MSK physiology Flashcards
State the functions of the skeleton
- Protect vital organs
- Houses bone marrow
- Shape/support
- Allows locomotion/movement
- Stores calcium
- Transmits body weight
State the different classes and shapes of bone
Long Short Flat Irregular Sesamoid
Give 3 examples of a long bones
Femur
Phalanges
Metacarpals
Give an example of a short bone
Carpal
Give 4 examples of flat bones
Rib
Some bones of the skull
Sternum
Ileum of pelvis
Give 3 examples of irregular bones
Vertebra
Mandible
Sacrum
Give an example of a sesamoid bone
Patella
What are the two macrostructures of bone?
Cortical (compact)
Trabecular (spongey)(cancellous)
What are the two microstructures of bone
Woven 1
Lamellae 2
What are the 3 parts of a long bone?
Epiphysis (end)
Metaphysis
Diaphysis (shaft)
Where are the epiphyseal plates located?
Between the epiphysis and metaphysis
What are the two devisions of the skeleton?
Axial
Appendicular
Where in the long bone is trabecular bone most likely to be found?
Epiphysis
Describe the structure of trabecular bone
Bone struts with hole in between, filled with bone marroq
Describe cortical bone
Dense, located at the periphery of the diaphysis in long bones
Describe woven bone
Primary bone
Poorly organised
No clear structure
Lay down quickly
Describe lamellae bone
Secondary bone
Made slowly
Highly organised
In layers
What is the importance of hallow areas in bone
- Reduce mass
- Mass away from neural axis
- House bone marrow
What is the importance of having wide ends of bone
-Load spread over a larger SA
What is the importance of having trabecular bone within a long bone
- Reduces mass
- Load spread over larger SA/structural support
Describe the composition of bone
Inorganic 60%
Organic 30%
Water 10%
What makes up the inorganic component of bone?
Calcium hydroxyapatite
What makes up the organic component of bone?
90% Collagen
10% Non-collagenous proteins e.g Glycoproteins/Protoglycans
What are the two types of bone formation?
Intramembranous ossification
Endochondral ossification
Define intramembranous ossification
Formation of primary bone with no prior cartilaginous template/proformer
What type of bones are formed by intramembranous bone formation
Flat bones
Describe the process of intramembranous ossification
Osteoprogenitor cells within a primitive mesenchyme develop into osteoblasts
Osteoblast secrete osteoid (mainly type 1 collagen)
Osteoid becomes ossified by calcium hydroxyapatite also secreted by osteoblasts
What type of bones are formed by endrochondral ossification?
Long bones
Describe endrochondral ossification
1)Proformer cartilage - hyaline
2)Shaft of the proformer is calcified
3)Bony colar develops
4)Collar penetrated by blood vessels - bring more osteoprogenitor cells
5)Osteoprogenitor cells develop in osteoblasts
Osteoblast secrete osteoid
6)1 primary ossification centre is developed
7)2 primary ossification centres later develop in the epiphyses
8)Expansion of the ossification centres -
9)Cartilage proformer reduced only to the epiphyseal plates
10) Lengthening via epiphyseal plates
11) Closure of epiphyseal plates
Two what hormones is the epiphyseal cartilage particularly responsive to?
GH Sex hormones (hence growth spurt at puberty)
Which bone cells secrete RANK ligand?
Osteoblasts
Which cells have high alkaline phosphate activity?
Osteoblasts
Describe the function of osteoclasts?
Bone resorption
Dissolve the mineralised matrix
Breakdown collagen
What do osteoblasts secrete to dissolve the mineralised matrix?
Hydrochloric acid
What do osteoblast secrete in order to breakdown type 1 collage of bone?
Cathepsin K
What are the reasons for bone remodelling?
Repair damage Obtain calcium Form bone shape 1 woven to 2 lamellar bone In response to loading - exercising Reorganise fibrils to improve mechanical strength Pathological
Give an example of a bone formed by a combination of intramembranous and endochondral ossification?
Scapula
What type of collagen is found in basement membranes?
IV
Where is type I collagen found?
Bone, teeth, skin, ligament, tendon
Where is type II collagen found?
Cartilage
What type of collagen is found at the liver/kidneys/spleen/uterus/arteries
III - Reticulin
How is reticulin different from the other types of collagen?
Forms branched fibres
Where is type V collagen found?
Placenta
Which collagen types form fibrils?
I, II, III, V, XI
Describe the structure of a collagen fibre
Triple polypeptide alpha helix = tropocollagen (cross linking)
Overlapping tropocollagen molecules = collagen fibril (cross linking)
Several collagen fibrils = collagen fibre
How is collagen synthesised?
Tropocollagen molecules synthesised by fibro/osteoblast and secreted
Collage fibrils/fibres arranges extracellularly
What is the purpose of collagen in the organic bone matrix
Provide tensile strength
What is the purpose of protoglycans in the organic bone matrix?
To withstand pressure
What are the properties of protoglycans
Negative charge Allows binding of water Friction free surfaces Compressive stiffness Can also be used a signalling molecule
Where are protoglycans found?
All cartilaginous tissues
How does cartilage breakdown occur
Inflammatory response - cytokines
Chondroclasts release protienases in response to cytokines
What is the role of integrins in terms of bone?
Collagen and fibronectin receptors
Control cell shape, movement and can alter gene expression by a kinase cascade
Allow cross talk between ECM and cells
What provides the function of bone
Extracellular matrix
How does a deficiency of sex hormone lead to someone being tall?
Late closure of the epiphyseal plates
What type of cells are osteoblasts derived from?
Mesenchymal
What type of cells are osteoclasts derived from?
Haemopoetic cells
Where in the bone do osteoblasts lie?
Howship’s lacunae
What are the sex hormone stimulators of?
Bone growth
What is growth hormone a stimulator of?
Growth of epiphyseal cartilage
What is calcium needed for?
Blood clotting
Nerve function
Muscle contraction
Where is calcium stored?
Skeleton - Calcium hydroxyapatite
In what different forms does calcium exist in the body? Which in the most imp
- Ionised*
- Complex
- Bound to plasma proteins (not filtered at kidneys)
How does pH affect the extracellular (ionised) Ca?
Increase in pH
Increased negative charge on albumin
Increased binding of Ca
Decreased extracellular Ca
What hormones are involved in Ca homeostasis?
Parathyroid hormone
Calcitonin
Vitamin D
Where is parathyroid hormone released from?
Chief cells of parathyroid gland
Where is calcitonin released from?
Parafollicular C cells of thyroid follicles
Where is vitamin D (inactive D) synthesised?
Skin, in the presence of UV radiation
What is the active form of Vit D
1,25-hydroxyvitaminD
Where is Vitamin D activated
1) Liver
2) Kidney
What is the overall aim of PTH?
Increase Ca serum levels
What are the individual actions of PTH?
1) Increase bone resorption - increase osteoclast activity
2) Increase Ca reabsorption at the kidney - DCT
3) Decrease phosphate reabsorption at the kidney - PCT
4) Activate vitamin D (at kidney 1-hydroxylase) - increase absorption of Ca and phosphate
What is the overall action of calcitonin? How does it do this?
Decrease serum Ca levels
Decrease bone resorption - decrease osteoclastic activity
What are the variables of strain put on bone?
Magnitude Frequency Hold/rest periods No. of cycles Site Age Drugs
What affect does increased physical activity have on bone?
Increased activity
Increased strain
Bone formation
Define a fracture
A soft tissue injury further complicated by a breach in continuity of the bone
In terms of bone remodelling, what is coupling?
Formation occurring at the same sites as resorption is taking place
Other than coupling, what is an important factor of bone remodelling?
Balance
Which bone cells CONTROL bone remodelling?
OsteoBlasts
Which cells secrete RANK-Ligand
Osteoblasts
Where are RANKL receptors found?
Osteoclasts
What is the role of RANKL?
Stimulates resorption - osteoclasts to release Cathepsin K and HCl
What is the role of Osteoprotegrin?
Prevents RANK-RANKL binding by binding to RANKL
Increases bone density (prevents bone resorption)
What other factors beside RANKL/OPG influence bone remodelling?
Hormones (endocrine) including 1,25 dihydroxyvitamin D PTH/PTHrP Oestrogen Leptin Paracrine/autocrine including Prostaglandins Interleukin-1 (IL-1) Interleukin-6 (IL-6) Tumour necrosis factor (TNF)
What are the stages of fracture healing?
Haematoma/Inflammation Soft callus(repair) Bony callus(repair) Remodelling
Why do bones break?
Normal bone - abnormal load
Abnormal bone - normal load
State the different types of fracture
Comminuted Spiral Wedge Open Transverse Oblique Avulsion Segmental Impact Torus (looks like welling)
What happens during the haematoma phase of fracture healing?
Death of osteocytes
Periosteal stripping
What happens during inflammation of fracture healing?
Neovascularisation
Osteoclasts clear debris
What happens during repair stage of fracture healing?
Cartilage proformer - soft callus
Osteoblast secrete osteoid - hard callus
Increased vascularity
What happens during the remodelling stage of fracture healing?
Woven bone to lamellar bone
Vascularity returns to normal
How is fracture healing (closed) unique?
No scaring
What are the principles of fracture management?
Reduce
Immobilise
Rehabilitate
What factors affect fracture healing?
Patient -Age -Sex The fracture -site -bone-cortical v cancellous -vascularity Treatment