elbow, arm, forearm, wrist hand Flashcards
forearm bones
radius on the lateral or thumb side
ulna on the medial or little finger side
both bones articular with the humerus, so the elbow joint is really 2 synovial joints enclosed in the same capsule
joint between the humerus (trochlea) and the ulna (trochlear notch on the olecranon process)
a hinge joint allowing only flexion-extension
joint between the head of the radius and the capitulum of the humerus
allows flexion-extension and the head of the radius to rotate; this rotation in turn allows for supination and pronation of the forearm and hand; the superior (proximal) radioulnar joint also lies in the joint capsule
at the superior (proximal) radiulnar joint
the head of the radius lies within a ring composed of the anular ligament and the radial notch of the ulna; this is a pivot joint; the head of the radius slides again the ulna allowing the head to rotate during supination and pronation
in the supine position (anatomical position), the radius and ulna
lie parallel to each other; in the prone position, the radius rotates nearly 180degrees and comes to lie over the ulna; the hand is attached to and rotates with the radius
pronation is performed by
the teres and pronator quadrants muscles of the forearm
supination is performed by
the supinator muscle of the forearm, but biceps is the most powerful supinator when the elbow is fixed
collateral ligaments of the elbow joint
prevent abduction-adductionof the forearm at the elbow
ulnar collateral ligament
attaches medial epicondyle of humerus to ulna, but radial collateral ligament attaches to the ulnar ligament, not to the radius itself (to allow rotation of the radius)
hooked olecranon process
allows increased area for attachment of the triceps muslce
on extensionof the elbow, the olecranon process goes into the olecranon fossa on the posterior side of the humerus; this prevents hyperextensionfthejoint
A FOOSH with the elbow flexed (more common in children)
can break the humerus above the condyles of the elbow joint
in this supracondylarfracture, the brachial artery and median nerve areat risk, because they are immediately anterior to the joint
how do protonation and supination of the radius become compromised
if the headbecomes unableto rotate freely within the anular ligament
pulling forcibly on the hand, particularly of small children
can pull the head of the radius out of the anular ligament (dislocation); this is called pulled elbow or “nursemaids elbow”
anterior compartmentof the upper limb
contain flexor muscles innervated by nerves from anterior divisons of the brachial plexus
posterior compartments of the upper limb
contain extensor muscles innervated by nerves from posterior divisions of the plexus
what separates the anterior and posterior componentsofthe arm
the septa and the humerus
musculocutaneous nerve
supplies the muscles of the anterior compartment of the arm (flexors of the elbow and shoulder joints)
biceps brachii
has 2 heads; a long head runs in the bicipital groove across the shoulder joint to the supraglenoid tubercle, while a short head attaches to the coracoid process (already seen with the shoulder joint); biceps inserts on the tuberosity of the radius via the biceps tendon and to forearm fascia via the bicipital aponeurosis
biceps brachii actions
bicepsis a flexor of the elbow joint; the tendon of the long head stabilizes the shoulder joint during flexion.
biceps is also the important supinator of the forearm when the elbow is flexed
coracobrachialis muscle
runs from the coracoid process of the scapular to the humerus; together with the pectoralis major, it draws the arm medially across the chest; an adductor when the arm is abeducted
brachialis muscle
lies deep to the biceps, originates on distal portion of humerus and inserts on tuberosity and coronoid process of ulna; it flexes the elbow joint, but does not supinate the hand because it doesn’t act on the radius
musculocutaneous nerve
from lateral cord of brachial plexus; it pierces coracobrachialis and supplies it, then runs between the biceps and brachialisis and supplies them. its terminal branch is the lateral cutaneous nerve of the forearm, which emerges lateral to the distal part of the biceps
cutaneous innervation of the arm
although the axillary nerve comes from the posterior cord, its cutaneous branches supply anterior skin just distal to the shoulder join; the axillary nerve may be damaged by a shoulder dislocation, causing a deficit in the cutaneous sensation; a branch of the radial nerve also winds around the lateral side of the arm to supply a lateral portion of anterior skin
lateral cutaneous branch of T2
supplies skin coveringthe rib cage and adjacent portionsof the arm; it is therefore called the intercostalbrachial nerve; pain from angina or a heart attach is referred in part to the T2 dermatome on the left side, accounting for the characteristic distribution of this pain; medical and posterior cutaneous nerves of the arm supply their named areas
radius and ulna together with teh interosseous membrane that conencts them
divide the forearm into anterior and posterior compartments
carpal bones
are in two rows; from lateral to mesial the bones are:
proximal row - scaphoid, lunate, triquetrum, pisiform
distal row - trapezium, trapezoid, captiate, hamate
scaphoid
shaped like the hull of a ship; also called the navicular
trapezium
articulates with the 1st metacarpal at the base of the thumb
pisiform
shape of a pea; really a seasmoid bone in the tendon of a flexor muscle of the wrist (Flexor carpi ulnaris)
hook of hamate
a projection that is an attachment for this muscle
each of the digits
has a proximal, middle and distal phalanx, connected by proximal and distal interphalangeal joints
thumb
has a proximal phalanx and distal phalanx, connected by one interphalangeal joint
radiocarpal joint (wrist)
radius articulates with the scaphoid and lunate bones; the triquetrum articulates with a triangular piece of fibrocartilage at the distal end of the ulna; the fibrocartilage rotates relative to the ulna during pronation/supination; there is a midcarpal joint between the proximal and distal rows of carpal bones; there is a radiocarpal and midcarpal joint between the proximal and distal rows of carpal bones; the radiocarpal and midcarpa joints allow flexion, extension, abduction and adduction
radial and ulnar deviation (abduction and adduction)
primarily occur at the midcarpal joint
joints that connect the wrist and hand
wrist joint metacarpophalangeal joints (MP) proximal (PIP) distal (DIP) interphalangeal joints
layer 1 of anterior compartment of the forearm
4 muscles: lateral to medial: pronator teres, flexor capri radialis, palmaris longus, flexor carpi ulnaris
pronator teres
inserts on the radius and draws the radius medially over the ulna to cause pronation; it has two heads, attached to the medial epicondyle of the humerus and the cornoid process of the ulna
flexor capri radialis
attaches distally to the base of the 2nd and 3rd metacarpals
flexor capri ulnaris
attaches to the pisiform and the hook of the hamate with an extension to the 5th metacarpal
which muscles flex the wrist joint
flexor capri radialis and flexor capri ulnaris
palmaris longus
attaches to palmar aponeurosis of the head; it may be missing
layer 2
flexor digitorus superficialis; note the wide origin from the common flexor origin + ulna + radius; it attaches to the middle phalanx of digits 2-5 and flexes the proximal interphalangeal joints
layer 3
2 flexors
flexor digitorum profundus (medial) from ulnaand interosseous membrane, insert into distal phalanx and flexes the distal interphalangeal joints of digits 2-5. ulnar half of this muscle (to digits 4-5) is suppliedby the ulanr nerve; ulnar supplies 1/2 musclesin the forearm and 1/2 digits in the hand
radial half of the flexor digitorum profundus (to digist 2-3) is supplied by the deep branch of the median nerve, the anterior interosseus nerve, lying just deep to it; note how the tendon of flexor digitorum superficialis splits to allow the tendon of flexor digitorum profundus to pass through
flexor pollicis longus (lateral)
from radium and interosseuous membrane; is attached to the distal phalanx of the thum, flexes the interphalangeal joint and is supplied by the anterior interosseus nerve; only 2 phalanges of thumb, so only 1 IP joint
layer 4
portnator quadratus, the square pronator, attached to adius and ulna at their distal ends, deep to flexor digitorum profundus; also supplied by anterior interosseus merve
blood supply of the arm
the superficial veins of the arm, the cephalic and basilic ceins, are connected by the median cubital vein in the cubital fossa which lies anterior to the elbow joint; this is a convenient place to draw blood as underlying structures are protected by the tough bicipital aponeurosis
brachial artery
deeper in the cubital fossa; the brachial artery divides into the artiers of the forewarm, the raidal and ulnar arteries; additionally, recurrent artiers arise from the radial and ulnar arteries and anastomose with collateral arteries of the arm, forming a collateral circulation around the elbow joint.
common interosseous artery
just distal to the cubital fossa; arises from the ulnar artery; the common interosseus artery gives two branches, the anterior and posterior interosseous arteries; these run just anterior and posterior to the interosseous membrane and supply the deeper muscles of the forearm
radial artery
runs distally with the superficial branch of the radial nerve undercover of the brachioradialis muscle; after giving off the common interosseous artery, teh ulnar artery runs distally with the ulnar nerve under cover of fleor carpi unaris; the two aretiers are connected in the hand by the lamar arches, which in turn give branches to the digits
nerve supply
anterior muscles of the forearm are innervated by the median and ulnar nerves; the ulnar nerve innervats the skin of 1 1/2 digits int he hand and innervates 1 1/2 muscles in the forewarm; muscles supplied by the ulnar nerve are on the ulnar side of the forearm, the flexor capri ulnaris and the ulnar half of the flexor digitorum profundus flexing the ring and little fingers; remaining anterior compartment muscles are innervated by the median nerve or its branch, the anteriro interosseous nerve
median nerve
passes between the two heads of the pronator teres and then runs deep tot eh flexor digiotrum superficialis, supplying these muscles as well as the overylying flexor carpi radialis and palmaris longus; the anterior interosseous nerve (a deep branch of the median nerve) run with the anterior interossesu artery to supply the deep muscle of the anterior compartment, flexor pollicis longus, the radial 1/2 flexor digtorum profundus (flexor of the index and middle finters) and pronator quadratus; the median nerve then passes into the hand to supply additional muscles an skin
cutaneous nerves of the forearm
the lateral cutaneous nerve of the forearm is part of the musculocutaneous nerve (lateral cord of the brachial plexus); the medial cutaenous nerves of the arm and forearm are branches of the medial cord of the brachial plexus
cutaneous innervation of the hand
medial 1 1/2 digits (little finer and 1/2 of ring finger), both dorsal and palmar, is by branches of the ulnar nerve
palmar surface of the lateral 3 1/2 digits is by branches of the median nerve
remaining dorsal surface and palmar base of thumb is by the superficial branch of the radial nerve
muscles of the posterior compartment of the arm
are extensors of the shoulder, elbow, wrist and hand joints; the msucles are innervated by the radial nerve and its extension, the posterior interosseous nerve, which are both derived from the posterior cord of the brachial plexu
muscles of the posterior compartment of the arm
triceps, a 3 headed muscle; its long head originates at infraglenoid tubercle of scapula; it is an extensor of the shoulder; lateral and medial heads arise lat and me to the raial groove of the humerus; these don’t act on the shoulder joint; the radial nerve and the profunda brachii artery lie in the radial groove; both have branches supplying posterior compartment muscles of the arm; triceps inserts ont eh olecranon process of the ulna and is an extensor of the elbow joint
anconeus
a small muscle extending from the lateral epicondyle of the humerus to the olecranon process of the ulna; this is an offshoot of the triceps, and also an extensor of the elbow joint
skin over the posterior compartment of the arm are supplied by
cutaneous branches of the radial and axillary nerves
muscles of the posterior compartment of the forearm are innervated by
the posterior interosseous nerve, which is the continuation of the deep branch of the radial nerve
radiak nerve
runs in the radial groove on the humerus and emerges deep in the cubital fossa - a triangular region anterior and distal to the elbow joint; the cubtal fossa is bounded by pronator teres medially and brachioradialis lateally, and superioly by a line across the epicondyles of the humerus; it is important because of the locations of nerves and blood vessels; the median nerve and brachial artery pass through the fossa
deeper in the cubital fossa
the radial nerve also divides into its sueprficial and deep branches; the deep branch runs through the supinator muscle in the floor of the cubital fossa to become the posterior interosseous nerve; the superficial branch is only cutaneous and continue toward the hand under cover of the brachioradialis muscle; it supplies skin on the back of the hand
