Chapter 1
Musculoskeletal Tissue
Tissues of the body
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Epithelial
Nervous
Connective
Muscle
Epithelial tissue

Two forms
– Membranous

Forms such structures as the outer layer of
the skin, the inner lining of the body cavities
and lumina, and the covering of visceral
organs
– Glandular

Specialized tissue that forms the secretory
portion of glands
Nervous tissue

Helps coordinate movements via a
complex motor control system of prestructured motor programs and a
distributed network of reflex pathways
mediated throughout the CNS
Connective tissue
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Found throughout the body
Divided into subtypes according to the
matrix that binds the cells
Includes bone, cartilage, tendons,
ligaments, and blood tissue
Muscle tissue


Responsible for the movement of materials
through the body, the movement of one
part of the body with respect to another,
and locomotion
Three types:
– Smooth
– Cardiac
– Skeletal
Connective Tissue

The primary types of connective tissue
cells are:
– Macrophages, which function as
phagocytes to clean up debris
– Mast cells, which release chemicals
associated with inflammation
– Fibroblasts, which are the principal cells
of connective tissue
Connective Tissue Proper
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1.
2.
3.
4.
5.
6.
Loose connective tissue
Dense regular connective tissue
Dense irregular connective tissue
Elastic connective tissue
Reticular connective tissue
Adipose connective tissue
Cartilage and bone tissue
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1.
2.
3.
Hyaline cartilage
Fibrocartilage
Elastic cartilage
Collagen and Elastin

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Collagen and elastin are vital constituents of
the musculoskeletal system
Collagen
– Maintains the structural integrity of various
tissues
– Provides tensile strength to tissues

Elastin
– Provides the tissues in which it is situated with
elastic properties
Collagen and Elastin

Collagenous and elastic fibers are
sparse and irregularly arranged in
loose connective tissue, but are tightly
packed in dense connective tissue
– Fascia is an example of loose connective
tissue
– Tendons and ligaments are examples of
dense regular connective tissue
Tendons

Cordlike structures that function to
attach muscle to bone and to transmit
the forces generated by muscles to
bone in order to achieve movement or
stability of the body in space
Tendons

The fascicles of tendons are held together
by loose connective tissue called endotenon
– Endotenon contains blood vessels, lymphatics
and nerves, and permits longitudinal movements
of individual fascicles when tensile forces are
applied to the structure

The connective tissue surrounding groups of
fascicles and/or the entire structure is called
the epitenon
Myotendinous junction
(MTJ).
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The site where the muscle and tendon meet
Very vulnerable to tensile failure, especially
biceps and triceps brachii, the rotator cuff
muscles, the flexor pollicis longus, the
peroneus longus, the medial head of the
gastrocnemius, the rectus femoris, the
adductor longus, the iliopsoas, the
pectoralis major, the semimembranosus,
and the whole hamstrings group
Skeletal ligaments

Skeletal ligaments are fibrous bands of
dense connective tissue that connect
bones across joints
– Contribute to the stability of joint function
by preventing excessive motion
– Act as guides to direct motion
– Provide proprioceptive information for
joint function
Ligament pathology

Ligament injuries are graded according
to severity
– First-degree (mild)
– Second-degree (moderate)
– Third degree (complete)
Ligament pathology

First-degree sprain
– Minimal loss of structural integrity
– Little or no swelling
– Minimal bruising
– Minimal functional loss
– Early return to training
Ligament pathology

Second-degree sprain
– Significant structural weakening
– Some abnormal motion
– More bruising and swelling
– Tendency for recurrence
– Need protection from risk of further injury
– May need modified immobilization
Ligament pathology

Third-degree sprain
– Loss of structural integrity
– Marked abnormal motion
– Significant bruising
– Needs prolonged protection
– Surgery may be considered
– Permanent functional instability a
possibility
Bone
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A highly-vascular form of connective tissue
Composed of collagen, calcium phosphate,
water, amorphous proteins, and cells
The collagen of bone is produced in the
same manner as that of ligament and
tendon, but by a different cell, the
osteoblast
Bone

There are 206 bones in the human
skeleton
– 177 of these bones are involved in
voluntary movement
– 29 of these bones are immobile
Bone

The function of bone is to:
– Provide support
– Enhance leverage
– Protect vital structures
– Provide attachments for both tendons
and ligaments
– Store minerals, particularly calcium.
Two Components of the
Skeleton
Axial
Skeleton
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Skull
Spinal Column
Sternum
Ribs
Appendicular
Skeleton
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Upper Extremity
Lower Extremity
Major Bone Types
1.
2.
3.
4.
Long
Short
Flat
Irregular
Long Bones
Characteristics
– Possess a cylindrical shaft and medullary
canal
– Relatively broad ends
– Thick walled shaft
Long Bones of Skeleton
Upper Extremity
1. Clavicle
2. Humerus
3. Ulna
4. Radius
5. Metacarpals
6. Phalanges
Lower Extremity
1. Femur
2. Tibia
3. Fibula
4. Metatarsals
5. Phalanges
Short Bones

Relatively short, compact and solid
structures
Short Bones of Skeleton
Upper Extremity
Carpals (wrist)
Lower Extremity
Tarsals (ankle)
Flat Bones
Examples:
 Sternum
 Scapulae
 Ribs
 Pelvic bones
 Patellas
Irregular Bones
Examples:
 Bones of Spinal Column
– The 24 vertebrae
– Sacrum
– Coccyx
Characteristics of Bone
Epiphyses
–
–
Each bone has two epiphysis, which are layers
of cartilage at the ends of the bones
The presence of an epiphysis indicates
incomplete bone growth
Articulation
–
–
Connection point of bones (joint)
Type of articulation helps determine the type
and amount of motion possible
Pathology of bone
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Osteoporosis
– Maybe primary or secondary
Osteomalacia
– Characterized by incomplete mineralization of
normal osteoid tissue
Osteomyelitis
– An acute or chronic inflammatory process of the
bone and its marrow secondary to infection
Paget’s disease (osteitis deformans)
– An osteometabolic disorder
Cartilage Tissue

Cartilage tissue consists of cartilage cells
called chondrocytes
– Chondrocytes are specialized cells that are
responsible for the development of cartilage, and
the maintenance of the extracellular matrix

Cartilage tissue exists in three forms:
– Hyaline
– Elastic
– Fibrocartilage
Hyaline cartilage
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Covers the ends of long bones and,
along with the synovial fluid that
bathes it, provides a smooth and
almost frictionless articulating surface
The most abundant cartilage within
the body
Elastic cartilage

A very specialized connective tissue,
primarily found in locations such as
the outer ear, and portions of the
larynx
Fibrocartilage
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Fibrocartilage functions as a shock
absorber in both weight bearing, and
non-weight bearing joints
Examples include the symphysis pubis,
the intervertebral disc, and the menisci
of the knee
Pathology of cartilage
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Osteoarthritis
– Can be primary or secondary
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Osteochondritis dissecans
– And osteochondral fracture
Joints
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Joints are regions where bones are capped
and surrounded by connective tissues that
hold the bones together and determine the
type and degree of movement between
them
Joints may be classified as diarthrosis, which
permit free bone movement and
synarthrosis, in which very limited or no
motion occurs
Joint Classifications
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Synarthrodial (immovable)
Amphiarthrodial (slightly movable)
– Syndesmosis
– Synchondrosis
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Diarthrodial (freely movable)
Diarthrosis

This type of joint generally unites long
bones and has great mobility.
Examples include but are not limited
to the hip, knee and shoulder and
elbow joints
Diarthrodial Joint
Characteristics
1.
2.
3.
4.
5.
Articular cavity present
Joint encased within ligamentous capsule
Capsule lined with synovial membrane
Secretion of synovial fluid, which lubricates
the joint
Smooth articular surfaces, which are
covered with cartilage
Diarthrodial Joint
Classifications
1.
2.
3.
4.
5.
6.
Ball and socket (spheroidal; enthrodial)
Hinge (ginglymoid)
Pivot (trochoid)
Condyloid (ellipsoidal)
Irregular (arthrodial: plane)
Sellar (saddle)
Ball-and-Socket Joint
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Surface:
– Spherical head fits into
– Cup cavity of other bone
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Motion: Triaxial
– Flexion/Extension
– Abduction/Adduction
– Circumduction
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Example:
– Hip
– Shoulder
Hinge (ginglymus) Joint
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Surface:
– 1 surface spool-like
– 1 surface is concave
and fits over spool
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Motion: Uniaxial
– Concave surface glides
partially around the
spool-like process
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Example: humero-ulnar joint
Pivot (trochoid) Joint
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Surface
– Peg-like pivot
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Motion: Uniaxial
– Rotation only
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Example:
– Atlanto-axial
– Radioulnar
Condyloid Joint
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Surface:
– Oval or egg-shaped
convex surface
– Fits into a reciprocally
shaped concave surface
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Motion: Biaxial
– Forward/backward
– Side to Side
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Example:
– wrist
Irregular Joint
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Surface
– Irregularly shaped,
– usually flat or slightly
curved.
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Motion:
– Gliding (non-axial)
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Examples: some intercarpal joints
Saddle Joint
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Surface:
– Ends of both bones are convex
– Like western saddle
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Motion: biaxial
– Flexion/Extension
– Abduction/Adduction
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Example:
– Carpometacarpal
joint of thumb
Diarthrodial Joint
Classifications and Axes
Number of
Axes
Classificatio
n
0
1
Nonaxial Uniaxial
Irregular
Hinge/
Pivot
2
Biaxial
3
Triaxial
Condyloid
/
Saddle
Ball
&
Socket
Synovial joints

The bones that articulate in a synovial
joint are capped with a smooth layer
of hyaline cartilage called articular
cartilage.
Synarthrosis

There are three major types of synarthroses
based on the type of tissue uniting the bone
surfaces:
– Synostosis joints: united by bone tissue.
Examples include sutures and gomphoses
– Synchondrosis joints: joined by either hyaline or
fibrocartilage. Examples include the epiphyseal
plates of growing bones and the articulations
between the first rib and the sternum
– Syndesmosis joints: joined together by an
interosseous membrane. Examples include
joints such as the symphysis pubis
Synarthrodial Joint
Characteristics
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Surface:
– Bones are united by fibrous tissue continuous
with periosteum
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Motion:
– None permitted
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Example:
– Sutures of the Skull
Amphiarthrodial Syndesmosis Joint
Characteristics
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Surface:
– Ligamentous connection between bones
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Motion:
– Minimal movement between bones
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Examples:
– Inferior tibiofibular joint
Amphiarthrodial Synchondrosis Joint
Characteristics
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Surface:
–
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Motion:
–
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bones are united by
fibrocartilage
Bend &Twist
Example:
–
Articulations between
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bodies of vertebrae
Symphysis pubis
Costochondral joints of the ribs w/ sternum
Bursa
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Flattened sac-like structures
Closely associated with some synovial
joints
Produce small amounts of fluid
allowing for smooth and almost
frictionless motion between contiguous
muscles, tendons, bones, ligaments,
and skin
Skeletal Muscle

A single muscle cell is called a muscle fiber
or myofiber
– Individual muscle fibers are wrapped in a
connective tissue envelope called endomysium
– Bundles of myofibers which form a whole muscle
(fasiciculus) are encased in the perimysium. The
perimysium is continuous with the deep fascia
– Groups of fasiciculus are surrounded by a
connective sheath called the epimysium
Machinery of movement
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Each myofibril contains many fibers
called myofilaments, which run parallel
to the myofibril axis
– The myofilaments are comprised of two
protein filaments: actin (thin) and myosin
(thick)
– The A bands are composed of myosin
filaments, while the I bands are
composed of actin filaments
Machinery of movement
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The actin filaments of the I band
overlap into the A band, giving the
edges of the A band a darker
appearance than the central region (H
band), which only contains myosin
At the center of each I band is a thin
dark Z line. A sarcomere represents
the distance between each Z line
Machinery of movement
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When a muscle contracts isotonically:
– The distance between the Z lines decreases
– The I band and H bands disappear
– The width of the A band remains unchanged

This shortening of the sarcomeres is not
produced by a shortening of the actin and
myosin filaments, but by a sliding of actin
filaments over the actin filaments, which
pulls the Z lines together
Machinery of movement

Cross-bridges
– Structures that serve to connect the actin and
myosin filaments
– The myosin filaments contain two flexible hingelike regions, which allow the cross-bridges to
attach and detach from the actin filament
– During contraction, the cross-bridges attach and
undergo power strokes, which provide the
contractile force
– During relaxation, the cross-bridges detach
Machinery of movement

The regulation of cross-bridge attachment
and detachment is a function of two
proteins found in the actin filaments:
tropomyosin and troponin
– Tropomyosin attaches directly to the actin
filament
– Troponin attaches to the tropomyosin, rather
than directly to the actin filament

For contraction to take place, the
tropomyosin must be moved
The energy for movement

The energy required to power
muscular activity is derived from the
hydrolysis of ATP to ADP and inorganic
phosphate.
The energy for movement

Three major energy systems:
– Phosphagen system (anaerobic)
– Glycolysis system (anaerobic)
– Oxidative system (aerobic)
Neuromuscular Junction
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Each muscle fiber is innervated by a somatic
motor neuron
One neuron and the muscle fibers it
innervates constitute a motor unit, or
functional unit of the muscle
Each motor neuron branches as it enters the
muscle to innervate a number of muscle
fibers
The area of contact between a nerve and a
muscle fiber is known as the motor
endplate, or neuromuscular junction
Muscle contraction
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Release of a chemical acetycholine from the axon
terminals at the neuromuscular junctions
Electrical activation of the skeletal muscle fibers
Release of Ca2+ from the terminal cisternae
The released Ca2+ diffuses into the sarcomeres,
binds to troponin, displaces the tropomyosin, and
allows the actin to bind with the myosin crossbridges
At the end of the contraction, the sarcoplasmic
reticulum actively accumulates Ca2 which requires
the degradation of adenosine triphosphate (ATP)
to adenosine diphosphate. (ADP)
Muscle Fiber Types

Four different types of muscle fibers
have been recognized within skeletal
muscle:
– Type I (slow twitch red oxidative)
– Type IIa (fast twitch red oxidative)
– Type IIb (fast twitch white glycolytic)
– Type IIc (fast twitch intermediate)
Slow twitch Fibers

Slow twitch fibers are richly endowed
with mitochondria and have a high
capacity for oxygen uptake
– Suitable for activities of long duration or
endurance, including posture
Fast Twitch Fibers

Fast twitch fibers can be separated
into those that have a high
complement of mitochondria (Type
IIa), those that are mitochondria poor
(Type IIb) and those that display a
mixture of characteristics (Type IIc)
– Fast twitch fibers are suited to quick,
explosive actions, including such activities
as sprinting
Pathology of muscle

Muscle strains may be classified
according to their severity:
– Mild (first degree): involves a tear of a
few muscle fibers with minus swelling and
discomfort
– Moderate (second degree): involves
greater damage to the muscle and clear
loss of strength
– Severe (third degree): involves a tear
extending across the whole muscle belly
Pathology of muscle

Myositis ossificans: is an aberrant
reparative process that causes benign
heterotopic ossification in soft tissue