar joint?
Located btwn head of radius and radial notch of ulna; it’s a pivot synovial joint in which the radial head spins the radial notch of ulna
What kind of joint is the middle radioulnar joint?
Formed by interosseous membrane btwn radius and ulna; it’s a fibrous joint. It’s taught in supination and relaxed in pronation.
What kind of joint is the distal radioulnar joint?
Located btwn head of ulna and ulnar notch of radius; it’s a synovial joint that has a fibrocartilaginous interarticular disk (which connects styloid process of ulna head and ulnar notch of radius).
Pulled elbow
Sudden pull on pronated forearm, sublaxation of radial head inferiorly out of annular ligament.
Kids under 5 not too bad and can be replaced. Happens to them bc their radial head is small enough to pop out of annular ligament. Can be replaced back to proper position.
Annular ligament
Proximal radioulnar joint has an annular ligament that encircles head of radius and attaches to either side of radial notch at ulnar.
Allows radial head to spin freely (ulna fixed into position w/ humerus), during pronation/supination, within osseofibrous ring formed by annular ligament and radial notch of ulna.
Proximal radioulnar’s interosseus membrane is oriented which way from radius to ulna
It runs inferomedially from radius to ulna
This is clinically significant b/c when you fall, you land on pronated forearm where membrane is in a “loose” position. This allows some “give” so radius and ulna can move on each other w/o breaking. Ulna also absorbs some of the force on radius
At all three radioulnar joints, how do radius and ulna move around each other.
Radius moves around fixed ulna.
When supinated, the elbows are parallel; when pronated, the bones are crossed
Medial and lateral intermuscular septa
Extends from brachial fascia inward to humerus
Separated by medial and lateral intermuscular septa, what does the anterior (flexor) compartment of the arm contain?
3 flexor muscles innervated by musculocutaneous nerve: 1. Biceps brachii 2. Coracobrachialis 3. Brachialis Also contains brachial artery
Median and ulnar nerves travel through anterior compartment of arm to reach forearm.
Separated by medial and lateral intermuscular septa, what does the posterior (extensor) compartment of the arm contain?
Contains triceps brachii, innervated by radial nerve and profunda brachii artery.
Name 4 large named nerves from the cords of brachial plexus that travel through the length arm
- Radial
- Ulnar
- Median
- Musculocutaneous
2 arteries in the arm:
- Brachial artery
2. Profunda (deep) brachial artery
Which nerve becomes the lateral antebrachial nerve?
Musculocutaneous nerve
Which nerve runs with the deep brachial artery in the arm?
Radial nerve
Which nerves passes posterior to the medial epicondyle of the humerus?
Ulnar nerve
What passes through carpal tunnel?
Flexor digitorum superficialis tendons (4)
Flexor pollicis longus tendons (4)
Flexor digitorum profundus tendons (1)
Median nerve
Which two muscles are the “getting handcuffed” muscles?
Teres major and latissimus dorsi
Which part of the rotator cuff is most commonly torn? What is a result of this?
Tendon of supraspinatus, this allows translation of humeral head in joint capsule (which affects GH joint mechanics)
Radiocarpal joint
Btwn radius and proximal row of carpal bones
Mid-carpal joint
Btwn proximal and distal rows of carpal bones
Radiocarpal joint and mid-carpal joint move separately or together?
These two joints ALWAYS moves together. This allows for larger ROMs than each joint would have individually.
In shoulder dislocations, head of humerus can be displaced from glenoid fossa in which direction?
Anterior, posterior, inferior
Pectoralis major and latissimus dorsi can move which shoulder joints?
SC, AC, and GH joints (all 3!)
What advantage does the pectoralis get in having a twisted tendon attached to the humerus?
Fibers from clavicular head insert inferior to fibers of sternocostal head to give it a good mechanical advantage to flex.
Explain the 2 components of adduction for latissimus dorsi
- Lats pull directly on humerus (act on GH joint)
2. Lats pull on inferior angle of scapula (acts on SC joint –> downward rotation of glenoid fossa)
The long head biceps brachii’s tendon runs through what? What’s it held down by?
Runs in a groove in the shaft of humerus (intertubercular or bicipital groove). It is held down by transverse humeral ligament. Travels through GH joint covered w/ synovial sheath and inserts on supraglenoid tubercle of scapula.
The long head of triceps passes btwn which 2 muscles? It inserts on what?
Teres major and teres minor; inserts on infraglenoid tubercle of scapula.
Movements around the wrist occur around how many axes?
Two axes:
- Abduction/adduction (AP axis)
- Flexion/extension (transverse axis)
NO ROTATION AT THE WRIST JOINT! (Supination/pronation is at the forearm and 3 radioulnar joints, NOT wrist)
Ulnar and collateral ligament at the wrist is different than the ones in the elbow joint because
The ones at the wrist limit, but do not prevent, movements in the coronal plane.
(At elbow joint, it pretty much prevents this from happening)
The intercarpal joints are examples of which type of synovial joint?
Gliding (plane) joint
Carpal tunnel
Formed by concave, anterior surface of carpal bones and an extremely dense band of CT called flexor retinaculum
Flexor retinaculum attaches to what?
Medially to pisiform bone and hook of hamate and laterally to tubercles of trapezium and scaphoid.
Flexor retinaculum does what?
Holds the flexor tendons close to the bones of the forearm and wrist, preventing bowstringing of tendons when muscles contract.
The CMC joint of the thumb is what kind of synovial joint?
Multiaxial saddle joint that can do flexion/extension, abduction/adduction, and small amount of medial/lateral rotation.
What makes the thumb different from other digits?
Most of the movements of the thumb occur at CMC joint
Adduction/abduction of digits 2-5 occur at what axis?
AP axis
Adduction/abduction of 1st digit occurs at what axis?
Transverse axis
Flexion/extension of the metacarpophalangeal joints of digits 2-5 occurs around which axis?
Transverse axis
Flexion/extension of the metacarpophalangeal joint of digit 1 occurs around which axis?
AP axis
What kind of synovial joints are metacarpophalangeal (MP) joints of digits 2-5?
Biaxial, condyloid joints btwn heads of metacarpals and bases of proximal phalanges. Can do flexion/extension around transverse axis and abduction/adduction around AP axis
What’s the degree of movement for metacarpophalangeal digit 1?
Uniaxial (only flexion/extension)
What’s the degree of movement for all interphalangeal joints?
Uniaxial (flexion/extension)
What kind of ligaments are at MP joints?
Medial and lateral collateral ligaments (limits abduction/adduction)
Dorsal and palmar ligaments (limit hyperflexion/hyperextension)
What’s happening when you limit abduction at the MP and IP joints by flexing?
Strengthen the grips of your hand
Separated by septa, what does the anterior (flexor) compartment of the forearm contain?
Flexor muscles
Median and ulnar nerves
Radial and ulnar arteries
Anterior interosseus artery.
Common extensor origin
Lateral epicondyle of humerus
Common flexor origin
Superior to medial epicondyle of humerus
What happens if you have loss of function of primary movers of elbow?
Weak or “minor” functions of forearm muscles can be exploited clinically to compensate for loss of function of primary movers of elbow since they cross the elbow joint.
The radial and ulnar contribute to the superficial palmar arch and deep palmar arch in the hands. This helps provide ___ within the hand.
Collateral circulation
For forearm and hand, there are 4 general grouping of muscles and their nerve supply
- Muscles in posterior (extensor) compartment of forearm innervated by radial nerve.
- Most muscles in anterior (flexor) compartment of forearm innervated by median nerve.
- Most muscles of hand innervated by ulnar nerve
- There are some important exceptions to these general schemes.
The elbow joint capsule surrounds all 3 articulations of the elbow but not the radius, describe why this is clinically important. Describe it’s thickness around the articulations.
Allows radius to spin. It’s LOOSE anteriorly and posteriorly;
THICKENED medially and laterally to prevent ab/adduction.
The elbow flexor muscles produces ____ contraction in order to bring a weight down from a flexed position.
eccentric
Which head is the tricep’s strongest elbow extensor?
Lateral head
What’s the most powerful elbow flexor muscle?
Brachialis
What’s the most powerful muscle acting around the vertical axis of proximal radioulnar joint?
Biceps brachii (works optimally to supinate arm when elbow is flexed)
2 accessory flexor muscles are
- Brachioradialis
2. Pronator teres
How do joints (e.g., elbow and shoulder joints) get nutrients?
All arteries in arm send branches to form an anastomosis around the elbow/shoulder.
Extrinsic hand muscles
Muscles of the forearm that act on the hand
Intrinsic hand muscles
Muscles that attach entirely within the hand
Pronator teres muscle crosses which joint?
Elbow joints
The neurovascular plane of the forearm between layers 2 and 3 contain what?
Radial and ulnar arteries and median and ulnar nerves
What happens to the hand’s resting position if a function were to be affected?
The loss of function in one muscle will result in the hand resting in a position determined by the injured muscle’s antagonist.
So if there’s a flexor tendon injury, the affected finger’s resting position will be extended instead of naturally flexed
Fibrous digital sheaths prevent what?
Bowstringing
Synovial sheaths in digits prevent what?
Friction during gliding
What structures in the hand help facilitate friction-free gliding of tendons in the hand?
Digital synovial sheaths Radial bursa (made of synovial membrane) Ulna bursa (made of synovial membrane)
List the carpal bones
Scaphoid Lunate Triquetrum Pisiform Trapezium Trapezoid Capitate Hamate
(Sam likes to push the toy car hard)
Explain the blood supply to scaphoid
- Radial artery branch is on radial side of forearm, passes to wrist, and branches to scaphoid bone.
- Enters scaphoid at distal pole of bone
What happens to blood supply if there’s a fracture of scaphoid bone?
Blood supply to proximal scaphoid can be disrupted and result in avascular necrosis
What structures does flexor retinaculum extend between in hands?
Tubercles of scaphoid and trapezium; pisiform and hook of hamate
Where is the radiocarpal joint?
Between radius and 3 carpal bones
Where is the midcarpal joints?
Between midcarpals and carpals
Radioulnar joint can do what movements and move about what axes?
Flexion/extension (transverse axis)
Abduction/adduction (AP axis)
CANNOT rotate.
Midcarpal joint can do what movements and move about what axes? What bone do these axes pass through?
Flexion and extension (transverse axis)
Abduction/adduction (AP axis)
NO ROTATION.
Capitate bone
Ulnar (medial) collateral ligament of elbow, radiocarpal, and midcarpal joints limit what movement?
ABduction and hyperextension
Radial (lateral) collateral ligament of elbow, radiocarpal, and midcarpal joints limit what movement?
ADduction and hyperextension
What are the joints of the wrist?
Radioulnar joint and midcarpal joint
Describe the carpometacarpal (CMC) joints for each metacarpal
Metacarpal 5 is less constrained by carpals and help w/ grasping (flexion/extension and lateral rotation).
Metacarpal 2, 3, and 4 are fixed btwn adjdacent carpals. There’s little movement at CMC
Metacarpal 1 is primary joint of movement. It’s a multiaxial, saddle joint
What axis and plane is flexion and extension of thumb?
AP axis/coronal plane
What axis and plane is adduction and abduction of thumb?
Transverse axis/sagittal plane
What axis and plane is medial and lateral rotation of thumb?
Vertical axis/transverse plane
What is opposition of thumb?
A combination of movements (abduction, flexion, medial rotation, and adduction)
Describe the metacarpophalangeal (MCP) joints for each metacarpal
Digits 2-5 are biaxial condyloid joints (fexion/extension and abduction/adduction).
Digit 1 is uniaxial hinge joint (flexion/extension)
Which axis does the AP axis go through for abduction/adduction in metacarpophalageal joints?
Midline of hand (3rd digit)
What is finger circumduction of MCP joints?
A combination of flexion, extension, adduction, and abduction allows fingers to “draw” a circle, but it’s NOT rotation.
Condyloid joints cannot rotate!
What ligaments do MCP joints have?
Medial and lateral collateral ligaments
Dorsal and palmar ligaments
If you touch the hot surface w/ tip of index finger, flexor muscles of arm will contract, causing upper limb to recoil, as part of simple reflex arc btwn sensory input and motor output.
Sensory input from skin at tip of index finger is carried by which nerve?
Motor output to anterior (flexor) compartment of arm is carried by?
Sensory input carried by median nerve.
Motor output carried by musculocutaneous nerve.
Would a stab wound to anterior neck endanger trunks or cords of brachial plexus?
Trunks
Hypertrophy of anterior scalene muscles can compress which segment of the brachial plexus?
Roots
Where are the roots of brachial plexus located?
Between anterior and middle scalene muscles
Lateral cord of brachial plexus has fibers from which spinal levels?
C5-7
Trapezius actions
Upper fibers:
- Elevate shoulder girdle
- Retract shoulder girdle
- Upward rotation of glenoid fossa (lateral spine and clavicle superiorly)
Middle fibers:
- Retract shoulder girdle
Lower fibers:
- Depress shoulder girdle
- Retract shoulder girdle
- Upward rotation of glenoid fossa (medial spine inferiorly)
Rhomboids actions
Fixed axial attachments:
- Retract shoulder girdle
- Downward rotation of glenoid fossa
Levator scapulae actions
Fixed axial attachments:
- Elevate shoulder girdle
- Downward rotation of glenoid fossa
Serratus anterior actions
Fixed scapula:
- Elevates ribs (accessory respiratory muscle)
Fixed ribs:
- Depresses shoulder girdle (lower fibers)
- Protracts shoulder girdle (holds scapula against ribcage)
- Upward rotation of glenoid fossa (inferior angle laterally)
- Scapular stabilization
Pectoralis minor actions
Fixed scapula:
- Elevates ribs 3-5
Fixed ribs:
- Depresses shoulder girdle
- Protracts shoulder girdle
- Downward rotation of glenoid fossa (assists rhomboids)
Subclavius actions
- Stabilizes clavicle for UL movements
- Depresses clavicle
Describe the course of nerves arorund humerus
Axillary n: around surgical neck of humerus
Radial n: around shaft of humerus (radial groove)
Ulnar n: behind medial epicondyle of humerus
Describe the attachment of the ulnar (medial) collateral ligament at the elbow joint
Medial epicondyle of humerus –> ulnar coronoid and olecranion processes
Describe the attachment of the radial (lateral) collateral ligament at the elbow joint
Lateral epicondyle of humerus –> ulna and annular ligament (not to radius bc we don’t want to limit its ability to spin around)
What movement at elbow joint occurs at vertical axis?
Pronation and supination (proximal radioulnar [pivot] and humeroradial [pivot])
What movement at elbow joint occurs at AP axis?
No movement around this axis
What movement at elbow joint occurs at transverse axis?
Flexion and extension (humeroulnar [hinge] and humeroradial [hinge])
Describe “Tommy John” surgery. Tendons from which muscles are usually used?
Replacing a torn ulnar collateral ligament w/ tendon from “unused” muscle in forearm of leg (usually palmaris longus or plantaris muscle)
Describe supination/pronation at distal radioulnar joint with regards to its articular disk
Radius rotates around FIXED ulna; articular disk rotates with radius and sweeps over ulna.
What muscles move the radioulnar joints?
Supinators:
- Supinator
- (Biceps)
- (Brachioradialis)
Pronators:
- Pronator teres
- Pronator quadratus
- (Bradioradialis)
What are the boundaries of cubital (elbow) fossa? What structures does it contain?
Triangle boundaries:
- Line btwn humeral epicondyles
- Pronator teres
- Brachioradialis
Contents (lateral to medial; TAN):
- Biceps Tendon
- Brachial Artery
- Median Nerve
- (Superficial vein: median cubital vein)
Forearm flexors are considered to be weak elbow flexors since they cross the humeroulnar joint. What nerve are they mainly innervated by?
Median nerve
Extensor expansion, or extensor hood
Extensor digitorum tendons attach to digits by expanding at MP joints into flattened tendinous “hoods” over the dorsum of the entire length of the digit (unlike the “regular” tendinous way, which is to insert into the bone)
This is why it’s almost impossible to independently extend the PIP and DIP joints of a particular digit.
Extrinsic thumb muscles and their main function
The three “pollicis” muscles of deep extensors:
- Abductor pollicis longus
- Extensor pollicis brevis
- Extensor pollicis longus
Return thumb back into anatomical position from opposition (reposition).
What axis of the wrist joint passes through the anatomical snuffbox?
Transverse axis
Extensor retinaculum function
Holds extensor close to bones of forearmr to prevent bowstringing of tendons during extension and increases mechanical advantage of their contraction
What is a prominent structural difference between extensor retinaculum and flexor retinaculum?
Flexor retinaculum has a single canal (carpal tunnel) for all tendons which pass deep to it.
Extensor retinaculum is bound down to radius and ulna at intervals and forms six separate canals for groups of tendons
Which muscles of the lateral group of extensor muscles can also flex the elbow? Why can they flex the elbow?
All 3 muscles of lateral group because they all cross ANTERIOR to transverse axis of elbow joint.
- Brachioradialis (strong elbow flexor)
- and 3. Extensor carpi radialis longus and brevis (weak elbow flexors)
What muscles are in layer one of forearm flexors?
Superficial flexors:
- Pronator teres
- Flexor carpi radialis
- Palmaris longus
- Flexor carpi ulnaris
Palmar aponeurosis
Attached to palmaris longus. It’s a tough layer of CT which slips to each digit and forms compartments in hand. It’s important for grip.
What muscles are in layer two of forearm flexors?
Flexor digitorum superficialis
What structures are in the neurovascular bundle of the forearm and where can the bundle be found?
Radial artery, median nerve, ulnar nerve, and ulnar artery. Found btwn layers 2 and 3 of forearm muscles.
Anterior interosseus nerve branches from which nerve and supplies which muscles in the forearm?
Branches from median nerve and supplies deep flexors (flexor pollicsi longus and flexor digitorum profundus of digits 2 and 3) of forearm.
What muscles are in layer three of forearm flexors?
Deep flexors:
- Flexor pollicis longus
- Flexor digitorum profundus
What muscles are in layer four of forearm flexors?
- Pronator quadratus
Median nerve territory of forearm consists of:
Palmaris longus, flexor carpi radialis, and pronator teres (layer 1)
Flexor digitorum superficialis (layer 2)
Flexor pollicis longus and flexor digitorum profundus (radial half) (layer 3)
Ulnar nerve territory of forearm consists of:
Flexor carpi ulnaris (layer 1)
Flexor digitorum profundus (ulnar half) (layer 3)
Ulnar nerve and median nerve travels through which tunnel in the wrist?
Ulnar nerve = Guyon’s canal
Median nerve = carpal tunnel
What kinds of fibrous digital sheaths can be found in the hand?
Annular ligaments and transverse metacarpal ligament
Where are synovial tendon sheaths found in the hand?
Can be found in each digit within fibrous sheaths. The synovial tendon sheath in digit 5 is continuous with the ulnar bursa.
Trigger finger
“Locked” bent position of finger occurs when the gliding mechanism in finger is not working bc of an inflamed tendon that makes it too difficult for it to slide easily through annular ligaments.
Which muscles of the flexor forearm can pronate at radioulnar joints?
Pronator teres
Pronator quadratus
Which muscles of the flexor forearm can flex elbow?
All of them :O
Which muscles of the flexor forearm can flex wrist?
Flexor carpi radialis Palmaris longus Flexor carpi ulnaris Flexor digitorum superficialis Flexor pollicis longus Flexor digitorum profundus
Which muscles of the flexor forearm can adduct wrist?
Flexor carpi ulnaris
Which muscles of the flexor forearm can abduct wrist?
Flexor carpi radialis
Which muscle tenses the palmar aponeurosis?
Palmaris longus
Which muscles of the flexor forearm can flex digits?
Flexor digitorum superficialis
Flexor digitorum profundus
Flexor pollicis longus
Name the 4 four compartments within the hand that are separated by connective tissue septa which project inwardly from the palmar aponeurosis
- Thenar
- Hypothenar
- Palmar (central)
- Adductor
Extensor forearm muscles are all innervated by which nerve?
Radial nerve
General functions of extensor forearm muscles crossing the elbow
Flex*/extend elbow
Extensor carpi radialis longus and brevis
General functions of extensor forearm muscles crossing the wrist joints
Flex*/extend wrist
Abduct/adduct wrist
General functions of extensor forearm muscles crossing the 1st CMC joint
Extend thumb
Abduct thumb
General functions of extensor forearm muscles crossing the MP joints
Extend MP
General functions of extensor forearm muscles crossing the PIP and/or DIP joints
Extend PIP and/or DIP
Name the lateral muscles of extensor forearm; their origin; their innervation
Brachioradialis
Extensor carpi radialis longus
Extensor carpi radialis brevis
Originate superior to elbow (supracondylar ridge)
Innervated by Radial N.
Lateral extensor muscles of the forearm actions and where do they cross in relation to the transverse axis
All 3 extensor muscles cross anterior to transverse axis of elbow:
- Brachioradialis (strong elbow flexor)
- Extensor carpi radialis longus and brevis (weak elbow flexors
Extensor carpi radialis longus and brevis cross posterior to transverse axis:
- Extend wrist
Lateral extensor muscles of the forearm actions around vertical axis
Brachioradialis acts on radioulnar joints to return forearm to “handshake” position
Lateral extensor muscles of the forearm actions around AP axis
Extensor carpi radialis longus and brevis abduct hand at wrist
Name the medial extensor muscles of the forearm; their origin; their innervation.
Extensor carpi ulnaris (base of 5th metacarpal)
Extensor digitorum (digits 2-5)
Extensor digiti minimi (digit 5)
Originate from lateral epicondyle of humerus
Innervated by Radial N.
Medial extensor forearm muscles of the forearm actions and where do they cross in relation to the transverse axis
All 3 muscles cross elbow posterior to transverse axis (extensor carpi ulnaris, extensor digiti minimi, extensor digtiorum)
- Weak elbow extension
All 4 cross wrist posterior to transverse axis:
- Strong wrist extension
Extensor digitorum crosses MP, PIP, and DIP:
- Extends MP
- Extends PIP and DIP (weak, assists intrinsic hand muscles)
Medial extensor forearm muscles of the forearm actions around AP axis
Extensor carpi ulnaris adducts hand at wrist
Extensor expansion/hood
Expansion of extensor digitorum tendons that connect to ligaments of MP, PIP, and DIP joints.
Affects ability of joints of fingers to move independently (hard to move one joint at a time) bc anything that increases tension on extensor expansion causes extension of PIP and DIP.
What muscles insert into the extensor expansion/hood?
2 sets of intrinsic hand muscles:
- Lumbricals
- Interossei
Name the deep extensor muscles of the forearm; their innervation.
Supinator Abductor pollicis longus Extensor pollicis brevis Extensor pollicis longus Extensor indicis
All innervated by Radial N.
If a muscle has a medially-directed pull, posterior to the vertical axis through the glenohumeral joint, how would it move that joint?
Laterally rotates humerus
Name a rotator cuff muscle which protects against anterior dislocation of the glenohumeral joint.
Subscapularis
A woman comes to clinic with a calcification in a tendon due to chronic degenerative changes. The tendon runs between the head of the humerus and the acromion. In which tendon is the calcification?
Supraspinatus
