3.5 Bone Structure

Question 1

What is the axial skeleton

Answer 1

The bones along the body’s lengthways axis such as the skull, vertebral column and rib cage

Question 2

What is the appendicular skeleton

Answer 2

The bones attached to the axial skeleton such as limbs and girdles

Question 3

What are the 5 bone shape classifications

Answer 3

-flat
-long
-short
-irregular
-sesamoid

Question 4

What are the functions of flat bone

Answer 4

-to protect internal organs
-points of attachment for muscles

Question 5

What is the structure of flat bone

Answer 5

It is thin and curved. It has a layer of spongey bone lined on either side by layers of compact bone

Question 6

Give some examples of flat bone

Answer 6

sternum
ribs
cranial bones

Question 7

What is the function of long bone

Answer 7

To provide leverage

Question 8

What are the 3 areas of long bone

Answer 8

diaphysis
epiphysis
metaphysis

Question 9

What is the diaphysis in long bone?

Answer 9

A tubular shaft running between the proximal and distal ends of the bone with a medullary cavity in it containing yellow marrow. The diaphysis wall is made of compact bone

Question 10

What is the epiphysis in long bone

Answer 10

The wider section at the each end of the bone made of spongy bone.

Question 11

What is the metaphysis in long bone

Answer 11

Where the diaphysis and epiphysis meet. It has the epiphyseal (growth) plate

Question 12

What is the endosteum

Answer 12

The membranous lining of the medullar cavity. Its involved in bone growth, repair and remodelling

Question 13

What is the periosteum

Answer 13

The fibrous membrane covering the outer surface of the bone. It is rich in blood vessels, lymphatic vessels and nerves.

Question 14

What are long bone fossa

Answer 14

The point of attachment for muscles, ligaments, tendons or joints

Question 15

Describe how bone is vascularised

Answer 15

Blood enters through the nutrient foramen in the periosteum and nourishes the spongy bone and marrow cavities. The blood then exits through other foramen.

Question 16

What else follows the same foramen pathway as blood in bone

Answer 16

Nerves

Question 17

What are the two components of bone matrix and what are their proportions

Answer 17

-35% organic portion (made of collagen fibres and proteoglycans)
-65% inorganic portion (made of calcium and phosphate salts)

Question 18

What are the functions of the organic and inorganic parts of bone matrix

Answer 18

-inorganic part gives strength
-organic part gives flexibility

Question 19

What can deficiencies in the organic and inorganic parts of bone matrix give you

Answer 19

inorganic defficiency - rickets
organic deficiency - brittle bones

Question 20

What are osteogenic cells (aka osteoprogenitors)

Answer 20

The only bone cells that divide. Immature osteogenic cells are found in the periosteum and marrow. Osteogenic cells differentiate into osteoblasts.

Question 21

What are osteoblasts

Answer 21

The primary bone forming cells, synthesising and secreting the collagen matrix and calcium salts

Question 22

How are osteocytes formed

Answer 22

As osteoblasts secrete bone matrix, they get trapped in it which changes their structure to osteocytes

Question 23

What are osteocytes

Answer 23

The primary cell of mature bone. they maintain the mineral concentration of the matrix via secreting enzymes and responding to mechanical strain.

Question 24

How are osteocytes connected

Answer 24

They are interconnected by long cytoplasmic processes that extend through canaliculi channels to form a network.

Question 25

What are osteoclasts

Answer 25

Multinucleated phagocytic cells that come from monocytes and macrophages (and their production is regulated by cytokines and sex hormones). They remove bone tissue

Question 26

Why is the balance of osteoclasts and osteoblasts important

Answer 26

So there can be rapid release and rapid reabsorption of calcium ions

Question 27

Describe the 2 classifications of bone according to the organisation of the collagen fibres in the matrix

Answer 27

Woven bone: The collagen fibres are randomly distributed. Is formed for foetal development and for bone fracture repair Lamellar bone: Collagen fibres are organised in parallel and perpendicular lamella. Osteocytes are found in the lacuna between the lamella. Mature bone is lamellar.

Question 28

What are 2 classifications of bone according to the amount of space in the bone matrix

Answer 28

-compact (aka cortical) bone -spongy (aka cancellous or trabecular) bone

Question 29

What is compact bone

Answer 29

Dense and vascular, mostly found on outside of the bone. Its basic unit is an osteon. Its defined as 80-90% of the bone volume being mineralised. Most bone in the body is compact

Question 30

What is spongy bone

Answer 30

It is made of interconnecting trabeculae (groups of lamallae) which provide strength despite its light weight. In between the trabeculae are spaces with bone marrow, osteocytes and blood vessels. The trabecular surface is covered with a single layer of cells.