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Phase 1 Medicine - Riona > Musculoskeletal physiology > Flashcards

Musculoskeletal physiology Flashcards

(109 cards)

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1
Q

What are the functions of bones? (7)

A
  • Hold up against gravity
  • Transmits body weight
  • Protects internal organs
  • Determines basic body shape
  • Haematopoiesis (formation of blood cellular contents)
  • Mineral recevoir for calcium & phosphate & lipid storage
  • Acid-base balance
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2
Q

What are the two types of bone?

A

Primary/woven

Secondary/lamellar

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3
Q

What are the two subtypes of secondary bone?

A

Compact

Spongy/cancellous - trabeculae

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4
Q

What are the reasons for bone remodelling? (6)

A
  • Form bone shape
  • Replace woven bone with lamellar
  • Reorientate fibres & trabeculae in favourable direction for mechanical strength
  • Response to loading
  • Repair damage
  • Obtain calcium
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5
Q

What are the 5 types of bone according to shape, and an example of each?

A 
Long - femur
Short - carpals
Flat - skull
Irregular - vertebra 
Sesamoid - patella
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6
Q

What are the differences between the axial skeleton & the appendicular skeleton?

A 
Axial = skull, spinal column, ribs, bones of trunk
Appendicular = limbs, inc scapulae & pelvis
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7
Q

What is the epiphysis?

A

Head of a long bone

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8
Q

What is the diaphysis?

A

Shaft of a long bone

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9
Q

What are the 2 substances make up the composition of bone?

A

Mineral

Matrix

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10
Q

What is the mineral part of bone made from?

A

Hydroxyapatite, crystalline form of calcium phosphate

Adds stiffness & rigidity

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11
Q

What is the matrix part of bone made from?

A

Type I collagen
Provides elasticity
Osteoid

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12
Q

Define ossification

A

The process by which embryonic connective tissue is replaced by bone

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13
Q

How does endochondrial ossification begin?

A
  • hyaline cartilage proformer for bone formation
  • vascularisation of perichondrium (outermost layer of cartilage)
  • mesenchymal stem cells in primary ossification centre gain blood supply
  • stimulated to develop into osteoblasts
  • produced & secrete osteoid
  • congregate at wall of diaphysis, forming bone collar
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14
Q

What stimulates the mineralisation of the osteoid?

A

Chondrocytes in hyaline cartilage send out signals

Forms primary bone as a collar

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15
Q

What results in formation of a cavity in the centre of the cartilage?

A

Mineralisation of bone means nutrients cannot be delivered to chondrocytes beneath it so cell death occurs

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16
Q

What results in the formation of spongy bone inside the cavity?

A

Periosteal bud invasion
Blood vessels & lymphatics to cavity
Also has osteogenic cells (osteoclasts & osteoblasts)

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17
Q

Where do the osteoblasts & osteoclasts work?

A

Osteoblasts in middle/behind osteoclasts to lay down spongy bone
Osteoclasts work at ends of cavity to degrade cartilage

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18
Q

What does the cavity in the centre become?

A

Medullary cavity

Where yellow bone marrow is stored

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19
Q

Where does the degradation of cartilage in the centre of the epiphyses occur?

A

Secondary ossification centre

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20
Q

What causes elongation of bone?

A

Chondroblasts that form hyaline cartilage still working at ends

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21
Q

What do osteoclasts leave at the edges of epiphyses?

A

Articular cartilage

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22
Q

How does intramembranous ossification occur?

A

Mesenchymal stem cells in the middle of connective tissue membranes differentiate into osteoblasts
Produce osteoid that gets mineralised
Flat bones of skill, clavicle, shafts of ribs

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23
Q

What does exercise do to bone formation?

A

Increased strain; increased bone formation

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24
Q

What 3 places does extracellular calcium come from?

A

Absorbed in gut
Reabsorbed from tubule fluid in kidneys
Reabsorbed in bone

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25
What is most of EC calcium in the form of?
Free ionised Ca2+ ions
26
Where is calcium absorbed?
Actively - duodenum & jejumum | Passively - ileum & colon
27
What causes an increase in the amount of calcium?
Calcitriol | 1,25-dihydroxyvitamin D
28
What are the 2 ways calcium can be released from bone?
Rapidly - exchangeable calcium at surface of bone | Slowly - osteoclasts on bone surface (secrete acid onto bone)
29
What type of calcium is not filterable?
Protein-bound
30
Where does the majority of calcium reabsorption take place?
PCT Thick ascending tubule Some in DCT, under hormonal control
31
Which cells in the parathyroid glands detect calcium & secrete PTH?
Chief cells
32
What type of hormone is PTH & hence where are its receptors?
Peptide hormone | On plasma membranes
33
What does PTH use as a secondary messenger?
cAMP
34
What does PTH do in the kidneys? (3)
* Increase production of 1,25-dihydroxyvitamin D - by stimulating activity of 1a-hydroxylane enzyme that produces this from 25-hydroxyvitamin D * Increases reabsorption of calcium from tubule fluid in DT * Decreases amount of phosphate being reabsorbed
35
What does 1,25-dihydroxyvitamin D do?
Increases absorption of calcium from gut
36
What does PTH do to bones? (2)
* Stimulates immediate release of calcium from exchangeable calcium on surface of bone * Stimulates increase in amount of bone remodelling (osteoclast activity increases to release calcium)
37
What is calcitonin?
Peptide hormone | Antagonist to PTH
38
What are the 3 main effects of calcitonin?
* Inhibits osteoclast activity * Stimulates osteoblast activity * Inhibits DCT reabsorption of calcium
39
How is vitamin D produced?
* UVB radiation hits skin * stimulates conversion of 7-dehydrocholestrol into cholecalciferol * transported to liver * acted upon by 25-hydroxylase enzyme to convert it into 25-hydroxyvitamin D (pro hormone) * transported to kidneys * acted upon by 1-alpha hydroxylase enzyme into 1,25-dihydroxyvitamin D (active)
40
What do osteoclasts originate from?
Haemopoietic stem cells
41
What are Howship's lacunae?
Small cavities on the surface of bones where osteoclasts are found
42
What is the sealing zone?
The area where a osteoclast attaches onto the bone
43
How do the osteoclasts absorb bone?
Secrete H+ ions through action of carbonic anhydrase enzymes in cell Secrete collagenases Secretions break down bone matrix
44
What is the role os osteoblasts?
To secrete ostoid
45
What do osteoblasts originate from?
Mesenchymal stem cells via osteoprogenitors
46
What is the different in nuclei between osteoclasts & osteoblasts?
Clasts - large multinucleate | Blasts - uninucleate
47
How are osteocytes formed?
Osteoblasts trapped in bone matrix in concentric rings in osteons when lamellar (secondary) bone is formed
48
How do osteocytes receive nourishment?
Through small canaliculi that extend from the central canal (Haversian canal) in the centre of the osteon Slow delivery - limits growth
49
What is RANK-ligand?
A protein found on osteoblast cell surface membranes that is able to bind to the RANK receptors on the cell surface membrane of the osteoclast precursors
50
What does the binding of RANK-ligand do?
Stimulates osteoclast precursors' differentiation to osteoclasts
51
Where are RANK-ligands also found?
On the cell surface membrane of osteoclasts themselves
52
What is another protein that is similar in structure to RANK-ligand?
Osteoprotegrin (OPG)
53
What does the binding of OPG cause?
Can bind to RANK receptors Inhibits RANK-RANK-l pathway as it does not cause differentiation Reduces osteoclastic activity
54
Define fracture
Breach in the continuity of bone
55
What are the two ways in which a fracture can occur?
Non-physiological load applied to normal bone | Physiological load applied to abnormal bone (fragility fracture)
56
How is a fracture described? (5)
``` Site Pattern Displacement/angulation Joint Skin ```
57
What is an intra-articular fracture?
A joint is involved
58
What are the 4 stages of fracture healing?
Haematoma Inflammation Repair Remodelling
59
What occurs during the haematoma stage of healing?
Within hours Bleeding from endosteal & periosteal blood vessels Blood accumulates around fracture site Death of cells
60
What occurs during the inflammation stage of healing?
Few days Formation of fibrin clots & neovascularisation (new blood vessels) Cleaning up of any fragmented/dead tissue by haematopoietic cells (repair cytokines & osteoclasts)
61
What occurs during the repair stage of healing?
``` Weeks Formation of a callus Fibroblasts form fibrous tissue that acts as basis for chondroblasts, which then produce & lay down cartilage Osteoblasts secrete osteoid Mineralised into primary bone ```
62
What occurs during the remodelling stage of healing?
Months/years Woven into secondary Vascularisation back to normal No scarring (unique to bone tissue)
63
Define a ligament
Fibrous connective tissues that connect bones to other bones
64
Define a tendon
Fibrous connective tissues that connect muscles to bones
65
What are 2 of the roles of a ligament?
Confer mechanical stability to skeleton | Help guide motion of a joint, preventing excessive motion
66
What are 3 of the roles of a tendon?
Provide solid base onto which muscle can insert Help transmit tensile weight that the muscle is experiencing to the skeleton Aids in stability of joint
67
What are 4 differences between ligaments & tendons?
* ligaments have less collagen * ligaments have more elastin * ligament fibres are more randomly organised * ligaments receive their blood supply through their insertion sites; tendons can be vascular or avascular
68
What are ligaments & tendons made up of?
* Dense connective tissues that consist of mainly parallel fibres (gives high tensile strength) * Have tenocytes
69
What are tenocytes?
Fibroblasts that synthesise & remodel the extracellular matrix
70
Why do ligaments & tendons have a poor capacity for healing?
Poorly vascularised
71
What is the hierarchal structure of ligaments & tendons?
* 3 procollagen helices bound together to form a tropocollagen * multiple tropocollagen bound together to form a microfibril * microfilbrils form sub fibrils * subfibrils form fibrils * fibrils bind together by endotenon to form fascicles * fasciles bound by peritenon to form tendon/ligament * then surrounded by epithenon
72
What helps to regulate the diameter of a collagen fibre during fibrillogenesis?
Proteoglycans
73
What do proteoglycans also do?
Keeps fibrils together | Act as lubricant to help the fibres move over one antoher
74
Where is collagen initially synthesised?
Fibroblasts
75
What do fibroblasts produce in collagen synthesis?
Procollagen molecules | Single stranded polypeptide chains, left-handed helix (alpha chains)
76
What do alpha chains in collagen synthesis come together to form?
3 come together to form a right-handed helix | Cross linking occurs between these chains, enhancing strength
77
How is the triple helix of collagen synthesis made into microfibrils?
Transported out of cell via secretion vacuoles Terminal peptides removed to for tropocollagen Enzyme lysol oxidase forms cross-links to form microfibrils
78
What are entheses?
Connective tissue between tendon/ligament & bone
79
What are the 2 types of entheses?
Fibrous | Fibrocartilagenous
80
What are entheses innervated by?
Proprioceptive receptors & nociceptor endings
81
How are the fibrous entheses formed?
Through intramembranous ossification | Calcified part formed by Sharpey's fibres (calcified collagen fibres) & attach directly onto bone
82
How are the fibrocartilagenous entheses formed?
Through endochondral ossification | Gradual change from collagenous ligament to fibrocartilage then into mineralised cartilage on bone
83
What does the load-elongation curve show?
The relationship between load applied to ligament/tendon & the elongation it is experiencing
84
What are the 4 regions of the load-elongation curve?
1) toe - small increase leads to straightening out of fibres 2) linear - increasing load leads to increasing straightness & stiffness 3) micro failure - deformed to maximum, progressively fail 4) yield pont - complete failure of whole tissue
85
What are the 4 phases of tendon repair?
Inflammatory phase Reparative phase Remodelling/consolidation phase Maturation phase
86
What occurs during the inflammatory phase of tendon repair?
``` Increased vascular permeability Influx of inflammatory cells Platelet aggregation Fibrin clot forms Acute local inflammation ```
87
What occurs during the reparative phase of tendon repair?
``` 3-6 weeks Formation of granulation tissue Deposition of disordered collagen fibres Neovascularisation Fibroblast proliferation ```
88
When is the remodelling phase of tendon repair?
10-12 weeks
89
What occurs during the inflammatory phase of tendon repair?
9-12 months Decrease in cellular & vascular content of repairing tissue Increase in collagen type I Becomes more organised
90
What are 4 factors that affect the mechanical properties of ligaments & tendons?
Maturation & ageing Pregnancy & postpartum Physical training Immobilisation
91
What are 3 functions of joints?
Allow movement of bones Bear weight Transfer load to MSK system
92
What are the 3 main structural classifications of joints & what is an example of each?
Fibrous - teeth joints Cartilaginous - intervertebral discs Synovial - metacarpopharyngeal joints
93
What are the 3 main functional classifications of joints & what is an example of each?
Synarthroses - immovable, mostly fibrous; sutures of skull Amphiarthroses - slightly moveable, mostly cartilaginous; IV discs Diarthroses - feel moveable, mostly synovial; hip
94
What are the 3 subcategories of fibrous/synarthroses joints?
Sutures - between bones of skull Gomphoses - peg in socket joints, teeth Syndesmoses - bones connected by cord or sheet, tibia & fibula
95
What are the 2 subcategories of cartilaginous/amphiarthroses joints?
Synchondroses - bones connected by hyaline cartilage, ribs & sternum Symphyses - pads/plates of connecting fibrocartilage, IV discs
96
What is a synovial joint composed of?
2 articulating bones separated by a cavity that is filled with synovial fluid
97
What are the characteristics of a synovial joint? (5)
* articular cartilage * joint capsule * joint cavity * synovial fluid * reinforcing ligaments
98
What are menisci?
Discs of fibrocartilage
99
What is synovial fluid?
A filtrate of blood plasma formed by synoviocytes
100
What are 2 functions of synovial fluid?
Lubricates bones | Reduces friction
101
What cells line the synovial cavity?
Synoviocytes
102
What are the 6 classes of synovial joints?
* ball & socket (hip) * condyloid (wrist) * gliding (carpals) * hinge (elbow) * pivot (neck) * saddle (MCP)
103
What are the 3 main types of cartilage?
Hyaline/articular Elastic Fibrocartilage
104
What are the 3 layers of hyaline cartilage?
Superficial Middle Deep
105
What is made of type I collagen?
Skin, tendons, organs, bone
106
What is made of type II collagen?
Cartilage
107
What is made of type III collagen?
Reticulate/connective tissue
108
What is made of type IV collagen?
Basement membrane
109
What is made of type V collagen?
Cell surfaces, hair, placenta

Phase 1 Medicine - Riona (13 decks)

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