Foot is the most distal part of the lower limb of a person. This means that it is farthest from the center of the body. It is the feet that account for the entire load of the body mass. Therefore, such a seemingly 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 proceeding to the anatomy of the innervation of the foot, its other departments should be disassembled. The foot, like any other musculoskeletal system in the human body, consists of the following parts:
- bone skeleton;
- joints
- striated muscle;
- vascular formations: veins, arteries, capillaries;
- nerves.
Bone frame
In order to fully understand the innervation and blood supply to the foot, one should understand what basic bone structures it consists of. After all, the large nerves and vessels are mainly located along the bones and have similar names.
Three sections are distinguished on the foot:
- tarsus;
- metatarsus;
- phalanges of the fingers.
The tarsal region is located most proximal, that is, directly under the ankle joint. The line that distinguishes between 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.
Tarsus is composed of 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 wedge-shaped and one scaphoid. In the second row is only one cuboid bone.
The metatarsal part of the foot is located in the middle between two other departments. It consists of five seeds of approximately the same shape and size. Each of them includes three parts: the head, body and base.
The phalanges of the fingers consist of the smallest bones. Each phalanx includes three bones. The exception is only the big toe, which consists of only two bones. This finger is also called the first and is indicated by the Roman numeral I. The little finger, respectively, is indicated by the number V.
Core muscles
The main task of the nerves involved in the innervation of the foot is aimed precisely at the transmission of impulses to the muscular frame. After all, it is precisely due to the arrival of nerve impulses that muscle contraction is possible, and therefore human walking.
There are five muscle groups on the foot:
- lateral;
- back;
- front
- surface layer;
- deep layer.
The long and short peroneal muscles belong to the lateral group. Their reduction provides abduction, outward rotation (pronation) and bending of the foot.
The front group consists of the following muscles:
- a long extensor of the thumb, due to which it is possible to extend both the first toe of the foot, and the foot as a whole by raising its upper edge;
- front tibial, which provides extension of the foot;
- long extensor of the fingers, due to which it is possible to extend the toes of the foot from the second to the fourth, as well as raising the outer edge and leading to the side.
The muscles of the surface layer are involved in the formation of the Achilles tendon, due to which movements in the ankle joint are ensured.
The deep layer of muscles consists of a long flexor of the fingers (provides the foot to rotate outward and flexes it), a long flexor of the first finger (performs the function in accordance with the name), and the posterior tibial muscle (flexion of the foot and adduction).
Features of blood supply
The innervation of the foot and the course of arteries in it are inextricably linked, since in most cases the artery, vein and nerve go in the same direction. Therefore, you 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, according to their name, carry blood to the plantar of the foot. The medial vessel has two branches: deep and superficial. The deep carries blood to the muscle, which removes the big toe, and to the short flexor of the fingers. The superficial branch supplies only the muscle that diverts the thumb with blood.
The lateral plantar artery supplies blood to most of the sole. At the base of the metatarsus, it forms a plantar arch, from which many small branches depart to various structures of the foot. Plantar metatarsal arteries branch off from this arc, 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 divided into two own arteries.
The dorsal artery of the foot carries blood to the dorsum. 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 respectively to the lateral and median surfaces of the foot.
Another branch of the dorsal vessel of the foot is the arched artery. From it, by analogy with the plantar vessels, the rear metatarsal arteries depart, which are divided into the digital arteries.
The nerves of the rear foot
We begin the examination of the nerves of the most distal limb with the innervation of the rear of the foot. But first you need to figure out what the external landmarks of this site are. The inner edge is limited by the tuberosity of the scaphoid, it is easy to palpate, especially in thin people. At the outer border, it is easy to see the tuberosity of the fifth metatarsal bone.
The innervation of the skin of the foot, namely its back departments, is carried out due to the following nerves:
- subcutaneous 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 departs from the tibial nerve. From the subcutaneous nerve, the impulses go to the middle part of the ankle and the medial area of the tarsus. In some people, this nerve is longer and ends already at the base of the first finger.
The medial cutaneous dorsal nerve passes through the midfoot and is divided along its length into branches that go to the skin of the dorsum of the thumb and partially to the second and third toes.
The intermediate cutaneous dorsal nerve is divided into digital branches, which stretch to the areas of the third and fourth, as well as the fourth and fifth toes of the foot facing each other.
The lateral dorsal cutaneous nerve carries an impulse to the lateral surface of the fifth finger.
A feature of the innervation of the human foot, namely its rear, is its significant variability. For example, some people lack a dorsal cutaneous nerve.
Nerves of the sole of the foot
The innervation of the muscles of the foot of the plantar is provided by the plantar nerves: medial and lateral. Both of these nerve trunks extend from the tibial nerve.
The medial nerve runs along the mid plantar canal and forms a small arc. The beginning of this arch corresponds to the base of the first metatarsal bone, and its end corresponds to the middle of the fourth metatarsal bone. During the median nerve, medial calcaneal branches depart from it. They provide the transmission of nerve impulses to the mid sole of the heel.
The medial nerve carries impulses to the muscle that takes the thumb away, as well as to the short flexor of the fingers. Interestingly, in young children, several branches immediately leave to the superficial flexor. Then branches extend from the medial plantar nerve, which innervate the surfaces facing each other from the first to fourth fingers. These branches are called the first, second and third common digital plantar nerves. The innervation of the fingers 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 up several branches: the digital nerve of the lateral edge of the fifth finger, the 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 - 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, the sensitive sphere, trophism of the skin and muscles.
Perhaps the development of mononeuropathy (damage to one nerve) or polyneuropathy (multiple lesions of several nerve fibers at once).
Causes of neuropathy
There can be many 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 salts of heavy metals: lead, mercury, arsenic;
- endocrinological diseases: diabetes mellitus, thyroid pathology;
- severe liver disease;
- prolonged deficiency of vitamins and nutrients;
- side effects of certain drugs: Amiodarone, Isoniazid, cytostatics;
- severe infectious diseases: diphtheria, HIV infection, mumps;
- autoimmune diseases in which antibodies are produced against own cells in the body: systemic lupus erythematosus, dermatomyositis, rheumatoid arthritis;
- genetic predisposition.
Symptoms of Neuropathy
The clinical manifestations of neuropathy depend on which particular nerve function is impaired: sensitive, 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, symptoms will spread higher.
Sensitive disorders are manifested as follows:
- Painful sensations of a pulling or aching nature, which correspond to the innervation zone of the affected nerve.
- The so-called paresthesias - a feeling of creeping crawls on the skin, tightening, twisting of the foot. Sometimes these feelings 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 innervation zone of the affected nerve: pain, temperature, tactile.
- Sensory ataxia sometimes develops. This is a condition in which a person is worried about shakiness 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 orientation of the parts of the body in space.
For motor disorders, the following manifestations are characteristic:
- tremor and muscle cramps, the innervation of which is impaired;
- with a long ongoing process, muscle weakness develops;
- flaccid paralysis - the patient loses the ability to move the foot;
- decrease in reflexes, which is detected by a neurological examination.
Due to impaired muscle innervation, deformity of the foot due to muscle atrophy develops. Atrophy occurs both due to inaction of the muscle during paralysis, and due to damage to the trophic function of the corresponding nerve.
The consequences of an innervation disorder
Long-term disorder of the innervation of the toes and other parts of the lower extremities can lead to irreversible consequences. The restoration of nerve function is a rather complicated and not always feasible process, especially with untimely and incorrect treatment.
Atrophic changes in the area of the feet first lead to dry skin. Then ulcers and cracks appear, which heal very hard. If you do not adhere to the rules of personal hygiene, an infection can get there.
With prolonged inaction of the foot, restoration of its function is difficult. So, paralysis of the lower extremities may 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 physiotherapy exercises.
Pain and unpleasant paresthesia can lead to psychological problems in the patient. Therefore, sometimes there is a need for taking antidepressants.
Conclusion
Feet are a really important part of the human body. Therefore, not only a medical professional, but also an average person should know the general principles of the anatomy of the foot, especially 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.