According to their size and functions, bones are divided into tubular, short spongy And flat(Fig. 16).

Tubular bones— the bones of the limbs are long, have two heads and a body. Their longitudinal section shows a cavity in the central part, which in children is filled with red bone marrow, and in adults - with yellow bone marrow. The body of the tubular bone consists of dense (compact) tissue, and the head is made of spongy bone tissue formed by membranes located in mutually perpendicular directions. Between the membranes of the spongy substance there is red bone marrow, a blood-forming organ. Heads tubular bones have an articular surface covered cartilage, which consists of cells - chondrocytes(With gr. cartilage) and strong connective fibers. Thanks to cartilage cells, the bone grows in length.

Flat(scapula, sternum) and short spongy(wrist, vertebrae) bones, as a rule, consist only of spongy substance, covered with a thin layer of compact substance. Material from the site

The outside of the bone is covered periosteum- a thin connective tissue membrane that contains many vessels and nerves. Its inner layer consists of cells that grow, multiply and ensure the bone grows in thickness, as well as its healing in case of a fracture. Nutrition of the bone occurs thanks to the blood vessels of the periosteum. There are irregularities on the surface of the bone where the muscles attach. They are increased in people who have been involved in sports since childhood or adolescence.

On this page there is material on the following topics:

• Explain the relationship between the microscopic structure and functions of bones

• How physical labor and sports affect bone structure

• Bones (flat, tubular) anatomy

• Briefly about tubular bones

• Biology what is the microscopic and anatomical structure of bones

Questions about this material:

Bone tissue- a specialized type of connective tissue with high mineralization of the intercellular substance (73% bone tissue consists of calcium and phosphorus salts). The bones of the skeleton are built from these tissues. Bone tissue consists of cells and intercellular substance. Osteocytes are the predominant cells of bone tissue that have lost the ability to divide. They have a process form and are poor in organelles. They are located in bone cavities, or lacunae, which follow the contours of the osteocyte. Osteocyte processes are located in the bone tubules, through which nutrients and oxygen diffuse from the blood deep into the bone tissue.

Osteoblasts- young cells that create bone tissue. In bone, they are found in the deep layers of the periosteum, in places of formation and regeneration of bone tissue. Their cytoplasm has a well-developed granular endoplasmic reticulum, mitochondria and Golgi complex.

Osteoclasts (“bone crushers”) are symplasts capable of destroying calcified cartilage and bone. They are formed as a result of the fusion of several blood monocytes, are large in size (up to 90 microns), and contain from 3 to several dozen nuclei. The cytoplasm is slightly basophilic, rich in mitochondria and lysosomes.

Intercellular substance consists of:

Basic substance (osseomucoid), impregnated with calcium and phosphorus salts (calcium phosphate, hydroxyapatite crystals);

Collagen fibers forming small bundles. Moreover, hydroxyapatite crystals are ordered along the fibers.

Depending on the location of collagen fibers in intercellular substance bone tissues are classified into:

1. Reticulofibrous bone tissue. In it, collagen fibers have a random arrangement. This tissue is found mainly in embryos. In adults, it can be found in the area of ​​cranial sutures and in the places where tendons attach to bones.

2. Lamellar bone tissue. This is the most common type of bone tissue in the adult body. It consists of bone plates formed by osteocytes and mineralized amorphous substance with collagen fibers located parallel inside each plate. In adjacent laminae, the fibers usually have different directions, which results in greater strength of the lamellar bone tissue. The compact and spongy substances of most flat and tubular bones of the skeleton are built from this tissue.

The structure of tubular bone (bone as an organ).

Tubular bone consists of epiphyses and diaphysis. Outside, the diaphysis is covered with periosteum, or periosteum. There are two layers in the periosteum: outer (fibrous) - formed mainly by fibrous connective tissue and internal (cellular) - contains stem cells and young osteoblasts. From the periosteum, vessels and nerves supplying the bone pass through the perforating channels. The periosteum connects the bone with surrounding tissues and takes part in its nutrition, development, growth and regeneration. The compact substance that forms the bone diaphysis consists of bone plates that form three layers:

- outer layer of common lamellae. In it, the plates form 2-3 layers running around the diaphysis.

- middle, osteonic layer- formed by concentrically layered bone plates around the vessels. Such structures are called osteons (Haversian systems), and the plates that form them are called osteon plates. Osteons are a functional and structural unit of the compact substance of tubular bone. Each osteon is delimited from neighboring osteons by the so-called fusion line. The central canal of the osteon (Haversian canal) contains blood vessels with accompanying connective tissue. All osteons are generally located parallel to the long axis of the bone. The osteon canals anastomose with each other. The vessels located in the osteon canals communicate with each other, with the vessels of the periosteum and bone marrow. In the osteon layer between the osteons there are also intercalary plates (remnants of old destroyed osteons).

- inner layer of common laminae- 2-3 layers of plates bordering the medullary cavity.

The inside of the compact substance of the diaphysis is covered with endosteum, which has the same structure as the periosteum.

There are two types of tubular bones - short and long

Tubular bones

All tubular bones consist of both organic and inorganic substances. Throughout life, their quantitative ratio is not the same. In childhood, human bones are dominated by organic matter, which provide flexibility to the bones, and in the elderly - inorganic, which are responsible for strength. In adults, the ratio of inorganic substances (calcium salts) is 2/3, and organic (ossein, water) 1/3.

The bones contain:

· Periosteum – covers the entire bone from the outside. The periosteum is penetrated by many small vessels and nerves that penetrate deep into the bone through bone canals, providing blood supply and innervation to the deeper layers. The periosteum is a connective tissue plate, the outer layer of which consists of an accumulation of dense fibrous fibers, and the inner layer is represented by loose connective tissue containing osteoblasts (bone-forming cells);

· Compact substance - consists of bone plates that cover the periphery of the bone with a dense layer. Bone plates form the structural units of bone - osteons;

· Osteon – is a cylindrical formation that consists of cylindrical bone plates. Vessels and nerves pass inside the osteons;

· Spongy substance - located immediately behind the compact layer and differs from it in its porous structure. Bone crossbars (trabeculae), formed from the same bone plates, take part in the formation of spongy substance;

· Bone marrow is the main hematopoietic organ in the human body, which lies in the very thickness of the tubular bones. Bone marrow is divided into yellow and red:

1. Yellow bone marrow is formed by fat cells and is located in the bone marrow cavity;

2. Red bone marrow - located in the spongy substance and consists of reticular tissue, which is densely permeated blood vessels. Through these vessels, newly formed cells enter the bloodstream. Formed elements are formed due to stem cells located in the bone marrow. In addition to stem cells, osteoblasts and osteoclasts are also present here, thanks to which new bone structures are formed and old ones are destroyed.

There are two types of tubular bones - short and long