Musculoskeletal System 2 Flashcards
What is hypertrophy?
Increase in cell size
No change in cell number
What is hyperplasia?
No change in cell size
Increase in cell number
What is the initial stage of longitudinal bone growth?
- bone growth starts as the formation of a bony collar around the cartilage template
What is the second stage of longitudinal bone growth?
Blood vessels invade the tissue
What is the third (middle) stage of longitudinal bone growth?
Osteoblasts enter the cartilage shaft and lay down bone matrix
What is the fourth (2nd to last) stage of longitudinal bone growth?
Osteoblasts enter epiphysis and lay down bone matrix.
What is the last (5th) stage of longitudinal bone growth?
Cartilage is retained between the epiphysis and the shaft.
What are the two types of bone growth?
Interstitial Growth
Appositional Growth
What is interstitial bone growth?
Largening of the bone longitudinally
Growth from within the cartilage
Division of chondroblasts
Replicate and enlarge - allowing lengthening of the cartilage template
What is Appositional growth?
Thickening of the bone
Surface cells differentiate - growing into perichondrium –> dense fibrous connective tissue
What is longitudinal bone growth?
Indirect growth via interstitial cartilage growth at the growth plate and ossification
Ends at skeletal maturity
What is circumferential bone growth?
Occurs directly via appositional growth at the bone surface
Continues throughout life
What are the steps in the process of longitudinal bone growth?
Bone growth starts at formation of bony collar around cartilage template
Blood vessels invade tissue
Osteoblasts enter cartilage shaft, lay down bone matrix
Osteoblasts enter epiphysis and lay down bone matrix
Cartilage is retained between epiphysis and shaft
What is the epiphyseal growth plate?
Site of indirect bone growth via interstitial cartilage growth
Increase in bone length complete at skeletal maturity when the growth plate “closes” and interstitial cartilage growth stops
What does endochondral (bone formation) mean?
Within cartilage
What does intramembranous (bone growth) mean?
Inside a membrane
How does skeletal muscle growth occur?
Achieved through upregulation of protein synthesis within muscle cells
Result of hypertrophy rather than hyperplasia
= Increase in muscle mass
What is the main hormone involved in growth in the musculoskeletal system?
Growth Hormone (GH)
What are the functions of growth hormone?
Acts on liver to release insulin like growth factor 1 (IGF-1)
Where is growth factor produced?
Produced at anterior pituitary gland
What does IGF-1 act on and do?
Acts on:
- bone and cartilage –> increasing longitudinal growth
- muscle –> increasing muscle mass
- Increases conversion of carbohydrates into proteins
- Increases uptake of amino acids to be used in protein synthesis
What happens when there is a deficiency in growth hormone?
Leads to a shortened stature and decrease in growth.
What happens when there is excess growth hormone?
= gigantism
When is gigantism caused and what are the impacts?
= Onset of excess GH. Before closure of epiphysis
- Tall stature
- Long extremities
- Delayed puberty
When is acromegaly caused and what are the impacts?
= Onset of excess GH. After closure of epiphysis
- Height unaffected
- Gonads unaffected
- Altered facial characteristics
What is the function of Parathyroid Hormone (PTH) ?
Regulates the distribution of calcium and phosphorus in the body.
Increasing osteoclast activity - cells that break down bone
Decreasing osteoblast activity
What happens when there is too much parathyroid hormone in the body?
Increased Ca and P loss from bone = weakening bone
Increase chance of kidney stones and osteoporosis.
What happens when there is too little parathyroid hormone in the body?
Decreased Ca in the plasma
Muscular rigidity
Muscular spasm
What is the function of vitamin D in the body?
Works with parathyroid hormone to release calcium from the bone
Stimulates absorption of Ca and P in the GI tract
Deficiency = rickets
What is the function of calcitonin in the body?
Opposes parathyroid hormone - reduces calcium in the plasma
Inhibits osteoclast activity - calcium can be absorbed into the skeleton
What is the function of vitamin C in the body?
Important co-factor for many enzymatic reactions
Involved in collagen synthesis
Collagen = vital component of muscle, bone and cartilage
Deficiency = scurvy
What is the function of oestrogen in the body?
Reduces bone resorption
Stimulated bone development
What is the function of testosterone in the body?
Reduced bone resorption
Stimulates bone development
Stimulates muscle mass increase
Impacts of osteoblasts on bone loss?
Decreased apoptosis
Decreased oxidative stress
Increased maintenance of bone formation
–> Bone loss
Impacts of osteoclast on bone loss?
Increased apoptosis
Decreased bone resorption
- bone loss
What are 5 performance enhancing drugs?
- Erythropoietins (EPO) and agents affecting erythropoiesis
- Anabolic androgenic steroids (AAS) - Testosterone
- Peptide hormones and releasing factors - GH
- Growth factors and growth factor modulators - (IGF-1, VEGF)
- Hormone and metabolic modulator - anti-oestrogens
How does exercise affect bone?
Exercise changes the mechanical environment of the skeleton
Triggers cellular response and changes in bone architecture
Bones adjust size and shape in response
What is wolfs law?
*Optimisation of bone strength with respect to bone mass
* Alignment of trabeculae with principle stress direction
* Self regulation of bone cells responding to mechanical stimulus
How does increased mechanical loading result in increased bone strength?
- increased mineralisation
- decreased porosity
- increased bone mass
e.g. athletes
How does decreased mechanical loading result in decreased bone strength?
- decreased mineralisation
- increased porosity
- increased bone mass
e.g astronaughts
e.g teeth removed = lack of loading = bone restrictions
What are all synovial joints made up of?
- Articular cartilage
- Fluid filled synovial cavity
- Joint capsule
–> outer fibrous membrane
–> inner synovial membrane
What are some synovial joints made up of?
Articular discs or menisci
Articular fat pads
Tendons
Accessory ligaments (extracapsular and intracapsular)
Bursae
What is the structure of articular cartilage?
Has a smooth, slippery surface
Transmission of loads with little friction
Devoid of blood vessels, lymphatics and nerves.
What is osteoarthritis?
Progressive joint degeneration of articular cartilage and bone
Joint pain only present when bone is damaged
What is sarcopenia?
Age related loss of skeletal muscle mass and a decline in strength.
A decrease in size and quality of muscle.
More than twice as fast in the lower limb than the upper limb
Presence >50% in >80 yr olds
What impact can posture have on bone degeneration?
The vertebral column adjusts throughout development. Its shape is influenced by supporting the head and bipedal walking.
In old age Kyphosis can occur –> degeneration of intervertebral disks, osteoporosis in vertebrae, lengthening of extensor muscles
