Cartilage & Bone

Question 1

What are the contents of extracellular substance in cartilage?

Answer 1

Collagen fibers, aggregates of Proteoglycans rich in chondroitin sulphates, glycoproteins

Question 2

What are chondrogenic cells?

Answer 2

Stem cells for cartilage, can transform into chondroblasts

Question 3

What are chondroblasts?

Answer 3

Build bone by actively producing components of ECS during cartilage formation

Question 4

What are chondrocytes?

Answer 4

Mature cartilage cells, which continue to produce smaller amounts of ECS in order to maintain and strengthen the cartilage

Question 5

What are the common characteristic for all cartilage types?

Answer 5

A vascular, ground substance rich in chondroitin sulphates, chondrocytes in lacunae, chondral territories

Question 6

What are Chandra’s territories?

Answer 6

Lacunae surrounded by condensed ground substance

Question 7

What is the perichondrium?

Answer 7

A layer of dense CT covering the cartilage surface. It provides the cartilage with oxygen and nutrients as it contains blood vessels.

Question 8

Which layer of the perichondrium contains chondrogenic cells?

Answer 8

The inner layer

Question 9

What is growth by apposition?

Answer 9

When the chondrogenic cells differentiate into chondroblasts, which then deposit additional layers of ECS on the existing surface, leading to an increase in the tissue’s overall size or thickness. (MORE ECS)

Question 10

What is interstitial growth?

Answer 10

Growth from within, when the chondrocytes divide in lacunae and produce ECS. (MORE CELLS)

Question 11

What are the main features of hyaline cartilage?

Answer 11

Has chondral territories, collagen type II, ground substance rich in aggrecan

Question 12

What are the mechanical properties of hyaline cartilage?

Answer 12

Resistance to compression resulting from properties of highly hydrated proteoglycans (aggrecan)

Question 13

What are the key features of elastic cartilage?

Answer 13

Has chondral territories, collagen type II, network of elastic fibers, ground substance

Question 14

What are the mechanic properties of elastic cartilage?

Answer 14

Elasticity

Question 15

What are the key features of fibrocartilage?

Answer 15

Few chondral territories, collagen type I, small amount of ground substance, no perichondium —> cannot grow appositionally

Question 16

What are the mechanical properties of fibrocartilage?

Answer 16

Resistance to stretch

Question 17

What are the main components of ECS in bone?

Answer 17

HA crystals, collagen type I fibers, ground substance (osteoid) with proteoglycans and glycoproteins

Question 18

What is the function of osteonectin?

Answer 18

Binds HA crystals to collagen

Question 19

What is the function of osteocalcin?

Answer 19

Binds Ca, participates in mineralization

Question 20

What is the function of osteopontin?

Answer 20

Binds cells with ground substance

Question 21

What is the function of bone silo protein II?

Answer 21

Strongly promotes mineralization

Question 22

What is the function of bone morphogenic proteins?

Answer 22

Promote differentiation of osteoblasts, induce formation of new bone

Question 23

What type of junctions are the long processes of osteocytes connected by?

Answer 23

Gap junctions

Question 24

How do osteocytes get oxygen and nutrients?

Answer 24

Oxygen and nutrients diffuse via canaliculi into lacunae, where osteocytes reside

Question 25

What are the key features of quiescent (resting) osteocytes?

Answer 25

Most numerous, poorly developed organelles, produce small amounts of ECS

Question 26

What are the key features of resorptive osteocytes?

Answer 26

Contain lysosomes which bread down the surrounding ECS by releasing proteinases, liberate Ca ions

Question 27

How can the activity of osteocytes connected close to each other be coordinated?

Answer 27

By exchange of chemical signals through gap junctions

Question 28

What are the key features of osteoclasts?

Answer 28

Bone marrow-derived, multinucleated, resorb bone, ruffled border

Question 29

How do osteoclasts digest bone?

Answer 29

1. They seal off the space beneath the ruffled border by integrity ring, 2. They release H+ ions (acidification & dissolution of HA crystals), 3. They realest lysosomal enzyme for extra cellular digestion, 4. The endocytose predigested bone fragments and digest them intracellulary

Question 30

How do osteoblasts control the differentiation and recruitment of osteoclasts?

Answer 30

1. Bone marrow stromatolites cells send out M-CS. 2. M-CS makes osteoprogenitor cells express RANK-receptors. 3. Osteoblasts express RANKL. 4. RANKL binds to RANK-receptors. 5. Osteoprogenitor cells transform into osteoclasts and digest old bone

Question 31

What are bone lamellae?

Answer 31

The structural units of mature (lamellar) bone

Question 32

What 2 types of bone are there?

Answer 32

Spongy (cancellous) and Compact

Question 33

What is spongy bone built of?

Answer 33

Interconnected networks of bone trabeculae

Question 34

What is compact bone made of?

Answer 34

A compact array of parallel osteoblasts formed around Haversian canals

Question 35

What is the periosteum?

Answer 35

A layer of dense CT containing blood vessels, osteoprogenitor cells, and inactive osteoclasts

Question 36

What is the endosteum?

Answer 36

A single layer of flat cells lining the inner surfaces of bone. It’s function is to support and protect the bone tissue