Lecture 10 - Bone and Cartilage

Question 1

What are the three types of cartilage?

Answer 1

• hyaline cartilage
• elastic cartilage
• fibrocartilage

Question 2

What body system is cartilage found in?

Answer 2

-skeletal system

In some vertebrates the entire skeletal system is cartilage.

Most bone is preceded by cartilage.

Question 3

What are the functions/characteristics of cartilage?

Answer 3

• compressible
• resists distortion
• absorbs shock
• reduces friction
• template for endochondral bone growth
• involved in bone fracture repair

Question 4

What is the name of the space where chondrocytes/blasts are found?

Answer 4

-lacunae

Question 5

How does cartilage receive nutrients? How does this affect the tissue?

Answer 5

• diffusion of nutrients through matrix from surrounding blood vessels (cartilage is avascular)
• cartilage is slow to heal

Question 6

What differentiates territorial matrix and inter-territorial matrix?

Answer 6

Territorial matrix:

• more newly formed
• closer in proximity to chondrocytes
• high GAG, low collagen

Inter-territorial matrix:

• older
• further from chondrocytes
• low GAG, high collagen

Question 7

What are the different layers of perichondrium and what are their functions?

Answer 7

Outer fibrous later:

• contains fibroblasts
• point of connection to other structures

Inner chondrogenic layer:

• contains chondroblasts which become chondrocytes
• produces matrix components

Question 8

What are characteristics of hyaline cartilage?

Answer 8

• most common cartilage
• avascular, receives nutrients by diffusion
• type II collagen
• translucent, blue grey/white
• solid but flexible
• chondrocytes found in groups
• perichondrium.
• grows both appositionally and interstitialy

Question 9

What are the characteristics of elastic cartilage?

Answer 9

• contains type II collagen and elastic fibers
• yellow color (without staining)
• more opaque, flexible and elastic
• chondrocytes mostly located singly
• surrounded by perichondrium.

Question 10

What are the characteristics of fibrocartilage?

Answer 10

• type I cartilage
• increased collagen concentration
• opaque
• reduced cellularity
• single, sparse chondrocytes
• no perichondrium

Question 11

Where is hyaline cartilage found?

Answer 11

• external auditory meatus
• larynx
• trachea
• bronchi
• fetal long bones
• epiphyseal plate
• articular surfaces

Question 12

Where is elastic cartilage found?

Answer 12

• auricle (pinna) of ear

- epiglottis

Question 13

Where is fibrocartilage found?

Answer 13

• intervertebral discs
• pubic symphysis
• insertion of some tendons and ligaments
• associated with dense connective tissues and hyaline cartilage

Question 14

What is the organization of bone tissue and why is it organized this way?

Answer 14

-organized in a canalicular system allowing penetration of blood vessels for high vascularity

Question 15

How is bone length increased?

Answer 15

• appositional growth of a hyaline cartilage model

- bone can not grow intersttially

Question 16

Bone is a(n) __________ tissue meaning that it is constantly __________, __________, and __________.

Answer 16

Active/living; resorption; reconstructed; remodeled

Question 17

What are the different components of bone matrix and what is their function?

Answer 17

Organic component:

• osteoid
• provides flexibility

Inorganic component:

• hydroxyapatite
• 35-65% of matrix
• provides rigidity

Question 18

What are the types of bone tissue and what are their characteristics?

Answer 18

Woven:

• occurs during bone development and repair
• rapidly produced
• haphazard collagen
• less structural integrity

Spongy:

• also called trabecular or cancellous bone
• 3D lattice of bone spicules
• spaces for bone marrow

Compact bone:

• also lamellar bone
• Haversian structure
• lacks larger cavities

Question 19

Describe the features of the Haversian structure of compact bone.

Answer 19

• Haversian system, also called OSTEON, consists of multiple concentric layers called LAMALAE
• border of osteon is called CEMENT LINE
• at center is a HAVERSIAN CANAL which contains a blood vessels and nerves
• blood vessels and nerves penetrate osteons to reach Haversian canals via VOLKMAN’S CANALS
• cells are located in LACUNAE between lamellae
• lacunae are connected to each other and Haversian canal by CANALICULI

Question 20

What are osteoprogenitor cells?

Answer 20

• stem cells which differentiate into osteoblasts and bone lining cells
• found on the inner periosteum, the nostrum, and lining vascular canals

Question 21

Describe osteoblast characteristics and major products.

Answer 21

Characterized by:

• alkaline phosphates (not in osteocytes)
• vitamin D3 (regulates osteocalcin)

Major products:

• type I collagen
• osteocalcin (binds hydroxyapatite)
• osteonectin
• osteopontin
• osteoprotegerin
• RANKL

Question 22

What cell type is the progenitor for osteoclasts?

Answer 22

-monocytes and monocytes progenitors located in the bone marrow

Question 23

What does high and low parathyroid hormone have on bone regulation.

Answer 23

Low PTH:

• bone formation
• osteoblast activation

High PTH:

• bone reabsorbtion
• release of osteoclast differentiation factors
• differentiation of monocytes into osteoclasts
• osteoclast activation

Question 24

Describe the process of osteoclast regulation by osetoblasts.

Answer 24

Formation:

• PTH binds osteoblast
• osteoblast stimulated to release M-CSF (monocytes colony stimulating factor) and RANKL (RANK receptor)
• M-CSF binds receptor on monocyte
• monocyte differentiates into macrophage
• macrophage releases RANK which binds RANKL (coupling cells)
• macrophage becomes immature osteoclast

Inhibition:

• osteoprotegerin binds RANKL prevents maturation of osteoclast
• calcitonin reduces bones resorption

Question 25

What are the two main products of osteoclasts which give them their function.

Answer 25

• cathepsin K: protease that catabolizes elastin, collagen, and gelatin
• H+ Cl- ions: dissolves inorganic bone matrix