0416 Bone and cartilage

Question 1

Briefly describe what bone is

Answer 1

Bone is a specialised form of connective tissue. It is made of cells (osteoblast, osteocytes, osteoclasts, etc) contained in an extracellular matrix of fibres (collagen) in ground substance

Question 2

What are the 4 types of cells in bone and what are their functions

Answer 2

Osteoprogenitor cells (Self replicate and differentiate into bone forming cells)
Osteoblasts (bone forming cells that deposit osteoid)
Osteocytes (modified osetocytes that regulate homeostassis)
Osteoclasts (phagocytic cells the resorb bone)

Question 3

What is the extracellular matrix of bone made of

Answer 3

70% of inorganic salts (calcium and phosphate) and 30% organic matrix (mainly collagen type 1)

Question 4

What is calcification and when does it occur?

Answer 4

Calcification is the accumulation of calcium salts in a body tissue, causing it to harden. It usually occurs after the secretion of osteoids (as well as other proteins) by osteoblasts). Initiates after a few days and can take months to finalize

Question 5

What is osteoid and where is it produced

Answer 5

Osteoid is the unmineralized, organic portion of the bone matrix that forms prior to the maturation of bone tissue. It is secreted by osteoblasts

Question 6

What are the 2 types of bone? What is their main difference

Answer 6

Woven and lamellar (compact or cancellous). Woven bone has irregular organisation while lamellar bone has orderly strata

Question 7

Describe woven bone and where/when you might find it

Answer 7

Woven bone is characterised by randomly arranged collagen fibres in osteoid. it is produced when osteoid is produced rapidly (e.g. when a fracture is healing)

Question 8

Describe compact bone and where would you find it

Answer 8

Compact bone is mature bone characterised by lamellae (concentric circles matrix) and Haversian canals (neurovascular). Also contains lacunae and canaliculi. It is the outermost layer of many bones in our skeleton

Question 9

Describe cancellous bone and where would you find it

Answer 9

Cancellous bone is mature bone with irregulae lamellae. It has a mesh of trabeculae which contain marrow. It is the inside of many bones in our skeleton

Question 10

What is the rate at which we replace/remodel bone ?

Answer 10

5-10% of our bones per year

Question 11

What 2 types of cells are directly responsible for remodelling bone (think destroying and building)

Answer 11

Osteoblasts and osteoclasts

Question 12

List the 2 methods of bone development and growth and briefly describe where they happen

Answer 12

Intramembranous ossification (direct replacement of mesenchymal tissue e.g. vault of skull, mandible). Endochondral ossification (bone replacing cartilage e.g. most long bones, vertebrae, pelvis)

Question 13

List some functions of bone

Answer 13

Mainly structural (protection, movement), source calcium and phosphate, Marrow (haemopoiesis)

Question 14

List some functions of cartilage

Answer 14

Supports soft tissues, shock absorption in joints, development, growth and healing of bone

Question 15

Briefly describe cartilage

Answer 15

Specialised connective tissue consisting of cells (condroblasts and chondrocytes) surroudning by an extracellular substance (gel like matrix of collagen, elastin and GAGs)

Question 16

What are the cellular components of cartilage and what do they do

Answer 16

Chondroblast = precursors to cells in cartilage
Chondrocytes = are the mature cartilage cells

Question 17

Why is the thickness of cartilage limited (hint think vascularisation)

Answer 17

Cartilage, unlike other connective tissues, has no vessels or nerves and depends on diffusion of nutrients. Thus growth limits thickness

Question 18

What is the name of the dense connective tissue surrounding cartilage

Answer 18

Perichondrium

Question 19

Describe Hyaline cartilage and where you might find it

Answer 19

It is cartilage with collagen fibre and ground substance of GAGs. It is the most common cartilage, a precursor of bone. IT is found in nasal septum, larynx, tracheal rings and most articular surfaces

Question 20

What is the name of the specialised type of hyaline cartilage that is found on the ends of bones

Answer 20

Articular cartilage - Transforms the articulating ends of the bones into lubricated, wear-proof, slightly compressible surfaces

Question 21

Describe fibrocartilage and where you might find it

Answer 21

Cartilage with collagen fibres and ground substance of GAGs. It looks like alternating layers of hyaline cartilage and thick layers of dense collagen fibres in one direction. It is found in intervertebral discs, arrticular cartilage and pubic symphysis

Question 22

Describe elastic cartilage and where you might find it

Answer 22

It is cartilage with elastic and collagen fibres and ground substance of GAGs. It is found in the external ear, external auditory canal and part of laryngeal cartilages

Question 23

What are centres of chondrification

Answer 23

COC are found during formation of cartilage when precursor cells become rounded and form densely packed cellular masses (COC)

Question 24

What are the 2 mechanisms of cartilage growth

Answer 24

Interstitial growth and appositional growth

Question 25

What are haversion canals

Answer 25

Neurovascular channels in compact bone that are surrounded by lamellae and run parallel to surface. They provide nutrients to tissues

Question 26

What are lacunae and what are canaliculi

Answer 26

Lacunae are small hollows in the bone matrix that house osteocytes. Canaliculi tiny canals between lacunae that allow communication and exchange between osetocytes