Bone growth: Tissues of joints Flashcards
When we were a fetus, we did not have bones. Instead,
we had a skeleton made out of cartilage.
When does the cartilage model start
6 weeks after fertilisation
Endochondral ossification
The process of turning cartilage into bone
Primary ossification centre
The diaphysis (shaft) is the primary ossification centre, which means it is the first place that turns into bone. The epiphyses remain as cartilage.
Secondary ossification centres
After the shaft of the bone is slowly developing and gaining structure, the epiphyses will be the secondary ossification centre.
The epiphyses is separated from the diaphysis by
the epiphyseal/growth plate.
Explain the process of secondary ossification in the epiphyses
Blood vessels and osteoblasts will make way in the centre of the cartilage and start turning into bone tissue. It will do that until all of the space is filled up with bone tissue. It won’t turn all of the cartilage into bone yet.
Bone growth in length is enabled by
epiphyseal plates or growth plates.
Appositional growth is bone growth in
width
Explain the process of appositional bone growth
Osteoblast activity on the outside of the bone will produce circumferential lamellae, wrapping around the bone increasing it outwards to make it wider and wider. On the inside of the medullar cavity, osteoclasts break down the bone from the inside to hollow it out more to create a balance of growth without the bone being too heavy.
To create a balance of bone growth without making it too heavy,
osteoclasts mould bone shape and form medullary cavity
Functions of joints
-Hold bones together
-Involves bone ends
-Involves soft tissues to attach
-Allows control of movement
DFCT
Dense fiber connective tissue
Key soft tissues
Cartilage and dense fiber connective tissue
Three types of cartilage
Hyaline, elastric and fibrocartilage
Dense fibre connective tissue
- Ligaments
-Tendons
-Joint Capsules
Ground substance is made out of
sticky sugar components
Chondro meaning
Related to cartilage
Chondrocytes …
sit in the lacuna just like the osteocytes do in bone. They make the extracellular matrix of the cartilage. They release components in to the environment of the cell.
What kind of fibres are collagen fibres
Dense protein fibres
How are nutrients diffused through the matrix
Through a process called joint loading which is where at the end of the bones there is cartilage and next to it is fluid that has nutrients to it. Each time we move, it squishes the fluid into the cartilage and gives it the nutrients that it needs
Cartilage is a-….
avascular which means that there are no blood vessels present
Meaning of hyaline
Clear or transparent or see through
Function of the hyaline articular cartilage
Resist compression so when you push on it, it won’t crumble.
How does the hyaline articular cartilage resist compression
Because of its high water content in the matrix. Lots of water molecules that are trapped in the ground substance are fantastic at resisting compression.
Why do we have hyaline cartilage?
Every time we take a step, we are shifting our weight and putting more pressure on the ends of our bones. The bones will move against each other in a frictionless way and the hyaline cartilage allows it to happen. If we did not have this, the bones will wear down and the blood vessels and nerves in the bones will hurt.
Does the hyaline articular cartilage have collagen fibres
It has sparse collagen fibres in random places
Are there collagen fibres in fibrocartilage
There are many collagen fibres in bundles
Function of fibrocartilage
Resist compression and tension
Function of Ligaments
- Connect bone to bone
-Collagen and elastin resist tension and allow a little stretch and recoil
-Restrict movement away from themselves
What is the orientation of fibrocartilage
The orientation of fibres aligns with stresses
Why do we need fibrocartilage
Fibrocartilage is useful at joints that experience both compression and tension. They act as a buffer/shock absorber that distributes force over wider area. It also deepens articular surfaces
Qualities of DFCT
-Tightly packed
-Function is to resist tension
-Little vascularity
-slow to heal
Function of tendons
- Connect muscle to bone
- Less elastin than ligaments
-Facilitates and controls movement
-Contraction of muscles transmitted to bone
Bony congruence
Sum of bone surfaces that form an articulation.
if there is less congruence ,
more soft tissue support is needed
Fibrous joints
tissue structure and function
Tissue: Dense fibre connective tissue
Structure: Ligament
Function: Limit movement and provide stability
Three type of joints
Fibrous Cartilaginous Synovial
Example of fibrous joints
Cranial sutures and distal tibiofibular joint
Function of cranial suture
Stability for skull and protects brain
Examples of cartilaginous joints
Pubic symphysis and intervertebral disc
Cartilaginous joints
Bones are connected entirely by fibrocartilage
Cartilaginous joints
Tissue structure function
Tissue: Fibrocartilage
Structure: Varies
Function: Some movement
Function of distal tibiofibular joint
Stability for ankle and prevents unwanted movements
Synovial joints
Tissue function structure
Tissues: Many
Structures: Many
Function: Allow lots of movement
Example of synovial joints
Most joints in appendicular skeleton
