Lecture 15

Question 1

What bones form from endochondral and intramembranous ossification?

Answer 1

All form from endochondral except flat bones which are intramembranous

Question 2

Bone function?

Answer 2

Mechanical

Metabolic

Synthetic

Question 3

What is the difference between a spicule and trabeculae?

Answer 3

They are the same thing

Question 4

What type of growth is intramembranous?

Answer 4

Appositional at the periosteum to widen long bones

Question 5

How does intramembranous ossification work?

Answer 5

Cluster of mesochymal stem cells

Differentiate into osteoblasts which form spicules that expand into surrounding tissue

Spicules form trabeculae which form woven bone that traps blood vessels and spongey bone is formed

Spongey bone can be later converted to compact bone through remodelling

This growth is interstitial and widens bone by osteoclasts resorting bone at endosperm and this process occurring at periosteum.

Question 6

What do you find in the Haversian canal?

Answer 6

Artery, vein and nerve

Question 7

Immature vs mature bone?

Answer 7

Immature osteocytes are random whereas with mature they are in concentric lamellae.

Question 8

What lies on either side of compact bone?

Answer 8

A periosteum and endosteum

Question 9

Difference between spongey and compact bone?

Answer 9

Spongey bone has trabeculae with concentric lamellae within them and chondrocytes in between (see lecture). No blood supply as bone marrow present in between the woven bone.

Compact bone has osteons with concentric lamellae and chondrocytes in between. Blood vessels are required through Haversian canals as no space in between bone and no bone marrow.

Question 10

What determines bone remodelling?

Answer 10

Usage and stress lines. Being immobile reduces bone mass by a third

Question 11

Why are oestrogen and testosterone important for bones?

Answer 11

They stimulate osteoblasts and osteocytes

Question 12

How is a bone fracture repaired?

Answer 12

Hematoma formation- blood clot with granulation tissue(white blood cells like neutrophils and macrophages as well as fibrin clot and platelets)

Fibrocartilaginous callus formation- made of hyaline cartilage and dense connective tissue. Blood vessels also form

Bony callus formation- endochondral and intramembranous ossification gives rise to trabeculae and spongey bone

Remodelling- spongey bone converted to compact bone

Question 13

Bone remodelling in to turn spongey to compact bone.

Answer 13

Osteoclasts make a wide tunnel through the cancellous bone and osteoblasts behind make smaller tunnel of cortical bone. The wide tunnel at the start becomes smaller tunnel at end- this smaller tunnel becomes the Haversian canal. Creates an osteon in cancellous bone

Question 14

What is osteoid?

Answer 14

The unmineralised organic component of bone made of 90% collagen 10% ground substance

Question 15

What is a characteristic of rickets?

Answer 15

Bowed legs as bones lack mineralisation and are weakened. Lower mineralisation and so increased osteoid.

Question 16

What is the adult equivalent of rickets and what can cause it?

Answer 16

Osteomalacia caused by kidney disease as the kidney activates vitamin D. Protection from sunlight such as Hijab. Surgery that damages stomach and intestines and certain drugs.

Question 17

What types of osteoporosis are there?

Answer 17

Primary which can be type 1 or 2 and secondary.

Type 1- postmenopausal women no oestrogen increased osteoclasts function and decreased osteoblasts function.

Type 2- old age with decreased set last activity

Secondary- due to drug therapy, processes that affect remodelling like space travel or being inactive and metabolic bone diseases like hyperparathyroidism that results in increased PTH which increases osteoclasts activity

Question 18

What is achondroplasia?

Answer 18

Inherited genetic disease that affects endochondral ossification. This results in shortened stature as long bones don’t lengthen. Intramembranous ossification and flat bone formation unaffected. Normal head size etc