Bones Flashcards
What is the extracellular matric of bone made of?
Made of calcified material and Collagen type I
Clacification = build up of Calcium
What are the cell types present in bones?
- Osteoprogenitor cells → stem cells derived from mesenchymal cells
- Osteoblasts → derived from osteoprogenitors, synthesize the organic components of ECM
- Osteocytes → dervied from osteoblasts, found in lacunae
- Osteoclasts → derived from osteoprogenitor cells, big round multinucleated cell, involved in bone resorption (remodelling) to provide Ca to the blood
Why are osteoclasts multinucleated?
They need to produce lots of enzymes to breakdown bone
- To do so, need lots of DNA for quick transcription
What is the ground substance of the bones?
Proteoglycans
Glycoproteins → sialoprotein, osteocalcin
What minerals are found in the ECM of bones?
Crystals of hydroxyapatite → Ca10(PO4)6(OH)2)
*Lots of Ca in bones
How can bones be prepared for microscopic visualisation?
Requires special technique because glass blade would break
Special technique = decalcification → 5% nitric acid or EDTA treatement (takes Ca out of the bones)
*Gives rubber material
What are the 3 ways of classifying/defining bone?
- Gross Appearance:
- compact
- cancellous (spongy) - Microscopy Appears
- woven (immature) → spongy bone
- lamellar (mature) → compact bone - Development Appear
- intramembranous → within a membrane, sheath of mesenchymal cells become a sheath of bone → sheaths fuse together eventually (flat bones → ex: skull)
- endochondral → formed from pieces of cartilage
What are the parts/structure of compact bone?
outside → inside (bone marrow):
1. Periosteum → Fibrocytes + Osteoprogenitors
2. Outer circumferential system → parallele to periosteum, osteocytes struck in bone ECM
3. Haversian system + Interstitial system
4. Inner circumferential system → parallel???? NOT????? , layer of osteocytes
5. Endosteum → hard to see because 1 layer of very flat cells, closest to bone marrow, osteoprogenitor cells + osteoblasts
What shape do osteocytes appear to have? why?
Have spider-like projection called cellular processes that connect osteocytes between each other and connect to Volkmann’s canals to have access to nutrients and reject organic wastes
(though gap junctions)
What is a Haversian system? What are its characteristics and roles?
Haversian lamellae = Haversian system
Also called Osteon
- Perpendicular to periosteum
- Lengthwise with the bones
- Different haversian systems are connected by Volkmann’s canals
- Nerves and blood vessels run through Haversian canal in the middle of each Haversian system
- Composed of osteoblasts (at surface of haversian canal) and osteocytes
What is Volkmann’s canal?
They connect Haversian systems
- Run perpendicular to muscles
- Have blood vessels, nerves, lymphatic vessels
Describe the Priosteum as a layer?
Connective tissue sheath surrounding a compact the bone
What is the structure/the components of Trabecular bones?
*Trabecular bones = spongy bones
- Surrounded by osteoblasts (on the outside making the ECM)
- Osteoclasts are also found on the outside (almost only seen in trabecular, not in compact)
- Osteocytes trapped inside the ECM
- Equivalent of flat bones??????????????
What are interstitial systems?
- Not circle
- Old haversian systems degrading and turning over
What is the orientation of the type 1 collagen in the bones?
→ Forms alpha helices lengthwise with the muscle
Gives strength to the muscle