From here, with a more detailed look, we can say that synthesizing for collagens in tendon structure begins in the cell membrane of the tenocytes.
In other words, the integrins are like force sensors and, in particular, detect cell withdrawal, allowing the cell to react to these mechanical stimuli. At the same time, various growth factors contribute to the regulation of this mechanical conversion process [ 14 ].
Cross-linkages form between collagen molecules, which are very important for clustering at the fibril level. The cross-links between the fibrils are more complex.
And this cross-link structure of collagen fibrils provides the strength of the tissue and thus ensures that it performs the task of the tissue under mechanical loads. In the newly formed collagen, these cross bonds are less in number, soluble in salt or acid solution, and can easily break with heat. As collagen matures, the number of cross bonds that can dissolve and break down decreases and decreases to the minimum level.
As a result, organized collagen molecules form microfibril, sub-fibrils, and fibrils. The fibrils are also clustered to form collagen fibers, collagen clusters or fascicles, and the tendon. Tenocytes are arranged between these fascicles and aligned in the direction of the mechanical load [ 10 ]. In the cellular structures of tendons, as mentioned above, there is much less amount of elastin than collagen, because the mechanical properties of the tendons depend not only on the architecture and properties of collagen fibers but also on the extent to which this structure contains elastin.
Because the bond has a special function and the nerve roots of the spine, mechanical stresses, stresses, etc.
Blood circulation in tendons is very important, because the current circulation of blood directly affects metabolic activity especially during healing. Therefore, they have a white color when compared to the muscles with a much higher blood vessel density.
However, there are a few factors such as the anatomical location, structure, previously damaged condition, and physical activity level of tendons that contribute to blood supply besides the small amount of vascular structure. There are studies that show that blood flow increases in tendons in the case of increasing physical activity in the literature.
There are more vascular tendons due to their anatomical position or shape and function. The flushing of tendons is primarily derived from the synovium at the point of attachment to the bone or paratenon. However, some tendons feed on the tendon like the Achilles tendon and the paratenon structure, and some tendons are fed by a true synovial sheath they are surrounded. Bone and tendon adhesion is a layer of cartilage where blood flow cannot pass directly from the bone-tendon compound.
Instead, they make anastomosis with the veins on the periosteum and make indirect connections [ 16 ]. In contrast, tendons have a very rich neural network and are often innervated from the muscles in which they are associated or from the local cuticle nerves.
However, experimental studies on humans and animals have shown that tendons have different characteristics of nerve endings and mechanoreceptors.
They play an important role especially for proprioception position perception and nociception pain perception in joints. In fact, studies have shown that there is internal growth in the nervous and vascular systems during the healing of tendon, which causes chronic pain. Internal growth of the vein is an indicator of the tendon trying to heal, but because of this growth, nerves may feel pain in areas without pain before.
This means that the nerves play an important role not only in the proprioception but also in the nociception. Nerve endings are located below the muscle-tendon junction and typically in the bone-tendon junction in the form of Golgi organs, Pacini bodies, and Ruffini endings. Of these, the Golgi organs are only mechanically stimulated by pressure and compression, so that they receive information from the power produced by the muscle.
Pacinian bodies are rapidly adaptive mechanoreceptors due to nerve endings with a highly sensitive capsular end to deformation, thus dynamically responding to deformation, but are insensitive to constant or stable changes. Ruffin termination results from multiple, thin capsule-tipped, and single axons and has slowly adapting mechanoreceptors and thus continues to receive information until a constant warning level is stimulated during deformation [ 17 ].
The tendons are surrounded by loose, porous connective tissue, which is called paratenon. A complex structure, paratenon, protects the tendon and allows shifting tendon cover format. Tendon sheaths consist of two continuous layers: parietal on the outside and visceral on the inside. The visceral layer is surrounded by synovial cells and produces synovial fluid.
In some tendons, the tendon sheath extends along the tendon, while in others it is found only in the binding parts of the bone. The parietal synovial layer is found only under the paratenon in the body regions where tendons are exposed to high friction.
This is called the epitenon and surrounds the fascicles. In regions where friction is less, tendon is surrounded by paratenon only. At the tendon-bone junction, the collagen fibers of endotenon continue into the bone and become a peritendon. The regions of the tendon bonding to the bone consist of a dense connective tissue, which is able to adhere to the hard bone from the dense connective tissue and is resistant to movement and damage.
Although they occupy a small area in size, the areas of adhesion to the bone have a complex structure that is much different from that of the tendon itself. According to the size of the load they carry, they show a different proportion of collagen bundles [ 18 ]. The tendons cling to the bone is a complex event; collagen fibers mix into fibrocartilage, mineralize, and then merge with the bone.
Sticking to the bone is done in two ways. In the first type, the adhesion of many collagen fibers is direct to the bone, while the second type indirectly adheres to the periosteum. In other words, the tendon is attached to the bone in the form of fibrous or indirect adhesion to the metaphysics and diaphysis of long bones or fibrocartilaginous or direct adhesion to the epiphyses of the bone. In fibrous adhesions, while the collagen fibers of the tendon are permanently adhered to the periosteum during bone development, fibrocartilaginous adhesions have a gradual transition from tendon to bone.
This gradual transition in fibrocartilaginous adhesions includes the tendon, decalcified fibrocartilage, calcified fibrocartilage, and four zones of bone, so that the uniform distribution of the load at the adhesion site and the joint movement and the coordination of the collagen fibers are ensured.
However, changes in the fibrocartilaginous structure due to compressive loading vary depending on the adhesion sites of the tendons. This ensures better protection against compressive forces. The complex macro- and microstructure of tendons and tendon fibers make this possible. During various phases of movements, the tendons are exposed not only to longitudinal but also to transversal and rotational forces.
In addition, they must be prepared to withstand direct contusions and pressures. The above-described three-dimensional internal structure of the fibers forms a buffer medium against forces of various directions, thus preventing damage and disconnection of the fibers. Publication types Comparative Study Review. Substances Glycoproteins Glycosaminoglycans Proteoglycans Collagen.
Symptoms of a sprained ligament generally include pain, swelling, and bruising in the affected area. The joint may feel loose or weak and may not be able to bear weight. The intensity of your symptoms will vary depending on whether the ligament is overextended or actually torn.
Doctors classify sprains by grades, from grade 1 a mild sprain with slight stretching of the ligament to grade 3 a complete tear of the ligament that makes the joint unstable. Common areas affected by strains are the leg, foot, and back. Strains are often the result of habitual movements and athletics.
Athletes who overtrain their bodies without adequate time for rest and muscle repair in between workout sessions are at increased risk. Much like a sprain, symptoms include pain and swelling. You may also experience muscle cramping and weakness. Tendonitis, another tendon injury, is an inflammation of the tendon. This can occur as a result of the natural aging process.
Like other parts of the body, tendons weaken as we age, becoming more prone to stress and injury. Tendonitis can also occur from overuse of a tendon. Golfers and baseball pitchers, for instance, often experience tendonitis in their shoulders. Symptoms of tendonitis include pain when the muscle is moved and swelling. The affected muscle may feel warm to the touch. Telling the difference between a ligament or tendon injury on your own can be hard.
Whenever you have pain and swelling, see your doctor for a skilled diagnosis and effective treatment plan. Doctors recommend:. But others are. Take these precautions to protect your tendons and ligaments:. There are thousands of ligaments and tendons throughout the body.
Ligaments and tendons are both made of connective tissue and both can be torn or overstretched, but they differ in function. Ligaments attach one bone to another. Tendons attach a muscle to a bone. Both, however, are essential to proper body mechanics.
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