Bone & Biomechanics 3 Flashcards
What does bone start off as?
A cartilage model in the shape of the eventual bones is formed 6 weeks after fertilization
How is the cartilage transformed into bone?
Endochronal ossification
What is endochronal ossification?
Chemical signals cause the centre of the cartilage to become calcified. This continues to happen and blood vessels form outside the cartilage which brings osteoblasts that secrete bone matrix. The osteoblasts can make their way to the centre of the shaft to form the diaphysis of the bone.
What is the primary ossification centre?
Diaphyses
What is the secondary ossification centre?
Epiphyses
Do the epiphyses and diaphyses develop at the same time?
No. When the diaphyses is bone, the epiphyses may still be cartilage depending on which bone it is.
What separates the diaphyses and epiphyses?
Then epiphyseal plate
What is the epiphyseal plate made of?
Cartilage
What does the epiphyseal plate allow?
Growth of the bone in length
What is the maintaining cells of cartilage?
Chondrocytes
How do bones grow in length?
The chondrocytes at the epiphyseal side of the cartilage continue to grow while on the diaphyses side they degenerate. Osteoblasts in the diaphysis can then move upwards and so cartilage is replaced by bone until eventually the whole growth plate disappears.
Why must bones grow in width and length?
For strength
What is the purpose of joints?
To hold bones together and allow for movement and control of movement
What is an articulation?
Where two or more bones meet
What is involved in a joint?
Bone shapes and soft tissue which holds everything together
What soft tissues are found at joints?
Cartilage, ligaments, muscles and tendons. Depends on the type of joint though
Why are soft tissues soft?
Because they have no inorganic (mineral) component
What is the structure of cartilage?
Collagen fibres are found in the ground substance along with water and some proteins. The maintaining chondrocyte cells are found in lacunae.
What is joint loading?
When pressure is put on a joint and the nutrients diffuse through the soft tissue matrix to reach the chondrocytes as blood vessels don’t penetrate cartilage.
What are the two types of cartilage?
Hyaline cartilage and fibrocartilage
What is the structure of hyaline cartilage?
Collagen fibres which are barely visible in the matrix which has a high water content
What is the function of hyaline cartilage?
To resist compression and provide a smooth, frictionless surface
Where is hyaline cartilage found and why?
Hyaline cartilage moulds to the outer surface of bones to form a covering where they articulate. This allows for smooth, frictionless movement because cartilage is moving over cartilage.
What happens to hyaline cartilage as we get older?
It degrades which means bone ends up rubbing over bone and this results in joint degradation
What is the structure of fibrocartilage?
Bundles of collagen fibres found throughout the matrix
How are the collagen fibres arranged?
To align with the stresses
What is the function of fibrocartilage?
To resist compression and tension. This is done by deepening the articulation surface and acting as a shock absorber because force is spread over a wider area.
Where is fibrocartilage found?
At articulations which experience compression and tension
What are ligaments and tendons made of?
Dense Fibrous Connective Tissue, collagen, elastin and fibroblasts (cytes)
What is DFCT made of?
Dense Fibrous Connective Tissue is made of protein fibres closely packed together
What is the difference between collagen and elastin?
Elastin is more stretchy
What do tendons connect?
Muscle to bone
What is the function of tendons?
To facilitate and control movement. The contraction of muscles is transmitted to bone
What has more elastin present?
Tendons
What do ligaments connect?
Bone to bone
What is the function of ligaments?
To restrict movement away from themselves
What do lateral ligaments restrict?
Movement medially
What do medial ligaments restrict?
Movement laterally
What is found in ligaments?
Minimal elastin compared to collagen
What is bony congruence?
The amount of surface area of bone touching