Download THE MUSCULOSKELETA L SYSTEM THE

Università degli Studi di Catania
Facoltà di Medicina e Chirurgia
Corso di laurea in Fisioterapia
Equipollenza
THE
MUSCULOSKELETA
L SYSTEM
Inglese Scientifico
Prof.ssa Mariagrazia Torrisi
THE MUSCULOSKELETAL
SYSTEM
15 October 2008
Phsiotherapy lesson 1
INTRODUCTION
MUSCLES
BONES
JOINTS
LIGAMENTS
TENDONS AND
BURSAS
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There are three types of muscles:
skeletal
smooth
cardiac (heart).
Two of these kinds—skeletal and smooth—are part of the
musculoskeletal system.
The musculoskeletal system provides
form, stability and movement to the
human body. It consists of the
body's bones (which make up the
skeleton),
muscles,
tendons,
ligaments, joints, cartilage, and
other connective tissue.
tissue The term
"connective tissue" is used to
describe the tissue that supports
and binds tissues and organs
together. Its chief components are
elastic fibers and collagen, a protein
substance
Phsiotherapy lesson 1
Phsiotherapy lesson 1
MUSCLES
Introduction
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skeletal muscles
is what most people think of as muscle, the type that can be
contracted to move the various parts of the body. Skeletal
muscles are bundles of contractile fibers that are organized
in a regular pattern, so that under a microscope they appear
as stripes (hence, they are also called striped or striated
muscles). Skeletal muscles vary in their speeds of
contraction. Skeletal muscles, which are responsible for
posture and movement, are attached to bones and arranged in
opposing groups around joints. For example, muscles that
bend the elbow (biceps) are countered by muscles that
straighten it (triceps). These countering movements are
balanced. The balance makes movements smooth, which
helps prevent damage to the musculoskeletal system.
Skeletal muscles are controlled by the brain and are
considered voluntary muscles because they operate with a
person's awareness. The size and strength of skeletal muscles
are maintained or increased by regular exercise. In addition,
growth hormone and testosterone help muscles grow in
childhood and maintain their size in adulthood.
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Muscoloskeletal system(front view)
Smooth muscles
Smooth muscles control certain bodily functions that
are not readily under a person's control. Smooth muscle
surrounds many arteries and contracts to adjust blood
flow. It surrounds the intestines and contracts to move
food and feces along the digestive tract. Smooth muscle
also is controlled by the brain but not voluntarily. The
triggers for contracting and relaxing smooth muscles are
controlled by the body's needs, so smooth muscles are
considered involuntary muscle because they operate
without a person's awareness.
Cardiac muscle
Cardiac muscle forms the heart and is not part of the
musculoskeletal system. Like skeletal muscle,
cardiac muscle has a regular pattern of fibers that
also appear as stripes under a microscope.
However, cardiac muscle contracts and relaxes
rhythmically without a person's awareness.
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BONES
Muscoloskeletal system(back view
• Bone, although strong, is a constantly changing tissue that has several functions.
Bones serve as rigid structures to the body and as shields to protect delicate internal
organs. They provide housing for the bone marrow, where the blood cells are
formed. Bones also maintain the body's reserve of calcium. In children, some bones
have areas called growth plates. Bones lengthen in these areas until the child
reaches full height, at which time the growth plates close. Thereafter, bones grow in
thickness rather than in length, based on the body's need for additional bone
strength in certain areas.
• Bones have two shapes: flat (such as the plates of the skull and the vertebrae) and
tubular (such as the thighbones and arm bones, which are called long bones). All
bones have essentially the same structure. The hard outer part (cortical bone)
consists largely of proteins, such as collagen, and a substance called hydroxyapatite,
which is composed mainly of calcium and other minerals. Hydroxyapatite is largely
responsible for the strength and density of bones. The inner part of bones
(trabecular bone) is softer and less dense than the hard outer part. Bone marrow is
the tissue that fills the spaces in the trabecular bone. Bone marrow contains
specialized cells (including stem cells) that produce blood cells. Blood vessels
supply blood to the bone, and nerves surround the bone.
• Bones undergo a continuous process known as remodeling (see Osteoporosis). In
this process, old bone tissue is gradually replaced by new bone tissue. Every bone in
the body is completely reformed about every 10 years. To maintain bone density
and strength, the body requires an adequate supply of calcium, other minerals, and
vitamin D and must produce the proper amounts of several hormones, such as
parathyroid hormone, growth hormone, calcitonin, estrogen, and testosterone.
. Activity (for example, weight-bearing exercises for the legs) helps bones
strengthen by remodeling. With activity and optimal amounts of hormones,
vitamins, and minerals, trabecular bone develops into a complex lattice structure
that is lightweight but strong.
• Bones are covered by a thin membrane called the periosteum. Injury to bone
transmits pain because of nerves located mostly in the periosteum. Blood enters
bones through blood vessels that enter through the periosteum.
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JOINTS
•
•
•
According to their structure and the range
of movements they allow,
Joints are the junction between two or more bones. Some joints do
not normally move, such as those located between the plates of the
skull. Other joints allow a large and complex range of motion. The
configuration of a joint determines the degree and direction of
possible motion. For example, the shoulder joints, which have a balland-socket design, allow inward and outward rotation as well as
forward, backward, and sideways motion of the arms. Hinge joints of
the knees, fingers, and toes allow only bending (flexion) and
straightening (extension
There are two important kinds of joint with quite different functions.
Between the secondary centres of ossification or epiphyses of the
bones and the metaphyses are joints where movement is positively
discouraged: between the femur and the tibia is the synovial knee
joint proper, where movement is positively encouraged.
So where two or more bones come together we find a joint: the range
of movement at joints may be zero or a just a little give, or extremely
large.
The components of joints provide stability and reduce the risk of
damage from constant use. In a joint, the ends of the bones are
covered with cartilage—a smooth, tough, resilient, and protective
tissue composed of collagen, water, and proteoglycans that reduces
friction as joints move. (Collagen is a tough fibrous tissue;
proteoglycans are substances that provide the cartilage's resilience.)
Joints also have a lining synovial tissue) that encloses them to form
the joint capsule. Cells in the synovial tissue produce a small amount
of clear fluid (synovial fluid), which provides nourishment to the
cartilage and further reduces friction while facilitating movement
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joints are classified into:
FIBROUS AND CARTILAGINOUS
JOINTS where two bones are separated by a
deformable intermediate
Fibrous joints.
Sutures
Gomphoses
Syndesmosis:
SYNOVIAL JOINTS
where one surface slides freely over
another
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FIBROUS JOINTS
•
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SYNOVIAL JOINTS
Fibrous joints. The joint between the bony shaft and
cartilage at the ends of long bones. is a synchondrosis, a
cartilage sandwich with bone on either side: bone and
cartilage fit together perfectly and the whole thing is cup
shaped. If movement occurs the growing bone will be
damaged (slipped epiphysis) and this is countered by putting
in a long nail to fix it again.
Sutures: are limited to the skull. They resemble a
synchondrosis, but with fibrous tissue instead of cartilage
between the bones. Sutures are necessary for skull growth:
consequently well marked in the young less so in the adult.
The only movement in sutures is at birth when the cranial
bones overlap to allow passage through the maternal pelvis.
After this movement is discouraged by increasing complexity
of the suture, which becomes serrated or denticulate. Later in
life, when growth is complete they fuse.
gomphoses: are peg and socket joints as seen between teeth
and jaws. The joint is maintained by the periodontal ligament
which gives only a little to act as a shock absorber when we
bite on a ball bearing.
syndesmosis: only one of these in the body, the inferior
tibio-fibular joint. In this type there is a little movement,
limited by a tight ligament. Since many joints are limited by
ligaments this is probably a special definition we can do
without. symphysis: two bones united by cartilage, but
designed to give a bit. The symphysis pubis with ligaments
and fibrocartilage is normally closed, but opens in childbirth
due to hormonal influences.
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Inside the knee.............
•
The knee is designed for its own protection. It is completely
surrounded by a joint capsule that is flexible enough to allow
movement but strong enough to hold the joint together. The
capsule is lined with synovial tissue, which secretes synovial
fluid to lubricate the joint. Wear-resistant cartilage covering
the ends of the thighbone (femur) and shinbone (tibia) helps
reduce friction during movement. Pads of cartilage (menisci)
act as cushions between the two bones and help distribute
body weight in the joint. Fluid-filled sacs (bursas) provide
cushioning between structures such as the tibia and the
tendon attached to the kneecap (patellar tendon). Five
ligaments along the sides and the back of the knee reinforce
the joint capsule, adding stability. The kneecap (patella)
protects the front of the joint.
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Synovial joints
have different parameters. Joint surfaces almost in contact
but discontinuous, as a great range of movement is often
possible, and the surfaces slide over each other. The sliding
surfaces are covered with a thin layer of cartilage. This
gives a coefficient of friction of <0.002. The joint cavity is
sealed by a synovial membrane which secretes synovial
fluid, a lubricant and nutrient. Around this, in turn, is a
tough fibrous joint capsule which keeps the ends of the
bones in proper orientation. This is often locally thickened to
form joint ligaments. The synovial cavity is very small
between articular surfaces but larger round the edges where
it may form a bursa, a sack-like extension which may be in
contact with the joint cavity.
Various inclusions may be present in the joint cavity: a
tendon may pass through, sheathed in synovial
membrane. Fat pads may be present, packing the
large gaps which occur in some joints between bone
ends. Pieces of cartilage are also found, in addition to
articular cartilage. These may form
1. a labrum or lip deepening a bony socket
2. menisci - incomplete discs or crescents increasing
the size of articular surfaces
3. complete, or nearly complete articular discs of
fibrocartilage. This will convert a joint into two in
parallel, which can then move in independent
directions. The temporomandibular joint of the jaw is a
good example of this.
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Movements in synovial joints.
These can be very extensive.The shoulder joint is particularly
free
and
able
to
move
around
three
axes.
Various schemes of classification of synovial joints have been
used according to;
•Complexity Many joints possess only two articular surfaces and
are therefore simple. Usually one surface is convex or larger than
the other and termed male. Compound joints have more than one
pair of articulating surfaces (e.g. the elbow has two male
surfaces on the humerus which articulate with female surfaces on
radius and ulna) and are thus compound. Complex joints have an
intracapsular disc or menisci.
•Degrees of freedom A joint which moves substantially in one
plane (like an elbow) is uniaxial. One which moves in two planes
is biaxial, one which moves in three is triaxial. A ball and socket
is multiaxial, but is equivalent to a triaxial as it has three degrees
of freedom i.e. all movements can be reduced to XYZ axes. Not
a good classification as there are often small but vital movements
in other planes (e.g. knee rotation at end of flexing) and cannot
.
take account of sliding movement
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•
•
•
Shape
Probably the most widely used classification, but still tries to
simplify.
Surfaces hinge joints: permit flexion and
extension (knee) pivot joints: allow rotation (superior radioulnar) plane joints: have flat surfaces and allow gliding in
several directions (carpus and tarsus) condylar joints:
usually regarded as two hinge joints with separate
articulations (TMJ) saddle joints: have surfaces shaped like
two saddles - allow movement in two planes at right angles
and a little rotation (base of thumb) ball and socket: allows
very free movement around any axis through ball (hip)
ellipsoid: ball and sockets which are not round : rotation
therefore impossible (radiocarpal joint)
Functional approach. This is the best classification as
regards understanding what is going on. All above
classifications are approximations and have holes in them
which fit uneasily.
joint movement is always made up of:–
–
–
–
gliding - of one surface over another- slide
angulation - flexion, extension etc. - roll
rotation about axis of bone - spin
approximation of soft parts.
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Movement always occurs at articular surfaces, which are
never planes nor spheres nor cones but always spheroids egg shapes, either male or female i.e. convex or concave. A
point moving between A and B on a surface can take the
shortest great circle route a chord, or can take a longer,
prettier arc. Any movement can be described by a trigone (a
bendy triangle) or three arcs. The imaginary point which
traces these movements is the end of the axis of rotation. In
the simplest case this is the end of the long axis of the bone:
for something like a femur it obviously isn't. Lets try this on
a real movement, extending the knee. If we hold the tibia still
and move the femur extension has three bits.
– the femur rolls on the tibia
– the femur slides posteriorly
– the femur spins to lock the joint.
The third of these is most important because it tells us
something about how joints work. Take an egg and cut it in
half. The resulting curved surface has a variable radius of
curvature. If we try to fit this to another spheroid we see that
it only fits well at one point. Elsewhere there are wedgeshaped gaps and smaller areas of contact. Joints exploit this:
the position of best fit, or close packed position usually
occurs at the end of the range of habitual movement. As a
joint approaches this position ligaments are stretched and
often some spin is imparted by them to screw the joint home.
In this position the joint is virtually
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LIGAMENTS
•
abolished: in practice it is only fully reached under strain and
may damage articular surfaces and pull ligaments. So usually
it is approached but not realised. This position is comfortable
because it uses little muscular energy and can be maintained
for long periods. The loose packed position is also important
because it allows
– loosely fitting surfaces to spin, roll and slide
– a reduced area of contact, so little friction
– wedge shaped gaps, continually changing circulate
synovial fluid like a peristaltic pump.
• Limitation of movement is also important. Usually
achieved by
– tension in ligament, which have strain and pain receptors
– tension of muscles around a joint - passive resistance to
stretch followed by reflex contraction when stimuli from
mechanoreceptors becomes critical. These explain
Hilton's law: that joints and the muscles acting on them
share a nerve supply. Paralysis of muscles thus affects
joints. In spastic paralysis muscle tone is increased and
movement restricted. In other paralyses joints become
lax, flail joints or actually disrupted. Charcot elbow in
syphilis.
– Running out of articular surface.
– approximation of soft parts.
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Ligaments are tough fibrous cords composed of connective
tissue that contains both collagen and elastic fibers. The elastic
fibers allow the ligaments to stretch to some extent. Ligaments
surround joints and bind them together. They help strengthen
and stabilize joints, permitting movement only in certain
directions. Ligaments also connect one bone to another (such
as inside the knee).
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TENDONS AND BURSAS
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Nerve/Muscle Connections
• Tendons are tough bands of connective tissue made up
mostly of a rigid protein called collagen. Tendons firmly
attach each end of a muscle to a bone. They are often located
within sheaths, which are lubricated to allow the tendons to
move without friction.
•
• Bursas are small fluid-filled sacs that can lie under a
tendon, cushioning the tendon and protecting it from injury.
Bursas also provide extra cushioning to adjacent structures
that otherwise might rub against each other, causing wear
and tear—for example, between a bone and a ligament or a
bony prominence and overlying skin (such as in the elbow,
kneecap, or shoulder area).
• Tendonitis is the inflammation, irritation, and swelling of a
•
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tendon.
It can occur as a result of injury, overuse, or with aging as
the tendon loses elasticity. Any action that places prolonged
repetitive strain on the forearm muscles can cause tendonitis.
The most common symptom of tendonitis is pain,
tenderness, and the increase of pain with movement.
Nerves, known as sensory neurons, come from every part of the body to carry
impulses to the brain or spinal cord concerning the condition of every nook
and cranny in the body, including the muscles. In the same way, motor neurons
send impulses to the muscles, often through intermediate connections or
"interneurons" in the spinal cord. These messages cross the gap at a junction
between nerves and muscles, setting off a chain of events that ends in
contraction. Within a second, millions of impulses reach the motor neurons.
Some of the impulses are sent from various parts of the brain and spinal cord;
some come from sense organs located in the joints, ligaments, and tendons;
and some come from the muscles themselves. The seeds of movement are
sown by the brain, in its primary cortex, an area of the brain's wrinkled surface
which spans both cerebral hemispheres. Another patch of cortex directly in
front of the primary area also houses neurons which are involved in
movement. This area is thought to be important to speech and delicately
coordinated movements such as those performed by the hand. Electrical
impulses from many regions of the brain feed into the motor areas. The brain
must collect and analyze all the sensory messages it receives before it can
direct a coordinated movement. This interplay is continuous and elaborate sight, sound, smell, pressure and pain are all important, but so are messages
bringing information about the angles and position of joints, the length and
tension of muscles, or even the speed of movements. At every point along the
descent from brain to muscle, impulses can influence interneurons to vary the
precision of muscular control. An average motor neuron may have as many as
15,000 connections each, providing information from all over the body. Some
parts, like the back, which have a limited precision of motion, are only
equipped with a few - perhaps 50,000. Hand muscles, which perform very
delicate and precise movements are driven by about 200,000 neurons. A
second major transmission network produces contractions of groups of
muscles and is responsible for larger muscular functions, such as running,
walking or swimming. A "muscle spindle" is a sensory end organ in a muscle
that is sensitive to stretching of the muscle.
•
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Nerve/muscles connection
Nerve/Muscle Connections
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