Osteology (2)

Question 1

Long bone

Answer 1

3 main regions

Epiphysis- rounded end proximal and distal

Metaphysis- wide part between the epiphysis and narrow diaphysis part of the growth plate grows during childhood

Diaphysis-shaft

Question 2

Blood supply long bone

Answer 2

1. Nutrient artery - enters shaft via nutrient foramen and enters medullary cavity where it divides into ascending and descending branches near epiphysis it joins with epipyseal and metaphyseal arteries and this is how the nutrient artery nurisous the whole medulla cavity, inner 2/3 of cortex and helps nourish metaphysis
2. Epiphyseal artery- enters in between articular cartilage and growth plates cartilage
3. Metaphyseal artery- enters metaphysis
4. Periosteal artery- form an extensive network of vessles which cover the entire external surface of the shaft small arteries enter cortex through small channels and supply the outer 1/3 of the cortex

Blood supply of the immature bones is similar but epiphysis and metaphysis are separate vascular areas and have little or no connections between them until ossification of growth plates occurs in teens

Question 3

Microscopic structure of bone

Periosteum

Answer 3

Periosteum– outer connective tissue membrane of bone

Outer Fibrous layer (fribroblasts muscles tendons ligaments)

Inner osteogenic layer progenitor cells similar to stem cells= specialised bone cells chondroplasts or osteoblasts for fracture healing

Innovative = has a nerve supply and capable of generating pain

Question 4

Outer circumferential lamella

Answer 4

Deep to periosteum

Layered like an onion - compact bone layered Circumferentially

Question 5

Compact bone functional unit = Haversian systems

Answer 5

Arranged in Haversian systems (functional unit of compact bone) arranged in parallel to long axis of the bone. +interstitial lamella

Each haversian system consists of concentric layers of lamelle or compact bone tissue that surround the central canal - haversion canal- lined with endosteal membrane

Longitudinal small pore system

Central canal lined by endosteal membrane

Question 6

Vulkmans canal

Answer 6

Vulkmans canals lie at right angles to the long axis of the bone and connect blood and nerve supply of periosteum to central canal and medulla cavity.

Question 7

Inner circumferential lamelle

Answer 7

Separates haversion systems from and endosteum and medulla cavity

Question 8

Endosteum

Answer 8

Endosteum-lines medullary cavity of long bone soft and thin Connective tissue contains osteoprogenitin cells = healing fractures

Question 9

Medullary cavity

Answer 9

Centre of long bones

Children – contains red bone marrow-blood cells

Adults – contains yellow fatty marrow and cancellous bone

Question 10

Cancellous bone

Trabecular/spongy bone

Answer 10

Mature bone

Inner layer

Lamelle arranged in an irregular lattice of thin collums = trabecular

Delicate branching layers of bone with a sponge like appearance

Trabecular cavities= occur along the lines of stress filled with red marrow lined with endosteum

Less dense than compact bone present mainly in ends of bones to distribute weight across joints

Highly vascular- red bone marrow

Question 11

Compact

cortial

Answer 11

Thicker in shaft to resist bending and rotational forces

No visible spaces/hollows more dense and strong providing protection and support and resists stress from weight transmission

Consists of parallel sheets bone

Has concentric rings of lamelle for harevision systems

Question 12

Woven bone

Answer 12

Immature bone laid down in haphazard arrangement collagen fibres

Occurs when osteoblasts (bone producing cells) produce osteoid rapidly (bone like tissue before it has ossified)

embryos- replaces by compact bone in 3rd trimester

fracture healing processes- replaced compact bone

Mechanically weak

Question 13

Histology of bone

Answer 13

Bone= Extracellular a bone matrix, inorganic mineral salts, bone cells

Question 14

Extracellular bone matrix

Answer 14

Extracellular bone matrix
25% water

type one collagen (90–95%)

protein gel (proteoglycan)
other proteins- (osteonectin and osteocalcin bind bone mineral and calcium)

Provides scaffold for separated cells

In compact bone alternating arrangements of Collagen fibres, fibres in each layer are parallel to each other but at right angles to fibres in alternating layers= torsional forces but better at resisting compressible forces

Question 15

Inorganic mineral salts

Answer 15

50%=hydroxyapatite =calcium and phosphate complex which is deposited along Collagen strands and gives bone it’s rigidity

Question 16

Bone cells

Answer 16

Osteoblasts - produce new bone

Osteocytes- maintain the bone (mature bone cells) osteoblasts become trapped in the matrix= osteocytes
Reduced ability to synthesis bone
Routine turn over of matrix

Osteoclasts- Remove bone tissue- reabsorb bone

Osteoprigenerator cells- periosteum and endosteum- mature to osteoblasts Differentiate into osteoblasts when required I.e fracture

Question 17

Bone growth

Answer 17

Osteoblasts produce new bone cells and then to prevent them getting too big osteoclasts remove bone

Question 18

Ossification is the process of producing new bone. It occurs via one of two mechanisms:

Answer 18

1)Endochondral ossification -€“ Where hyaline cartilage is replaced by osteoblasts secreting osteoid.

The femur is an example of a bone that undergoes endochondral ossification.

2) Intramembranous ossification -€“ Where mesenchymal (embryonic) tissue is condensed into bone.

This type of ossification forms flat bones such as the temporal bone and the scapula.

In both mechanisms, primary bone is initially produced. It is later replaced by mature secondary bone.

Question 19

Where are Osteocytes located

Answer 19

Osteocytes are located between the lamellae, within small cavities (known as lacunae). The lacunae are interconnected by a series of interconnecting tunnels, called canaliculi.

Question 20

Mature bone cells

Answer 20

Osteocytes in lacunae make contact with Cytoplasmic processes by a network small transverse canals - Provides many routes for nutrients and oxygen to reach osteocytes and removal of waste products