Chapter 6: Osseous Tissue and Bone Structure. The Skeletal System. Skeletal system includes: bones of the skeleton cartilages, ligaments, and other connective tissues that stabilize the bones. Skeletal System. Functions: 1 . Support : framework & structure of body
1. Support: framework & structure of body
2. Storageof minerals and lipids
Minerals: calcium and phosphate
- for osmotic regulation, enzyme function,
Yellow marrow: triglycerides
3. Blood cell production: all formed elements
- red marrow: stem cells hematopiesis
4. Protection: surround soft tissues
5. Leverage for movement:
- levers upon which skeletal muscles act
- Extra bones in sutures of skull
All bones consist of 2 types of bone tissue
- solid, dense bone, makes up surfaces and shafts
- meshy, makes up interior of bones, houses red marrow in spaces
Table 6–1 (2 of 2)
- Hollow shaft of compact bone
- connection between two bones, surrounded by CT capsule, lined with synovial membrane
Joint cavity filled with synovial fluid to reduce friction on articular cartilage
-no cell division
-located in lacunae between layers of matrix called lamellae
-canaliculi link lacunae to each other and blood supply
-osteocytes linked to each other via gap junctions on cell projections in canaliculi:
- allow exchange of nutrients and wastes
1. To maintain protein and mineral content of matrix
2. Can also participate in bone repair:
-become stem cell like when broken free of lacuna
LM X 362
3. Osteoprogenitor Cells – mesenchymal cells
- bone stem cell that produces daughters
- daughters become osteoblasts for repair and growth
- located in endosteum and inner periosteum
- large, multinuclear
- derived from monocytes (macrophages)
- perform osteolysis =
- digest and dissolve bone matrix
- release minerals:
1. For use in blood or
2. Recycling during bone remodeling
Osteocyte: Mature bone
cell that maintains the
bone cell that secretes
Stem cell whose divisions
cell that secretes acids and
enzymes to dissolve bone matrixCells located in Bones
How would the strength of a bone be affected if the ratio of collagen to hydroxyapatite increased?
Strength increases, flexibility increases.
Strength increases, flexibility decreases.
Strength decreases, flexibility. decreases.
Strength decreases, flexibility increases.
If the activity of osteoclasts exceeds the activity of osteoblasts in a bone, how will the mass of the bone be affected?
stable mass, but re-positioned matrix
mass will not be affected
- Dense irregular CT
Figure 6–9 (Step 1)
Figure 6–9 (Step 2)
Figure 6–9 (Step 3)
Figure 6–9 (Step 4)
Figure 6–9 (Step 5)
Figure 6–9 (Step 6)
Figure 6–9 (Step 2)
During intramembranous ossification, which type(s) of tissue is/are replaced by bone?
fibrous connective tissue
mesenchymal connective tissue
de novo synthesis
cells brought with via the nutrient artery
cells of the inner layer of the perichondrium
chondrocytes from the original model
A child who enters puberty several years later than the average age is generally taller than average as an adult. Why?
Epiphyseal plates fuse during puberty.
Bone growth continues throughout childhood.
Growth spurts usually occur at the onset of puberty.
All of the above.
- Complete mineralization takes ~1 week
** These factors are controlled by hormones to regulate blood calcium levels
- decrease storage
- increase absorption
- From food, for mineralization of matrix
- From kidneys, for absorption of calcium and phosphate
- From food, for collagen synthesis and osteoblast differentiation
- From carotene in food, for normal bone growth in children
- From food, for synthesis of osteoid proteins
- From pituitary gland, for protein synthesis and cell growth
- From thyroid gland, for cell metabolism and osteoblast activity
- From gonads, for epiphyseal closure
- From thyroid gland AND
- too much GH after closure, bones don’t
grow but all cartilage does
- ribs, nose, ears, articular cartilage
3. Pituitary Dwarfism:
- not enough GH, bones fail to elongate
- lack of Vit. C
- causes low collagen content, reduced bone
mass, bones brittle
- lack calcitriol, osteoid produced but
not mineralized, bones flexible
-Called Rickets in children and leads to
A seven-year-old child has a pituitary tumor involving the cells that secrete growth hormone (GH), resulting in increased levels of GH. How will this condition affect the child’s growth?
The individual will be taller.
The individual will be shorter.
Growth of the individual will be erratic and slow.
Excessivegrowth will be limited to axial skeleton.
Joints become fused, preventing movement.
Bones are brittle and break under body weight.
Bones are flexible and bend under body weight.
Motor skills are impaired.
What effect would increased PTH secretion have on blood calcium levels?
higher level of calcium
lower level of calcium
uncontrolled level of calcium
no effect on blood calcium, PTH effects calcium in the bones
by inhibiting osteoclast activity
by increasing the rate of calcium excretion at the kidneys
by increasing the rate of calcium uptake by intestinal cells
1 and 2
Figure 6–15 (Step 1)
Figure 6–15 (Step 2)
Figure 6–15 (Step 3)
Figure 6–15 (Step 4)
1. Osteopenia = reduction in bone mass
2. Osteoporosis = reduction in bone mass that compromises function
SEM X 25
(b) Spongy bone in osteoporosis
SEM X 21
Testosterone levels decline in post-menopausal women.
Older women tend to be more sedentary than older men.
Declining estrogen levels lead to decreased calcium deposition.
In males, androgens increase with age.