17605347 skeletal bio mechanics slide show

7/30/2019 17605347 Skeletal Bio Mechanics Slide Show

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Biomechanics I 1



Biomechanics I 2

Axial vs. Appendicular

Axial skeleton refers to the body of

the animal

Appendicular refers to the limbs



Biomechanics I 3



Biomechanics I 4

Introduction

Axial skeleton Forms the long

axis of the body 80 bones in three

major regions skull vertebral column

bony thorax• Ribs• Sternum

Appendicular Bones of upper &

lower extremitiesand girdles

126 bones in threemajor regions Girdles

• Shoulder girdle

• Pelvic girdle

upper extremity

lower extremity



Biomechanics I 5

Classification of Bones



Biomechanics I 6

short bones: approximately cubical;

include the carpals and tarsals

flat bones: protect organs & provide

surfaces for muscle attachments;

include the scapulae, sternum, ribs,patellae, some bones of the skull

Types of bones



Biomechanics I 7

irregular bones: have different shapes

to serve different functions; include

vertebrae, sacrum, coccyx, maxilla long bones: form the framework of

the appendicular skeleton; include

humerus, radius, ulna, femur, tibia,fibula

Types of bones



Biomechanics I 8

Joints

Classify by function Synarthroses

• Joints with little or no movement

Amphiarthroses

• Slightly moveable joints

Diarthroses / Synovial joint

• Freely moveable joints



Biomechanics I 9



Biomechanics I 10

diarthroses or synovial: (freely movable)characterized by:

articular cartilage - a protective

layer of dense white connective

tissue covering the articulating bone

surfaces articular capsule - a double-layered

membrane that surrounds the joint

Joint Architecture



Biomechanics I 11

diarthroses or synovial: (freely movable)

characterized by:

synovial fluid - a clear, slightly yellowliquid that provides lubrication insidethe articular capsule

associated bursae - small capsulesfilled with synovial fluid that cushionthe structures they separate

Joint Architecture



Biomechanics I 12

Functions of articular cartilage

distributing loads over joint surfaces

improving the fit of articulations

limiting slip between articulating bones

protecting the joint periphery

lubricating the joint absorbing shock at the joint



Biomechanics I 13

Types of Synovial Joints

Plane joints

Articular surfaces

are flat and allowshort slipping or

gliding movements

Intercarpal and

intertarsal joints



Biomechanics I 14

Hinge joints Movement

resembles a door

hinge

Elbow joint – ulna

and humerus;

Interphalangeal joints




Biomechanics I 15


Pivot joints Rounded end of one

bone protrudes into

a ring formed byanother bone or byligaments of thatbone.

Proximal radioulnar joint

Atlas-axial joint



Biomechanics I 16

Condyloid joints Oval articular

surface of onebone fits into acomplementarydepression onanother.

Radiocarpal joints Metacarpophalang

eal joints




Biomechanics I 17


Saddle joints Each articular

surface has convex

and concave areasEach articularsurface is saddle-shaped.

Carpometacarpal joints of thethumbs



Biomechanics I 18


Ball-and-Socket joints Spherical or semi-

spherical head ofone bone

articulates with thecuplike socket ofanother.

Allow for much

freedom of motion. Shoulder and hip

joints



Biomechanics I 19

Joint Stability

ability of a joint to resist abnormaldisplacement of the articulating bones

factors increase joint stability a closely reciprocating match of the

articulating bone surfaces

a strong array of ligaments andmuscle tendons crossing the joint



Biomechanics I 20

Factors increase joint

stability articulating bone surfaces

wide contact area - high stability different among joints and

individuals

change in joint angle - change incontact area - change in stability



Biomechanics I 21

Connective tissues crossing the joint

weak and lax connective tissues -

low stability strengthening of tissues - increase

in stability

muscle activity and fatigue -decrease in stability

Factors increase jointstability



Biomechanics I 22

Joint Flexibility

a description of the relative ranges ofmotion allowed at a joint in differentdirections

range of motion (ROM) - the anglethrough which a joint moves from

anatomical position to the extremelimit of segment motion in a particulardirection



Biomechanics I 23

Factors influence jointflexibility

Shapes of articulating bone surfaces Intervening muscle or fatty tissue

Laxity Extensibility of collagenous tissue and

muscles

Fluid contents in cartilagenous disc Temperature of collageneous tissuesStretching program



Biomechanics I 24

Types of muscle



Biomechanics I 25

Skeletal muscle

Characteristics of skeletal muscle;

Extensibility - ability to be

stretched or to increase in length

•Viscoelasticity - having the

ability to stretch or shorten overtime



Biomechanics I 26

Skeletal muscle

Characteristics of skeletal muscle;

Contractility - ability to contract

(develop tension) Excitability (Irritability ) - ability to

respond to a stimulus

Elasticity - ability to recoil to normallength following a stretch



Biomechanics I 27

Elastic components

Parallel elastic component (PEC) passive elastic property of muscle

derived from muscle membranes

(epimysium, perimysium,endomysium, sarcolemma)

Series elastic component (SEC)

passive elastic property of musclederived from the tendons (primarilyresponsible for elasticity)



Biomechanics I 28

Elastic components

Contractile component (CC)

actual part of muscle that contracts(actin and myosin)



Biomechanics I 29

Motor unit

single motor neuron and all fibers it

innervates

considered the functional unit of the

neuromuscular system



Biomechanics I 30



Biomechanics I 31

Basic fiber arrangement

parallel fiber arrangement: fibers areroughly parallel to the longitudinal axis

of the muscle Convergence: fan-shaped

pennate fiber arrangement: short

fibers attach to one or more tendonswithin the muscle



Biomechanics I 32

Arrangements of Muscle Fibers



Biomechanics I 33

Types of muscle contraction

isometric contraction: muscle length

does not change

concentric contraction: muscle lengthdecreases

eccentric contraction: muscle length

increases



Biomechanics I 34

Skeletal Muscle Function

agonist: acts to cause a movement

antagonist: acts to slow or stop a

movement stabilizer: acts to stabilize a body part

against some other force

neutralizer: acts to eliminate anunwanted action produced by an agonist



Biomechanics I 35

Tension present in a stretched muscle is

the sum of the active tension providedby the muscle fibers and the passive

tension provided by the tendons and

membranes

Muscle’s length-tensionrelationship



Biomechanics I 36

T e n s i o n

Length (% of resting length)

50 100 150

ActiveTension

PassiveTension

TotalTension



M l ’ f l i



Biomechanics I 38

Muscle’s force-velocityrelationship

17605347 skeletal bio mechanics slide show

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