Joints and ligaments are also distinguished as their constituent parts. The upper limbs consist of: bones of the shoulder, forearm, hands (wrist, metacarpus and phalanges of the fingers).
Characteristics of the humerus
This limb element is a long tubular bone. It consists of the so-called body and 2 epiphyses: the upper proximal and the lower distal. The upper section has a rounded shape, and the lower section has a triangular shape. The shoulder joint is the connection of the upper epiphysis with the glenoid fossa of the scapula. All bones of the skeleton of the upper limbs consist of a body and epiphyses and are connected to each other.
Structure and functions of the ulna
According to their anatomical structure, the ulna and radius bones are classified as the forearm. The ulna consists of many long tubular bones and two ends (proximal and distal epiphysis). The base of the bone is presented in the shape of a trihedron; it has certain edges, which have the following names: anterior (palmar), posterior (dorsal), interosseous (external). The anterior edge of the bone is round in shape. The rear one goes back a little. The interosseous edge has a pointed shape and faces the radius.
Unlike the distal one, the proximal epiphysis is thicker. The trochlear notch, which is located in it, is completely covered with articular cartilage. This is necessary so that the edges of the bone do not wear away with constant movement of the upper limb. The ulnar notch is also located at the ends of the trochlear notch. The anterior surface of the bone, located below the coronoid process, has a tuberous structure.
The upper and lower epiphyses of the radius and ulna interact with each other through joints. Any connection of the bones of the upper limbs is a complex mechanism, especially in the elbow area. If an injury occurs and the bones in the elbow are damaged or shattered, many procedures and surgeries will be performed by specialists before the elbow can function again.
The lateral side (outer surface) of this element of the upper limb includes the radial notch, a notch for the inclusion of the head of the radial bone. This cavity for the front of the bone and the bone itself form the proximal joint of the forearm.
Like the lateral side of the distal epiphysis, the posteromedial section has a styloid process, which is necessary for better ligament of the elements of the limb. We see that the ulna, which together with the radius forms the bones of the upper limb, is very complex. Human anatomy - the structure of all organs and systems, including the bones and joints of its limbs - is not at all elementary.
Radius bone of the upper limb
The difference between the two components of the forearm is that the distal end of the radius is much thicker than the proximal end. This ending forms a rounded head, in which there is an epiphysis with a flat depression. Thanks to this, the bones are properly connected. This head is the surface of the joint. On the anterior side of the radius there is a part that is responsible for the attachment of the biceps brachii muscle. The structural elements of the wrist are connected to the radius through a massive distal epiphysis. The lower epiphyses of the radius and ulna combine to form the radioulnar joint.
Wrist characteristics
The bones of the human upper limbs consist of short elements arranged in 2 rows (proximal and distal) and have an unusual shape. At the wrist it is presented in the form of a curved groove, the convexity of which faces the back of the hand.
In the proximal row there are small bones, which are named after their shape: lunate, scaphoid, triquetrum. In addition, there is also a pisiform bone, which adjoins the palmar surface to the triangular element. The distal row is formed by the trapezoid, capitate and hamate bones. To perform their functions, all of the listed structural components are ordered so that they are not in the same plane. The carpal bones of the proximal row of human upper limbs form an elliptical convexity. It connects to the distal epiphysis of the radial part of the upper limb. And at the distal row, the bones articulate with the metacarpal.
Bones of the upper limb
The metacarpal phalanges of the fingers are formed by tubular bones (with one epiphysis), which have a body, a base, and a head. They are curved, with their convex side facing the back of the hand. The distal row of carpal bones is connected to their bases, and the heads are connected to the beginning of the phalanges. The heads are adjacent to the bases of the proximal phalanges, and their head part articulates with the beginning of the distally located phalanges. Each finger has 3 phalanges: proximal, middle, distal. However, they only have two.
Each phalanx, like all other bones of the upper limbs, the anatomy of which is described above, also has a base, body and head. But their peculiarity is that they are lined up one after another. In this case, there is only one true epiphysis for all three phalanges. The proximal carpals have a single fossa where they connect to the next bone. The middle and distal phalanges are slightly different from the proximal ones, as they have two pits to form a joint. These recesses are flat in shape and separated by small scallops. Each last phalanx in the finger is slightly narrowed, flattened and rough on top.
Bones of the free upper limb, their connection
All bones are connected to each other by joints, this allows a person to move unlimitedly. The connection of the bones of the upper limbs, clavicle and scapula is represented by the combination of two paired joints: the articulation of the sternal ends of the clavicle with the manubrium of the sternum and its acromial ends with the acromions of the scapula. The next ligament of the scapula, the superior transverse one, has the shape of a short thin bundle thrown over the notch of the scapula. The opening for the passage of nerves and vessels is formed by the transverse ligament with the notch and very often ossifies. In humans, the structure of the bones of the upper limbs is very diverse.
The acromioclavicular joint can move in any direction, but the frequency of movement is small. They are hindered by the coracoclavicular ligament. It is divided into quadrangular and triangular ligaments. The quadrangular one has the shape of a trapezoid, and the triangular one has the shape of a cone. Both ligaments are located at an angle towards each other.
Description of the shoulder joint
The shoulder joint plays an important role in the movement of the bones of the upper limb. The shoulder joint is formed by the head of the humerus and the glenoid cavity of the scapula. This depression is oval in shape, occupies one quarter of the area of the head, and is slightly concave. The labrum present in it increases the congruence of the connecting tissues covered with hyaline cartilage. The joint capsule has freedom of movement, so when the bone is lowered, it can gather into folds. It is strengthened by the muscles and ligaments located in the shoulder joint. The head of the humerus is tightly fixed by muscles and ligaments in the glenoid cavity. There are no muscles in the anterior lower part of the shoulder joint. It is surrounded by mucous bags that interact with the articular cavity.
Blood enters the shoulder joint through the anterior and posterior arteries located around the shoulder bone. This connection of bones is very mobile, it is characterized by the following actions: rotation, circular movements, extension, flexion, abduction, adduction. In humans, the bones of the upper and lower extremities are slightly different, but the joints are the same in structure.
Elbow joint complexity
The elbow joint is formed by the union of the humerus, ulna and radius bones. Inside this large joint there are three small joints:
- humeroulnar;
- brachioradial;
- radioulnar.
Due to the presence of a joint capsule and a common cavity, they are combined into a complex joint covered with hyaline cartilage.
The humeroulnar and humeroradial joints, working together, determine flexion and extension, and the radioulnar joint participates in the movements of the forearm. Various movements are due to the presence of a large number of muscles. Such a complex mechanism cannot exist without support. And the joint has this support in the form of the ulnar and radial ligaments. They wrap around the heads of the bones of the upper limb. Human anatomy is designed in such a way that it prevents the joint from bending in the opposite direction.
How are the bones of the forearm connected?
The radius and ulna are located next to each other, and their ends are connected at the joint. The epiphyses of these structures are connected by distal and proximal joints. To ensure the strength of the connection between these bones there is a membrane, which is the beginning of the deep muscles of this part of the upper limbs. The upper connection (proximal) is an integral part of the elbow joint, and the lower one acts independently. The distal radioulnar joint is separated from the radiocarpal joint by a small articular disc. It is shaped like a triangle with concave plate surfaces.
The structure of the wrist joint
The carpal bones are connected to the radius through the articular disc and the surfaces of all members of the connection. The proximal rows of carpal bones are strongly connected to each other, so the articular surface is one area on the side of the wrist. It is naturally smaller than the surface of the radius, so the triangle-shaped disc helps connect the two different sized articular areas. In addition, it helps to separate the ulna bone, which is surrounded on all sides by ligaments, from the joint.
What joints are involved in connecting the bones of the hand and fingers?
The bones of the hand are connected to each other using three joints:
- Midcarpal. It is located between the bones of the first and second rows of the wrist. There are many ligaments on the two surfaces of the wrist (palmar and dorsum). This is due to the fact that the hands are actively functioning, they must perform small movements, bend and unbend. This strong ligamentous apparatus is called the radiate carpal ligament.
- Carpometacarpal. Four have one capsule and articular plane. The joint of the thumb is separated from the rest.
The bones of the fingers are connected to each other using the metacarpophalangeal and interphalangeal joints. In addition to them, there are also a large number of strong ligaments on each finger, which allows a person to bend and straighten his fingers. As you can see, the structure of the human upper limbs is quite complex, but due to this they are distinguished by mobility.
The upper limbs of a person allow you to perform various movements that are necessary to perform the most simple or complex actions.
To understand the diseases of the bones of this department, it is important to know the structure of the skeleton of the upper extremities.
The upper limbs are the most mobile, so its role in the human body is significant.
The main function of the upper limbs is the ability to make extensive movements with the hands, which is necessary when performing various types of work activities.
The skeleton of the arms allows a person to perform flexion and extension, adduction and abduction, circular movements and rotation of the upper limbs.
There are also biological functions of the skeleton, which consist in the participation of bones in metabolic processes, as well as in hematopoiesis.
Upper limbs: skeletal structure
In the skeleton of the limbs, a free part and a belt are distinguished.
The girdle of the upper limbs includes the scapula and. The scapula is a bone adjacent to the sternum, located at the level of the second to seventh rib. This bone is similar to a triangle and therefore has an upper, lateral and lower angle. The clavicle consists of a rounded body, as well as the acromial and sternal ends.
The free part consists of the following sections:
- Distal part
- Average
- Proximal
The distal part is the carpal bones. There are carpal, metacarpal and digital bones in this part of the skeleton. The carpal bones consist of eight spongy but short bones, which are arranged in two rows. The metacarpal rings are also short tubular rings. They have two sections - the body and the head.
The number of finger bones is five. The thickest and shortest bone is at the first (thumb) finger. From it the count is made: second (index), third (middle), fourth (ring) and fifth (little finger).
The main function of the upper limb skeleton is to provide a variety of arm movements
The middle part of the skeleton consists of two types of bones: the radius and the ulna. They are the bones of the forearm. The ulna begins from the fifth finger, its upper end is thickened, and has two branches - the coronoid, which is located in front and the ulna, located behind.
The radius bone is located on the side of the first finger (thumb).
The proximal part of the skeleton includes bone. The shoulder joint is formed by the socket of the scapula and the head of the humerus.
The humerus is a tubular bone. It contains the body, as well as the lower and upper ends, which are separated from the body by the so-called anatomical neck. Below there are small elevations - the small and large tubercle, which are separated by the intertubercular groove.
Pathologies in the structure of the skeleton
Diseases of the skeletal parts of the upper extremities can be congenital or acquired.
Congenital pathologies include club-handedness. It is caused by shortened tendons, ligaments or muscles of the palmar radius, as well as an abnormal phenomenon such as the absence of the ulna or radius. This is extremely rare; most often these bones are underdeveloped.
Amelia or phocomelia is a pathology in which a limb is completely or partially absent.
Syndactyly, ectrodactyly and polydactyly are also considered congenital defects. With syndactyly, the shape of the fingers is disrupted, or fusion of the finger bones is impossible. Ectrodactyly is characterized by the absence of bone in one or more fingers. With polydactyly, there is an increase in the number of fingers on the hand.
The following pathologies in the structure of the skeleton are distinguished:
- Among diseases of the upper extremities, osteochondropathy should be highlighted. This disease is a necrotic aseptic process that occurs in spongy bones, which has a chronic form and leads to microfractures.
- The most common pathologies of the bones of the upper extremities are dislocations. They can be either congenital or acquired. The first type of fracture occurs during difficult childbirth. Also, during labor there may be a fracture of the shoulder. Acquired fractures are divided into open and closed.
- Diseases of the shoulder joint include periarthrosis of the glenohumeral joint. This disease often leads to a complication – calcification.
Neoplasms - chondroma, osteoidosteoma, chondroblastoma - benign, sarcoma - malignant, which affect the bones of the upper extremities.
Among the diseases of the elbow joint, bursitis is often diagnosed, which is usually provoked by prolonged injuries in sports, as well as injuries to the shoulder area at work.
Experts say that common diseases of the skeleton of the upper extremities are arthrosis, the cause of which is most often inflammatory processes inside the joints. Arthritis that affects the wrist joint area is also particularly common.
– a disease of the hand, characterized by an inflammatory process that occurs in an acute form.
Phlegmon of the hand is considered a dangerous pathology of the hand. The disease is usually a complication of felon tendon. Phlegmon between the fingers quickly spreads into the deep tissue of the palm. If the tendon sheath is affected, then pus can penetrate into the wrist area and forearm.
Pathologies in the skeletal structure of the upper extremities are characterized by a mass of unpleasant symptoms that significantly reduce a person’s quality of life. If a patient notices signs of pathology in the upper extremities, he should contact a specialist who will make the correct diagnosis, which will prevent complications.
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The skeleton of the upper limbs includes the shoulder girdle and the skeleton of the arm. The shoulder girdle consists of the scapula and clavicle, andskeleton hand- from the shoulder, forearm and hand. The hand is divided into the wrist, metacarpus and fingers.
Fig. 30. Bones of the arm from the front in its three positions. A - shoulder in the middle position, with a slight rotation of the forearm forward and inward; B - the shoulder is turned forward and inward; B - shoulder in the middle position, forearm turned outward:
/ - clavicle, 2 - upper angle of the scapula, 3 - inner edge of the scapula, 4 - lower angle of the scapula, 5 - humerus, 6 - internal epicondyle of the humerus, 7 - trochlea of the humerus, 8 - coronoid process of the ulna, 9 - radius bone, 10 - styloid process of the radius, 11 - trapezoid bone, 12 - phalanges of the thumb, 13 - phalanges of the fingers, 14 - metacarpus* 15 - head of the ulna, 16 - ulna, 17 - tuberosity of the radius, 18 - neck of the radius bones, 19 - head of the radius, 20 - capitate eminence of the humerus, 21 - external epicondyle of the humerus, 22 - surgical neck, 23 - crest of the lesser tubercle, 24 - head of the humerus, 25 - greater tubercle, 26 - humeral process of the scapula, acromion, 27 - wrist, 28 - styloid process of the ulna, 29 - coracoid process of the scapula, 30 - anatomical neck. 31 - lesser tubercle of the humerus, 32 - coronoid fossa, 33 - olecranon process of the ulna
The shoulder blade is a flat, triangular-shaped bone located on the back. The clavicle is a tubular bone, one end of which articulates with the sternum and ribs, and the other with the scapula. In children, the costoclavicular joint appears from 11 to 12 years of age; It reaches its greatest development in adults, especially those engaged in physical labor, and in athletes when exercising the shoulder girdle and arms.
The arm skeleton consists of the humerus (shoulder skeleton), the ulna and radius bones (forearm skeleton), and the bones of the hand.
The wrist is made up of 8 small bones arranged in 2 rows, which form a groove on the palm and a bulge on its back surface. The metacarpus consists of 5 small tubular bones, of which the thumb bone is shorter and thicker, the second bone is longer, and each of the following bones is smaller than the previous one, with the exception of the first finger, consisting of two phalanges; four fingers have 3 phalanges. The largest phalanx is proximal, the smaller one is the middle one, and the smallest one is the distal one. On the palmar surface, inside the tendons between the metacarpal bone of the thumb and its proximal phalanx, there are also permanent sesamoid bones and non-permanent ones - between the metacarpal bone and the proximal phalanx of the II and V fingers.
One of the bones of the wrist also belongs to the sesamoids - the pisiform, embedded in the tendon of the muscle in the lower row at the ulna. These bones especially increase the leverage of the muscles attached to them, and the opposition of the thumb to the other four distinguishes the human hand from higher animals as an organ of labor and ensures the grasping of objects.
In a newborn, the clavicle is almost completely bone; in its sternal section, the ossification nucleus is formed at 16-18 years of age and merges with its body at 20-25 years of age. The ossification nucleus of the coracoid process fuses with the body of the scapula at 16-17 years of age. Synestosis of the acromial process with its body ends at 18-25 years.
In a newborn, all long bones (humerus, radius, ulna) have bony diaphyses and cartilaginous epiphyses. There are no bones in his wrist. Ossification of the cartilage of the wrist begins in the 1st year of life in the capitate and hamate bones, at 2-3 years - in the triquetrum, at 3-4 years - in the lunate bone, at 4-5 years - in the scaphoid, at 4-6 years - in polygonal large and at 7-15 years old - pisiform. Sesamoid bones in the first metacarpophalangeal joint appear at 12-15 years of age. At 15-18 years of age, the lower epiphysis of the humerus merges with its body and the upper epiphyses merge with the bodies of the bones of the forearm. Ossification of the proximal and distal epiphyses of the phalanges occurs in the 3rd year of life.
“Bone age” is determined by the ossification centers of the hand. Ossification ends in the clavicle, scapula and humerus at 20-25 years, radius - 21-25, ulna - 21-24, carpal bones - 10-13, metacarpus - 12, phalanges - 9-11. It ends in women on average 2 years earlier than in men. The last centers of ossification are found in the clavicle and scapula at 18-20 years, the humerus - 12-14, the radius - 5-7, the ulna - 7-8, the metacarpals and phalanges of the fingers - 2-3 years. Ossification of the sesamoid bones usually begins during puberty: in boys at 13-14 years old, and in girls at 12-13. The beginning of the fusion of parts of the 1st metacarpal bone indicates the beginning of puberty.
The timing of ossification of the arm bones should be taken into account when teaching children labor movements and physical exercises, as well as writing and drawing. For example, gymnastics lengthens the hand. Children should not perform physical exercises or labor movements that disrupt the normal ossification process.
The humerus is the longest and largest bone of the upper limb. Its proximal part connects to the scapula (in the glenoid fossa). The distal end is the pulley (which is similar to a bobbin) and capitulum (or head), which are part of the elbow joint along with the radius and ulna. On each side of the trochlea there are medial and lateral epicondyles of the humerus, which are easily palpable.
Humerus: a) front view; b) rear view
Radius
The radius is one of the two bones of the forearm and is located laterally, or on the thumb side of the forearm. The proximal head of the radius forms an articulation with the head of the humerus. The radius crosses the ulna during pronation.
Elbow bone
The ulna is the medial bone of the forearm on the side of the little finger. At the proximal end of the ulna there are two processes: the coronoid process and the olecranon process, which lie over the two medial rounded "spools" of the humerus trochlea. The olecranon process, which protrudes strongly when the elbow is flexed, is also called the “musical bone” because when the nerve crossing the olecranon process is irritated, a painful sensation occurs. The styloid processes of the radius and ulna can be felt as sharp projections on either side of the wrist.
Right elbow: medial view at right angle flexion
Carpal bones
Eight small carpal bones make up the wrist. They are connected by ligaments and are arranged in two transverse rows, four bones per row. The first row consists of the scaphoid, lunate, triquetrum and pisiform bones. The second row consists of the trapezium, trapezoid, capitate and hamate bones. The memory pattern for the wrist joints (from lateral to medial) begins with the proximal row.
Metacarpal bones
Five metacarpal bones located between the wrist and the knuckles of the fingers (which are the heads of the metacarpals).
Phalanges of fingers
Each finger has three phalanges, the thumb has only two.
Brush (back view)
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Bones of the forearm and hand (front view)
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Bones of the forearm and hand (back view)
The girdle of the upper limb, cingulum membri superioris, consists of the scapula and clavicle. The medial end of the clavicle is movably connected to the sternum, the lateral end is connected to the scapula, which is connected to the chest through muscles.Figure: Skeleton of the upper limb (right), front view.
1 - collarbone; 2 - blade; 3 - humerus; 4 - ulna; 5 - radius; 6 - carpal bones; 7 - metacarpal bones; 8 - phalanges of fingers.
The scapula, scapula, is a thin, flat, triangular bone that is loosely laid between the muscles, articulating movably with the lateral section with the clavicle and humerus. There are two surfaces in the scapula: the anterior, costal, facies costalis, facing the ribs, and the dorsal, facies dorsalis, facing posteriorly. One of the edges, the medial one, margo medialis, with a freely hanging arm, is located almost parallel to the spine at the level from II-III to VII-VIII ribs. The second edge is the upper one, margo superior, facing upward and has a notch, incisura scapulae, sometimes turning into a hole through which the suprascapular nerve passes. The third edge is the lateral one, margo lateralis, the thickest of all the edges, bifurcated along the entire length and downwards into roughness on the costal and dorsal surface of the scapula. These three edges converge at angles, of which the lower, angulus inferior, is rounded and extended downwards, the upper, angulus superior, ACUTE, facing upward, lateral, angulus lateralis, thickened, equipped with an articular cavity, cavitis glenoidalis, for articulation with the head of the humerus . The glenoid cavity is separated from the scapula by the cervical cavity, collum scapulae. Above and below the glenoid cavity there are two tubercles: the supraglenoid, tuberculum supraglenoidale, to which the tendon of the long head of the biceps brachii is attached, and the subarticular, tuberculum infraglenoidale, the place of attachment of the tendon of the long head of the triceps brachii. Between the lateral angle and the notch there is a coracoid process, processus coracoideus, of a curved shape, the initial section of which is directed upward and forward, the final section is directed forward and outward. This process is connected to the scapula by means of cartilage until the age of 13-15.
The costal surface of the scapula is concave, especially in the upper lateral region, and is called the subscapular fossa, fossa subscapularis. The bundles of the subscapularis muscle begin in it. The dorsal surface of the scapula, facing posteriorly, is convex and divided by the scapular spine, spina scapulae, into two fossae: a smaller supraspinatus, fossa supraspinata, and a larger one, occupying approximately the lower ⅔ of the surface, infraspinatus, fossa infraspinata.
The scapular spine is more expanded on the lateral side, where it passes at an angle into the humeral process, acromion. At the apex of the process there is a small oval-shaped articular surface for connection with the acromial end of the clavicle.
Ossification. The scapula has three most constant points of ossification: in the body, the coracoid process and the lower angle with the adjacent part of the medial edge. In the body, the ossification point appears in the 2nd month of intrauterine development, in the coracoid process - in the first year of life, in the region of the lower angle and medial edge - in the 15-17th year. The coracoid process fuses with the body at 14-16 years of age, the lower angle and medial edge - at the 21-25th year of life.
The clavicle, clavicula, is a curved tubular bone located between the sternum and the acromial process of the scapula. The clavicle has a middle part and two ends: the sternal, extremitas sternalis, facing the sternum, and the humeral, extremitas acromialis, facing the acromial process of the scapula. The sternal end is more widened and massive compared to the humeral end, and is equipped with a saddle-shaped articular surface for connection with the sternum. The humeral end is thickened and bears an articular surface for connection with the humeral process. The upper surface of the clavicle is smooth, on the lower there is a conical tubercle, tuberculum conoideum, - the place of attachment of the ligaments. The part of the clavicle located near the sternal end is convex forward; the section closest to the acromial end has a convexity directed backwards.
Ossification. The clavicle has two ossification points: in the body and the epiphysis facing the sternum. The ossification point in the body appears first in the entire skeleton at the 6th month of intrauterine development, at the sternal end at 16-20 years, fusion with the body occurs at 21-25 years of life.
BONES OF THE FREE UPPER LIMB
The free upper limb consists of three sections. The proximal section is the shoulder, the middle section is the forearm, and the distal section is the hand. The skeleton of the shoulder is formed by the humerus, the bones of the forearm, ossa antebrachii, consist of the radius and ulna. The skeleton of the hand, manus, includes the bones of the wrist, metacarpus and phalanges of the fingers.
Brachial bone
The humerus, humerus, is a long tubular bone, in which there is a body - the diaphysis and two ends - the epiphyses: the upper (proximal) and the lower (distal). The upper end connects to the scapula, the lower end to the bones of the forearm. At the upper end of the humerus there is a head, caput humeri, facing upward and medially, covered with hyaline cartilage and representing almost half a ball. The head is separated from the rest of the upper end of the humerus by an anatomical neck, collum anatomicum. Behind it there are two tubercles: the large one, tuberculum majus, facing outward, and the small one, tuberculum minus, facing forward. The hillocks continue downwards into ridges: the large hillock, crista tuberculi majoris, and the small hillock, crista tuberculi minoris. Between the crests and tuberosities there is an intertubercular groove, sulcus intertubercularis, which is the site of passage of the tendon of the long head of the biceps brachii muscle.
The body of the humerus, corpus humeri, is cylindrical in the upper part and triangular in the lower part. Approximately in the middle of the anterior lateral surface of the body there is a deltoid tuberosity, tuberositas deltoidea, a trace of the attachment of the deltoid muscle. Behind the tuberosity on the posterior surface there is a groove of the radial nerve, sulcus n. radialis, which extends spirally from top to bottom from the medial to the lateral edge. Where the upper end meets the body is the surgical neck, collum chirurgicum, so named because bone fractures most often occur in this area. The lower end of the humerus - the condyle, condylus humeri, has a triangular shape with the base facing downwards. Its lateral sections form the medial and lateral epicondyles, epicondyli medialis et lateralis, which are the origin of the muscles of the forearm and ligaments of the elbow joint. The medial epicondyle, larger in size, bears the groove of the ulnar nerve on the posterior side, sulcus n. ulnaris. At the base of the lower end of the humerus there are located: medially - the block of the humerus, trochlea humeri, - the articular surface for articulation with the ulna, laterally - the head, capitulum humeri, - the articular surface for the radius. On the posterior surface of the lower end, above the trochlea, there is a fossa of the olecranon process, fossa olecrani, into which the process of the ulna bone enters. On the anterior surface there are two fossae: the coronal, fossa coronoidea, and the radial, fossa radialis.
Ossification. The humerus has seven ossification points, of which one appears in the body (7-8th week of intrauterine development), three in the upper (proximal) epiphysis, three in the lower (distal). In the upper epiphysis they appear sequentially in the region of the head, in the region of the greater and then lesser tuberosity (2-5 years), in the lower epiphysis - in both padondyles and trochlea (8-12 years). At 18-20 years of age, these islands of ossification merge.
Bones of the forearm
The ulna is located on the medial side of the forearm, the radius on the lateral side. Both bones are long tubular bones, which have an upper proximal and lower distal end, or epiphyses, and a body, the diaphysis. The ends of the radius and ulna are at different levels. In the proximal section, the upper end of the ulna is located higher; in the distal section, the lower epiphysis of the radius occupies a lower position. The ends of the bones are connected to each other through joints. Along the remaining length between the bones there is a connective tissue interosseous membrane.
Elbow bone
The proximal end of the ulna, ulna, is massive and widened. It connects to the trochlea of the humerus. It has two processes: the upper - ulnar, olecranon, and the lower - coronoid, processus coronoideus, which limit the trochlear notch, incisura thochlearis, open anteriorly. The olecranon process can be easily felt under the skin, the coronoid process is covered by the muscles located around the elbow joint. For articulation with the head of the radius, on the lateral side of the coronoid process there is a radial notch, incisura radialis. Below the notch there is a crest of the supinator muscle for attachment of the muscle of the same name. In front and below the coronoid process, a tuberosity, tuberositas ulnae, is defined for the attachment of the tendon of the brachialis muscle.
The body of the ulna is triangular in shape and has anterior, posterior and medial surfaces separated from each other by edges. The distal end is significantly smaller than the upper, bears a head, from the medial side of which a styloid process, processus styloideus, extends, which can be easily palpated under the skin. On the lateral surface of the head there is an articular circle, circumferentia articularis, which articulates with the ulnar notch of the radius. The ulna can be easily palpated under the skin at the back along the entire length from the ulna to the styloid process. The front of the bone is covered with muscles and tendons.
Radius
The upper proximal end of the radius, radius, forms a head, caput radii, equipped at the top with a flat fossa for articulation with the head of the humerus. On the lateral surface of the head there is an articular circle, circumferentia articularis, for articulation with the notch of the ulna. Somewhat below the head, the radius forms a neck, collum radii, below and medial of which there is a tuberosity, tuberositas radii, for attachment of the biceps tendon.
The body of the radius is curved, with a convexity facing laterally. It has three surfaces, anterior, posterior and lateral, separated by three edges. The lower, distal end of the radius is thickened, forming on the lateral side a styloid process, processus slyloideus, and on the medial side - an ulnar notch, incisura ulnaris, for the head of the ulna. From below, the distal epiphysis has a carpal articular surface, facies articularis carpea, covered with cartilage, for articulation with the bones of the proximal row of the wrist. In the radius, you can feel the head and its entire lower section with the styloid process under the skin.
Ossification. In each of the bones of the forearm, five ossification points appear: one in the body (end of the 2nd month of intrauterine development) and two in the epiphyses (2-19 years). First, ossification points appear in the radius (2-5 years), then in the ulna (5-19 years), and the lower epiphyses are the first to ossify. The fusion of the epiphyses with the body occurs in the reverse order: first, the upper epiphyses of the ulna grow (14 years), then the upper epiphyses of the radius (18-19 years), and at the 21st year - the lower epiphyses of both bones.
Hand bones
Hand bones, ossa manus include the bones of the wrist, metacarpus and phalanges.
Carpal bones
The wrist, carpus, consists of 8 small short bones, ossa carpi, located in two rows: proximal and distal. The bones of the wrist have a variety of sizes and shapes, which is reflected in their names. The proximal row of carpal bones (counting from the thumb side) includes: the scaphoid, os scaphoideum, the lunate, os lunatum, the triquetrum, os triquetrum, and the pisiform, os pisiforme. The pisiform bone is one of the sesamoid bones embedded in the tendon of the muscle. The bones of the proximal row (except for the pisiform), connecting with each other, form an arch, the convex surface of which is connected to the radius, the concave surface to the bones of the distal row of carpal bones. The distal row consists of: trapezium bone, os trapezium, trapezoid, os trapezoideum, capitate, os capitatum, and hooked, os humatum, bones. The upper surface of the bones of this row is covered by an arc formed by the bones of the proximal row, the lower surface, which has a stepped nature, is connected to the bones of the wrist.
The carpal bones have articular surfaces to connect to each other and adjacent bones. On the scaphoid and trapezoid bones there are tubercles on the palmar side, and on the hamate there is a hook, hamulus, which serves for the attachment of tendons and ligaments. The bones of the wrist are located so that on the palm side the wrist is concave in the form of a groove or groove, on the back it is convex. The carpal groove, sulcus carpi, is bounded on the medial side by the pisiform bone and the hook of the hamate bone, on the lateral side by the tubercles of the trapezium bone and the scaphoid bone. It serves for the passage of tendons, blood vessels and nerves. It is difficult to palpate the carpal bones individually. The easiest bone to palpate is the pisiform bone, which is located under the skin in the superomedial corner of the palm and moves when palpated. On the palmar side, when flexing and extending the hand, a tubercle of bone is felt - the trapezium, on the back side - the capitate and triquetral bones.
Ossification. The carpal bones have one ossification point in each of them. Ossification points appear first in the capitate and hamate bones (at the 1st year of life), the last - in the pisiform (at 12-13 years).
Metacarpal bones
The metacarpus, metacarpus, consists of 5 metacarpal bones, ossa metacarpalia, tubular in shape. The name of each of them corresponds to their serial number, counting from the thumb (I-V). The metacarpal bone has a body and two ends. The body of the metacarpal bones is irregularly triangular in shape, concave on the palmar side. The proximal end, the base, is connected to the second row of metacarpal bones, and the distal end, the head, caput, is connected to the proximal phalanx. The articular surfaces of the bases of the II - IV metacarpal bones are flat, saddle-shaped. At the base of the third metacarpal bone there is a process that projects between the capitate and trapezoid bones. The articular surface on the head is convex; on its lateral sections there are roughnesses for attaching ligaments. The shortest is the I metacarpal bone, the longest is the III.
Phalanges of the fingers
Each finger consists of phalanges, phalanges digitorum manus. The first finger has two phalanges - proximal and distal, the rest have three - proximal, middle and distal. The largest sizes are in the proximal phalanges, the smallest - in the distal ones. Each phalanx is shaped like a tubular bone and has a body, corpus phalangis, flattened from front to back, and two ends: proximal - base, basis phalangis, and distal - head, caput phalangis. The heads of the first and second phalanges have the shape of a block, and the third - tuberosities, tuberositas phalangis distalis. The bases of the first phalanges bear articular surfaces in the form of pits for articulation with the heads of the metacarpal bones. At the bases of the second and third phalanges, the articular surface corresponds to the trochlear surface of the heads of the first two phalanges that articulates with it and has a guide ridge. At the level of the joints between the metacarpal bones and the proximal phalanges of the first, less often the fifth and second fingers on the palmar side there are sesamoid bones.
Ossification. The bones of the metacarpus and phalanges of the fingers have two ossification points - in the body and in one of the epiphyses. The ossification point in the body occurs at the 2-3rd month of intrauterine development, in the epiphysis at 3-10 years of age, and in the II-V metacarpal bones, the centers of ossification are located in the head, and in the I metacarpal bone and all phalanges - in the bases . The fusion of the body with the epiphysis occurs at 18-21 years. The sesamoid bones of the first finger receive ossification points at 12-16 years of age.
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