Upper Limb Anatomy .
[1]. The fore- and hindlimbs were evolved basically for bearing the weight of the body and for locomotion as is seen in quadrupeds, e.g. cows or dogs.
[2]. The two pairs of limbs are, therefore, built on the same basic principle. Each limb is made up of a basal segment or girdle, and a free part divided into proximal, middle and distal segments.
[3]. The girdle attaches the limb to the axial skeleton. The distal segment carries five digits .
[4]. The whole upper limb works as a jointed lever. The human hand is a grasping tool. It is exquisitely adaptable to perform various complex functions under the control of a large area of the brain.
[5]. The unique position of man as a master mechanic of the animal world is because of the skilled movements of his hands . Out of 206 total bones in man, the upper limbs contain as many as 64 bones.
[6]. Each side consists of 32 bones .Since bones of the two upper limbs are similar, one needs to learn only 32 bones out of a total 64 bones.
[7]. One learns only one upper limb, the other upper limb gets learnt on its own. This is true for the whole body except parts of abdomen.
[8]. Actually, one needs to master only 50% of the body and other 50% gets mastered itself .
Parts of the upper Limb .
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| Parts and 32 bones of the upper limb |
It has been seen that the upper limb is made up of four parts:
(1) Shoulder region;
(2) arm or brachium;
(3) forearm or antebrachium; and
(4) hand or Manus.
1 .The shoulder region .
[a] . The pectoral or breast region on the front of the chest;
[b] . The axilla or armpit; and
[c] . The scapular region on the back comprising parts around the scapula.
The bones of the shoulder girdle are the clavicle and the scapula. Of these, only the clavicle articulates with the axial skeleton at the sternoclavicular joint.
The scapula is mobile and is held in position by muscles. The clavicle and scapula articulate with each other at the acromioclavicular joint.
2 .The arm (upper arm or brachium) .
The arm extends from the shoulder to the elbow (cubitus). The bone of the arm is the humerus. Its upper end meets the scapula and forms the shoulder joint.
The shoulder joint permits movements of the arm.
3 .The forearm (antebrachium) .
[1]. The forearm extends from the elbow to the wrist. The bones of the forearm are the radius and the ulna.
[2]. At their upper ends, they meet the lower end of the humerus to form the elbow joint.
[3]. Their lower ends meet the carpal bones to form the wrist joint. The radius and ulna meet each other at the radioulnar joints.
[4]. The elbow joint permits movements of the forearm, namely flexion and extension.
[5]. The radioulnar joints permit rotatory movements of the forearm called pronation and supination.
[6]. In a mid-flexed elbow, the palm faces upwards in supination and downwards in pronation. During the movement of pronation, the radius rotates around the ulna .
4 .The hand (Manus) .
The hand (Manus) includes:
a. The wrist or carpus, supported by 8 carpal bones arranged in two rows.
b. The hand proper or metacarpus, supported by 5 metacarpal bones.
c. Five digits (thumb and four fingers).
[1]. Each finger is supported by three phalanges, but the thumb has only 2 phalanges (there being 14 phalanges in all).
[2]. The carpal bones form the wrist joint with the radius, intercarpal joints with one another and carpometacarpal joints with the metacarpals.
[3]. The phalanges form metacarpophalangeal joints with the metacarpals and interphalangeal joints with one another.
[4]. Movements of the hand are permitted chiefly at the wrist joint.
[5]. The thumb moves at the first carpometacarpal joint; where an exclusive movement of opposition besides the other usual movements is permitted.
[6]. Each of the second to fifth digits moves at metacarpophalangeal, proximal and distal interphalangeal joints .
Clavicle.
[1]. The clavicle (Latin a small key) is a long bone. It supports the shoulder so that the arm can swing clearly away from the trunk.
[2]. The clavicle transmits the weight of the limb to the sternum.
[3]. The bone has a curved part called the shaft, and two ends, lateral and medial.
Features of Clavicle bone .
%20Superior%20aspect.jpg "General features of right clavicle (a) Superior aspect,") |
| General features of right clavicle: (a) Superior aspect, and (b) inferior aspect . |
Shaft of Clavicle bone .
[1]. The shaft is divisible into the lateral one-third and the medial two-thirds. The lateral one-third of the shaft is flattened from above downwards.
[2]. It has two borders—anterior and posterior. The anterior border is concave forwards. The posterior border is convex backwards.
[3]. This part of the bone has two surfaces—superior and inferior. The superior surface is subcutaneous and the inferior surface presents an elevation called the conoid (Greek cone) tubercle and a ridge called the trapezoid ridge.
[4]. The medial two-thirds of the shaft is rounded and is said to have four surfaces. The anterior surface is convex forwards. The posterior surface is smooth.
[5]. The superior surface is rough in its medial part. The inferior surface has a rough oval impression at the medial end.
[6]. The lateral half of this surface has a longitudinal subclavian groove. The nutrient foramen lies at the lateral end of the groove.
Lateral and Medial Ends of Clavicle .
[1]. The lateral or acromial (Greek peak of shoulder) end is flattened from above downwards.
[2]. It bears a facet that articulates with the acromion process of the scapula to form the acromioclavicular joint.
[3]. The medial or sternal end is quadrangular and articulates with the clavicular notch of the manubrium sterni to form the sternoclavicular joint.
[4]. The articular surface extends to the inferior aspect, for articulation with the first costal cartilage.
Soft Tissue & Muscular attachments .
%20Superior%20aspect,%20and%20(b)%20inferior%20aspect.jpg "Attachments of right clavicle (a) Superior aspect, and (b) inferior aspect") |
| Attachments of right clavicle: (a) Superior aspect, and (b) inferior aspect . |
[1]. At the lateral end, the margin of the articular surface for its acromioclavicular joint gives attachment to the joint capsule.
[2]. At the medial end, the margin of the articular surface for the sternum gives attachment to:
a. Fibrous capsule of sternoclavicular joint all around .
b. Articular disc posterosuperiorly.
c. Interclavicular ligament superiorly .
[3]. Lateral one-third of shaft
a. The anterior border gives origin to the deltoid muscle .
b. The posterior border provides insertion to the trapezius muscle.
c. The conoid tubercle and trapezoid ridge give attachment to the conoid and trapezoid parts of the coracoclavicular ligament .
[4]. Medial two-thirds of the shaft
a. Most of the anterior surface gives origin to the pectoralis major .
b. Half of the rough superior surface gives origin to the clavicular head of the sternocleidomastoid .
c. The oval impression on the inferior surface at the medial end gives attachment to the costoclavicular ligament .
d. The subclavian groove gives insertion to the subclavius muscle. The margins of the groove give attachment to the clavipectoral fascia.
e. The posterior surface close to medial end gives origin to sternohyoid muscle.
f. The subclavian vessels and divisions of trunks of brachial plexus pass towards the axilla lying between the inferior surface of the clavicle and upper surface of first rib. Subclavius muscle acts as a cushion. The nutrient foramen transmits a branch of the suprascapular artery .
Side Determination of Clavicle Bone .
The side to which a clavicle belongs can be determined from the following characters.
[1]. The lateral end is flat, and the medial end is large and quadrilateral.
[2]. The shaft is slightly curved, so that it is convex forwards in its medial two-thirds, and concave forwards in its lateral one-third.
[3]. The inferior surface is grooved longitudinally in its middle one-third.
Ossification of Clavicle Bone.
[1]. The clavicle is the first bone in the body to ossify . Except for its medial end, it ossifies in membrane. It ossifies from two primary centres and one secondary centre.
[2]. The two primary centres appear in the shaft between the fifth and sixth weeks of intrauterine life, and fuse about the 45th day.
[3]. The secondary centre for the medial end appears during 15–17 years, and fuses with the shaft during 21–22 years. Occasionally, there may be a secondary centre for the acromial end.
Scapula .
[1]. The scapula (Latin shoulder blade) is a thin bone placed on the posterolateral aspect of the thoracic cage.
[2]. The scapula has two surfaces, three borders, three angles and three processes .
Features of Scapula .
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| General features of right scapula . |
Surfaces of Scapula .
[1]. The costal surface or subscapular fossa is concave and is directed medially and forwards. It is marked by three longitudinal ridges.
[2]. Another thick ridge adjoins the lateral border. This part of the bone is almost rod-like.
[3]. It acts as a lever for the action of the serratus anterior in overhead abduction of the arm.
[4]. The dorsal surface gives attachment to the spine of the scapula which divides the surface into a smaller supraspinous fossa and a larger infraspinous fossa.
[5]. The two fossae are connected by the spinoglenoid notch, situated lateral to the root of the spine.
Borders of Scapula .
[1]. The superior border is shortest. Near the root of the coracoid process, it presents the suprascapular notch.
[2]. The lateral border is thick. At the upper end, it presents the infraglenoid tubercle.
[3]. The medial border is thin. It extends from the superior angle to the inferior angle.
Angles of Scapula .
[1]. The superior angle is covered by the trapezius.
[2]. The inferior angle is covered by the latissimus dorsi. It moves forwards round the chest when the arm is abducted.
[3]. The lateral or glenoid angle is broad and bears the glenoid cavity or fossa, which is directed forwards, laterally and slightly upwards . A supraglenoid tubercle is present above the glenoid cavity.
Processes of Scapula .
[1]. The spine or spinous process is a triangular plate of bone with three borders and two surfaces.
[2]. It divides the dorsal surface of the scapula into the supraspinous and infraspinous fossae.
[3]. Its posterior border is called the crest of the spine. The crest has upper and lower lips.
[4]. The acromion process has two borders, medial and lateral; two surfaces, superior and inferior; and a facet for the clavicle .
[5]. The coracoid (Greek like a crow’s beak) process is directed forwards and slightly laterally. It is bent and finger-like. It is an atavistic type of epiphysis.
Soft Tissue & Muscular attachments of Scapula .
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| Attachments of right scapula . |
[1]. The multipennate subscapularis muscle arises from the medial two-thirds of the subscapular fossa.
[2]. The supraspinatus arises from the medial two-thirds of the supraspinous fossa including the upper surface of the spine .
[3]. The infraspinatus arises from the medial two-thirds of the infraspinous fossa, including the lower surface of the spine .
[4]. The deltoid arises from the lower border of the crest of the spine and from the lateral border of the acromion . The acromial fibres are multipennate.
[5]. The trapezius is inserted into the upper border of the crest of the spine and into the medial border of the acromion process .
[6]. The serratus anterior is inserted along the medial border of the costal surface: One digitation from the superior angle to the root of spine, two digitations to the medial border and five digitations to the inferior angle .
[7 ]. The long head of the biceps brachii arises from the supraglenoid tubercle; and the short head from the lateral part of the tip of the coracoid process.
[8]. The coracobrachialis arises from the medial part of the tip of the coracoid process.
[9]. The pectoralis minor is inserted into the medial border and superior surface of the coracoid process. [10]. The long head of the triceps brachii arises from the infraglenoid tubercle.
[11]. The teres minor arises by two slips from the upper two-thirds of the rough strip on the dorsal surface along the lateral border . Circumflex scapular artery lies between the two slips.
[12]. The teres major arises from the lower one-third of the rough strip on the dorsal aspect of the lateral border . Latissimus dorsi arises from inferior angle.
[13]. The levator scapulae is inserted along the dorsal aspect of the medial border, from the superior angle up to the root of the spine .
[14]. The rhomboid minor is inserted into the medial border (dorsal aspect) opposite the root of the spine .
[15]. The rhomboid major is inserted into the medial border (dorsal aspect) between the root of the spine and the inferior angle.
[16]. The inferior belly of the omohyoid arises from the upper border near the suprascapular notch. [17]. The margin of the glenoid cavity gives attachment to the capsule of the shoulder joint and to the glenoidal labrum (Latin lip) .
[18]. The margin of the facet on the medial aspect of the acromion process gives attachment to the capsule of the acromioclavicular joint .
[19]. The coracoacromial ligament is attached:
(a) to the lateral border of the coracoid process, and
(b) to the medial side of the tip of the acromion process .
[20]. The coracohumeral ligament is attached to the root of the coracoid process .
[21]. The coracoclavicular ligament is attached to the coracoid process: The trapezoid part on the superior aspect, and the conoid part near the root .
[22]. The transverse ligament bridges across the suprascapular notch and converts it into a foramen which transmits the suprascapular nerve. The suprascapular vessels lie above the ligament .
[23]. The spinoglenoid ligament may bridge the spinoglenoid notch. The suprascapular vessels and nerve pass deep to it .
Side Determination of Scapula .
[1]. The lateral or glenoid (Greek socket) angle is large and bears the glenoid cavity.
[2]. The dorsal surface is convex and is divided by the triangular spine into the supraspinous and infraspinous fossae.
[3]. The costal surface is occupied by the concave subscapular fossa to fit on the convex chest wall .
[4]. The thickest lateral border runs from the glenoid cavity above to the inferior angle below.
Ossification of Scapula .
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| Ossification of scapula . |
[1]. The scapula ossifies from one primary centre and seven secondary centres.
[2]. The primary centre appears near the glenoid cavity during the eighth week of development.
[3]. The first secondary centre appears in the middle of the coracoid process during the first year and fuses by the 15th year.
[4]. The Subcoracoid centre appears in the root of the coracoid process during the 10th year and fuses by the 16th to 18th years .
[5]. The other centres, including two for the acromion process, one for the lower two-thirds of the margin of the glenoid cavity, one for the medial border and one for the inferior angle, appear at puberty and fuse by the 25th year.
[6]. The fact of practical importance is concerned with the acromion process. If the two centres appearing for acromion process fail to unite, it may be interpreted as a fracture on radiological examination. In such cases, a radiograph of the opposite acromion process will mostly reveal similar failure of union.
Humerus .
The humerus is the bone of the arm. It is the longest bone of the upper limb. It has an upper rounded end, a lower flattened end and a shaft .
Features of Humerus .
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| General features of right humerus . |
Upper End of Humerus .
[1]. The head is directed medially, backwards and upwards. It articulates with the glenoid cavity of the scapula to form the shoulder joint.
[2]. The head forms about one-third of a sphere and is much larger than the glenoid cavity.
[3]. The line separating the head from the rest of the upper end is called the anatomical neck.
[4]. The lesser tubercle (Latin lump) is an elevation on the anterior aspect of the upper end .
[5]. The greater tubercle is an elevation that forms the lateral part of the upper end. Its upper and posterior aspect is marked by three impressions—upper, middle and lower.
[6]. The intertubercular sulcus or bicipital groove separates the lesser tubercle medially from the anterior part of the greater tubercle.
[7]. The sulcus has medial and lateral lips that represent downward prolongations of the lesser and greater tubercles.
[8]. The narrow line separating the upper end of the humerus from the shaft is called the surgical neck . [9]. Morphological neck lies 0.5 cm below surgical neck. It shows the position of epiphyseal line .
Shaft of Humerus .
The shaft is rounded in the upper half and triangular in the lower half. It has three borders and three surfaces.
Borders of Humerus .
[1]. The upper one-third of the anterior border forms the lateral lip of the intertubercular sulcus. In its middle part, it forms the anterior margin of the deltoid tuberosity. The lower half of the anterior border is smooth and rounded.
[2]. The lateral border is prominent only at the lower end where it forms the lateral supracondylar ridge. In the upper part, it is barely traceable up to the posterior surface of the greater tubercle. In the middle part, it is interrupted by the radial or spiral groove .
[3]. The upper part of the medial border forms the medial lip of the intertubercular sulcus. About its middle, it presents a rough strip. It is continuous below with the medial supracondylar ridge.
Surfaces of Humerus .
[1]. The anterolateral surface lies between the anterior and lateral borders. The upper half of this surface is covered by the deltoid. A little above the middle, it is marked by a V-shaped deltoid (Greek triangular-shaped) tuberosity. Behind the deltoid tuberosity, the radial groove runs downwards and forwards across the surface.
[2]. The anteromedial surface lies between the anterior and medial borders. Its upper one-third is narrow and forms the floor of the intertubercular sulcus. A nutrient foramen is seen near the medial border below its middle part .
[3 ]. The posterior surface lies between the medial and lateral borders. Its upper part is marked by an oblique ridge. The middle one-third is crossed by the radial groove .
Lower end of Humerus .
[1]. The lower end of the humerus forms the condyle which is expanded from side-to-side and has articular and non-articular parts.
[2]. The articular part includes the following.
1. The capitulum (Latin little head) is a rounded projection which articulates with the head of the radius.
2. The trochlea (Greek pulley) is a pulley-shaped surface. It articulates with the trochlear notch of the ulna.
3.The medial edge of the trochlea projects down 6 mm more than the lateral edge—this results in the formation of the carrying angle .
[3]. The non-articular part includes the following.
1. The medial epicondyle is a prominent bony projection on the medial side of the lower end. It is subcutaneous and is easily felt on the medial side of the elbow .
2. The lateral epicondyle is smaller than the medial epicondyle. Its anterolateral part has a muscular impression.
3. The sharp lateral margin just above the lower end is called the lateral supracondylar ridge.
4. The medial supracondylar ridge is a similar ridge on the medial side.
5. The coronoid fossa is a depression just above the anterior aspect of the trochlea. It accommodates the coronoid process of the ulna when the elbow is flexed .
6. The radial fossa is a depression present just above the anterior aspect of the capitulum. It accommodates the head of the radius when the elbow is flexed.
7. The olecranon (Greek ulna head) fossa lies just above the posterior aspect of the trochlea. It accommodates the olecranon process of the ulna when the elbow is extended .
Soft Tissue & Muscular attachments of Humerus.
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| Attachments of right humerus . |
[1]. The multipennate subscapularis is inserted into the lesser tubercle .
[2]. The supraspinatus is inserted into the uppermost impression on the greater tubercle.
[3]. The infraspinatus is inserted into the middle impression on the greater tubercle .
[4]. The teres minor is inserted into the lower impression on the greater tubercle .
[5]. The pectoralis major is inserted into the lateral lip of the intertubercular sulcus. The insertion is bilaminar .
[6]. The latissimus dorsi is inserted into the floor of the intertubercular sulcus.
[7]. The teres major is inserted into the medial lip of the intertubercular sulcus.
[8]. The contents of the intertubercular sulcus are:
a. The tendon of the long head of the biceps brachii, and its synovial sheath.
b. The ascending branch of the anterior circumflex humeral artery.
[9]. The deltoid is inserted into the deltoid tuberosity .
[10]. The coracobrachialis is inserted into the rough area on the middle of the medial border.
[11]. The brachialis arises from the lower halves of the anteromedial and anterolateral surfaces of the shaft. Part of the area extends onto the posterior aspect .
[12]. The brachioradialis arises from the upper two-thirds of the lateral supracondylar ridge .
[13]. The extensor carpi radialis longus arises from the lower one-third of the lateral supracondylar ridge.
[14]. The pronator teres (humeral head) arises from the lower one-third of the medial supracondylar ridge.
[15]. The superficial flexor muscles of the forearm arise by a common origin from the anterior aspect of the medial epicondyle. This is called the common flexor origin.
[16]. The superficial extensor muscles of the forearm and supinator have a common origin from the lateral epicondyle. This is called the common extensor origin.
[17]. The anconeus (Greek elbow) arises from the posterior surface of the lateral epicondyle .
[18]. Lateral head of triceps brachii arises from oblique ridge on the upper part of posterior surface above the radial groove, while its medial head arises from posterior surface below the radial groove.
[19]. The capsular ligament of the shoulder joint is attached to the anatomical neck except on the medial side where the line of attachment dips down by about 2 cm to include a small area of the shaft within the joint cavity. The line is interrupted at the intertubercular sulcus to provide an aperture through which the tendon of the long head of the biceps brachii leaves the joint cavity .
[20]. The capsular ligament of the elbow joint is attached to the lower end along a line that reaches the upper limits of the radial and coronoid fossae anteriorly; and of the olecranon fossa posteriorly; so that these fossae lie within the joint cavity. Medially, the line of attachment passes between the medial epicondyle and the trochlea. On the lateral side, it passes between the lateral epicondyle and the capitulum .
[21]. Three nerves are directly related to the humerus and are, therefore, liable to injury—the axillary nerve at the surgical neck, the radial nerve at the radial groove, and the ulnar nerve behind the medial epicondyle .
Side Determination of Humerus .
[1]. The upper end is rounded to form the head. The lower end is expanded from side-to-side and flattened from before backwards.
[2]. The head is directed medially, upwards and backwards.
[3]. The lesser tubercle projects from the front of the upper end and is limited laterally by the intertubercular sulcus or bicipital groove.
Ossification of Humerus ,
[1]. The humerus ossifies from one primary centre and seven secondary centres.
[2]. The primary centre appears in the middle of the diaphysis during the 8th week of development.
[3]. The upper end ossifies from three secondary centres—one for the head (first year), one for the greater tubercle (second year), and one for the lesser tubercle (fifth year).
[4]. The three centres fuse together during the sixth year to form one compound epiphysis, which fuses with the shaft during the 20th year.
[5]. The epiphyseal line encircles the bone at the level of the lowest margin of the head. This is the growing end of the bone. (Remember that the nutrient foramen is always directed away from the growing end.)
[6]. The lower end ossifies from four centres which form two epiphyses. The centres include one for the capitulum and the lateral flange of the trochlea (first year), one for the medial flange of the trochlea (9th year) and one for the lateral epicondyle (12th year).
[7]. All three fuse during the 14th year to form another compound epiphysis, which fuses with the shaft at about 16 years.
[8]. The centre for the medial epicondyle appears during 4–6 years, forms a separate epiphysis, and fuses with the shaft during the 20th year.
Radius .
The radius is the lateral bone of the forearm, and is homologous with the tibia of the lower limb. It has an upper rounded end, a lower broad end with a styloid process and a shaft.
Features of Radius .
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| Features of anterior surfaces of radius and ulna . |
Upper end of Radius .
[1]. The head is disc-shaped and is covered with hyaline cartilage . It has a superior concave surface which articulates with the capitulum of the humerus at the elbow joint.
[2]. The circumference of the head is also articular. It fits into a socket formed by the radial notch of the ulna and the annular ligament, thus forming the superior radioulnar joint.
[3]. The neck is enclosed by the narrow lower margin of the annular ligament. The head and neck are free from capsular attachment and can rotate freely within the socket.
[4]. The radial tuberosity lies just below the medial part of the neck. It has a rough posterior part and a smooth anterior part.
Shaft of Radius .
It has three borders and three surfaces .
Borders of Radius .
[1]. The anterior border extends from the anterior margin of the radial tuberosity down close to the styloid process. It is oblique in the upper half of the shaft, and vertical in the lower half. The lowest part is sharp and crest-like. The oblique part is called the anterior oblique line .
[2]. The posterior border is the mirror image of the anterior border, but is clearly defined only in its middle one-third. The upper oblique part is known as the posterior oblique line .
[3]. The medial or interosseous border is the sharpest of the three borders. It extends from the radial tuberosity above to the posterior margin of the ulnar notch below. The interosseous membrane is attached to its lower three-fourths . In its lower part, it forms the posterior margin of an elongated triangular area .
Surfaces of Radius .
[1]. The anterior surface lies between the anterior and interosseous borders. A nutrient foramen opens in its upper part, and is directed upwards. The nutrient artery is a branch of the anterior interosseous artery.
[2]. The posterior surface lies between the posterior and interosseous borders.
[3]. The lateral surface lies between the anterior and posterior borders. It shows a roughened area in its middle part.
Lower end of Radius .
The lower end is the widest part of the bone. It has five surfaces.
[1]. The anterior surface is in the form of a thick prominent ridge. The radial artery is palpated against this surface.
[2]. The posterior surface presents four grooves for the extensor tendons. The dorsal tubercle of Lister lies lateral to an oblique groove .
[3]. The medial surface is occupied by the ulnar notch for the head of the ulna .
[4]. The lateral surface is prolonged downwards to form the styloid (Greek pillar) process .
[5]. The inferior surface bears a triangular area for the scaphoid bone, and a medial quadrangular area for the lunate bone. This surface takes part in forming the wrist joint .
Soft Tissue & Muscular attachments .
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| Attachments of right radius and ulna . |
[1]. The biceps (Latin two heads) brachii is inserted into the rough posterior part of the radial tuberosity. The anterior part of the radial tuberosity is covered by a bursa .
[2]. The supinator (Latin to bend back) is inserted into the upper part of the lateral surface.
[3]. The pronator teres is inserted into the middle of the lateral surface .
[4]. The brachioradialis is inserted into the lowest part of the lateral surface just above the styloid process .
[5]. The radial head of the flexor digitorum superficialis takes origin from the anterior oblique line and the upper part of anterior border .
[6]. The flexor pollicis (Latin thumb) longus takes origin from the upper two-thirds of the anterior surface .
[7]. The pronator quadratus is inserted into the lower part of the anterior surface and into the triangular area on the medial side of the lower end.
[8]. The radial artery is palpated for ‘radial pulse’, as it lies on the pronator quadratus medial to the sharp anterior border of radius, lateral to the tendon of flexor carpi radialis.
[9]. The abductor pollicis longus and the extensor pollicis brevis arise from the posterior surface .
[10]. The quadrate ligament is attached to the medial part of the neck.
[11]. The oblique cord is attached on the medial side just below the radial tuberosity .
[12]. The articular capsule of the wrist joint is attached to the anterior and posterior margins of the inferior articular surface.
[13]. The articular disc of the inferior radioulnar joint is attached to the lower border of the ulnar notch.
[14]. The extensor retinaculum is attached to the lower part of the sharp anterior border .
[15]. The interosseous membrane is attached to the lower three-fourths of the interosseous border.
[16]. The first groove between sharp crest-like lowest part of anterior border and styloid process gives passage to abductor pollicis longus and extensor pollicis brevis .
[17]. The second groove between styloid process and dorsal tubercle gives way to extensor carpi radialis longus and extensor carpi radialis brevis tendons.
[18]. The third oblique groove medial to dorsal tubercle gives passage to extensor pollicis longus tendon.
[19]. The fourth groove on the medial aspect gives passage to tendons of extensor digitorum, extensor indicis, posterior interosseous nerve and anterior interosseous artery.
[20]. In addition, at the junction of lower ends of radius and ulna, the fifth groove gives passage to the tendon of extensor digiti minimi.
[21]. Lastly in relation to ulna, between its head and styloid process is the sixth groove, traversed by the tendon of extensor carpi ulnaris .
[22]. These are six compartments/grooves under extensor retinaculum of wrist, four are in relation to radius, 5th at the junction of radius and ulna and 6th on the ulna itself between its head and styloid process .
Side Determination of Radius .
[1]. Upper end is having disc-shaped head, a narrow neck while lower end is expanded with a styloid process. Close to neck, it presents a radial tuberosity.
[2]. At the lower end, the anterior surface is in the form of thick prominent ridge. While the posterior surface presents four grooves for the extensor tendons.
[3]. Lower end presents a tubercle on the posterior surface called as dorsal tubercle of Lister.
[4]. The sharpest border of the shaft is the medial border.
Ossification of Radius .
[1]. The shaft of radius ossifies from a primary centre which appears during the 8th week of development.
[2]. The lower end ossifies from a secondary centre which appears during the first year and fuses with shaft at 20th year; it is the growing end of the bone.
[3]. The upper end (head) ossifies from a secondary centre which appears during the 4th year and fuses with shaft at 18th year .
Ulna .
The ulna is the medial bone of the forearm, and is homologous with the fibula of the lower limb. It has an upper end with two processes, a shaft and a narrow rounded lower end.
Features of Ulna .
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| Features of anterior surfaces of radius and ulna . |
Upper end of Ulna .
The upper end presents the olecranon and coronoid processes, and the trochlear and radial notches .
1. The olecranon process projects upwards from the shaft. It has superior, anterior, posterior, medial and lateral surfaces.
[1]. The anterior surface is articular, it forms the upper part of the trochlear notch .
[2]. The posterior surface forms a triangular subcutaneous area which is separated from the skin by a bursa. Inferiorly, it is continuous with the posterior border of the shaft of the ulna . Its upper part forms the point of the elbow.
[3]. The medial surface is continuous inferiorly with the medial surface of the shaft.
[4]. The lateral surface is smooth, continues as posterior surface of shaft.
[5]. The superior surface in its posterior part shows a roughened area.
2. The coronoid (Greek like crow’s beak) process projects forwards from the shaft just below the olecranon process and has four surfaces, namely superior, anterior, medial and lateral.
[1]. The superior surface forms the lower part of the trochlear notch.
[2]. The anterior surface is triangular and rough. Its lower corner forms the ulnar tuberosity.
[3]. The upper part of its lateral surface is marked by the radial notch for the head of the radius.
[4]. The annular ligament is attached to the anterior and posterior margins of the notch.
[5]. The lower part of the lateral surface forms a depressed area to accommodate the radial tuberosity. It is limited behind by a ridge called the supinator crest .
[6]. Medial surface is continuous with medial surface of the shaft.
3. The trochlear notch forms an articular surface that articulates with the trochlea of the humerus to form the elbow joint.
4. The radial notch articulates with the head of the radius to form the superior radioulnar joint .
Shaft of Ulna .
The shaft has three borders and three surfaces .
Borders of Ulna .
[1]. The interosseous or lateral border is the sharpest in its middle two-fourths. Inferiorly, it can be traced to the lateral side of the head. Superiorly, it is continuous with the supinator crest.
[2]. The anterior border is thick and rounded. It begins above on the medial side of the ulnar tuberosity, passes backwards in its lower one-third, and terminates at the medial side of the styloid process.
[3]. The posterior border is subcutaneous. It begins, above, at the apex of the triangular subcutaneous area at the back of the olecranon process, and terminates at the base of the styloid process .
Surfaces of Ulna .
[1]. The anterior surface lies between the anterior and interosseous borders. A nutrient foramen is seen on the upper part of this surface. It is directed upwards. The nutrient artery is derived from the anterior interosseous artery .
[2]. The medial surface lies between the anterior and posterior borders .
[3]. The posterior surface lies between the posterior and interosseous borders. It is subdivided into three areas by two lines. An oblique line divides it into upper and lower parts. The lower part is further divided by a vertical line into a medial and a lateral area.
Lower End of Ulna .
[1]. The lower end is made up of the head and the styloid process.
[2]. The head articulates with the ulnar notch of the radius to form the inferior radioulnar joint. It is separated from the wrist joint by the articular disc .
[3]. Ulnar artery and nerve lie on the anterior aspect of head of ulna.
[4]. The styloid process projects downwards from posteromedial side of lower end of the ulna.
[5]. Posteriorly, between the head and the styloid process, there is a groove for the tendon of the extensor carpi ulnaris .
Soft Tissue & Muscular attachments.
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| Attachments of right radius and ulna . |
[1]. The triceps brachii is inserted into the rough posterior part of the superior surface of the olecranon process . The anterior part of the surface is covered by a bursa.
[2]. The brachialis is inserted into the anterior surface of the coronoid process including the ulnar tuberosity .
[3]. The supinator arises from the supinator crest and from the triangular area in front of the crest .
[4]. The ulnar head of the flexor digitorum superficialis arises from a tubercle at the upper end of the medial margin of the coronoid process.
[5]. The ulnar head of the pronator teres arises from the medial margin of the coronoid process.
[6]. The flexor digitorum profundus (Latin deep) arises from:
a. The upper three-fourths of the anterior and medial surfaces of the shaft.
b. The medial surfaces of the coronoid and olecranon processes.
c. The posterior border of the shaft through an aponeurosis which also gives origin to the flexor carpi ulnaris and the extensor carpi ulnaris .
[7]. The pronator quadratus takes origin from the oblique ridge on the lower part of the anterior surface .
[8]. The flexor carpi ulnaris (ulnar head) arises from the medial side of the olecranon process and from the posterior border.
[9]. The extensor carpi ulnaris arises from the posterior border .
[10]. The anconeus is inserted into the lateral aspect of the olecranon process and the upper one-fourth of the posterior surface of the shaft.
[11]. The lateral part of the posterior surface gives origin from above downwards to the abductor pollicis longus, the extensor pollicis longus and the extensor indicis.
[12]. The interosseous membrane is attached to the interosseous border.
[13]. The oblique cord is attached to the ulnar tuberosity.
[14]. The capsular ligament of the elbow joint is attached to the margins of the trochlear notch, i.e. to the coronoid and olecranon processes .
[15]. The annular ligament of the superior radioulnar joint is attached to the two margins of radial notch of ulna.
[16]. The ulnar collateral ligament of the wrist is attached to the styloid process.
[17]. The articular disc of the inferior radioulnar joint is attached by its apex to a small rough area just lateral to the styloid process .
Side Determination
[1]. The upper end is hook-like, with its concavity directed forwards.
[2]. The lateral border of the shaft is sharp and crest-like.
[3]. Pointed styloid process lies posteromedial to the rounded head of ulna at its lower end.
Ossification of Ulna .
[1]. The shaft and most of the upper end of ulna ossify from a primary centre which appears during the 8th week of development.
[2]. The superior part of the olecranon process ossifies from a secondary centre which appears during the 10th year. It forms a scale-like epiphysis which joins the rest of the bone by 16th year.
[3]. The lower end ossifies from a secondary centre which appears during the 5th year, and joins with the shaft by 18th year. This is the growing end of the bone .
Carpal .
The carpus is (Greek Karpos, wrist) made up of 8 carpal bones, which are arranged in two rows .
[1]. The proximal row contains (from lateral to medial side):
a. The scaphoid (Greek boat, wrist),
b. The lunate (Latin moon-shaped),
c. The triquetral (Latin three-cornered), and
d. The pisiform (Greek pea)
[2]. The distal row contains in the same order:
a. The trapezium (Greek four-sided geometric figure),
b. The trapezoid (Greek baby’s shoe),
c. The capitate (Latin head), and
d. The hamate (Latin hook).
Identification of Carpal .
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| Skeleton of the right hand: Palmar aspect . |
[1]. The scaphoid is boat-shaped and has a tubercle on its lateral side.
[2]. The lunate is half-moon-shaped or crescentic.
[3]. The triquetral is pyramidal in shape and has an isolated oval facet on the distal part of the palmar surface.
[4]. The pisiform is pea-shaped and has only one oval facet on the proximal part of its dorsal surface.
[5]. The trapezium is quadrangular in shape, and has a crest and a groove anteriorly. It has a sellar (concavo-convex) articular surface distally.
[6 ]. The trapezoid resembles the shoe of a baby.
[7]. The capitate is the largest carpal bone, with a rounded head.
[8]. The hamate is wedge-shaped with a hook near its base.
Specific Features of Carpal .
1. The scaphoid:
The tubercle is directed laterally, forward and downwards.
2. The lunate:
i. A small semilunar articular surface for the scaphoid is on the lateral side.
ii. A quadrilateral articular surface for the triquetral is on the medial side.
3. The triquetral:
i. The oval facet for the pisiform lies on the distal part of the palmar surface.
ii. The medial and dorsal surfaces are continuous and non-articular.
4. The pisiform:
i. The oval facet for the triquetral lies on the proximal part of the dorsal surface.
ii. The lateral surface is grooved by the ulnar nerve.
5. The trapezium:
i. The palmar surface has a vertical groove for the tendon of the flexor carpi radialis.
ii. The groove is limited laterally by the crest of the trapezium.
iii. The distal surface bears a sellar concavo-convex articular surface for the base of the first metacarpal bone.
6. The trapezoid:
i. The distal articular surface is bigger than the proximal.
ii. The palmar non-articular surface is prolonged laterally.
7. The capitate:
The dorsomedial angle is the distal-most projection from the body of the capitate.
It bears a small facet for the 4th metacarpal bone.
8. The hamate:
The hook projects from the distal part of the palmar surface, and is directed laterally.
Soft Tissue & Muscular attachments .
There are four bony pillars at the four corners of the carpus. All attachments are to these four pillars .
[1]. The tubercle of the scaphoid:
i. The flexor retinaculum,
ii. A few fibres of the abductor pollicis brevis.
[2]. The pisiform gives:
i. Insertion to be Flexor carpi ulnaris (FCU). Pisiform is a sesamoid bone in tendon of FCU.
ii. Flexor retinaculum and its superficial slip ,
iii. Abductor digiti minimi ,
iv. Extensor retinaculum .
[3]. The trapezium:
i. The crest gives origin to the abductor pollicis brevis, flexor pollicis brevis and opponens pollicis. These constitute muscles of thenar eminence .
ii. The edges of the groove give attachment to the two layers of the flexor retinaculum.
iii. The lateral surface gives attachment to the lateral ligament of the wrist joint.
iv. The groove lodges the tendon of the flexor carpi radialis.
[4]. The hamate:
i. The tip of the hook gives attachment to the flexor retinaculum .
ii. The medial side of the hook gives attachment to the flexor digiti minimi and the opponens digiti minimi.
Articulations of Carpal .
[1]. The scaphoid: Radius, lunate, trapezium, trapezoid capitate .
[2]. The lunate: Radius, scaphoid, capitate, hamate and triquetral.
[3]. The triquetral: Pisiform, lunate, hamate and articular disc of the inferior radioulnar joint.
[4]. The pisiform articulates only with the triquetral.
[5]. The trapezium: Scaphoid, 1st and 2nd metacarpals and trapezoid.
[6]. The trapezoid: Scaphoid, trapezium, 2nd metacarpal and capitate.
[7]. The capitate: Scaphoid, lunate, hamate, 2nd, 3rd and 4th metacarpals and trapezoid.
[8]. The hamate: Lunate, triquetral, capitate, and 4th and 5th metacarpals.
Side Determination of Carpal .
[1]. The proximal row is convex proximally, and concave distally.
[2]. The distal row is convex proximally and flat distally.
[3]. Each bone has 6 surfaces.
a. The palmar and dorsal surfaces are non-articular, except for the triquetral and pisiform.
b. The lateral surfaces of the two lateral bones (scaphoid and trapezium) are non-articular.
c. The medial surfaces of the three medial bones (triquetral, pisiform and hamate) are nonarticular.
[4]. The dorsal non-articular surface is always larger than the palmar non-articular surface, except for the lunate, in which the palmar surface is larger than the dorsal.
Metacarpal .
[1]. The metacarpal bones are 5 miniature long bones, which are numbered from lateral to the medial side .
[2]. Each bone has a head placed distally, a shaft and a base at the proximal end.
a. The head is round. It has an articular surface which extends more antero-posteriorly than laterally. It extends more on the palmar surface than on the dorsal surface. The heads of the metacarpal bones form the knuckles during flexion.
b. The shaft is concave on the palmar surface. Its dorsal surface bears a flat triangular area in its distal part.
c. The base is irregularly expanded .
Characteristics of Individual Metacarpal Bones.
1st Metacarpal .
[1]. It is the shortest and stoutest of all metacarpal bones .
[2]. The base is occupied by a concavo-convex articular surface for the trapezium.
[3]. The dorsal surface of the shaft is uniformly convex .
[4]. The head is less convex and broader from side to side than the heads of other metacarpals. The ulnar and radial corners of the palmar surface show impressions for sesamoid bones.
[5]. The first metacarpal bone (lying on a more anterior plane) is rotated medially through 90° relative to the other metacarpals. As a result of this rotation, the movements of the thumb take place at right angles to those of other digits.
[6]. It does not articulate with any other metacarpal bone.
2nd Metacarpal .
The base is grooved from before backwards. The medial edge of the groove is larger .
3rd Metacarpal .
The base has a styloid process projecting up from the dorsolateral corner .
4th Metacarpal .
The base has two small oval facets on its lateral side for the third metacarpal and on its medial side it has a single elongated facet for the 5th metacarpal .
5th Metacarpal .
The base has an elongated articular strip on its lateral side for the 4th metacarpal. The medial side of the base is non-articular and bears a tubercle.
Soft Tissue & Muscular attachments .
The main attachments from shaft of metacarpals are of palmar and dorsal interossei muscles. Palmar interossei arise from one bone each except the 3rd metacarpal . Dorsal interossei arise from adjacent sides of two metacarpals .
1st Metacarpal .
a. The opponens pollicis is inserted on the radial border and the anterolateral surface of the shaft .
b. The abductor pollicis longus is inserted on the lateral side of the base.
c. The first palmar interosseous muscle arises from the ulnar side of the base.
2nd Metacarpal .
a. The flexor carpi radialis is inserted on a tubercle on the palmar surface of the base .
b. The extensor carpi radialis longus is inserted on the dorsal surface of the base .
c. The oblique head of the adductor pollicis arises from the palmar surface of the base.
3rd Metacarpal .
a. A slip from the flexor carpi radialis is inserted on the palmar surface of the base.
b. The extensor carpi radialis brevis is inserted on the dorsal surface of the base, immediately beyond the styloid process.
c. The oblique head of the adductor pollicis arises from the palmar surface of the base .
d. The transverse head of the adductor pollicis arises from the distal two-thirds of the palmar surface of the shaft 4th Only the interossei arise from it .
5th Metacarpal .
a. The extensor carpi ulnaris is inserted on the tubercle at the base.
b. The opponens digiti minimi is inserted on the medial surface of the shaft .
Articulations at the Bases .
[1]. 1st Metacarpal :-With the trapezium forms saddle-shaped joint.
[2]. 2nd Metacarpal :- With the trapezium, the trapezoid, the capitate and the 3rd metacarpal .
[3]. 3rd Metacarpal :- With the capitate and the 2nd and 4th metacarpals.
[4]. 4th metacarpal :- With the capitate, the hamate and the 3rd and 5th metacarpals.
[5]. 5th Metacarpal :- With the hamate and the 4th metacarpal.
Ossification of Metacarpal .
[1]. The shafts ossify from one primary centre each, which appears during the 9th week of development.
[2]. A secondary centre for the head appears in the 2nd–5th metacarpals and for the base in the 1st metacarpal.
[3]. It appears during the 2nd–3rd year and fuses with the shaft at about 16–18 years.
Phalanges .
There are 14 phalanges in each hand, three for each finger and two for the thumb. Each phalanx has a base, a shaft and a head.
Base of The Phalanx .
In the proximal phalanx, the base is marked by a concave oval facet for articulation with the head of the metacarpal bone. In the middle phalanx, or a distal phalanx, it is marked by two small concave facets separated by a smooth ridge.
Shaft of The Phalanx .
The shaft tapers towards the head. The dorsal surface is convex from side-to-side. The palmar surface is flattened from side-to-side, but is gently concave in its long axis.
Head of The Phalanx .
In the proximal and middle phalanges, the head has a pulley-shaped articular surface. In the distal phalanges, the head is non-articular, and is marked anteriorly by a rough horseshoe-shaped tuberosity which supports the sensitive pulp of the finger/tip.
Soft Tissue & Muscular attachments.
[1]. Base of the distal phalanx
a. The flexor digitorum profundus is inserted on the palmar surface .
b. Two-side slips of digital expansion fuse to be inserted on the dorsal surface. These also extend the insertion of lumbrical and interossei muscles .
[2]. The middle phalanx
a. The two slips of flexor digitorum superficialis are inserted on each side of the shaft .
b. The fibrous flexor sheath is also attached to the side of the shaft.
c. A major part of the extensor digitorum is inserted on the dorsal surface of the base through dorsal digital expansion .
[3]. The proximal phalanx
a. The fibrous flexor sheath is attached to the sides of the shaft.
b. On each side of the base, parts of the lumbricals and interossei are inserted.
[4]. In the thumb, the base of the proximal phalanx provides attachments to the following structures .
a. The abductor pollicis brevis and flexor pollicis brevis are inserted on the lateral side.
b. The adductor pollicis and the first palmar interosseous are inserted on the medial side.
c. The extensor pollicis brevis is inserted on the dorsal surface .
[5]. In the little finger, the medial side of the base of the proximal phalanx provides insertion to the abductor digiti minimi and the flexor digiti minimi .
Ossification of Phalanges .
[1]. The shaft of each phalanx ossifies from a primary centre which appears during the 8th week of development in the distal phalanx, 10th week in the proximal phalanx and 12th week in the middle phalanx.
[2]. The secondary centre appears for the base during 2–4 years and fuses with the shaft during 15–18 years .
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