Microstructure and Ultrastructure Flashcards
1
Q
List 6 properties of tendons
A
- Dense regular connective tissue
- Composed of <80% collagen (chiefly type 1) and 1-2% elastin
- Vary in size based on function
- Responsible for transmission of muscle force to bone
- Organised in bundles
- Strain resistant with up to 1260kg/cm2 tensile strength
2
Q
List 4 properties of ligaments
A
- Similar to tendons in origin and internal structure
- Responsible for connecting bone to bone at joints
- Highly reliant on crimping regions to utilise their elasticity
- Crimping regions are also present in tendons but play a less prominent role
(Frank, 2004)
3
Q
Describe the ascending organisation of tendons and ligaments
A
- Fibrils
- Fibres
- Primary bundles
- Secondary bundles
- Tertiary bundles
- Tendon / ligament
4
Q
Describe fibrils
A
Composed of elongated fibroblast cells which run longitudinally, transversely and horizontally.
Bundles which run longitudinally do not always run parallel with each other; they often cross other bundles.
This structure acts as a buffer against forces acting on the tissues from all directions.
5
Q
Describe the composition of a tendon exposed to higher strains
A
- Thicker
- Shorter
- Bigger, denser packed bundles
6
Q
Describe the composition of a tendon exposed to lower strains
A
- Long
- Thin
- For more precise movements
7
Q
What are groups of fascicles of a tendon bound by?
A
Epitenon (Kannus, 2000)
8
Q
What is the supporting covering sheath of a ligament called?
A
Epiligament (Kannus, 2000)
9
Q
Compare and contrast tendons and ligaments
A
10
Q
Tendons and ligaments are viscoelastic structures.
What does this mean?
A
When a force is applied, the tendon or ligament will stretch to allow movement, but will always return to its original structure.
11
Q
Why are tendons strong?
Why are tendons flexible?
A
- Strong to withstand the forces applied during muscle contraction.
- Flexible to allow movement around bone and to move under retinacula (example - long flexor tendons of the hand).
12
Q
Why are ligaments strong?
Why are ligaments flexible?
A
- Strong to offer resistance and hold the joint together during movement.
- Flexible to allow free and natural movement of the joint (example - medial and lateral collateral ligaments of the knee joint).
13
Q
What is stress?
A
A measure of force per unit area
14
Q
What is strain?
A
The response of a system when stress is applied
15
Q
How do you calculate strain?
A
Ratio: change in length over initial length
16
Q
Describe normal stress
A
- It is assumed that the intensity of distributed forces are uniform
- Changes dimensions but not the shape of the object under stress
- Compressive stresses or tensile stresses
- δ = F/A
F = force
A = area
17
Q
Describe shear stress
A
- Equal and opposite forces applied to opposite faces of an object
- Changes the shape of the object under stress but does not change the dimensions
- τ= F/A
18
Q
Describe normal strain
A
- Ratio of the amount of elongation to the original length
- ϵ= Δ1/1
- If the material increases in length then strain is tensile and positive
- If the material decreases in length then strain is compressive and negative
19
Q
Describe shear strain
A
- Related to distortions from shear stress
- Shear strain is the ratio of horizontal displacement (d) to height (h)
- Ɣ= d/h
20
Q
Draw the stress vs strain curve
A
- O - origin
- P - proportionality limit
- E - elastic limit
- Y - yield point
- U - highest stress point
- R - rupture point
- 𝛔y - yield strength of material
- 𝛔u - ultimate strength of material
21
Q
Describe the load and elongation curve
A
- Used to analyse biomechanical properties of tendons and ligaments
- Tissue has a tensile force applied to cause a constant rate of elongation
- This force is applied until the tissue ruptures
- There are 4 main points on the graph:
- Toe region (primary region)
- Linear region (secondary region)
- End of secondary region
- Maximum load
22
Q
What limits range of motion of the vertebral column?
A
- Resistance of the ligaments
23
Q
How does movement of the vertebral column occur?
A
As a whole - NOT between individual segments, except between C1 and C2.
24
Q
Describe the structure and function of the nuchal ligament
A
Elasticity allows flexion and extension of the vertebral column without buckling of the ligament
25
Descrbie the structure of the anterior longitudinal ligament
* Extends along anterolateral aspects of vertebral bodies and IV discs from pelvic surface of sacrum to anterior tubercle of C1 and occipital bone.
* Strong, thick band of collagen fibres arranged in 3 distinct layers: superficial, intermediate and deep.
* Superior part blends with the anterior atlantoaxial and atlanto-occipital ligaments.
* 1.3-2.5mm thickness range
* Well arranged bundles of collagen fibres - very stiff due to high percentage of collagen fibres.
26
Describe the functions of the anterior longitudinal ligament
* Maintains stability of the vertebral column between the individual joints of the vertebrae.
* Restricts movement of each vertebral segment limiting extension (only ligament which limits extension).
* Strongest and largest vertebral ligament.
27
Describe the structure of the posterior longitudinal ligament
* Lies within the vertebral canal along the posterior aspect of the vertebral bodies.
* Narrower than the ALL
* Uniform and broad in the cervical and upper thoracic regions - 10-15mm width
* Saw-toothed appearance in the lower thoracic and lumbar regions.
* Narrows over lower thoracic and lumbar vertebral bodies extending over vertebral discs.
* Collagen fibres are more compact than in the ALL
* 2x weaker than than the ALL
* In the thoracic region, ligament can withstand forces of up to 70N, but in the cervical and lumbar regions can only withstand up to 50N.
28
Describe the functions of the posterior longitudinal ligament
* Limits hyperflexion by preventing separation of the posterior ends of the vertebral bodies.
* Prevents posterior herniation of the nucleus pulposus.
29
Describe the ligamenta flava
* Series of ligaments that connect adjacent laminae.
* Thin and broad superiorly thickening towards the lumbar vertebrae.
* Yellow appearance due to higher percentage of elastin than other vertebral ligaments.
30
Describe the functions of the ligamenta flava
* Counteracts vertebral lamina separation during flexion.
* Helps return vertebral column to an upright position after flexion.
* Elastic component of the ligament prevents buckling.
31
Describe the supraspinous ligaments
* Cord-like structure connecting tips of adjacent spinous processes.
* Run from the tips of spinous processes from C7 to the sacrum.
* Superiorly the ligaments merge with the nuchal ligament.
* Ligaments broaden towards the lumbar region.
32
Describe the functions of the supraspinous ligaments
* Limits flexion.
* Offers limited resistance to separation of vertebral spinous processes.
* Holds maximum load during torsion.
33
Describe the interspinous ligaments
* Thin, membraneous ligaments connecting adjacent spinous processes.
* Ligament is poorly developed in the neck and thickens as it descends through thoracic and lumbar vertebra.
* Anteriorly, merges with supraspinous ligaments.
34
Describe the function of the interspinous ligaments
* Works with ligamentum flavum and supraspinous ligaments.
* Provides vertebral stability.
* Offers limited resistance to flexion.
* Counteracts separation of vertebral spinous processes.
35
Describe the intertransverse ligaments
* Ligament extends from superior border of one transverse process to inferior border of the adjacent transverse process.
* Ligaments are fibrous cords between thoracic vertebrae and become thinner and more membraneous between lumbar vertebrae.
36
Descrbe the function of the intertransverse ligaments
* Limits flexion
* Carries maximum load during lateral flexion of vertebral column
37
Describe the nuchal ligament
* Thickened fibroelastic tissue.
* External occipital protuberance and posterior border of the foramen magnum to spinous processes of cervical vertebrae.
* Very high in elastin (~80%).
* Forms a midline septation dividing the posterior neck muscles.
* It is an extension of the supraspinous ligament.
38
Describe the function of the nuchal ligament
* Supports the head
* Resists hyperflexion of the cervical spine
* Helps return head to the anatomical position
* Helps maintain cervical spine alignments
* Muscle attachment site due to broad lateral surfaces
* In other quadrupeds the nuchal ligament is thicker to hold head up while walking on all fours
39
Describe the transverse ligament of the atlas
* Composed of neatly arranged collagen fibres.
* Extends between the tubercles of medial aspect of the lateral masses of C1.
* Runs transversely across the anterior arch of the atlas and divides the ring into an anterior and posterior compartment.
* Can withstand a force of 350N before rupturing - largest, thickest and strongest craniocervical ligament.
* Has a smooth fibrocartilaginous surface, allowing the odontoid proess to glide smoothly against it.
40
Describe the function of the transverse ligament of the atlas
* Craniocervical joint stability
* Aids stabilisation of the atlantoaxial joint
* Permits rotation of the atlantoaxial joint
* Limits flexion at the atlantoaxial and atlantooccipital joints
* Prevents anterior displacement of the axis by pushing the ventral surface of the dens against the atlas.
41
Describe the alar ligament
* Used to attach the axis to the base of the skull
* Lateral aspects attach to the odontoid process
* Some believe that the superior attachment of the ligament is to the anterolateral aspect of the foramen magnum.
* Others believe that the attachment is to the medial aspect of the occipital condyles on either side.
* Mean length - 8.8mm
* Mean diameter - 7.3mm
* Can withstand 200N of force before rupturing
42
Describe the function of the alar ligament
* Atlantoaxial joint stabiliser
* Craniocervical junction stabiliser along with transverse ligament
* Prevents excessive rotation at the atlantoaxial and atlantooccipital joint.
* Limits lateral bending to the contralateral side.
* Prevents displacement of the atlas anteriorly.
43
Which injury would cause rupture of the transverse ligament of the atlas?
Falls or accidents with a direct blow to the head causing forced hyperflexion.
44
Which injury would cause the alar ligament to rupture?
Injuries commonly cause by road traffic collisions causeing hyperextension or rotation of the neck
45
Why are the craniocervical ligaments more susceptible to high energy injuries?
Due to theie high percentage collagen composition.
46
Why are the craniocervical ligaments unable to stretch under tension?
Due to their low percentage elastin composition
47
Which injuries commonly cause rupture of the craniocervical ligaments?
Whiplash injuries
48
Why are tears of the transverse ligament of the atlas rare in children?
They have a weaker synchondrosis of the dens compared to the ligaments
49
Ossification of ligaments of the vertebral column
* Characterised by ectopic bone growth
* Genetic predisposition
* Biomechanical stress
* Ossification of posterior longitudinal ligament due to atlanto-axial fusion.
* Ossification of ligamentum flavum due to range of rotation along the vertebra.
50
What can result from ossification of vertebral column ligaments?
* Compression on the spinal cord
* This can cause significant neurological disorders
* Symptoms include serious neck pain and dysfunction of the upper and lower extremities - more commonly appears in females for unknown reason.
51
Where is ossification of the posterior longitudinal ligament most common?
1. Cervical region
2. Thoracic region
3. Lumbar region
52
Why is risk of ossification of the posterior longitudinal ligament higher after lower lumbar spine surgery?
Because this surgery can disturb the posterior surface causing instability and increasing stress on the ligament.
53
Where is ossification of the ligamentum flavum most common?
1. Thoracic region
2. Cervical region
3. Lumbar region
This injury is relatively common in the Asian population.
54
In which spinal region is it supposed that ossification of the ligaments causes the most severe problems?
In the thoracic and lumbar regions, ossification is said to cause the most serious issues because patients are often left unable to walk.
