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Musculokeletal Phyt I > Week 2 - Lecture 1 - Tissue Mechanics and Injury > Flashcards

Week 2 - Lecture 1 - Tissue Mechanics and Injury Flashcards

1
Q

Explain why the human body must adapt in appearance and composition in response to functional demand. How can these demands change?

A

• Our musculoskeletal systems must adapt in appearance and composition in
response to functional demand
• These demands can change with immobilization, inactivity, or training
• Understanding the functional demands and the tissues’ response, we can modify
the stresses on joint structure during rehabilitation to optimize function

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2
Q

What are tissues (definition)?

What are the four different types of tissue?

A

• An aggregate of cells that
have similar structure and
function

  1. Connective tissue
  2. Epithelial tissue
  3. Muscle tissue
  4. Nervous tissue
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3
Q

What are various examples of connective (inert) tissue?

A
  • All joints in the body are composed of connective tissue
  • Bones
  • Bursae
  • Capsules
  • Cartilage
  • Discs
  • Menisci
  • Ligaments
  • Tendons
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4
Q

How do you go from a tissue to a full multi-cellular organism? How do the cells get together, coordinate, structure themselves to form me or you?

A

And the answer is, or at least it involves, something called the extracellular matrix.

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5
Q

What are the different non-fibrous components of the ECM?

A

Non-fibrous component
• Glycoproteins
• Proteoglycans

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6
Q

What are the functions of the ECM?• Attracting and binding water
• Supporting substance for fibrous and
cellular components
• Contributes to overall strength of
connective tissue thereby protecting it

A

• Attracting and binding water
• Supporting substance for fibrous and
cellular components
• Contributes to overall strength of
connective tissue thereby protecting it

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7
Q

What are the different fibrous components of the ECM?

A

• Fibrous Component
• Collagen – white fibrous, steel-like
strength, rigid
• Elastin – yellow fibrous, elastic properties

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8
Q

What is the difference between Collagen type 1 to collagen type 2.

A

Collagen type 1: thick fibers, little elongation
• Resists tensile forces well
• Collagen type 2: thinner, less stiff fibers
• Resists compression and shear

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9
Q

What are Resident cells?

What are circulating cells?

A

Resident Cells – Always present but depends on tissue

  • Fibroblasts (collagen)
  • Osteoblasts (bone)
  • Chondroblasts (cartilage)

Circulating Cells – If inflamed or damaged

  • Lymphocytes
  • Macrophages
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10
Q

Explain the concept of a ligament.

A

BONE TO BONE

• Cells make up 10-20%
• ECM makes up 80-90%
• Primarily composed of type I collagen fibrils that are
densely packed into fiber bundles arranged in line
with the applied tensile force
• Depending on the ligament there may be varying
directions of tensile force therefore ligaments run in
multiple directions (e.g., MCL)

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11
Q

Explain the concept of a tendon.

A

BONE TO MUSCLE

Similar make up as ligaments
• More type I collagen thought to be an adaptation
to larger tensile forces
• Primarily aligned in one direction

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12
Q

What is a fibrocartilaginous junction?

A
  • The gradual change in tendon structure, divided into four zones
  • Diffuses the load at the tissue-bone, interface, perhaps to help prevent injury
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13
Q

What is the musculotendinous junction?

A

• Muscle cells intertwine with the tendon
• Very sensitive to mechanical conditions
and becomes flatter with low load
• Weakens the junction increasing
susceptibility to injury
• Loading caution post-immobilization

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14
Q

What is hyaline cartilage?

A

• Lines articulating bones and distinguishes synovial joints
• Type II collagen throughout the ECM and compresses on the proteoglycan (PG)
molecules that hold onto water during load
• Articular cartilage has much more PG than other joint structures
• Limited blood supply, nutrient diffusion with compression

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15
Q

What is articular cartilage and the different zones?

A

• Zone 1: parallel fibers,
smooth, reduced friction,
distribute forces
• Zone 2: mesh-like to hold
water, absorbs
compression
• Zone 3: perpendicular,
securely holds the
calcified cartilage

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16
Q

What is fibrocartilage?

A

• Type I > type II collagen
• Collagen density to keep the water in the tissue (versus hyaline cartilage that
utilizes collagen and chemical water attraction)
• Limited blood supply, nutrient diffusion with compression
• E.g., meniscus
• Circumferential fibers (deep zone)
• Radial fibers (superficial zone)

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17
Q

Explain the components of the bone.

A
  • Primarily type I collagen
  • Mineral (Ca2+)
  • Two layers:
  • Cancellous (spongy)
  • Compact (cortical)

• Osteoblasts versus osteoclasts

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18
Q

What are some of the behavioural properties?

A

Structural Properties
• Load, force and elongation
• Stress and Strain
Viscoelasticity
Time/Rate-Dependent Properties
• Creep
• Stress Relaxation
• Strain Rate Sensitivity

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19
Q

Explain the slope of the different lines… What do they represent.

A

The slope of the line represents the stiffness and compliance of the tissue
• Steep curve: high stiffness, low compliance
• Gradual curve: low stiffness, high compliance

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20
Q

What are the 5 different structural properties?

A
  1. Tensile strain
  2. Bending strain
  3. Torsional loading
  4. Shear loading
  5. Compressive strain
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21
Q

What is viscoelasticity?

A

• Elasticity: returning to the original length or shape of the material after the load
has been removed
• Also known as deformation (proportional to the amount of force)
• Elastic tissue: return to resting length when force is removed
• Viscosity: the material’s resistance to flow
• Force applied to viscous material display time/rate dependent properties
• Viscous tissue: creeps under constant load (plastic does not return shape)

23
Q

What are the 3 time/rate dependant properties?

A

• Creep: continuous change in shape with prolonged force application
• Stress Relaxation: a tissue is stretched to a fixed length and held constant, the
force needed to maintain that length reduces over time
• Strain-Rate Sensitivity: more force is required to deform a tissue rapidly versus
slowly

24
Q

What are some important facts about bone?

A
  • Cortical bone withstands greater force with less deformation than cancellous bone
  • Greater compression versus tension
  • The amount of strain required to reach failure (fracture) is less in cortical bone
  • Frequent loading of low magnitude: stress fracture
  • Single load of high magnitude: complete failure (fracture)
25
Types of fractures.
26
Explain the aspects of a tendon.
Differences in stress-strain reflects varied proportion of collagen and type • Cross-sectional area, material and tendon length determine the amount of force that a tendon can resist and the amount of elongation that it can undergo • Continuous compression modifies composition to resemble cartilage (reducing tensile strength) • Tensile loads over long periods will increase tissue size, collagen concentration and cross-linking
27
Explain the contents of a ligament.
Differences in stress-strain reflects varied proportion of collagen and type • Similar mechanics to tendons • Increased thickness and strength with intermittent tensile loads • Slightly less resistant to tensile stress than tendons because they must be oriented in multiple directions (but withstand a wider variety of force directions)
28
Cartilage is to resist load:
• To resist load 1. Stress developed in the fibrillar portion of ECM 2. Swelling pressures developed in the interstitial fluid 3. Frictional drag resulting from fluid flow through the ECM • Compression reduces volume and increases pressure to push fluid out (rapid initial deformation becoming gradual and stops) • Varied orientation of fibers through zones creates non-linear behaviour
29
• Thousands of fibers grouped into: 1. 2. 3. • Myofilaments: 1. 2. 3. • Cross-bridge: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
• Thousands of fibers grouped into: • Fascicles • Myofibrils • Myofilaments • Myofilaments: actin, myosin, troponin • Cross-bridge: Action potential releases Ca2+ to expose binding sites between actin and myosin
30
Explain the cross-bridge cycle.
31
What is a sarcomere? • (I) only \_\_\_\_\_\_“\_\_\_\_\_\_\_\_\_\_\_”, (A) ______________ “\_\_\_\_\_\_\_\_\_\_\_\_”, (H) only \_\_\_\_\_\_\_\_\_\_\_\_\_
• (I) only actin “isotropic”, (A) actin and myosin “anisotropic”, (H) only myosin
32
Explain these different positions of the sarcomere. 1. Resting 2. Concentric 3. Eccentric 4. Isometric
Resting (inactive) Concentric (shortening) Eccentric (lengthening) Isometric (active)
33
ACTIVE TENSION • Developed by the active contractile elements of the muscle • Depends on more cross-bridges being formed, by: • • • •
ACTIVE TENSION • Developed by the active contractile elements of the muscle • Depends on more cross-bridges being formed, by: • Frequency of motor unit firing • Number of motor units firing • Size of motor units firing • Diameter of the axon in motor unit (conduction velocity)
34
Explain passive tension.
• Tension developed by passive, non-contractile components of muscle • Parallel elastic components • When the muscle is stretched they resist and contribute to the tension (only in tension stretch not shortening) • Epimysium • Perimysium • Endomysium • Series elastic component • Tendon (stretch exerts a pull on the tendon)
35
MUSCLE TENSION Direct relationship between \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_and \_\_\_\_\_\_\_\_\_\_\_\_ • Optimal length: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ • As a muscle is lengthened or shortened from the optimal length, the amount of tension generated is \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
MUSCLE TENSION Direct relationship between tension development and muscle length • Optimal length: capable of developing a maximal tension • As a muscle is lengthened or shortened from the optimal length, the amount of tension generated is diminished
36
What happens to the muscle tension when the muscle is being pulled apart? Explain also with a graph.
When the muscle is being pulled apart, increase stretch • Passive increases while active decreases, but the overall tension increases as the muscle gets longer
37
38
Name a few tissue modifiers.
* Age * Immobility * Disuse * Injury * Medication * Pain
39
CONTRACTILE STRUCTURES • Muscle, tendon, tendon-periosteal (TP) junction • Pain increases with ____________ movements • In the _________ direction • Pain increases with ____________ movements • In the ____________ direction • E.g., painful active and resisted elbow flexion, and passive elbow extension
CONTRACTILE STRUCTURES • Muscle, tendon, tendon-periosteal (TP) junction • Pain increases with ACTIVE AND RESISTED movements • In the SAME direction • Pain increases with PASSIVE movements • In the OPPOSITE direction • E.g., painful active and resisted elbow flexion, and passive elbow extension
40
INERT STRUCTURES • Ligaments, bursae, fascia, nerve roots, capsules, dura mater • Non-contractile • Pain is provoked by \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ • Pain increases with _____________________ movements (often end-range) • In the _____________ direction • Resisted movements are not painful
* Ligaments, bursae, fascia, nerve roots, capsules, dura mater * Non-contractile * Pain is provoked by stretching the tissue * Pain increases with ACTIVE AND PASSIVE movements (often end-range) * In the SAME direction * Resisted movements are not painful
41
What are passive movements?
* Physiological movements are used (PPM) * Need full accessory movements for PPM to occur (movements beyond control) * E.g., Bend finger – interphalangeal flexion plus slide * Apply over-pressure (OP) at the end to determine end-feel * Isometric muscle testing (strong, weak, painful, painless) – compared other side * To determine tissue type (source of pain) * Treatment guided by tissue and the specific lesion
42
What are end-feels?
• A sensation that the therapist feels in the joint and tissues at the end of available range of motion during passive movement • May be normal or pathological (abnormal) • Must compare the affected and unaffected sides
43
44
What are normal end feels?
Bone to Bone • Abrupt stop in motion; two bone surfaces coming together (e.g., elbow ext) Capsular or Soft Tissue Stretch • Hard-ish stop in motion; spring or slight give (e.g., shoulder lateral rotation) Soft Tissue Approximation • Squishy, giving • Movement stopped by limb hitting again soft tissue of another body part • e.g., knee flexion
45
What are the different abnormal end feels?
Empty – movement stopped by pain before resistance is felt (e.g., 10/10 pain) Spasm – involuntary, vibrant twang (e.g., recent #) Springy Block – unexpected rebound, non-capsular pattern restriction (e.g., tear) Abnormal Bone to Bone – early abrupt stop, crepitus or grating (e.g., post immobilization) Abnormal Capsular – early hard-ish stop before end range (e.g., frozen shoulder)
46
What is a capsular pattern of restriction?
A characteristic pattern of expected proportional limitation of movement, specific to a particular joint • Exists only in those joints controlled by muscle, which have a joint capsule and are lined by a synovial membrane • Suggests that the entire capsule and/or synovial membrane of the joint is involved • Total joint reaction (e.g., post-immobilization) • Determined by passive movements
47
Define a closed packed position (CPP) for articular joint positions.
Most stable position • Greatest protection for the joint • Usually avoided during assessment • Greatest congruency of surfaces • Capsule, ligaments under max tension • If swollen, CPP cannot be reached
48
49
Define a loose packed position (LPP) for articular joint positions.
* Any position other than CPP * Not congruent * Capsule and ligaments are relaxed * Greatest room for swelling * Naturally adopted for rest when painful * Least amount of stress on structures
50
What is the resting position?
* A specific loose packed position * Minimal congruency between surfaces * Capsule and ligament have greatest laxity * Passive separation of joint surfaces, therefore greatest swelling * Usually the mid-position for the joint
51
What is the constant length phenomenon?
Limitation of movement at one joint is dependent on the position at which another joint is held • Restricting tissue is outside the joint • Suggests a lesion in a tissue that spans two joints E.g., lumbar disc lesion, irritates the sciatic nerve à positive SLR E.g., muscle adhesion in the two joint muscle

Musculokeletal Phyt I (5 decks)

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