Bones of the pastern: structure and functions

What are the dice bones? What functions do they perform? The answers to these and other questions can be found in the article. The brush is the distal part of the arm, the skeleton of which consists of metacarpal bones, fingers (phalanges), and wrists.

Structure

What are the dice bones? We will answer this question further, and now we will find out the structure of the wrist. It consists of eight spongy short bones, arranged in two lines, four in each:

• Upper: triangular, scaphoid, semilunar, pea-shaped;
• Lower: capitate, trapezoid, hook-shaped, trapezoidal.

The lower endings of the radius and elbow are linked to the carpal bones, forming a wrist joint, in which it is possible to make revolutions along all three axes. Bones of the lower line are attached at the top to the bones of the upper, below - to the knuckles of the pastern, and also to each other, forming small-knobby joints.

The next bone line is formed by the bones of the pastern. There are only five, according to the number of fingers. Their basis is connected to the bones of the wrist. Just like the metacarpal bones, the phalanges of the fingers are tubular short bones. Each finger has three phalanges: proximal (base), middle and distal or terminal (nail). Only the thumb is an exception, since it is formed by two phalanges - the nail and the main phalanx. Between the phalanges of each finger and the metacarpal bone are formed mobile joints.

Bones of the pastern

How many bones are included in the pastern? It consists of five metacarpal bones. The most oblong is the second bone of the pastern, and the shortest is the metacarpus of the thumb (the first one), which differs in its massiveness.

The remaining knuckles towards the elbow border of the hand decrease in length. Each metacarpal bone has a head, a base and a body. Their bases are articulated with carpal bones. The articular surfaces of the bases of the fifth and first metacarpals have saddle contours. The rest of the surface is flat articular. The metacarpal bones have heads that differ in a hemispherical articular surface and are connected to the proximal bones of the fingers.

View details

So, we continue to study the pastern. How many bones does she have? We already know that five metacarpals form a pastern. By type they refer to tubular short bones with a single real epiphysis (bones monoepiphysical). They are called in order - I, II, III and so on, starting from the first finger.

At the proximal extremities of the bases of II-V bones, there are articular flat facets that serve as a connection with the bones of the second wrist line, and those that are placed on the sides are for communication with each other. The basis of the first knuckle of the pastern has an articular saddle-shaped form and joins the carpal trapezoid bone, but there are no lateral facets here.

The base II of the pastern bone forms a cutout in the form of a corner, encompassing the carpal bone. On the basis of the V metacarpal base, on its ulnar side, there is a tubercle. On the head of metacarpal bones there are articular convex surfaces necessary for articulation with proximal bones of the fingers. On the sides of the heads there are rough recesses - the places of attachment of ligaments.

Tubular bones

It is known that the tubular small bones include the bones of the pastern and phalanx of the fingers, as well as metatarsal bones. To the tubular long bones belong femoral, fibular and tibia, as well as the ulnar, humerus and ray. Oblong bones of the legs make up about half of human growth.

What are the tubular bones? These bones are triangular or cylindrical, the width of which is shorter than the length. They have epiphyses on the extremities covered with hyaline articular cartilage, and grow mainly due to an increase in the length of the body (diaphysis). Between the diaphysis and the epiphyses are metaphyses, in childhood and pubertal age containing epiphyseal cartilaginous plates.

Structure

So, you already know how many human bones (pasterns) participate in the movement of the fingers. And what is the structure of the tubular bone? Outside, it is covered with a periosteum - a layer of connective tissue. The bony epiphysis is represented mainly by bone spongy substance containing the bone red brain, diaphysis with bone compact substance. In the center of the diaphysis there is a bone marrow canal, which in adults is filled with a bone marrow of yellow color. This substance contains fat cells.

Brush

The bones of the pastern and phalanx of the fingers refer to the skeleton of the hand. What are the bones of the fingers? These are small, placed one after the other bones with a single real epiphysis (mnepepifazarnye bones). They are called phalanges. Each finger has three phalanges: middle, distal and proximal. The thumb is an exception, since it has only two phalanges, distal and proximal. In all animals it is weakly developed and reaches its maximum growth only in humans.

The base of the proximal bone carries a joint single fossa, which is needed to connect with the globular head. At the bases of the distal and middle phalanges there are two flat grooves, fenced off by a comb. They are attached to the heads of the middle and proximal phalanges, which grow in the form of a block with a depression in the center.

The end of the phalanx is flattened and roughened. In the area of interphalangeal and metacarpophalangeal joints of the hand, where tendons are attached, there are sesamoid bones. They are constant on the first finger and changeable on others.

Ball joints of the hand

The brush has metacarpophalangeal joints, which are formed by the bases of the proximal phalanges of the fingers and the heads of metacarpal bones. All these joints have three mutually perpendicular axes of rotation, around which there is separation and reduction, circumduction (circular motion), straightening and bending, and they also have a spherical shape. Extension and flexion are possible at 9-100 °, reduction and retraction - by 45-50 °.

Collateral ligaments strengthen the metacarpophalangeal joints and are located on each side of them. On the palm side, the capsules of these joints have additional ligaments, which are called the palms. Their fibers are interwoven with the fibers of the transverse deep metacarpal ligament, which inhibits the divergence of the knuckles of the pasterns to the sides.

Flat joints

Every person should know how many bones are included in the pastern. And what are the wrist-metacarpal joints of the hand? This is the articulation of the distal line of carpal bones with the bases of the metacarpal. These joints are inactive and have a flat shape, minus the carpometacarpal joint of the first finger. The magnitude of the motions in them does not exceed 5-10 °. Lability in these joints, as well as between the carpal bones, is localized with superbly developed ligaments.

Bundles placed on the surface of the palm form a strong ligamentous palmar apparatus. It attaches wrist bones to each other, as well as to the metacarpal bones. The head bone of the ligamentous apparatus is central. It is attached to her most of the ligaments.

The back ligament of the hand is much less developed than the palmar ligament. They unite their wrists and are part of thick capsules that cover the joints placed between these bones. To the second line of the wrist bones, besides the palmar and dorsal bones, interosseous ligaments are also attached.

The bones of the distal wrist line and the four (II-V) pastern bones are not very manoeuvrable in relation to each other and are tightly connected to the integral device constituting the main bone nucleus of the bone. In this regard, they are marked as a solid base of the brush.

The polygonal bone and the base of the first bone of the pastern form the wrist-metacarpal joint of the first finger of the hand. The surfaces of the joints have saddle contours. In the joint, such movements are possible: withdrawal and reduction, reverse movement (reposition) and opposition (opposition), as well as circumduction (circular movement).

The thumb is opposed to all the other fingers, so the amount of grasping movements of the brush is significantly increased. The parameters of mobility in the carpometacarpal joint of the first finger are 45-60 ° with reduction and retraction and 35-40 ° with reverse movement and opposition.