Skeletal Physiology Flashcards
1
Q
What are the basic functions of the bone/skeletal system?
A
- Ribcage protects heart and lungs, cranium protects brain
- Yellow bone marrow stores and releases fats
- Red bone marrow responsible for haemopoiesis (process of blood cell formation)
- Calcium and phosphorus store and release minerals to maintain balance and provide strength
- Attached to skeletal muscles via tendons to facilitate movement
- Supports the body with structural framework
2
Q
Briefly describe the axial and appendicular skeleton
A
- Axial (80 bones) - longitudinal axis (vertical line), forms the ‘trunk’
- Appendicular (126 bones) - upper and lower extremities (appendages), girdles that connect limbs to axial skeleton, ‘branches’
3
Q
Describe the macrostructures of bones
A
- Medullary cavity - home to marrow/blood vessels, reduces weight of bone
- Compact bone (cortical)
- Periosteum - contains bone cells = allows bone to grow in thickness
- Articular cartilage - reduces friction and absorbs shock
- Spongy bone (trabecular)
- Proximal epiphysis - expanded end
- Diaphysis - shaft/body of a bone
- Distal epiphysis - expanded end
4
Q
Describe the cortical (compact) bone tissue
A
- Strongest bone tissue
- Compact structural units = osteons
- Resistive to bending
- Most of diaphysis in long bones
- High stress, few directions
5
Q
Describe the trabecular (spongy) bone tissue
A
- Small needle-like piece of bone
- Forms core of epiphyses in long bones
- Areas of low stress, but many directions
6
Q
Describe the parts of the organic bone matrix (40%)
A
- Collagen (90%) - scaffold, provides tensile strength
- Proteins (osteocalcin, osteonectin) and growth factors (IGF, IL-6) - promote mineralisation of collagen scaffold
7
Q
What is the component of inorganic bone matrix (60% of matrix)?
A
Mineral salts - mainly calcium and phosphate ions, form crystals to increase stiffness, give compressive strength
8
Q
Describe the cells of bone tissue
A
- Osteogenic - bone stem cell, only bone cell that divides, differentiates into osteoblast and osteocyte
- Osteoblast - build bone tissue, initiate calcification, known as ‘formation’, some become osteocytes
- Osteocyte - mature bone cell, main cell of bone tissue, assists with daily metabolic activities of bone
- Osteoclast - remove bone tissue, release enzymes and acids, digest protein and mineral components of extracellular matrix, known as resporption
9
Q
What is bone remodeling and the 3 key purposes?
A
- Cycling of resorption and formation
1. Repair microdamage
2. Adapt to mechanical loading
3. Maintain blood calcium homeostasis
10
Q
What minerals are involved in bone remodeling?
A
- Calcium and phosphorous - creation of bone
- Magnesium - calcium absorption
11
Q
What vitamins are involved bone remodeling?
A
- Vit A - osteoblast activity
- Vit C - collagen synthesis
- Vit D - calcium absorption in GI tract
- Vit B12 - synthesis of bone proteins
12
Q
What hormones are involved in bone remodeling?
A
- Insulin-like growth factors (IGF) - important during childhood
- Parathyroid hormone (PTH) and calcitonin - calcium homeostasis
13
Q
Describe DXA
A
- Dual energy X-ray absorptiometry
- Exposed to a very small amount of radiation
- Provides measures of bone mineral density (BMD)
- 2D (whole body and regional)
- Provides body composition estimates
14
Q
Describe PQCT
A
- Peripheral quantitative computed tomography
- Scanning of lower leg and forearm
- Scans at fixed points of the limb - 4%, 14%, 38% and 66%
- Provides estimates of volume (3D properties)
- Differentiate cortical and trabecular bone
15
Q
Define Wolfss Law and Mechanical Stress
A
- Wolffs - bone will optimise structure as to withstand functional loading
- Mechanical Stress - localised response of bone to loading
16
Q
What are the components of the Mechanostat Theory?
A
- Strain Magnitude - trivial, physiological, overload, pathological
- Strain rate - isometric vs dynamic
- Strain Distribution - uneven loading important in osteogenesis
- Strain cycle - number of repetitions
17
Q
Describe osteoporosis
A
- Fragility related bone condition
- Systemic skeletal disease
- Lack of bone mineral mass
- Increased risk of fragility fractures
18
Q
Who suffers from osteoporosis?
A
- Elderly men and women
- Middle aged women (menopause)
- Athletes (training, caloric intake, body weight)
- People with eating disorders (caloric intake, body weight)
- Paralysed
- Bedridden
- Inactive - sedentary lifestyle
- Astronauts
19
Q
Describe stress fractures
A
- Stress related bone condition
- Highly prevalent in athletes and military personnel
- Caused by excessive repetitive loading
20
Q
Can we prevent bone breaks and fractures?
A
- Breaks - unfortunate and unpredictable events
- Stress fractures - more manageable, but still hard to predict due to complex nature of stress fracture risk (mechanical strain, nutrition, genetics)
