Mechanical Role of the Skeleton Flashcards
What are the functions of the skeleton
- Locomotion _Lever - Respiration - Protection - Calcium store - Haematogenetic factory (houses bone marrow).
What role does the skeleton have in calcium storage
98% of the body’s calcium is stored in the skeleton. Calcium is the most regulated ion in the body. A vital level needs to be maintained - cannot be too high or too low.
What seven adaptations does the skeleton have for bipedal locomotion
- Spinal curves
- Shock absorption of discs
- Weight bearing axis of hip and knee
- Tripod arrangement of the foot
- Shape of the thorax
- Soleus slow muscle
- TA (tendon achilies) energy absorption.
How is the weight bearing axis of the hip and the knee adapted for bipedal locomotion
The centre of mass is close to the axis of rotation of the hip.
How is the weight bearing axis of the knee compromised in osteoarthritis
The end result of OA is loss of extension in the knee. This makes you need to walk with bent knees which makes walking difficult.
How is the shape of the thorax adapted for bipedal motion
Vertebral bodies are positioned quite far forwards.
How is the tendon achilies adapted to bipedal motion
This tendon has elastin as well as collagen which enables travelling of long distances with little energy.
In which age groups is the skeleton most likely to fail
In the young and the old.
What are the three most likely modes of failure of the skeleton
- Perinatal - in the young
- Trauma - in the middle aged
- Osteoarthritis/osteoporosis in the older generation.
How can perinatal segmentation fail
The mesoderm either side of the midline segments into block to form vertebral bodies. This segmentation can fail and this can lead to indiscreet vertebrae or failure of proper formation leading to the creation of a wedge shaped vertebrae.
What can failure of segmentation lead to
Congenital scoliosis.
Other than failure of segmentation, what is a second perinatal mode of failure of the skeleton
Failure of formation.
What are the requirements for the healing of fractures
Cells, growth factors and blood vessels.
What are the initial steps involved in fracture healing
Blood enters the gap in the broken bone. This acts as a scaffold as it beings to clot.
What will stop the healing and formation of new bone
Movement of the broken bone.
What is the possible yield strain for granulation tissue
Granulation tissue can be stretched quite a lot before it becomes damaged. The yield strain is 100% so granulation tissue can be stretched to double it’s size.
Above what yield strain will prevent healing and formation of new bone
Movement causing more than 2% strain on the bone will prevent formation of new bone in healing.
How do bones need to be aligned for proper healing
Bones do not need to be lined up to heal however to heal properly the bone should be placed in a good position in order for the least strain on the joint.
What is the name of the new bone that begins to form to repair fractures
The callus
What is the origin of the external callus
The periosteum and soft tissue which contributes cells and blood vessels to the healing process.
What is the origin of a gap callus
Bone marrow
What is the origin of a direct/primary callus
The cortex.
What are the two mechanisms of fracture repair
Indirect and direct.
What is formed in indirect fracture healing
An external callus. This is new bone of a semi-rigid fixation.
How does direct fracture repair work
There is no callus formation - it is an extension of remodelling.
What type of fixation occurs in direct fracture repair
Rigid fixation
What type of fixation occurs in indirect fracture repair
Semi-rigid fixation.
What are two bones in the body with poor healing ability
The clavicle and the tibia.
What is the callus
New bone
By which method - direct or indirect - do most bones heal
The indirect repair process.
Why is the callus formed in indirect fracture repair semi-rigid
This is so that the body knows that it is damaged and reduces movement of the bone.
Which part of the bone composition is gives it strength
The organic collagenous component
Which part of the bone gives it stiffness
The inorganic hydroxyapatite component.
What is the process of direct fracture repair
Osteoclasts go across the crack and bone is removed before new bone is laid down. This “fools” the body into thinking it has a giant microcrack therefore the healing process is just an extension of bone remodelling.
What is the name of an infectious condition that can affect growth plates and therefore growth in children
Osteomyelitis.
What is mechanotransduction
The sensing of a mechanical stimulus and conversion of this to a biological response. Bone cells must receive signals from movement of the bones in order to work.
What are the possible consequences of treatment
Treatment can take up to two years and more. This can have a huge impact on the patients life in terms of independence and earning, as well as pain, muscle weakness etc.
What is the big disadvantage of OP fractures in older people
Loss of independence which many people do not recover.
