Building & Maintaining the Skeleton Flashcards
The head of the skeleton is derived from what, embryonically?
The neural crest
The body of the skeleton is derived from what, embryonically?
The mesoderm
All skeletal bones are formed in two ways. What are they called?
Endochondral ossification
Intramembraneous ossification
Which bones are formed by intramembraneous ossification?
Skull and clavicle
Which bones are formed by endochondral ossification?
All bones except skull and clavicle
Vertebrae develop from…?
Somites
What is a Hox gene?
A class of genes which control the body plan of an embryo along the cranio-caudal (head-tail) axis
When do limb buds develop?
At 4-5 weeks
The signalling within a developing limb bud from root to tip is controlled by?
The apical ectodermal ridge
The signalling within a developing limb bud from side to side is controlled by?
The zone of polarising activity
Endochondrial ossification uses what kind of models?
Cartilagenous models
Intramembraneous ossification uses what kind of models?
Membrane models
What are the four segments of the long bone?
Epiphysis
Physis
Metaphysis
Diaphysis
What is the Physis also known as?
Epiphyseal growth plate
Outline the process of endochondral ossification
- Cartilage is then invaded via blood vessels
- This proceeds to ossify, beginning at the diaphysis and spreading outwards
- This is roughly laid down bone, irregularly organised
- A second ossification occurs at the epiphysis again, under blood vessel influence
- The epiphysis also develops articular cartilage
- Between the epiphysis and diaphysis is the epiphyseal growth plate
- This expands and forms the metaphysis
What is the cell of cartilage?
Chondrocyte (derived from chondroblasts)
Why is damage to cartilage hard to heal?
It is avascular (no blood supply) and relies on diffusion
What are the three broad classes of joints?
Fibrous joints
Cartilagenous joints
Synovial joints
Within long bones, there are two distinct types of bones material - what are they and where are they located?
Outer shell: Cortex, compact bone
Inner shell: Semi hollow, trabecular bone
State the four stages of Bone Remodelling
Reactive Phase
Reparative Phase: Fibrocartilagenous Callus formation
Reparative Phase: Bony Callus formation
Bone remodelling
What happens during Osteoporosis?
Deposition and resorption is out of balance, giving rise to bone thinning and loss of mechanical energy
