Lecture 4 : Bone Tissue and its Microscopic Structure Flashcards
1. Describe the microscopic structure of bones (and how that reflects function) 2. Describe how bone maintains homeostasis. 3. Describe common bone pathologies (e.g. osteoporosis)
What are the types of cells found within bone?
Osteocytes, Osteoblasts, Osteoclasts and Osteogenic.
Osteoclasts vs Osteoblasts
Osteoblasts secrete bone matrix, can be considered the formers of bones. While Osteoclasts recycle and ‘destroy,’ bone matrix.
What do osteocytes do?
Osteocytes maintain bone shape and control the activity of osteoclasts and osteoblasts.
How is bone homeostasis controlled?
Bone homeostasis, density, is regulated through the activity of osteoblasts and osteoclasts. For an adult human osteoblast activity = osteoclast activity.
What is osteoporosis and osteopetrosis?
Osteoporosis is a condition where osteoclast activity > osteoblast activity, resulting in low bone density. While osteopetrosis is when osteoblast activity > osteoclast activity, resulting in high bone density.
What are the two components of bone? What percentage?
The cellular component and extra cellular component.
2% cellular and 98% extracellular matrix.
What is the extracellular matrix composed of?
Inorganic and organic material. 66% inorganic and 33% organic.
What is the organic component of bone, what happens if it is removed?
The organic component is a protein called collagen. If it is removed the bone becomes brittle as it lacks collagen which gives resists tension. There are also some proteoglycans.
What is the inorganic component of bone, what happens if it is removed?
The inorganic component is mostly minerals and calcium. One of these calcium molecules is called hydroxyapatite. If it is removed the bone becomes bendy as it lacks the hard brittle inorganic component.
What two types of microscopic bone structure are there and what bone tissue type it related to.
Osteon - Compact
Trabecular - Cancellous
They are both made of the same things just structure differently.
What are the components of osteon bone structure?
A central canal which contains blood vessels and nerves. Surrounding this is concentric lamellae in a cylindrical shape. Inbetween lamellae are lakes of osteocytes called lacunae. Linking all the lacunae up is a structure called canaliculi.
What is the periosteum?
The outer tissue of all bones except at articular surfaces. So usually only on compact bone.
What are the types of lamellae, where are they found?
Circumferential lamellae found surrounding all of the osteons as a whole. Interstitial lamellae found between osteons. Finally, concentric lamellae, they surround individual osteons.
What is the purpose of osteon?
Because compact bone is dense they provide pathways for nutrients to get to cells.
What is lamellae made of? What function does this give it?
Collagen, therefore lamellae is resistant to tension.
