Bones

Question 1

smallest bone in the human body

Answer 1

The stapes or stirrup bone

Question 1

humans have ? bones

Answer 1

206 in adults and 300-350 in infants

Question 2

Functions of bones

Answer 2

• Support
• Protection
• Movement
• Mineral storage
• Blood cell formation 
• Energy storage
. Attachment sites for muscle

Question 3

Compact bone tissue - in outer regions of the bone. Why?

Answer 3

• Bending exerts strongest forces in these areas.

Question 4

• Spongy bone tissue -

Answer 4

in inner regions,
mainly near epiphyses
- Spongy bone “pillars” (trabeculae) are aligned along stress lines
- Red bone marrow (even in adults) – in marrow cavities

Question 4

• Osteoblasts:

Answer 4

bone-building cells

Question 5

Osteoclasts

Answer 5

bone-dissolving cells. Larger than other bone cells.

Question 6

Osteocytes

Answer 6

mature osteoblasts, trapped in matrix

Question 7

Compact bone tissue. In outer regions. Why?

Answer 7

Strongest force there.

Question 8

Red bone marrow tissue

Answer 8

Lymphoid tissue, all lymphoid tissue is reticular tissue.

In the spongy bone cavities.

Question 9

What structure is flat bones of the skull.

Answer 9

Spongy bone sandwiched between compact bone. Think about how heavy a compact bone head would be. Also spongy bone helps impact.

Question 10

Perichondrium

Answer 10

• Which acts like a girdle to to resist outward pressure of the cartilage
• growth and repair of cartilage
• 60-80% water very resilient

Question 10

Hyaline cartilage

Answer 10

Most abundant

Question 11

• Periosteum:

Answer 11

• Dense irregular CT
• Covers most of bone - Functions:
  – Resists tension
  – Growth
  – Attachments
  (Periosteum secured by perforating fibers)

Question 12

• Articular cartilage

Answer 12

a thin layer hyaline cartilage covering the joint surface of each epiphysis.

Question 13

• Medullary cavity in

diaphysis. Contains:

Answer 13

• Red bone marrow (at birth)
• • Contains hematopoietic stem cells (immature blood cells)
• • A lymphoid structure (reticular connective tissue)
• Yellow bone marrow (in adults)
• • Adipose tissue

Question 14

• Endosteum

Answer 14

for remodeling interior surfaces of bone
Exists as the interior layer lining the inside of the medullary cavity.
And canals in compact bone.

Question 15

hydroxyapatite

Answer 15

primarily calcium phosphate

- Resists compression

Question 16

What are the 2 types of mature bone tissue?

Answer 16

compact and spongy

Question 17

• Osteoid

Answer 17

• the matrix( ground substance and fibers) secreted by the osteoblasts.
• This also includes enzymes promoting calcium phosphate formation

Question 18

Concentric lamellae

Answer 18

form an osteon

Question 19

Interstitial lamellae

Answer 19

remnants of old osteon

Question 20

Woven bone

Answer 20

immature bone
• Bone tissue that has recently formed
- Produced rapidly (e.g. fetus or healing fracture)
- Eventually remodeled into spongy or compact bone
• Has trabeculae
• Collagen fibers randomly arranged (“woven”), so…
- No lamellae
- Weaker than spongy or compact bone
= mature bone

Question 21

Intramembranous bone formation steps

Answer 21

1. Mesenchyme gives rise to osteoblasts
   And secrete the organic part of the bone matrix( Osteoid)
2. Surrounded by the matrix blasts become cytes. And woven bone is the result
3. The woven bone tissue are trabeculae but no lamellae. During this stage the mesenchyme condenses to form the periosteum.
4. Trabeculae at apical surface grow thicker and become compact bone. Inner trabeculae remain and form spongy bone.

This is flat bone of the skull and clavicle. No other intramembraneous bones exist.

Question 21

Endochondral bone formation steps

Answer 21

1. Cartilage model grows a periosteum
   • Periosteum produces bone collar
2. Chondrocytes in center of diaphysis cause cartilage matrix to calcify
   • Calcified matrix blocks nutrient diffusion • Chondrocytes die -> cavity is produced
3. Periosteal bud (vessels, bone cells) invades diaphysis • Spongy bone deposited over calcified cartilage
   • Resulting bony region is called the primary ossification center
   
4. Steps 2 & 3 occur in the epiphyses as well: - Cartilage matrix calcifies
   - Chondrocytes die
   - Bud invades
   - Bone tissue deposited
   • Results in secondary ossification centers
   • Does not happen until
   around birth

5. Further ossification and remodeling
•  Mature arrangement of compact & spongy bone
•  Cartilage remains in two places:
- Articular cartilage - Epiphyseal plate


Question 21

Diaphysis

Answer 21

Shaft of the long bone.

Question 22

Epiphysis

Answer 22

The bone ends

Question 23

Epiphyseal line

Answer 23

Between the diaphysis and each epiphyses of the adult longbone. Consists of compact bone.
-remnant of the epiphyseal plate, a disk of hyaline cartilage that grows during childhood to lengthen the bone.

Question 25

Intramembranous ossification

Answer 25

Process of bone development of ‘membrane bones’ develop from mesenchymal membranes.

Question 26

Endocondral ossification

Answer 26

Bones develop as hyaline cartilage, know as cartilage replacement bones.

Question 27

Epiphyseal plates

Answer 27

Elongation/ bone lengthening occurs here.

Question 28

Tribecular bones.

Answer 28

Spongy bone

Has lamellae but not osteons.

Question 29

Compact bone interior.

Answer 29

• central Haversian canal
• perforating Volkmans canals connect them
• these canals lined by endosteum
• arteries veins nerves run through these canals