Why tendons are the basis of the anatomical shape of the human body

The ideal structure of the human body provides a special meaning for each anatomical component. Tendons also have their own set of unique functions. This type of tissue is part of the musculoskeletal system, closely related to muscles and bones. Tendons act as a connecting link between muscle fibers and the surface of bones. This way the fabrics are held together and do not slip or come apart. Each tendon is surrounded by a dense, immovable sheath (synovial sheath) that provides hydration, strength and protection.

Contraction or relaxation of muscles pulls the bone along with it precisely due to strong tendon threads. This ensures coordinated, controlled movements of the entire body.

The structure of tendons, their thickness, as well as the margin of safety in different parts of the human body differs. Likewise, in different places, tissues are at greater or lesser risk of injury.

What are human tendons

If we consider the subject from the point of view of medicine and anatomy, then tendons are bundles of collagen fibers of connective tissue. The larger such bundles are, the stronger they are in a specific area. Such tissues are especially powerful in the lower extremities.

Collagen bundles do not have the property of stretching, which makes them even stronger and allows them to reliably perform the function of maintaining body shape by stabilizing the position of muscles and joints. They are needed for the full use of bones as levers, the impulse to which is supplied by the muscles.

In terms of its internal structure, the structure of tendon fibers is similar to any other connective tissue. They are surrounded by a network of blood vessels, nerve canals coming from the periosteum, as well as muscles.

Non-contractile tendon tissue is the main reason to talk about the musculoskeletal framework of the human body, and not about separate systems - muscular and skeletal.

Tendon pain

General information

A tendon is a formation of connective tissue, the terminal structure of striated muscles, with the help of which they are attached to the bones of the skeleton. The tendon consists of compact parallel bundles of collagen fibers, between which are rows of fibrocytes (tendocytes). Type I collagen is most often involved in the formation of tendons; collagen types III and V are also found. Collagen bundles are held together by proteoglycans. Parallel to the course of collagen fibers there are blood vessels with transverse anastomoses. Due to their structure, tendons have high strength and low elongation. The shape of the tendons varies - from cylindrical (usually in long muscles) to flat, lamellar (aponeuroses of the broad muscles).

Pain in tendons due to diseases

Tendon pain is extremely common: this symptom is reported by patients almost as often as high blood pressure. Damage to the tendon apparatus can occur in the form of tendinitis, tendinosis and tenosynovitis. There are three phases in the development of tendinitis :

• development of acute inflammation;
• with an untreated inflammatory process, increased growth of rough connective tissue occurs;
• chronic inflammation and degenerative changes in the tendon can lead to its rupture.

The tendons most commonly affected are the tendons of the shoulder girdle and the upper extremity (especially the biceps brachii tendon). Predisposing factors to such injuries are monotonous movements, long training sessions with insufficient rest breaks, as well as:

• low-quality sports equipment;
• athlete's age;
• wrong technique.

Tendinosis is a non-inflammatory atrophy and degeneration of fibers within a tendon, often associated with chronic tendonitis, which can lead to partial or complete rupture of the tendon accompanied by tendon pain. Tenosynovitis is an inflammation of the paratendon, which is the outer sheath of some tendons and is lined with a synovial membrane (for example, damage to the extensor tendon of the thumb in de Courvain's tenosynovitis). Tendinitis is inflammation or irritation of the tendon, the thick tissue that connects bone and muscle. Tendinitis is most often caused by frequent stress on the affected area, as well as serious injury. There are activities that increase the risk of developing tendinitis:

• gardening
• raking
• carpentry
• shoveling
• painting
• cleaning (scraper or stiff brush)
• tennis
• golf
• skiing.

Poor posture at home and at work, and poor stretching before exercise also increases the risk of developing tendinitis. risk factors include

• deviations in the location and structure of bones (for example, different leg lengths, arthritis of the joint), which increase the load on soft tissues;
• other diseases, for example, rheumatoid arthritis, gout, psoriatic arthritis, thyroid arthritis; the body's reaction to medications;
• It happens that infection causes the development of tendinitis.

Tendinitis can affect anyone, however, it is more common in adults over 40 years of age. Over time, tendons wear out, they become more sensitive to stress, less elastic, and more vulnerable. Tendonitis can affect almost any part of the body where a tendon connects bone and muscle:

• base of the thumb
• elbow
• shoulder
• hip
• knee
• calcaneal tendon.

Symptoms of tendonitis include pain in the tendon and adjacent area. The pain may gradually increase in severity, may come on suddenly and be acute, especially if calcium deposits are present. There is a decrease in shoulder mobility. One of the causes of pain in the tendon is rupture of a healthy tendon, when the load on it becomes prohibitive and exceeds the mechanical endurance of the tissue. Tendons are made of dense fibrous connective tissue.

If the tendon has experienced significant overload for a long time, a degenerative-dystrophic process may develop in it. Degeneration of tendon tissue is promoted by impaired blood supply, metabolic diseases, chronic inflammatory processes and hypothermia.

Tendon rupture A tendon rupture can be complete or incomplete and occur along the course of the tendon or at its attachment to the bone. In this case, separation of the bone fragment does not occur. If the tendon has not been degenerated, separation from its insertion occurs extremely rarely. The following may be subject to such injury:

• supraspinatus tendon at its insertion into the greater tubercle of the humerus
• biceps tendon at its insertion into the acromion of the scapula
• biceps tendon attached to the tuberosity of the radius and to the coracoidal process of the scapula (very rare).
• The triceps brachii tendon may become detached from the olecranon.
• Separation of the tendon stretch (aponeurosis) of the extensor finger is somewhat more common, with dislocation in the interphalangeal joint.

The most common on the lower extremities are:

• tear of the quadriceps tendon, which attaches to the top of the patella
• separation of the Achilles tendon from the tubercle of the calcaneus.

When a tendon , the patient is bothered by pain at the site of the tear, which appears unexpectedly with heavy load, throwing, or jumping. Movement in the affected muscle is impaired and swelling . When the tendon is completely torn off, its end connected to the muscle slips along the muscle, the muscle shortens and rises in the form of a tubercle.

Tendon ruptures along their length, in a place remote from the point of attachment on the upper extremities, are quite rare, and are more often incomplete. Much more often in athletes, ruptures of the tendons of the large muscles of the lower girdle of the extremities occur. There are gaps:

• biceps femoris tendon
• quadriceps tendon
• Achilles tendon ruptures

All these ruptures are accompanied by dysfunction of the muscle, regardless of whether the rupture is complete or incomplete. At the site of the rupture, pain in the tendon, swelling, and hemorrhage occurs.

If you have pain in the tendons, a traumatologist will help you. The patient will undergo an X-ray and receive an accurate diagnosis, as well as minor treatment. Some methods of traditional medicine are quite effective for pain in the tendons. For example, bird cherry juice perfectly relieves inflammation of the tendons. Infuse three tablespoons of fresh bird cherry berries in a water bath (pour a glass of boiling water) for ten minutes. Take two tablespoons of the decoction three to four times a day.

Tendon shapes

There are several different types of collagen bundles in the human body. They differ not only in thickness, as mentioned above, but also in other parameters. Below are the main types of tendons.

• By length: long (clearly visible next to the muscles, provide high mobility), short (hidden inside the muscle tissue, strengthens them). It also happens that the fibers are located at an angle to the muscles, which indicates a mixed type.
• According to the shape of the beam: round, flat or lamellar, ribbon-shaped.
• Fiber width: wide, narrow.

The tendons on the arms are mostly long and narrow, on the legs they are lamellar and wide. The connective tissue on the head is also lamellar, but the fibers are predominantly long. The internal organs along the external contour are shrouded in a variety of flat connecting bundles - aponeuroses.

The strength of collagen tissue increases in humans from childhood to 40 years. Then the reverse process begins. Therefore, older people have weak, inelastic tendons that are susceptible to injury and disease. Children's fibers also have a low strength reserve.

Read also: Symptoms and treatment of ankle arthrosis

Constant physical activity, frequent diseases of the musculoskeletal system, as well as the immune system lead to a decrease in the properties of the tendons.

Where are the tendons located?

Connective tissues permeate the entire human body. Wherever there are muscles and bones, the fibers that hold them together are necessarily present. The most important are the human tendons, which are found in the arms, legs and head.

Brush

Since the movements of this part of the body are predominantly subtle and precise, special control of muscle work is required. The human hand has many small but strong muscles and also consists of a large number of bones. The work of the hand is based on the antagonism of the back and palm, the outer and inner sides.

Tendons are involved in the work of extensor and flexor muscles at various levels, and are involved in active movements in the interphalangeal joints

The strength found in tendons throughout the body is also reflected in the hand area. This type of connective tissue is represented by flat bundles. Despite this, tendons can be easily seen on the hands of people of asthenic type or simply having a low percentage of subcutaneous fat.

Damage to the tendons in the hands presents a certain difficulty for the doctor, since all the fibers are thin and small, which seriously complicates diagnosis and treatment. Today, treating hand injuries with flexor tendon injuries is much easier than working with extensor injuries. The problem with the second type is the high probability of displacement of damaged tissue from anatomically normal places. It is not easy to return the fibers and also to attach them back to the bone surface.

Head

Muscles and tendons follow the shape of the human head. The more muscles there are in a person’s body, the more “muscular” the head becomes.

The following main types of muscles are represented in the head area:

• Chewable. As the name implies, they are designed to provide jaw movement. They surround the joint located between the upper and lower jaw. Thanks to the presence of such a muscle-tendon system, a person speaks and processes food in the mouth. They are also partly involved in the formation of facial expressions. The general outline of the masticatory muscles and tendons can be seen through the skin, especially if it is thin. Their structure is dense, rough, massive.
• Mimic. They are characterized by a fine structure and low density. The main participants in the expression of emotions on the face. They control the lips, eyebrows, forehead, eyelids, and wings of the nose. The role of the tendons that support the “helmet” muscles, a kind of bridge between the muscles of the forehead and the occipital region, is especially important. This is part of the protection of the skull from external influences.

Knee

As with the hand, connective collagen tissue supports the flexor-extensor system of the knee joint. In this case, the tendons entangle the joint capsule itself, touch the ligaments, uniting with them. Due to this, the strength and safety of the knee area is guaranteed during movements.

For many people, the tendons in the knee area suffer as a result of a dislocated joint. This is a common example of complex trauma.

Read also: Treatment of lumbar disc herniation with massage

Foot

Here the tendons are represented by many small bundles. They are similar to the fibers on the brush, but their shape and size are larger. This is understandable, since the daily load on the foot is enormous.

Jumping, running, as well as regular walking require tissues to have great endurance and resistance to external loads. The flexor muscles are located on the plantar zone, the extensors are located on the dorsum of the foot. Connective tissues are also placed accordingly.

Also on the foot is the Achilles or Achilles tendon, which is considered the strongest of all. It connects the heel to the muscles of the lower leg, guaranteeing safety when lifting on tiptoes, jumping, and running loads. More information about the tendons in the leg.

Tendon[edit | edit code]

Tendon

is part of the non-contractile connective tissue of skeletal muscles. With the help of one or more tendons, muscles are connected to the bone skeleton or cartilage. They transmit the movement caused by muscle contraction to the bones or, conversely, the force of gravity acting on the axial skeleton to the muscles.

Tendon structure[edit | edit code]

Rice.
1.9. The structure of collagen fiber There are various forms of tendon.

• Long thin tendons
  - for example, in the muscles of the hand. They provide free mobility of the distal parts of the upper limb, which short tendons cannot provide.

• Short tendons
  - for example, in the deltoid and pectoralis major muscles. These muscles macroscopically have barely visible tendons. In this case, they talk about the beginning of the muscle and the place of attachment.

• Flat tendons
  - the so-called
  aponeuroses
  , have muscles that form the walls of the body.

The tendon consists of 70-80% fibrous connective tissue. The remaining components of the matrix are the main substance (dermatan sulfate, hyaluronic acid and chondroitin sulfate, about 0.5-1%), non-collagenous proteins (fibronectin and tenascin) and cells - tenocytes (tendon tissue cells), fibroblasts, synovial cells (connective tissue membrane cells) and chondroblasts or chondrocytes (cartilage cells). Under the tendon fibers

refers to the majority (95%) of wavy type I collagen fibers, which impart mechanical strength to the tendon.
In addition, the tendon contains elastic fibers (about 1%). Collagen fibers
consist of collagen molecules, which are three protein chains twisted relative to each other (triple helix, each helix has the shape of an a-helix).
A group of fibers join together in the interstitium and form a so-called collagen microfibril. Numerous microfibrils, spirally twisting relative to each other, form a collagen fibril, from which, in turn, collagen fiber is formed (Fig. 1.9). rice.
1.10. Arrangement of collagen fibers in the tendon Collagen fibers have a wavy shape and are located in both long and short tendons parallel to each other. In the aponeuroses, bundles of collagen fibers intersect and look like a lattice.

Thanks to the spiral structure of collagen fibers and their wave-like course, the tendon can stretch by 5% of its length and optimally distribute the forces acting on it. Tensile loads during muscle contractions or passive muscle stretching lead first to tension in the collagen fibers, and then to uniform stretching of the collagen. This mechanism ensures the transfer of applied force between muscle and tendon. The spiral structure gives the tendon (even after straightening the wavy fibers) a very high tensile strength - about 500-1000 kg/cm2. The tendon is very strong and can withstand greater loads than steel cable of the same thickness (van den Berg, 1999). Elastic fibers located between the bundles of collagen fibers (Fig. 1.10) absorb loads and return the tendon fibers to their wave-like shape after they cease. Groups of collagen fibers are united into bundles by a thin layer of unformed connective tissue - endotenonium

.
The bundles, in turn, are surrounded by connective tissue internal peritenonium
and form large (secondary) bundles of fibers.
The external peritenonium unites large bundles into a tendon. All of these connective tissue layers are rich in blood vessels and nerves. The external peritenonium is covered with an additional layer - paratenonium
- which anatomically separates the tendon from the surrounding tissues. The paratenonium is formed by loose, fibrous, well-supplied connective tissue and, due to the presence of synovial cells, can produce fluid similar to synovial fluid. This reduces friction as the tendon glides and prevents loss of muscle contraction force.

The connective tissue sheaths of tendons pass into similar sheaths of muscles without a visible border. Between the bundles of tendon fibers are cells (tenocytes), also called pterygoid cells because of their thin, long cytoplasmic projections, with the help of which they connect with neighboring cells. Tenocytes synthesize collagen and elastic fibers, as well as a small amount of the main matrix substance. The function of the contractile actin and myosin filaments found in them is still completely unknown. Cells of connective tissue sheaths of tendons are represented by fibroblasts

.
In addition, tendon tissue contains non-contractile proteins
(fibronectin and tenascin), which connect the layers of connective tissue and perform a stabilizing function.

With age, the proliferative capabilities of tendon cells decrease. The number of cells and the production of ground substances decrease, and the number of elastic and collagen fibers decreases. As a result, there is an age-related decrease in tensile strength and tensile extensibility of the tendons by approximately 20%. The maximum load capacity of the tendon is also reduced (Weineck, 2003). Only with constant irritation (tension and relaxation) is it possible to maintain the strength of the constantly renewed tendon. With appropriate training, tendon strength can even be increased. Adequate irritation of tendon tissue leads to an increase in the activity of tenocytes and the synthesis of collagen and ground substance - the number of collagen fibrils and fibers increases and the diameter of the tendon increases (Oakes, 1998). Too much non-physiological stress, such as in professional sports, can lead to the replacement of thick collagen fibers with thin ones, resulting in the formation of a more stable but less elastic tendon (van den Berg, 1999). Too high non-physiological loads can often lead to partial ossification of the tendon due to the fact that tendon cells, like osteocytes (bone cells), can react with increased calcification. Tendon strength decreases with ossification and the risk of tendon rupture increases. When the tendon is immobilized or underloaded (for example, when the muscle is inactive), the number of collagen and non-collagen fibers decreases (see “Tip”).

Tendons differ not only in shape (see above), but also in structure

depending on the tissue surrounding them.
Some tendons are composed entirely of tendon tissue. In areas of particularly high stress (for example, in the area of ​​bending bones), a zone of fibrocartilage forms in the thickness of the tendon (
for example, in the biceps brachii tendon in the radius region). If tendons slide over other tissues, primarily bones, tendon sheaths (the tendon bursa of the triceps brachii muscle between its tendon and the olecranon process) are formed to reduce friction.

Advice

:After immobilization for 4 weeks. tendon strength is reduced by approximately 20% (Cunnings and Tillmann, 1992; Tabary, 1972). After 12 weeks During immobilization, the loss of collagen fibers in the tendon reaches 16% (van den Berg, 1999). In addition, due to insufficient mechanical irritation, the organization of collagen fibers is disrupted, which increases the likelihood of injury even with light loads. The previous strength is achieved only after 4-12 months. (Oakes, 1998).

Tendon sheaths[edit | edit code]

rice.
1.11. The structure of the tendon sheath Tendon sheaths are sheaths that surround the tendons and facilitate their sliding. Their function is to reduce friction and pressure of surrounding tissues. They are located in places where the tendon bends or puts pressure on the underlying bones and ligaments. For example, there are a large number of tendon sheaths on the foot and hand. The inner layer of the two-layer connective tissue membrane ( epithenonium

) instead of the external peritenonium surrounds the tendon, and the outer layer is formed
by the external peritenonium
. The outer leaf is additionally reinforced with a paratenonium derivative - a fibrous membrane. The fibrous membrane extends throughout the tendon and is attached to the underlying bone at the sides. In the area of ​​the tendon sheaths of the fingers and toes, dense connective tissue crosswise strands are additionally formed. The epitenonium and peritenium are covered by a synovial membrane, which can secrete fluid similar to synovial membrane. This reduces friction between the sheets and facilitates the sliding of the tendon. Both layers join at the end of the tendon sheath, forming a closed sac. The tendon sheath is attached to the underlying tissues with the help of the so-called mesotenium, through which blood vessels and nerves approach it (Fig. 1.11).

synovial bursae can also reduce friction of surrounding tissues.

.

Synovial bursae[edit | edit code]

Synovial bursae (bursae synoviales)

They are sac-like formations filled with synovial fluid (they are compared to cushions of water).
Like tendon sheaths, their shell consists of two layers: the outer (connective tissue fibrous layer
) and the inner (
synovial layer
).
The latter consists of synovial cells capable of producing synovial fluid, which reduces the friction of these two layers relative to each other. In addition, the bursae redistribute the pressure exerted on them and reduce friction when tissues shift. They are often located between tendons and bones, at the origin and insertion of muscles ( subtendinous bursae
), between fascia (
subfascial bursae
), ligaments (
interligamentous bursae
) and between subcutaneous tissue and underlying tissues (
subcutaneous bursae
). Near the joints, they often merge with each other and communicate with the cavity of the joints (for example, the suprapatellar bursa).

Blood supply and innervation of tendons[edit | edit code]

Tendon tissue, including its connective tissue components, is well supplied with blood and innervated. Vessels and nerves approach it through connective tissue membranes (endotenonium, peri-tenonium, paratenonium) and are located parallel to the tendon fibers. In addition to extratendinous vessels, there are also intratendinous vessels and nerves that anastomose with each other. In the area of ​​the bone-tendon junction they connect with the vessels and nerves of the periosteum and bone. Anastomoses are also formed with the vascular and nervous structures of the tendon sheaths. At the site of fibrocartilage formation in the tendon, tissue nutrition is performed avascularly, i.e. through the processes of osmosis and diffusion. Tendons receive both autonomic and sensory innervation (for example, through Golgi receptors).

Tendon diseases and injuries

Connective tissue problems arise mainly due to high stress or injury. This is a scenario where fiber damage occurs under the influence of external circumstances.

There is also an internal context. Various pathologies of the body, acute and chronic diseases occur in representatives of different ages. The risk group consists of people whose body is weakened, and also if there are simultaneously systematic increased loads on the musculoskeletal system.

There are several diagnoses that reflect tendon lesions. Below are common diseases.

Tendinitis

The mechanism of development of the disease is as follows: the muscles, together with the tendons, experience a long, monotonous load day after day, then, as the safety margin expires, the tissues tear, as if cracking. If the load is not canceled at this moment, the inflammatory process will begin, causing pain, limiting mobility, causing swelling and hyperemia.

Lack of treatment changes the structure of the connective fibers; they become lumpy due to uncontrolled scarring. These tubercles interfere with normal muscle contraction, block movements, and reduce their amplitude. The person begins to hear a strange crunching sound. The tendon in the hand is most susceptible to tendonitis. Examples of harmful monotonous movements are working with a keyboard, playing a musical instrument, milking cows, collecting small parts.

Paratenonitis

Inflammation does not affect the underlying tissue itself, but the sheath of the tendon. It becomes covered with fibrous formations, interfering with normal activity. This is always the result of frequently recurring illnesses and injuries.

As for injuries, they occur from a blow to the tendon area, a sudden movement or a cut. In this case, damage of varying severity may occur. They also differ in symptoms. In all cases, the victim feels pain, swelling is observed, and the area is unable to move in the usual way. The situation is sometimes complicated by internal hemorrhages (this is another factor that provokes paratenonitis).

To assess the condition of tendon tissue and determine the presence of a disease or traumatic injury, doctors turn to modern diagnostic techniques.

1. general examination with detailed palpation,
2. assessment of human motor reactions,
3. ultrasound examination (ultrasound),
4. puncture of the synovial membrane - a kind of “cover” that surrounds the tendon,
5. biopsy,
6. magnetic resonance imaging (MRI),
7. arthroscopy (used if the tissues of the articular area are affected),
8. scanning electron diffraction is ideal for studying collagen fibers of the calcaneal tendon,
9. Radiography and thermography are less commonly used.

Read also: Causes of pain in the tailbone in women

Treatment can be conservative or surgical. This depends on how severe the tendon disease or injury is. It is always recommended to maintain rest, use anti-inflammatory drugs, compresses, and tight bandaging.

In difficult situations, surgery is indicated on the fibers themselves and at the site of attachment of the tendon to the bone. Increasingly, doctors are resorting to plastic surgery using autografts.

Characteristics/Clinical picture

The following are characteristics of tendon injuries depending on the damaged area:

• Zone I: hammertoe;
• Zone II: partial tendon damage without complete rupture;
• Zone III: destruction of the insertion of the extensor tendons at the base of the middle phalanx of the finger, also known as Weinstein contracture (characterized by flexion of the proximal interphalangeal joint, extension or hyperextension of the distal interphalangeal joint);
• Zone IV: injuries are often partial with or without loss of proximal interphalangeal joint extension;
• Zone V: open wounds or blunt trauma (a possible effect of such injuries may be rupture of the sagittal band, accompanied by tendon displacement, causing difficulty when trying to straighten a flexed metacarpophalangeal joint);
• Zone VI: The metacarpophalangeal joint can still be extended by the intertendinous joints;
• Zone VII: physical damage to the extensor retinaculum.

Tendon strengthening

Taking into account the specifics of collagen cells, medicine has developed a set of recommendations aimed at preventing any problems with tendons. The main task is to ensure their training. Its essence comes down to isometry, static muscle tension.

• It is ideal to tone different muscle groups one by one without making any movements. Gradually after this, you can move on to classical gymnastics or full-fledged training. An option for physically developed people is exercises with your own weight, calisthenics.
• The appearance of pain, discomfort, as well as previous diseases of the musculoskeletal system and injuries is a reason to urgently reduce the load on the tendon, no matter what it was before.
• It is important for every person to remember that the musculoskeletal system as such reacts negatively to sudden movements, overloads, and excessive pressure. Accordingly, this should be avoided whenever possible.
• From a nutritional point of view, attention to factors such as avoidance of food chemicals, emphasis on collagen-containing foods, as well as healthy fats (jelly or aspic, agar-agar, liver, fatty fish, yolks) requires attention. It is worth thinking about maintaining calcium levels in the body through supplements or eating dairy products, seeds, nuts, and some dried fruits.

It would be useful to strengthen the body, immunity, timely cure of diseases, and prevent injuries.

Treatment

Patients with extensor tendon injuries can be treated in two ways: surgically or conservatively (namely splinting). The choice of treatment depends on the extent of the damage. In general, open injuries and entire tears require surgical treatment. Closed injuries and partial tendon ruptures require splinting. Both static and dynamic splinting are practiced. The action of the dynamic splint is based on the elastic elements pulling the fingers of the hand to secure them in a certain position. Static splints do not put stress on the finger joints.