veterinary online-General OSTEOLOGY
Skeleton (skeletos, Greek. - Dried) represents a set of dense formations that develop from mesenchyme with mechanical significance. It consists of separate bones connected to each other via connective, cartilage or bone, with whom and is passive movement of the device.
The value of the skeleton. osseous system performs a number of functions, with or preferably mechanical or predominantly biological significance.Consider the features that are mostly mechanical significance. For all vertebrate characteristic internal skeleton, although there are also species that along with the inner skeleton are also more or less developed exoskeleton that occurs in the skin (bone flakes in the skin of fish). At the beginning of his appearance solid skeleton served to protect the body from harmful external influences (external skeleton invertebrates). With the development of the internal skeleton of vertebrates, he first became a mainstay and support (frame) for soft tissue. Some parts of the skeleton become levers are driven muscles, resulting skeleton acquired locomotion function. As a result of the mechanical functions of the skeleton are manifested in his ability to defend, support and movement.
Reliance achieved attaching soft tissue and organs to different parts of the skeleton. Rukh possible by the structure of the bones in the form of long and short levers connected by movable joints and set in motion by the muscles, nervous system manageable.
Finally, protection is through the formation of individual bones bone canal - spinal that protects the spinal cord, bone box - the skull that protects the brain, bone cells - chest, protects vital organs of the thoracic cavity (heart, lungs), bone containers - pelvis that protects important for the continuation of the type of reproductive organs.
The biological function of the skeletal system connected with the participation of the skeleton in metabolism, especially in mineral metabolism (Skeleton is the depot minerals - phosphorus, calcium, iron, etc..) This is important to consider for understanding disease metabolism (rickets, etc.) and for diagnosis via radiant energy (X-rays, radioactive isotopes). In addition, the skeleton performs hematopoietic function. This bone is not just a protective case for bone marrow, and the latter is an organic part of it. Some development and activity of the bone marrow affecting the bone structure of matter, and, conversely, mechanical factors affect the function of blood: increased movement promotes blood, so when designing exercise to consider the unity of all functions of the skeleton.
The development of the skeleton
At the lower levels of the organization, as well as the embryonic period in all vertebrates first beginnings internal skeleton is dorsal string - chorda dorsalis, which originates from the mesoderm. Chord is the hallmark of a lower representative type of chord - lancelet (Amphioxus lanceolatus), whose skeleton consists of elongated along the body with its dorsal side dorsal string and its surrounding connective tissue.In lower vertebrate species [kruhlorotыe, selahyy (SHARKS) and hryaschevыe hanoydы] connective tissue skeleton around the chord and the rest replaced cartilage skeleton, which in turn is more highly vertebrates from teleost fish and mammals ending becomes bone. As the last chord fades, except for minor residues (jelly core of the intervertebral disc). Water forms can treat cartilage skeleton as mechanical load in the aquatic environment far less than in the air. But skeleton allowed the animals to get out of the water onto land, raise your body above the ground and firmly on his feet.
Thus, in the course of phylogenesis as something to adapt to the environment is a succession of three species of the skeleton. This change is repeated in the course of human ontogenesis, during which there are 3 stages of development of the skeleton: 1) connective tissue (webbed), 2) cartilage and 3) bone. These 3 stages of development are almost all the bones, except the bones of the cranial vault, most of the bones of the face, of the clavicle, which arise directly on the basis of connective tissue, bypassing the stage of cartilage.These, as they are called, cover the bone can be considered as derivatives of the once former external skeleton, drifted into the mesoderm and joined in the further evolution of the internal skeleton as its complement.