Bone Growth, Joints: tissues and structures Flashcards
When does the cartilage model form?
Roughly 6 weeks after fertilisation
What is endochondreal ossification?
The process of turning cartilage into bone
What is the primary ossification centre?
It is where ossification happens first. It is in the diaphysis (shaft) of the bone. In all bones this is the same, but they develop at different times.
What are the secondary ossification centres?
The epiphysis.
How do we get from the cartilage model to the primary ossification centre being established?
Start of calcification - blood vessels and osteoblasts external - blood vessels and osteoblasts internal - primary ossification centre developed
How does bone grow in length?
Enabled by the epiphyseal (growth) plates. Bit of bone formed on top and bottom of growth plates so it lengthens. It ossifies (disappears) when we reach adulthood.
What are epiphyseal plates?
Growth plates. They are formed by cartilage
How does the bone grow in width?
Osteoblast activity forms circumferential lamellae, while the osteoclasts mould bone shape and form medullary cavity so that the bone is widening but not becoming too heavy
What is the name for bone growth in width?
Appositional growth
How do we move?
Bones articulate and the joints
What is the role of a joint?
Holds bones together, involves bone ends, involves soft tissue, allows control of movement
What are the two key soft tissues in bones?
Cartilage and DFCT (dense fibrous connective tissue)
What are the sub categories of tissue for cartilage tissue?
Hyaline (articular) and Fibrocartilage
What are the sub categories of tissue for dense fibrous connective tissue?
Ligaments, Tendons, Joint Capsules
What are chondrocytes?
Found in the lacuna in cartilage. They are cartilage cells.
Collagen fibres from cartilage are embedded in what?
Ground substance
How does cartilage get nutrients?
They are diffused through the joint matrix by joint loading
What does the fact that cartilage is avascular mean?
That it gets not much blood flow and therefore not much access to nutrients.
What is hyaline (articular cartilage)?
Its function is to resist compression and it has a high water content in its matrix that helps do this. It has sparse collagen fibres.
What are the two types of cartilage in joints?
Hyaline (articular) and Fibrocartilage
What does hyaline (articular) cartilage do?
Moulds to surfaces of bones where they articulate and creates a smooth surface with results in frictionless movement.
What does the two names hyaline (articular) represent?
Hyaline is what it looks like.
Articular is what it does (creates the smooth surfaces).
What is the purpose of fibrocartilage?
Resists compression and tension. It has many collagen fibres to do this and they are arranged in bundles. The orientation of the fibres aligns with the stresses.
What does fibrocartilage do in the joint?
It is useful in joints that experience compression and tension, acting as a buffer/shock absorber. It distributes the force over a wider area and deepens articular surfaces.
What are the properties of DFCT (dense fibrous connective tissue)?
It is made of fibroblasts, collagen fibres and some elastin fibres. They are all tightly packed and the function is to resist tension. It also has little vascularity so it is slow to heal.
Ligaments connect what?
Bone to bone
Tendons connect what?
Muscle to bone
What is bony congruence?
How well bones fit together - The sum of bone surfaces that form an articulation
High bony congruence equals what?
A stable joint
Low bony congruence equals what?
A less stable joint (with more soft tissue to support it)
What are the joint classifications and how much movement do they allow?
Fibrous = least amount of movement
Cartilaginous = some movement
Synovial = lots of movement
What is a tissue?
cells grouped together in a highly organised manner according to specific structure and function. eg DFCT
What is structure?
Something formed of a tissue. eg ligament
Describe fibrous joints
Tissue = DCFT
Structure = ligament
Function = limit movement and provide stability
eg. cranial sutures
Describe cartilaginous joints
Tissue = fibrocartilage
Structure = varies
Function = some movement. The bones are connected entirely by fibrocartilage.
eg. intervertebral disk
Describe synovial joints
Tissues = many
Structures = many
Function = allows a lot of movement
eg. most joints in the appendicular skeleton
