Stages of bone growth and development
- Bones continue to grow in length until approximately 25 years of age – may grow in
thickness after this time
Bone growth in length
- Bone growth in length is the addition of new bone on the diaphyseal side of the epiphyseal
growth plates.
- The epiphyseal growth plate is composed of hyaline cartilage and separates the epiphyses
from the diaphysis of the growing bones. Can be divided into 4 stages:
ZONE 1 – Resting Cartilage
- Closest to the epiphysis, made up of small, scattered chondrocytes that have low
proliferation rate
- Cells are unactive
- Is the germinal layer that supplies developing cartilage cells
- Also anchors the epiphysial growth plates to the epiphysis bone
- Matrix > cell volume → matrix allows diffusion of nutrition from blood to epiphysis to
maintain chondrocytes in deeper layers
ZONE 2 – Proliferating Cartilage
- Chondrocytes are slightly larger and are stacked like coins.
- The chondrocytes are dividing and replacing the ones that are dying at the diaphyseal side of
the epiphyseal growth plate.
- These chondrocytes produce the necessary matrix and are responsible for longitudinal
growth of the bone via active cell division.
ZONE 3 – Hypertrophic Cartilage
- Can be further subdivided into zones of:
o maturation,
o degeneration and
o provisional calcification
- Chondrocytes get bigger, remain in their columns, but they accumulate calcium, which
causes them to deteriorate, leading to cell death
- On death, calcium is released into the matrix with calcium salts
- Matrix calcification is necessary for:
o invasion of metaphyseal blood vessels,
o destruction of cartilage cells, and
o formation of bone along the walls of the calcified cartilage matrix.
- No active growth occurs in this layer; columns of cells extending toward the metaphysis are
at various stages of maturation.
- This is the weakest portion of the epiphyseal growth plate and is commonly a site of fracture
or alteration
- Bones continue to grow in length until approximately 25 years of age – may grow in
thickness after this time
Bone growth in length
- Bone growth in length is the addition of new bone on the diaphyseal side of the epiphyseal
growth plates.
- The epiphyseal growth plate is composed of hyaline cartilage and separates the epiphyses
from the diaphysis of the growing bones. Can be divided into 4 stages:
ZONE 1 – Resting Cartilage
- Closest to the epiphysis, made up of small, scattered chondrocytes that have low
proliferation rate
- Cells are unactive
- Is the germinal layer that supplies developing cartilage cells
- Also anchors the epiphysial growth plates to the epiphysis bone
- Matrix > cell volume → matrix allows diffusion of nutrition from blood to epiphysis to
maintain chondrocytes in deeper layers
ZONE 2 – Proliferating Cartilage
- Chondrocytes are slightly larger and are stacked like coins.
- The chondrocytes are dividing and replacing the ones that are dying at the diaphyseal side of
the epiphyseal growth plate.
- These chondrocytes produce the necessary matrix and are responsible for longitudinal
growth of the bone via active cell division.
ZONE 3 – Hypertrophic Cartilage
- Can be further subdivided into zones of:
o maturation,
o degeneration and
o provisional calcification
- Chondrocytes get bigger, remain in their columns, but they accumulate calcium, which
causes them to deteriorate, leading to cell death
- On death, calcium is released into the matrix with calcium salts
- Matrix calcification is necessary for:
o invasion of metaphyseal blood vessels,
o destruction of cartilage cells, and
o formation of bone along the walls of the calcified cartilage matrix.
- No active growth occurs in this layer; columns of cells extending toward the metaphysis are
at various stages of maturation.
- This is the weakest portion of the epiphyseal growth plate and is commonly a site of fracture
or alteration
