The Hand Anatomy Bones Blood Supply Muscles Notes

Palm of the hand

Question 1. Describe the palmar aponeurosis briefly and discuss its applied anatomy.
Answer.

The palmar aponeurosis is the thick central part of the deep fascia of the palm. It is triangular in shape with its apex facing proximally and base facing distally. It overlies the superficial palmar arch, long flexor tendons, terminal part of the median nerve and superficial branch of the ulnar nerve.

Attachments

Apex:

It is attached to the flexor retinaculum and provides insertion to the tendon of palmaris longus.

Base:

Just proximal to the heads of metacarpals, divides into four longitudinal slips – one for each medial four digits. Each slip has a superficial and a deep set of fibres. The superficial fibres are attached to the skin of fingers at their roots. The deep fibres blend with the fibrous flexor sheaths and are also connected to deep transverse ligaments of palm.

Relations

• Between the slips (in the web spaces of fingers), the digital nerve and vessels emerge to pass distally.
• From the medial and lateral borders of palmar aponeurosis, medial and lateral intermuscular septa extend inwards and get attached to 5th and 1st metacarpals, respectively. These septa divide the palm into compartments.

Functions

• Protects the underlying tendons, nerves and vessels
• Helps to improve the grip of hand by fixing the skin of the palm

Applied anatomy

The progressive contraction of medial part of palmar aponeurosis produces a deformity called Dupuytren’s contracture. The little and ring fingers are usually involved. The proximal and middle phalanges become flexed and cannot be straightened. The distal phalanges, however, remain unaffected or may become hyperextended.

Question 2. Enumerate the intrinsic muscles of the hand.
Answer.

These are given next.

Subcutaneous muscle

• Palmaris brevis

Muscles of thenar eminence

• Abductor pollicis brevis
• Flexor pollicis brevis
• Opponens pollicis

Adductor of thumb

• Adductor pollicis

Muscles of hypothenar eminence

• Abductor digiti minimi
• Flexor digiti minimi
• Opponens digiti minimi

Lumbricals

• Four in number
• Numbered from lateral to medial side (1, 2, 3 and 4)

Read And Learn More: Selective Anatomy Notes And Question And Answers

Interossei

• Palmar interossei (four in number)
• Dorsal interossei (four in number)

Question 3. Write a short note on adductor pollicis.
Answer.

It is a fan-shaped deeply placed muscle in the lateral part of hand.

Origin

• Oblique head: From capitate, and bases of 2nd and 3rd metacarpals.
• Transverse head: From linear ridge on the middle of the palmar surface of 3rd metacarpal.

Insertion

Two heads converge and meet to form a tendon, which is inserted into the medial side of base of proximal phalanx of the thumb and often contains a sesamoid bone.

• Nerve supply: By deep branch of ulnar nerve (C8, T1).
• Action: Adduction of thumb towards other fingers as in power grip.

Question 4. Give the origin, insertion, nerve supply and actions of lumbrical muscles.
Answer.

The origin and insertion of lumbrical muscles.

Origin and Insertion of Lumbrical Muscles

Nerve supply

First and 2nd lumbricals are supplied by median nerve, whereas 3rd and 4th lumbricals are supplied by deep branch of ulnar nerve.

Actions

Flexion of metacarpophalangeal (MP) joints and extension of proximal and distal interphalangeal (PIP + DIP) joints.

Question 5. What are interossei muscles? Describe their origin, insertion, nerve supply and actions in brief.
Answer.

The interossei are small muscles present between the metacarpals. They are divided into two groups: palmar interossei and dorsal interossei; each group consists of four muscles.

Origin and insertion

The origin and insertion of interossei muscles.

Origin and Insertion of Interossei Muscles

Nerve supply

All the interossei are supplied by the deep branch of the ulnar nerve.

Actions

Palmar interossei adduct the digits while dorsal interossei abduct the digits.

Mnemonic: PAD and DAB

(D, dorsal; P, palmar; AD, adductor; AB, abductor)

Question 6. Write a short note on dorsal digital expansion.
Answer.

Each tendon of extensor digitorum flattens to form an aponeurotic expansion over the dorsal aspect of MCP joint, which covers the dorsum and sides of the proximal phalanx like a hood. At the PIP joint, the aponeurotic expansion divides into three slips: a central slip and two collateral slips. The central slip is attached to the base of the middle phalanx and the two lateral slips join each other to form a single slip which is attached to the dorsal aspect of the base of distal phalanx.

The margins of the extensor expansion are reinforced by intrinsic muscles of the hand – the interossei and lumbrical muscles.

Functional significance of the dorsal digital expansion

The intrinsic muscles arising from the palmar aspect of the hand and inserting along the dorsal aspect of the fingers can have unique function in that they flex the metacarpophalangeal (MP) joints, and extend the proximal and distal interphalangeal (i.e. PIP and DIP) joints.

Question 7. What are fascial spaces of the hand?
Answer.

A number of fascial spaces in the region of hand are formed due to arrangement of fasciae and fascial septa. These are as follows.

Palmar spaces

• Midpalmar space
• Thenar space
• Pulp space

Dorsal spaces

• Dorsal subcutaneous space
• Dorsal subaponeurotic space

Parona’s space

• Fascial space in front of distal forearm

Question 8. Write a short note on midpalmar space.
Answer.

It is a triangular space located under the inner half of the hollow of the palm.

Boundaries

Anterior:

From superficial to deep, the structures forming anterior boundary are palmar aponeurosis, superficial palmar arch, ulnar bursa enclosing flexor tendons of middle, ring and little fingers, and 2nd, 3rd and 4th (medial three) lumbricals.

Posterior:

Fascia covering the interossei of the 3rd and 4th spaces.

Lateral:

Oblique intermediate palmar septum extending from palmar aponeurosis to 3rd metacarpal bone, which separates it from thenar space.

Medial:

Medial palmar septum extending from palmar aponeurosis to 5th metacarpal bone, which separates it from hypothenar muscles.

Proximally:

It is continuous with the Parona’s space situated deep to the flexor tendons and in front of pronator quadratus.

Distally:

It continues as extensions around lumbrical canals to web spaces of medial three fingers.

Applied anatomy

This space is primarily infected by puncture wounds. It may be involved secondarily due to infection spreading from digital synovial sheaths of flexor tendons. From here, the infection may spread to Parona’s space. If this space is infected, then there is tenderness in the palm over the area of midpalmar space and painful flexion of little, ring and middle fingers. The pus from midpalmar space can be drained by an incision into 3rd or 4th web space, depending on where the pus points.

Question 9. Write a short note on thenar space.
Answer.

It is a triangular space located under the outer half of the hollow of palm.

Boundaries

Anterior:

Flexor tendons of index finger, 1st lumbrical and palmar aponeurosis.

Posterior:

Fascia covering transverse head of adductor pollicis and 1st dorsal interosseous muscle.

Medial:

Oblique intermediate palmar septum, which separates it from midpalmar space.

Lateral:

Lateral palmar septum extending from palmar aponeurosis to 1st metacarpal.

Proximally:

It is continuous with Parona’s space.

Distally:

Extends around the 1st lumbrical (1st lumbrical canal) to 1st web space.

Applied anatomy

Primary infection to thenar space occurs through puncture wounds. Secondary infection may be due to infection spreading from digital synovial sheath of index finger. This space can be drained by an incision in the 1st web space or where the pus points.

Question 10. Write a short note on pulp space.
Answer.

It is a closed subcutaneous space in front of distal phalanx of each digit.

Boundaries

In front and sides:

Skin.

Behind:

Distal two-third of distal phalanx.

Features

The space is divided into many compartments by fibrous septa extending between the skin and the bone. The proximal one-fifth of the distal phalanx is outside the pulp space and corresponds to the epiphysis of the bone, which receives its blood supply from epiphyseal artery – a branch of digital artery that does not pass through pulp space.

The distal four-fifth of distal phalanx lies within the space and receives its blood supply from digital artery, which runs through the space.

Applied anatomy

The infection of the pulp space is called whitlow. It can produce necrosis of the distal four-fifth of the phalanx due to occlusion of digital artery. The complete regeneration is possible because the proximal epiphyseal portion of phalanx remains unaffected.

Question 11. Write a short note on Parona’s space.
Answer.

It is a rectangular fascial space located in front of distal forearm.

Boundaries

Proximally:

It extends up to the origin of flexor digitorum superficialis from anterior oblique line of radius.

Distally:

It is continuous with fascial spaces in palm.

Superficially:

Long flexor tendons.

Deep:

Pronator quadratus.

Applied anatomy

Infection from palmar spaces may extend proximally into this space and form an hourglass swelling.

Question 12. Describe the ulnar and radial bursae in brief.
Answer.

Ulnar bursa

• It is a large synovial sac that encloses the tendons of flexor digitorum profundus (FDP) and flexor digitorum superficialis (FDS).
• Proximally, it extends up to 2.5 cm above the flexor retinaculum and distally up to proximal one-third of the metacarpal bones.
• Distally, on the medial side, it is continuous with the digital synovial sheath of the little finger.

Radial bursa

• It is synovial sheath around the tendon of flexor pollicis longus.
• Proximally, it extends about 2.5 cm above the flexor retinaculum and distally continuous with the synovial sheath of the thumb.

Dorsum of the hand

Question 1. Write a short note on anatomical snuffbox.
Answer.

It is an elongated triangular depression seen on the dorsal aspect of 1st metacarpal when the thumb is hyperextended.

Boundaries

Medial:

Tendon of extensor pollicis longus.

Lateral

• Tendon of abductor pollicis longus
• Tendon of extensor pollicis brevis

Floor:

Scaphoid, trapezium.

Roof:

Deep fascia stretching between the medial and lateral boundaries.

Contents

• Radial artery

Structures crossing the roof

• Cephalic vein
• Terminal branches of superficial radial nerve

Applied anatomy

• Tenderness in the region of anatomical box indicates fracture of scaphoid.
• Pulsations of radial artery can be felt at this site.

Question 2. What is dorsal subaponeurotic space? Give its applied importance.
Answer.

The dorsal subaponeurotic space lies between the aponeurotic sheath and the dorsal surfaces of medial four metacarpals and the dorsal interossei.

On the dorsum of hand, the extensor tendons of the fingers are bound to one another by oblique bands of deep fascia in such a manner as to form an aponeurotic sheath, which is attached to the borders of 2nd and 5th metacarpals on the lateral and medial sides, respectively.

Applied anatomy

The primary infection of this space is due to wounds on the dorsum. The space may be involved secondarily due to infections spreading from midpalmar space via the lymphatics.

Question 3. Give sensory innervation of the palmar aspect of the hand.
Answer.

• Lateral two-third of palm and lateral 3½ digits are supplied by the median nerve.
• Medial one-third of palm and medial 1½ digits are supplied by the ulnar nerve.

Question 4. Give sensory innervation of the dorsal aspect of the hand.
Answer.

• Lateral two-third of the dorsum of hand and lateral 3½ digits are innervated by the radial nerve.
• Medial one-third of the dorsum of hand and medial 1½ digits are innervated by the ulnar nerve.