Chapter 6- Bones

Question 1

Name 6 functions of bones:

Answer 1

• Support
• Movement
• Protection
• Mineral storage
• Blood cell formation and energy storage
• Energy metabolism

Question 2

Canaliculi of osteon:

Answer 2

Run thru matrix connecting neighboring lacunae to another and to nearest capillaries.

Question 3

Lamella of osteon:

Answer 3

Layer of bone matrix where collagen fibers and mineral crystals align. Run in single direction.

Question 4

Haversion (central) canal:

Answer 4

Core of each osteon. Lined internally with endosteum.

Question 5

Compact bone:

Answer 5

Made up of osteons. Heavier and tougher.

Central canal contains its own blood vessels which supply nutrients to bone cells.

Question 6

Spongy bone:

Answer 6

Made of trabeculae. Lighter bones.
Do not contain osteons or blood vessels. They are made of lamella and osteocytes. The osteocytes get nutrients from capillaries in the endosteum via canaliculi.

Question 7

Intramembranous ossification phase 1:

Answer 7

(1) During week 8 of embryonic development, mesenchymal cells cluster within the connective tissue membrane and become bone forming osteoblasts.

Question 8

Intramembranous ossification phase 2:

Answer 8

Bone matrix (osteoid) is secreted within the fibrous membrane and calcifies. Osteoblasts become osteocytes.

Question 9

Intramembranous ossification phase 3:

Answer 9

Woven bone and periosteum form. Vascularized mesenchyme condenses on external face of woven bone and become periosteum.

Question 10

Intramembranous ossification phase 4:

Answer 10

Trabeculae at periphery grows thicker until plates of compact bone are present in both surfaces. Trabeculae remain distinct in the center of membranous bone, which become spongy bone. Final pattern is that of flat bone.

Question 11

Endochondral ossification phase 1:

Answer 11

Perichondrium surrounding diaphysis is invaded by blood vessels and become a bone forming periosteum. Osteoblasts lay down a collar of bone tissue around diaphysis.

Question 12

Endochondral ossification phase 2:

Answer 12

Cartilage in center of diaphysis calcifies and then develops cavities.

Question 13

Endochondral ossification phase 3:

Answer 13

The periosteal bud invades the internal cavities and spongy bone forms.

Question 14

Endochondral ossification phase 4:

Answer 14

The diaphysis elongates, and a medullary cavity forms as ossification continues. Secondary ossification centers appear in the epiphyses

Question 15

Endochondral ossification phase 5:

Answer 15

The epiphyses ossify. When completed hyaline cartilage remains only in the epiphyseal plates and articular cartilage.

Question 16

Why are bones considered organs?

Answer 16

Because they contain several different tissues

Question 17

Describe postnatal lengthening of endochondral bones:

Answer 17

Bones lengthen by growth of epiphyseal plates. Cartilage is replaced with bone tissue on diaphysis side as soon as it grows, so epiphyseal plate remains a constant thickness. At the end of adolescence, chondroblasts divide less often and plates become thinner. Cartilage stops growing and is replaced by bone tissue. Long bones stop lengthening when the epiphyses and diaphysis fuse.

Question 18

Describe postnatal widening of endochondral bones:

Answer 18

Osteoblasts in the iatrogenic layer of the periosteum add bone tissue in circumferential lamellae to the external face of the diaphysis as osteoclasts in the endosteum remove bone from within the diaphysis wall.

Question 19

Microscopic anatomy of epiphyseal plates (top to bottom):

Answer 19

Resting zone
Proliferation zone
Hypertrophic zone
Calcification zone
Ossification zone

Question 20

Resting zone:

Answer 20

The cartilage cells nearest epiphysis are small and inactive.

Question 21

Proliferation zone:

Answer 21

Tall columns formed by cartilage cells. Chondroblasts divide quickly, pushing epiphysis away from diaphysis.

Question 22

Hypertrophic zone:

Answer 22

Older chondrocytes enlarge and signal the surrounding matrix to calcify.

Question 23

Calcification zone:

Answer 23

Matrix become calcified; cartilage cells die; matrix begins deteriorating.

Question 24

Ossification zone:

Answer 24

New bones forming.

Question 25

Bone remodeling:

Answer 25

New bone tissue is continuously deposited and reabsorbed in response to hormonal and mechanical stimuli. Bone remodeling in adults occurs in endosteum.

Question 26

What are the cells responsible of bone modeling?

Answer 26

Osteoclasts break down bone tissue by secreting digestive enzymes and acid into bone surfaces.
Osteoid is secreted by osteoblasts and areas of bone deposit

Question 27

What are hormones that regulate bone remodeling?

Answer 27

Calcium salt is then deposited in the osteoid. Parathyroid hormone stimulates the reabsorption of bone.

Question 28

What is another factor regulating bone remodeling?

Answer 28

Bone grows thicker in response to forces from exercise and gains in weight.
Also, in the absence of mechanical stress, bone tissue is lost. Bone is also lost under near zero gravity conditions

Question 29

Compound fracture:

Answer 29

Broken ends of bone protrude thru skin

Question 30

Simple fracture:

Answer 30

Bone breaks cleanly but doesn’t penetrate skin

Question 31

6 more types of fractures:

Answer 31

Comminuted 
Spiral
Depressed
Compression
Epiphyseal
Greenstick

Question 32

Four phases of bone repair:

Answer 32

1) Hematoma formation
2) Fibrocartilaginous callus formation
3) Bony callus formation
4) Bone remodeling

Question 33

Osteoporosis:

Answer 33

Low bone mass and a deterioration of the microscopic architecture of the bony skeleton. Bone reabsorption outpace bone deposition.

Question 34

Osteoporosis treatment:

Answer 34

Supplemental calcium and vitamin D, increased exercise, and estrogen replacement.

Question 35

Gross anatomy of long bones:

Answer 35

Diaphysis (shaft), epiphysis (ends). Nutrient vessels serve diaphysis. Epiphyseal vessels serve epiphyses. Bone marrow occurs within spongy bone and in marrow cavity. Periosteum covers outer surface of bones; endosteum covers inner surface.

Question 36

Gross anatomy of flat, short, and irregular bones:

Answer 36

Periosteum on outer surface of compact bone; endosteum covers inner surface of spongy bone. No diaphysis or epiphysis. Contain bone marrow but no marrow cavity. Flat bones have 2 plates of compact bone, separated by later of spongy bone.