Lecture 17: Cartilage And Bone

Question 1

What is the composition of cartilage in terms of its cells and extracellular components?

Answer 1

Chondrocytes surrounded by a dense network of collagen and elastic fibres embedded in a gel-like matrix that also contains water and ground substance

Question 2

What are the 3 components of the cartilage matrix?

Answer 2

Fibres, water and ground substance

Question 3

What are the 3 types of cartilage?

Answer 3

Hyaline
Elastic
Fibrocartilage

Question 4

What are the 3 components present in hyaline cartilage matrix?

Answer 4

1. Type II collagen
2. Hyaluronate proteoglycans aggregates bound to collagen matrix
3. Tough dense tissue often containing fluid

Question 5

How do chondrocytes present in hyaline cartilage?

Answer 5

Present as single cells or if recently divided in small clusters, isogenous groups but separate as they lay down extracellular matrix

Question 6

What are the 2 components of ground substance?

Answer 6

Hyaluronic acid and proteoglycans

Question 7

What is the function of chondrocytes?

Answer 7

Produce and maintain the extracellular matrix

Lies in a lacuna

Question 8

What are the 2 main layers in hyaline cartilage?

Answer 8

Perichondrium and cartilage extracellular matrix with chondrocytes

Question 9

What is perichondrium?

Answer 9

Dense connective tissue that covers the margin of hyaline cartilage

Question 10

What does perichondrium contain?

Answer 10

Elongated, fibroblast-like cells that become chondroblasts and then chondrocytes

Question 11

Why is the cartilage extracellular matrix highly hydrated?

Answer 11

Water is non compressible and so permits resilience to increased pressure

Question 12

What are 2 examples of hyaline cartilage?

Answer 12

C-shaped tracheal cartilage in tracheal wall 
Articular surfaces (joints)

Question 13

What is the function of cartilage in the tracheal wall?

Answer 13

Reinforces trachea and helps to protect and maintain airway

Question 14

What are the 3 components of the elastic cartilage matrix?

Answer 14

1. Elastic Fibres
2. Type II collagen
3. Hyaluronate proteoglycans aggregates

Question 15

What are the 3 locations where elastic cartilage can be found?

Answer 15

Pinna of the ear
Eustachian tube (connects ear to mouth)
Epiglottis (flap that ensures food goes to the right tube)

Question 16

What are the 2 layers in elastic cartilage?

Answer 16

Perichondrium and cartilage itself

Question 17

What are the 3 main components of fibrocartilage matrix?

Answer 17

A lot of type I collagen
Small amount of type II
Hyaluronate proteoglycan aggregates

Question 18

How are the cells distributed in fibrocartilage?

Answer 18

Rows

Question 19

Do fibrocartilage have perichondrium?

Answer 19

No they only have fibroblasts

Question 20

What are 2 examples of places where fibrocartilage can be found?

Answer 20

Intervertebral discs

Menisci of the knee joint

Question 21

What is the function of fibrocartilage?

Answer 21

Shock absorber and to resist shearing forces - that’s why it’s quite messy inside - have to resist forces from diff directions

Question 22

How does cartilage grow?

Answer 22

Appositional growth - growing from the periphery

Question 23

Can cartilage be repaired?

Answer 23

No chondrocytes cannot undergo mitosis, fibroblasts lay down scar tissue instead

Question 24

What are the 2 main components of bone?

Answer 24

Matrix and cells

Question 25

What are the 2 inorganic components of the bone matrix?

Answer 25

Calcium hydroxyapatite

Question 26

What is the function of the inorganic components of bone matrix?

Answer 26

Resists bending and compression forces

Question 27

What proportion of the matrix is inorganic?

Answer 27

65%

Question 28

What proportion of the matrix is organic?

Answer 28

35%

Question 29

What are the 3 organic components of bone matrix?

Answer 29

Collagen 1 GAGs and proteoglycans Non-collagen out proteins

Question 30

What is the function of organic component of bones?

Answer 30

Resist pulling and tension forces

Question 31

What are the 4 types of cells present in bones?

Answer 31

Osteoprogenitor Osteoblasts Osteocytes Osteoclasts

Question 32

What is a osteoprogenitor?

Answer 32

Undifferentiated stem cell that eventually develops into an osteoblast

Question 33

What is a osteoblast?

Answer 33

Intermediate cells that can’t divide | Lays down new bone

Question 34

What are osteocytes?

Answer 34

terminally differentiated bone cell trapped within osteon, maintains bone and resists stress and force

Question 35

What are osteoclasts?

Answer 35

Multinucleated cell that secretes acids and enzymes to dissolve bone matrix

Question 36

What is the general structure of compact/cortical bone?

Answer 36

Functional unit is osteon, which is made up of layers of compact mineralized collagen which traps osteoblasts that produce bone,

Question 37

How do bones form from cartilage?

Answer 37

Endochondral ossification

Question 38

What are the 6 stages of emdochondral ossification?

Answer 38

1. Bone collar forms around the diaphysis of the hyaline cartilage model 2. Central cartilage calcifies and nutrient artery penetrates the centre of the bone to supply osteoblasts (primary ossification centre formed) 3. Medulla becomes cancellous bone, cartilage forms epiphyseal growth plates and epiphyses develop secondary centers of ossification 4. After birth: Epiphyses ossify and growth plates moves apart to lengthen bone 5. Adult: Epiphyseal growth plates replaced by bone but hyaline articular cartilage remains

Question 39

How does bone increase in length?

Answer 39

Endochondral ossification

Question 40

How does bone increase its girth?

Answer 40

Periosteal ossification

Question 41

What are the 5 zones of epiphyseal growth plate?

Answer 41

1. Zone of reserve cartilage 2. Zone of proliferation 3. Zone of hypertrophy 4. Zone of calcified cartilage 5. Zone of resorption

Question 42

What happens at the zone of reserve cartilage?

Answer 42

No cellular proliferation of active matrix production

Question 43

What happens at the zone of proliferation

Answer 43

Cellls actively dividing to form columns, cells enlarge and secrete matrix

Question 44

What happens at the zone of hypertrophy?

Answer 44

Cells enlarge greatly, matrix compressed into linear bands between cell columns

Question 45

What happens at the zone of calcified cartilage?

Answer 45

Enlarged cells begin to degenerate and matrix calcifies

Question 46

What happens at zone of resorption?

Answer 46

Small blood vessels and connective tissue invade the region occupied by dying chondrocytes, leaving the calcified cartilage as spicules between them

Question 47

What are osteons?

Answer 47

Cylindrical structures that contain a mineral matrix and living osteocytes connected by canaliculi

Question 48

What is a canaliculi?

Answer 48

Tiny canals that transport stuff

Question 49

What is lamellar?

Answer 49

Layers of compact matrix that surround a central canal called the Haversian canal

Question 50

What is Haversian canal?

Answer 50

Contains the bone’s blood vessels and nerve fibers

Question 51

What are Volkmann canals?

Answer 51

Transverse vessels that connect adjacent osteons connect blood vessels of the Haversian canals

Question 52

What is the periosteum?

Answer 52

Tissue covering bone’s outer surface

Question 53

What is osteoarthritis?

Answer 53

Age-related degeneration leading to mechanical failure of the articular cartilage as joint space narrows due to bone rubbing against bone

Question 54

What is rheumatoid arthritis?

Answer 54

Autoimmune disease where the synovial membrane is inflamed, leads to damage of underlying bone and articular cartilage and they disintegrate

Question 55

What are osteophytes?

Answer 55

Growth of bony spurs