skeletal system 3

1. What is the structural unit of bone tissue?

the Haversian system, or osteon

2. What are the structural components of the osteon?

Haversian canal or central canal, lamellae, osteocytes, lacunae,

matrix, canaliculi.

3. Briefly describe the following.

Haversian canal or central canal – little tunnels in the bone that

contain blood vessels.

lamellae – concentric layers of bone tissue surrounding the Haversian

canals.

osteocytes – bone cells – live in lacunae.

lacunae – little holes in bone where osteocytes live.

matrix – non-living substance between cells, especially in cartilage

and bone tissue.

canaliculi – tiny tunnels between lacunae – provide a way for

cytoplasmic processes of osteocytes to contact each other and pass

oxygen, nutrients, carbon dioxide, wastes, etc. between each other

and the blood vessels in the Haversian canals.

4. What are the 2 main components of bone matrix?

organic matrix and inorganic matrix.

What is organic matrix? What is another name for organic matrix?

Why does bone tissue need organic matrix?

osteoid – protein, collagen fibers. needed for flexibility.

What is inorganic matrix? Why does bone tissue need inorganic matrix?

minerals – mainly Ca - calcium. needed for rigidity and strength.

What does “organic” mean? (chemically)

derived from living things; carbon based; usually containing C-H bonds

What does “inorganic” mean? (chemically)

not organic - not containing C, C-H

5. Name the 3 types of bone cells and briefly describe their function.

osteocytes – originally osteoblasts, live in lacunae in bone.

osteoblasts – form new bone.

osteoclasts – resorb bone.

Which of these bone cell types cannot divide?

osteocytes

Which of these bone cell types is the biggest?

osteoclasts

6. How do osteoblasts make new bone?

secrete osteoid, the secrete an enzyme that helps with mineral

deposition.

How do osteoblasts become osteocytes?

by trapping themselves in the bone matrix.

7. Which of these terms implies calcium deposition for normal bone

formation, and which implies calcium deposition in an abnormal

location?

ossification - calcium deposition for normal bone formation.

calcification – calcium deposition in an abnormal location.

8. Where can osteoblasts be found in bone, if they are not in the

lacunae?

periosteum, endosteum, Haversian canals.

9. What is a closed fracture?

the skin over the fracture site is unbroken, and the fractured bone

has not been exposed to microorganisms.

What is an open fracture?

The skin has been broken, fractured bone is exposed to

microorganisms, can become infected.

10. Briefly describe these types of fractures.

greenstick – fracture does not go completely through bone.

transverse – straight across.

oblique – diagonally across bone.

comminuted – several small fragment, fragment lines may radiate from a

common point.

physeal – through a growth plate in a young animal.

11. Whose fracture heals fastest – a young animal or an old one?

young animal

Do fractured bones hurt? Why?

yes – nerve endings are present in bone.

12. List 7 factors affecting fracture healing.

blood supply, immobilization, fracture reduction, bone size,

fracture type, presence of infection, age of patient.

Which 2 of these are most important?

blood supply, immobilization.

13. What are the 2 sources of blood supply that a bone has?

nutrient artery, vessels of periosteum.

What is the name of the hole in a bone where a blood vessel normally

enters?

nutrient artery

14. Why is immobilization important to fracture healing?

any movement breaks down healing

15. What is fracture reduction?

putting the bone back together as close to normal as possible.

What does the presence of infection do to the healing process?

delays it – due to physical barrier of exudate, general unhealthy

local environment.

16. What is a non-union?

improper healing of a fracture – it healed, but in pieces.

17. Give some examples of external fixation of a fractured bone?

reducing and immobilizing a fracture without surgery.

18. What is internal fixation of a fractured bone?

surgical repair of a fracture. IM (intramedullary)pin, plate,

screws, wires.

19. List the 4 stages of the body’s fracture repair, in order of

occurrence.

callus formation, callus vascularization, callus ossification,

callus reorganization.

20. What is a callus?

a bone scab

21. Briefly describe callus formation.

when the bone breaks, blood vessels are broken and a blood clot

forms. the fibrin in the clot forms a “scaffold” for osteoblasts to occupy while making new osteoid. at first the new bone is loosely woven and unorganized.

Briefly describe callus vascularization.

blood vessels growing into the callus.

Briefly describe callus ossification.

calcium and other minerals are deposited in the callus. the callus

will now show up white on a radiograph.

Briefly describe callus reorganization.

by the efforts of osteoclasts and osteoblasts, the original

unorganized bone is remodeled along lines of stress to more closely

resemble the original unfractured bone. increases strength of the

fracture site.

22. What is rickets?

bone deformity occurring in a young animal due to lack of vitamin D,

which helps calcium be absorbed from the gastrointestinal tract.

Do we see many cases of rickets in this day and age?