Bone; Structure, Growth and Repair Flashcards
What is compact bone?
Dense bone on the cortex (Outside)
- Contains osteons
- Covered in periostium
What is spongy bone?
- Also known as trabecular, cancellous bone.
- Internal to compact bone
- Distributes loads
- Reduces bone weight
What is periosteum?
- Outer layer of bone
- In the mature adult it can be divided into;
- Fibrous outer layer
- Internal layer of osteoprogenitor cells
What is endosteum?
- Internal lining of cell surfaces
- Contains osteoblasts and osteoprogenitor cells
What is bone marrow?
Red;
- Heamopoesis; RBC made and stored
Yellow
- Fat storage
Is adipose found in the bone?
Yes, adipocytes are found in bone
What are lammellae?
Concentric layers of bone that form a unit (Osteon) in compact bone
What are osteons?
Unit of compact bone that contains its own blood supply.
Contain the lamallae of the bone
What are canaliculi?
Haversion cannels?
Little canals - osteocytes project through and connect with each other.
Involved in nutrition and communication
Whats the epiphysis?
Head of the bone.
Can be covered in articular cartilage.
Generally contains spongy bone
Whats the metaphysis?
Region where the epiphyseal growth plate is located.
In mature adults epiphyseal lines develop
What is the diaphysis?
Shaft of the bone. Contains a medullary cavity in long bones with nutrient vessels.
What are osteoprogenitor cells?
Mesodermal-Mesenchyme in origin. Develop into osteoblasts.
What are osteoblasts?
Secrete ostoid (bone ECM) once surrounded by ECM they differentiate into osteocytes
What are osteocytes?
Osteocytes maintains bone tissues
What are osteoclasts?
Osteoclasts breakdown the ECM of bone. Bone reabsorption.
Derived from macrophage/monocyte lineage.
Describe the ECM of bone;
Water
Collagen (30%, tensile strength)
Inorganic minerals; Hydroxyapetite (CaPO4, CaOH2)
What sort of forces does the lamellae structure of compact bone resist against?
Compression, tensile and torsion stresses.
Describe the type of lamellae in compact bone;
Concentric lamellae (Osteons)
Outer circumferential lamellae
Interstitial lamellae
Are lamellae found in spongy bone?
Yes, theyre irregular giving the trabecular structure.
How do osteocytes in spongy bone gain their nutrition?
Diffusion from the morrow that surrounds them
What are the two types of bone formation in growth and development (not fracture)?
Endochondral ossification
Intramembranous ossifcation
Describe intramembranous ossification;
Osteoprogenitor cells condense to form a primary ossification center in the mesenchyme.
Ostoid is deposited and a trabecular network is formed
The bone organises itself to form a compact outer shel with periosteium derived from the surrounding mesenchyme.
Describe endochondral ossification;
In the developing fetus;
1) Mesenchyme cells develop into chondrocytes.
2) Chondrocytes produce a cartilage model.
3) Primary ossification centre develops in the diaphysis region. With nutrient and blood vessels invading. Osteoclasts core out medullary cavity.
4) Secondary ossification centre develops at the epiphysis.
5) Articular and hyaline cartilage develop.
Gradients of growth factors direct chondrocytes, hypertrophies chondrocytes and deposits bone.
How do bones grow longer and wider?
Longer = Endochondral ossifcation Wider = Appositional growth (ostoid is deposited on the outside, interal bone is consumed)
