Lecture 7 Flashcards
What does bone start as? What process changes this and what centers for this are there?
Bone begins as a cartilage model, the process of transforming this cartilage into bone is known as ossification. The centers for this are the primary center of ossification (where the bone first starts ossifying) in the diaphysis (shaft), the secondary centers (where bone starts to ossify after the primary center has already started of ossification are in the epiphysis (extremities).
What is found between the centers of ossification? What is it formed of and when will this be gone?
Between the two centers of ossification are growth plates/epiphyseal plates. These are formed of cartilage and will not be present in fully grown bones.
What do the X-rays of younger children look like? why?
It looks as if the bones aren’t joined, this is because the cartilage is about half as dense as bone and as such doesn’t show up well on x-rays.
How is growth of bone achieved?
Growth in length is done by ossifying the growth plate (which can lengthen as an individual grows, allowing for more bone growth). Growth in width/moulding is done by osteoblasts at the periosteum secreting bone matrix to increase the width while osteoclasts at the endosteum (an inner layer of the bone which lines the medullary cavity) take up more bone matrix, leading to an increase in size of the medullary cavity and bone width.
What is the medullary cavity?
The central cavity of bone shafts.
What two types of marrow are there, what do they do and where are they mainly found?
Red marrow: found primarily in the red marrow cavities in the epiphysis, functions to produce red blood cells, platelets and white blood cells.
Yellow marrow, found primarily in the shaft of bones, (medullary cavity) and functions primarily as fat storage.
What is osteoporosis and what changes occur as a result in the two bone types? What are the risk factors?
Osteoporosis is when osteoclasts overtake the osteoblasts, leading to more bone being taken up than bone secreted. In the compact bone this makes it more porous and thinner, in cancellous bone it leads to loss of volume (less trabeculae). This makes fractures in both bone types easier and leads to compression fractures of the vertebrae, (causing a slouched back posture with a hunched forward neck.
Risk factors include loss of oestrogen (making postmenopausal women heavily at risk), lack of exercise, nutritional factors and the peak bone mass of an individual (higher is worse).
What stages occur in fractures repair?
Stage 1: a haemotoma is formed (swelling of clotted blood) from blood from the capillaries and phagocytes come in to clean up any present pathogens.
Stage 2: Fibroblasts come in and turn into chondroblasts which will form a fibrocartilaginous callus (procallus, soft callus) and new blood vessels will form.
Stage 3: Osteoblasts replace the fibrocartilaginous callus with a bony callus.
Stage 4: the bone is fixed but the bony callus is unorganised and as such must be remodelled into correct shape.
This whole process can take months to complete fully.
What is pseudoarthrosis?
Pseudarthrosis is a bone fracture that has no chance of mending without intervention. In pseudarthrosis the body perceives bone fragments as separate bones and does not attempt to unite them. If this is then repaired it will lead to a false joint.
What are the three main types of fractures?
Closed/simple: The bone has been minimally displaced and the bone hasn’t injured soft tissue (bone isn’t sticking out). Open/compound fracture: large amount of displacement, usually penetrates the skin and has a large chance of infection.
Greenstick fracture: a fracture of the bone, occurring typically in children, in which one side of the bone is broken and the other only bent.
