Study Guide – Skeleton Test – Chapter 6

Be able to define these terms, provide their function, describe their form and how it follows their function, and label them on a diagram:

• Lacuna – “little lake”, bathes osteocyte with interstitial fluid • Osteon* (no function necessary) • Canaliculi – filled with interstitial fluid, which connects osteocytes with blood supply, allows projections from osteocytes to grow toward each other • Interstitial fluid – bathes cells, allows for exchanges between blood and osteocytes (acts like blood), fills canaliculi and lacunae • Periosteum – smooth and strong covering for bone, protects it and allows for smooth surface for articulation and contact with body’s tissues • Central canal – in center of osteo, carries blood vessels and nerves in direction parallel to axis of bone (walls of diaphysis) • Medullary artery – carries blood through medullary canal • Nutrient artery – connects blood in bone with blood in rest of body • Volkmann’s canals – connect central canals, also connect blood in medullary canal with nutrient artery and everything in between • Medullary canal – holds marrow as well as blood vessels and nerves • Epiphysis – ends of long bone, articulates w/ other bones and holds spongy bone • Diaphysis – long portion of long bone, provides strength • Metaphysis* • Yellow marrow – stores fat • Red marrow – makes blood • Dense bone – made of osteons, gives strength to bone; outer part of diaphyses and epiphyses • Spongy bone – in epiphyses of long bones, filled with small spaces that lighten bones and contain red marrow

Know the definition and function of these terms:

• Osteoblast -- makes bone (secretes matrix), when surrounded it turns into osteocyte • Osteoclast – breaks down bone in remodeling • Osteocyte – maintainer of bone, found in lacunae • Bone matrix – made by osteoblasts, hard and strong part of bones • Epiphyseal plate (and closing of it)

Be able to answer these questions:

1. When does an osteoblast become an osteocyte? When it is surrounded by the matrix it secreted

1/12

2. What component of bone provides flexibility? Which component provides strength? What examples from the lab demonstrate this? Ca & P – strength, removed by vinegar Keratin – flexibility, degraded by baking

3. What are the 2 steps of an osteocyte forming bone? 1. secrete matrix (gel-like) 2. Attract minerals to turn matrix into hard bone

4. Compare and contrast spongy and dense bone.

Spongy – full of holes wh/ contain marrow and reduce weight, has osteocytes, but not osteons Dense – osteons provide structure, blood vessels run throughout

5. What happens to the marrow in the medullary canal as you age? How can examining a bone help you determine the age of a mammal?

Turns to yellow marrow (started red), that and growth plate closing indicate age

6. You are a glucose molecule in a blood vessel in the medullary (nutrient) artery of a bone. What might be your path to an osteocyte? Then how would the waste product carbon dioxide get to the blood vessels in the periosteum?

Volkmann’s canal to central canal’s artery to canaliculi to lacuna to osteocyte Reverse for carbon dioxide

7. Why does bone need the complicated system discussed in #6? It’s so much more complicated and structured than blood flow through the skin.

Bone is hard, blood vessels can’t grow through it like they can through muscles, need to build bone w/ tunnels and canals so that vessels and canaliculi can go through

8. Why does bone heal so much more quickly than cartilage?

Good blood supply

9. In what direction do the central canals run within the diaphysis? What runs perpendicular to them? Central canals run parallel to the walls of the diaphysis; the nutrient canal, the Volkmann’s canals, and the canaliculi are perpendicular

10. How are tendons and ligaments attached to bones?

The periosteum grows out and becomes the tendons and ligaments

11. What are the steps in the healing of fractures?

• Step 1. organization – – clot formation – then procallus (fibrous connective tissue) to protect and stabilize area – Happens within 5 days • Step 2. callus formation – – 1st transformed to soft callus by adding cartilage – Then by day 28, have hard callus (bone, but weak and not organized) • Step 3. Remodeling – Happens over subsequent years: break down hard callus and build strong dense bone with osteon structure

12. Why are bones relatively light? What is the advantage of their structure rather than their being all dense bone? (2 advantages)

• Spaces filled with red marrow which produces blood (hematopoeisis) • Spaces also make bone lighter

13. Give 4 different reasons bone might be remodeled. Know the general steps of the process.

Growth (remove bone from medullary canal as person gets taller and bone gets wider), need for calcium, bone thickened in response to stress (such as athlete in training)

14. Know the causes and symptoms of these diseases:

• rickets Due to lack of vitamin D Leads to softening of bones Symptoms include:Bone pain or tenderness,Skeletal deformities, Impaired growth, Increased tendency toward fractures

• arthritis, Painful inflammation and swelling of joints

• osteoporosis, Bones are weakened by loss of bone mass, which causes spaces to form in the bones.

• scoliosis, In scoliosis, the spine is curved in an unnatural manner.

scurvy, Caused by lack of vitamin C • Weakens collagen in tissues, bones, and blood vessels • Symptoms include: – Bleeding into periosteum, muscles and joints, causing pain – Swollen and bleeding gums – Easy bruising

• carpal tunnel In carpal tunnel syndrome, there is pressure on the median nerve of the wrist. Repetitive motion of the wrist joint and bone spurs are two possible causes.