Bone and Cartilage

Question 1

What are the three major classes of cartilage?

Answer 1

hyaline, elastic, fibrocartilage

Question 2

What are the two components of cartilage?

Answer 2

cells (chondroblasts and chondrocytes) and extracellular matrix.

Question 3

What are chondroblasts?

Answer 3

cartilage-forming cells

Question 4

What are chondrocytes?

Answer 4

cartilage-maintenance cells

Question 5

What is in the cartilage extracellular matrix?

Answer 5

collagen (type II) and amorphous ground substance

Question 6

What are some functions of cartilage?

Answer 6

absorb shock, reduce friction, repair bone fractures, necessary for endochondral bone growth.

Question 7

What do chondroblasts become after they lay down cartilage matrix?

Answer 7

chondrocytes

Question 8

What are lacunae?

Answer 8

Pockets within the matrix where the chondroblasts and chondrocytes are found.

Question 9

Is cartilage vascular or avascular?

Answer 9

avascular

Question 10

How does cartilage receive nutrients?

Answer 10

diffusion through the cartilage matrix

Question 11

What is the perichondrium?

Answer 11

A layer that can give rise to chondroblasts. It contains an outer fibrous layer and an inner chondrogenic layer.

Question 12

What does the outer fibrous layer contain, and what do they differentiate into?

Answer 12

fibroblasts; they differentiate into chondroblasts.

Question 13

What does the inner chondrogenic layer give rise to?

Answer 13

chondroblasts, which become chondrocytes.

Question 14

What are functions of the chondrocyte?

Answer 14

produce collagen and proteoglycans, secrete chondronectin (adhesion molecules).

Question 15

What is in the cartilage matrix?

Answer 15

collagen type II, hyaluronic acid, glycosaminoglycans, terriritorial and inter-territorial matrices

Question 16

What matrices surround each chondrocyte?

Answer 16

territorial and inter-territorial; the territorial has a high GAG content and low collagen content and vice versa for inter-territorial.

Question 17

What is hyaline cartilage often referred to as?

Answer 17

gristle; it is the most common type of cartilage

Question 18

What are features of hyaline cartilage?

Answer 18

avascular, contains type II collagen fibers, surrounded by perichondrium, grows appositionally or interstitially.

Question 19

Where is hyaline cartilage located?

Answer 19

fetal long bones, articular ends of bones, tracheal cartilages, larynx

Question 20

What is the matrix of hyaline cartilage composed of?

Answer 20

chondroitin sulfate, collagen fibers and proteoglycans

Question 21

What is the chondrogenic perichondrium a source of?

Answer 21

chondroblasts and osteoprogenitor cells.

Question 22

What are characteristics of elastic cartilage?

Answer 22

has elastic fibers in the matrix, surrounded by perichondrium, is flexible, has type II collagen.

Question 23

Where is elastic cartilage found?

Answer 23

auricle (pinna) of the ear, epiglottis.

Question 24

What are characteristics of fibrocartilage?

Answer 24

increased collagen, not surrounded by pericardium, type I collagen, sparse chondrocytes, has good tensile strength.

Question 25

Where is fibrocartilage located?

Answer 25

intervertebral discs, pubic symphysis, tendons & ligaments

Question 26

Where does interstitial growth occur?

Answer 26

from chondrocytes within the cartilage

Question 27

During embryogenesis, what do mesenchymal cells differentiate into?

Answer 27

chondroblasts

Question 28

What do the chondroblasts from the mesencyhmal cells then do?

Answer 28

Divide mitotically and fill the lacuna; they are surrounded by territorial matrix and inter-territorial matrix; which is known was INTERSTITIAL GROWTH.

Question 29

Where does appositional growth occur?

Answer 29

from undifferentiated cells at the surface of the cartilage, or perichondrium.

Question 30

What do the inner layers of the perichondrium do during appositional growth?

Answer 30

Differentiate into condroblasts and synthesize/secrete type II collagen precursors and other ECM components.

Question 31

What kind of a system is bone tissue based on?

Answer 31

canalicular

Question 32

Is bone vascular or avascular?

Answer 32

vascular

Question 33

How does bone increase in length?

Answer 33

through appostional growth of a hyaline cartilage model.

Question 34

What is bone formed by?

Answer 34

osteoblasts, which become osteocytes.

Question 35

What is the organic components of a bone?

Answer 35

the osteoid

Question 36

What is the inorganic component of a bone?

Answer 36

hydroxyapatite

Question 37

What are the three types of bone?

Answer 37

woven bone, compact bone, spongy bone

Question 38

When is woven bone most commonly seen?

Answer 38

during bone development and repair

Question 39

When is compact bone also referred to as?

Answer 39

lamellar bone

Question 40

What is spongy bone also referred to as?

Answer 40

trabecular or cancellous bone

Question 41

What are the lamellae which encircle a central blood vessel?

Answer 41

Haversian

Question 42

Where are the osteocytes found, and how are they connected?

Answer 42

between the lamellae; they are connected via canaliculi.

Question 43

What do Volkmann's canals do?

Answer 43

run perpindicular to haversian canals and connect the haversian canals to each other and to the surface of the bone.

Question 44

What does spongy bone contain? What does it surround?

Answer 44

trabeculae; they surround bone marrow spaces in long bones and flat bones.

Question 45

What is the periosteum?

Answer 45

A membrane that surrounds the entire bone.

Question 46

What are Sharpey's fibers?

Answer 46

fibers that connect to bone and periosteum. They are abundant where tendons and ligaments attach.

Question 47

What are osteocytes responsible for?

Answer 47

maintenance and turnover of the bone matrix.

Question 48

What do osteoprogenitors differentiate into?

Answer 48

osteoblasts, then osteocytes

Question 49

What do osteoblasts do?

Answer 49

control the mineralization of the matrix. They also synthesize the organic matrix of bone.

Question 50

What are the major protein products of an osteoblast?

Answer 50

type I collagen, RANKL, osteocalcin, osteopontin, bone siatoprotein.

Question 51

Where are osteoclast cells derived from?

Answer 51

monocytes (bone marrow)

Question 52

What occurs at adult remodeling sites and during development?

Answer 52

ARF (activation-resorption-reversal-formation).

Question 53

What is the primary regulator of bone turnover?

Answer 53

parathyroid hormone.

Question 54

What is stimulated at low PTH levels?

Answer 54

bone formation by osteoblasts.

Question 55

What is stimulated at high PTH levels?

Answer 55

osteoclast-differentiation factors (turns osteoblasts into osteocytes).

Question 56

What does the osteoblast synthesize after PTH binds to receptors on the osteoblast?

Answer 56

M-CSF (monocyte colony stimulating factor) and RANKL. The osteocyte releases M-CSF.

Question 57

What does M-CSF bind to?

Answer 57

an M-CSF receptor on a nearby monocyte.

Question 58

What does a monocyte bound to M-CSF become?

Answer 58

a macrophage that expresses RANK

Question 59

What does RANK bind to?

Answer 59

RANKL (osteoblast and macrophage binding).

Question 60

What does a macrophage become once it has bound to RANKL?

Answer 60

an immature osteoclast.

Question 61

What is osteoprotegerin?

Answer 61

substanced secreted by the osteoblast that binds to RANKL with greater affinity than rank. It inhibits maturation of osteoclasts.

Question 62

What does PTH block?

Answer 62

synthesis of osteoprotegerin.

Question 63

What are osteoclasts directly regulated by?

Answer 63

calcitonin, vitamin D and regulatory molecules of the osteoblasts.

Question 64

What are functions of the osteoclasts?

Answer 64

Bone remodelling (removing bone matrix and replacing with osteoblasts), proper shaping of the bones, extension of medullary space to allow for hematopoiesis.