Session 7 - Cartilage and Bone

Question 1

What does cartilage consist of?

Answer 1

Extracellular matrix, chondrocytes and proteoglycans

Question 2

What do chondrocytes do?

Answer 2

Produce and maintain the ECM

Question 3

What type of GAG is abundant in cartilage and why?

Answer 3

Hyaluronic acid and its negative charges means it attracts water to produce a hydrated gel that allows for diffusion and resistance to pressure

Question 4

What type of collagen is found in the ECM of cartilage?

Answer 4

Type 2

Question 5

What are the 3 types of cartilage?

Answer 5

Hyaline, elastic and fibrocartilage

Question 6

What is hyaline cartilage composed of?

Answer 6

Proteoglycans, hyaluronic acid and type 2 collagen

Question 7

What are groups of chondrocytes called?

Answer 7

Isogenous groups

Question 8

Where is hyaline cartilage found?

Answer 8

At articulating surfaces, nose, ribs, larynx, trachea and bronchus

Question 9

What is the perichondrium?

Answer 9

A layer of dense CT that surround hyaline cartilage except at the articulating surfaces

Question 10

What is the perichondrium responsible for?

Answer 10

Appositional growth as the fibroblasts in the perichondrium develop into chondrocytes which secrete the ECM causing growth of the cartilage from the edges

Question 11

What is interstitial growth of cartilage?

Answer 11

Where the isogenous groups deep into the cartilage produce ECM and move away from each other causing growth of the cartilage

Question 12

What is the composition of elastic cartilage?

Answer 12

The same as hyaline cartilage but with elastic fibres

Question 13

Where is elastic cartilage found?

Answer 13

In the pinna of the ear and the epiglottis

Question 14

What is fibrocartilage composed of?

Answer 14

Hyaline cartilage, dense regular CT (lots of type 1 collagen), fibroblasts (elongated) and rows of chondrocytes

Question 15

Where is fibrocartilage found?

Answer 15

Pubic symphysis, knee joint, intervertebral discs

Question 16

What is the role of fibrocartilage?

Answer 16

To act as a shock absorber in pressure areas

Question 17

What is endochondrial ossification?

Answer 17

Where hyaline cartilage is replaced by bone

Question 18

What types of bone are made from endochondrial ossification?

Answer 18

Long bone

Question 19

Outline the steps of long bone development

Answer 19

Starts with hyaline cartilage. Periosteal (compact) bone forms in the shaft. The central cartilage calcifies and arteries protrude in supplying osteogenic cells to the area, which develop into osteoblast which lay down osteoid. This is the primary ossification centre. Secondary centres forms at the epiphyses. These then calcify forming bone. Epiphyseal plate remains to allow lengthening of bone.

Question 20

What is osteoid?

Answer 20

Substance secreted by osteoblasts containing type 1 collagen and ground substance. It is unmineralised

Question 21

What are the 5 zones found at the epiphyseal growth plates

Answer 21

Zones of reserve cells, proliferation, hypertrophy, calcified cartilage and resorption.

Question 22

What is a synovial joint?

Answer 22

Articulating joint covered by hyaline cartilage. Contains synovial fluid lined by a synovial membrane

Question 23

What are osteogenic cells?

Answer 23

Bone cells that can divide and differentiate into osteoblasts

Question 24

What are osteoblasts?

Answer 24

Cells that produce osteoid found on the periosteum and endosteum

Question 25

What are osteoclasts?

Answer 25

Multi-nucleated cells that break down bone for remodelling.

Question 26

Where are osteoclasts found?

Answer 26

In depressions called Howship Lacunae

Question 27

What are osteocytes?

Answer 27

Osteoblasts that are surrounded by bone

Question 28

How do osteocytes reach to adjacent cells?

Answer 28

Through cytoplasmic extensions called canaliculi connecting cells via gap junction to exchange nutrients

Question 29

What type of bone develops from intramembranous ossification?

Answer 29

Flat bone e.g. Skull, pelvic, scapula and clavicle

Question 30

Outline the process of intramembranous ossification

Answer 30

A cluster of mesenchymal stem cells forms a nidus. These cells then develop RER and Golgi and differentiate into osteoblasts, which start to lay down the osteoid. The osteoid then mineralises forming bone spicules which merge to form trabeculae giving cancellous bone. The trabeculae can then merge together to form layers of lamellae, making up compact bone

Question 31

What is cancellous bone?

Answer 31

Network of trabeculae which combines strength and lightness. The spaces are filled with bone marrow

Question 32

What is compact bone?

Answer 32

The external surfaces of bone made up of layers of lamallae

Question 33

What is a lacuna?

Answer 33

The space where a chondrocyte lies

Question 34

What is the structure of compact bone?

Answer 34

The lamallae are arranged in concentric layers called osteons. Haversian Channels run down the middle of osteons where the arteries, Lymphatic and nerve vessels lie. Osteocytes are arranged in the osteons of mature bone.

Question 35

How is bone remodelled?

Answer 35

Osteoclasts break down bone forming a cutting cone. The osteoblasts then follow to form new osteons

Question 36

Why does bone need remodelling?

Answer 36

To meet the mechanical needs e.g. You want thicker stronger bone if you are exercising more

Question 37

Outline how bone repairs itself

Answer 37

1. Haematoma form as blood vessels break. Bone at edges die. There is swelling and phagocytes remove damaged tissue and blood clot 2. Fibrocartilaginous callus forms as new blood vessels infiltrate allowing fibroblast and osteoblasts to enter and form new bone, collagen and cartilage. 3. Bony callus formation. The fibrocartilaginous callus is converted into spongy bone 4. Bone remodelling

Question 38

What is osteoporosis?

Answer 38

Where more bone is broken down then is formed

Question 39

What are the 2 types of primary osteoporosis

Answer 39

1. Where there is an increase in osteoclasts | 2. Where there is a decrease in osteoblasts

Question 40

What is type 1 osteoporosis?

Answer 40

Resorption of bone in post menopausal women

Question 41

What is type 2 osteoporosis

Answer 41

Bone resorption in the elderly

Question 42

What are the 2 different types of type 2 osteoporosis

Answer 42

Increased Osteoclast activity and decreased osteoblast activity