The structure and shape of bones

The combination of the required mechanical properties of bone - both flexibility and mechanical strength - provides its composition. Bone 2 / 3 consists of inorganic matter (calcium salt) and 1 / 3 - from organic matter (ossein protein). Calcium salts give bone hardness, and provides significant flexibility ossein.

The structure of the isolated bone periosteum (periosteum), compact substance, and cancellous bone marrow.

The periosteum (periosteum) covering the entire outer surface of the bone except joint. It permeates a lot of fine blood vessels and nerve fibers in bone tubules penetrating into the bone, due to what is provided by its blood supply and innervation. In structure the periosteum is a thin plate of connective tissue, its outer layer consists of dense fibrous fibers, and internal - of fibrous and loose connective tissue in which lie osteoblasts - osteoplastic cells. The inner layer of the periosteum is cambial, he is responsible for bone growth in width, cambial layer of osteoblasts also provide recovery after bone fractures.

Compact substance (substantia compacta), consisting of bony plates covered by a dense layer of the periphery of the bone. Part of the bony plates that make up the compact substance, forms a structural unit of the actual bone - osteon.

Osteon - a cylindrical formation consisting of several layers of bony plates of cylindrical form, as it were inserted into each other and surrounding the central canal, which are nerves and blood vessels. The intervals between osteons is occupied intercalary plate; inside and outside osteons and intercalary plates covered with surrounding plates. Osteons are arranged in accordance with the load acting on this bone.

Cancellous bone (substantia spongiosa), located under the compact, different porous structure. It is formed bone beams (trabeculae), which, in turn, are composed of bony plates, oriented in accordance with the direction of acting on the bone stress.

Bone marrow (medulla ossium) operates as the bones of the body. Distinguish yellow (medulla ossium flava) and red (medulla ossium rubra) bone marrow.

Yellow bone marrow is located in the medullary cavity and consists mainly of fat cells (they determine its color).

Red bone marrow is located in cancellous bone - Body bone formation and hematopoiesis. It consists of a reticulum and densely penetrated by blood vessels. For these vessels the blood cells, which mature in hematopoietic cells (stem cells), bone marrow, enter the general circulation of the body. In the hinges of the reticulum, in addition to stem cells, are also the cells that form and destroy the bone - osteoclasts and osteoblasts.

The shape of the diversity of bone is divided into four groups: isolated tubular sponge, flat, and mixed bone. Different roles of these bones in the skeleton determines the differences in their internal structure.

Bones are distinguished by more or less elongated cylindrical middle part - the diaphysis, or body of the bone. Diaphysis (diaphysis) consists of compact substance which surrounds the inner medullary cavity (cavitas medullaris), containing yellow marrow. Distinguish long and short tubular bones: the bones are long bones of the shoulder, forearm, thigh and leg, and a short - phalanges, and bones of the pastern and hock. Diaphysis of long bones on either side terminates the pineal gland (epiphysis), which is filled with a spongy material containing red marrow. Between the epiphysis and diaphysis is separated metaphyses (metaphisis).

Spongy bone, consisting of a spongy substance, and divided into long and short. By the long bones are cancellous bone of the chest - the ribs and sternum, and a short - vertebrae, carpal bones, tarsal, and sesamoid bones (located in the tendons of the muscles near the joints). Of spongy bones differ in the absence of the medullary cavity, spongy bone on the outside covered with a thin layer of compact substance.

By the flat bones include the bones of the scapula, pelvic bones, the bones of the skull cap. Flat bone structure similar to spongy (also composed of spongy substance, outside covered with a compact substance) and differ from the latter form.

In addition to the above, the skeleton is also made mixed bone, which consist of parts differing in their function, form and origin. Mixed bones found among the bones of the skull base.

List of Abbreviations

a., aa. — arteria, arteriae (artery, the artery)

lig., ligg. — ligamentum, ligamenta (ligament, the ligaments)

m., mm. — musculus, musculi (muscle, the muscle)

n., nn. — nervus, nervi (nerve, the nerve)

r., rr. — ramus, rami (branch)

s. — seu (or)

v., vv. — vena, venae (vienna)