Bone Flashcards
What is the name of the cells that develop into osteocytes?
Osteoprogenitor cells –> Osteoblasts –> osteocytes
What is the difference between osteoblasts and osteoclasts?
Osteoblasts are the cells responsible for formation of bone, while osteoclasts are responsible for breaking down bone.
What is present in the extracellular substance of bone?
Present in the EC substance of bone is:¨
- Calcium phosphate (70%).
- Appears as hydroxyapatite crystals (40x25x3 nm, between and within collagen fibrils and also in the ground substance) - Collagen type 1
- Ground substance which is called osteoid in bone
- Proteoglycan
- Glycoproteins
What are some common glycoproteins present in bone?
Some common glycoproteins present in bone are:
- Osteonectin
- Osteocalcin
- Osteopontin
- Bone sialoprotein 2
- Proteases, alkaline phosphatase (enzymes)
- Bone morphogenetic proteins
What is the function of osteonectin?
Osteonectin binds crystals to collagen.
What is the function of osteocalcin?
Osteocalcin binds ca and participates in mineralization
What is the function of osteopontin?
Osteopontin binds cells with ground substance
What is the function of Bone sialoprotein 2?
Bone sialoprotein 2 strongly promotes mineralization.
What are the function of the enzymes proteases and alkaline phosphatase?
These enzymes participate in mineralization and bone modeling
What is the function of bone morphogenetic proteins?
Bone morphogenetic proteins promote differentiation of osteoblasts –> induce the formation of new bones
What is the form of osteoprogenitor cells?
Osteoprogenitor cells are spindle-shaped (like a spider)
What is the main function of osteoprogenitor cells?
Osteoprogenitor cells are active in fetal bone development. In mature bone, where there is no active new bone-development or remodeling, the osteoprogenitor cells become flattened and spindle-shaped cells closely applied to the bone surface (in the periosteum, vascular canals, and endosteum), where they are sometimes referred to as inactive osteoblasts.
What is the form of osteoblasts and is their cytoplasm basophilic or acidophilic?
Osteoblasts are cuboidal in shape and has a basophilic cytoplasm
What is the main role of the RER and Golgi in osteoblasts?
The RER and Golgi in osteoblasts are responsible for producing components of the extracellular substance and control its mineralization.
What is the main function of osteoblasts?
Osteoblasts are very active in fetal bone development and in mature bone repair and remodeling.
Where are the osteoblasts found in bone tissue?
Active osteoblasts are found in areas of remodeling and repair. Inactive osteoblasts are found in the endosteum and vascular channels.
What happens to the osteoblasts as the bone formation and remodeling processes come to an end?
The osteoblasts are then transformed into osteocytes
What form do osteocytes have?
Osteocytes are flattened and have a large nucleus.
How are the osteocytes interconnected to each other?
The osteocytes have long processes with gap junctions that interconnects the osteocytes to each other.
Which spaces do the osteocytes and their processes occupy in the extracellular substance of bone?
The non-mineralized spaces in EC substance. The osteocytes occupy lacunae and their processes occupy bone canaliculi.
Why is the diffusion of substances possible in osteocytes despite the fact that it is surrounded by the mineralized walls of lacunae and canaliculi?
Between the osteocytes and the mineralized walls of lacunae and canaliculi, there is a thin layer of fluid that is highly hydrated and non-mineralized.
What are the main functions of osteocytes?
Osteocytes participate in bone remodeling and in keeping the calcium balance in body fluids.
What are the three main types of osteocytes?
There are three types of osteocytes:
- Quiescent (resting) osteocytes.
- Formative osteocytes
- Resorptive osteocytes