Biology Lecture Week 6 - Biological Materials Flashcards
Bone contains the following …
- 25-30% water
- Collagen (30% dry weight). Gives resistance to tensile loading, ductility (flexibility) and toughness (resistance to shock loading
- Minerals (about 70% of dry weight). Mainly calcium phosphate/carbonate. These resist compression, and provide rigidity
Bone is capable of withstanding loads …
Six times those experienced in normal life
Define what Osteocytes are …
A specialised form of connective tissue which are light, in a collagen matrix and packed with minerals
What are the two types of bone ?
- Cortical
- Trabecular
The combined strength to weight ratio is greater when combined than in the individual parts
Compressive and tensile forces act on bone, which type of bone is better at resisting these forces ?
Cortical bone as trabecular bone is much weaker in resisting either type of force
What are the different types of [fracture patterns] and their {load type} ?
1: [Diaphyseal impaction] - {Axial Compression}
2: [Transverse] - {Bending}
3: [Spiral] - {Torsion}
4: [Oblique transverse and butterfly] - {Axial compression and bending}
5: [Oblique] - {Axial Compression, bending, torsion}
Define a transverse fracture …
- Bending Load
- Cortical bone weaker in tension than compression so bone under tension fails first
- Failure mechanism is break propagation perpendicular to bone’s long axis, from surface layer inwards
Describe what Cartilage is …
- Cells are widely separated within a fibrous, organic matrix which may:
- appear (but isn’t) structureless as in rigid hyaline cartilage
- contain more connective tissue fibres in the matrix (eg. fibrocartilage)
What does Cartilage consist of (genetic make-up)
- Cells (chondrocytes) account for less than 10% of tissue volume
- the organic matrix consists of collagen fibrils (10-30% net weight) within a proteoglycans solution (3-10%) net weight
- Remainder of tissue (60-87% is made up of water, inorganic salts and small quantities of matrix proteins, glycoproteins and lipids
- its mechanical properties are dependant on the direction of loading (anisotropic)
what are Cartilage’s Biomechanical Properties
- Cartilage shows typical viscoelastic behaviour:
- loading leads to rapid initial deformation followed by more gradual increase
- returns to initial shape on load removal (hysteresis)
- prolonged standing causes creep of intervertebral discs (hence shortening of the body’s overall height
What leads to Articular Cartilage Injuries …
- Articular cartilage is capable of deformation; decreases stress on the joints by increasing load-bearing area
- Avascular and tends to have few nerve endings, meaning it shows little external symptoms and repairs poorly
- Overuse injuries cause cartilage to wear away, leading to osteoarthritis
- High impact loads lead to swelling of cartilage; if sever enough may fracture
What are Tendons ?
Tough cords of closely packed collagen fibres
What are Aponeuroses ?
Sheet like tendons
Attach muscles to bones and transmit tensile loads so that movement can occur
What are Deep facia ?
Occur between muscles, enveloping individual muscles and binding them in groups
What is Intermuscular Septa ?
Separates muscle groups passing from the deep fascia to the bone
