Anatomy of the hand: the relationship between structure and function
Ruki is a perfect and extremely complex structure that allows a person not only to cope with most tasks, but also to indirectly cognize the world around him: touch, touch, evaluate. What determines the functionality of the hands, what features of the anatomy do you need to know in order to maintain their health and be able to develop certain skills? Consider the structure of the upper limbs, starting with the shoulder girdle and ending with the phalanges of the fingers.
Human hand anatomy: basic components
Anatomically, the arm is the upper limb of the human musculoskeletal system. Like most parts of the body, it is formed by bone and muscle structures, ligaments, cartilage and tendons, as well as a network of blood capillaries and nerve fibers that provide tissue nutrition and impulse transmission, respectively.
For a more detailed study of the anatomy of the hand, it is customary to classify into several key areas:
Each of these zones is connected in series with the others through complex joints. It is thanks to this that the arms can remain mobile, maintaining a wide trajectory of movement.
The structure and function of the shoulder girdle
The shoulder girdle is the place where the torso transitions to the upper limbs. It consists of two shoulder blades – right and left – and the same number of collarbones. Thanks to them, support is provided for the position of the arms relative to the body, as well as their movement along three different axes.
The scapula is a flat, triangular bone located on the back. Its relatively small thickness increases towards the lateral edge, where the place of articulation with the head of the humerus is located. The articular cavity, surrounded by tubercles, supports the humerus and allows circular movements with the hands.
The scapula itself is slightly curved outward in the direction from the costal arches. On its outer side there is a key bone axis, on both sides of which powerful supraspinatus and infraspinatus muscle fibers are attached. The rest of the muscle groups, as well as the ligaments supporting the shoulder, are attached to the forward-facing coracoid process.
Another bone of the shoulder girdle – the clavicle – is tubular and has a slightly curved S-shape. It lies horizontally and slopes slightly downward in the neck area. The clavicle serves as a link between the sternum and shoulder blades, and also supports the muscular frame of the shoulder girdle.
Anatomy of the bones and muscles of the arm in the shoulder area
Shoulder – The upper part of the arm, connected directly to the torso. In the elbow joint, it passes into another area – the forearm. The shoulder consists of a large tubular bone, the shape of which changes depending on the zone: if closer to the scapula the section of the humerus has an almost perfectly rounded shape, then closer to the forearm it looks more like a triangle with rounded corners.
The shoulder accounts for most of the physical activity during work, so its muscular system is represented by strong, durable and powerful muscles that are easily amenable to physical development and improvement. The main part of the fibers surrounds the humerus, parallel to the vertical axis. The skin in this area is relatively thin, therefore, in physically developed muscular people, the attachment points and the main bends of the muscles stand out noticeably. It is believed that the volume and relief of the forearm is directly proportional to the strength of a person, but this is not entirely correct: the basis of physical strength is not the size of the muscles, but their training, the ability to quickly contract and relax when exposed to high loads.
Shoulder functions are varied and include almost the full range of arm movements. To understand how this system functions, let’s look at the anatomy of the key muscles through which certain actions are carried out.
Biceps is the biceps muscle of the shoulder, both heads of which tightly cover the upper part of the humerus. Two biceps heads – short and long – begin at the shoulder joint, and approximately in the middle of the humerus, they intertwine together, descending to a circular eminence on the forearm.
By contracting and relaxing the muscle fibers that form the biceps, a person can do the following:
move palms up, rotate and unbend them;
bend your shoulder;
raise your arms forward and up, including with a load.
The triceps, or triceps muscle of the shoulder, consists of three heads of different lengths that cover the elbow and partially the shoulder joints from the back of the hand. The medial and lateral fusiform heads of the triceps originate in the region of the humerus, and the long one is fixed on the protrusion of the scapula. They, like the heads of the biceps, merge into one system in the lower part of the shoulder, forming a tendon attached to the olecranon of the forearm bone.
The functions of the triceps are as follows:
straightening the arm parallel to the vertical axis of the body;
bringing the hand to a position near the body.
This muscle is located directly under the biceps and comes out to the surface of the muscular skeleton only at the attachment point in the lower segment of the humerus. It is not so powerful compared to the biceps, but it also plays a key role in the physiological capabilities of the arm – thanks to its rhythmic contractions, a person can raise the ulna and bend the forearm.
As the name suggests, this group of muscle fibers connects the shoulder and elbow joints along the entire length of the humerus. Its main function is to bend the arm at the elbow during contraction. You can notice this muscle on the surface of the cubital fossa – its ridge is especially pronounced when lifting weights.
The area of the upper limb that begins at the elbow and ends at the wrist is called the forearm. It is formed by two bones of different diameters – radial and ulnar. The cut of the ulna has a triangular shape with a thickening at the upper end, at the point of articulation with the humerus. In front of the elbow joint there is a small block-shaped notch that limits the extension of the elbow, preventing non-physiological overstretching of the muscles of the forearm and shoulder.
The radius, on the other hand, thickens downwards, in the wrist joint. They are connected to the ulna in a flexible manner, thanks to which the hand can rotate up to 180 degrees.
In normal condition, the forearm has a flattened shape with a noticeable expansion upward. This configuration is due to the specific location of muscle tissue: closer to the elbow joint there are massive muscle abdomens, which narrow and pass into the tendons in the wrist. Due to this, by the volume of the lower part of the forearm, one can judge how developed the bony structure of the hand is – thin wrist zones are characteristic of people with anatomically weak bones, and vice versa.
The muscles of the forearm are divided into 3 key groups. The fibers that control flexion and extension of the wrist and fingers are located in the front, the extensor muscles in the back, and the group responsible for the movement of the opposed thumb to the side.
Human Arm Bones: Anatomy of the Hand
The hand is one of the most anatomically challenging areas of the hand. It can be conditionally divided into 3 functional areas:
The wrist is the distal part of the hand, formed by the carpal, metacarpal bones and phalanges. It includes 8 small spongy bones arranged in 2 rows. Their small size and soft articulation allow for the development of hand motor skills, honing the skills of more delicate work.
The metacarpus includes 5 short tubular bones that connect the wrist and fingers (one bone goes to each finger of the hand).
The toes are made up of phalanges of various lengths. The thumb is formed by only two phalanges – proximal and distal, the rest of the fingers also have a third phalanx – the middle one. The longer the fingers are, the thinner and longer their phalanges will be.
The complex structure of the muscle fibers of the hand, with the assistance of the muscles of the forearm, provides a full range of finger movements. Visually, these muscles are difficult to train: unlike biceps, triceps and other large groups of fibers, they do not protrude above the surface of the arm and do not increase in volume. Nevertheless, these muscles are easy to develop: it has been proven that with regular performance of work related to fine motor skills, the fingers become more precise and mobile, and with constant physical activity aimed exclusively at the forearm and shoulder, the hand muscles, on the contrary, atrophy.
The abilities of human hands are immense. Hundreds of nerve endings that crown the hands on the palms contribute to the meticulously honed motor skills. However, even more “rough” work is impossible without the participation of a person’s hands, because strong muscles allow a person to lift and move weight, in some cases exceeding his own. With their help, a person can cognize the world around him through one of the most significant senses – touch. By developing these skills, you can significantly expand your own capabilities, but this process is impossible without knowledge and understanding of the anatomy of the hands.