MSK Flashcards
Tropocollagen made up of…
Triple helices of polypeptides (2x alpha1 and 1x alpha2)
Type of collagen in bone
Type 1
What proteinases break down collagen?
Collagenases and cathepsin K (in bone)
Type I collagen found where?
Bone, tendon, ligaments, skin
Type II collagen found where?
Hyaline cartilage, elastic cartilage
Type III collagen found where?
Alongside Type I in wound healing
Type IV collagen found where?
Basal lamina
Type V collagen found where?
Cell surfaces
Type X collagen found where?
Growth plate
6 skeleton functions
- Mineral storage
- Protection
- Movement – lever system
- Body shape
- Bone marrow
- Transmits weight
How many bones in appendicular skeleton?
126
How many bones in axial skeleton?
80
Long bones
Tubular shape, hollow shaft
Femur, phalanges, tibia, fibula
Short bones
Cuboidal in shape
carpals, tarsals
Flat bones
Plates of bone, often curved (protection)
skull, scapula
Irregular bones
Varying shapes
vertebrae, sacrum, scapula, coccyx
Sesamoid bones
Ovular and within a tendon
Patella
3 types of fibrous joints (no/little movement)
Sutures (junctions between adjacent skull bones)
Gomphoses (peg and socket joints - teeth)
Syndesomes (connected by membranes - between radius and ulna)
Cartilaginous joints
Hyaline cartilage connects bones
Stretches to allow some movement
Pelvic symphysis
Synovial joints composition
Freely moveable
Joint capsule: outer = fibrous
Inner = synovial fluid
6 types of synovial joint
Hinge
Pivot
Plane
Ball and Socket
Condyloid
Saddle
Condyloid joint example
Metacarpophalangeal joint
Saddle joint example
Carpometacarpal joint
Plane joint example
Carpal/tarsal joints
Macro-composition on outside of bones
Cortical - dense, solid, only space for cells and blood vessels
Macro-composition on inside of bones
Trabecular - Network of bony struts (like sponge), many holes filled with bone marrow
Osteoclasts role
Secrete:
-Acid to breakdown calcium hydroxyapatite
-Collagenase to breakdown collagen
Bone matrix made from…
Calcium hydroxyapatite
Collagen protein
4 types of bone cells
Osteoblasts
Osteocytes
Osteoclasts
Bone lining cells
Interstitial bone growth
Growth form within
Appositional bone growth
Growth from outside
2 enzymes that form bonds between the triple helices of a tropocollagen molecule
Lysyl oxidase
Pyridinolines
Type I collagen formation/structure
Synthesized by fibroblast, procollagen secreted and converted to collagen
One collagen molecules consists of 2 alpha1 and 1 alpha2 polypeptide chains
2/3 of molecules consists of glycine, proline, hydroxyproline. Every 3rd aa glycine
Bone extracellular matrix
Collagen and elastin in gel containing proteoglycans
Chondrocytes trapped in lacunae which maintain and repair
Bone lacunae
Small, spindle-shaped spaces
Each containing an osteocyte that is left behind by osteoblasts during the process of remodelling
Osteoblast role
Building cells in the bone
Osteocyte role
Energy metabolism, phosphate metabolism
What inhibits and promotes release of PTH from the parathyroid glands?
Low serum Ca2+ promotes release of PTH
High serum Ca2+ inhibits release of PTH
Synthesis of Vitamin D
Vit D from skin/diet first hydrolysed by liver by 25-hydroxylase to form calcidiol
Further hydrolysis by 1-hydroxylase forms active vitamin D (calcitriol)
PTH stimulates hydrolysis in kidney
High calcitriol inhibits PTH release
Vitamin D effect in bone
Stimulates Ca2+ and phosphate resorption
Stimulates osteoclast breakdown of bone in Ca2+ and phosphate
Where is calcitonin produced?
Parafollicular cells (C cells) of thyroid
Calcitonin release in response to…
High plasma concentration of Ca
Calcitonin action
Blocks PTH release
Inhibits Ca2+ absorption in small intestine
Stops Ca2+ reabsorption in kidneys
A myocyte (muscle cell) is surrounded by…
Endomysium
What is a fascicle?
Multiple myocytes surrounded by perimysium
What is muscle proper?
Multiple fascicles surrounded by epimysium
Neurotransmitter in skeletal, smooth and cardiac muscle
Skeletal - ACh
Smooth - ACh/NA
Cardiac - ACh
3 types of muscle fibres
Type I - slow oxidative fibres
Type IIa - oxidative fibres
Type IIx - glycolytic fibres
Features of Type I muscle fibres
Fatigue - resistant
Colour - red
Metabolism - oxidative
Glycogen content - low
ATP synthesis - aerobic
Mitochondria - high
Muscles - soleus
Features of Type IIa muscle fibres
Fatigue - resistant
Colour - red
Metabolism - oxidative
Glycogen content - abundant
ATP synthesis - aerobic
Mitochondria - higher
Muscles - gastrocnemius
Features of Type IIx muscle fibres
Fatigue - fatigable
Colour - white
Metabolism - glycolytic
Glycogen content - high
ATP synthesis - anaerobic
Mitochondria - fewer
Muscles - biceps brachii
H bands in muscle myofibrils
Between small filaments
A bands in muscle myofibrils
Length of thick filament
I band in muscle myofibrils
Gap between thick filaments
At muscle contraction _ and _ bands disappear
H and I
Patellar tendon is…
A ligament
Tendons and ligaments composition
Dense connective tissues consisting of mainly parallel fibres (to enable tissue to sustain high tensile strains)
20% cells (fibroblasts) which synthesise ECM
80% ECM
Sparsely vascularised (poor capacity for healing)
Structure of Tendons and Ligaments
Tropocollagen pack to form Microfibrils
Microfibrils pack to form Subfibrils
Subfibrils pack to form Fibrils
Fibrils packs to form Fascicles
Endotenon surrounds each Fascicle
Fascicles packed together and surrounded by Epitenon
Major component of tendon and ligament is…
Collagen (mainly Type I, some Type III, small amounts of V, VI, IX)
90-95% of dry weight
Minor component of tendon and ligament
Proteoglycan
Regulate fibre diameter during fibrillogenesis
Aid in keep fibrils together
Act as lubricant for collagen fibres gliding over each other
1-5% of dry weight
4 differences between ligaments and tendons
Their connections
Lower collagen I content in ligaments
Higher elastin content in ligaments
Fibres organised more randomly in ligaments (highly organised in tendons)
2 types of insertion for ligaments into bone
Fibrous insertion
Fibrocartilage insertion
FIbrous insertion
Formed through intermembranous ossification
Calcified collagen fibres (Sharpey’s fibres) into bone
Fibrocartilage insertion
Formed through endochondral ossification
Gradual change from collagenous ligament -> fibrocartilage -> mineralised cartilage -> bone
Total serum calcium in body
2.4 mmol/L
Ionised serum calcium in body
1.1 mmol/L
Calcium functions (5)
Muscle contraction (Ca2+ efflux from SR)
NT release (Ca2+ into synaptic terminal)
Conduction system of heart
Clotting cascade
Bone integrity
Daily Ca intake
1000mg (most comes out in faeces)
Golgi Tendon Organ
Encapsulated sensory receptors proprioceptors activated by stretch or muscle contraction
Located in tendons near junction with muscle
3 functional classifications of joints
Synarthroses - immovable joints, fibrous (skull sutures)
Amphiarthroses - slightly moveable joints, cartilaginous (intervertebral discs)
Diarthroses - freely moveable joints, synovial (hip)
3 structural classifications of joints
Fibrous - teeth sockets
Cartilaginous - intervertebral discs
Synovial - metacarpophalangeal
3 types of fibrous joints
Sutures
Syndesmoses
Gomphoses (peg-in-socket joint in teeth)
2 types of cartilaginous joints
Synchondroses - costal cartilage
Symphyses - pubic symphysis, intervertebral discs (annulus fibrosus)
Articulating bones in a synovial joint are separated by…
A fluid-filled cavity
5 components of a synovial joint
Articular cartilage
Joint capsule
Joint (synovial) cavity
Synovial fluid
Reinforcing ligaments
3 types of cartilage in joints
Fibrocartilage
Hyaline Cartilage
Elastic Cartilage
What are menisci?
Discs of fibrocartilage
What are bursae?
Fluid-filled sacs lined by synovial membrane
Features of hyaline cartilage
Almost frictionless surface
Resists compressive loads
High water content
Low cell content
No blood supply
3 components of cartilage
Water
Proteoglycans
Collagen
How does the synovial membrane increase surface area?
Villi on surface
How is synovial fluid modified from plasma?
Synoviocytes on synovial membrane
1st class lever (joints)
Fulcrum in middle (elbow)
Force at one end (triceps muscle)
Resistance at other end (weight being pulled)
2nd class lever (joints)
Fulcrum at one end (temperomandibular joint)
Force at other end (muscles of chin)
Resistance in centre (muscles attached to coronoid process)
3rd class lever (joints)
Fulcrum at one end (elbow joint)
Force in middle (biceps muscle)
Resistance at other end (weight being pulled)
6 types of synovial joint
Ball-and-socket
Condyloid
Gliding
Hinge
Pivot
Saddle
