The Skeleton - Bones And Joints (I)

Question 1

What are the functions of the skeleton

Answer 1

Support
Movement
Protection
Storage of mineral and ions (such as calcium and potassium)
Production of blood cells

Question 2

True or false: the skeleton is dead

Answer 2

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

Question 3

What are the name of the two types of bones

Answer 3

Compact bone and trabecular bone

Question 4

Down to its simple core, what is bone

Answer 4

Bone is collagen type 2 which gets calcified and mineralised

Question 5

How is collagen arranged in compact bone

Answer 5

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

Question 6

What is the advantage of compact bone

Answer 6

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

Question 7

What is the disadvantage of the compact bone

Answer 7

Its only strong in one direction. It can’t take heavy loads in different directions

Question 8

What are the other names of the trabecular bone

Answer 8

Spongy bone or cancellous bone

Question 9

How are the collagen fibres arranged in the trabecular bone

Answer 9

The arrangement of collagen fibres in the trabecular bone are in struts that are then cross-linked to provide strength.

Question 10

What is the advantage of trabecular bone

Answer 10

You can load it in all different directions and be able to cope with that (unlike compact bone)

Question 11

What is the disadvantage of the trabecular bone

Answer 11

It can’t take as heavy of a load than a compact bone

Question 12

Where is trabecular bone typically found?

Answer 12

Trabecular bone is typically found near joints as the bone needs to be loaded in different directions

Question 13

What is the name of the common bone found in your body

Answer 13

Long bone. It does not mean that they are very long. It only means it is longer then wider

Question 14

Give an example of a long bone

Answer 14

The phalanges (fingers and toes) are very tiny but are considered long bones because they are longer then wider

Question 15

Describe the structure of a long bone

Answer 15

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

Question 16

Define ossification

Answer 16

The formation of bone
Replacing other tissues with bone

Question 17

What are the two forms of ossification

Answer 17

Endochondral
Bone replaces existing cartilage model

Intramembranous
Bone develops directly from mesenchyme (fibrous connective tissue)

Question 18

What is the most common form of ossification

Answer 18

Endochondral ossification

Question 19

In which bones does intramembranous ossification take place

Answer 19

Scalp and clavicle

Question 20

Define endochondral ossification

Answer 20

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

Question 21

How many stages are there in the process of endochondral ossification?

Answer 21

Five stages

Question 22

Outline stage 1 of endochondral ossification

Answer 22

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

Question 23

Outline stage 2 of endochondral ossification

Answer 23

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)

Question 24

Outline stage 3 of endochondral ossification

Answer 24

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.

Question 25

Define stage 4 of endochondral ossification

Answer 25

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

Question 26

Define stage 5 of endochondral ossification

Answer 26

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

Question 27

What is the function of articular cartilage

Answer 27

Articulates with cartilage from another bone, prevents bone on bone articulations

Question 28

What is the function of the epiphyseal growth plate

Answer 28

Allows interstitial growth in the bone

Question 29

How is arthritis caused

Answer 29

In arthritis your articular cartilage is damaged and in extreme cases completely wears away

Question 30

What are the two ways by which cartilage grows?

Answer 30

Interstitial- growth from within (the epiphyseal growth plate)
Appositional growth - new layers of cartilage are added to the surface via the perichondrium