BM unit 4

Question 1

what does the upper limb consist of? (5 parts)

Answer 1

shoulder girdle, arm, forearm, wrist, hand

Question 2

what forms the shoulder girdle?

Answer 2

clavicle and scapula

Question 3

what forms the arm?

Answer 3

humerus

Question 4

what forms the forearm?

Answer 4

ulna and radius

Question 5

what forms the wrist?

Answer 5

8 carpal bones

Question 6

what forms the hand?

Answer 6

metacarpals and phalanges

Question 7

name the 3 joints that give the upper limb a wide range of motion

Answer 7

shoulder, elbow, wrist

Question 8

what forms the spine?

Answer 8

24 vertebrae, sacrum, coccyx

Question 9

name the 4 articulations of the shoulder joint and their types

Answer 9

glenohumeral, acromioclavicular, sternoclavicular (all synovial) and scapulothoracic (bone-on-muscle-on-bone)

Question 10

describe the glenohumeral joint

Answer 10

ball-and-socket, synovial joint formed by the humeral head and the glenoid fossa of the scapula. shallow socket for a wide ROM but leaves it susceptible to dislocation. the glenoid labrum assists with stability - it is a thick and cartilaginous rim. the articulation is surrounded by a capsule and more importantly the rotator cuff

Question 11

describe the rotator cuff

Answer 11

group of 4 muscles and their tendons - subscapularis, infraspinatus, supraspinatus and teres minor. they form a cuff of tissue around the glenohumeral joint. they provide dynamic restraints to anterior, posterior, and inferior displacement. the rotator cuff pushes on the humeral head, preventing any anterior-posterior movement, stabilising the joint.

Question 12

describe acromioclavicular joint

Answer 12

small synovial joint formed by the prox acromion of the scapular and the distal clavicle.
it is stabilised by superior and inferior acromioclavicular ligaments which prevent the joint being pulled apart. further stability is provided by the two parts of the coracoclavicular ligament between the clavicle and the coracoid process of the scapula which limit the movement of the clavicle.

The ROM is restricted by the thorax and the muscle attachments, being limited to a few degrees during arm abduction.

Question 13

sternoclavicular joint

Answer 13

small synovial joint between the manubrium of the sternum and the prox clavicle. it is the only bony joint connecting the shoulder girdle to the trunk.

during arm elevation the clavicle also elevated at the SC joint. for the first 90 degrees of arm elevation the clavicle elevates by about 4 degrees for every 10 degrees of arm elevation. Beyond 90 degrees of arm elevation the elevation of the clavicle is almost negligible.

During elevation and depression the clavicle rotates about an axis determined by the attachment of the costoclavicular ligament (clavicle to rib)

Question 14

scapulothoracic articulation

Answer 14

the bone-muscle-bone articulation between the scapula and the posterior thoracic wall. Not a joint in its truest sense since there are no direct bony or ligamentous connections between the scapula and the thorax. but it contributes to the wide ROM of the scapula.

The broad ant surface of the scapula is separated from the post thorax by two broad flat muscles - the serratus anterior and the subscapularis muscles.

the serratus ant originates on the upper 8/9 ribs and inserts on the ant surface of the scapula along its vertebral border. it helps hold the scapula against the thorax and prevents winging, and is a strong abductor that is useful in pulling/pushing movements.

the subscapularis originates from the subscapular fossa and inserts on the lesser tubercle of the humerus. It is one of the rotator cuff muscles and acts to medially rotate the humerus.

Question 15

ROM of shoulder

Answer 15

shoulder elevation - humerus away from the side of the thorax in any plane. quantified by the angle of elevation.

shoulder depression - humerus towards the thorax

in the sagittal plane:
shoulder elevation = forward flexion when the arm moves forward and backwards extension/backwards elevation when it moves back
flexion - 180
extension - 60

in the coronal plane:
shoulder elevation = abduction when the arm moves away, and adduction when the arm moves towards the trunk (true adduction is restricted by the trunk nut if you put the arm slightly in front of the trunk it can be achieved)
abduction - 180
adduction - 75

all these ranges decrease with age

rotation about the longitudinal axis of the humerus
internal rotation - 90
external rotation - 90
(total of 180)
amount varies with the amount of shoulder elevation

motion in transverse plane. starting from a position of 90 degrees abduction with the arm parallel to the ground
horizontal flexion - 135
horizontal extension - 45

Question 16

most common shoulder dislocation

Answer 16

anterior dislocation of the glenohumeral articulation. head of humerus slips forwards off the shallow glenoid fossa. occurs when arm suffers a heavy blow when the shoulder is abducted and extended horizontally. in this position the arm pivots about the acromion and the ligaments and muscles act to prevent the humeral head slipping. if the blow is too heavy/ligamental muscles are too weak then dislocation occurs. in this way the arm and shoulder are functioning as a first class lever.

with the arm fully extended the effort force is working a v large mechanical advantage over resistance force enabling even a comparatively small external force to cause a dislocation.

Question 17

describe the elbow joint

Answer 17

formed by the distal surface of the humerus and the prox articular surfaces of the forearm bones, the radius and ulna.
3 synovial articulations - humeroradial, humeroulnar, prox radioulnar
humeroradial - capitellum of the distal humerus and the head of radius
humeroulnar - trochlea of the distal humerus and the reciprocally shaped trochlear fossa of the prox ulnar
radioulnar - head of radius and radial notch of ulna.

Question 18

ROM of elbow

Answer 18

2 articulations that include the humerus allow the elbow to flex and extend in a hinge like manner. teh axis of rotation passes through the middle of the trochlear and is roughly parallel to the line joining the lateral and medial epicondyles of the humerus
flexion-extension motion - 140
when the elbow is fully flexed the angle between the humerus and forearm is 40 degrees and when fully extended it is 180 - so total ROM of 140 (140 flexion and 0 extension)

radioulnar artic allows rotation of forearm about a longitudinal axis - pronation and supination
pronation - palm faces posteriorly if elbow is extended with the upper arm alongside the trunk, and downwards of the elbow is flexed at 90 degrees.
achieved by rotation of the head of the radius in the radial notch of the ulnar in a pivot like manner. it occurs inside the ligamentous sling which binds the radius to the ulnar - the annular ligament. the longitudinal axis passes through the radial head and the distal ulnar articular surface. rotation about this axis results in the migration of the distal end of the radius around the distal end of the ulnar
pronation - 70
supination - 80
total - 150

Question 19

ROM OF ELBOW IN DAILY LIFE

Answer 19

100 flexion motion from 30-130 degrees

100 pronation supination - around 50 pronation and 50 supination

Question 20

stability of teh elbow

Answer 20

mechanically stable joint with the bony structure and ligaments an muscles all contributing

olcranon process - resists forces in the anteroposterior directions as it holds the trochlear like a nut. it doesn’t provide much resistance to forces acting in a lateral and medial direction

side to side stability is provided by 2 collateral ligaments. ulnar or medial colat ligament is most important, it prevents abduction of the elbow.
lateral colat ligament provides only limited resistance to adduction. it is assisted by the anconeus muscle which is located on the lateral aspect of the elbow - origin is on the lateral epicondyle of the humerus and insertion on the olcranon and superior portion of the ulnar shaft. this apparent weakness doesn’t pose a significant problem as valgus stability is much more important than varus.

stability of the elbow means dislocations are much less apparent than the shoulder. but if you fall on outstretched arm in full extension it can result in ant dislocation, where the distal end of humerus slides forward over coronoid process

Question 21

joint forces at the elbow

Answer 21

daily life means joint forces at the elbow can be as high as 3 times body weight eg pulling an object

they are high as the large muscle forces that are needed to be generated to perform these activities act to pull the two sides together. the muscle forces needs to be large since the muscles generally have small moment arms compared to the moment arms of the externally applied forces

Question 22

describe the writs joint structure

what can be palpated

is it a stable joint

Answer 22

allows loads to be transmitted between the forearm and hand

formed by the distal radius, the structures within the ulnocarpal space, the carpal bones and the prox ends of the metacarpals

7/8 of the carpal bones are arranged into 2 rows:
proximal row - triquetrum, lunate, scaphoid
distal row - hamate, capitate, trapezoid, trapezium
the 8th bone, the pisiform, is positioned anterior to the triquetrum

pisiform is the only one that is easily palpated, it projects anteriorly on the side of the little finger. it is the insertion point of the flexor carpi ulnaris muscle which flexes and adducts the wrist. the tendon of this muscle can also be easily palpated when the wrist is flexed . the pisiform increases the lever arm of the flexor carpi ulnaris (like the patella does with the knee extensor muscles)

despite its wide ROM it is a stable joint. its stability is derived from the intricate ligamentous structures and the precise opposition of the multifaceted articular surfaces rather than any inherent bony stability

Question 23

articulations in the wrist

describe in detail the two mist interesting ones

Answer 23

radiocarpal joint, midcarpal joints, carpo-metacarpal joints and the intercarpal joints

the lunate and the scaphoid articulate with the distal end of radius forming the radiocarpal joint. it is a condyloid joint (oval shaped condyle fits into an elliptical depression). it allows flexion and extension, adduction and abduction and circumduction.

the triquetrum articulates with the dial ulnar via a triangular shaped inter-articular disc which occupies the ulnocarpal space. this is attached at its apex to the styloid process of the ulnar and at its base to the ulnar notch of the radius

Question 24

motion at the wrist joint

Answer 24

flexion - 80-90
extension -70-80
60% flexion occurs at the midcarpal joint and the rest at the radiocarpal joint. opposite true for extension

adduction - 35
abduction - 15-20
total - 50

10 degrees of flexion and 35 of extension is satisfactory for daily life. max rage of extension id most crucial. for an immobilised wrist joint a fixed extension of 15 degrees allows most daily activities to be performed

Question 25

hand structure

Answer 25

5 metatarsals and 14 phalanges (three for each finger and two for the thumb)

joints:
carpometacarpal (CMC)
intermetacarpal
metacarpophalangeal (MCP)
prox interphalangeal (PIP)
distal interphalangeal (DIP)

Question 26

describe the CMC joints

Answer 26

The CMC joints are formed by the carpal bones of the wrist and the metacarpals of the hand. first one is formed between the trapezium and the 1st metacarpal, at the base of the thumb. it is of great significance as it is the most freely moving one. it allows the thumb t oppose the fingers giving the hand a much greater dexterity than any animal. it is a saddle joint which allows the 1st metacarpal to flex and extend and abduct and adduct. the remaining CMC joints are modified saddle joints. all the CMC joints are surrounded by joint capsules which are reinforced several times

Question 27

describe the intermetacarpal joints

Answer 27

irregular articulations between the prox ends of the adjacent metacarpals. they share the joint capsule of the CMS joints.

Question 28

describe the metacarpophalangeal joints (MCP)

Answer 28

condyloid joints formed by the rounded distal heads of the mets and the concave prox ends of the phalanges. form the knuckles of the hand. each joint is enclosed in a capsule and is stabilised by strong colateral ligaments. the MCP joint of the thumb is strengthened by an additional dorsal ligament

Question 29

describe the prox interphalangeal (PIP) and distal interphalngeal joints (DIP)

Answer 29

hinge joints allowing flexion and extension motion only. the thumb only has one interphalangeal joint (IP)

Question 30

ROM of the fingers

Answer 30

2nd and 3rd metacarpals are basically immobile, 4th and 5th permit a small amount of flexion and extension in the region of 10-15 degrees in the 4h and 20-30 in the fifth

the metacarpophalangeal joints allow flexion-extension and adduction-abduction. Minimum flexion is 90. amount of extension varies depending on individuals laxity of ligaments.

DIP and PIP permit only flexion and extension. largest flexion occurs at the PIP (100-110). At DIP flexion is about 90. extension beyond the neutral position, with the fingers straight is termed hyperextension - dependent on ligamentous laxity

Question 31

ROM of the thumb

Answer 31

the MCP and IP joints of the thumb resemble those of the fingers in structure and function.

but the MCP joint doesnt allow a large amount of flexion - varies from 30-90. amount of extension through is greater than fingers - 15

CMC joint is of partic importance functionally. Flexion as the thumb moves across the palm and extension as the thumb moves away from the palm - motion of thumb in plane of palm. 15 flexion and 20 extension is possible.

abduction occurs when thumb moves away from hand - 60. a small amount of rotation is also possible.

eg is thumb moves across palm to touch bottom of little finger this is achieved by flexion and and rotation of CMC joint and flexion of MCP and IP joints. if the thumb is then moved to touch the tip of the little finger, abduction is required.

Question 32

interaction of the hand and wrist motion

Answer 32

the principle muscles that control the movements of the digits are actually in the forearm. their distal tendons cross the wrist and possibly several joints of the digits before they are inserted. eg flexor digitorum profundus originates from the ant aspect of the ulnar and has insertions on the distal phalanges, allowing it to flex the distal interphalangeal joints

as the wrist changes position it also alters the functional lengths of the muscle tendons that cross it. eg when the wrist is straight the fingers can be easily clenched into a tight fist, but if flexed then its hard to fully flex the fingers.
similarly range of wrist flexion is dependent on whether the fingers and straight or flexed. with the fingers extended the wrist can flex to 90, but with fingers clenched wrist flexion is reduced.

Question 33

structure and function of the spine

Answer 33

24 vertebrae unfused, the sacrum and the coccyx
protects the spinal cord, transfers loads from the head and trunk to pelvis, and allows movement of the trunk

5 regions - cervical, thoracic, lumbar, sacrum, coccyx

Question 34

describe the vertebrae

Answer 34

all the unfused vertebrae except first two have a flat rounded body placed anteriorly and centrally called teh vertebral body, an arch of bone called the neural arch, that forms the spinal foramen where the SC passes, a spinous process projecting inferiorly in the posterior mid-line and two transverse processes projecting laterally. these processes provide anchorage sites for the ligaments and muscles which stabilise and move teh spine

each vertebra articulates with each adjacent vertebra at three points. the main articulation is at the vertebral body via an intervertebral disc, the two others are facet joints - synovial joints positioned on either side of the arch. the upper facets articulate with the lower facets of the vertebra above and the lower facets articulate with the upper facets of the vertebra below.

Question 35

intervertebral disc structure and function

Answer 35

bears and distributes loads and restrains excessive
motion. the cylindrical discs are made up of the inner nucleus pulpus and outer annulus fibrosus.

Nucleus pulposes lies directly in the centre of the discs except in lumbar region where it is slightly posterior. it is formed by a strongly hydrophilic gel that is enmeshed in a random collagen matrix. it produces a high water content and an elevated nucleus pressure. the internal pressure balances the applied compressive stress. if the applied stress is increased water is driven out of the disc until a new steady state is reached. when the applied stress is reduced the disc rehydrates. but its not capable of maintaining a constant level of hydration over a long period of time. the reduction in hydration over time results in a decreased disc height which is evident in the loss of standing height over the day which can be as much as 1cm.

the annulus fibrosus is a tough layer that surrounds the nucleus pulposus. it is composed of collagen fibres. these form concentric layers (lamellae) with alternating orientations of the collagen fibres. this arrangements resists high bending and torsional loads.

Question 36

the cervical spine

Answer 36

7 vertebrae
most mobile region
C1 atlas and C2 axis are partic mobile
atlas has no body but is composed of a ring within which an oval fossa articulates with the axis
The axis has an articular process, the dens, which protrudes superiorly from the vertebral body. a small synovial joint is formed between the anterior tip of the dens and the oval fossa of the atlas. the atlas rotates about the dens but the motion is restricted by several ligaments that are attached to the top of the dens.

Question 37

the thoracic spine

Answer 37

12 vertebrae
each one is attached to a pair of ribs
each rib articulates with the body and the tubercle of each rib articulates with the transverse process. the 2-9th ribs articulate with the body of the vertebra above also. these articulations allow the ribs to move up and down as we breathe. the ribs give added rigidity to the thoracic spine which effectively limits its mobility to only a very limited degree of flexion and extension and little rotation

Question 38

lumbar spine

Answer 38

5 vertebrae

subject to significantly greater loads. they have larger bodies

Question 39

saccrum and coccyx

Answer 39

distal potion of the spine
sacrum is a single triangular shaped bone that has resulted from the fusion of 5 vertebrae.
coccyx is a single bone that has resulted from the fusion of 4 or 5 vertebrae

sacrum forms the link between the lumbar spine an pelvic girdle. junction between sacrum and lumbar spine is v mobile. sacrum is joined to the two innominate bones of the pelvis by fibrous joints that allow only a small amount of relative motion

Question 40

ROM in spine

Answer 40

overall ROM is large but depends on age

flexion extension varies in the diff parts of spine

• greatest in cervical spine - total ROM of 21 between C4 and C5
• smallest in thoracic spine - total ROM of 3 between T9 and T10
• max amount of flexion and extension also varies within each segment eg in lumbar the max range of flexion is 10 and max range of extension is 4
• during actual movements the motion of the spine is combined with other motion of the MSK system. eg forward bending the first 50-60 degrees of flexion occurs in the lumbar spine with any further flexion being achieved by the pelvis tilting forward.

lateral bending

• cervical spine most mobile
• thoracic least mobile
• no lateral bending between first 2 vertebrae
• no rotation between c1 and occipital bone

rotation

• rotation decreased down the spine
• ROM of considerably largest between c1 and c2 due to their unique structure

Question 41

loadings on the spine and how posture affects it

Answer 41

due to upper body weight, muscle activity and external loads
lumbar carries highest loadings - reflected in large vertebrae. despite this lower back pain in lumbar region is v prevalent and usually results from bad posture or bad lifting techniques. this can be explained by considering the position of the upper body relative to the lumbar spine.

the moment arm of the upper body mass about the lumbar spine is increased in the case of relaxed sitting due to the backwards tilt of the pelvis. the flexion moment produced by the upper body weight and moment arm must be counterbalanced by an extension moment produced by the posterior back muscles. the larger the moment arm is the greater the muscle forces need to be. these muscles produce a compressive load on the spine which increases with increasing muscle force. so any change in posture that causes the upper body to be in a position offset from the lumbar spine effectively increases the load that it must carry

loading is highest with relaxed sitting, then bent forward standing, then erect sitting, then erect standing, then lying prone

similarly during lifting the load on the lumbar spine is increased in accordance with the increase in the moment arm produced by weight of the object being lifted. the moment arms of the weight of both upper body and the object are greater than when lifting the same object with knees bent. this bad lifting technique results in a considerably larger load on the lumbar spine which could be avoided by bending the knees and keeping the object closer to the body