MSK Flashcards
What is a bone fracture?
Breach in continuity of bone
When do fractures occur?
Non-physiological loads applied to normal bone;
Physiological loads applied to abnormal bone
What are the types of joints?
Fibrous, cartilagenous, synovial joints
What is rheumatology?
Medical management of joint and MSK problems
What is rheumatism?
A colloquial term for bone/joint/muscle pain
What are synarthroses?
Immovable joints, mostly fibrous (eg. skull sutures)
What are amphiarthroses?
Slightly moveable joints, most cartilaginous (eg. intervertebral discs)
What are diarthroses?
Freely moveable joints, mostly synovial (eg. hip)
What are suture joints?
Fibrous joints.
Occur only between bones of the skull (allow skull growth in development)
Adjacent bones interdigitate
Junction filled with very short tissue fibres
What are syndesmoses?
Fibrous joints.
Bones are connected by a cord (ligament) or sheet (interosseous membrane) of fibrous tissue.
Amount of movement permitted is proportional to length of fibre
What is a gomphoses?
Fibrous joint.
A peg-in-socket fibrous joint found only in tooth articulation
What are synchondroses?
The bones are directly connected by hyaline cartilage. These are usually amphiarthroses ie. slightly moveable eg. costal cartilage of the ribs
What are symphyses?
Here the connecting cartilage is a pad or plate of fibrocartilage
What are the classifications of joint?
What are the 5 components of synovial joints?
- Articular cartilage
- Joint capsule -the inner layer is the synovial membrane,
- Joint (synovial) cavity - a space filled with synovial fluid.
- Synovial fluid
- Reinforcing ligaments
What are the key components of articular (hyaline) cartilage?
Almost frictionless surface
Resists compressive loads
High water content
Low cell content
No blood supply
What are the components of cartilage?
Water, proteoglycans, collagen
Where is synovial fluid?
Covers articulating surfaces with thin film (e.g. healthy knee just 0.5 ml fluid)
How is synovial fluid modified from plasma?
Modified from plasma by synovial membrane (synoviocytes)
What is synovial fluid?
Fluid, proteins, charged sugars that bind water eg. hyaluronate
Result: slimy fluid (like egg white)
What is the function of synovial fluid?
Reduces friction during articulation
Where is the synovial membrane?
Sits on the joint capsule and encloses synovial cavity
What is the function of the synovial membrane?
Secretes synovial fluid components eg. hyaluronate
What do ligaments do?
Connect bone to bone
How are ligaments different to tendons?
- Similar to a tendon but with less regularly arranged fibres
- Can stretch up to 6% before breaking and may contain more elastic fibres than tendon (generalisation)
What is the function of tendons?
Stabilise joints
Allow muscles to be accommodated at a distance from their insertion, e.g. muscles of the forearm move the fingers. Provides a solid base (insertion to bone) on which muscles can pull
Where do most tendon ruptures occur?
The musculotendinous junction
What is a first class lever in the musculoskeletal system?
In a first class lever, the fulcrum is in the middle (the elbow joint) the force is at one end (the triceps muscle) and the resistance is at the other end (the weight being pulled).
What is a second class lever in the musculoskeletal system?
In a second class lever, the fulcrum is at one end (eg. Temperomandibular joint) the force is at the other end (the muscles of the chin) and the resistance is in the centre (the muscles attached to the coronoid process).
What is a third class lever in the musculoskeletal system?
In a third class lever, the fulcrum is at one end (eg. elbow joint), the force is in the middle (the biceps muscle) and the resistance is at the other end (the weight being pulled).
How is a ball and socket joint held in place?
Held securely in place by strong ligaments and heavy cylindrical joint capsule
What are the main stabilising ligaments at the hip joint?
Iliofemoral
Pubofemoral
Ischiofemoral
What are the tendons stabilising the shoulder?
Long head of Biceps brachii
Tendons of the rotator cuff: subscapularis, supraspinatus, infraspinatus and teres minor
What are joints?
Spaces between bones bridged by fibrous and/or cartilaginous tissue
What makes a bone a long bone?
It is in the appendicular skeleton.
It is cancellous and compact bone.
It has articular hyaline cartilage.
What type of bone is flat bone? Give some examples.
Thin inner and outer layer of compact bone.
eg. skull, ribs, sternum, scapula
What is an irregular bone? Give some examples
One that doesn’t fit any of the other categories. Examples include vertebrae and sphenoid bones
What are short bones? Give some bones
Cuboidal/round in shape.
Cancellous bone surrounded by compact bone.
Wrist and midfoot.
What is a sesamoid bone? Give some examples.
Small bones in tendons.
Patella and sesamoid.
They reduce friction on the tendon
What is bone made of?
20% organic component (osteoid - 90% type 1 collagen, 10% GAGs)
70% inorganic component (mineral - hydroxyapatite)
10% water
What is the function of the organic component of bone?
It provides elasticity
What is the function of the inorganic component of bone?
Facilitate water exchange and provides stiffness
What is woven bone?
Coarse collagen fibres with low mineral content
How quickly is woven bone produced?
It is produced very rapidly (fractures, embyronic development)
It gets remodelled
What is lamellar bone made of?
Regular parallel collagen fibres
What are the two types of lamellar bone?
Cortical and cancellous bone
What is cortical bone?
It is the outer shell of long bones, Haversians canals, osteocytes in lacunae. The lamellar and canals form an osteon. Volkmann’s canals communicate with the periosteum.
What is cancellous bone?
Lamellae forming trabeculae, oriented along lines of stress. Affected in osteoporosis.
What is a simple fracture?
A clean break in bone that causes no or very little damage to the overlying skin
What is compound ‘open’ fracture?
A broken bone piercing and oftenprotruding through the overlying skin
What is greenstick fracture?
An incomplete fracture in which the bone is bent. This happens most commonly in children.
What is a communited fracture?
A multifragmentary fracture, more than 2 pieces
What is a complicated fracture?
A broken bone that has also damaged surrounding structures or organs
What happens during the inflammatory phase of fracture healing?
Decreased blood flow. Periosteal stripping. Osteocyte death.
Haemotoma develops within the first few hours. Inflammatory and fibroblasts infiltrate the bone in the next few days
What is the reparative phase of fracture healing?
Approx 2 weeks after the fracture took place. Callus eventually hardens over a 6-12 week period.
Fibroblasts produce fibrous tissue, chondroblasts produce cartilage, osteoblasts produce osteoid. HIgh vascularity. Progressive matrix mineralisation.
What happens during the remodelling phase during fracture healing?
Woven bone remodelled into stronger lamellar bone. This can take months to years.
What are principles of fracture management?
Reduce
Immobilisation
Rehabilitate
How is vitamin D produced from the skin?
UVB rays from the sun turns cholesterol in the skin into vitamin D
What is the main function of Vitamin D?
It helps calcium and phosphorus get absorbed from our diet in the gut
What is the active form of vitamin D?
Calcitriol.
1,25 dihydroxyvitamin D
How does parathyroid hormone increase calcium levels?
Increases reabsorption from the distal convoluted tubules in the kidneys.
Increased active absorption in the duodenum and jejunum (with help from Vit D)
Increased resorption from bones via osteoclasts
What hormones influence osteoblasts?
BMP, TGF-B and FGF
How do osteoclasts resorb bone?
Release H+ and MMPs
What influences osteoclast activity?
RANKL, OPG and PTH
What is OPG secreted by?
Secreted by osteoblasts
How does OPG work?
Binds to RANK ligand, therefore neutralising it.
Reduced activation of osteoclasts and differentiation from haematopoietic stem cells.
Reduced resorption of bone
Where is RANKL secreted?
Osteoblasts
How does RANKL work?
Binds to RANK receptor on haematopoietic precurosr and osteoclasts.
Stimulates activation of osteoclasts from precursor.
Increases resorption of bone.
What is Wolff’s law?
Bone is deposited in line with where load is being placed and therefore resorbed where less load is being placed
What is fibrous joint? Give some types.
Fibrous tissue, little movement possible.
Sutures, syndemoses, gomphoses
What are primary cartilagenous joints? Give some examples
Hyaline cartilage, no movement possible.
Costosternal joints
What are secondary cartilagenous joints? Give some examples
Articulating surface of hyaline cartilage with fibrocartilage.
Manubriosternal joint, symphysis pubis, intervertebral discs
What are synovial joints?
Hyaline cartilage lines articulating surfaces
Synovial fluid lubricates joint cavity
Synovial membrane covers cavity
Fibrous joint capsule reinforced by ligaments
What are ligaments and what is their function?
Flexible bands connecting bones or cartilage together.
Strengthen and stabilise joints
What are tendons and what is their function?
Connect muscle and bone together.
Allow for transmission of force of contraction during movement
Where is procollagen produced?
It is produced inside the cell and then secreted
What is the function of bones?
Raises us from the ground against gravity
Dictates body shape
Transmits body weight
Forms joint system for movement
Protects vital structure
Contains bone marrow
Stores minerals
What is the axial skeleton?
Bones of the head and trunk
What is the appendicular skeleton?
Supports the appendages (everything but the head and the trunk)
What does fibroblast growth factor 23 (FGF-23) do?
Decreases renal reabsorption of phosphate. If phosphate level is too high, FGF-23 levels increase. If phosphate level is too low, FGF-23 levels increase.
Fracture definition:
A soft tissue injury, complicated by a breach of bone continuity
What is hyaline cartilage made of?
Water, proteoglycans and collagen.
High water and proteoglycans content
Low cell content
No blood supply
What is an entheses?
Where a tendon inserts into a bone.
What are the two types of entheses? What is the difference?
Fibrous: tendon inserts directly into bone
Fibrocartilagenous: entheses has four transitional zones
Where do osteoblasts come from?
Mesenchymal cells -> osteoprogenitor cells -> osteoblasts
What does osteiod contain?
Type 1 collagen, GAGs and proteoglycans
Do osteoblasts create the osteoid or the matrix first?
Osteoid (provides elasticity) then matrix vesicles rich in minerals (mineralises the extracellular matrix by depositing hydroxyapatite within collagen fibrils)
Where do osteoclasts come from?
Bone marrow -> monocytes -> specialised macrophage (osteoclasts)
How do osteoclasts work?
Secrete acids, which break up the hydroxyapatite, releasing calcium and phosphate
What is coupling?
Bone formation occurs at sites of previous bone resorption
Why do we need to remodel bone?
Repair damage, obtain minerals, form bone shape, reorganise fibrils
How does RANKL work?
Binds to RANK on the surface of pre-fusion osteoclasts that stem from myeloid precursors, converting them into multinucleated then finally activated osteoclasts
