Limbs Anatomy

1. Limbs Anatomy By Asst. Lecturer. Mays Ibrahim

2. Fascial Compartments of the Upper Arm • The upper arm is divided into an anterior and a posterior fascial compartment, each having its muscles, nerves, and arteries. • Contents of the Anterior Fascial Compartment of the Upper Arm Muscles: Biceps brachii, coracobrachialis, and brachialis Blood supply: Brachial artery Nerve supply to the muscles: Musculocutaneous nerve Structures passing through the compartment: Musculocutaneous, median, and ulnar nerves; brachial artery and basilic vein. The radial nerve is present in the lower part of the compartment.

5. Contents of the Posterior Fascial Compartment of the Upper Arm • Muscle: The three heads of the triceps muscle • Nerve supply to the muscle: Radial nerve • Blood supply: Profundabrachii and ulnar collateral arteries • Structures passing through the compartment: Radial nerve and ulnar nerve • Structures Passing through the Posterior Fascial Compartment: Radial Nerve (The origin of the radial nerve from the posterior cord of the brachial plexus in the axilla)

6. The Cubital Fossa • The cubital fossa is a triangular depression that lies in front of the elbow • Boundaries Laterally: The brachioradialis muscle Medially: The pronator teres muscle The base of the triangle is formed by an imaginary line drawn between the two epicondyles of the humerus. The floor of the fossa is formed by the supinator muscle laterally and the brachialis muscle medially. The roof is formed by skin and fascia and is reinforced by the bicipital aponeurosis.

7. The Cubital Fossa Contents The cubital fossa contains the following structures, enumerated from the medial to the lateral side: • the median nerve. • the bifurcation of the brachial artery into the ulnar and radial arteries. • the tendon of the biceps muscle. • the radial nerve and its deep branch. • The supratrochlear lymph node lies in the superficial fascia over the upper part of the fossa, above the trochlea.

8. Bones of the Forearm The forearm contains two bones: • The Radius • The Ulna.

9. Radius • The radius is the lateral bone of the forearm. • Its proximal end articulates with the humerus at the elbow joint and with the ulna at the proximal radioulnar joint. • Itsdistal end articulates with the scaphoid and lunate bones of the hand at the wrist joint and with the ulna at the distal radioulnar joint.

10. Radius • At the proximal end of the radius is the small circular head. The upper surface of the head is concave and articulates with the convex capitulum of the humerus. The circumference of the head articulates with the radial notch of the ulna. • Below the head, the bone is constricted to form the neck. • Below the neck is the bicipital tuberosity for the insertion of the biceps muscle.

11. Radius • The shaft of the radius, in contradistinction to that of the ulna, is wider below than above. Ithas a sharp interosseous border medially for the attachment of the interosseous membrane that binds the radius and ulna together. The pronator tubercle, for the insertion of the pronator teres muscle, lies halfway down on its lateral side.

12. Radius • At the distal end of the radius is the styloid process; this projects distally from its lateral margin. • On the medial surface is the ulnar notch, which articulates with the round head of the ulna. • The inferior articular surface articulates with the scaphoid and lunate bones. • On the posterior aspect of the distal end is a small tubercle, the dorsal tubercle.

13. Ulna • The ulna is the medial bone of the forearm. • Itsproximal end articulates with the humerus at the elbow joint and with the head of the radius at the proximal radioulnar joint. • Its distal end articulates with the radius at the distal radioulnar joint, but it is excluded from the wrist joint by the articular disc.

14. Ulna • The proximal end of the ulna is large and is known as the olecranon process. this forms the prominence of the elbow. • It has a notch on its anterior surface, the trochlear notch, which articulates with the trochlea of the humerus. • Below the trochlear notch is the triangular coronoid process, which has on its lateral surface the radial notch for articulation with the head of the radius. • The shaft of the ulna tapers from above down. It has a sharp interosseous border laterally for the attachment of the interosseous membrane. • At the distal end of the ulna is the small rounded head, which has projecting from its medial aspect the styloid process

15. Bones of the Hand • There are eight carpal bones, made up of two rows of four. • The proximal row consists of (from lateral to medial) the scaphoid, lunate, triquetral, and pisiformbones. • The distal row consists of (from lateral to medial) the trapezium, trapezoid, capitate, and hamate bones. The bones of the hand are cartilaginous at birth. The capitatebegins to ossify during the first year, and the others begin to ossify at intervals thereafter until the 12th year, when all the bones are ossified.

16. Bones of the Hand • The Metacarpals and Phalanges • There are five metacarpal bones, each of which has a base, a shaft, and a head. • The first metacarpal bone of the thumb is the shortest and most mobile. It does not lie in the same plane as the others but occupies a more anterior position. • The bases of the metacarpal bones articulate with the distal row of the carpal bones; the heads, which form the knuckles, articulate with the proximal phalanges. • The shaft of each metacarpal bone is slightly concave forward and is triangular in transverse section. Its surfaces are posterior, lateral, and medial. • There are three phalanges for each of the fingers but only two for the thumb.

17. The Forearm • Fascial Compartments of the Forearm • The forearm is enclosed in a sheath of deep fascia, which is attached to the periosteum of the posterior subcutaneous border of the ulna. • This fascial sheath, together with the interosseous membrane and fibrous intermuscular septa, divides the forearm into several compartments, each having its own muscles, nerves, and blood supply.

18. Interosseous Membrane • The interosseous membrane is a strong membrane that unites the shafts of the radius and the ulna; it is attached to their interosseous borders. • Its fibers run obliquely downward and medially so that a force applied to the lower end of the radius (e.g., falling on the outstretched hand) is transmitted from the radius to the ulna and from there to the humerus and scapula. • The interosseous membrane provides attachment for neighboring muscles.

19. Flexor and Extensor Retinacula • The flexor and extensor retinacula are strong bands of deep fascia that hold the long flexor and extensor tendons in position at the wrist.

20. Carpal Tunnel • The bones of the hand and the flexor retinaculum form the carpal tunnel. The median nerve lies in a restricted space between the tendons of the flexor digitorumsuperficialisand the flexor carpi radialis muscles.

21. Contents of the Anterior Fascial Compartmentof the Forearm • Muscles: A superficial group, consisting of the pronator teres, the flexor carpi radialis, the palmaris longus, and the flexor carpi ulnaris; an intermediate group consisting of the flexor digitorumsuperficialis; and a deep group consisting of the flexor pollicislongus, the flexor digitorumprofundus, and the pronator quadratus. • Blood supply to the muscles: Ulnar and radial arteries • Nerve supply to the muscles: All the muscles are supplied by the median nerve and its branches, except the flexor carpi ulnaris and the medial part of the flexor digitorumprofundus, which are supplied by the ulnar nerve.

25. Muscles of the Anterior Fascial Compartment of the Forearm

26. Muscles of the Anterior Fascial Compartment of the Forearm

28. Contents of the Lateral Fascial Compartment ofthe Forearm • The lateral fascial compartment may be regarded as part of the posterior fascial compartment. • Muscles: Brachioradialis and extensor carpi radialislongus • Blood supply: Radial and brachial arteries • Nerve supply to the muscles: Radial nerve

30. Contents of the Posterior Fascial Compartmentof the Forearm • Muscles: The superficial group includes the extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, and anconeus. These muscles possess a common tendon of origin, which is attached to the lateral epicondyle of the humerus. The deep group includes the supinator, abductor pollicislongus, extensor pollicis brevis, extensor pollicislongus, and extensor indicis. • Blood supply: Posterior and anterior interosseous arteries • Nerve supply to the muscles: Deep branch of the radial nerve

34. The Region of the Wrist Structures on the Anterior Aspect of the Wrist The following structures pass superficial to the flexor retinaculum from medial to lateral: • Flexor carpi ulnaris tendon, ending on the pisiform bone. (This tendon does not actually cross the flexor retinaculum but is included for the sake of completeness.) • Ulnar nerve lies lateral to the pisiform bone. • Ulnar artery lies lateral to the ulnar nerve. • Palmar cutaneous branch of the ulnar nerve • Palmaris longus tendon (if present), passing to its insertion into the flexor retinaculum and the palmar aponeurosis • Palmar cutaneous branch of the median nerve

35. The following structures pass beneath the flexor retinaculum from medial to lateral: • Flexor digitorumsuperficialis tendons and, posterior to these, the tendons of the flexor digitorumprofundus; both groups of tendons share a common synovial sheath. • Median nerve • Flexor pollicis longus tendon surrounded by a synovial sheath • Flexor carpi radialis tendon going through a split in the flexor retinaculum. The tendon is surrounded by a synovial sheath.

36. Structures on the Posterior Aspect of the Wrist • The following structures pass superficial to the extensor retinaculum from medial to lateral: • Dorsal (posterior) cutaneous branch of the ulnar nerve • Basilic vein • Cephalic vein • Superficial branch of the radial nerve

37. Structures on the Posterior Aspect of the Wrist • The following structures pass beneath the extensor retinaculum from medial to lateral: • Extensor carpi ulnaris tendon, which grooves the posterior aspect of the head of the ulna • Extensor digitiminimi tendon is situated posterior to the distal radioulnar joint. • Extensor digitorumand extensor indicistendons share a common synovial sheath and are situated on the lateral part of the posterior surface of the radius.

38. The Palm of the Hand • Skin • The skin of the palm of the hand is thick and hairless. It is bound down to the underlying deep fascia by numerous fibrous bands. The skin shows many flexure creases at the sites of skin movement, which are not necessarily placed at the site of joints. Sweat glands are present in large numbers. • The palmaris brevis is a small muscle that arises from the flexor retinaculum and palmar aponeurosis and is inserted into the skin of the palm.

39. The Palmar Aponeurosis • The palmar aponeurosis is triangular and occupies the central area of the palm. • The apex of the palmar aponeurosis is attached to the distal border of the flexor retinaculum and receives the insertion of the palmaris longus tendon. • The base of the aponeurosis divides at the bases of the fingers into four slips. Each slip divides into two bands, one passing superficially to the skin and the other passing deeply to the root of the finger; here each deep band divides into two, which diverge around the flexor tendons and finally fuse with the fibrous flexor sheath and the deep transverse ligaments. • The function of the palmar aponeurosis is to give firm attachment to the overlying skin and so improve the grip and to protect the underlying tendons.

41. The Carpal Tunnel • The carpus is deeply concave on its anterior surface and forms a bony gutter. The gutter is converted into a tunnel by the flexor retinaculum. • The long flexor tendons to the fingers and thumb pass through the tunnel and are accompanied by the median nerve. • The four separate tendons of the flexor digitorumsuperficialismuscle are arranged in anterior and posterior rows, those to the middle and ring fingers lying in front of those to the index and little fingers. • At the lower border of the flexor retinaculum, the four tendons diverge and become arranged on the same plane. • The tendon of the flexor pollicis longus muscle runs through the lateral part of the tunnel in its own synovial sheath. • The median nerve passes beneath the flexor retinaculum in a restricted space between the flexor digitorumsuperficialisand the flexor carpi radialis muscles

43. Synovial Flexor Sheaths • In the hand, the tendons of the flexor digitorumsuperficialisand profundus muscles invaginate a common synovial sheath from the lateral side. The medial part of this common sheath extends distally without interruption on the tendons of the little finger. • The lateral part of the sheath stops abruptly on the middle of the palm, and the distal ends of the long flexor tendons of the index, the middle, and the ring fingers acquire digital synovial sheaths as they enter the fingers. The flexor pollicis longus • tendon has its own synovial sheath that passes into the thumb. These sheaths allow the long tendons to move smoothly, with a minimum of friction, beneath the flexor retinaculum and the fibrous flexor sheaths.

44. The Dorsum of the Hand Skin • The skin on the dorsum of the hand is thin, hairy, and freely mobile on the underlying tendons and bones. • The sensory nerve supply to the skin on the dorsum of the hand is derived from the superficial branch of the radial nerve and the posterior cutaneous branch of the ulnar nerve.

45. Elbow Joint • Articulation: This occurs between the trochlea and capitulumof the humerus and the trochlear notch of the ulna and the head of the radius. The articular surfaces are covered with hyaline cartilage. • Type: Synovial hinge joint • Capsule: Anteriorly, it is attached above to the humerusalong the upper margins of the coronoid and radial fossae and to the front of the medial and lateral epicondyles and below to the margin of the coronoid process of the ulna and to the anular ligament, which surrounds the head of the radius. • Posteriorly, it is attached above to the margins of the olecranon fossa of the humerusand below to the upper margin and sides of the olecranon process of the ulna and to the anular ligament.

46. Elbow Joint • Ligaments: The lateral ligament is triangular and is attached by its apex to the lateral epicondyle of the humerusand by its base to the upper margin of the anular ligament. The medial ligament is also triangular and consists principally of three strong bands: the anterior band, which passes from the medial epicondyle of the humerusto the medial margin of the coronoid process; the posterior band, which passes from the medial epicondyle of the humerus to the medial side of the olecranon; and the transverse band, which passes between the ulnar attachments of the two preceding bands. • Synovial membrane: This lines the capsule and covers fatty pads in the floors of the coronoid, radial, and olecranon fossae; it is continuous below with the synovial membrane of the proximal radioulnar joint.

47. Elbow Joint • Movements • The elbow joint is capable of flexion and extension. • Flexionis limited by the anterior surfaces of the forearm and arm coming into contact. • Extension is checked by the tension of the anterior ligament and the brachialis muscle. • It should be noted that the long axis of the extended forearm lies at an angle to the long axis of the arm. This angle, which opens laterally, is called the carrying angle and is about 170° in the male and 167° in the female. The angle disappears when the elbow joint is fully flexed.

48. Proximal Radioulnar Joint • Articulation: Between the circumference of the head of the radius and the anular ligament and the radial notch on the ulna • Type: Synovial pivot joint • Capsule: The capsule encloses the joint and is continuous with that of the elbow joint.

49. Proximal Radioulnar Joint • Ligament: The anular ligament is attached to the anterior and posterior margins of the radial notch on the ulna and forms a collar around the head of the radius. It is continuous above with the capsule of the elbow joint. It is not attached to the radius. • Synovial membrane: This is continuous above with that of the elbow joint. Below it is attached to the inferior margin of the articular surface of the radius and the lower margin of the radial notch of the ulna. • Movements: Pronation and supination of the forearm

50. Distal Radioulnar Joint • Articulation: Between the rounded head of the ulna and the ulnar notch on the radius • Type: Synovial pivot joint • Capsule: The capsule encloses the joint but is deficient superiorly.