Topographic anatomy of the hand (with transverse section) and fingers
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Topographic Anatomy of the Hand and Fingers


The hand is one of the most intricate anatomical regions, consisting of bones, muscles, tendons, ligaments, nerves, and blood vessels that allow for a wide range of movement and fine motor control. The topographic anatomy of the hand includes its *skeletal framework, **muscles, **tendons, **neurovascular structures, and **skin. The **fingers* are an extension of the hand and involve highly specialized structures for movement and sensory function.


### *1. Skeletal Anatomy of the Hand*


The hand is made up of three main bone groups:

1. *Carpal Bones* (wrist):

  - The wrist is composed of two rows of carpal bones (proximal and distal).

  - *Proximal row*: Scaphoid, Lunate, Triquetrum, Pisiform.

  - *Distal row*: Trapezium, Trapezoid, Capitate, Hamate.


2. *Metacarpal Bones*:

  - These are the five long bones that connect the wrist to the fingers.

  - They form the palm and are numbered 1 to 5 starting from the thumb.


3. *Phalanges*:

  - Each finger has three phalanges (proximal, middle, and distal), except the thumb, which has only two (proximal and distal).

  - These bones articulate with the metacarpals at the metacarpophalangeal (MCP) joints and between each other at the interphalangeal (IP) joints

### *2. Muscles of the Hand*

The muscles of the hand are divided into two main groups: *extrinsic* (muscles that originate in the forearm) and *intrinsic* (muscles that originate and insert within the hand).


#### *Intrinsic Muscles*:

These muscles are essential for fine motor control and can be divided into four groups:


1. *Thenar Muscles* (Thumb muscles):

  - *Abductor pollicis brevis*: Abducts the thumb.

  - *Flexor pollicis brevis*: Flexes the thumb.

  - *Opponens pollicis*: Opposes the thumb (brings the thumb across the palm).

  - *Adductor pollicis*: Adducts the thumb.


2. *Hypothenar Muscles* (Little finger muscles):

  - *Abductor digiti minimi*: Abducts the little finger.

  - *Flexor digiti minimi brevis*: Flexes the little finger.

  - *Opponens digiti minimi*: Opposes the little finger.


3. *Lumbricals*:

  - Four small muscles that flex the metacarpophalangeal joints and extend the interphalangeal joints of the fingers.


4. *Interossei*:

  - *Palmar interossei*: Adduct the fingers toward the middle finger.

  - *Dorsal interossei*: Abduct the fingers away from the middle finger.


#### *Extrinsic Muscles*:

These muscles originate in the forearm and control both gross and fine movements of the hand.


- *Flexor tendons*:

  - *Flexor digitorum superficialis (FDS)*: Flexes the middle phalanges at the proximal interphalangeal (PIP) joints.

  - *Flexor digitorum profundus (FDP)*: Flexes the distal phalanges at the distal interphalangeal (DIP) joints.

- *Extensor tendons*:

  - *Extensor digitorum*: Extends the fingers.

  - *Extensor pollicis longus* and *brevis*: Extend the thumb.


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### *3. Neurovascular Structures of the Hand*


#### *Nerves*:

The hand receives innervation from three main nerves:

- *Median nerve*:

  - Supplies the thenar muscles, the first and second lumbricals, and the skin of the lateral palm and first three fingers.

- *Ulnar nerve*:

  - Innervates most of the intrinsic hand muscles, including the hypothenar muscles, interossei, and the medial two lumbricals. It also provides sensation to the medial palm and little finger.

- *Radial nerve*:

  - Supplies sensation to the dorsal aspect of the hand and the lateral part of the thumb.


#### *Blood Supply*:

The hand is primarily supplied by the *radial* and *ulnar arteries*, which form two arterial arches:

- *Superficial palmar arch*: Mainly formed by the ulnar artery.

- *Deep palmar arch*: Mainly formed by the radial artery.


Both arches give off branches that supply the fingers via the *digital arteries*.


*4. Topographic Relations and Movements*


The hand’s movement is complex and involves both *extrinsic* and *intrinsic muscles*, along with tendons, ligaments, and joint structures. The topography of the hand and fingers is especially important in fine motor control, precision grip, and power grip.


#### *Movements of the Fingers*:

- *Flexion and Extension*: Occur at the MCP, PIP, and DIP joints.

- *Abduction and Adduction*: Performed by the interossei muscles.

- *Opposition: Movement that brings the thumb across the palm toward the fingers, primarily performed by the **thenar muscles*.


*Movements of the Thumb*:

- *Flexion/Extension*: Movements in the coronal plane.

- *Abduction/Adduction*: Movements in the sagittal plane.

- *Opposition*: A complex motion that combines flexion and abduction.


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*5. Transverse Section of the Hand*

When viewing a *transverse section* through the hand at the level of the metacarpals, the following structures can be identified (from superficial to deep):

- *Skin and subcutaneous tissue*.

- *Palmar aponeurosis*: A thickened triangular fascia.

- *Flexor tendons: Passing through the carpal tunnel, including the **FDS* and *FDP* tendons.

- *Median nerve*: Located between the tendons of the FDS and flexor carpi radialis in the carpal tunnel.

- *Ulnar nerve and artery*: Running along the ulnar side of the hand.

- *Radial artery*: Found on the radial side, supplying the deep palmar arch.


6. Clinical Considerations*:

- *Carpal Tunnel Syndrome*: Compression of the median nerve within the carpal tunnel leading to pain and sensory loss in the hand.

- *Dupuytren’s Contracture*: Thickening of the palmar fascia causing fixed flexion of the fingers.

- *Trigger Finger*: Swelling or inflammation of the flexor tendons, causing difficulty in finger movement.