Bone and Joint Physiology Flashcards
List the 5 functions of bone
- Supports the body
- Facilitates movement
- Produces RBCs (haematopoeisis)
- Regulates calcium
- Protects organs
What conditions result from low Vitamin D
- Rickets
2. Osteomalacia
Where is Vitamin D converted to its active form
- Liver
2. Kidney
Where is parathyroid hormone produced
Chief cells of the parathyroid
What is the effect of PTH on bone
Causes bone resorption by osteoclasts
Where is Calcitonin produced
Parafollicular C-cells of the Thyroid
How does growth hormone cause bone growth
- GH stimulates the production of IGF-1 in the liver
2. IGF-1 stimulates bone growth
Why is magnesium essential for bone health
Important in hydroxyapatite crystallisation
What process increases bone length
Endochondral ossification
What process increases bone width
Subperiosteal appositional ossification
How is the bone matrix divided
- Organic (35%)
2. Inorganic (65%)
What is the main component of the inorganic matrix
Calcium hydroxyapatite (contains 99% of the body’s calcium and 85% of body phosphorus)
What is the main component of the organic matrix
Bone proteins - namely Type 1 collagen
What are the two ways in which osteoblasts lay down collagen
- Random weave (woven bone)
2. Orderly layers (lamellar bone)
From where are osteoprogenitor cells derived
Pluripotential mesenchymal stem cells
Where are osteoblasts derived
Osteoprogenitor cells
Where are osteocytes derived
Osteoblasts
Where are osteoclasts derived
Haematopoietic progenitor cells
Where are osteoclasts located
Sites of active bone resorption in pits called Howship’s lacunae
What is woven bone and where is it found
Immature bone - seen in the fetal skeleton, growth plates and callus
What is cortical bone
- Rigid with no marrow
- Well-defined haversian canals lying parallel to the long axis
What is cancellous bone
- Lies inside the cortical layer
- Contains marrow in spaces between trabeculae
- No blood vessels
What connects periosteum to the underlying bone
Sharpey’s fibres
What are the two layers of periosteum
- Cambrial (inner)
2. Fibrous (outer)
What are the 3 functions of periosteum
- Anchor - site of tendon/ligament attachment
- Source of Osteoprogenitor cells
- Nutrition
What are the two ways in which a bone may ossify during development
- Directly - intermembranous - e.g. clavicle
2. Endochondral ossification of a hyaline cartilage template - e.g. long bones
How may a long bone be divided
- Diaphysis (shaft) - tube of cortical bone
- Metaphysis - conical area of cancellous bone facilitating load transfer from the articular surface to the diaphysis
- Physis - growth plate
- Epiphysis - articular surface and consists of zone of cancellous bone
Where are the primary and secondary ossification centres of long bones
- Primary = diaphysis
2. Secondary = epiphysis
What are the 4 zones of the physis (growth plate)
- Resting zone
- Proliferative zone
- Hypertrophic zone
- Zone of provisional calcification
Which zone of the growth plate are the chondrocytes dividing
Proliferative zone
Between which zones of the growth plate do fractures typically occur
Between hypertrophic and calcific zones
Define Wolff’s law
Trabeculae are formed in response to the loads placed on the bone
What percentage of cardiac output is distributed to the bone
5-10%
Which artery typically supplies the bone marrow and trabecular bone
Nutrient artery
Describe the circulus vasculosus
Arterial plexus surrounding the epiphysis derived from regional arterial branches
Describe the venous drainage of bones
Venous flow is from the cortical capillaries draining into sinusoids and then to the emissary venous system
What are the 3 classes of joint based on function
- Immovable (synarthroses) e.g. skull suture
- Slightly movable (amphiarthrosis) e.g. manubriosternal
- Freely movable (diarthroses)
What are the 3 classes of joint based on structure
- Fibrous
- Cartilaginous
- Synovial
What is a fibrous joint
- Lacks a joint cavity
- Fibrous tissue unites bone
What are the 3 types of fibrous joint
- Sutures
- Syndesmosis
- Gomphosis
What is an example of a gomphosis joint
Roots of teeth in alveolar socket
What are the two types of cartilaginous joint
- Primary (synchondrosis) - where bone and hyaline cartilage meet e.g. between rib and costal cartilage
- Secondary (symphysis) - where hyaline covered articular surface of two bones are united by fibrous tissue e.g, intervertebral joints
What type of collagen is found Hyaline cartilage
Mainly Type 2
