Bone LS, Bone TS- discussion, viva

Bone:

1. What is bone?
• Bone is a specialized connective tissue.
2. What are the components of bone?
• Bone consists of cells (osteoblast, osteocyte, osteoclast), fibers and extracellular matrix.
• Extracellular matrix- 
• organic (coarse type I collagen fibers, sulfated glycosaminoglycans, hyaluronic acid, glycoproteins
• inorganic- calcium and phosphate together form hydroxyapatite crystals
3. Why is bone hard?
• Bone is hard because of mineral deposition in the matrix. The hydroxyapatite crystals with collagen fibers makes the bone hard, durable and strong.
4. What are the functions of bone?
• Bone is remodeled continuously due to mechanical stress, bone thinning due to age, fracture healing
• Calcium and phosphate are released into blood when needed to maintain proper levels
• Calcium is necessary for muscle contraction, blood coagulation, cell membrane permeability, transmission of nerve impulses
5. What are the functions of the bone cells?
• Osteoblast- synthesize, secrete and deposit osteoid (uncalcified without minerals)
• Osteocytes- mature cells trapped in bone matrix
• Osteoclasts- large multinucleated cells, responsible for resorption (renew or restructure), remodeling of the bone and bone repair

Bone Longitudinal Section:

1. What is the arrangement of bone components in LS of bone?
• Haversian canals coarse longitudinally with parallely running lamellae, lacunae, canaliculi
2. What is the function of Haversian canal and Volkmann's canal?
• Nutrition to the bone is supplied through blood vessels present in the Haversian canals and Volkmann's canals. Along with blood vessels, nerves and lymphatics are also present
3. What is a lamella, lacuna, canaliculi?
• Lamella- thin plate of bone matrix 
• Lacuna- space lodging osteocyte
• Canaliculi- tiny canals radiating from lacuna, penetrate lamellae and communicate with other canaliculi. They lodge the cytoplasmic processes of osteocytes which communicate with cytoplasmic processes of other osteocytes.

Bone Transverse Section:

1. What is osteon/ Haversian system?
• One Haversian system consists of Haversian canal with neurovascular structures in the center surrounded by concentric lamellae
2. What are the different types of lamellae?
• Concentric lamellae- lamellae surrounding the Haversian canal
• Interstitial lamellae- lamellae present between the various osteons
• Inner circumferential lamellae- lamellae present surrounding the bone marrow/endosteum
• Outer circumferential lamellae- lamellae present deep to the periosteum
3. What is periosteum?
• Periosteum is the connective tissue which surrounds the bone
• It has two layers outer fibrous layer and inner cellular layer
• Outer fibrous layer- formed by collagen fibers and fibroblasts
• Inner cellular layer- formed by the osteoprogenitor, osteoblast cells
4. What is a lamella, lacuna, canaliculi?
• Lamella- thin plate of bone matrix 
• Lacunae- spaces present between adjacent lamellae lodging osteocytes
• Canaliculi- tiny canals radiating from lacuna, penetrate lamellae and communicate with other canaliculi. They lodge the cytoplasmic processes of osteocytes which communicate with cytoplasmic processes of other osteocytes.
5. What is Haversian canal and Volkmann's canal?
• Haversian canal- Central canal of the osteon running longitudinally which transmits blood vessels, nerves and lymphatics to provide nutrition to the bone
• Volkmann's canal- communicating channels between the Haversian canals, periosteum and endosteum
6. What are Howship's lacunae?
• They are eroded shallow depressions which lodges osteoclasts