Human Anatomy - Bone tissue (remodelling, histology, growth, disorders) Flashcards
In the healthy adult, the rates of bone _____ equal the rate of bone _______.
Resorption/deposition
Spongy bone in the skeleton is entirely replaced every ____ years; compact bone every ___ years.
3-4
10
Bone is continuously remodeled for two reasons. These are?
1 - To maintain constant concentration of calcium and phosphate
2 - In response to mechanical stress
Bones that undergo more ____ are remodeled faster than their less ______ counterparts.
Stress
stressed
Describe osteoprogenitor/osteogenic cells.
Where are they found?
Undifferentiated cells
Can divide to replace themselves and become osteoblasts.
Found in the inner layer of the periosteum and endosteum.
Describe osteoblasts. What is their function? When do they differentiate into osteocytes?
Bone forming cells
Form matrix and collagen fibres and initiate calcification.
Cannot divide.
Once the osteoblasts surrounds itself with its secretions, becomes an osteocyte.
Describe osteocytes.
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.
Describe osteoclasts.
Cells with a ruffled border.
Bone degrading cell.
Giant cell with many nuclei.
How do osteoclasts degrade bone?
Secrete concentrated HCl and release lysosomal enzymes.
Compact bone surrounds the ______ and spongy bone lines the _____ _____.
Diaphysis (shaft)
Marrow cavity.
What is the functional unit of bone?
Osteon
What is a haversian canal? What is another name for it?
Canal that allows blood vessels and nerves to go through.
Supply nutrients and remove wastes.
Central canal.
What surrounds the central canals?
Lamallae
What are lamellae?
Rings of collagen fibres that impart strength when calcified.
These are found in alternate arrangements.
Clockwise, then counterclockwise.
What are circumferential lamellae?
Lamallae surrounding the bone, with the same anti-directional pattern.
What is the advantage of the anti-directional pattern?
Provides strength against torsional strain, preventing twisting injuries.
Inhibits crack propagation.
All osteons are arranged ______. They act as weight bearing pillars. This organization prevents _______ and ______. Circumferential lamellae function to resist ______.
Longitudinally
Tension and compression
Torsion
How is the periosteum attached to bone?
Perforating collagen fibres
What is the outer layer of the periosteum?
What is the inner layer?
Outer - dense irregular connective tissue
Inner - osteogenic layer (fibrous)
_______ _____ run at right angles to the central canal.
Perforating canals
Projections of the osteocytes in compact bone run through small channels called ________.
canaliculi.
What is the purpose of canaliculi?
Projections of osteocytes run through them to link with other osteocytes to share nutrients and remove wastes along the osteon.
Spongy bones do not have true ______. However, they still have _________ and _________, as well as _______ in terms of cells.
Osteons
Osteoblasts, osteocytes, osteoclasts.
What are interstitial lamellae. Where are they located?
Part of lamellae left over from bone remodeling process.
Located in compact bone.
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 ______.
Long, inside
trabeculae, stress
trabeculae, red bone marrow
osteons
Activity of the epiphyseal plate is the only way the diaphysis can increase in ______.
length
Cartilage cells are produced by mitosis on the _______ side of the growth plate.
epiphyseal
Cartilage cells are destroyed and replaced by bone on the _______ side of the growth plate.
Diaphyseal
Between the ages of ____, the epiphyseal plates close.
This is because _______ cells stop dividing and ____ replaces the cartilage at the ________ line.
18-21
Cartilage
Bone
epiphyseal
Fetal skeleton is primarily _______ _______ and, as the child grows, it gets replaced by _____.
Hyaline cartilage
bone
If you break a bone during growth at a growth plate region, this will affect what?
Why does this generally not occur?
Affect bone growth and length
Not common since skeletons at this age are more malleable.
What is the process of bone growth in terms of length?
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.
Describe osteoporosis.
Who does it affect?
What treatments are available?
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
