4- Ligaments Flashcards Preview

Musculoskeletal System II > 4- Ligaments > Flashcards

Flashcards in 4- Ligaments Deck (41)
Loading flashcards...
1
Q

What is “anisotrophic”?

A

having unlike mechanical properties in different dictions; that is, the mechanical properties depend on the orientation of the applied force

2
Q

How do ligaments work in pairs?

A

work in pairs to stabilize the joint, a ligament on the lateral side is stabilized by a ligament on the medial side (ex in book was lateral talofibular ligament is balanced by deltoid ligament on medial side of the ankle)

3
Q

What is the relationship between load and elongation on a curve?

A

a) Ligaments have built in laxity to allow small deformation in joints, but when stretched become stiff to stabilize joints.
b) At low loads the ligament is lax and not stiff, as load increases so does elongation and with it stiffness. Once load is too large the ligament will tear

4
Q

How can a joint be stabilized if a ligament is torn?

A

ligament is torn, a pt may use muscles to actively stabilize the joint (ex if ankle ligament is torn they can use the fibularis longus and brevis)

5
Q

What is the histological organization of ligaments?

A

display band-like connective tissue, they are intricate amalgams (combining or uniting multiple entities into one form) of extraceulluar matrix proteins

6
Q

What are fascicles?

A

densely organized fiber bundles in muscle and ligament. Ligaments are composed of longitudinally oriented fascicles, that take the form of organized sinusoidal waveform when viewed from longitudinal axis called the crimp.

7
Q

What is a crimp?

A

the crimp is when the fibers bunch into a wavy pattern (think of a hair crimper) under no stretch, this allows room for stretching when the ligament is stretched

They are also in a gang rivalry with the bloods.

8
Q

What are the 3 basic types of cells in a ligament?

A

a) Fusiform: spindle-shaped, related to crimped collagen fibers
b) Ovoid: found in columns, w/ amorphous ECM in periceullular space
c) Spheroid: found in columns, w/ amorphous ECM in periceullular space

9
Q

How does a ligament get its blood supply?

A

a) The supply originates in the blood vessels near the joint surfaces
b) The cells of ligaments depend on diffusion of nutrients from vascularized tissues

10
Q

What is an engoligament?

A

the vascularized layer of loose connective tissue that surrounds bundles of individual collagen fibrils w/in a ligament

11
Q

What is the epiligament?

A

the vascularized layer that covers the surface of the entire ligament

12
Q

Where are the nerve fibers located that supply a ligament?

A

located near the vessels, predominantly in the epiligament

13
Q

What are the types of receptors that supply the nerve?

A

Ruffini receptors, Pacinian Receptors, Golgi Receptors, Free Unmyelinated nerve endings.

14
Q

What is the role of the mechanoreceptors in the ligament?

A

play a role in proprioception by helping to provide the sense of where the body is in space.

15
Q

What would happen if the mechanoreceptors in the ligament are injured?

A

if an ankle ligament is damaged and healed, but the mechanoreceptor nerve pathway has not been reestablished, a pt may have a poor sense of where the foot is relative to the ground if not staring at the foot, they “do not trust the ankle”. This leads to clumsiness. Nerve pathway may return faster with PT.

16
Q

What are the 4 zones of the direct attachment of a ligament to a bone?

A

(1) Ligament
(2) Nonmineralized fibrocartilage
(3) Mineralized fibrocartilage
(4) Bone

17
Q

What is the indirect attachment of a ligament to bone?

A

fibers pass directly into bone w/o intervening layer of fibrocartilage. The fibers of the ligament blend with the periosteal layer.

18
Q

What is the molecular stucture of collagen?

A

a macromolecular triple helix composed of 3 AA alpha chains, which are composed of repeating triplets of polypeptides. Usually the chain starts with glycine then proline. The proline causes the alpha chains to wind into a left-handed triple helix. The 3 alpha chains then wind together into a right-handed triple helix. It is the helix’s spiral shape that gives collagen the ability to resist tensile forces.

19
Q

What type of collagen makes up 90% of a ligament’s collagen?

A

Type I

20
Q

What type of collagen makes up the remaining 10% of a ligaments collagen?

A

Type III

21
Q

How is collagen produced?

A

type I collagen is produced intracellularly and modified extracellularly by cleavage which then aggregate into microfibrils which takes on a staggered pattern. The staggered pattern allows oppositely charged AA to align and bond giving the fibril extra tensile strength.

22
Q

What is the size of a collagen molecule?

A

300nm

23
Q

What are the 2 other components of ligaments besides collagen?

A

a) Proteoglycans: such as chondroitin 4-sulfate and dermatan sulfate
b) Glycoproteins: such as elastin and fibronectin

24
Q

What is a sprain?

A

damage to ligament, and are graded to amount of gross displace of the joint. This is caused by anything that causes a large amount of tension in ligament

25
Q

What is a grade 1 sprain?

A

pain but no joint instability, intrafibrous injury to ligament

26
Q

What is a grade 2 sprain?

A

some but not all fibers are torn, minimal joint instability

27
Q

What is a grade 3 sprain?

A

you’re screwed, complete tear of ligament and great instability

28
Q

What occurs during the 7-10 days of the inflammatory stage of ligament healing?

A

(1) Begins w/in hours and extends through 7 to 10 days. It is characterized by presence of necrosis, inflammatory cells, and growth of neovascular tissue on surface of ligament remnant.
(2) Hematoma forms from capillary damage, signaling continuation of migration of inflammatory cells
(3) Do not want to impede inflammation, so no anti-inflammatories

29
Q

What occurs during the 10-21 days of the proliferation stage of ligament healing?

A

(1) Characterized by an increase in cell density in the ligament remnants with ovoid cells and gradual neovascularization of the entire ligament remnant.
(2) New collagen forms and so does a scar
(3) Cells migrate from torn ligament ends into granulation tissue. So the space between torn ends is filled with matrix of disorganized proteins and many cells

30
Q

What occurs during the 21 days-years of the remodeling stage of ligament healing?

A

(1) This phase starts when fibroblast response slows down and matrix alignment starts to happen, collagen condenses w/in scar.
(2) Over time the collagen becomes more aligned, it is similar to original but not perfect

31
Q

How long do you need to complete ligament healing?

A

minimum of 1 year but may extend to several

32
Q

Do ACL tears heal?

A

no

33
Q

What is the Tx for ACL tears?

A

Tx is ligament reconstruction, which is removal of torn ligament and replacement with a tendon graft. The graft is never as good b/c of the complex geometry of the native ACL, also proprioception is usually lost with an ACL tear.

34
Q

Why can immobilization during healing of a joint lead to stiffness?

A

can cause stiffness b/c, w/o appropriate signals from normal mechanical stress, the healing tissue fails to orient itself in the correct direction. The tissue takes on a haphazard orientation causing adhesions.

35
Q

What does immobilization of intact ligaments do?

A

can weaken them and their attachments to bone

36
Q

What is characteristic of Ehlers-Danlos syndrome?

A

characterized by weakness/laxity in ligaments, skin and blood vessels.

37
Q

What is the etiology of Ehlers-Danlos?

A

mutation in fibrillar collagen genes, and genes that modify fibrillar collagen

38
Q

What is Ehlers-Danlos Syndrome Type I?

A

an autosomal dom disorder caused by mutation in the gene that codes for collagen type V which is required for forming collagen type I fibrils, this leads to decreased ligament stiffness and joint laxity

39
Q

What is the etiology of Marfan’s syndrome?

A

an autosomal dom disorder caused by mutation in fibrillin gene.

40
Q

What is the role of fibrillin?

A

a glycoprotein and is a component in elastin-containing microfibrils.
i) So if you have a mutated fibrillin gene and decreased fibrillin, you have structurally weak elastin (which is important to structure of ligaments)

41
Q

What are the clinical manifestations of Marfan’s syndrome?

A

ligament laxity, loose joints, aortic dilation, and other connective tissue problems.