Ch. 6 Cartilage & Bone

Question 1

Why are the bones of the skeleton considered organs?

Answer 1

They contain several tissues

Question 2

What are the functions of the skeletal system?

Answer 2

Support, protection, movement, hemopoiesis (blood cell production), energy & mineral reserves

Question 3

Know the difference between cartilage and bone tissue, including: cell types, relative strength/flexibility, density of matrix, vascularization.

Answer 3

Cartilage:

• -avascular (no blood supply),
• -cell type: chondrocytes (in lacunae)
• -strength/matrix: elastic cartilage is very flexible, fibrocartilage has thick dense collagen fibers and resists strong compression (shock absorber)

Bone tissue:

• -well vascularized
• -cell types: osteocytes, osteoblasts, osteoclasts
• -strength: very strong, resists compression and tension
• -matrix: organic fibers and inorganic fibers
• ->inorganic: 65% mineral salts (calcium phosphate)
• ->organic: fibers (lots collagen), ground substance

Question 4

What is the difference between an osteoblast and an osteoclast? What’s an osteocyte?

Answer 4

Osteoblast: builds new bone
Osteoclast: break down bone
Osteocyte: mature bone cells

Question 5

What are the 3 types of cartilage and how do they differ? Be able to identify the cartilage type if given an example (e.g.: external ear, nose, pubic symphysis) and also be able to tell where each type is found.

Answer 5

3 types:
hyaline, elastic, fibrocartilage

Hyaline:

• -most common type
• -has tiny, nearly invisible, collagen fibers called fibrils
• -found: ends of long bones, respiratory structures, fetal skeleton

Elastic:

• -similar to hyaline but lots of elastic fibers
• -very resilient and flexible, tolerates repeated bending
• -found: in pinna (outer ear) and epiglottis

Fibrocartilage:

• -has little ground substance and the matrix has thick, dense collagen fibers
• -resists strong compression (shock absorber)
• -found: in intervertebral disks, knee joint, pubic symphysis

Question 6

Which type of cartilage is the most common?

Answer 6

Hyaline cartilage

Question 7

What are the two types of cartilage growth? Which is important for an increase in girth (size)? Which is important for length increase?

Answer 7

Types: appositional growth and interstitial growth

Girth size: appositional growth

Length increase: interstitial growth

Question 8

What is Appositional Growth?

Answer 8

Chondroblasts in perichondrium make new cartilage tissue by secreting new matrix on the perichondrium.

On the outside. This widens the cartilage.

Question 9

What is Interstitial Growth?

Answer 9

Chondrocytes within existing cartilage divide and secrete new matrix to lengthen the skeleton. Continues until skeletal maturity.

Question 10

Which as more cartilage, an adult or a juvenile?

Answer 10

Juvenile

Question 11

What is osteogenesis?

Answer 11

The process of bone formation

Question 12

Explain the process of endochondral ossification. Include the following terms: diaphysis, epiphysis, primary center of ossification, secondary center of ossification, epiphyseal plate, periosteal bud.

Answer 12

Most of bones of skeleton form this way.

Skeleton begins as hyaline cartilage. From primary center of ossification in diaphysis, bone cells begin to replace cartilage cells. Secondary centers of ossification form in epiphysis. Skeleton continues to grow via division of cartilage (and bone) cells until maturity. When centers of ossification meet (at epiphyseal plate), growth stops.

Periosteal Bud: a vascular connective tissue bud from the perichondrium that enters the cartilage of a developing long bone and contributes to the formation of a center for ossification.

Question 13

What happens when the epiphyseal plates have closed?

Answer 13

Growth stops

Question 14

What are the cells involved in producing new bone tissue?

Answer 14

Osteoblasts

Question 15

Be able to draw and label a long bone with the following structures: diaphysis, epiphyses, spongy bone, compact bone, epiphyseal line, periosteum, medullary cavity.

Answer 15

Um…go see the textbook and/or your notes!

Question 16

What is the periosteum? Where is it located? How is this different from endosteum?

Answer 16

Periosteum: outer membrane on bone, well supplied w/ nerves and blood vessels, attached to underlying bone via collagen fibers, and provides a place for tendons and ligaments to attach to bone.

Periosteum location: most external surface of bones (ex: long bones). Helps things stick.

Endosteum: Layer of cells lining the inner surface of bone in the medullary cavity.

Question 17

Differentiate between compact and spongy bone. What part of a bone has compact bone? What part has spongy bone?

Answer 17

Compact bone (cortical bone): smooth, dense, outsides of bones strong, rigid.

Spongy bone (trabecular bone): inside bones, better at shock absorption.

Question 18

Be able to label a cross section of compact bone, including Haversian canal, osteon, lamellae, canaliculi.

Answer 18

So…go study the textbook and/or your notes.

Question 19

What is an osteon? What are the concentric tubes that make up an osteon?

Answer 19

Osteon: structural unit of compact bone; also called a Haversian system.

Concentric tubes: concentric lamellae
–>rings of bone CT that surround the central canal and form the bulk of the osteon.

Question 20

What is a Haversian canal? What is the function/job of the Haversian canal?

Answer 20

It’s the central canal; cylindrical channel that lies in the center of the osteon. Traveling within the central canal are the blood vessels and nerves that supply the bone.

Question 21

What are the perforating canals (Volkmann’s canals)? What is their job/function?

Answer 21

Resemble central canals in that they also contain blood vessels and nerves. However, perforating canals run perpendicular to the central canals and help connect multiple central canals, thus creating a vascular and innovation connection among multiple osteons.

Question 22

What are canaliculi? How are these different from perforating canals? What is their job/function?

Answer 22

Tiny, interconnecting channels within the bone CT that extend from each lacuna, travel through the lamellae, and connect to other lacunae and the central canal.

House osteocyte cytoplasmic projecting that permit intercellular contact and communication. Nutrients, minerals, gases, and wastes can travel through these passageways between the central canal and the osteocytes.

Question 23

Consider the process of bone remodeling. How would bone respond to long-term, weight bearing exercise? How might bone respond to long term confinement/lack of use? To minimize risk of osteoporosis, should an individual sit quietly or exercise regularly?

Answer 23

Mechanical stress, in the form of exercise, is required for normal bone remodeling. In response, bone has the ability to increase strength over time. Weight-bearing activities, such as weight lifting or walking, help build and retain bone mass.

In contrast, lack of mechanical stress weakens bone through both demineralization of the bone matrix and reduction of collagen formation.

Exercising regularly will help minimize the risk of osteoporosis.

Question 24

What property or properties of cartilage make osteoarthritis so painful and difficult to treat?

Answer 24

Can create bone spurs. Articular cartilage is thin and doesn’t have good blood supply, heals poorly. Creates rubbing between 2 bones (ex: knee joint, bones rubbing back and forth).

Question 25

What is a bony callus? What causes this?

Answer 25

Fibrocartilaginous callus is replaced by primary bone. The trabecular of the hard callus continue to grow and thicken for several months.

Cause: 3rd step of fracture repair

Question 26

List the characteristics of irregular bones and provide examples.

Answer 26

Elaborate, complex shapes and do not fit into any of the categories.

ex: vertebra, ossa coxae (hip bones), ethmoid, sphenoid

Question 27

List the characteristics of long bones and provide examples

Answer 27

Greater length than width. Elongated, cylindrical shaft (diaphysis). This is the most common bone shape.

ex: humerus, phalanges, femur, tibia, radius, ulna, fibula

Question 28

List the characteristics of short bones and provide examples

Answer 28

They’re as long as they are wide. External surface covered by compact bone, interior composed of spongy bone.

ex: talus and carpals

Question 29

List the characteristics of flat bones and provide examples

Answer 29

Flat, thin surfaces. Roughly parallel surfaces of compact bone with layer of internally placed spongy bone. Provide extensive surfaces for muscle attachment and protect underlying tissues.

ex: sternum, roof of skull, scapulae, ribs, clavicles

Question 30

What’s intramembranous ossification?

Answer 30

Mesenchymal cells congregate in CT membrane.
Mesenchyme cells become osteoblasts and this region is an “ossification center” (osteoid).
Osteoblasts become osteocytes and new bone tissue is formed.
Embryonic blood vessels grow through the region, forming “woven” bone tissue (=trabeculae).
Forms flat bones

Question 31

Describe the 4 steps of bone healing.

Answer 31

Require both osteoblasts and osteoclasts. Osteoblasts tend to overgrow at site, osteoclasts smooth it out.

1. broken blood vessels=hematoma, inflammatory response
2. new blood vessels grow, osteoblasts form a fibrocartilaginous (soft callus)
3. trabeculae appear and join together the pieces of broken bone; new bone forms
4. bony callus is formed; osteoclasts smooth away excess tissue