Bone growth - Joint, Tissues and structures Flashcards
How did all bones begin?
As a cartilaginous model in the womb
At 10 weeks in utero, you find…
Future hip bones and primary ossification centres in the femur
At 16 weeks in utero, you find…
Flat bones of the skull and long bones of limbs
When does the cartilage model begin to develop?
At 6 weeks
Process of cartilage into bone
intermembranous and endochondral ossification
What happens when ossification starts?
The cells inside the cartilage expand and precipitate Calcium. Chondrocytes die and leave cavities
Blood vessels proliferate around outside of cartilage and bring osteogenic cells –> osteoblasts and then they lay down bone tissue i.e organic and inorganic. This process repeats when vessels penetrate the cartilage and lay down cells inside.
More bone formed in the centre –> diaphysis. It is the 1º ossification centre i.e formed first
Do babies have tarsals
Nope, not until later, otherwise its just cartilage
How are epiphyses created?
Same process as the diaphyses but later
The plate that divides the diaphyses and epiphyses is the epipheseal plate (cartilage, growth). Allows growth to happen in the epiphyses and diaphyses, especially in linear growth of diaphyses
Osteoblasts converts cartilage into bone until after peak bone growth is reached
How does Linear bone growth in the diaphyses happen?
Chondrocytes at the superior epipheseal side divide and expand to produce more cartilage.
Chondrocytes at the diapheseal side degenerate and break down
The osteoblasts at the diapheseal side migrates upwards into cartilage and lays down new bone tissue
INTERSTITAL GROWTH
When does the sternal clavicle cartilage change?
30s
When does the sacrum cartilage turn into bone
mid 20s
What is a joint?
Articulation, where bone meets bone. It is surrounded by other soft tissue to support, stabilise or make more mobile
Do joints have inorganic materials?
No
Key thing about joint soft tissues
There are different structures depending on the function
Cartilage
Cartilage found in the articulations of joints
Hyaline, also bone model
Fibrocartilage
Have small cellular component with ECM
- Gel like fluid ground substance
- Chondrocytes in lacunae
Hyaline
Lot of gel like fluid and less collagen structures
* More H2O to resist compression and *provide a smooth surface to prevent friction between bones
It degrades with age as it loses its H2O content over time, friction between bones
How does Cartilage get nutrients?
They are avascular and get their nutrients through joint loading i.e pressure put on joints causing diffusion of nutrients through fluid (loading up the fluid with mats).
Fibrocartilage
Collagen forms thicker bundles and lines in the direction of the stresses
resisting tension and sharing stress
Not as fluid rich as Hyaline so not as good as resisting comepression. They are found where you need to resist both compression and tension eg. Knee
What does meniscus do?
Made of fibrocartilage, Deepen articular surface, cups that hold ends of femur and acts as a shock absorber. It distributes the force over a larger area rather than just a point when two bones meet
What are ligaments and tendons made of?
DFCT, made of fibrocytes from fibroblasts
What are cartilage cells?
Chondrocytes
DFCT
Cellular component of Fibrocytes
ECM is made of thick protein bundles with collagen and some elastin
Less fluid and cant resist a lot of compression but can resist a lot of tension
Lined in the orientation of stress
Somewhat vascular.
What is a ligament?
Bone to bone
- Prevents bone from moving laterally (medial prevents this)/medially (lateral lig)
-stressed parents - recoils bone back with little elastin but mostly collagen
What is a tendon?
Bone to muscle to move bones.
- Has more movement and enable movement, pull at collagen fibres and respose is quick.
- Muscle signal travels through tendons thick bundles to pull at bone for movement
What is Bony congruence?
How much bone touches other bone, structure of soft tissues around joints depends on this
- More congruence = more stability
Tissues vs Structures
Tissues made of specialised cells
Structures made from tissues
3 types of joints
- Fibrous
- Cartilaginous
- Synovial
Fibrous joints
- DO NOT ALLOW MOVEMENT and give stability
- Tissue is DFCT
- Structure is a ligament
- Found at sutures
- Distal tibiofibular joint
Cartlaginous joints
- Allow some movement
- Tissue is fibrocartilage, entirely cartilage
- Resists compression and tension
- In between bones (cartilaginous joints) eg intervertebral disc to absorb forces from twisting etc. Another eg. Pubic symphysis
Appositional bone growth
osteogenic cells in inner layer of periosteum –> daughter cells of osteoblasts add bone matrix to surface –> succesive circumferential lamellae –> osteoblasts in between lamallae become osteocytes
Perforating fibres
Collagen fibres from joint capsules,ligs and tendons attatch to circumferential lamallae through the osteoblasts in the cellular layer of periosteum.
What is endosteum?
- Incomplete lining found in the medullary cavity
- Covers trabeculae lining the central canals
- Surface is usually osteogenic cells that covers matrix, no cells matrix exposed
Why is the inner surface of the circumferential lamalle incomeplete?
Because of Osteoclasts that reside in osteoclastic crypts i.e shallow depressions
Intramembranous ossification bones called
Dermal/membrane bones as bone are created deep in dermis
Process of intramembranous
IN OSSIFICATION CENTRE
- Mesenchymal –> osteoblast –> bone matrix which then becomes one with Ca salts and forms bone
-Moves outward in struts called spicules that engulf some osteoblasts to be recruited to become osteocytes
-Blood vessels invade and as spicules join they capture them
- Plate of spongy bone around the blood vessels
- After process, the fibres around bone become outer layer od perio and the first layer of osteoblasts become the cellular layer
-Diploë
Amount of motion at a joint
Range Of Motion
