Bone. Bone tissue - basics of histology Bone plate histology
Topic 14. CONNECTING TISSUE. SKELETAL CONNECTING TISSUES
Skeletal connective tissues include cartilage and bone tissues that perform supporting, protective and mechanical functions, as well as participate in the metabolism of minerals in the body. Each of these types of connective tissue has significant morphological and functional differences, and therefore they are considered separately.
Cartilage tissue
Cartilage tissue consists of cells - chondrocytes and chondroblasts, as well as dense intercellular substance.
Chondroblastsare located singly along the periphery of the cartilaginous tissue. They are elongated flattened cells with a basophilic cytoplasm containing a well-developed granular EPS and a lamellar complex. These cells synthesize the components of the intercellular substance, release them into the intercellular environment, gradually differentiate into definitive cells of the cartilage tissue - chondrocytes.Chondroblasts are capable of mitotic division. The perichondrium surrounding the cartilaginous tissue contains inactive, poorly differentiated forms of chondroblasts, which, under certain conditions, differentiate into chondroblasts, synthesizing the intercellular substance, and then into chondrocytes.
Amorphous substancecontains a significant amount of minerals that do not form crystals, water, dense fibrous tissue... Vessels in the cartilaginous tissue are normally absent. Depending on the structure of the intercellular substance, cartilage tissues are subdivided into hyaline, elastic and fibrous cartilaginous tissue.
In the human body, hyaline cartilage tissue is widespread and is part of the large cartilage of the larynx (thyroid and cricoid), trachea, and the cartilaginous part of the ribs.
Elastic cartilage tissue is characterized by the presence of both collagen and elastic fibers in the cellular substance (cartilage tissue auricle and the cartilaginous part of the external auditory canal, the cartilage of the external nose, small cartilage of the larynx and middle bronchi).
Fibrous cartilage is characterized by the content of powerful bundles of parallel collagen fibers in the intercellular substance. In this case, chondrocytes are located between the fiber bundles in the form of chains. By physical properties characterized by high strength. In the body, it is found only in limited places: it forms part of the intervertebral discs (annulus fibrosus), and is also localized at the points of attachment of ligaments and tendons to hyaline cartilage. In these cases, a gradual transition of connective tissue fibrocytes to cartilage chondrocytes is clearly traced.
When studying cartilage tissue, one should clearly understand the concepts of "cartilage tissue" and "cartilage".
Cartilage is a type of connective tissue, the structure of which is superimposed above. Cartilage is an anatomical organ that consists of cartilage and perichondrium. The perichondrium covers the cartilaginous tissue from the outside (with the exception of the cartilage tissue of the articular surfaces) and consists of fibrous connective tissue.
In the perichondrium, two layers are distinguished:
1) external - fibrous;
2) internal - cellular (or cambial, germ).
In the inner layer, poorly differentiated cells are localized - prechondroblasts and inactive chondroblasts, which, in the process of embryonic and regenerative histogenesis, turn first into chondroblasts, and then into chondrocytes.
The fibrous layer contains a network of blood vessels. Therefore, the perichondrium, as an integral part of the cartilage, performs the following functions:
1) provides avascular cartilage tissue with trophism;
2) protects cartilage tissue;
3) ensures the regeneration of cartilage tissue in case of damage.
The trophism of the hyaline cartilage tissue of the articular surfaces is provided by the synovial fluid of the joints, as well as fluid from the vessels of the bone tissue.
The development of cartilage tissue and cartilage (chondrogistogenesis) is carried out from the mesenchyme.
Bone tissue
Bone is a type of connective tissue and consists of cells and intercellular substance, which contains a large amount of mineral salts, mainly calcium phosphate. Mineral substances make up 70% of bone tissue, organic - 30%.
Bone tissue functions:
1) support;
2) mechanical;
3) protective (mechanical protection);
4) participation in the mineral metabolism of the body (depot of calcium and phosphorus).
Bone cells - osteoblasts, osteocytes, osteoclasts. The main cells in the formed bone tissue are osteocytes... These are process cells with a large nucleus and a weakly expressed cytoplasm (nuclear-type cells). Cell bodies are localized in bone cavities (lacunae), and processes in bone tubules. Numerous bone tubules, anastomosed with each other, penetrate the bone tissue, communicating with the perivascular space, and form the drainage system of the bone tissue. This drainage system contains tissue fluid, through which the exchange of substances is provided not only between cells and tissue fluid, but also in the intercellular substance.
Osteocytes are definitive forms of cells and do not divide. They are formed from osteoblasts.
Osteoblastscontained only in developing bone tissue. In the formed bone tissue, they are usually contained in an inactive form in the periosteum. In developing bone tissue, osteoblasts cover each bone plate along the periphery, tightly adhering to each other.
The shape of these cells can be cubic, prismatic and angular. The cytoplasm of osteoblasts contains a well-developed endoplasmic reticulum, the lamellar Golgi complex, and many mitochondria, which indicates a high synthetic activity of these cells. Osteoblasts synthesize collagen and glycosaminoglycans, which are then secreted into the intercellular space. Due to these components, an organic matrix of bone tissue is formed.
These cells provide the mineralization of the intercellular substance through the release of calcium salts. Gradually releasing the intercellular substance, they seem to be walled up and turn into osteocytes. At the same time, intracellular organelles are largely reduced, synthetic and secretory activity decreases, and the functional activity inherent in osteocytes remains. Osteoblasts, localized in the cambial layer of the periosteum, are in an inactive state, and synthetic and transport organelles are poorly developed in them. When these cells are irritated (in the case of injuries, bone fractures, etc.), a granular EPS and a lamellar complex develop rapidly in the cytoplasm, an active synthesis and release of collagen and glycosaminoglycans occurs, the formation of an organic matrix ( callus), and then the formation of definitive bone tissue. In this way, due to the activity of osteoblasts in the periosteum, bone regeneration occurs when they are damaged.
Osteoclasts- bone-destroying cells, in the formed bone tissue are absent, but are contained in the periosteum and in places of destruction and restructuring of bone tissue. Since local processes of bone tissue restructuring are continuously carried out in ontogenesis, osteoclasts are also present in these places. In the process of embryonic osteohistogenesis, these cells play a very important role and are present in large numbers. Osteoclasts have a characteristic morphology: these cells are multinucleated (3 - 5 or more nuclei), have a rather large size (about 90 μm) and characteristic shape - oval, but the part of the cell adjacent to the bone tissue is flat. In the flat part, two zones can be distinguished: the central (corrugated part containing numerous folds and processes, and the peripheral part (transparent) in close contact with the bone tissue. In the cytoplasm of the cell, under the nuclei, there are numerous lysosomes and vacuoles of various sizes.
The functional activity of the osteoclast is manifested as follows: in the central (corrugated) zone of the cell base, carbonic acid and proteolytic enzymes are released from the cytoplasm. Released carbonic acid causes demineralization of bone tissue, and proteolytic enzymes destroy the organic matrix of the intercellular substance. Fragments of collagen fibers are phagocytosed by osteoclasts and are destroyed intracellularly. Resorption (destruction) of bone tissue occurs through these mechanisms, and therefore osteoclasts are usually localized in the depressions of the bone tissue. After the destruction of bone tissue due to the activity of osteoblasts, which are evicted from the connective tissue of the vessels, new bone tissue is built.
Intercellular substancebone tissue consists of a basic (amorphous) substance and fibers, which contain calcium salts. Fibers consist of collagen and are folded into bundles that can be arranged in parallel (ordered) or irregularly, on the basis of which a histological classification of bone tissues is built. The main substance of bone tissue, like other types of connective tissue, consists of glycosamine and proteoglycans.
The bone tissue contains less chondroitinsulfuric acids, but more citric and others, which form complexes with calcium salts. In the process of development of bone tissue, an organic matrix is \u200b\u200bfirst formed - the main substance and collagen fibers, and then calcium salts are deposited in them. They form crystals - hydroxyapatites, which are deposited both in the amorphous substance and in the fibers. Providing strength to bones, calcium phosphate salts are also a depot of calcium and phosphorus in the body. Thus, bone tissue takes part in the mineral metabolism of the body.
When studying bone tissue, the concepts of "bone tissue" and "bone" should also be clearly distinguished.
BoneIs an organ, the main structural component of which is bone tissue.
Bone as an organ is composed of elements such as:
1) bone tissue;
2) the periosteum;
3) bone marrow (red, yellow);
4) vessels and nerves.
Periosteum(periosteum) surrounds bone tissue along the periphery (except for the articular surfaces) and has a structure similar to the perichondrium.
In the periosteum, the outer fibrous and inner cell (or cambial) layers are isolated. The inner layer contains osteoblasts and osteoclasts. The vascular network is localized in the periosteum, from which small vessels penetrate into the bone tissue through the perforating channels.
Red bone marrowis considered as an independent organ and belongs to the organs of hematopoiesis and immunogenesis.
Bone tissue in the formed bones is presented mainly in a lamellar form, however, in different bones, in different parts of the same bone, it has a different structure. In flat bones and epiphyses of tubular bones, bone plates form crossbeams (trabeculae) that make up the cancellous bone. In the diaphysis of the tubular bones, the plates are tightly adjacent to each other and form a compact substance.
All types of bone tissue develop mainly from the mesenchyme.
There are two ways of osteohistogenesis:
1) development directly from the mesenchyme (direct osteohistogenesis);
2) development from the mesenchyme through the cartilage stage (indirect osteohistogenesis).
The structure of the diaphysis of the tubular bone... On the transverse section of the diaphysis of the tubular bone, the following layers are distinguished:
1) the periosteum (periosteum);
2) the outer layer of general (or general) plates;
3) a layer of osteons;
4) the inner layer of common (or general) plates;
5) an internal fibrous plate (endosteum).
External common plates are located under the periosteum in several layers, without forming a single ring. Osteocytes are located between the plates in the lacunae. Through the outer plates, piercing channels pass through which piercing fibers and vessels penetrate from the periosteum into the bone tissue. The perforating vessels provide trophism of the bone tissue, and the perforating fibers firmly bind the periosteum to the bone tissue.
The osteon layer consists of two components: the osteons and the insertion plates between them. Osteon is a structural unit of the compact substance of the tubular bone. Each osteon consists of 5 - 20 concentrically layered plates and an osteon channel, in which vessels (arterioles, capillaries, venules) pass. There are anastomoses between the canals of adjacent osteons. Osteons make up the bulk of the bone tissue of the diaphysis of the tubular bone. They are located longitudinally along the tubular bone in accordance with the lines of force (or gravitational) and provide a support function. When the direction of the lines of force changes, as a result of a fracture or curvature of the bones, osteons that do not bear a load are destroyed by osteoclasts. However, osteons are not completely destroyed, and part of the osteon's bone plates along its length is preserved, and such remaining parts of the osteon are called insertion plates.
During postnatal osteogenesis, bone tissue is constantly being restructured, some osteons are resorbed, others are formed, therefore there are intercalated plates or remnants of previous osteons between the osteons.
The inner layer of the common plates has a structure similar to the outer one, but it is less pronounced, and in the area of \u200b\u200bthe transition of the diaphysis to the epiphyses, the common plates continue into the trabeculae.
Endoost - a thin connective tissue plate lining the cavity of the diaphysis canal. The layers in the endosteum are not clearly expressed, but among the cellular elements there are osteoblasts and osteoclasts.
Bone classification
There are two types of bone tissue:
1) reticulofibrous (coarse fibrous);
2) lamellar (parallel to fibrous).
The classification is based on the nature of the arrangement of collagen fibers. In reticulofibrous bone tissue, bundles of collagen fibers are thick, sinuous, and disordered. Osteocytes are randomly located in the mineralized intercellular substance in the lacunae. Lamellar bone tissue consists of bone plates, in which collagen fibers or their bundles are located parallel in each plate, but at right angles to the course of the fibers of adjacent plates. Osteocytes are located between the plates in the lacunae, while their processes pass through the plates in the tubules.
In the human body, bone tissue is almost exclusively a lamellar form. Reticulofibrous bone tissue occurs only as a stage in the development of some bones (parietal, frontal). In adults, it is located in the area of \u200b\u200battachment of the tendons to the bones, as well as at the site of the ossified sutures of the skull (sagittal suture, scales of the frontal bone).
Bone and bone development (osteohistogenesis)
All types of bone tissue develop from one source - from the mesenchyme, but the development of different bones is not the same. There are two ways of osteohistogenesis:
1) development directly from the mesenchyme - direct osteohistogenesis;
2) development from the mesenchyme through the stage of cartilage - indirect osteohistogenesis.
With the help of direct osteohistogenesis, a small number of bones develop - the integumentary bones of the skull. In this case, reticulofibrous bone tissue is first formed, which is soon destroyed and replaced by lamellar tissue.
Direct osteohistogenesis occurs in four stages:
1) the stage of formation of skeletal islands in the mesenchyme;
2) the stage of formation of the osseoid tissue - organic matrix;
3) the stage of mineralization (calcification) of osteoid tissue and the formation of reticulofibrous bone tissue;
4) the stage of transformation of reticulofibrous bone tissue into lamellar bone tissue.
Indirect osteogenesis begins from the 2nd month of intrauterine development. First, in the mesenchyme, due to the activity of chondroblasts, a cartilaginous model of the future bone from hyaline cartilage tissue, covered by the perichondrium, is laid. Then there is a replacement first in the diaphysis, and then in the epiphyses of the cartilaginous tissue of the bone. Ossification in the diaphysis is carried out in two ways:
1) perichondral;
2) endochondral.
Initially, in the area of \u200b\u200bthe diaphysis of the cartilaginous anlage of the bone, osteoblasts are evicted from the perichondrium and form reticulofibrous bone tissue, which in the form of a cuff encompasses the cartilaginous tissue along the periphery. As a result, the perichondrium turns into a periosteum. This method of bone formation is called perichondral. After the formation of the bone cuff, the trophism of the deep sections of the hyaline cartilage in the diaphysis region is disturbed, as a result of which the deposition of calcium salts occurs here - the cartilage mistlenae. Then, under the inductive influence of calcified cartilage, blood vessels grow into this zone from the periosteum through the holes in the bone cuff, in the adventitia of which there are osteoclasts and osteoblasts. Osteoclasts destroy the mistletoe cartilage, and around the vessels, due to the activity of osteoblasts, lamellar bone tissue is formed in the form of primary osteons, which are characterized by a wide lumen (channel) in the center and fuzzy boundaries between the plates. This method of bone formation deep in cartilage is called endochondral. Simultaneously with endochondral ossification, the coarse-fibrous bone cuff is rearranged into lamellar bone tissue, which makes up the outer layer of the general plates. As a result of perichondral and endochondral ossification, the cartilaginous tissue in the diaphysis is replaced by bone. In this case, the cavity of the diaphysis is formed, which is filled first with red bone marrow, followed by white bone marrow.
Epiphyses of tubular bones and cancellous bones develop only endochondrically. Initially, mistletoe is noted in the deep parts of the cartilage tissue of the pineal gland. Then vessels with osteoclasts and osteoblasts penetrate there, and due to their activity, the cartilage tissue is replaced by lamellar tissue in the form of trabeculae. The peripheral part of the cartilage tissue is retained as articular cartilage. Between the diaphysis and the pineal gland long time the cartilage tissue is preserved - the metaepiphyseal plate, due to the constant multiplication of cells of which the bone grows in length.
In the metaepiphyseal plate, the following cell zones are distinguished:
1) border zone;
2) the area of \u200b\u200bcolumnar cells;
3) a zone of vesicular cells.
By about 20 years, the metaepiphyseal plate is reduced, synostosis of the epiphyses and diaphysis occurs, after which the bone growth in length stops. In the process of bone development due to the activity of osteoblasts in the periosteum, bones grow in thickness. Regeneration of bones after damage and fractures is carried out due to the activity of the osteoblasts of the periosteum. The restructuring of bone tissue is carried out constantly throughout the entire osteogenesis: some osteons or their parts are destroyed, others are formed.
Factors affecting the process of osteohistogenesis and the state of bone tissue
The following factors influence the process of osteohistogenesis on the state of bone tissue.
1. Content of vitamins A, C, D. Lack of these vitamins in food leads to disruption of the synthesis of collagen fibers and to the breakdown of existing ones, which is manifested by fragility and increased fragility of bones. Insufficient formation of vitamin D in the skin leads to impaired calcification of bone tissue and is accompanied by insufficient bone strength and flexibility (for example, in rickets). Excess vitamin A content activates the activity of osteoclasts, which is accompanied by bone resorption.
2. Optimal content of thyroid hormones and parathyroid gland - calcitonin and parathyroid hormone, which regulate serum calcium. The level of sex hormones also affects the condition of the bone tissue.
3. Curvature of bones leads to the development of a piezoelectric effect - stimulation of osteoclasts and bone resorption.
4. Social factors - nutrition, etc.
5. Environmental factors.
Age-related changes in bone tissue
With increasing age, the ratio of organic and inorganic substances in the bone tissue changes towards an increase in inorganic and a decrease in organic, which is accompanied by an increase in bone fragility. This can explain the significant increase in the frequency of fractures in the elderly.
Lesson number 10
Traffic. The structure of the musculoskeletal system. Prevention of her diseases
II. Skeleton
III. Muscular apparatus
Muscle structure
2) Muscle groups
I. Functional structure of the musculoskeletal system
1) Body support
2) Moving a body or its parts in space
3) Protective (protection internal organs, brain and spinal cord, etc.)
Basic principles of the system functioning
1) Basic principles of the skeleton: works in accordance with the laws of mechanics
2) The basic principles of the functioning of the muscular apparatus:
A) arbitrary (conscious) nature of the contraction
B) most muscles are grouped into functional complexes - agonists (move the body or part of it in one direction) and antagonists (move the body or part of it in opposite directions); the coordinated work of these muscle complexes is achieved due to the coordination of the processes of excitation and inhibition in the neurons of the corresponding somatic arches)
C) with excessive stress on the muscles, a state of fatigue develops in them; the resulting muscle pain and the feeling of fatigue is associated with a relative lack of oxygen in muscle tissue (delivery lags behind consumption), activation of glycolysis, the formation of excessive amounts of lactic acid and its release into the general bloodstream
3) Regulatory mechanisms
AND) nervous regulation the musculoskeletal system is carried out by the somatic department nervous system
B) the basic principle of regulation is reflex (somatic reflex arcs are closed at the level of the spinal cord and brain stem)
C) plays an important role in the activity of the somatic nervous system midbrain
C) the highest link in the system of regulation of movements is the cortex of the cerebral hemispheres of the endbrain (musculocutaneous zones located on both sides of the central sulcus)
D) along with the above-mentioned nervous structures, the cerebellum, basal nuclei of the telencephalon, and the limbic system play an important role in the regulation of motor activity.
II. Skeleton
It contains over 200 bones. Bone structure.
1) Classification of bones:
Flat bones (eg: frontal and parietal bones of the skull, scapula, sternum)
Tubular bones (ex: femur, humerus)
Anatomical structure of bones
Flat bones: consist of two thin plates, between which there is a spongy substance
Tubular bones: in the tubular bone, two pineal glands are distinguished, formed by a cancellous substance, and a diaphysis, built of a compact substance. The epiphyses are outside covered with hyaline cartilage (part of the articular apparatus)
The diaphysis is covered from the outside by the periosteum, from the inside, from the side of the medullary cavity - by the endosteum; the periosteum performs protective and trophic functions, and also provides growth (in thickness) and bone regeneration.
Histological structure bones
The bones of an adult consist of lamellar bone tissue; coarse-fibrous bone tissue is found only in the cranial sutures and the places where tendons attach to the bones. General plan of the microscopic structure of bone tissue: the elementary structural block of lamellar bone tissue is a bone plate, consisting of a set of parallel oriented collagen fibers, impregnated with calcium phosphate, and cells (mainly osteocytes). Higher-order structures are formed from bone plates - osteons, general plates and bone packets. Osteon is a system of concentric cylinders, the wall of which is formed by a bone plate, in the center of which there is a canal containing vessels and nerve fibers... It is important to note that the directions of the fibers in adjacent cylinders do not coincide, which ensures high mechanical strength of the structure as a whole. Osteons form the basis of the compact substance of tubular bones. General plates are a set (usually up to ten) of extended bony plates located along the outer and inner perimeters of the diaphysis of tubular bones. The bone package is a complex of several bone plates. Many bone packets form the cancellous substance of flat bones and epiphyses of tubular bones, it should be emphasized that the internal architecture of bones is such that all their structural elements are organized in space in accordance with the direction of the lines of force, which results in significant strength with a relatively small bone thickness.
Bone joints
A) Continuous: characterized by the presence of a spacer between the bones, consisting of connective tissue (ex: spinal ligaments), cartilage (ex: intervertebral discs), bone tissue (ex: joints of the frontal and parietal skull bones),
B) Discontinuous: characterized by the following structure: between the bones there is a cavity containing fluid, which reduces the friction of the articular surfaces (the latter, as mentioned above, are covered with hyaline cartilage). The articular apparatus includes auxiliary structures, in particular, the articular capsule made of connective tissue. Varieties of discontinuous joints: cylindrical (ex: joint between I and II cervical vertebrae), block (ex: interphalangeal joint), ellipsoidal (ex: wrist joint), saddle (ex: carpal-metacarpal joint thumb), flat (ex: the joint between the flat processes of the vertebrae), spherical (ex: hip joint)
Skeleton departments
A) The skeleton of the head (skull) includes: the brain region consists of six bones - one frontal, two parietal, two temporal, one occipital), the facial region is formed by five main bones - one upper jawone lower jaw, two cheekbones, one palatine bone.
B) The skeleton of the trunk is presented:
A spine, built of individual vertebrae, connected by intervertebral discs (they consist of fibrous cartilage, provide flexibility of the spine, perform a shock-absorbing function). A separate vertebra is a bony ring. The spine consists of five sections: cervical (7 vertebrae), thoracic (12 vertebrae), lumbar (5 vertebrae), sacral (5 fused vertebrae), coccygeal (4-5 fused vertebrae). The spine is S-shaped and has four bends: two backward (kyphosis) and two forward (lordosis).
· chestwhich includes thoracic region spine, sternum, 12 pairs of ribs (10 of them connect to the sternum, 2 - oscillating)
B) the skeleton of the limbs, represented by the upper limbs, consisting of a belt upper limbs: 2 shoulder blades, 2 collarbones. Free limb skeleton: shoulder ( brachial bone), forearm (ulna and radius), hand (bones of the wrist, metacarpus, fingers). Lower limbs are represented by a belt lower limbsconsisting of the pelvis (a bony ring consisting of two pelvic bones and a sacrum). Skeleton of the free limb: thigh (femur), lower leg (large and small tibia), foot (bones of the tarsus, metatarsus, fingers).
III. Muscular apparatus
Has over 400 muscles
Muscle structure
AND) anatomical structure... Muscle is an organ in which a contractile part (or a body consisting of a head, abdomen and tail) and a tendon (built of dense, formed connective tissue) are distinguished, with the help of which it attaches to bones and other structures; outside the muscle is covered with fascia. Types of muscles:
Depending on the number of heads (biceps, for example, the biceps brachii), triceps, for example, the triceps brachii, quadriceps, for example, the quadriceps femoris)
Shape (long, for example, biceps brachii, short, for example, short flexors of the fingers of the hand, wide, for example, the diaphragm)
The histological structure of the muscles:
The basis of skeletal muscles is striated skeletal muscle tissue, the structural unit of which is muscle fiber (symplast)
Muscle fiber is covered with a thin connective tissue sheath in which blood vessels and nerves pass
Groups of muscle fibers form bundles of various ranks, separated by layers of connective tissue
In the center of the muscle fiber there is its contractile apparatus - many parallel oriented myofibrils (organelles of special significance)
Nuclei and most organelles overall value located on the periphery of the muscle fiber
Myofibrils are characterized by transverse striation - regular alternation of light (I) and dark (A) discs
Dark discs are formed by myosin fibrils, light discs - by actin ones (the latter are attached to the plate passing in the middle of the I-disc - the Z-strip)
The smallest repetitive unit of myofibril capable of contraction is the sarcomere, which includes half of the I-disk, the A-disk and half of the I-disk (its formula is as follows: 1/2 I + A + 1/2
Contraction mechanism: thin actin fibrils are drawn in by thick myosin fibrils deep into the A-disk (slip theory); the process needs ATP and Ca ions
Mouse groups
A) muscles of the head
I group - facial muscles: frontal, circular muscles of the eyes and mouth
Group II - chewing muscles: temporal, chewing, internal and external pterygoid
B) neck muscles
Subcutaneous muscle (platysma), sternocleidomastoid muscles, hyoid muscles.
C) back muscles
Distinguish between superficial (trapezius muscle, latissimus dorsi muscle, rhomboid muscle, serratus and levator scapula muscles) and deep (spinal erector muscles, etc.)
D) abdominal muscles
The rectus, transverse and oblique muscles of the abdomen (all of these muscles have broad and flat tendons that join together to form the white line of the abdomen).
Muscle abdominal wall together they form the abdominal press, which plays an important role in the acts of defecation and urination, as well as in generic activity
E) chest muscles
Large and small pectoral muscles, external and internal intercostal muscles, diaphragm (with holes for the esophagus and accompanying vagus nerves, trachea, aorta, inferior vena cava, sympathetic nerve trunk and some other nerves and vessels)
E) muscles of the shoulder girdle
Deltoid muscles.
G) shoulder muscles
Biceps brachii, brachialis muscle, triceps brachii.
H) muscles of the forearm
Brachioradialis muscle, flexors of the hand and fingers, extensors of the hand and fingers.
I) hand muscles
Muscles of the I-th finger, V-th finger, middle group muscles, providing flexion, extension and abduction of the phalanges.
K) muscles of the pelvic girdle
Large, middle and small gluteal muscles
L) thigh muscles
Quadriceps femoris, sartorius muscle, biceps femoris, semitendinosus muscle, semimembranosus muscle.
M) calf muscles
Tibialis muscle, peroneal muscles, triceps muscle of the leg (consists of two muscles: gastrocnemius and soleus).
H) muscles of the foot.
The short extensors of the fingers, internal, middle and external muscles that provide flexion and lateral movement of the fingers.
Similar information.
Musculoskeletal system human bone skeleton and skeletal muscles form. Due to the ability to contract, the muscles set in motion the bones of the skeleton, as a result of which the human body or parts of it can move in space and perform this or that work. Muscle contraction occurs under the influence of nerve impulses coming from the central nervous system. Skeletal muscles are one of the main effector apparatuses of the nervous system, which has been convincingly shown by physiologists.
THEM. Sechenov wrote: "All the infinite variety of external manifestations of brain activity is finally reduced to only one phenomenon - muscle movement." In addition to the bone skeleton and musculature, the system of organs of movement and support includes joints, cartilage, tendons, ligaments, fascia.
Main function bones - providing a solid support for the human body. Along with this mechanical function, bones also take part in mineral metabolism, since they contain the main supply of calcium, phosphorus, and other minerals. The bones contain red bone marrow - the main organ of hematopoiesis. Bone is an organ built predominantly from bone tissue. Each bone also includes a number of tissues that are in certain proportions.
For example, consider the structure of a tubular bones, namely the human femur. It consists of lamellar bone tissue, periosteum (periosteum), endosteum, articular cartilage, synovial endothelium, vessels and nerves. The cavity of the diaphysis, as well as the spaces of the spongy substance of the epiphyses, are filled with bone marrow. The compact bone substance is represented by lamellar bone tissue. Outside the diaphysis of the bone, there is a periosteum (periosteum), followed by the outer surrounding (general) plates.
From the inside from the side bone marrow cavity the internal surrounding (general) plates are located, covered with an endostomy. The main part of the tubular bone, located between the outer and inner surrounding plates, is made up of osteons and the insertion plates filling the spaces between them (residual osteons).
Osteon is a three-dimensional cylindrical system of concentrically located bone plates and osteocytes surrounding the central osteon canal. In the bone plates, ossein fibrils are tightly and parallel to each other. Bone-lamellar cylinders are inserted into one another, as it were. In the adjacent concentric bone plates, the axial fibrils run at a different angle. This results in the exceptional strength of the osteons. The complex structure of osteons is formed during the histogenesis of bone tissue and its constant restructuring.
Part osteons collapses. Their remains are made up of insert plates. Along with this, new osteons arise. Their source is cambial cells located in the loose connective tissue around the vessels in the osteon canals. Big role in the process of restructuring and especially in the mechanisms of reception physical activity take away piezoelectric effects. When the bone plates are bent, + and - charges appear on their surface. It is believed that a positive charge induces the differentiation of osteoclasts, and a negative charge induces osteoblasts.
Thus, in bone tissue the processes of creation and destruction proceed harmoniously, due to which mechanical strength and physiological bone regeneration are achieved.
Growth tubular bones in length, it usually ends by 20 years of age. Until this time, the metaepiphyseal growth plate, located between the pineal gland and the diaphysis, functions. In the metaepiphyseal plate, a border zone is distinguished, located closer to the bone tissue of the pineal gland. This zone is also called the resting cartilage zone. Next, a zone of proliferating young cartilage, or a zone of columnar cells, is isolated. Here, new chondroblasts are formed to replace those cartilage cells that die off at the diaphyseal surface of the plate.
The next zone in the metaepiphyseal plate called the zone of maturing cartilage, or the zone of vesicular cells. It is characterized by the destruction of chondrocytes, followed by enchondral ossification. Allocate another area of \u200b\u200bcalcification of the cartilage. It directly borders on the bone tissue of the diaphysis. Capillaries and osteogenic cells penetrate into it. The latter turn into osteoblasts, forming bone crossbars on the diaphyseal side of the metaepiphyseal plate.
Thus, interstitial cartilage growth on the epiphyseal side of the metaepiphyseal plate, it pushes the epiphyseal away from the diaphysis, but the metaepiphyseal plate does not increase in thickness, since from the side of the diaphysis it is constantly resorbed and replaced by bone tissue. Due to this, the growth of tubular bones occurs in length.
Lamellar bone tissue ( textus osseus lamellaris) - the most common type of bone tissue in an adult organism... It consists of bone records (lamellae ossea). The thickness and length of the latter ranges from several tens to hundreds of micrometers. They are not monolithic, but contain fibrils oriented in different planes.
In the central part of the plates, fibrils have predominantly longitudinal direction, along the periphery - tangential and transverse directions are added. The plates can delaminate, and the fibrils of one plate can continue into adjacent ones, creating a single fibrous bone base. In addition, the bone plates are penetrated by individual fibrils and fibers oriented perpendicular to the bone plates, woven into the intermediate layers between them, due to which greater strength of the lamellar bone tissue is achieved. This tissue is used to build both compact and spongy substances in most of the flat and tubular bones of the skeleton.
The histological structure of the tubular bone as an organ
The tubular bone as an organ is mainly built of lamellar bone tissue, except for the tubercles. Outside, the bone is covered with the periosteum, with the exception of the articular surfaces of the epiphyses, covered with hyaline cartilage.
Periosteum, or periosteum ( periosteum). In the periosteum, two layers are distinguished: outer (fibrous) and interior (cellular). The outer layer is formed mainly by fibrous connective tissue. The inner layer contains osteogenic cambial cells, preosteoblasts and osteoblasts of varying degrees of differentiation. Fusiform cambial cells have a small volume of cytoplasm and a moderately developed synthetic apparatus. Preosteoblasts are vigorously proliferating oval-shaped cells capable of synthesizing mucopolysaccharides. Osteoblasts are characterized by a highly developed protein-synthesizing (collagen) apparatus. The vessels and nerves feeding the bone pass through the periosteum.
The periosteum connects the bone with the surrounding tissues and takes part in its trophism, development, growth and regeneration.
Diaphysis structure
The compact substance that forms the diaphysis of the bone consists of bony plates [the thickness of which ranges from 4 to 12-15 microns]. Bone plates are arranged in a certain order, forming complex formations - osteons, or Haversian systems. Three layers are distinguished in the diaphysis:
outer layer of common plates,
middle, osteonic layer, and
the inner layer of common plates.
External common (general) plates do not form full rings around the shaft of the bone, overlapped on the surface by the following layers of plates. The internal common plates are well developed only where the compact substance of the bone directly borders on the medullary cavity. In the same places where the compact substance becomes spongy, its internal common plates continue into the plates of the spongy crossbeams.
In the outer common plates, there are perforating (Volkman's) canals, through which vessels enter the bone from the periosteum. From the side of the periosteum, collagen fibers penetrate into the bone at different angles. These fibers are named perforating (sharpey) fibers... Most often, they branch only in the outer layer of the common plates, but they can penetrate into the middle osteon layer, but they never enter the osteon plates.
In the middle layer, the bone plates are located in the osteons. Collagen fibrils are located in the bone plates, soldered into the calcified matrix. Fibrils have different directions, but they are mainly oriented parallel to the long axis of the osteon.
Osteons (Haversian systems) are structural units of the compact substance of the tubular bone. They are cylinders, consisting of bone plates, as if inserted into each other. In the bone plates and between them are the bodies of bone cells and their processes, immured in the bone intercellular substance. Each osteon is delimited from neighboring osteons by the so-called cleavage line formed by the main substance that cements them. In the central canal of the osteon, there are blood vessels with accompanying connective tissue and osteogenic cells.
Most of the diaphysis is the compact substance of tubular bones. On the inner surface of the diaphysis, bordering on the medullary cavity, lamellar bone tissue forms the bone crossbeams of the cancellous bone. The cavity of the diaphysis of tubular bones is filled with bone marrow.
Endost (endosteum) - the shell that covers the bone from the side of the medullary cavity. In the endosteum of the formed bone surface, an osmiophilic line is distinguished on the outer edge of the mineralized bone substance; an osteoid layer, consisting of an amorphous substance, collagen fibrils and osteoblasts, blood capillaries and nerve endings, a layer of squamous cells, indistinctly separating the endosteum from the elements of the bone marrow. The thickness of the endosteum exceeds 1–2 µm, but is less than that of the periosteum.
Between the endosteum and the periosteum, there is a certain microcirculation of fluid and minerals due to the lacunar-canalic system of the bone tissue.
Bone vascularization. Blood vessels form a dense network in the inner layer of the periosteum. From here originate thin arterial branches, which, in addition to the blood supply to the osteons, penetrate into the bone marrow through the feeding holes and take part in the formation of the capillary network feeding it. Lymphatic vessels are located mainly in the outer layer of the periosteum.
Bone tissue innervation. In the periosteum, myelinated and nonmyelinated nerve fibers form a plexus. Some of the fibers accompany the blood vessels and penetrate with them through the nutrient holes into the channels of the same name, and then into the osteon channels and then reach the bone marrow. Another part of the fibers ends in free nerve branches in the periosteum, and is also involved in the formation of encapsulated bodies.
Bone development, growth and regeneration. Osteoclast, its structure and function.
Bone growth is a very long process. It begins in humans from early embryonic stages and ends on average by 20 years of age. During the entire growth period, the bone increases both in length and width.
Long bone growth in length provided by the presence metaepiphyseal cartilage plate, in which two opposite histogenetic processes are manifested. One is the destruction of the epiphyseal plate with the formation of bone tissue, and the other is the continuous replenishment of cartilage tissue by the formation of cells. However, over time, the processes of destruction of cartilaginous tissue begin to prevail over the processes of neoplasm, as a result of which the cartilaginous plate becomes thinner and disappears.
In metaepiphyseal cartilage, three zones are distinguished:
border zone (intact cartilage),
the zone of columnar (actively dividing) cells and
zone of vesicular (dystrophically altered) cells.
The border zone, located near the pineal gland, consists of rounded and oval cells and single isogenic groups that provide a connection between the cartilaginous plate and the pineal gland bone. In the cavities between the bone and the cartilage, there are blood capillaries that provide nutrition to the cells of the deep-lying zones of the cartilaginous plate. The area of \u200b\u200bcolumnar cells contains actively multiplying cells that form columns located along the axis of the bone and ensure its growth and length. The proximal ends of the columns are composed of maturing, differentiating cartilage cells. The zone of vesicular cells is characterized by hydration and destruction of chondrocytes, followed by endochondral ossification. The distal part of this zone borders on the diaphysis, from where osteogenic cells and blood capillaries penetrate into it. The longitudinally oriented columns of the enchondral bone are essentially bony tubules, in place of which osteons form.
Subsequently, the centers of ossification in the diaphysis and pineal gland merge and the growth of the bone in length ends.
Long bone growth wide carried out due to the periosteum. From the side of the periosteum, very early, fine fibrous bone begins to form in concentric layers. This appositional growth continues until the end of bone formation. The number of osteons immediately after birth is small, but by the age of 25 in the long bones of the limbs, their number increases significantly.
It consists of epiphyses and diaphysis. From the outside, the diaphysis is covered by the periosteum, or periosteum (Figure 6-3). In the periosteum, two layers are distinguished: outer (fibrous) - formed mainly by fibrous connective tissue and internal (cellular) - contains cells osteoblasts. The vessels and nerves feeding the bone pass through the periosteum, and collagen fibers penetrate at different angles, which are called perforating fibers. Most often, these fibers branch out only in the outer layer of the common plates. The periosteum connects the bone with the surrounding tissues and takes part in its trophism, development, growth and regeneration.
The compact substance that forms the diaphysis of the bone consists of bone plates arranged in a certain order, forming three layers:
outer layer of common lamellae... In him the plates do not form full rings around the shaft of the bone. This layer contains perforating channels,along which vessels enter the bone from the periosteum.
middle, osteonic layer - formed by concentrically layered bone plates around the vessels . Such structures are called osteons, and the plates forming them - osteon plates... Osteons are the structural unit of the compact substance of the tubular bone. Each osteon is delimited from neighboring osteons by the so-called the cleavage line. In the central canal of the osteon, there are blood vessels with accompanying connective tissue . All osteons are generally parallel to the long axis of the bone. The osteon canals anastomose with each other. The vessels located in the canals of osteons communicate with each other, with the vessels of the bone marrow and periosteum. In addition to the osteon plates, this layer also contains insert plates(remnants of old destroyed osteons) , which lie between the osteons.
inner layer of common plates well developed only where the compact bone substance directly borders on the medullary cavity.
From the inside, the compact substance of the diaphysis is covered with an endosteum, which has the same structure as the periosteum.
Figure: 6-3. The structure of the tubular bone. A. Periosteum. B. Compacted bone substance. B. Endost. D. Bone marrow cavity. 1. Outer layer of common plates. 2. Osteonic layer. 3. Osteon. 4. Osteon canal. 5. Insert plates. 6. The inner layer of common plates. 7. Bone trabecula of spongy tissue. 8. Fibrous layer of the periosteum. 9. Blood vessels of the periosteum. 10. The piercing channel. 11. Osteocytes. (Scheme by V.G. Eliseev, Yu. I. Afanasyev).
Growth of tubular bones - the process is very slow. It begins in humans from the early embryonic stages and ends on average by 20 years of age. During the entire growth period, the bone increases both in length and width. The growth of the tubular bone in length is provided by the presence metaepiphyseal cartilaginous growth plate, in which two opposite histogenetic processes are manifested. One is the destruction of the epiphyseal plate and the other, opposite to it, is the constant replenishment of cartilage tissue by neoplasm. However, over time, the processes of destruction of the cartilaginous plate begin to prevail over the processes of neoplasm in it, as a result of which the cartilaginous plate becomes thinner and disappears.
Regeneration. Physiological regeneration of bone tissue is carried out by osteoblasts of the periosteum. However, this process is very slow.