Structure and Function of the MSK System

Question 1

components of a single joint system

Answer 1

bone - rigid links

joint - shape determiens kinds and range of movement

ligaments - provides stability

muscle - determines the kind and range of motions possible

motor and sensory nerves

Question 2

What is the role of the bones?

Answer 2

provide the stable levers on which muscles act to produce movement

responds to the forces of gravity and the force that muscles exert

bones must be built to resist the forces acting on them

Question 3

Wolff’s law

Answer 3

bone is laid down where needed and reabsorbed where it is not

lack of mobility or force results in lower bone mass and reduced strength

Question 4

What are the forces that are placed on the bones?

Answer 4

compression

tension

shear

torsion

bending

Question 5

What factors determine the ability of bone to resist applied loads?

Answer 5

age

disease

hormone levels

size of the force

direction of the force

rate at which force is applied

Question 6

stress fractures

Answer 6

fractures that result from repetitive application of small forces

Question 7

What materials that make up joints in order of least to most degree of movement?

Answer 7

fibrous > cartilaginous > synovial

Question 8

What are the compoents that determine the stability of joints?

Answer 8

articular shape

joint type

ligamentous arrangements

muscle tone

Question 9

What is the definition of joint stability?

Answer 9

the ability of a joint to maintain an appropriate functional position throughout its range of motion while carrying functional loads that produce oint contact forces of normal intensity between the articular surfaces

they key to joint health is joint stability

Question 10

What determines the range of motion of the skeleton?

Answer 10

articular shape, joint type, ligamentous arrangements, and muscle tone

synovial joints increase mobility

Question 11

fibrous joints

Answer 11

synostosis, syndesmosis

bones united by fibrous connective tissue

ex. sutures of the cranial vault, interosseous membrane

little to no movement

Question 12

cartilaginous joints

Answer 12

symmphysis, synchondrosis

bones united by cartilage of fibrocartilage

ex. intervertebral discs, smphysis pubis

some movement

Question 13

synovial joint

Answer 13

bones are separate, fibrous joint capsule lined with synovium forming synovial cavity

ends of bone ar lined with hyaline cartilage

the entire joint area is surrounded by a fibrous membrane enclosing the joint cavity

the inside of this cavity is lined with the synovial membrane, which produces the lubricating synovial fluid

ex. hip, shoulder, knee, elbow, ankle, wrist

diarthrosis - freely movable

Question 14

articular cartilage

Answer 14

cartilage that has no blood vessels, nerves, or lymphatics

nutrition is primarily by way of diffusion

limited ability to repair damage

Question 15

What are the types of join pathology?

Answer 15

lack of normal joint space

destruction of cartilate/bone

sclerotic bone

osteophyes

swollen, painful joints

Question 16

What does shape have to do with mobility of joints?

Answer 16

the rounder the joint, the more movement

spheroid - increased mobility, the surfaces are either concave or convex in all directions (spheroid is a subcategory of ovoid)

sellar - increased stability, saddle shaped, in ondirection the surface is concave, and in the other it is convex

Question 17

What are the three axes of motion at any joint?

Answer 17

medio-lateral axis (flexion-extension)

antero-posterior axis (abduction and adduction)

long axis of alimb (medial and lateral rotations, pronation-supination, inversion-eversion)

Question 18

What are the directions of movement of synovial joints?

Answer 18

all three axes of rotations

extension-flexsion

abduction-adduction

medial and lateral rotation

Question 19

What is the functional tradeoff between stability and mobility?

Answer 19

as mobility increases, stability decreases

Question 20

types of ovoid joints

Answer 20

spheroid

plane

condyloid

Question 21

spheroid joints

Answer 21

“ball and socket”

ex. shoulder, hip

usually multiaxial

flexion-extension

abduction-adduction

medial and lateral rotation

axial rotation

Question 22

plane joints

Answer 22

small sliding movements, usually biaxial

Question 23

condyloid joints

Answer 23

flexion-extension

usually biaxial - no axial rotation or circumduction

Question 24

sellar or hinge joints

Answer 24

saddle shaped, in one direction the surface is concave, and in the other it is convex

uniaxial saddles are sometimes called hinge joints

ex. humero-ulnar, upper ankle

usually uniaxial - more stable as a result

flexion-tension

no axial rotation

Question 25

What is the relationship between type of ligament and movement and stability?

Answer 25

stretchy/weak ligaments increase mobility

strong ligaments increase stability

Question 26

ligaments

Answer 26

tough bands of fibrous connective tissue that connect bones to other bones

movement theoretically allowed by joint shape may be prevented by ligaments

prevent damage to joints by limiting the range of movement in the normal direction of motion and preventing movements in unwanted directions

damage to a ligament is called a “sprain”, which is graded based on the degree of tear and resulting joint instability

Question 27

proprioception in the ligaments

Answer 27

contain sensory receptors in and around joints

many of these are locatred in the ligaments and tell the body the position of joints and limb segments

Question 28

avulsion injury

Answer 28

injury where little pieces of bone are torn off instead of liagments tearing

heals faster than a torn ligament because bone heals faster than ligaments

Question 29

Why do female athletes injure the ACL at a 4-6x higher rate than males in certain sports?

Answer 29

females have a higher valgus angle of the knee

smaller size of the intercondylar notch

ligament laxity at puberty increases in girls and decreases in boys

Question 30

Ehlers-Danlos syndrome

Answer 30

mutation in collagen genes or enzymes for processing collagen results in defective collagens with different material properties

results in hypermobility of joints because of unusually stretchable ligaments

Question 31

Marfan’s syndrome

Answer 31

defective fibrillin

also results in hypermobility of thejoints because of unusually stretchable

ligaments

Question 32

What is the relationship between movement and stability of joints?

Answer 32

normal muscle tone leads to increased mobility

rigid, tight muscles increase stability

Question 33

What are the factors that increase mobility of joints?

Answer 33

synovial joints

spheroid shapes

stretchy/weak ligaments

normal muscle tone

Question 34

What are the factors that increase stability of the joints?

Answer 34

not synovial

sellar shape

strong ligaments

rigid, tight, muscles

Question 35

What is the role of skeletal muscles?

Answer 35

generate force to cause movement or to counter external forces (ex. gravity)

stretch receptors in the spindle fibers of the muscles sense changes in the length of the muscle fibers and contribute to proprioception and the mediation of the stretch reflex

maintain posture and balance

40-50% of body weight

Question 36

origin vs. insertion

Answer 36

origin is usually more proximal and is fixed

insertion is usually distal and moves

Question 37

tendon

Answer 37

tough cords of closely packed collagenous fibers

force is concentrated in a limited area

ex. Achilles tendon

Question 38

aponeurosis

Answer 38

broad flat sheets of connective tissue - spread forces over wide area

ex. aponeurosis of latissimus dorsi

Question 39

Osgood-Schlater disease

Answer 39

repeated stress from contraction of the quadriceps femoris muscle is transmitted through the patellar tendon to the immature tibial tuberosity

this can cause avilsion fractures, most common in adults

Question 40

concentric contraction

Answer 40

change in muscle length - shorter while it contracts

Question 41

eccentric contraction

Answer 41

change in muscle length - longer while it generates tension

generates tension while stretching out, cause of muscle soreness (DOMS - delayed onset muscle soreness)

Question 42

isometric contraction

Answer 42

no change in muscle length - no movement, stabilization, constant tension

often counteracting gravity

Question 43

protagonist muscles

Answer 43

muscles primarily responsible for a movement

ex. biceps brachii is the protagonist in forelimb flexion at the elbow joint, as is brachialis

Question 44

antagonist muscles

Answer 44

performs the movement opposite to the protagonist

help stabilize and control the moving limb

ex. triceps brachii is the antagonist in forelimb flexion at the elbow joint

Question 45

synergist muscles

Answer 45

complements the action of the protagonist muscle

fixate intervening joint

counteract unwanted movement of protagonist

ex. when wrist is extended and fingers are flexed, greater gripping force - using wrist extenders to counteract movement of wrists to increase gripping strength

Question 46

What are the roles of nerves in the musculoskeletal system?

Answer 46

muscles must receive inntervation in order to contract

the integrity of the nervous system determines muscle strength and deep tendon reflexes

Question 47

What are the symptoms of damage of nerves that innervate muscles?

Answer 47

reduced or lost strength

changes in tone

changes in the deep tendon reflex

Question 48

Describe the basic pathway of the stretch reflex arc.

Answer 48

muscle stretch

stretch receptors sense stretch and conve information to the same spinal cord level

motor fibers for the muscles are activated, which causes muscle to contract to counteract the stretch