The foot is the most distal part of the human lower limb. This means that it is farthest from the center of the body. It is on the feet that the entire load of the body's mass is accounted for. Therefore, such, at first glance, a small part of the body has a very thoughtful structure. Details about the anatomy, blood supply and innervation of the foot - later in the article.
Topographic anatomy
The structure of any structure of the human body should be considered gradually. Therefore, before moving on to the anatomy of the innervation of the foot, it is necessary to disassemble its other departments. The foot, like any other musculoskeletal formation in the human body, consists of the following parts:
- bone frame;
- joints;
- striated muscles;
- vascular formations: veins, arteries, capillaries;
- nerves.
Bone framework
To fully understand the innervation and blood supply of the foot, one should understand what main bone structures it is from.composed. After all, large nerve and vessels are mainly located along the bones and have similar names.
There are three sections on the foot:
- tarsus;
- plus;
- phalanges of fingers.
The tarsal area is located most proximally, that is, directly below the ankle joint. The line that separates these two formations is at the same time the upper edge of the human foot. This line runs along the posterior edge of the calcaneus.
The tarsus has two rows of small bones. The first row, which is located closer to the edge of the foot, consists of the talus and calcaneus. They are larger. In the second row, which is closer to the metatarsus, there are five bones at once, placed in two more rows. The first is represented by four bones: three cuneiform and one scaphoid. There is only one cuboid in the second row.
The metatarsal part of the foot is in the middle between the other two departments. It consists of five bones of approximately the same shape and size. Each of them includes three parts: head, body and base.
The phalanges of the fingers consist of the smallest bones. Each phalanx includes three bones. The only exception is the big toe, which consists of only two bones. This finger is also called the first and is denoted by the Roman numeral I. The little finger, respectively, is denoted by the number V.
Main Muscles
The main task of the nerves involved in the innervation of the foot is aimed specifically attransmission of impulses to the muscle frame. After all, it is precisely due to the receipt of nerve impulses that muscle contraction is possible, and consequently, human walking.
There are five muscle groups on the foot:
- lateral;
- rear;
- front;
- surface layer;
- deep layer.
The lateral group includes the long and short peroneal muscles. Their contraction provides abduction, outward rotation (pronation), and flexion of the foot.
The front group consists of the following muscles:
- long extensor of the thumb, due to which it is possible to extend both the first toe and the foot as a whole by raising its upper edge;
- tibialis anterior, which provides foot extension;
- long extensor of the fingers, due to which extension of the toes from the second to the fourth is possible, as well as raising the outer edge and abduction to the side.
The muscles of the superficial layer are involved in the formation of the Achilles tendon, due to which movements in the ankle joint are provided.
The deep layer of muscles consists of the long flexor of the fingers (provides the foot to turn outward and flex it), the long flexor of the first toe (performs the function according to the name), the posterior tibialis muscle (flexes the foot and adducts it inward).
Features of the blood supply
The innervation of the foot and the course of the arteries in it are inextricably linked, since in most cases the artery, vein and nerve go in onedirection. Therefore, one should know the main vessels of the distal extremities. These include:
- posterior tibial artery;
- anterior tibial artery;
- lateral plantar artery;
- medial plantar artery;
- dorsal artery of the foot.
The posterior and anterior tibial arteries are a continuation of the popliteal artery.
The lateral and medial plantar arteries, as their name suggests, carry blood to the plantar portion of the foot. The medial vessel has two branches: deep and superficial. Deep carries blood to the muscle that abducts the big toe and the short flexor of the fingers. The superficial branch supplies blood only to the abductor thumb muscle.
The lateral plantar artery supplies blood to most of the sole. At the level of the base of the metatarsus, it forms a plantar arch, from which many small branches extend to various structures of the foot. From this arc, the plantar metatarsal arteries branch off, which, in turn, give off branches called "perforating".
From the plantar metatarsal artery at the level of the phalanges of the fingers, the plantar digital artery is formed, each of which is then subdivided into two own arteries.
The dorsal artery of the foot carries blood to the dorsal surface. As a result, it is divided into two branches: the first dorsal metatarsal artery and the deep plantar branch. Also, tarsal vessels depart from it: lateral and medial. They carry blood to the lateral and median surfaces, respectively.feet.
Another branch of the dorsal foot vessel is the arcuate artery. From it, by analogy with the plantar vessels, the dorsal metatarsal arteries depart, which are divided into digital arteries.
Nerves of the dorsal foot
Let's start the examination of the nerves of the most distal limb with the innervation of the dorsum of the foot. But first you need to figure out what are the external landmarks of this site. The inner edge is limited by the tuberosity of the navicular foot, it is easy to palpate, especially in thin people. It is easy to see the tuberosity of the fifth metatarsal on the outer border.
Innervation of the skin of the foot, namely its dorsal sections, is carried out by the following nerves:
- saphenous nerve;
- medial cutaneous dorsal nerve;
- intermediate cutaneous dorsal nerve;
- lateral dorsal cutaneous nerve.
The first three are branches of the superficial peroneal nerve, the last branches off the tibial nerve. From the saphenous nerve impulses go to the middle part of the ankle and the medial part of the tarsus. In some people, this nerve is longer and ends right at the base of the first toe.
The medial dorsalis cutaneous nerve runs along the median region of the foot and divides along its course into branches that go to the skin of the dorsum of the thumb and partly to the second and third toes.
The dorsalis cutaneous nerve nerve divides into digital branches that extend into the facing portions of the third and fourth, as well as the fourth and fifth toes.
Lateral dorsal cutaneous nervecarries impulse to the lateral surface of the fifth finger.
Feature of the innervation of the human foot, namely its rear, is its significant variability. For example, some people lack the dorsal cutaneous nerve.
Nerves of the sole of the foot
Innervation of the muscles of the foot of the plantar part is provided by plantar nerves: medial and lateral. Both of these nerve trunks arise from the tibial nerve.
The medial nerve runs along the median plantar canal and forms a small arc. The beginning of this arc corresponds to the base of the first metatarsal, and its end to the middle of the fourth metatarsal. Along the median nerve, medial calcaneal branches depart from it. They provide transmission of nerve impulses to the median plantar part of the heel.
The medial nerve carries impulses to the abductor thumb muscle and to the flexor digitorum brevis. Interestingly, in young children, several branches go to the superficial flexor at once. Then branches depart from the medial plantar nerve, which innervate the surfaces facing each other from the first to the fourth fingers. These branches are called the first, second and third common digital plantar nerves. The innervation of the toes of the sole of the foot is carried out to a greater extent precisely due to these branches.
The lateral nerve is located between the square muscle and the short flexor of the fingers. It also has two branches: superficial and deep. They depart from the nerve at the base of the metatarsal bone. The superficial nerve gives off several branches: digitalnerve of the lateral edge of the fifth finger, common digital nerve. They innervate the skin on the surfaces of the fourth and fifth fingers facing each other.
What is neuropathy?
Neuropathy of the lower extremities is not a diagnosis, but a collective concept for diseases in which the peripheral nervous system is damaged. First of all, the distal parts of the limbs suffer - the innervation of the lower leg and foot.
The causes of this problem are really many, and clinical symptoms are variable. Neuropathies are manifested by disorders of movement, sensory sphere, skin and muscle trophism.
May develop mononeuropathy (damage to one nerve) or polyneuropathy (multiple damage to several nerve fibers at once).
Causes of neuropathy
There can be a lot of reasons that lead to a violation of the innervation of the foot. The main ones are listed below:
- alcohol abuse;
- drug use;
- prolonged exposure to toxic substances, especially s alts of heavy metals: lead, mercury, arsenic;
- endocrinological diseases: diabetes mellitus, thyroid pathology;
- severe liver disease;
- prolonged vitamin and nutrient deficiency;
- side effects of some drugs: Amiodarone, Isoniazid, cytostatics;
- severe infectious diseases: diphtheria, HIV infection, epidemicmumps;
- autoimmune diseases in which antibodies are produced against the body's own cells: systemic lupus erythematosus, dermatomyositis, rheumatoid arthritis;
- genetic predisposition.
Symptoms of neuropathy
Clinical manifestations of neuropathy depend on which function of the nerve is impaired: sensory, motor or trophic (nutritional). It is noteworthy that the most distal sections are the first to suffer. Therefore, the innervation of the toes will suffer in the first place. With the further development of the disease, the symptoms will spread higher.
Sensory disorders manifest as follows:
- Painful sensations of a pulling or aching nature that correspond to the zone of innervation of the affected nerve.
- The so-called paresthesia - a feeling of crawling on the skin, tightening, twisting the foot. Sometimes these sensations are so unpleasant that patients would prefer leg pain to them.
- Violation of sensitivity. Moreover, there is a simultaneous loss of all types of sensitivity in the zone of innervation of the affected nerve: pain, temperature, tactile.
- Sometimes sensory ataxia develops. This is a condition in which a person is disturbed by unsteadiness when walking due to the fact that he does not feel the position of his feet. This is due to a violation of the deep sense of the orientation of body parts in space.
Movement disorders are characterized by the following manifestations:
- tremor and spasms inmuscles whose innervation is impaired;
- with a long-term process, muscle weakness develops;
- flaccid paralysis - the patient loses the ability to move the foot;
- decrease in reflexes, which is detected during a neurological examination.
Due to violation of the innervation of the muscles, deformity of the foot develops due to muscle atrophy. Atrophy occurs both due to inactivity of the muscle during paralysis, and due to damage to the trophic function of the corresponding nerve.
Consequences of impaired innervation
Prolonged disorder of the innervation of the toes and other parts of the lower extremities can lead to irreversible consequences. Restoration of nerve function is a rather complicated and not always feasible process, especially with untimely and incorrect treatment.
Atrophic changes in the feet first lead to dryness of the skin. Then ulcers and cracks appear, which heal very hard. If you do not adhere to the rules of personal hygiene, infection can get there.
With prolonged inactivity of the foot, the restoration of its function is difficult. So, paralysis of the lower extremities can remain until the end of life. Therefore, in the treatment of neuropathy, attention is paid not only to medical methods of treatment, but also to physical therapy.
Pain and unpleasant paresthesias can lead to psychological problems in the patient. Therefore, sometimes there is a need to take antidepressants.
Conclusion
Feet are a really important part of the human body. Therefore, not only a medical worker, but also a layman should know the general principles of the anatomy of the foot, the features of its blood supply and innervation. It is also necessary to have an idea of what neuropathy is and how it manifests itself in order to seek medical help in time.
