MSK case Flashcards
Functions of the musculoskeletal system: (6)
- Protects organs
- Stores and releases fat
- Produces blood cells
- Stores and releases minerals
- Facilitates movement
- Supports the body
Mineral phase of bone:
- Hydroxyapatite (a calcium phosphate)
Organic phase of bone:
- Collagen and other proteins
Bone cells: osteochondral progenitor cells
- Undifferentiated stem cells
Bone cells: Osteoblasts
- Make new bone
Bone cells: osteocytes
- Maintain the activity of the bone
Bone cells: Osteoclasts
- Reabsorb (remove) bone
Types of bone: (2)
- Cortical bone
- Trabecular bone
Bone and calcium:
- Role of bones
- Amount of calcium
- Bone is the main body store of calcium
- Body contains approximately 1Kg of calcium and 99% of that is bone
Calcium regulation: Parathyroid hormone
- Secretion
- Action on kidney :Ca, Ph, VitD
- Action on bone
- Secreted from the parathyroid glands
- Actions on the kidney:
. Increases Ca Resorption in distal tubules
. Increases Phosphate excretion
. Increases formation of active vitamin D - Actions on bone:
. Stimulates bone Resorption
Vitamin D sources:
- Mostly formed from the action of UV light on the skin
- Also found in some foods (oily fish)
- Highly fat soluble, large amounts stored in the adipose tissue
Vitamin D activation pathway: - 2 Reactions - Liver: cholecalciferol to ..... - Kidney: ...... to active vit D Regulated by the enzyme:
- 2 hydroxylation reactions
- In the liver:
Cholecalciferol to calcidiol - In the kidney:
Calcidiol to active vitamin D - regulated by the enzyme 1a-hydroxylase
Actions of vitamin D:
- Bone
- Intestine (Ca,Ph)
- Bone: stimulates bone resorption
- Intestine:
. Stimulates calcium absorption
. Stimulates phosphate absorption
Calcitonin:
- Secretion
- Effect
- Secreted by parafollicular cells of the parathyroid gland
- Opposes the effect of PTH
Regulation of low calcium levels:
- Parathyroid gland releases PTH
- Calcium levels increase
Bone density:
- A measure pf the amount of minerals present in the bone
Factors effecting bone density: (3 main)
- Availability of substrates . Ca intake, Ca absorption, PTH functionality - Physiological factors . Exercise, BMI, smoking - Biochemical factors . Hormones
Groups that require calcium supplementation:
- Vegans
- Lactose intolerance
Bone density after menopause:
- Decreases
Macroscopic bone structures: (2)\
- Axial
- Apendicular
- Axial: skull, spine, ribs
- Appendicular: Limbs, pelvis, shoulders
Osteology:
- E
- M
- D
- Epiphysis: ends of the long bone
- Metaphysis: Wide part of the bone. Growth occurs here
- Diaphysis: long part of the bone (shaft)
Cortical bone: (4)
- Type
- Skeletal weight %
- Organisation
- Turnover rate
- Compact bone
- 80% skeletal weight
- Organised into Haversian systems
- Slow turnover
Cancellous bone: (5)
- Type
- Density
- Wolff’s law
- Turnover rate
- Function
- Spongy/trabecular
- Less dense
- Remodels due to Wolff’s law
- High turnover
- Haematopoiesis
Haematopoiesis:
- The formation of bloods cellular components
Osteoblast products:
- Type 1 collagen
- ALP - initiates calcification
- Calcium phosphate
Osteocytes further:
- Positioning
- Derivation
- Causes
- Lie within lacunae in mature bone
- Derived from osteoblasts
- Responsible for bone maintenance
Wolff’s Law:
- Bones will adapt based on the stress or demands placed on them
Primary bone healing: (2)
- Absolute stability + compression
- No callus
Secondary bone healing:
- Relative stability
- Callus formation
Stages of bone break/heal: (5)
- Fracture
- Haematoma forms: blood surrounds the fracture, inflammatory cells arrive
- Soft callous: repairing stage. Osteoblasts arrive, forming new unmineralised bone
- Hard callous: soft callous becomes mineralised due to calcification
- Remodelling
Stages of bone healing: haematoma
- Blood surrounds the fracture, inflammatory cells arrive, causing inflammation
Stages of bone healing: soft callous
- Osteoblasts form new uncalcified bone around the fracture.
Stages of bone healing:hard callous
- Soft callous is calcified
Stages of bone healing: remodelling
- 12-18 months for the bone to revert to its original shape without surgery.
Factors influencing bone healing: (2)
- Variables
- Fracture variables
- Patient variables
Fracture variables: (3)
- Blood supply
- Complexity
- Immobilisation
Patient variables: (5)
- Nicotine
- Diabetes mellitus
- Diet/deficiencies
- COX-2 inhibitors
- HIV
Functions of skeletal muscle (4)
- Movement
- Control posture
- Remove and store glucose
- Generate heat (temp. regulation)
Sarcomere:
- Distance between two z lines
Striations:
- I band
- A band
- Which band shortens
- I band: appears light
- A band: appears dark
- The I band appears to shorten
Isotonic movement:
- muscle resists a constant weight, changing length in the process
Isometric movement:
- Contraction under tension, muscle doesn’t change length
An action potential is:
- A regenerating depolarisation of membrane potential that propagates along an excitable membrane
Excitatory synapses: (4)
- AP in pre-synaptic cells causes a release of vesicles
- Transmitter diffuses to receptors on post-synaptic cell.
- Activation of receptors depolarises (via Na+ entry) cell to threshold
- Initiating AP in post-synaptic cell
Neuromuscular Junction (NMJ) structure: - Active zones:
- Top of cleft
- Bottom of cleft
- Aligned with clefts in the post-junctional membrane
- Top of the clefts = nACH receptors (minimal diffusion distance)
- Bottom of clefts = voltage-gated Na+ channels (distance unimportant)
Concentric contraction:
- shortening of the muscle during contraction
Eccentric contraction:
- Lengthening of the muscle during contraction
Skeletal muscle relaxants: (3)
- B T
- C
- S
- Botulinum toxin: Prevents release of Ach-containg vesicles (muscle paralysis)
- Curare: blocks nAChrRs to cause paralysis
- Succinylcholine: short-acting block of nAChR
Sarcoplasmic reticulum (SR) and T tubules:
- SR is a Ca store
- T tubules conduct AP into the muscle fibre
- T tubule AP stimulates Ca release from the SR, stimulates contraction
Functions of the SR: (3)
- Stores calcium
- Rapidly releases calcium (AP triggered)
- Rapidly restores calcium (using ATP-driven calcium pumps)
T tubule function:
- To convey quickly the action potential deep inside the fibre
Triad:
- A t tubule and two SR’s
Membrane receptors in triads: (2)
- voltage sensor:
- Ca release channel
- DHP receptors: voltage-sensors
- Ryanodine receptors: calcium release channels
Tetanic contraction:
- At high rates of stimulation, no muscle relaxation is seen (fused)
How to measure osteoblastic activity:
- The enzyme alkaline phosphate acts as a marker
Development of the wrist:
- As the skeletal system matures, carpal bones ossify
- Becoming visible on radiographs, this allows for an estimation of age
Torus fractions:
- The bone buckles, but the integrity of the surface of the bone on the convex side is maintained
- The bone will remodel over time
Greenstick fracture:
- Usually mid-diaphysial
- Damage to convex surface but fracture is incomplete
Growth plate fractures:
- Salter Harris fractures
- 5 types
Type 1 SHF:
- SLIPPED
- Shift between epiphysis from the metaphysics
Type 2 SHF:
- ABOVE
- Fracture extends through meta-physis and physis
Type 3 SHF:
- LOWER
- Fracture extends through from the physis to the epiphysis
Type 4 SHF:
- THROUGH/TRANSVERSE
- Fracture passes through the physis, epiphysis and metaphysics
Type 5 SHF:
- RAMMED/RUINED
- Physis is crushed
Rickets causes: (4)
- Causes: . Prematurity . Nutrition . Maternal vit D deficiency - Lack of sunlight
Rickets symptoms:
- Skeletal changes
- Growth pains
Osteopenia:
- Reduced bone mineral density
- Without differentiating between reduced BDM and oesteroperosis
Effects of age on bone: (3)
- Resorption greater than formation
- Osteoporosis
Sarcopenia:
- Accelerated loss of muscle mass and function
Acute pain:
- Duration
- Aetiology
- Purpose
- MSK examples
- Short
- Result of injury or disease
- Important protective role
- Fracture, sprains
Chronic pain:
- Duration
- Aetiology
- Purpose
- MSK examples
- Long (>3-6 months)
- Can be related or unrelated to tissue damage
- None
- Chronic back pain, osteoarthritis
Stress definition:
- Physiological changes
- A state of disharmony or a threat to homeostasis
- Alertness, focus and energy
Endochondral ossification steps (5)
- ……. Cells differentiate into ……., forming a cartilage model
- central ….. undergo ….. altering the matrix they secrete, enabling ……
- ….. undergo …….., blood vessels invade bringing ……
- Primary ….. centre forms in the centre …….
- Secondary…..
- Begins in utero Mesenchymal cells differentiate into chondrocytes, forming a cartilage model for the bone
- Central chondrocytes undergo hypertrophy, altering the matrix they secrete, enabling mineralisation
- Chondrocytes undergo apoptosis, blood vessels invade, bringing osteogenic cells
- Primary ossification centre forms in the centre, increasing bone width
- Secondary ossification centres form at epiphyseal regions after birth
Intramembranous ossification:
- Steps (5)
1. Mesenchymal cells differentiate into……
2. Osteoblasts become entrapped by the …..
3. ….. bone and ….. form
4. ……. bone forms superficial to ……
5. Blood vessels form the ………
- Mesenchymal cells differentiate into osteoblasts and group up (ossification centres)
- Osteoblasts become entrapped by the osteoid they secrete, making them osteocytes
- Trabecular bone and periosteum form
- Cortical bone forms superficial to trabecular bone
- Blood vessels form the red marrow
