ANATOMY - BONES Flashcards
How are bones classified on the basis of shape?
- long bones
- short bones
- flat bones
- irregular bones (e.g facial bones)
Give examples of long bones
Humerus , femurs , metacarpals
What defines a long bone?
They must be tubular ( length > breadth )
Give examples of short bones.
Vertebrate, carpal bones, tarsal bones
What defines a short bone?
Must be cube shaped
Have no medullary cavity
Give examples of flat bones
Sternum
Scapula
Skull
What is the general function of flat bones?
- protection e.g skull
- attachments for muscle e.g scapula
What is compact bone?
- Solid mass
- It forms the outer covering of bones
What is spongy bone?
- it is found inside compact bone.
- composed of a branching network of trabeculae
What is found in the spaced between trabeculae in spongy bone?
Red marrow
Yellow marrow
What is the epiphysis of a long bone?
The ends
What is the diaphysis of a long bone?
The shaft
What is the epiphyseal plate?
The growth plate during childhood which allows bone to increase in length
Hyaline cartilage is present until growth stops
What is the epiphyseal line?
It is formed from the bone fusing ( epiphyseal plate disappearing )
- forms around age 18-21
- no more growth happens
What is the medullary cavity ?
A hollow cavity in the centre of the diaphysis containing yellow and red marrow
Do long bones have a good blood supply?
Yes.
They have nutrient arteries and veins which enter//leave at characteristic locations
Where is the nutrient foreamen usually located on long bones?
Diaphysis
What are the membranes of a long bone?
Periosteum
Endosteum
Describe the periosteum
- on external surface of long bones
- continuous with articulate cartilage
- has perforating fibres
- tendons, joint capsules, ligaments attached to periosteum.
What is the Endosteum ?
The internal surface of bones, surrounds medullary cavity
How are trabeculae in the spongy bone of long bones orientated?
They are aligned along stress lines
What is the difference between compression and tension On bone?
Compression is when the bone is being squashed
Tension is when the bone is being stretched
What is the chemical composition of a bone?
1/3 organic components
2/3 inorganic mineral salts
What are the organic components which make up bones?
Cells, fibers, collagen, organic substances
What kind of cells are found in bone?
Osteoblasts and osteoclasts
What is the main kind of inorganic salt found in bones and what is the function?
Calcium
Resists compression by hardening bone
What is ossification?
Osteogenesis / bone tissue formation
What are the two methods of ossification?
- intramembranous ossification
- endochondral ossification
What is the first model of the bone that is laid down?
A mesenchymal model (simple version of the adult bone)
What bones are formed by intramembranous ossification?
Skull bones
clavicle
How is intramembranous ossification carried out?
- takes place in connective tissue membrane
- the mesenchymal model is turned directly into bone without becoming cartilage first
Describe steps of endochondral ossification.
- A bone collar forms around hyaline cartilage model
- Cavitation of hyaline cartilage within the cartilage model happens
- Internal cavities invaded by periosteal bud, spongy bone is formed
Does the epiphyseal plate maintain a constant ethickness, even as the bone is growing?
Yes
What happens to the epiphyseal plates at age 18-21?
They becomes thinner
Cartilage stops growing
They are replaced by bone tissue
Epiphysis and diaphysis are fused
When can bone atrophy occur?
When stress on the bone diminishes
Where does bone deposition and removal happen?
Periosteal and endosteal surfaces
What cells carry out bone deposition?
Osteoblasts
What cells carry out bone resorption?
Osteoclasts
Describe the process of endochondral ossification
- Hyaline cartilage model of skeleton laid down in embry
- Bone collar formed around cartilage by osteoblasts
- Cavities form in the hyaline cartilage within the model (by chondrocytes dying)
- Periosteal blood invades the cavities and spongy bone is formed
- Medullary cavity formed
- Secondary ossification centres form in epiphyses
- Epiphyses are ossified, hyaline cartilage now only remains in epiphyseal plates and articulate cartilage
What hormone stimulates the epiphyseal plates?
Growth hormone
What are the stages of healing a fracture ?
- Hematoma forms
- Fibrocartilagenous calllus forms
- Bony callus forms by endochondral ossification
- Bone remodelling
- Compact bone formation
What is a simple fracture?
The skin is not broken
What is a compound fracture?
Bone breaks the skin
A risk of infection
What is a compression fracture?
When the bone is crushed
Common in porous bones
What is a comminuted fracture?
Bone fragments into 3+ pieces
Common in older people who have more brittle bones
What is a spiral fracture?
A ragged break, at an oblique angle cause by excessive twisting forces on the bone
- a common sports fracture
What is an epiphyseal fracture?
Epiphysis separates from diaphysis along epiphyseal plate
- if it isn’t treated carefully, growth will stop
What is a depressed fracture?
When the broken bone is pressed inwards
A typical skull fracture
What is a Greenstick fracture?
Bone broken incompletely - like a twig (one part broken the other part bent)
- common in children whose bones have a more organic matrix & are more flexible than adults bones
Who is osteoporosis most common in ?
Post menopausal women
What is the purpose of red bone marrow?
Form blood cells
What is the purpose of yellow bone marrow?
Store fat in adults
