Human Anatomy - Bone tissue (remodelling, histology, growth, disorders)

Question 1

In the healthy adult, the rates of bone _____ equal the rate of bone _______.

Answer 1

Resorption/deposition

Question 2

Spongy bone in the skeleton is entirely replaced every ____ years; compact bone every ___ years.

Answer 2

3-4

10

Question 3

Bone is continuously remodeled for two reasons. These are?

Answer 3

1 - To maintain constant concentration of calcium and phosphate
2 - In response to mechanical stress

Question 4

Bones that undergo more ____ are remodeled faster than their less ______ counterparts.

Answer 4

Stress

stressed

Question 5

Describe osteoprogenitor/osteogenic cells.

Where are they found?

Answer 5

Undifferentiated cells
Can divide to replace themselves and become osteoblasts.
Found in the inner layer of the periosteum and endosteum.

Question 6

Describe osteoblasts. What is their function? When do they differentiate into osteocytes?

Answer 6

Bone forming cells
Form matrix and collagen fibres and initiate calcification.
Cannot divide.
Once the osteoblasts surrounds itself with its secretions, becomes an osteocyte.

Question 7

Describe osteocytes.

Answer 7

Mature cells that no longer secrete matrix.
Maintain the daily metabolism of bone (exchange of nutrients and wastes with the blood).
Do not undergo cell division.

Question 8

Describe osteoclasts.

Answer 8

Cells with a ruffled border.
Bone degrading cell.
Giant cell with many nuclei.

Question 9

How do osteoclasts degrade bone?

Answer 9

Secrete concentrated HCl and release lysosomal enzymes.

Question 10

Compact bone surrounds the ______ and spongy bone lines the _____ _____.

Answer 10

Diaphysis (shaft)

Marrow cavity.

Question 11

What is the functional unit of bone?

Answer 11

Osteon

Question 12

What is a haversian canal? What is another name for it?

Answer 12

Canal that allows blood vessels and nerves to go through.
Supply nutrients and remove wastes.
Central canal.

Question 13

What surrounds the central canals?

Answer 13

Lamallae

Question 14

What are lamellae?

Answer 14

Rings of collagen fibres that impart strength when calcified.
These are found in alternate arrangements.
Clockwise, then counterclockwise.

Question 15

What are circumferential lamellae?

Answer 15

Lamallae surrounding the bone, with the same anti-directional pattern.

Question 16

What is the advantage of the anti-directional pattern?

Answer 16

Provides strength against torsional strain, preventing twisting injuries.
Inhibits crack propagation.

Question 17

All osteons are arranged ______. They act as weight bearing pillars. This organization prevents _______ and ______. Circumferential lamellae function to resist ______.

Answer 17

Longitudinally
Tension and compression
Torsion

Question 18

How is the periosteum attached to bone?

Answer 18

Perforating collagen fibres

Question 19

What is the outer layer of the periosteum?

What is the inner layer?

Answer 19

Outer - dense irregular connective tissue

Inner - osteogenic layer (fibrous)

Question 20

_______ _____ run at right angles to the central canal.

Answer 20

Perforating canals

Question 21

Projections of the osteocytes in compact bone run through small channels called ________.

Answer 21

canaliculi.

Question 22

What is the purpose of canaliculi?

Answer 22

Projections of osteocytes run through them to link with other osteocytes to share nutrients and remove wastes along the osteon.

Question 23

Spongy bones do not have true ______. However, they still have _________ and _________, as well as _______ in terms of cells.

Answer 23

Osteons

Osteoblasts, osteocytes, osteoclasts.

Question 24

What are interstitial lamellae. Where are they located?

Answer 24

Part of lamellae left over from bone remodeling process.

Located in compact bone.

Question 25

Histology of spongy bone:
Found in ends of _____ bones and _____ flat bones.
Latticework of thin plates of bone called ________ are oriented along lines of ______.
Spaces in between the struts of _______ are filled with ______ bone marrow where blood cells develop.
No true ______.

Answer 25

Long, inside
trabeculae, stress
trabeculae, red bone marrow
osteons

Question 26

Activity of the epiphyseal plate is the only way the diaphysis can increase in ______.

Answer 26

length

Question 27

Cartilage cells are produced by mitosis on the _______ side of the growth plate.

Answer 27

epiphyseal

Question 28

Cartilage cells are destroyed and replaced by bone on the _______ side of the growth plate.

Answer 28

Diaphyseal

Question 29

Between the ages of ____, the epiphyseal plates close.

This is because _______ cells stop dividing and ____ replaces the cartilage at the ________ line.

Answer 29

18-21
Cartilage
Bone
epiphyseal

Question 30

Fetal skeleton is primarily _______ _______ and, as the child grows, it gets replaced by _____.

Answer 30

Hyaline cartilage

bone

Question 31

If you break a bone during growth at a growth plate region, this will affect what?
Why does this generally not occur?

Answer 31

Affect bone growth and length

Not common since skeletons at this age are more malleable.

Question 32

What is the process of bone growth in terms of length?

Answer 32

As the bone grows, cartilage cells continue to divide towards the epiphyseal side, to lengthen the bone.
As this occurs, cartilage on the diaphyseal side is replaced with bone.
To retain the correct shape, bone is resorbed by osteoclasts.
Cartilage keeps being formed until the age of 18-21. After this, bone replaces it and the growth plate starts to fuse.

Question 33

Describe osteoporosis.
Who does it affect?
What treatments are available?

Answer 33

Low bone mass where bone resoprtion outpaces bone deposition, leading to porous bone.
Occurs most often in women after menopause.
Treatment:
Use estrogen hormone replacement therapy
Calcium supplementation
Exercise - use it or lose it