Osteoporosis

 

It is a chronic skeletal disease characterized by low bone mass and alteration of the microarchitecture of bone tissue leading to fragility and fracture risk. Osteoporosis, osteon = bone from the greek and poros = pore.

osteoporosi

Normal spongy tissue
of a vertebra
 
Spongy tissue
within an osteoporotic vertebra

 

How osteoporosis develops

Bone is a vital structure, consisting of cells, proteins and mineral salts, constantly liable to processes of destruction and renewal. Osteoporosis associated with aging occurs when the rate of bone destruction increases than the rate of regeneration that decreases.

The skeleton

It is a strong and flexible structure, consisting of 206 bones, joints able to support the body, to move it (thanks to the muscle) and to protect the internal organs: lungs, intestines.

It has the following functions: support, locomotion, protection of internal organs, storage of minerals. The bones are formed by an outer membrane of fibrous connective tissue, the periosteum, an inner layer of compact and dense fabric, and a layer of spongy tissue and they are white, with solid consistence and with high mechanical strength. They Are classified as:

- long bones: limbs, formed by a cylindrical body (dialysis) and two extremes (epiphysis)
- Short bones: vertebrae, flat skull

There are two types of bone:

  1. spongy or trabecular bone: make part of the court bones and the epiphysis of long bones covered with compact bone
  2. cortical or compact bone: it is part of the flat bones and the diaphyses of long bones

osteoporosi

Bone remodeling

Bone is a living tissue which renews itself. This process is called "remodeling".

A bone become old and worn is reabsorbed through the work of cells called osteoclasts and by osteoblasts. Osteoclasts, from the greek means "bone breaker", osteoblasts Greek word "embryo bones".

The cycle of remodeling and resorption lasts from 90 to 130 days.

The succession of cycles of bone remodeling can become unbalanced because, as we grow up with age, the osteoclasts become more active than osteoblasts. When the tissue destruction is greater than the rebuilding results in an overall loss of bone mass.

osteoclast

 



reabsorbed bone

 

 

alignment of osteoblasts
in resorption cavities


newly formed bone
in a normal subject

Remodeling balanced

Newly formed bone
in an osteoporotic

Unbalanced remodeling