Bones Flashcards
Name the 4 main functions of bone
- Weight bearing/support
- Protection (e.g. brain/spinal cord)
- Mineral store
- Blood formation
Name the 6 different classification of bone found in the body
- Flat
- Short
- Sesamoid
- Sutural
- Irregular
- Long
Give an example of a flat bone
frontal bone of the skull
Give an example of a short bone
Carpal (in the wrist)
Give an example of a sutural bone
Skull bones
Give an example of an irregular bone
Vertebrae
Give an example of a long bone
Fermur
Name the two different TYPES of bone
- Compact bone
2. Spongy bone
Are bones vascular or avascular?
Vascular
Name the cavity found in the middle of long bones and note the type of marrow found within this cavity
The medullary cavity is found within the shaft of long bones and it is filled with yellow marrow
Name the membrane with covers the OUTSIDE of bones
periosteum
Name the membrane that lines the INNER medullary cavity of bones
Endosteum
Name the distinctive organisational structure that makes up COMPACT bone
Osteons (or Haversian systems)
What would you find in the centre of an osteon?
A Haversian canal
As well as the Haversian canal, osteons have a second horizon canal. What is the name of this horizontal canal and what is its function?
Volkmann’s canals connect osteons together
Name the three alternative names for spongy bone
- Cancellous bone
- Trabecular bone
- Diploe bone
What is spongy bone made up of?
A network of lamellated trabeculae filled with bone marrow (No Harversian systems!)
In spongy bone, what does the orientation of the lamellate trabecular reflect?
The main direction of the mechanical forces exerted onto the bone
Name the three cell types found in bone
– Osteoclasts
– Osteoblasts
– Osteocytes
Name the two components of bone
Bone cells (osteoclasts, osteoblasts & osteocytes) & extracellular bone matrix
What is bone matrix made of?
45% Hydroxyapatite crystals
35% Collagen (Type I)
20% Water
The bone matrix (a major component of bones) contains 45% hydroxyapatite crystals. What functions does hydroxyapatite crystals play?
- Make bone stiff & able to support structures
- High strength under compression (like concrete)
The bone matrix (a major component of bones) contains 35% collagen type I. What functions does collagen type I play?
- Gives bone some flexibility & reduces risk of fracture
* High strength under tension (like steel)
True or false, bone is a dynamic tissue
true! It is constantly being broken down and remodelled
Which bone cell type breaks down & reabsorbs bone?
Osteoclasts
Which bone cell type forms new bone?
Osteoblasts
What do osteoclasts look like under a microscope?
Large multinuleated cells
What are osteoclasts derived from?
Haematopoietic stem cells (like macrophages)
Where in the bone would you find an osteoclast?
On the surface of bone cells
How do osteoclasts break down bone?
By releasing acids which demineralise bone
What is the primary function of an osteoclast?
To reabsorb bone
What exists between anosteoclast and the bone surface?
Bone matrix and a ruffled border
What is left once a section of bone matrix has been reabsorbed by an osteoclast?
Howships’s Lacunae
What is the function of an osteoblast?
BLAST out bone matrix (osteoid (the unmineralised matrix) and initiate calcification)
What is an osteoblast and where does it come from?
Osteoblasts are immature bone cells created from osteoprogenitor cells in the periosteum and endosteum
What do osteoblasts become once they are surrounded by the bone matrix?
Osteocytes
Where can you find osteocytes?
Inside lacunae (small cavities within the bone matrix)
Name a distinctive feature of osteocytes which allow inter-osteocyte communication
Osteocytes have many long processes which lie within structures called canaliculi (canaliculi connect lacunae to each other which allows communication between cell)
What is the function of osteocytes?
To maintain the bone matrix & sense mechanical forces
Give a basic description of osteoporosis
Osteoporosis- more reabsorption of bone takes place than formation. This causes spongy bone to have much thinner trabeculae which weakens the bone and makes it more likely to fracture.
Give a basic description of Paget’s disease
- there is an increased rate of bone resorption and formation which causes deformations
Give a basic description of osteopetrosis
There is a decrease in the resorption of bone so bone becomes very dense and hard. It can cause bone deformation, growth issues, an increased risk of fractures and neurological deficits (such as blindness and deafness if bone compresses nerves)
At which points in life does bone mass increase, plateau and decrease?
- Bone mass increases during childhood, plateaus during puberty and falls after menopause due to a loss of oestrogen.
Why does a decline in oestrogen cause bone mass to decline?
The less oestrogen there is, the more bone is removed by osteoclasts
What happens to bone mass in astronauts in space or people on bed rest and why?
Weightlessness (astronauts) or bed rest causes significant bone loss because there is less load exerted on them
Why do athletes generally have a higher bone marrow density?
Because they have put an increased mechanical load on their bones compared to the average person
Which sport would be more effective at increasing & maintaining bone density and why; running or cycling
Resistance & high impact sports are particularly effective in maintaining or increasing bone mass due to the high mechanical load placed upon bones (e.g. running more effective than cycling)
What is meant by the term ossification?
Bone formation
Name the two different types of ossification and describe how they are different
- Endochondral ossification (most common type – it encompasses long bone growth)
- Intramembranous ossification (involves flat bones of skull, mandible, maxilla, but also long bones)
Describe the process of endochondral ossification
- Bone forms as a cartilage ‘model’ first
- Blood vessels begin to invade cartilage
- Ossification centres form- the primary ossification centre forms first in the shaft of the developing long bone.
- Secondary ossification centre’s form in the epiphyses (ends) of the long bone
- The cartilage surrounding the ossification centres is slowly replaced with bone
- Cartilage remains in epiphyseal growth plate
- The growth plate eventually ossifies
Describe the process of intramembranous ossification
- No cartilage involvement
- Mesenchymal stem cells develop into osteoprogenitor cells in the blood vessels & bone marrow
- The osteoprogenitor are found in the two membranes that cover developing bone (periosteum and endosteum)
- Osteoprogenitor cells then mature into osteoblasts ( which then start depositing bone matrix)
Which type of ossification would you find in;
a) Children
b) Adults
a) Endochondral
b) Intramembranous
What is the name given to bone growth that increases the diameter o bone?
Apositional bone growth
What is the name given to bone growth that increases the length of bones from the epiphyseal growth plate?
Interstitial growth
