HUMAN ANATOMY – VOLUME 1

Fig. 74. Shoulder joint.

A — anterior aspect. 1 — coracohumeral ligament; 2 — coracoacromial ligament; 3 — coracoid process; 4 — scapula; 5 — articular capsule; 6 — humerus; 7 — tendo of biceps brachii; 8 — greater tubercle of humerus.

B — frontal section: 1 — coracoid process; 2 — tendo of long caput of m. biceps brachii; 3 — glenoid cavity; 4 — articular capsule; 5 — intertubercular tendon sheath; 6 — head of humerus; 7 — subdeltoid bursa.

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which encases the tendon of the long head of the biceps muscle, which passes through the articular cavity. The second protrusion is a subtendineal bursa, found at the base of the coracoid process, beneath the tendon of the subscapular muscle.

The shoulder joint is a typical spheroid (ball-and-socket) joint with large amplitude of movement, which is allowed by the loose articular capsule, a large difference in size of articular surfaces and an absence of thick ligaments. It can perform flexion and extension movements about the frontal axis. The total amplitude of these movements is 120°. Abduction and adduction are performed about the sagittal axis with total amplitude of 100°. Supination and pronation are performed about the vertical axis with a total volume of movement of 135°. The shoulder joint can also carry out circumduction. The upper extremity can be raised above the horizontal level only with additional movement in the sternoclavicular joint, because the coracoacromial ligament limits this motion in the shoulder joint.

The elbow joint (art. cúbiti) is formed by the humerus, the radius and the ulna (it is a compound joint). These bones actually form three joints, which are enclosed in a common articular capsule (Fig. 75).

The h u m e r o u l n a r j o i n t is a hinge joint, formed between the trochlea of the humerus and the trochlear notch of the ulna. The h u m e r - o r a d i a l j o i n t is spherical, and is formed between the capitulum of the humerus and the head of the radius. The p r o x i m a l r a d i o u l n a r j o i n t (a r t . r a d i o u l n á r i s p r o x i m á l i s) is cylindrical and is formed by the articular surface on the head of radius and the radial notch of the ulna. The common articular capsule is loose. Proximally it attaches above the articular cartilage of the trochlea of the humerus, thus placing the coronoid and olecranon fossae on the inside of the articular cavity. The lateral and medial epicondyles of the humerus are located outside the articular cavity. On the ulna the articular capsule is attached below the articular cartilage of the coronoid process and along the margin of the trochlear notch. On the radius the capsule is attached at its neck. The articular capsule is strengthened by three ligaments. The u l n a r c o l l a t e r a l l i g a - m e n t (l i g . c o l l a t e r á l e u l n á r e) begins on the medial epicondyle of humerus and attaches to the medial margin of the trochlear notch of ulna. The r a d i a l c o l l a t e r a l l i g a m e n t (l i g . c o l l a t e r á l e r a d i á l e) begins on the lateral epicondyle of the humerus and then divides into two fascicles. The anterior fascicle passes over the neck of the radius and attaches near the external anterior edge of the trochlear notch. The posterior fascicle circles the neck of the radius from behind and entwines into the annular ligament of the radius. The a n u l a r l i g a m e n t o f r a d i u s (l i g . a n u l á r e r á d i i) begins on the anterior edge of the

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Fig. 75. Elbow joint.

A — Anterior aspect. 1 — articular capsule; 2 — ulnar collateral ligament; 3 — ulna; 4-radius; 5 — anular ligament of radius; 6 — radial collateral ligament; 7 — humerus.

B — Sagittal section: 1 — humerus; 2 — articular cavity; 3 — olecranon; 4 — ulna; 5 — radius; 6 — coronoid process; 7 — trochlea of humerus; 8 — articular capsule.

radial notch of ulna, circles the neck of the radius and attaches to the posterior edge of the radial notch.

The elbow joint performs flexion and extension of the forearm at total amplitude of 170°. During flexion the forearm deviates slightly medially, so that the hand is brought to the chest and not the shoulder. This takes place because the block of the humerus has a small furrow, which directs the displacement of the forearm and hand in a spiral fashion. The proximal radioulnar joint is used for rotation of the radius together with the hand about its longitudinal axis. This movement takes place simultaneously with movement in the distal radioulnar joint.

Articulations of the forearm and hand

Bones of the forearm are connected with continuous and discontinuous articulations. The discontinuous junction is the i n t e r o s s e o u s m e m - b r a n e o f t h e f o r e a r m (m e m b r á n a i n t e r ó s s e a a n t e -

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b r á c h i i), which is a strong connective tissue membrane, stretched between the interosseous margins of the radius and ulna.. Below the proximal radio-ulnar joint there is a fibrous cord stretching between the two bones called the o b l i q u e c h o r d a (c h ó r d a o b l í q u a).

Continuous junctions include the distal radioulnar joint, the radiocarpal (wrist) joint and joints of the hand.

The distal radioulnar joint (art. radioulnaris distalis) is formed between the head of the ulna and the ulnar notch of the radius. This joint is separated from the radiocarpal joint by an articular disc, stretched between the ulnar notch of radius and the styloid process of ulna. The joint capsule of the distal radio-ulnar joint is loose; it attaches along the edges of articular surfaces and the joint disc. The capsule usually protrudes proximally between the ulna and radius, forming a s a c c i f o r m r e c e s s.

The proximal and distal radioulnar joints together form a combination cylindrical joint. It performs rotation of the radius together with the hand around the ulna. During this movement the proximal epiphysis of the radius describes an arch about the head of ulna. The average amplitude of rotation in the radioulnar joints (supination and pronation together) is approximately 140°.

The radiocarpal (wrist) joint (art. radiocárpea) is the connection between the forearm and the hand. The joint is formed by the carpal articular surface of the radius, the articular disc (on the medial side), and the proximal row of the carpus (the lunate, triquetral and scaphoid bones). The thin articular capsule attaches along the edges of the articulating surfaces and is strengthened by several ligaments (Fig. 76).

The r a d i a l c o l l a t e r a l l i g a m e n t o f t h e w r i s t (l i g . c o l - l a t e r á l e r a d i á l e) begins on the styloid process of the radius and extends to the scaphoid bone. The u l n a r c o l l a t e r a l l i g a m e n t (l i g . c o l l a t e r á l e u l n á r e) passes from the styloid process of the ulna to the triquetral and pisiform bones of the wrist. The p a l m a r r a d i o c a r p a l l i g a m e n t (l i g . r a d i o c á r p e u m p a l m á r e) connects the anterior margin of the articular surface of the radius with the bones of the proximal row of the carpus and with the capitate bone. The d o r s a l r a d i o c a r - p a l l i g a m e n t (l i g . r a d i o c á r p e u m d o r s á l e) extends from the posterior margin of the articular surface of the radius to the proximal row of the carpus.

In structure the radiocarpal joint is compound ellipsoid, with movement possible about two axes (frontal and sagittal).

Bones of the hand are linked together by numerous joints with differently shaped articular surfaces, which, combined, allow the hand significant mobility.

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Fig. 76. Joints and ligaments of hand.

A — frontal cut of left wrist joint and joints of carpal bones; anterior aspect. 1 — wrist joint; 2 — radius; 3 — ulna; 4 — articular disc; 5 — ulnar collateral ligament; 6 — pisiform; 7 — midcarpal joint; 8 — intercarpal joints; 9 — carpometocarpal joint; 10 — interosseous metacarpal ligaments; 11 — carpometacarpal joint of thumb; 12 — radial collateral ligament.

B — anterior aspect: 1 — distal radioulnar joint; 2 — ulnar collateral ligament of wrist; 3 — pisohamate ligament; 4 — pisometacarpal ligement; 5 — radial collateral ligament of wrist joint; 6 — palmar metacarpal ligaments; 7 — metacarpophalangeal joints; 8 — interphalangeal joints (opened); 9 — fibrous sheath of digit of hand (opened); 10 — tendo m. flexor digitorum profundus; 11 — deep transverse metacarpal ligaments; 12 — collateral ligaments; 13 — carpometacarpal joint of thumb; 14 — hamate; 15 — radial collateral ligament of wrist joint; 16 — palmar radiocarpal ligament; 17 —

radius; 18 — ulna; 19 — interosseus membrane of forearm.

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The midcarpal joint (art. mediocárpea) is formed by articulating surfaces of the first and second rows of carpal bones. It is a compound hinge joint. The articular capsule is thin, especially on the dorsal side. It attaches along the edges of the articular surfaces. The midcarpal and radiocarpal joints are functionally connected.

The intercarpal joints (artt. intercárpeae) are formed between neighboring bones of the wrist. Their capsules attach on the edges of the articular surfaces. The articular cavities of the intercarpal joints communicate with the cavity of the midcarpal joint.

The midcarpal and intercarpal joints are strengthened by many ligaments. On the palmar surface this is the r a d i a t e c a r p a l l i g a m e n t

The intercarpal joints also include the p i s i f o r m j o i n t (art. óssis pisifórmis), which is strengthened by the p i s o m e t a c a r p a l and p i s o - h a m a t e l i g a m e n t s, which are a continuation of the tendon of the ulnar flexor muscle.

The carpometacarpal joints (artt. carpometacarpáles) are formed between articular surfaces on the second row of carpal bones and the bases of metacarpal bones. These are plane (gliding) joints (for the II–V metacarpals) with a common articular fissure (cavity). The articular capsule is taut and thin; it attaches along the margins of articular surfaces. The articular cavity is communicated with articular cavities of the midcarpal and intercarpal joints. The capsule is strengthened by the d o r s a l and palmar carpometacarpalia ligaments (l i g g . c a r p o m e t e c a r p á l i a d o r s á l i a e t p a l m á r i a).

The c a r p o m e t a c a r p a l j o i n t o f t h e t h u m b is a saddle joint formed between the articular surface of the trapezium and the base of the I metacarpal bone. The joint has high mobility (see below).

The intermetacarpal joints (artt. intercarpeae) are formed between adjoining sides of bases of II–V metacarpal bones. Their joint capsule is a continuation of the capsule of the carpometacarpal joints, and is strength-

t h e i n t e r o s s e o u s m e t a c a r p a l l i g a m e n t s (l i g g . m e t a c - a r p á l i a i n t e r ó s s e a). The latter are intra-articular ligaments, which connect adjacent surfaces of the metacarpal bones.

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The metacarpophalangeal joints (artt. metacarpophalangeae) are formed between the bases of proximal finger phalanges and heads of metacarpal bones. The loose joint capsules are attached along the edges of articular surfaces and are strengthened ligaments. On the palmar surface the capsule is thickened by the p a l m a r l i g a m e n t s, and on each side by the c o l l a t e r a l l i g a m e n t s. Between the heads of the II–V metacarpal bones are the deep transverse metacarpal ligaments (ligg. metacarpeae transvera profunda).

The interphalangeal joints (art. interphalangea) are formed between the heads and bases of adjacent phalanges. In structure these are hinge joints. Their articular capsules are loose, attached along the edges of articular cartilages. The capsules are strengthened in front and on the sides by the p a l m a r and c o l l a t e r a l l i g a m e n t s, respectively.

Movement in joints of the hand

Displacement of the hand relative to the forearm is conducted by simultaneous movement in a group of joints, which, for convenience, in clinical practice are called the hand joint.

Characteristics of the joints of the upper extremities are demonstrated in the 6 table.

The carpal joint is ellipsoid, allowing for movements about the frontal and the sagittal axes. Flexion and extension are carried out about the frontal axis with amplitude of 100°, while abduction and adduction are performed about the sagittal axis with the volume of 70°. Circumduction in the carpal joint is conducted through successive movements about the frontal and sagittal axes.

The carpometacarpal joint of thumb is used for opposition and reposition of the thumb relative to the other fingers (about the frontal axis), as well as abduction and adduction of the thumb relative to the index finger (about the sagittal axis). Circumduction in this joint is a result of a succession of movements about the frontal and sagittal axes.

The carpometacarpal joints (II–V) are only slightly movable. The carpometacarpal and intercarpal joints are capable of only insignificant gliding movements. Flexion and extension movements are executed around the frontal axis with a total volume of 90°. Abduction and adduction are conducted about the sagittal axis within limited amplitude. Metacarpophalangeal joints are also capable of circumduction. Movements in the interphalangeal joints are possible about the frontal axis (flexion and extention) with a total volume of approximately 90°.

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Questions for revision and examination

1.Which bones do the clavicle and the scapula articulate with? Name the joints formed between these bones.

2.Describe the structural characteristics of the shoulder joint and how they effect various movements.

3.The formation of which joints do the ulna and radius participate in?

4.Describe the structure of the radiocarpal joint. What ligaments strengthen it?

5.What structural characteristics allow for opposition and reposition of the thumb relative to the other fingers?

ARTICULATIONS OF THE LOWER EXTREMITIES

Articulations of the pelvic girdle

Articulations of the pelvic girdle include the paired sacroiliac joint and the pubic symphysis (Fig. 77).

The sacroiliac joint (art. sacroiliáca) is formed between the auricular surfaces of the sacrum and the pelvis. Its articular capsule is very thick and taut; it attaches around the edges of the articular surfaces, accreting with the periosteum of the pelvis and sacrum. The capsule is strengthened by several thick durable ligaments. The a n t e r i o r s a c r o i l i a c l i g a - m e n t stretch between the front edges of the articulating surfaces. The pos-

l i g a m e n t, stretched on the posterior surface of the joint between the articulating bones. Also there is the i l i o l u m b a r l i g a m e n t, which connects transverse processes of L4 and L5 vertebrae with the iliac tuberosity. In shape of articulating surfaces this is a plane joint. Movement in it, however, is almost impossible, due to the undulation of articulating surfaces and the taut articular capsule and ligaments.

The pubic symphysis (sýmphysis púbica) is a fibrocartilaginous i n - t e r p u b i c d i s c (d í s c u s i n t e r p ú b i c u s), situated between the symphysis surfaces of the pubic bones. This disk has a narrow fissure-like cavity. The pubic symphysis is strengthened by several ligaments. The s u p e r i o r p u b i c l i g a m e n t (l i g . p ú b i c u m s u p é r i o r) stretches transversely upward from the symphysis, connecting the two pubic bones. The i n f e r i o r p u b i c l i g a m e n t (l i g . p ú b i c u m i n f é r i u s) adjoins the symphysis on the bottom.

The pubic symphysis displays clear differences between the male and the female. In women this junction is smaller in height but thicker than in men. In women slight movement is possible in the pubic symphysis during child labor.

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