muscles

Question 1

What is the double meaning of bone

Answer 1

Bone is an organ, and organs are made up of different types of tissues

Bone can also mean the tissue, and one of the tissues found in the bones of the skeleton

Question 2

What are the 6 functions of the skeletal system

Answer 2

1) Support,
2) Protection
3) Movement
4) Calcium and phosphorus reserve
5) Haemopoiesis
6) Fat storage

Question 3

Axial skeleton

Answer 3

80 bones
(some are paired)
It has an emphasis on support/protection and haemopoiesis

Question 4

Appendicular skeleton

Answer 4

126 paired bones

Movement
Fat storage

Question 5

Endosteum

Answer 5

thin, inner fibro-cellular layer lining medullary cavity

Question 6

Periosteum

Answer 6

Outer fibro-cellular sheath surrounding the bone

Question 7

What is the extracellular matrix made of

Answer 7

Fibres (the organic component)
Ground substance (the inorganic component)

Question 8

What are the fibres in bone and give their precise function

Answer 8

Fibres resists tension/stretching and pulling

The ones in bone are Type I and V

Question 9

Ground substance in bone and function

Answer 9

Resists compression

squeezing/crushing

Question 10

Osteogenic cells

Answer 10

surface of bone in the periosteum and endosteum

Also found in the central canals of compact bone.

It normall is dormant but can divide and supply developing bone with bone forming cells

Question 11

Osteoblast

Answer 11

Usually in a layer, under the peri or endosteum wherever new bone is being formed

it is needed for the synthesis, deposition and calcification of the osteoid

Question 12

Osteoid

Answer 12

The organic extracellular matrix of bone, synthesised by osteoblasts prior to mineral deposition

Question 13

What is osteoid primarily made of

Answer 13

it’s 70% collagen with the remainder consisting of proteoglycans, other proteins and water

This precursor matrix is eventually infiltrated with bone salts (hydroxyapatite) and this process is called calcification

Question 14

What is the significance of the osteoid calcification

Answer 14

It prevents nutritive fluids from diffusing freely through it

Question 15

Osteocyte

Answer 15

Trapped within the lacunae inside of bone.
Osteocytes can communicate with neighboring cells through their long cellular processes inside canaliculi

they are required for
Bone tissue maintenance
they contibute to lattice inside the bone

responsible for localised minor repair

Rapid Calcium exchange

Question 16

An Osteoclast is a syncytium

A fusion of monocyte progenitor cells

Answer 16

They are found at sites where bone resorption is occuring

and secrete acid and enzymes, dissolves the mineral and organic components of bone

Question 17

How does the bone grow

Answer 17

Appositional growth+resorption

Collectively called bone remodelling.

Question 18

Why can’t the bone grow via interstitial growth

Answer 18

Because Bone is too rigid.

Interstitial growth involves cells dividing inside the tissue, secreting more Ecm AND GROWING THE TISSUE FROM WITHIN

Bones also can’t do that because bone i is designed to resist deformation, so it can only grow by adding new bone onto an existing surface

Question 19

Endochondral ossification

Answer 19

Ossification: Plate of hyaline cartilage (epiphyseal plate) which undergoes interstitial growth. As plate grows thicker, cartilage near the
metaphysis dies. This provides the framework for new bone to grow into, through the process of osteoblasts putting down new bone. As you reach the
age of 16-19, the rate of cartilage death exceeds rate of hyaline cartilage growth, and the metaphysis catches up. It becomes in contact with the epiphysis
and fuses forming the epiphyseal line. This determines your height.

Question 20

How are secondary osteon formed

Answer 20

1) Osteoclasts form and gather in an area that needs to be remodelled. This group of osteoclasts starts boring its way through the existing bone. This area is called the “cutting cone, and creates a tunnel inside the existing bone. This is how secondary osteons differ to primary osteons. In primary osteons the tunnel is created on the surface of a bone as it grows.”

After the tunnel has been created, osteoblasts mve in and line the tunnel wall. They form the new active endosteum and start depositing osteoid onto the walls of the tunnel. The osteoid layer is then calcified, forming new lamella. A blood vessel will grow into the newly formed tunnel to supply the cells

Osteoblasts deposit layer upon layer of new concentric lamellae onto the walls of the tunnel, slowly filling it in. This active area behind the cutting cone is called the closing cone. Some of the osteoblasts are trapped in the newly deposited lamellar bone and become osteocytes

Eventually the tunnel is reduced to the size of a typical haversian canal. The remaining osteoblasts lining the Haversian canal either die or become bone lining cells and contribute to the resting endosteum. A new osteon is now formed. Sometimes a line can be seen at the junction between the outermost lamella of the new osteon and the pre-existing older bone-called the cement line