TENDONS

Question 1

what are the types of connective tissue

Answer 1

1. muscle
   2.bone
2. tendons - muscle to bone
3. cartilage
4. ligaments -connect bone to cone

Question 2

what are the 2 types of musculoskeletal injuries(bone, muscle, tendons and ligaments)

Answer 2

1. acute onset injuries- from a single overuse event
2. chronic overuse injuries - repetitive overuse

Question 3

what is the point of union between muscle and tendon

Answer 3

the myotendinous junction

Question 4

what is the point of union between muscle and bone

Answer 4

the osteotendinous junction

Question 5

what are the 2 properties of tendons

Answer 5

they are viscous and elastic

Question 6

what are features of the viscoelastic tendon material

Answer 6

1. hysteresis
2. rate dependence
3. creep
4. load relaxation

Question 7

what is hysteresis

Answer 7

this is when the loading an unloading of a tendon leads to energy loss as heat

Question 8

what is rate dependence

Answer 8

this is when the faster we load a tendon leads to greater stress and strain compared to when it is loaded slower

Question 9

what is load relaxation

Answer 9

this is when a constant load is applied to tendons kept at constant length we see a decrease in the force in the tendons

Question 10

what is creep

Answer 10

when a constant load is applied to tendons we see their length deform over time

Question 11

explain the stages of the tendon stress(load) strain(elongation) curve

Answer 11

1.the first step is the toe phase where we see uncrimpling of the collagen fibres
2. linear phase where we see the collagen backbone straightening aswell
3. failure where we see the fibres sliding past one another and crosslinks breaking and so the the tendons fail
=rupture if not healed properly

Question 12

what is the structure of a tendon

Answer 12

1. collagen molecule(proteins ie type 1)
2. fibril-protein collagen molecules come together
3. fibre-fibrils come together
4. fascicle -fibers come together
   5.tendon-fascicles come together

Question 13

what is the smallest structural unit of collagen

Answer 13

the collagen fibril

Question 14

what are the collagen proteins made of

Answer 14

alpha chain triple helices
-these are when 3 alpha chains come together to form a helix
-each alpha chain is made up of triplet repeats of GLY-X-Y
-X is usually lysine or proline
-Y is usually hydroxylysine or hydroxyproline
-the triple helices are glycosylated

Question 15

what are the types of fibrillar collagens

Answer 15

1. type 1 collagen - 2a 1 and 1a2 chains
   -most abundant type
   -heterotrimer
   -confers rigidity
2. type 11 collagen- 3a1 chains
   -homotrimer
   -most common in cartilage
   3.type 111 collagen
   - 3a1 chains
   -often found with type 1
   -confers elasticity

Question 16

what are the collagen types found in bone, tendons, muscle and ligaments

Answer 16

major: type 1 and 3
minor: type v

Question 17

what are the collagen types found in cartilage

Answer 17

major: type 2
minor: type XI

Question 18

how does a type 1 collagen molecule form

Answer 18

1. 3 alpha helices come together
2. to form a procollagen
3. then procollagen peptidase will cleave off the loose ends to form collagen

Question 19

how do we go from a collagen molecule to a collagen fibril

Answer 19

the collagen molecules will align in parallel and form crosslinks for tensile strength to form a fibril
-the crosslinks form between lysine residues and hydroxylysine

Question 20

what are FACITS

Answer 20

non fibrillar collagen with interrupted triple helices
-these support the fibrillar collagens
-the FACIT types in bone, ligaments, tendons and muscle is types XIV and XII
-the main FACIT type is IX in cartilage

Question 21

what is the function of FACITs

Answer 21

they mediate the connection between collagen fibres and cell surfaces and they stabilise the fibrillar collagens

Question 22

what are the components of tendons

Answer 22

1. proteins
   2.ground substance
2. cells

Question 23

what are the proteins found in tendons

Answer 23

1. fibrillar proteins- elastin and collagen(60-80%)
   2.non fibrillar proteins -glycoproteins

Question 24

what is in the ground substance found in tendons

Answer 24

1. water
2. glycosaminoglycans
   3.proteoglycans

Question 25

what cells are found in the tendons

Answer 25

1. tenoblasts 2.tenocytes( tendon fibroblast) 3. fibroblasts

Question 26

what are glycoproteins

Answer 26

they are the non fibrillar proteins in tendons and they function in providing adhesion of cells to cells and cells to the ECM

Question 27

what does the ground substance contribute to in tendons

Answer 27

1. lubricance 2. adhesion 3. protective barrier 4. strength and elasticity

Question 28

what do proteoglycans do

Answer 28

they have a core protein with GAGs protruding off -they secrete the gel like medium of the ECM in which the fibres are embedded

Question 29

what do glycosaminoglycans do

Answer 29

they also secrete the gel like substance of the ECM that embeds the fibers -they are made of repeating disaccharides(sugars) that have negatively charged sulphate groups making GAGs negatively charged thus; can bind to water to give it its gel like properties

Question 30

what are large hyalectan proteoglycans

Answer 30

1. versican 2. aggrecan - they help with load bearing properties

Question 31

what is the function of the fibroblasts and tenocytes in the tendons

Answer 31

they produce all the components of the ECM ie; the collagen fibrils; the ground substance components etc..

Question 32

explain the steps of how collagen is formed from a tenocyte

Answer 32

1. alpha chain mRNA 2.this translates into alpha chain protein 3. then the alpha chain lysine and proline residues are hydroxylated 4. the chain is glycosylated 5. then the helix forms 6. the helix is then secreted into the ECM 7. then the procollagen is cleaved by procollagen peptidase to generate collagen 8. the collagen molecules then come together in parallel forming cross links to form a fibril

Question 33

how do tenocytes respond to force placed on a tendon

Answer 33

the force/mechanical trigger stimulates the integrin receptor on the membrane -this activates the cell -cell to cell contact -produce and release new proteins into the ECM - this can be a healing process or an adaptation

Question 34

achilles tendon injuries risk factors

Answer 34

1. INTRINSIC RISK FACTORS -previous injury -flexibility -weight 2.EXTRINSIC FACTORS - shoes -training method -occupation -physical activity

Question 35

what is the iceberg theory used to explain

Answer 35

tendinopathy pathogenesis

Question 36

explain the first step of the iceberg theory: healthy load

Answer 36

when a healthy load is placed on a tendon it is not harmful but instead re-inforces the tendon by stimulating the production of new collagen fibers. the tendon increases in elastic stiffness and tensile strength as it becomes larger, stronger and more resistant to injury

Question 37

explain the second step of the iceberg theory:overload

Answer 37

this is when the tendon is overloaded or overused then the collagen fibres are going to begin sliding past one another; causing the crosslinks to break and thus; failure of the tendon. this microtrauma also impacts the rest of the ECM

Question 38

what would be the tip of the iceberg in the iceberg theory

Answer 38

pain

Question 39

explain the third step of the iceberg theory: healing

Answer 39

the optimal conditions for good healing is optimal recovery time and rest without more overloading. if this is not met could lead to rupture -remember every person has different intrinsic and extrinsic factors so they will respond differently to healing and overloading so it needs to be specific for each individual