anatomy exam 2

classifications of joints

functional-

• synarthrosis- very limited motion

• amphiarthrosis- limited motion

• diarthrosis- freely movable

anatomical

• fibrous- synarthrodial (dense irregular fibrous connective tissue) ex: sutures, gomphosis, syndesmosis (radius and ulna)

• cartilaginous- synarthrodial or amphiarthrodial

  • synchrondrosis- 2 bones that are initially separate join by hyaline cartilage (primary = hyaline cartilage growth plate)

  • symphysis- fibrocartilage between bones (pubic symphisis, intervertebral discs)

• bony- synarthrodial (bones connected by bony union)

• synovial- diarthrodial

synovial joints types

plane: gliding

pivot: rotation

hinge: flex and extend

saddle: movement in 2 directions

condyloid: flex, extend, adduct, abduct, circumduction

ball and socket: flex, extend, adduction, abduction, rotation, circumduction

synovial joint development/characteristics

loading of joints puts mechanical strain on tissues during development

paralysis in vitro prevents cavitation

characteristics:

• bones linked by fibrous capsule so bony surfaces are not in contact

• bony surfaces covered by articular cartilage (helps with gliding)

• lined by synovial membrane, joint cavity filled with synovial fluid

• muscles and tendons are important for integrity/stability of many joints

accessory ligaments- connect bone to bone

• capsular- thickening of joint capsule

• extra capsular- outside joint capsule

• intracapsular- inside joint capsule

synovial membrane

ends at articular cartilage and does not cover it

very vascular so pathogens can go to it

2 layers

• intima- producing synovial fluid and cleaning fluid

• subintima- nerves and richly vascularized

  • important for diffusion, regulation of joint temp via blood flow

synovial fluid function- joint movement, lubrication, facilitates exchange of oxygen (healthy fluid appears clear to light yellow)

• lubricant- boundary layer lubrication of joints

• hyaluronan- incerases viscosity and works w/ lubricin to lubricate

muscle action vs function

action- motions produced by its shortening

function- reason the brain chooses to stimulate a muscle

joints of the shoulder

acromioclavicular

sternoclavicular- only synovial joint that holds the upper limb onto the body

glenohumeral- flexion, extension, rotation, adduction, abduction

• head of humerus and glenoid fossa

• held together by coracoclavicular, coracoacromial ligaments, joint capsule, glenohumeral ligaments anteriorly and rotator cuff muscles posteriorly

• tendon of long head of biceps brachii (goes into joint capsule)

scapulothoracic- not a synovial joint but blade of scapula slides around thorax (elevation, protraction/retraction, and upper/downward rotation)

positions that compromise shoulder stability:

• abducted, extended, externally rotated (like throwing a ball)- causes inferior destabilization → anterior shoulder dislocation

elbow joint

humeroulnar- trochlea of humerus and trochlear notch of ulna

humeroradial- capitulum of humerus and radial head

proximal radioulnar

pronation and supination- ulna doesn’t move, radius just rolls over it

ligaments holding elbow together

• lateral: radial collateral ligament

• medial: ulnar collateral ligament

• anular ligament (creates a funnel for radial head to sit in) - prevents radial head subluxation

hand and wrist

carpals

metacarpals

phalanges: 5 proximal, 4 intermediate, 5 distal

joints-

• radoiocarpal (wrist)- articular disc prevents triquetrum from participating (so only scaphoid, lunate, radius)

  • ligaments- carpal tunnel formed by flexor retinaculum

• metacarpophalangeal- superficial wrist/hand muscles, deep hand muscles (thenar and hypothenar muscles, interosseous muscles, lumbricals)

  • extensor digitorum tendon → extensor expansion (extensor digitorum, central band, 2 lateral bands, terminal tendon)

  • flexor digitorum profundus and flexor digitorum superficialis (both on flexor side of finger)

• proximal interphalangeal

• distal interphalangeal

hand and wrist injuries

terminal extensor tendon rupture- mallet finger (permanent flexion of distal interphalangeal joint)

central band rupture- boutonniere deformity (permanent flexion of proximal interphalangeal joint and permant extension of distal interphalangeal and metacarpalphalangeal joints)

• bc lateral bands slip down side of finger, which allows extensor digitorum to flex at pip

limb embryology

outgrowths of ventrolateral body wall

apcial ectodermal ridge induces development of mesenchyme → growth in proximo-distal axis

limb rotation-

• week 4-5- palmar and plantar sides face ventrally

• by end of 7th week, limbs have rotated in opposite directions

anterior arm

all innervated by musculocutaneous nerve

major actions: flex shoulder and elbow, supinate forearm

biceps, brachialis, coracobrachialis

posterior arm

triceps

innervated by radial nerve

major actions: extension of shoulder and elbow

posterior forearm

innervated by radial nerve, superficial radial nerve, or deep radial nerve

major actions: extend wrist and fingers

anatomical snuffbox formed by abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus

anterior forearm

innervation- median nerve or ulnar nerve

major actions- flex wrist and fingers

muscles of the hand

innervation- ulnar nerve or median nerve

major actions- abduction/adduction of fingers, flex MCP, extend PIP, opposition of first digit

arteries of the arm

subclavian → axillary (at 1st rib) → brachial (inferior teres major) → splits into radial and ulnar

smaller arteries anastomose around the elbow for collateral blood flow

brachial plexus

series of ventral roots that split and merge to form all the nerves of the uppper limb

roots of brachial plexus are ventral rami

roots, trunks, divisions, cords, branches

clinical correlation- inflammation in carpal tunnel = compression of median nerve

injuries to brachial plexus (proximal)

erb duchenne palsy- C5 and C6 root separated from superior trunk (caused by separation of neck and shoulder)

• dorsal scapular nerve not affected because it’s not distal to the injury

• loss of supination from biceps (musculocutaneous nerve) → hand presents always pronated

• loss of flexion at forearm → arm always extended

• loss of abduction (deltoid and supraspinatus), rotation of shoulder (rotator cuff)

• sensory deficits on lateral shoulder, arm, forearm, hand

klumpke’s palsy- C8-T1 and inferior trunk have too much pressure when arm is severely abducted

• complete loss of ulnar nerve (all intrinsic hand muscles → fingers 2-5 can’t be extended, dip can’t be flexed at fingers 4-5)

• partial loss of medial nerve

• loss of sensation on medial forearm and medial hand

injuries to brachial plexus (distal)

long thoracic neve damage- winged scapula (C5-C7 nerve damage)

axillary nerve damage (C5-C6)- loss of abduction from deltoid and lateral rotation from teres minor but compensated by infraspinatus, loss of cutaneous sensation to upper lateral arm

radial nerve (saturday night palsy)- wrist drop, loss of elbow extension (triceps), wrist extension (hand extensors), posterior, forearm, dorsolateral hand, dorsum of proximal part of lateral 3.5 fingers sensation

• if it’s damaged more distally (along humeral shaft, triceps would not be paralyzed)

median nerve damage at elbow- loss of thumb opposition, loss of flexion of lateral 3 fingers (hand of benediction when making fist), loss of cutaneous sensation of lateral 3.5 digits and lateral 2/3 of palm, loss of pronation

median nerve damage at wrist- loss of motor innervation to all 2 thenar eminence muscles, lateral 2 lumbricals, loss of sensory innervation same as damage to elbow

ulnar nerve damage at elbow (cubital tunnel syndrome)- loss of abduction and adduction of fingers 2-5, partial claw hand at rest (flexed pip joints but extended dip joints at fingers 4-5), loss of sensation to medial 1/3 of hands and medial 1.5 fingers

ulnar nerve damage at wrist (guyon’s canal)- motor loss in hand same as elbow injury but wrist flexion not affected, greater flexion of fingers 4-5, loss of sensation of distal 1/3 of palm and finger 4-5