Chapter 6 pt 2) Bones/ Skeletal Tissues

Question 1

Ossidication

Answer 1

• Process of bone tissue formation.
• Formation of the bony skeleton Begins at 2 months of develpoment.
• Bone remodiling and repair is a lifelong process.

Question 2

Endochondral Ossification

Answer 2

• Development of bones from cartlidge (called cartlidge bones). All of the bones below the skull develop this way.
• Begins at 2 months of development.
  
  • Hylane cartlidge is perviouly made and serves as a template for bone development. Cartlidge breaks down prior to ossification
• Primary Ossification Center)
  
  • Blood vessels inflitrate pericondrium making it periosteum.
  • Mesenchymal cells specialize into osteoblasts.

Question 3

Five Steps of Endocondral Ossification

Answer 3

1. Bone Collar forms around Hyaline Cartlidge
2. Cartlidge calcifies in the Diaphysis (shaft) center and cavities develop.
3. Periostial Bud invades the structure and forms spongy bone.
4. Diaphysis elongates and medulary cavity forms.
5. Epiphsyes Calcify leaving Hyaline Cartlidge only in Epiphesyal Growth Plate.

Question 4

Intramembranous Ossification (and 4 Steps)

Answer 4

• Mescenchymal cells form the frontal, parietal, occiptial, temporal, and clavicle bones.
  
  • 4 Major Steps

1. Meschenymal cells cluster together and differentiate into osteoblasts. This develops an Ossification center in a Fibrous Membrane
2. Osteoblasts scerete osteoid and calcify. They then become Osteoclasts.
3. Spongy Bone and primative Periostium Form. Osteoid is laid down to make spongy bone and Meschymal cells become Periostium
4. Compact Spongy Bone replace spongy bone just deep of Periostium. The spongy bone then fills with marrow.

Question 5

Postnatal Bone Growth

Answer 5

• Long Bones grow Lengthwise due to Insterstitial Growth in Epiphyseal Plate.
• Bone increases in Thickness through Appositional Growth.

Question 6

Interstitial Growth

Answer 6

• Growth in the Epiphysial Plate. Has Five Zones.

1. Resting Zone (at the top of the bone) Area of cartlidge in epiphyeal plate that is inactive
2. Proliferation Zone) Area of cartlidge on daiphyseal side which is rapidly dividing. New cells push away which causes lengthening.
3. Hypertonic Zone) Older Cartlidge cells enlarge and form interconnecting spaces.
4. Calification Zone) Cells calcify and condrocytes die.
5. Ossification Zone) Spincules of cartlidge (leftovers of dead condrocytes) are eroded by osteoclasts and reformed by osteoblsts into New Bone.

Question 7

Interstital Growth (Near the End of Adolescnese)

Answer 7

• Condrocytes divide less often
• Epiphyseal plate thins and eventually closes (epiphyseal plate closure)
• This process stops around 18 in females and 21 in males.

Question 8

Appositional Growth

Answer 8

• Growth in Widness of a bone. Can occur anytime throuought life as response to stress.
• Osteoblasts Secrete Bone matrix under Periostium on External Bone
• Osteoclasts Remove Bone on Endosteal Surface
  
  • Leads to bone that is generally thicker and stronger because building occurs faster than breaking down.

Question 9

Horomes that Regulate Bone Growth

Answer 9

• Growth Hormone) Most improtant hormone in stimulating epiphesial plate growth during childhood.
• Thyroid Hormone) Modulates growth to ensure propper propeotions,
• Testosterone (males) and Estrogen (females) activate at pruberty and cause adolesant growth spurts.
  
  • Also end the epiphesial plate growth (stimualte closeure at the end of aolesanse)

Question 10

Bone Remodeling

Answer 10

• About 5-7% of bone mass is replaced each week.
  
  • Spongy bone) fully replaced every 3-4 year
  • Compact Bone) every 10 years
• Remodeling is the replacment of old bone tissue with new bone tissue. Takes place at diffrent rates at diffrent sections of bone.
• Occurs on both the periostum and endostum.

Question 11

Bone Homeostasis (Bone Remodeling)

Answer 11

• Resoprtion) Function of Osteoclasts.
  
  • Secrete lysosomal enzymes and protons (H+) that digest Matrix.
  • Acidity converts calcium salts to soluable material.
• Bone Deposite) New bone matrix is secreted by osteoclasts.
  
  • Osteoid seam) band of unamterized matrix (Ostoid) that becomes calcified.

Question 12

Conrol of Bone Remodeling

Answer 12

• Two ways
  
  • Hormonal Controls) The need to release calcium into the blood
  • Response to mechanical stress

Question 13

Hormonal Control of Blood Ca+

Answer 13

• Parathyroid hormone (PTH) produced by parathyroid glands in response to low levels of Ca+.
  
  • Stimulates osteoclasts to reobsorb bone and release Ca+ into blood.
  • Secretion stops when Ca+ levels are reached.
• Calcitonin) Produced by parapholicular cells of thyroid in response to high calcium levels.
  
  • Effects are negligable but can cause calcium reorbstion at pharmacutical levels.

Question 14

Homeostatic Imbalance (Calcium Levels)

Answer 14

• Small changes in blood calcium can cause problems in nervous funtion
• Hypocalcemia) low Ca+ levels cause nerve excitability
• Hypercalcima) High Ca+ levels cause nonresponsivness

Question 15

Response to Mechanical Stress (Bones)

Answer 15

• Bones Reflect mechanical stress put on them. Bones recive stress from weight or muscle pulls.
  
  • Wolfs Law) Bones grow/remodel in accordance with the stress put on them
  • This stress is usually off center so bones tend to curve.
• Diaphysis is thickest where the bending stress is the greates.
• Bone can be hallow because compression and tenion cancel eachother out (Normal force is 0)

Question 16

Bone Fractures (Classification)

Answer 16

• Position of Bone ends after Fracture
  
  • Nondisplaced) Ends Retain Normal Position
  • Displaced) Ends are out of normal allignment
• Completness of Break
  
  • Complete) all the way through
  • Incomplete) Not broken all the way through.
• Weather Skin is Penetrated
  
  • Open (compound) Skin is penertated
  • Closed (simple) Skin is not penetrated

Question 17

Commutied Fracture

Answer 17

• Bone is broken into three or more pieces
• Typically in older people with more britlle bones.

Question 19

Compression Fracture

Answer 19

• Bone is crushed.
• Common in porus bones (ex osteoporosis) subject to a fall.

Question 20

Spiral Fracture

Answer 20

• Jagged Fracture occuring when a bone endures a twisting force
• common sports injury

Question 21

Epiphyseal Fracture

Answer 21

• Epiphyses and Daiphesis are split at the ephiphyesal plate.

Question 22

Depressed Fracture

Answer 22

• Bone is pressed inward
• Common skull fracture.

Question 23

Greenstick Fracture

Answer 23

• Incomplete bone fracture (simillary to how a wet/green twig breaks) Only one side of the shaft breaks
• More common in children.

Question 24

Fracture Treatment and Repair

Answer 24

• Reduction) realignemt of bone ends
  
  • Closed reduction) physisan manipulated to correct position
  • Open reduction) surgical pins or wires secure bone ends.
• Immobilization) Of the bone via a cast or traction is needed for healing
  
  • Repair time depends on break severity, bone broken, and patient age.

Question 25

Four Stages of Bone Repair

Answer 25

1. Hematoma Formation) Blood vessels hemmorage forming a mass of clotted blood called a hematoma. This site is swollen and painful
2. Firbrocartilaginous Callus formation) Mass of fibroblasts, cartlidge, osteogenic cells, and capalaries come together and start repairing tissue.
3. Bony Callus Formation) New trabecule are formed in fibrocartiganius callus. This is converted into a hard bony callus of spongy bone.
4. Bone Remodeling) excess material on diaphysis cover and meularry cavity is remoced and compact bone is laid down.

Question 26

Osteomalacia

Answer 26

• Bones are poorly mineralized. Ostoid is produced but calcium salts are not correct making the bones weak. There is pain upon bering wight.

Question 27

Rickets

Answer 27

• Osteomalacia of Children)
• Results in bowed legs or other deformaties
• Cause is low vitamin D

Question 28

Osteoporosis (defintion)

Answer 28

• Group of desieses where bone reopbstion occurs more than bone depositing. Matrix looks normal but bone mass declines

Question 29

Risk Factors for Osteoporosis

Answer 29

• Being Female after menopause age) Estogen levels drop which play a role in bone density
• Additional risk factors
  
  • Poor ecerxise habits, low calcium and protien intake, smoking, genetics, or other drugs.

Question 30

Treating Osteoporsis

Answer 30

• Calcium and Vitamin D suplements, Wight bering excercise, and hormone replament therapy.

Question 31

Preventing Osteoporosis

Answer 31

• High Calcium diet.
• Reduce consuption alchocol and carbonated beverages.
• Pleanty of weight bering excercise.

Question 32

Pagets Desise

Answer 32

• Poor bone develoment due to excessive bone deposit and reobsorbtion.
  
  • Bone is called pagetic bone. Has hogh ratio of spongy bone compared to compact bone.