5 amazing news about our skeleton
The skeleton of an adult has 206 bones
It's hard to believe it, but it's true: the skeleton of an adult has no less than 206 bones, so there are 26 bones in the spine (including 24 vertebrae), 25 bones in the bones. sternum (including 12 pairs of ribs), 64 bones in the upper limbs (humerus, clavicles, phalanges ...) and 62 bones in the lower limbs (patellae, shins, femurs ...).
Bones are organized into two distinct "systems": the Axial skeleton (which can be compared to a frame) and the appendix skeleton (with arms and legs).
All animals do not have a skeleton: those who do not belong to the family of invertebrates - we find the worm, crab, snail, jellyfish ... It should be noted that, in the newborn, there are 350 soft bones - but some (including the bones of the skull) are fused during growth, until the age of 25 years.
The skeleton is formed during the third month of pregnancy
It is during the 11th week of pregnancy (the 13th week of amenorrhea) that the first bones are formed in the unborn baby.
Cartilaginous tissues - which are then enriched with bone cells - appear first in the upper and lower limbs (arms and legs). Then the spine is consolidated, the ribs are formed, the bones of the pelvis are drawn and finally, "islets cartilaginous" are set up at the level of the skull and the face to delimit the nose and chin.
From the 14th week of pregnancy (the 16th week of amenorrhea), baby's skeleton can be observed on X-rays. The bones are flexible and flexible, to promote childbirth.
source: The future mother's diaryMarie-Claude Delahaye, ed. Marabout pocket.
The skeleton regenerates
The skeleton is not fixed: it is constantly renewed, of the order of 10% per year. This "bone remodeling" is provided by two types of cells: osteoclasts (which destroy bone tissue) and osteoblasts (which re-fabricate bone tissue).
The main function of osteoblasts is to synthesize and mineralize bone tissue during skeletal growth (up to about 25 years of age), bone turnover in adults, and bone repair. throughout life.
For their part, osteoclasts - produced in the bone marrow - are responsible for bone resorption. They have a cyclic function: they alternate between migratory phases (where they move along the bone) and active resorption phases (where they degrade the bone). It should be noted that the vast majority of skeletal diseases result from an imbalance between formation and bone resorption.
source: CHU Rangueil, Toulouse
3 unusual bone diseases to know
- Theosteogenesis imperfecta (or "glass bone disease") is a rare disease: there is approximately one patient per 10,000 to 20,000 people. It is characterized by repeated fractures occurring as a result of benign trauma (eg a small fall). These fractures mainly concern the ribs, the vertebrae and the femur. The disease is genetic and hereditary.
- The Gorham-Stout disease is a rare pathology (about 200 patients in the world) that is characterized by ... a gradual disappearance of bone, slowly replaced by blood and lymphatic vessels. The most common bones affected are the shoulder, skull or pelvic girdle.
- In adults, a vitamin D deficiency can lead to "soft" bones: we talk aboutosteomalacia. Today rare, this disease is characterized by the appearance of bone pain that predominate in the pelvis, in the back (at the shoulder blades), the sacrum or the thorax.
10 digits on the skeleton to remember
- The stirrup (located in the inner ear) is the smallest bone of the human body since it measures between 2.6 millimeters and 3.4 millimeters long for only a few milligrams. Either the size of a grain of rice!
- On average, the skeleton of a cat is composed of 250 bones, while that of the whale has "only" 150. Snakes, meanwhile, can have up to 400 pairs of ribs.
- In women, the weight of the skeleton is between 3 kilos and 4 kilos. In humans, it is a little heavier: the bones weigh between 4 kilos and 6 kilos. The skeleton represents about 15% of the body weight.
- The femur is the strongest bone of the body: at equal weight, it is about 6 times stronger than steel, and the bone is able to withstand a force 35 times greater than that needed to break a concrete slab .
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