The Skeleton - Bones And Joints (I) Flashcards
What are the functions of the skeleton
Support
Movement
Protection
Storage of mineral and ions (such as calcium and potassium)
Production of blood cells
True or false: the skeleton is dead
False
Common misconception is that the skeleton is dead or inert because the skeleton survives after tissue is broken down. Your skeleton is constantly changing - remodelled, broken down, being added to, getting bigger or smaller. The skeleton you have now is not the same skeleton you had 10 years ago
What are the name of the two types of bones
Compact bone and trabecular bone
Down to its simple core, what is bone
Bone is collagen type 2 which gets calcified and mineralised
How is collagen arranged in compact bone
The collagen arranges itself in these concentric circles which are around a canal called the Haversian Canal. These distinct concentric rings forming in the compact bone are known as osteons
What is the advantage of compact bone
It is very strong (due to how the collagen is arranged)
E.g. it takes roughly 50 times your body weight to pull apart the femur
What is the disadvantage of the compact bone
Its only strong in one direction. It can’t take heavy loads in different directions
What are the other names of the trabecular bone
Spongy bone or cancellous bone
How are the collagen fibres arranged in the trabecular bone
The arrangement of collagen fibres in the trabecular bone are in struts that are then cross-linked to provide strength.
What is the advantage of trabecular bone
You can load it in all different directions and be able to cope with that (unlike compact bone)
What is the disadvantage of the trabecular bone
It can’t take as heavy of a load than a compact bone
Where is trabecular bone typically found?
Trabecular bone is typically found near joints as the bone needs to be loaded in different directions
What is the name of the common bone found in your body
Long bone. It does not mean that they are very long. It only means it is longer then wider
Give an example of a long bone
The phalanges (fingers and toes) are very tiny but are considered long bones because they are longer then wider
Describe the structure of a long bone
The middle of the long bone is known as the diaphysis and surrounds the cavity called the medullary cavity (contains bone marrow where red blood cell production takes place).
The ends of the long bone are known as epiphyses (epiphysis is singular). You have a proximal epiphysis and distal epiphysis which are at the end of the bone that are connected to the diaphysis by the metaphyses
Define ossification
The formation of bone
Replacing other tissues with bone
What are the two forms of ossification
Endochondral
Bone replaces existing cartilage model
Intramembranous
Bone develops directly from mesenchyme (fibrous connective tissue)
What is the most common form of ossification
Endochondral ossification
In which bones does intramembranous ossification take place
Scalp and clavicle
Define endochondral ossification
Bone originates as a cartilage model
Cartilage is a flexible connective tissue found in many areas of the body (good at being loaded but not as good as bone)
Chondrocytes (chondro = cartilage, cytes= cells) are the only cells found in healthy cartilage. They produce and maintain the matrix (attracts water so watery cushion is formed) which consists of many collagen
How many stages are there in the process of endochondral ossification?
Five stages
Outline stage 1 of endochondral ossification
The chondrocytes begin to increase in size (hypertrophy) whilst the matrix calcified around them
These chondrocytes become starved and therefore die (undergo apoptosis - programmed cell death) as the chondrocytes rely on diffusion (especially in adult cartilage) of nutrients.
Calcified cartilage remains along with a structure known as the perichondrium (peri means side and chondrium means cartilage) so outer edge of cartilage
Outline stage 2 of endochondral ossification
Blood vessels grow into the perichondrium
Cells in the perichondrium differentiate into osteoblasts (bone forming cells) and begin forming bone around the edge of the cartilage shaft
This is now termed the periosteum (peri means beside and osteum means bone)
Outline stage 3 of endochondral ossification
Blood vessels and fibroblasts migrate into the cartilage. The fibroblasts differentiate into osteoblasts
The calcified cartilage matrix breaks down and is replaced by trabecular bone. The site where this first occurs is known as the primary ossification centre.
Define stage 4 of endochondral ossification
The wave of ossification spreads towards the ends of the long bone
Osteoclasts (bone resorbing cells) absorb bone from the centre leaving a marrow cavity
Bone grows inwards from the periosteum forming the compact bone surrounding the marrow cavity
Define stage 5 of endochondral ossification
Capillaries and osteoblasts migrate into the epiphyses and ossification begins
These areas are now known as secondary ossification centres
The timing of the appearance of second ossification centres varies greatly
What is the function of articular cartilage
Articulates with cartilage from another bone, prevents bone on bone articulations
What is the function of the epiphyseal growth plate
Allows interstitial growth in the bone
How is arthritis caused
In arthritis your articular cartilage is damaged and in extreme cases completely wears away
What are the two ways by which cartilage grows?
Interstitial- growth from within (the epiphyseal growth plate)
Appositional growth - new layers of cartilage are added to the surface via the perichondrium
