Bone Flashcards
What part of the body acts as a storehouse for calcium?
Bone
What does the ground substance of bone contain?
Compact bundles of Type I collagen fibers, stem cells, osteoblasts, osteocytes, osteoclasts
What is osteoporosis?
Pathology of again bone, especially in elderly women, involves loss of bone mss resulting in greatly enhanced chance of fracture
What are the two type of bone?
Compact and cancellous (trabecular)
Where is cancellous bone found?
The center or ends (medulla or epiphysis) of long bones
What are the branches in cancellous bone called which add strength to the structure?
Trabeculae
Where is compact bone found?
In the cortical areas of bones
Wha are the concentric layers of tissue in compact bone called?
Lamellae
What is found in the central region of compact bone?
Central canal (Haversion canal)
What is periosteum?
The bone surface
What are sharpey’s fibers?
Type 1 collagen running perpendicular tot he surface which connect ct to bone
What are the two layers of the periosteum?
Outer fibrous layer
Inner cellular layer
What does the outer fibrous layer of periosteum composed of?
Dense irregular CT
What does the inner (osteogenesis) cellular layer of periosteum consist of?
Osteoprogenitor (stem) cells
Osteoblasts
Osteoclasts
What is the stem cell of bone?
Osteoprogenitor cell
What is the endosteum?
A single layer of cells that adhere to all inner surfaces of bone
I.e. Line the cavity of all bones
What does endosteum contain and where is it found?
Contains no fibrous components
Found on bony trvecular, in ha version and volkmanns cannas and on surfaces lining the medullary cavity
What cells are found in the endosteum?
Osteoprogenitor cells
Osteoblasts
Osteoclasts
What is osteomalacia? (Rickets in kids)
A condition occurring when bones do not mineralized properly due to lack of vitamin D (no sunlight)
What does Vitamin D aid in the small intestine?
Absorption of calcium nod phosphorus
How can soft bones no pain be treated? (Those with osteomalacia)
Dietary vitamin D supplements or exposure of the epidermis of the skin to sunlight
What does the bone matrix consist of?
Type 1 collagen and glycosaminoglycans produced by osteoblasts
What does the ground substance of bone consist of?
Mainly hydroxyappetite crystals formed of. Combination of glycosaminoglycans and calcium phosphate
What lines the haversion canal?
Endosteum
What is the haversian system or osteon?
A system that runs lengthwise in long bone used to carry nutrients and waste products
What is the haversian system or osteon composed of?
Lamellae (rings of bone tissue) surrounding a Haversian canal
What nourishes the haversian system?
A single capillary in the Haversian canal
What are volkmann’s canal?
A canal where blood vessels and nerve fivers run from the soft tissue outside the bone to the center of the bone
What is the filopodia of osteocytes?
A long connection between osteocytes or capillary within the Haversian canal.
It is a used for exchange between cells
Where are osteoprogenitor cells found?
Periosteum and endosteum
Where are osteoblasts found?
In periosteum and endosteum
Where are osteocytes found and what is their function?
Found in lacunae to maintain matrix
Where are osteoclasts found and what is their function?
Periosteum and endosteum
Dissolve matrix
What cells can be found in both the periosteum nod endosteum?
Osteoprogenitor cells
Osteoblasts
Osteoclasts
Where are osteoprogenitor cells derived from and what do they produce?
Mesenchyme
Produce: osteoblasts
What cell shape are osteoblasts?
Cuboidal cells with basophilic cytoplasm
Where do osteoblasts becoming embedded?
Lacunae
When osteoblast becomes dormant in lacunae, what are they now called?
Osteocytes
Osteoclasts are part of what system?
The mononuclear phagocyte (macrophage-like) system
Where are osteoclasts formed from?
Blood stem cells in the marrow by several monocytes fusing together
Describe an osteoclasts
A large, multinculeated and eosinophilic (stain red?)
How do osteoclasts work?
Dissolves bone by exocytosing the contents of lysosomes
Secrete HCl and hydrolytic enzymes (e.g. Collagenase) to break down hydroxyapatite and collagen fibrils
Where are osteoclasts located t?
In a shallow indentation of bone called Howship’s lacuna
How is a new haversian system formed?
- Osteoclasts cut a cylinder followed by a capillary loop
- Osteoblasts lay down Lamellae
- Once several layers are formed, the system is complete
Explain how does intramembrnous bone forms (E.g. Skull bones)
Mesenchymal cells become osteoprogenitor cells then osteoblasts
Osteoblasts surround themselves with matrix to become osteocytes
Matrix calcifies into trabeculae with spaces holding red bone marrow
Superficial layers of spongy bone are replaced with compact bone
What is the simplified version of how intramembraous bone forms?
- Development of center of ossification
- Calcification
- Formation of trabeculae
- Development of the periosteum
What kind of development do long bones experience?
Endochondral ossification
Explain endochondral ossification
Cartilage template of bone first develops until a blood supply approaches the perichondrium
The chondrogenic layer becomes an osteogenic layer, deposits bone on the outside of the template
Cells in the center of the cartilage die, and capillaries, stem cells and osteoclasts take their place
The template is converted to bone
What do hot spots in bone scan indicate?
Areas of increased metabolic activity that may indicate cancer, abnormal healing or growth
What do cold spot indicate in bone scans?
Decreased metabolism of bone
E.g. Osteoporosis, bone infection
How are bone scans given?
Radioactive tracer substance is given intravenously
Amount of uptake of tracer is related to amount of blood to the bone
