14 Questions
What percentage of the dry weight of bone is comprised of inorganic materials?
75%
What is the main component of the inorganic materials in bone matrix?
Calcium in the form of hydroxyapatite
What happens to bone when the organic materials are removed?
It becomes more fragile
What is the function of osteogenic cells?
Bone formation and maintenance
Where are osteogenic cells typically found?
On or near all the free surfaces of bones in the endosteum and the inner layers of periosteum
What is the characteristic of osteoblasts?
Large oval cells with highly basophilic cytoplasm
What is the function of osteoclasts?
Bone resorption
What is the composition of the periosteum?
An outer vascularized dense fibrous layer and an inner osteogenic layer
What is the primary function of osteoclasts?
Bone resorption and remodeling
What is the role of alkaline phosphatase in osteoblasts?
Liberation of phosphate ions for bone mineralization
What is the characteristic feature of osteocyte morphology?
Branched shape with oval nucleus
Which organelle is responsible for the synthesis of procollagen molecules in osteoblasts?
RER
What is the purpose of the canaliculi in bone tissue?
To allow for the exchange of nutrients and waste between osteocytes and extracellular fluid
What is the characteristic feature of the border of osteoclasts?
Ruffled border
Study Notes
Definition and Composition of Bone
- Bone is a specialized type of dense supporting connective tissue composed of calcified intercellular substance, bone matrix, and bone cells.
- Bone matrix is composed of inorganic (75% of dry weight) and organic materials (25% of dry weight).
- Inorganic materials mainly consist of calcium in the form of hydroxyapatite.
- Organic materials are mostly type I collagen fibers (about 90%).
Periosteum and Endosteum
- Periosteum is the connective tissue that covers the bone, consisting of an outer vascularized dense fibrous layer and an inner osteogenic layer.
- Endosteum is a thin layer of flattened osteogenic cells and osteoblasts that lines the bone marrow cavity and spaces.
Bone Cells
Bone Formation and Maintenance Cells
- Osteogenic cells:
- Found on or near the free surfaces of bones in the endosteum and the inner layers of periosteum.
- Able to proliferate and differentiate into osteoblasts.
- Active during bone growth and repair.
- Osteoblasts (bone-forming cells):
- Large oval cells with highly basophilic cytoplasm.
- Secrete type I collagen and bone matrix proteins.
- Responsible for calcification of bone matrix (activity of alkaline phosphatase).
- Have well-developed RER, Golgi, and mitochondria with secretory vesicles containing procollagen molecules and alkaline phosphatase.
Bone Resorption Cells
- Osteoclasts:
- Large multinucleated cells (6-12 nuclei or up to 50 nuclei) derived from the fusion of monocytes.
- Have acidophilic cytoplasm and occupy pits in the bone surface (Howship's lacunae).
- Function: bone resorption and remodeling.
Osteocytes
- Oval branched cells present inside lacunae.
- Extend cytoplasmic processes through canaliculi filled with extracellular fluid and originating from lacunae.
- Maintain the calcified matrix, and death of osteocytes is followed by resorption of the matrix.
This quiz covers the definition and composition of bone, including bone cells, bone matrix, periosteum, and endosteum. It also explores the inorganic and organic materials that make up bone.
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