-
What are the primary functions of bone
- Mechanical Support
- Locomotion via tendons
- Protection of vital organs (skull)
- Metabolic Reservoir of mineral salts
-
Ezymatic reactions are dependent on what found in bones
Calcium
-
What do osteogenesis imperfecta patients lack
Type I Collagen
-
What are considered the support cells in the bones
Osteoblasts and osteocytes
-
Resorption and remodeling cells in the bone are
Osteoclasts
-
The matrix of the bones is made up of what two substances
- Inorganic mineral salts
- Organic materials
-
Non mineralized organic matrix is called an
Osteoid
-
The inorganic component of the bone matrix is made up of what elements
Calcium and phosphorus (Mg, K, and HCO3 minor amounts)
-
The Ca and Phosphorus form what
Hydroxyapatitie crystals alongside coll. I
-
What is the function of the surface crystals of hydroxyapatite
They form a hydration shell with water allowing ion exchange with the extracellular fluid
-
Amorphous means
Non- crystaline solid
-
The organic component of the bone matrix is made up of
- 90% Coll I and some Coll V
- Ground substance in the form of GAG's (Chondroitin sulfate, karatan sulfate, and hyaluronic acid)
-
What causes the organic matrix to stain basophilic
The abundance of Coll. I
-
Glycoproteins in bone such as osteocalcin, osteonectin, and osteopontin. As well as sialoproteins are important in the matrix for
Binding to crystals, fibers, ground substance, and cells
-
Ground substance and collagen become mineralized to form
Bone
-
What are the four different cell types in bones
- Osteogenic (Osteoprogenitors)
- Osteoblasts
- Osteocytes
- Osteoclasts
-
Osteoprogenitor (Osteogenic) cells are derived from
Mesenchyme
-
Osteoprogenitor cells can differentiate into what cells
- Fibroblasts
- Osteoblasts
- Chondrogenic cells
-
Where are the Osteoprogenitor cells found
- Lining the haversian canals
- Inner cellular layer of the periosteum
-
The bone grows only by what means
Appositional
-
Osteoblasts form
- The matrix of the bone
- - Coll I
- - GAG's
- - Glyco proteins
- - Osteoids
-
What shape are the osteoblasts
Cuboidal or columnar
-
Why do the osteoblasts stain basophilic
The extensive RER gives them a negative charge
-
How do the Osteoblasts and Ostecytes communicate
Gap Junctions
-
Alk. Phosphatase is used
As a marker in blood samples for the status of bones
-
Osteoblasts secrete vesicles into the matrix high in
- Ca
- PO4 ions
- ATPase
- Alk. Phosphotase
- Pyrophosphatase
-
What cleaves PO4 from the extracellular matrix
- Alk. Phosphatase
- Pyrophosphatase
-
What happens when the concentration of Ca and PO4 increase
They form CaPO4 and growing hydroxyapitite crystals burst the membrane of matrix vesicles
-
What surrounds osteoblasts and acts as a site of initiation
Hydroxyapatite
-
Rapid growth of hydroxyapatite crystals are deposited where
Into gap regions of collagen mineralizing the matrix
-
Osteocytes are, and perform what
- Mature bone cells
- Perform maintenance of bone matrix
-
Osteocytes are dervived from
Osteoblasts
-
What surrounds osteocytes
Lacunar space
-
What unique feature allows the Osteocytes to communicate outside the lacuna
Canaliculi
-
Through what means do Canaliculi communicate
Gap Junctions, with other osteocytes and Osteoblasts
-
What type of things are transported in the canaliculi
Ions and small molecules
-
What is found in canaliculi
- Ions
- Small molecules
- Nutrients
- Matabolites
- Extracellular Fluid
-
Osteocytes have what physical features
- Almond shaped
- reduced RER and Golgi
-
What results in the death of osteocytes
Resorption of the matrix
-
What are the three functional states of an osteocyte
- Quiescent
- Formative
- Resorptive
-
In the quiescent stage of an osteocyte
There is scant RER
-
In Formative osteocytes
There is lots of RER, deposition of osteoids in the pericellular space with the lacuna
-
Resorptive osteocytes have what organelles in abundance and perform what function
Lots of RER (making lysosomes), Golgi (removing matrix into the blood), and secretory lysosomes.
-
The pericellular space has no
Collagen fibrils
-
Osteocytic osteolysis is
Resorption stage of osteocytes when Ca is released
-
Osteoclasts are derived from
Monocytes fusing, they are large cells with 5-50 nuclei
-
Osteoclasts have abundant
- Mitochondria
- Golgi
- RER
- Lysosomes
-
Osteoclasts have a membrane that
Is ruffled on the bone side and a clear zone that demarcates the area of bone to be resorbed
-
The clear zone of an osteoclast has abundant
Microfilaments
-
Osteoclasts have what two phases of resorption
Initial dissolution of Ca salts by organic acids from PM
Subsequent enzymatic degredation of collagen by lysosomal enzymes (collagenase, Proteolytic enzymes)
-
Osteoclasts do not belong to what family
Osteogenic, made by monocytes
-
PTH has what effect on osteoblasts
- It stimulates them to release osteoclast stimulating factor causing the osteoclasts to absorb bone
- It can also affect osteoclasts directly
-
What effect does calcitonin have on osteoclasts
Reduces the bone resorption of osteoclasts
-
High calcitonin shuts off
PTH release
-
Somatotropin can have what effects when not in balance
Gigantism when high, dwarfism when low
-
What are the two types of bone on a microsopic level
- Primary - Immature or woven, first to form, abundant osteocytes, no arrangement, found in fetal and bone development
- Secondary - mature, found in adults, strong bone, replaces primary, in parallel array
-
What are the two types of bone marrow, where are they found, and what do they do
- Red - found in the sternum, ribs, ends of long bones, make blood cells
- Yellow bone - diaphyseal cavity of long bones, stores fat
-
Bone grows only by what means
Appositional
-
When the matrix is calcified it is considered
Strong bone
-
Intramembranous bone is formed in what order
- Mesenchyme
- Osteogenic cells
- Osteoblasts
- Spongy bone (trabeculae, cancellous)
- Primary bone
- Secondary bone (lamellar)
-
What two phases make up the Endochondral Ossification
- Hypertrophy and destruction of chondrocytes
- Osteogenic budding
-
When a bone is fractured what takes place
- The periosteum covers the fragments
- Hyaline cartilage follows
- Bone is formed around a callus
- Fracture is healed
-
What is the role of vitamin D in bone formation
It is necessary for the absorption of Ca from the intestines
-
Deficiency in Vitamin C, D, or phosphorus will lead to
Rickets in children osteomalacia in adults (major problem in pregnancy), child normally has bowed legs
-
Vitamin C has what function in bone formation
It is necessary for collagen formation, lack of vitamin C causes Scurvy
-
What is the role of vitamin A in bone formation
Lack of it inhibits proper bone formation, excess causes early ossification of epiphyseal plates
-
Osteopetrosis is when
There is no ruffled boarder in the osteoclasts and therefore high density of bones
-
Osteoporosis is when
There is a low bone density due to increase bone resorption, or decrease bone formation
-
Acromegaly is
An excess of GH causing gigantism affects
-
Papain can have a negative effect because
It destroys gound substance of cartilage resulting in lose of rigidity
|
|