The musculoskeletal system is often called the musculoskeletal system because the skeleton and muscles function together. They determine the shape of the body, provide support, protective and motor functions.
— the most active part of the musculoskeletal system, they are attached to the skeleton and control all human movements, because they can contract.
Bones act as passive levers.
Most of the bones of the skeleton are movably connected through joints. The muscle is attached at one end to one bone that forms the joint, and at the other end to another bone. When a muscle contracts, it moves the bones. Thanks to the muscles of opposite action, the bones can not only make certain movements, but also be fixed relative to each other.
Bones and muscles take part in metabolism, in particular in the exchange of phosphorus and calcium.
FUNCTIONS
Support the function is manifested in the fact that the bones of the skeleton and muscles form a strong frame that determines the position of the internal organs and does not allow them to move.
Protective the function is performed by the bones of the skeleton, which protect organs from injury. Thus, the spinal cord and brain are in a bone “case”: the brain is protected by the skull, the spinal cord by the spine.
The rib cage covers the heart and lungs, airways, esophagus, and major blood vessels. The abdominal organs are protected from behind by the spine, from below by the pelvic bones, and in front by the abdominal muscles.
Motor the function is possible only if the muscles and bones of the skeleton interact, since the muscles set the bone levers in motion.
CHEMICAL COMPOSITION OF BONES
The chemical composition of human bone consists of:
- Organic matter
- Minerals
Bone flexibility depends on the presence of organic substances, hardness - on inorganic substances.
The strongest bones in a person are in his adulthood (from 20 to 40 years).
In children, the proportion of organic substances in the bones is relatively large. Therefore, children's bones rarely break. In older people, the proportion of minerals in the bones increases. Therefore, their bones become more brittle.
TYPES OF BONES
Based on the type of structure there are:
- Tubular
- Spongy
- Flat Bones
Tubular bones: serve as long, strong levers, due to which a person can move in space or lift weights. The tubular bones include the bones of the shoulder, forearm, femur and tibia. The growth of tubular bones is completed by 20-25 years.
Spongy bones: mainly have a supporting function. Spongy bones include the bones of the vertebral bodies, sternum, small bones of the hand and foot.
Flat bones: perform mainly a protective function. Flat bones include the bones that form the cranial vault.
MUSCLES
Skeletal muscles are able to act only on signals coming from the central nervous system.
The energy required for contraction is released during the breakdown and oxidation of the organic substances of the muscle fiber itself. This creates energy-rich compounds that can repair muscle fibers during rest.
With work close to the limit, good nutrition and sufficient rest, the formation of new substances and structures in muscle fibers outpaces decay.
Due to this, a training effect occurs: the muscle becomes more powerful and more efficient. Low human mobility - physical inactivity - leads to weakening of the muscles and the entire body as a whole.
DISEASES OF THE MUSCULOSCAL APPARATUS
Physical inactivity is not the only reason that causes disorders in the skeleton. Poor nutrition, lack of vitamin D, diseases of the parathyroid glands - this is not a complete list of reasons that impair skeletal function, especially in children. So, with a lack of vitamin D in food, a child develops rickets.
At the same time, the intake of calcium and phosphorus into the body decreases, as a result of which the bones of the legs bend under the influence of the weight of the body. Due to improper ossification, thickenings are formed on the ribs and heads of the finger bones, and the normal growth of the skull is disrupted.
With rickets, not only the skeleton suffers, but also the muscles, endocrine and nervous systems. The child becomes irritable, whiny, and fearful. Vitamin D can be formed in the body under the influence of ultraviolet rays, so sunbathing and artificial irradiation with a quartz lamp prevent the development of rickets.
The cause of joint disease can be foci of purulent infection when the tonsils, middle ear, teeth, etc. are affected. Influenza, sore throat, severe hypothermia can precede disease of one or more joints. They swell, hurt, and movement in them becomes difficult. The normal growth of bone and cartilage tissue in the joints is disrupted; in especially severe cases, the joint loses mobility. That is why it is important to monitor the condition of your teeth, throat and nasopharynx.
Over-exercising can also damage your joints. With prolonged skiing, running, and jumping, the articular cartilage becomes thinner, and sometimes the knee meniscus suffers. In the knee joint between the femur and tibia there are cartilage pads - menisci.
Each knee joint has two menisci - left and right. There is fluid inside the cartilaginous meniscus (). It absorbs the sharp shocks that the body experiences during movements. Violation of the integrity of the menisci causes severe pain and severe lameness.
OUR MUSTOCULAR SYSTEM LOVES:
OUR MUSTOCULAR SYSTEM DOESN'T LIKE:
- Sedentary and sedentary lifestyle, which leads to muscle atrophy.
- Poor food, which causes a lack of micro- and macro-elements, in particular calcium and silicon.
- Excess weight.Excess weight puts excessive stress on the joints, causing them to wear out very quickly.
- Injuries.Injuries contribute to prolonged and forced limitation of movements. As a result, not only muscles and joints begin to suffer, but also the proper production of joint fluid, or, as it is also called, synovial fluid.
All organs of movement that ensure the movement of the body in space are combined into a single system. This includes bones, joints, muscles and ligaments. The human musculoskeletal system performs certain functions due to the peculiarities of the formation and structure of the organs of movement.
Importance of the musculoskeletal system
The human skeleton performs several vital functions:
- supporting;
- protective;
- provides movement;
- takes part in hematopoiesis.
Disorders of the musculoskeletal system cause pathological processes in the functioning of many body systems. Muscles attached to bones move them relative to each other, which ensures the movement of the body in space. The muscular apparatus has its own functional feature:
- surrounds the cavities of the human body, protecting them from mechanical damage;
- perform a supporting function, supporting the body in a certain position.
During the development of the human musculoskeletal system, the development of the central nervous system is stimulated. The development of muscles and nerve cells are mutually dependent processes. Knowing what functions of the musculoskeletal system are necessary for the normal functioning of the body, we can conclude that the skeleton is a vital structure of the body.
During the period of embryogenesis, when the body is practically not affected by any irritants, fetal movements cause irritation of muscle receptors. From them, impulses go to the central nervous system, stimulating the development of neurons. At the same time, the developing nervous system stimulates the growth and development of the muscular system.
Skeletal anatomy
Skeleton is a set of bones that perform supporting, motor and protective functions. The human musculoskeletal system has about 200 bones (depending on age), of which only 33-34 bones are unpaired. There are axial (chest, skull, spine) and accessory (free limbs) skeletons.
Bones are formed from a type of connective tissue. It consists of cells and a dense intercellular substance, which contains many mineral components and collagen, which provides elasticity.
The skeleton is a container for vital human organs: the brain is located in the skull, the spinal cord is located in the spinal canal, the chest provides protection to the esophagus, lungs, heart, main arterial and venous trunks, and the pelvis protects the organs of the genitourinary system from damage. Disorders of the musculoskeletal system can cause damage to internal organs, sometimes incompatible with life.
Bone structure
The bones contain a spongy and compact substance. Their ratio varies depending on the location and functions of a certain part of the musculoskeletal system.
The compact substance is localized in the diaphysis, which provides support and locomotor functions. Spongy substance is located in flat and short bones. The entire surface of the bone (with the exception of the articular surface) is covered with periosteum (periosteum).
Bone Formation
In ontogenesis, the formation of the musculoskeletal system goes through several stages - membranous, cartilaginous and bone. From the second week after conception, cartilaginous rudiments form in the mesenchyme of the membranous skeleton. By the 8th week, cartilage tissue is gradually replaced by bone tissue.
Replacement of cartilage tissue with bone tissue can take place in several ways:
- perichondrial ossification - the formation of bone tissue along the perimeter of the cartilage;
- periosteal ossification - production of young osteocytes by the formed periosteum;
- enchondral ossification - the formation of bone tissue within cartilage.
The process of bone tissue formation involves the growth of blood vessels and connective tissue from the periosteum into the cartilage (cartilage destruction occurs in these places). From some of the osteogenic cells, spongy bone subsequently develops.
During the period of intrauterine development of the fetus, ossification of the diaphyses of the tubular bones occurs (ossification points are called primary), then after birth, ossification of the epiphyses of the tubular bones occurs (secondary ossification points). Until the age of 16-24 years, a cartilaginous epiphyseal plate remains between the epiphyses and diaphyses.
Thanks to its presence, the organs of the musculoskeletal system are lengthened. After the bone is replaced and the diaphyses and epiphyses of the tubular bones fuse, human growth stops.
The structure of the spinal column
The spinal column is a series of overlapping vertebrae that are connected by the intervertebral discs, joints and ligaments that form the basis of the musculoskeletal system. The functions of the spine are not only support, but also protection, preventing mechanical damage to internal organs and the spinal cord passing in the spinal canal.
There are five sections of the spine - coccygeal, sacral, lumbar, thoracic and cervical. Each section has a certain degree of mobility; only the sacral spine is completely immobile.
The movement of the spine or its parts is ensured with the help of skeletal muscles. The correct development of the musculoskeletal system in the neonatal period provides the necessary support for internal organs and systems and their protection.
Structure of the chest
The rib cage is an osteochondral formation consisting of the sternum, ribs and 12 thoracic vertebrae. The shape of the chest resembles an irregular truncated cone. The chest has 4 walls:
- anterior - formed by the sternum and cartilage of the ribs;
- posterior - formed by the vertebrae of the thoracic spine and the posterior ends of the ribs;
- 2 lateral - formed directly by the ribs.
In addition, there are two openings of the chest - the upper and lower apertures. The organs of the respiratory and digestive system (esophagus, trachea, nerves and blood vessels) pass through the upper opening. The lower aperture is closed by a diaphragm, in which there are openings for the passage of large arterial and venous trunks (aorta, inferior vena cava) and the esophagus.
Structure of the skull
The skull is one of the main structures that forms the musculoskeletal system. The functions of the skull are to protect the brain, sensory organs and support the initial parts of the respiratory and digestive systems. It consists of paired and unpaired bones and is divided into the brain and facial sections.
The facial section of the skull consists of:
- from the maxillary and mandibular bones;
- two nasal bones;
The brain section of the skull includes:
- paired temporal bone;
- paired sphenoid bone;
- steam room;
- occipital bone.
The brain section performs a protective function for the brain and is its container. The facial region provides support for the initial portion of the respiratory and digestive systems and sensory organs.
Musculoskeletal system: functions and structure of the limbs
In the process of evolution, the skeleton of the limbs acquired extensive mobility due to the articulation of the bones (especially the radial and carpal joints). The thoracic and pelvic girdles are distinguished.
The upper girdle (pectoral) includes the scapula and two clavicle bones, and the lower (pelvic) is formed by the paired pelvic bone. The following sections are distinguished in the free part of the upper limb:
- proximal - represented by the humerus;
- middle - represented by the ulna and radius bones;
- distal - includes the carpal bones, metacarpal bones and finger bones.
The free part of the lower limb consists of the following sections:
- proximal - represented by the femur;
- middle - includes the tibia and fibula;
- distal - tarsal bones, metatarsal bones and finger bones.
The skeleton of the limbs provides the possibility of a wide range of actions and is necessary for normal work activity, which is provided by the musculoskeletal system. The functions of the skeleton of free limbs are difficult to overestimate, since with their help a person performs almost all actions.
The structure of the muscular system
Skeletal muscles are attached to bones and, when contracted, provide movement of the body or its individual parts in space. Skeletal muscles are based on striated muscle fibers. In addition to supporting and motor functions, muscles provide the function of breathing, swallowing, chewing, and take part in facial expressions, heat production and speech articulation.
The main properties of skeletal muscles are:
- excitability - the activity of muscle fibers is carried out under the influence of nerve impulses;
- conductivity - from the nerve endings to the central nervous system there is a rapid conduction of the impulse;
- contractility - as a result of the movement of a nerve impulse, contractility of the skeletal muscle occurs.
A muscle consists of tendinous ends (tendons that attach the muscle to the bone) and a belly (consisting of striated muscle fibers). The coordinated work of the musculoskeletal system is carried out by the correct functioning of the muscles and the necessary nervous regulation of muscle fibers.
The human musculoskeletal system is a set of structures (bones, joints, skeletal muscles, tendons) that provide the foundation (framework) of the body, provide support, and also provide the ability to make movements and move around. This article presents a very simplified description of the structure and some functions of the musculoskeletal system, so that it is understandable to as many visitors as possible, as well as possible diseases of these organs and systems.
SKELETON
The skeleton forms the human figure, supports and protects his body. It consists of 206 bones, supplemented by areas of cartilage. Cartilage is a dense, elastic tissue that is an important complement to bone, especially when a combination of strength and flexibility is required. The bones of the skeleton, mainly the long bones of the limbs, act as levers controlled by muscles, thereby allowing movement. Some bones protect the organs they surround, while others contain bone marrow, where red blood cells are produced. Bone is a living tissue in which old cells are constantly replaced by new ones. To keep your bones in good condition, you need to get enough protein, calcium and vitamins, especially vitamin D, from your diet.
The structure of the bone is characterized by strength, lightness and some flexibility. Bone tissue consists of protein strengthened with mineral salts, mainly calcium and magnesium. The outer (compact) layer of bone contains blood and lymphatic vessels, and the inner (spongy) layer has a cellular structure (for lightness). In the middle of the long bones there is a cylindrical cavity filled with bone marrow, a fat-like substance in which red and white blood cells are formed.
At the base of the skull there is an opening through which the spinal cord connects to the brain. The spinal cord runs inside the spine, which serves as its protection and consists of more than 30 individual vertebrae.
JOINTS
The individual bones of the skeleton are connected to each other by joints. There are several types of joints. Fixed joints, such as the sutures of the skull, hold bones tightly together, preventing them from moving. Partially moving joints (cartilaginous), such as those in the spine, allow some mobility. Finally, free-moving (synovial) joints, like those in the shoulder, allow significant mobility in multiple planes.
The nut joints (such as the shoulder or hip) are capable of providing the greatest range of motion. For example, the apex of the hip bone is almost spherical in shape and is located in the semicircular cavity of the pelvis. Joints of this type are designed like a ball joint, which gives them the ability to move in any direction.
Saddle joints allow movement in both directions and back and forth. This joint is located at the base of the thumb; without it it is very difficult to grasp large or small objects. Without these movements of the thumb, the hand would resemble a clumsy claw.
Locking joints are found in the fingers, toes, elbows and knees and allow movement in only one direction. The ends of the bones in such a joint are immersed in a lubricating fluid and held together by dense fibrous ligaments.
The carpal bones connected by these joints move in both directions and back and forth, similar to the saddle bones, but their range of motion is less. With age, movements in sliding joints become less smooth and more difficult.
Main signs of bone and joint disease
Among skeletal diseases of people of all ages, the most common are traumatic bone fractures and joint damage due to damage and wear. Bone inflammation and tumors are quite rare.
The main signs of skeletal injury are pain, swelling and inflammation (redness and heat) of the affected area.
Symptoms of joint damage include pain, swelling and stiffness. Osteoarthritis, caused by wear and tear on the joints, usually affects the joints in the neck, arms, hips and knees. Rheumatoid arthritis affects the connective tissue around the joints, causing them to become stiff and twisted, as well as severe pain.
MUSCLES
Movement of the body and internal organs is carried out with the help of muscles - soft tissue consisting of fibers that contract and relax, thereby causing movement. In the human body, there are three types of muscles: skeletal, which perform movements of the body itself, smooth, which produce movements within the body (for example, rhythmic contractions of the digestive tract that push food through it) and myocardium (heart).
The muscles become stronger through work and are usually in good condition with regular training. Vigorous exercise increases muscle size and improves blood circulation, and therefore increases the ability to perform even more strenuous activities. Conversely, inactivity can lead to muscle atrophy and weakness.
Smooth muscle and myocardium
Smooth muscles and myocardium are not under the control of consciousness, in other words, they contract or relax regardless of your desire and work automatically. Both types of involuntary muscles—smooth and cardiac—operate continuously to support cardiac contractions as well as functions such as breathing, digestion, and circulation.
Skeletal muscles are controlled and controlled by the central nervous system. Only skeletal muscles are under the control of consciousness and therefore voluntary in movement.
Skeletal muscles are attached to bones either directly or through tendons and can flex and straighten joints in response to specific stimuli.
How skeletal muscles work
Muscles are called the engines of the body. They make up almost half of the body's weight and convert chemical energy into force, which is transmitted through tendons to bones and joints. Most muscles usually work in groups, in which the contraction of one muscle is accompanied by the relaxation of another. When contracting, the muscle shortens in length by 40% and brings its attachment points to two different bones closer. Most skeletal muscles are attached to two or more nearby bones, often by fibrous tendons. When a muscle contracts, the bone to which it is attached moves. Thus, every movement is the result of a pull, not a push.
A muscle biopsy is a laboratory test of a small piece of muscle tissue to look for signs of disease. The photographs below show the thinnest sections of healthy muscle, magnified 8000 times. Each fiber consists of even thinner fibers separated by partitions. Each fiber contains two different proteins, which are arranged in parallel threads and form tiny dark (myosin molecules) and light stripes (actin molecules) - in the pictures on the left. In a relaxed muscle, these strips barely overlap each other (picture above), but in a contracted muscle they move over each other (picture below), shortening the muscle fibers.
Main signs of muscle diseases
Traumatic muscle injury is usually accompanied by pain, stiffness, and sometimes inflammation and swelling. Muscle weakness and pain can also occur with a viral infection.
In the process of evolution, animals mastered more and more new territories, types of food, and adapted to changing living conditions. Evolution gradually changed the appearance of animals. In order to survive, it was necessary to search for food more actively, hide better or defend against enemies, and move faster. Changing along with the body, the musculoskeletal system had to ensure all these evolutionary changes. The most primitive protozoa have no supporting structures, move slowly, flowing with the help of pseudopods and constantly changing shape.
The first support structure to appear is cell membrane. It not only separated the organism from the external environment, but also made it possible to increase the speed of movement due to flagella and cilia. Multicellular animals have a wide variety of support structures and devices for movement. Appearance exoskeleton increased the speed of movement due to the development of specialized muscle groups. Internal skeleton grows with the animal and allows it to reach record speeds. All chordates have an internal skeleton. Despite significant differences in the structure of musculoskeletal structures in different animals, their skeletons perform similar functions: support, protection of internal organs, movement of the body in space. The movements of vertebrates are carried out due to the muscles of the limbs, which carry out such types of movement as running, jumping, swimming, flying, climbing, etc.
Skeleton and muscles
The musculoskeletal system is represented by bones, muscles, tendons, ligaments and other connective tissue elements. The skeleton determines the shape of the body and, together with the muscles, protects the internal organs from all kinds of damage. Thanks to joints, bones can move relative to each other. The movement of bones occurs as a result of contraction of the muscles that are attached to them. In this case, the skeleton is a passive part of the motor apparatus that performs a mechanical function. The skeleton consists of dense tissues and protects internal organs and the brain, forming natural bone containers for them.
In addition to mechanical functions, the skeletal system performs a number of biological functions. Bones contain the main supply of minerals that are used by the body as needed. The bones contain red bone marrow, which produces blood cells.
The human skeleton includes a total of 206 bones - 85 paired and 36 unpaired.
Bone structure
Chemical composition of bones
All bones consist of organic and inorganic (mineral) substances and water, the mass of which reaches 20% of the mass of the bones. Organic matter of bones - ossein- has elastic properties and gives elasticity to bones. Minerals - salts of carbon dioxide and calcium phosphate - give bones hardness. High bone strength is ensured by a combination of the elasticity of ossein and the hardness of the mineral substance of bone tissue.
Macroscopic bone structure
On the outside, all bones are covered with a thin and dense film of connective tissue - periosteum. Only the heads of long bones do not have periosteum, but they are covered with cartilage. The periosteum contains many blood vessels and nerves. It provides nutrition to bone tissue and takes part in the growth of bone thickness. Thanks to the periosteum, broken bones heal.
Different bones have different structures. A long bone looks like a tube, the walls of which consist of a dense substance. This tubular structure long bones gives them strength and lightness. In the cavities of the tubular bones there is yellow bone marrow- loose connective tissue rich in fat.
The ends of the long bones contain cancellous bone substance. It also consists of bony plates that form many intersecting septa. In places where the bone is subject to the greatest mechanical load, the number of these partitions is highest. The spongy substance contains red bone marrow, the cells of which give rise to blood cells. Short and flat bones also have a spongy structure, only on the outside they are covered with a layer of damlike substance. The spongy structure gives bones strength and lightness.
Microscopic structure of bone
Bone tissue belongs to the connective tissue and has a lot of intercellular substance, consisting of ossein and mineral salts.
This substance forms bone plates arranged concentrically around microscopic tubules that run along the bone and contain blood vessels and nerves. Bone cells, and therefore bone, are living tissue; it receives nutrients from the blood, metabolism occurs in it, and structural changes can occur.
Types of bones
The structure of bones is determined by the process of long historical development, during which the body of our ancestors changed under the influence of the environment and adapted through natural selection to the conditions of existence.
Depending on the shape, there are tubular, spongy, flat and mixed bones.
Tubular bones are located in organs that make rapid and extensive movements. Among the tubular bones there are long bones (humerus, femur) and short bones (phalanxes of the fingers).
Tubular bones have a middle part - the body and two ends - the heads. Inside the long tubular bones there is a cavity filled with yellow bone marrow. The tubular structure determines the bone strength required by the body while requiring the least amount of material. During the period of bone growth, between the body and the head of the tubular bones there is cartilage, due to which the bone grows in length.
Flat Bones They limit cavities within which organs are placed (skull bones) or serve as surfaces for muscle attachment (scapula). Flat bones, like short tubular bones, are predominantly composed of spongy substance. The ends of long tubular bones, as well as short tubular and flat bones, do not have cavities.
Spongy bones built primarily of spongy substance covered with a thin layer of compact. Among them, there are long spongy bones (sternum, ribs) and short ones (vertebrae, carpus, tarsus).
TO mixed bones These include bones that are made up of several parts that have different structures and functions (temporal bone).
Protrusions, ridges, and roughness on the bone are places where muscles are attached to the bones. The better they are expressed, the more developed the muscles attached to the bones are.
Human skeleton.
The human skeleton and most mammals have the same type of structure, consisting of the same sections and bones. But man differs from all animals in his ability to work and intelligence. This left a significant imprint on the structure of the skeleton. In particular, the volume of the human cranial cavity is much larger than that of any animal that has a body of the same size. The size of the facial part of the human skull is smaller than the brain, but in animals, on the contrary, it is much larger. This is due to the fact that in animals the jaws are an organ of defense and acquisition of food and are therefore well developed, and the volume of the brain is less than in humans.
The curves of the spine, associated with the movement of the center of gravity due to the vertical position of the body, help a person maintain balance and soften shocks. Animals do not have such bends.
The human chest is compressed from front to back and close to the spine. In animals it is compressed from the sides and extended towards the bottom.
The wide and massive human pelvic girdle has the shape of a bowl, supports the abdominal organs and transfers body weight to the lower limbs. In animals, body weight is evenly distributed between the four limbs and the pelvic girdle is long and narrow.
The bones of the lower limbs of humans are noticeably thicker than the upper ones. In animals there is no significant difference in the structure of the bones of the fore and hind limbs. Greater mobility of the forelimbs, especially the fingers, allows a person to perform a variety of movements and types of work with his hands.
Skeleton of the torso axial skeleton
Skeleton of the torso includes a spine consisting of five sections, and the thoracic vertebrae, ribs and sternum form chest(see table).
Scull
The skull is divided into the brain and facial sections. IN brain The section of the skull - the cranium - contains the brain, it protects the brain from blows, etc. The skull consists of fixedly connected flat bones: the frontal, two parietals, two temporal, occipital and sphenoid. The occipital bone is connected to the first vertebra of the spine using an ellipsoidal joint, which allows the head to tilt forward and to the side. The head rotates along with the first cervical vertebra due to the connection between the first and second cervical vertebrae. There is a hole in the occipital bone through which the brain connects to the spinal cord. The floor of the skull is formed by the main bone with numerous openings for nerves and blood vessels.
Facial the skull section forms six paired bones - the upper jaw, zygomatic, nasal, palatine, inferior nasal concha, as well as three unpaired bones - the lower jaw, vomer and hyoid bone. The mandibular bone is the only bone of the skull that is movably connected to the temporal bones. All bones of the skull (with the exception of the lower jaw) are connected motionlessly, which is due to their protective function.
The structure of the human facial skull is determined by the process of “humanization” of the monkey, i.e. the leading role of labor, the partial transfer of grasping function from the jaws to the hands, which have become organs of labor, the development of articulate speech, the consumption of artificially prepared food, which facilitates the work of the masticatory apparatus. The cranium develops in parallel with the development of the brain and sensory organs. Due to the increase in brain volume, the volume of the cranium has increased: in humans it is about 1500 cm 2.
Skeleton of the torso
The skeleton of the body consists of the spine and rib cage. Spine- the basis of the skeleton. It consists of 33–34 vertebrae, between which there are cartilage pads - discs, which gives the spine flexibility.
The human spinal column forms four curves. In the cervical and lumbar spine they are convexly facing forward, in the thoracic and sacral spine - backward. In the individual development of a person, bends appear gradually; in a newborn, the spine is almost straight. First, the cervical curve forms (when the child begins to hold his head straight), then the thoracic curve (when the child begins to sit). The appearance of lumbar and sacral curves is associated with maintaining balance in an upright position of the body (when the child begins to stand and walk). These bends have important physiological significance - they increase the size of the thoracic and pelvic cavities; make it easier for the body to maintain balance; soften shocks when walking, jumping, running.
With the help of intervertebral cartilage and ligaments, the spine forms a flexible and elastic column with mobility. It is not the same in different parts of the spine. The cervical and lumbar spine have greater mobility; the thoracic spine is less mobile, as it is connected to the ribs. The sacrum is completely motionless.
There are five sections in the spine (see diagram “Divisions of the spine”). The size of the vertebral bodies increases from the cervical to the lumbar due to the greater load on the underlying vertebrae. Each vertebrae consists of a body, a bony arch and several processes to which muscles are attached. There is an opening between the vertebral body and the arch. The foramina of all vertebrae form spinal canal where the spinal cord is located.
Rib cage formed by the sternum, twelve pairs of ribs and thoracic vertebrae. It serves as a container for important internal organs: heart, lungs, trachea, esophagus, large vessels and nerves. Takes part in respiratory movements due to the rhythmic raising and lowering of the ribs.
In humans, in connection with the transition to upright walking, the hand is freed from the function of movement and becomes an organ of labor, as a result of which the chest experiences a pull from the attached muscles of the upper limbs; the insides do not press on the front wall, but on the lower one, formed by the diaphragm. This causes the chest to become flat and wide.
Skeleton of the upper limb
Skeleton of the upper limbs consists of the shoulder girdle (scapula and collarbone) and the free upper limb. The scapula is a flat, triangular bone adjacent to the back of the rib cage. The collarbone has a curved shape, reminiscent of the Latin letter S. Its significance in the human body is that it sets the shoulder joint some distance from the chest, providing greater freedom of movement of the limb.
The bones of the free upper limb include the humerus, the bones of the forearm (radius and ulna) and the bones of the hand (bones of the wrist, bones of the metacarpus and phalanges of the fingers).
The forearm is represented by two bones - the ulna and the radius. Due to this, it is capable of not only flexion and extension, but also pronation - turning inward and outward. The ulna at the top of the forearm has a notch that connects to the trochlea of the humerus. The radius bone connects to the head of the humerus. In the lower part, the radius has the most massive end. It is she who, with the help of the articular surface, together with the bones of the wrist, takes part in the formation of the wrist joint. On the contrary, the end of the ulna here is thin, it has a lateral articular surface, with the help of which it connects to the radius and can rotate around it.
The hand is the distal part of the upper limb, the skeleton of which is made up of the bones of the wrist, metacarpus and phalanges. The carpus consists of eight short spongy bones arranged in two rows, four in each row.
Skeleton hand
Hand- the upper or forelimb of humans and monkeys, for which the ability to oppose the thumb to all the others was previously considered a characteristic feature.
The anatomical structure of the hand is quite simple. The arm is attached to the body through the bones of the shoulder girdle, joints and muscles. Consists of 3 parts: shoulder, forearm and hand. The shoulder girdle is the most powerful. Bending your arms at the elbow gives your arms greater mobility, increasing their amplitude and functionality. The hand consists of many movable joints, it is thanks to them that a person can click on the keyboard of a computer or mobile phone, point a finger in the desired direction, carry a bag, draw, etc.
The shoulders and hands are connected through the humerus, ulna and radius. All three bones are connected to each other using joints. At the elbow joint, the arm can be bent and extended. Both bones of the forearm are connected movably, so during movement in the joints, the radius rotates around the ulna. The brush can be rotated 180 degrees.
Skeleton of the lower limbs
Skeleton of the lower limb consists of the pelvic girdle and the free lower limb. The pelvic girdle consists of two pelvic bones, articulated at the back with the sacrum. The pelvic bone is formed by the fusion of three bones: the ilium, the ischium and the pubis. The complex structure of this bone is due to a number of functions it performs. Connecting to the thigh and sacrum, transferring the weight of the body to the lower limbs, it performs the function of movement and support, as well as a protective function. Due to the vertical position of the human body, the pelvic skeleton is relatively wider and more massive than that of animals, since it supports the organs lying above it.
The bones of the free lower limb include the femur, tibia (tibia and fibula) and foot.
The skeleton of the foot is formed by the bones of the tarsus, metatarsus and phalanges of the fingers. The human foot differs from the animal foot in its arched shape. The arch softens the shocks the body receives when walking. The toes in the foot are poorly developed, with the exception of the big one, as it has lost its grasping function. The tarsus, on the contrary, is highly developed, the calcaneus is especially large in it. All these features of the foot are closely related to the vertical position of the human body.
Human upright walking has led to the fact that the difference in the structure of the upper and lower limbs has become significantly greater. Human legs are much longer than arms, and their bones are more massive.
Bone connections
There are three types of bone connections in the human skeleton: fixed, semi-movable and mobile. Fixed type of connection is a connection due to fusion of bones (pelvic bones) or the formation of sutures (skull bones). This fusion is an adaptation to bear the heavy load experienced by the human sacrum due to the vertical position of the torso.
Semi-movable the connection is made using cartilage. The vertebral bodies are connected to each other in this way, which contributes to the tilt of the spine in different directions; ribs with the sternum, which allows the chest to move during breathing.
Movable connection, or joint, is the most common and at the same time complex form of bone connection. The end of one of the bones that forms the joint is convex (the head of the joint), and the end of the other is concave (the glenoid cavity). The shape of the head and socket correspond to each other and the movements carried out in the joint.
Articular surface The articulating bones are covered with white shiny articular cartilage. The smooth surface of articular cartilage facilitates movement, and its elasticity softens the shock and shock experienced by the joint. Typically, the articular surface of one bone forming a joint is convex and is called the head, while the other is concave and is called the socket. Thanks to this, the connecting bones fit tightly to each other.
Bursa stretched between the articulating bones, forming a hermetically sealed joint cavity. The joint capsule consists of two layers. The outer layer passes into the periosteum, the inner layer releases fluid into the joint cavity, which acts as a lubricant, ensuring free sliding of the articular surfaces.
Features of the human skeleton associated with work and upright posture
Labor activity
The body of a modern person is well adapted to work and walking upright. Upright walking is an adaptation to the most important feature of human life - work. It is he who draws a sharp line between man and higher animals. Labor had a direct impact on the structure and function of the hand, which began to influence the rest of the body. The initial development of upright walking and the emergence of labor activity entailed further changes in the entire human body. The leading role of labor was facilitated by the partial transfer of the grasping function from the jaws to the hands (which later became organs of labor), the development of human speech, and the consumption of artificially prepared food (facilitates the work of the masticatory apparatus). The cerebral part of the skull develops in parallel with the development of the brain and sensory organs. In this regard, the volume of the cranium increases (in humans - 1,500 cm 3, in apes - 400–500 cm 3).
Upright walking
A significant part of the characteristics inherent in the human skeleton is associated with the development of bipedal gait:
- supporting foot with a highly developed, powerful big toe;
- hand with a very developed thumb;
- the shape of the spine with its four curves.
The shape of the spine was developed thanks to a springy adaptation to walking on two legs, which ensures smooth movements of the torso and protects it from damage during sudden movements and jumps. The body in the thoracic region is flattened, which leads to compression of the chest from front to back. The lower limbs also underwent changes in connection with upright walking - widely spaced hip joints give stability to the body. During evolution, a redistribution of body gravity occurred: the center of gravity moved down and took a position at the level of 2–3 sacral vertebrae. A person has a very wide pelvis, and his legs are widely spaced, this allows the body to be stable when moving and standing.
In addition to the curved spine, the five vertebrae of the sacrum, and the compressed chest, one can note the elongation of the scapula and the expanded pelvis. All this entailed:
- strong development of the pelvis in width;
- fastening the pelvis to the sacrum;
- powerful development and a special way to strengthen the muscles and ligaments in the hip area.
The transition of human ancestors to upright walking entailed the development of the proportions of the human body, distinguishing it from monkeys. Thus, humans are characterized by shorter upper limbs.
Upright walking and work led to the formation of asymmetry in the human body. The right and left halves of the human body are not symmetrical in shape and structure. A striking example of this is the human hand. Most people are right-handed, and about 2–5% are left-handed.
The development of upright walking, which accompanied the transition of our ancestors to living in open areas, led to significant changes in the skeleton and the entire body as a whole.
