Development and growth of bone Flashcards
What are some of the functions of bone?
Support of the body shape Systems of levers for muscle action Protection of internal organs Site of blood cell formation Mineral storage pool
What are the two mechanical properties of bone and what is responsible for these properties?
FLEXIBILITY (like a cable), due to the protein element of bone– and resistance to tension because the framework is collagen and other bone proteins (osteoid)
Pillar-like STIFFNESS, due to minerals– and resistance to compression conferred by impregnation of collagen with crystalline mineral (hydroxyapatite – a complex calcium hydroxyphosphate)
What are the two main types of bone tissue?
Woven (immature)
Lamellar (mature)
When is woven bone found in adults?
It is only found in repairing fractures
What is the technical term for the shaft of a bone?
Diaphysis
What is the technical term for the head of a bone?
Epiphysis
What type of bone is found around the outside of the bone?
Compact bone (aka cortical bone)
What is the term given to the cavity within the bone?
Medullary cavity (contains bone marrow)
What type of bone is found within this cavity?
Trabecular/spongy/cancellous bone (this is still lamellar bone)
What units are the outer compact/cortical bone arranged into? (in lamellar/mature bone)
Osteons/Haversian Systems
They have a central canal containing vessels and around the vessels you have concentric layers of bone maintained by concentrically arranged osteocytes
In what planes are these units arranged?
They are usually organised along pressure planes
What provides the main blood supply to the bone marrow?
Nutrient artery (passing through the nutrient foramen)
What are the two layers of the periosteum?
Fibrous (outer)
Cellular (inner)
The fibrous layer contains fibroblasts, while the cellular layer contains progenitor cells that develop into osteoblasts. These osteoblasts are responsible for increasing the width of a long bone and the overall size of the other bone types.
What are the main roles of the periosteum? Does it have a blood and nerve supply?
Bone growth and repair
It is vascular
It has a good sensory nerve supply
What do osteogenic cells give rise to?
Osteogenic cells (initial stem cells) –> Osteoblasts –> Osteocytes slide 17
What lineage do osteoclasts come from?
They are derived from the immune cell lineage – they are modified macrophages
At what point in fetal life does the skeleton start to develop?
6 weeks
What are the two types of ossification?
Intramembranous Endochondral (within cartilage)
Describe intramembranous ossification.
Occurs within existing vascular connective tissue
Bone matrix (ostein) is deposited around the collagen
This mineralises to form woven bone
It then remodels to form lamellar bone
Describe endochondral ossification.
Occurs within existing fetal cartilage models
Cartilage calcifies and the chondrocytes die
Periosteal osteoclasts cut channels for sprouting vessels
Osteoblasts enter with the vessels to build bone around them
List some bones in which intramembranous ossification takes place.
Skull bones
Jaw bones (mandible)
Part of the clavicle
At what point do the epiphyses ossify in a child’s wrist?
2 years
Until what point do epiphyseal plates remain cartilaginous?
Until you stop growing (ie your bones stop growing) – then the epiphyseal plates will calcify. The epiphyseal plate is where your bone grows and helps the bone to lengthen.
