BONE GROWTH & REPAIR

Bone Growth & Repair

Bone Growth & Repair

Bone Growth

Bone growth begins in embryonic life and continues until puberty. Growth in length is made ??by adding new bone diaphyseal face of the growth plate or physis

The growth plate is a disk-shaped structure which is sandwiched between the epiphysis and diaphysis. In the growth plate are two regions, a central and a peripheral. The central region is composed of hyaline cartilage which are distinguished from the epiphysis to the shaft, four zones: germinal, proliferative zone, hypertrophic zone of cartilage and calcified cartilage zone 2 . Germinal zone (layer standby or sleep) is the area closest to the epiphysis. It consists of cartilage cells isolated oval. Observed in this layer there is a strong mitosis and extracellular matrix synthesis Proliferative zone: One is composed of cartilage cells in the form of a wedge whose axis is perpendicular to the bone. These cells are arranged in columns parallel to the longitudinal axis of the bone. In this area there are also mitosis and there is a strong extracellular matrix synthesis. The cells in each column appear to divide in unison but in a asicrónica with respect to the remaining columns (Eastell & Delmas, 2003). Hypertrophic cartilage zone: this zone chondrocytes mature, they acquire a rounded shape and its size increases as you move away from the epiphysis. Calcified cartilage zone: This zone is mineralized cartilage matrix. The nucleus of chondrocytes lose chromatin (karyolysis) and vacuolated cytoplasm. Finally, these cells die and disappear so that at the end of each column there is an empty space surrounded by calcified cartilage matrix corresponds to that previously used as a chondrocyte. On this calcified matrix stromal osteoblasts diaphyseal marrow deposited woven bone (endochondral ossification type). In the course of this immature bone modeling bone is replaced by lamellar bone. The peripheral region of the growth plate area is called Ranvier. This area is a triangular section ring and outer core that surrounds the central region of the physis. The zone of Ranvier is composed of immature cells to chondroblasts and osteoblast differentiation. The first circumferential growth could contribute to the growth plate and the latter could contribute to growth in length of the diaphyseal cortex. The thickness of the bone growth is achieved by concentric subperiosteal apposition of bone tissue. The cells of the innermost layer of the periosteum differentiate into osteoblasts that deposit bone directly onto the outer surface of the diaphyseal cortical (intramembranous ossification type). Bone growth depends on genetic factors and is influenced by systemic factors (hormones) and local. The hormones involved in controlling bone growth can be divided into four groups:

Hormones needed for growth: growth hormone, thyroid hormone, insulin.

Growth-inhibiting hormones: cortisol

Hormones activating maturation: sex hormones

Vitamin D and Parathyroid Hormone Local factors that can influence growth are the nervous type and mechanical type. The mechanism by which the nervous system works on the bone growth. It has been suggested that it may intervene indirectly through control of blood ...