CAPITULO 3. LA PROBABILIDAD EN LAS PRUEBAS DE SELECTIVIDAD DE MATEMÁTICAS APLICADAS
3.2. METODOLOGÍA
providing pincer-like grip between the thumb and index finger.
Hypothenar Muscles (Fig. 11.12) They are also three in number, viz.
1. Abductor digiti minimi.
2. Flexor digiti minimi.
3. Opponens digiti minimi.
Some authorities also consider palmaris brevis (see page 139) as one of the hypothenar muscles.
Relationship
1. Abductor digiti minimi lies medially.
2. Flexor digiti minimi lies laterally.
3. Opponens digiti minimi lies deep to the above two muscles.
Features
1. They form hypothenar eminence of the palm of the hand.
2. All of them are supplied by the deep branch of ulnar nerve. The origin, insertion, and actions of the thenar and hypothenar muscles are presented in Table 11.1.
N.B.
• The flexor pollicis brevis has dual nerve supply: superficial head by the median nerve and deep head by the deep branch of the ulnar nerve.
• Tendons of insertion of the flexor digiti minimi along with the abductor digiti minimi on the medial side of the base of first phalanx contain a sesamoid bone.
Adductor Pollicis Muscle (Fig. 11.13)
This fan-shaped muscle is located deep in the palm in contact with metacarpal and interossei. It consists of two heads: (a) oblique and (b) transverse.
Origin
1. Oblique head arises from anterior aspects of capitate bone and bases of second and third metacarpal bones—
forming a crescentic shape.
2. Transverse head arises from ridge on distal two-third of the anterior surface of the shaft of the third metacarpal.
Insertion
Into the medial side of the base of proximal phalanx of the thumb.
Nerve supply
Deep branch of the ulnar nerve (C8, TI).
Actions
Adduction of the thumb to provide power to the grip.
N.B.
• The tendons of insertion of adductor pollicis on the medial side of the base of proximal phalanx of the thumb contain a sesamoid bone.
• The deep palmar arch and deep branch of ulnar nerve pass between the two heads of adductor pollicis.
Clinical testing (Foment’s sign)
Give the patient a thin book and ask him to grasp it firmly between the thumbs and index fingers of both hands. If the muscle is healthy and acting normally, the thumbs will be straight. But if the muscle is paralyzed and not acting, the thumbs are flexed at IP joints (Fig. 13.4). This occurs because when adductors are not acting, flexor pollicis compensates for it.
Lumbrical Muscles (Fig. 11.14)
There are four lumbrical muscles and numbered first, second, third, and fourth from lateral to medial side. They are small slender muscles one for each digit. They are named lumbricals because of their elongated worm-like shape (L. lumbrical ⫽ earthworm).
Origin
1. Lumbricals 1 and 2: From lateral side of lateral two tendons of the flexor digitorum profundus.
2. Lumbricals 3 and 4: From adjacent sides of medial three tendons of the flexor digitorum profundus.
Insertion
The tendons cross the radial side of metacarpophalangeal (MP) joints to be inserted into the lateral side of dorsal digital expansion of the corresponding digit from second to fifth.
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Textbook of Anatomy: Upper Limb and Thorax
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Table 11.1 Origin, insertion, and actions of the thenar and hypothenar muscles
Muscles Origin Insertion Action
Thenar muscles Abductor pollicis brevis • Tubercle of scaphoid
• Crest of trapezium
• Flexor retinaculum
Lateral side of base of the proximal phalanx of thumb
Abduction of thumb
Flexor pollicis brevis • Superficial head from the distal border of the flexor retinaculum
• Deep head from trapezoid and capitate bones
Lateral side of the base of the proximal phalanx of thumb
Flexion of thumb
Opponens pollicis • Flexor retinaculum crest of trapezium
Lateral border and adjoining lateral half of the palmar surface of the first metacarpal bone
• Opposition of thumb
• Deepens the hollow of palm
Hypothenar muscles Abductor digiti minimi • Pisiform bone
• Tendon of flexor carpi ulnaris
Ulnar side of the base of the proximal phalanx of little finger
Abduction of little finger
Flexor digiti minimi • Flexor retinaculum
• Hook of hamate
Ulnar side of base of the proximal phalanx of little finger along with tendon of abductor digiti minimi
Flexion of little finger
Opponens digiti minimi • Flexor retinaculum
• Hook of hamate
Medial surface of the shaft of 5th metacarpal bone
• Opposition of the tip of little finger with the tip of thumb
• Deepens the hollow of palm
Oblique head
Transverse head
Sesamoid bone
Origin
1. Oblique head from capitate and bases of 2nd and 3rd metacarpals
2. Transverse head from shaft of 3rd metacarpal Insertion
Medial side of base of proximal phalanx Adductor
pollicis
Fig. 11.13 Origin and insertion of the adductor pollicis muscles.
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Hand 149
1. Superficial palmar branch of the radial artery (most common).
2. Radialis indicis artery.
3. Princeps pollicis artery.
Branches
1. Three common palmar digital arteries go to the interdigital clefts between the fingers and each divides into two proper digital arteries, which supply their adjacent sides. In the interdigital clefts, they are joined by the palmar metacarpal arteries.
2. One proper digital artery runs along the medial side of the little finger which it supplies.
3. Cutaneous branches to the palm, which supply the skin and superficial fascia of the palm.
Relations
Superficial: Palmar aponeurosis.
Deep: 1. Long flexor tendons of FDS and FDP.
2. Lumbricals.
3. Digital branches of the median and ulnar nerves.
Surface Anatomy
The superficial palmar arch lies across the centre of the palm at the level of the distal border of the fully extended thumb.
Deep Palmar Arch (Fig. 11.17)
The deep palmar arch is the direct continuation of radial artery. The arch is completed medially (at the base of the fifth metacarpal) by anastomosing with the deep palmar branch of the ulnar artery.
The radial artery enters the palm from dorsal aspect of the hand by passing between the two heads of first dorsal interosseous muscle. Immediately after entering the palm, the radial artery gives off two branches: arteria radialis indicis and arteria princeps pollicis. In the palm, it passes between the two heads of adductor pollicis.
Branches
1. Three palmar metacarpal arteries, which join the common palmar digital arteries, the branches of the superficial palmar arch.
2. Three perforating arteries, which pass through the 2nd, 3rd, and 4th interosseous spaces to anastomose with dorsal metacarpal arteries.
3. Recurrent branch/branches run proximally in front of carpus to end in the palmar carpal arch.
Relations Deep:
(a) Proximal parts of shafts of the metacarpals.
(b) Interosseous muscles.
Superficial:
(a) Long flexor tendons of the fingers.
(b) Lumbricals.
N.B. The deep branch of the ulnar nerve lies in the concavity