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Brachial Fascia
- deep fascia that surrounds the Arm (analogous to the fascia lata of the thigh)
- sends septa INWARD toward the humerus that divides the Arm into an anterior & posterior compartment
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Muscles in the Anterior Compartment of the Arm
- flex the arm at the shoulder joint or flex the forearm at the elbow joint
- all these muscles are supplied by the Musculocutaneous nerve
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Muscles in the Posterior Compartment of the Arm
- really just 1 muscle - the Triceps
- extend the arm at the shoulder joint or extend the forearm at the elbow joint
- supplied by the Radial nerve
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What connects the radius to the ulna?
- the interosseuous membrane (a fibrous sheet) of the forearm
- (just like the one between the tibia & fibula in the leg)
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Antebrachial Fascia
- deep fascia of forearm that's continuous w/ the brachial fascia
- a dense, membranous investment, which forms a general sheath for the muscles in the forearm region
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Muscles in the Anterior Compartment of the Forearm
- flex the hand at the wrist joint or continue into the hand to flex the digits
- also pronate the forearm (turn the back of the hand up)
- are supplied mainly by the Median nerve but also have some assistance from the Ulnar nerve
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Muscles in the Posterior Compartment of the Forearm
- extend the hand at the wrist joint or continue into the hand to extend the digits
- also supinate the forearm (turn the palm of the hand up)
- like the muscles in the posterior compartment of the Arm, these muscles are supplied by the Radial nerve
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Hand Muscles
- flex, abduct, & adduct digits
- are innervated by the Ulnar & Median nerve (which travel down from the anterior compartment of the Forearm)
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Where do the rotator cuff muscles attach?
to the greater or lesser tubercles
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What muscle attaches at the deltoid tuberosity?
exists about halfway down the humerus, is the point of insertion for the DELTOID muscle
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Spiral Groove
groove on the posterior part of the humerus that serves as a pathway for the Radial nerve to traverse as it makes it way down the arm & innervates the muscles in the posterior compartment of the forearm
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Distal End of the Humerus
- is made up of 2 parts
- 1. Capitulum: rounded head on the lateral side of the humerus
- 2. Trochlea: on the medial side ('like a pulley')
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Forearm Bones
- Radius (more lateral) & Ulna (more medial & is longer)
- Radius has a rounded head at its proximal end in the elbow joint, a shaft that flares out at its distal end, & a distal head that articulates w/ bones in the wrist
- Ulna has an indentation at its proximal head called the Trochleal notch, the posterior Olecranon, the Ulnar tuberosity right below the proximal head, a shaft that narrows as it progresses toward the wrist joint, where it ends in the HEAD of the ulna (distal part = head)
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Which forearm bone pivots around the other forearm bone that is fixed?
- the Radius can PIVOT around the fixed Ulna
- when the hand is supinated, the bones lie 'parallel' to each other
- when the hand is pronated, the Radius is crossed over the Ulna
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Radial Tuberosity
located just distal to the head of the radius (just below the elbow joint) where the tendon of the biceps brachii attaches
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Trochleal Notch
- found at the proximal end of the ulna
- acts sort of like the mouth of a pipe wrench that grabs onto the trochleal part of the humerus
- allows flexion & extension of the forearm at the elbow joint
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Elbow Joint
- articulation between the head of the radius & the capitulum of the humerus; this is where the radius can pivot
- trochlear notch of the ulna fits into the trochlea of the humerus
- at this joint have flexion, extension, pronation, & supination
- can see posterior displacement of the ulna in the dislocation picture
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Olecranon
- posterior part of the proximal end of the Ulna which on the surface feels like the hard part of the elbow
- is where the Triceps Branchii muscle inserts
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Ulnar Tuberosity
- located below the proximal end of the Ulna on the 'anterior' side of the bone
- where the arm's Brachialis muscle tendon inserts
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Where does the blood supply to the upper limb come from?
- the Brachial Artery
- Radial & Ulnar Arteries
- the Cephalic, Basilic, & Median Cubital Veins
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Brachial Artery
- distal continuation of the Axillary artery
- name changes from Axillary → Brachial when the artery passes the lower edge of the Teres Major muscle
- runs on the medial side of the humerus
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Deep Brachial Artery
- branches off the Brachial Artery as soon as it turns into the Brachial from the Axillary (at that border defined by the Teres Major)
- winds around the back of the humerus (in company w/ the Radial nerve), comes down around the lateral side of the elbow joint, & connects with a branch of the Radial artery
- provides an anastamoses around the elbow joint
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Ulnar Collateral Arteries
- branch off the Brachial artery, go anterior & posterior to the medial side of the elbow joint, then anastamose w/ the Ulnar artery
- also provide collateral circulation around the elbow joint
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What happens when the Brachial Artery cross the elbow joint?
- it will branch into 2 arteries that run through the forearm: the Ulnar (medial) & Radial (lateral) Artery
- so Subclavian → Axillary → Brachial → Ulnar & Radial
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What happens to the Ulnar & Radial Arteries?
- they 'meet up' in the hand & form 2 arches
- Superficial Palmar Arch
- Deep Palmar Arch
- these provide collateral circulation around the hand
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Cephalic & Basilic Veins
superficial veins that lie just deep to the skin
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Median Cubital Veins
- lies in the anterior part of the elbow joint
- connects the Cephalic & Basilic veins
- is often used for vena puncture to get a sample of blood or to inject blood into the circulation
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Brachial, Ulnar, & Radial Veins
- run alongside the aforementioned arteries w/ the same names
- lie deep to the fascia
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Muscles of the Shoulder & Arm
- Thoraco-appendicular Group: from the thorax → the scapula or humerus
- Scapulo-humeral Group: from the scapula → the humerus
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The Scapulo-humeral Group of muscles include which muscles around the shoulder?
the Rotator Cuff muscles
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Thoraco-appendicular Muscles (5)
- Trapezius
- Latissimus Dorsi
- Rhomboids
- Serratus Anterior
- Levator Scapulae
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Trapezius
• the Upper part attaches to the back of the base of the skull (occipital region) or the spinous processes of the cervical vertebrae (in the midline) & can ELEVATE the scapula
• the Middle part originates on the upper spinous processes of the thoracic vertebrae (fibers run practically horizontally) & can RETRACT the scapula
• the Lower part originates on the lower spinous processes of the thoracic vertebrae & can DEPRESS the scapula
• all parts insert on the spine of the scapula & serve to ROTATE the scapula
- • supplied by the Spinal Accessory nerve, CN XI (one of the cranial nerves, NOT one from the brachial plexus)
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Latissimus Dorsi
• when the muscle contracts, it pulls toward the midline & posteriorly → extends, adducts, & medially rotates the humerus
• the lower part originates from the Thoraco-lumbar fascia (very thick fascia)
• its muscle fibers run up laterally to attach to the floor of the intertuburcular groove on the humerus
• is supplied by the Thoracodorsal (or Middle Subscapular) nerve which comes off the posterior cord of the brachial plexus
• is the widest muscle of the back
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What examples does Wilson give of things the Latissimus Dorsi is used for?
- Lat pulls (gym)
- Rowing (canoeing)
- Climbing a rope
- Skiing
- Chopping Wood
- (lots of other muscles are used for these processes too…)
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Retraction of the Scapula (Adduction)
- the scapula is moved posteriorly & medially along the chest wall
- rhomboideus major, minor, & trapezius are the prime movers
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Rhomboids
- pulls the scapula in toward the midline to RETRACT it & can also rotates it inferiorly
- seen under/if you cut the Trapezius
- made up of 2 parts, the rhomboid major & minor
- both originate off the medial border of the scapula
- the minor part inserts on lower cervical/upper thoracic spinous processes
- the major (larger) part inserts on lower thoracic spinous processes
- supplied by the Dorsal scapular nerve (comes off of the C5 root of the brachial plexus)
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Levator Scapulae
- small muscle that elevates the scapula
- runs from the posterior tubercles of transverse processes of C1 - C4 vertebrae to the superior part of the medial border of the scapula
- supplied by cervical nerves C3, 4, & the Dorsal scapular nerve (comes off of the C5 root of the brachial plexus)
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Serratus Anterior
- protracts (hunch) & rotates the scapula superiorly
- supplied by the Long thoracic (C5, 6, 7) nerve [branches off the roots of C5, 6, 7 cervical nerves]
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Protraction of the Scapula (Abduction)
- the scapula is moved laterally & anteriorly along the chest wall
- Serratus anterior is the prime mover
- Pectoralis minor & major, the latter acting through the humerus, may assist (act as synergists)
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Scapulo-humeral Muscles (7)
- Supraspinatus
- Infraspinatus
- Teres minor
- Subscapularis: Upper & Lower
- deltoid
- teres major
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Deltoid Muscle
- middle part ABDUCTS the arm (main purpose)
- anterior part helps to FLEX the arm
- posterior part helps to EXTEND the arm
- originates off the lateral part of the spine of the scapula, the lateral part of the clavicle, & the acromion
- muscle fibers come together to form a tendon that inserts on the deltoid tuberosity (~halfway down the lateral part of the humerus)
- is innervated by Axillary nerve (comes off the posterior cord)
- looks like an upside down 'delta'
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The Deltoid muscle can abduct upper limb to ~90 – 120o, but what does abduction of it to 180o require?
- abduction of the upper limb to 180o requires ROTATION OF THE SCAPULA
- serratus anterior fibers pull on the lower part of the scapula
- lateral fibers of the trapezius pull on the acromion (lateral part of the scapula spine)
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Scapulo-humeral Rhythm
- when abducting the arm to 180o, motion occurs at the glenohumeral, scapulo-thoracic, sternoclavicular, & acromioclavicular joints
- for every ~2o of abduction by the deltoid, there's ~1o of rotation of the scapula
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What will paralysis of the serratus anterior muscle result in?
both a “winged scapula” & the inability to abduct to 180o (serratus anterior can't pull down on the lower part of the scapula, meaning it's unable to rotate)
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Teres Major Muscle
- adducts & medially rotates the humerus
- originates off the lower lateral edge of the scapula (posterior surface of inferior angle of the scapula)
- runs anterior to the long head of the triceps
- inserts on the intertubercular groove of the humerus
- is supplied by the lower subscapular nerve
- (not a true rotator cuff muscle b/c it doesn't insert on the head of the humerus)
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