Palm

 

1. Layer of skin

The hand is a useful apparatus in man for prehensile and brachiating activities. The palm is the fleshy part of the hand placed ventrally. Layer 1 of the palm skin is divided into the following parts- thenar eminence, hypothenar eminence, midpalmar area and the pulps of the fingers. On the skin of the palm we have the following creases- transverse, proximal digital, middle digital and distal digital creases. We also have hypothenar eminence, thenar eminence and pulp of fingers.

2. Layer of superficial fascia

This is layer 2 of the palm. It is the layer of superficial fascia. To recap we have removed the skin and its constituent parts such as the skin of the roof of the thenar space, hypothenar space, midpalmar space and exposed the structures below the skin which includes the superficial fascia. We have also exposed the palmar branches of the palmar branches of median nerve and ulnar nerves, proper digital nerves of hand, palmar digital veins, and the palmar venous plexus. In sum we have exposed the superficial fascia which includes the following structures- the palmar branches of median nerve and ulnar nerves together with the lateral cutaneous of forearm, proper digital nerves, palmar digital veins, and the palmar venous plexus. The layer of superficial fascia contains the following structures-[palmar branch of median nerve, palmar branch of ulnar nerve, lateral cutaneous nerve of forearm, superficial branch of radial nerve, palmar venous plexus, digital branch of median nerve, digital branch of ulnar nerve, proper digital nerve, and palmar venous plexus]

3. Palmar apponeurosis layer

We have now reached the palmar aponeurosis layer. Removal of the superficial fascia exposes the palmar aponeurosis. It also exposes the flexor retinaculum and the also fibrous flexor sheath, But in this layer we shall see the palmar aponeurosis and structures which surround it. To reach this layer we have removed the superficial fascia, the palmar venous plexus and the proper palmar digital veins. We can now see the palmar aponeurosis, digital nerves and digital vessels. The roof of the hypothenar space has now been removed to expose the structures underlying it. At this stage we can only see two muscles- abductor pollicis brevis and fflexor pollicis  brevis. In the hypothenar space we can only see the abductor digiti minimi. In sum we have exposed the palmar aponeurosis, common digital nerves and vessels, the thenar space which at this stage contains only two muscles- the abductor pollicis brevis and the flexor pollicis  brevis, the ulnar artery and the hypothenar space which contains only one muscle the abductor digiti minimi.

Layer 3 contains the following structures-[Palmar aponeurosis, common digital nerves and vessels, hypothenar space containing abductor pollicis brevis, flexor pollicis  brevis, hypothenar space containing abductor digiti minimi, and ulnar nerve]

4.  SUPERFICIAL PALMAR ARCH LAYER

We have now arrived at the layer of the superficial palmar arch after the removal of the palmar aponeurosis and the common digital nerves and vessels. We can now see clearly the midpalmar space containing blood vessels of the superficial palmar arch and nerves. Flexor retinaculum is also clearly seen. The lumbricals which arise from the radial sides of the flexor digitorum profundus can be clearly seen. The fibrous flexor sheath of each finger can also be clearly seen at this level. So also is the median nerve and the superficial branch of ulnar artery and the superficial branch of radial artery. Together they form the superficial palmar arch. In sum we have exposed this layer which contains the fibrous flexor sheath, the lumbricals, the superficial palmar arch consisting of the superficial branch of ulnar artery and the superficial branch of radial artery and the median nerve.

5.  LAYER OF SUPERFICIAL FLEXOR TENDONS

This is layer 5. The layer of superficial flexor tendons. Please check all items on the web page links. To recapitulate we have removed the superficial palmar arch, common digital nerves and vessels and the median nerve. Please use the dissector to interact with all the links.  Common synovial flexor sheath surrounds all the flexor tendons- in particular the ulnar bursa, which is the bursa that surrounds all flexor tendons together with the flexor tendon of the little finger. The tendons include the flexor digitorum superficialis which is the superficial tendon of the long flexors and the flexor digitorum profundus which is found only minimally in this layer. Flexor digitorum superficialis takes its origin from the common flexor origin and from other structures surrounding this origin and runs downwards under cover of the flexor retinaculum to reach the palm at the midpalmar space with its tendons which gain their insertion by splitting into two to accommodate the tendons of its deep neighbor flexor digitorum profundus.  They gain insertion into the base of the middle phalanges. While the superficialis is supplied in its entirety by the median nerve, the profundus has  two nerve supply with its ulnar head being supplied by the ulnar nerve and the radial part by the median nerve, through its anterior interosseous nerve.

The radial bursa is the synovial flexor sheath that surrounds the flexor pollicis longus which is placed on the thumb.

The long flexors take their origin from the common flexor origin origin at the medial epicondyle of humerus. The flexor pollicis longus takes its origin from the front of the radius. It is found in the radial bursa. We have now seen the last of the short muscles of the thumb which is the opponens pollicis.  In the thenar eminence these muscles are three in number. - the abductor pollicis brevis, the flexor pollicis  brevis and the opponens pollicis. They take origin mainly from the scaphoid tubercle, trapezium, and the flexor retinaculum, and they gain their insertion mainly into the base of the proximal phalanx of the thumb.

We have also seen most of the hypothenar eminence muscles. This is the opponens digiti minimi and we have seen the abductor digiti minimi. They also take origin from inside the palm from the hook of hamate and the flexor retinaculum. They are attached mainly to the base of the proximal phalanx of the little finger. The last of the space in the palm are the pulp spaces found in the fingers. The following are found in layer 5 - [common synovial flexor sheath, flexor digitorum superficialis tendons, flexor digitorum profundus tendons, flexor pollicis longus tendons, opponens pollicis, opponens digiti minimi, ulnar bursa, radial bursa and pulp spaces]. In sum we have exposed in this layer synovial flexor sheath, tendons of the flexor digitorum superficialis, tendons of flexor digitorum profundus, tendon of flexor pollicis longus, opponens pollicis and opponens digiti minimi.

6.  LAYER OF DEEP FLEXOR TENDONS

We have now arrived at the layer of the deep flexor tendons.  There is only one deep long flexors and that is the tendons of the flexor digitorum profundus. To recap we have removed flexor digitorum superficialis tendons and the common synovial flexor sheaths. We can now see the deep tendons clearly, The carpal tunnel and the flexor digiti minimi which is the last muscle of the hypothenar eminence. The deep tendon layer consist of deep long flexors, carpal tunnel, palmar ligaments of metacarpophalangeal joints, adductor pollicis, palmar metacarpal arteries and the deep branch of ulnar nerve and artery.  In sum, we have exposed the fibrous flexor sheath and the carpal tunnel.

7.  ADDUCTOR POLLICIS LAYER

We have now reached the adductor pollicis layer. To recap we have removed the flexor retinaculum, carpal tunnel, long flexor tendons, thenar muscles and hypothenar muscle. This is the deep branch of ulnar artery and nerve, palmar metacarpal arteries, adductor pollicis- its oblique head and its transverse head. Palmar ligaments of metacarpophalangeal joints, adductor pollicis compartment which contains the adductor pollicis. Adductor pollicis layer therefore consist of the following- adductor pollicis, deep branch of ulnar artery, and nerve, palmar metacarpal arteries, palmar ligaments of metacarpophalangeal joints.

8.  DEEP PLAMAR ARCH LAYER

We have now reached the deep palmar arch layer. It contains palmar interossei. It also contains the 1st dorsal interosseous, deep palmar arch formed from the deep palmar branch of ulnar artery, deep branch of ulnar nerve,, 1st palmar metacarpal artery and the palmar carpal arch.  This layer, which is the layer of the deep palmar arch contains the deep palmar arch., deep branch of ulnar nerve, palmar carpal arch and the first dorsal interosseous. In sum, we have exposed the branches of the deep palmar arch, lateral palmar metacarpal arteries, and branches of the deep ulnar nerve.

9.  LAYER OF INTEROSSEI AND JOINTS

We are now in a new layer called layer of interossei and joints. To reach this layer we have removed all neurovascular structures. We have now exposed the 2nd, 3rd and 4th dorsal interossei, hook of hamate, capitate, pisiform, lunate, palmar radiocarpal ligament. In sum we have exposed the dorsal interossei, some bones and landmarks such as hook of hamate, capitate, pisiform, lunate and the palmar radiocarpal ligament.

10. LAYER OF BONES

Bones of the hand include carpus, metacarpus and the phalanges.  We are now in the last layer of the palm which is the layer of bones. To recap on how to reach this layer we had removed palmar radiocarpal ligament, and dorsal interossei. The carpal bones are as follows-
   scaphoid
,   lunate, triquetrum, pisiform. This is the proximal row of bones. The distal row of bones are as follows- trapezium, trapezoid,   capitate
 and hamate. The metacarpus are five in number. Metacarpal I is for the thumb. Metacarpal II is for the index finger, metacarpal III  is for the middle finger, Metacarpal IV is for the ring finger and metacarpal V  is for the little finger. The

Phalanges of Hand are 14 in number. We have proximal, middle and distal for the medial digits with only proximal and distal for the thumb. In sum, we have exposed the bones of the hand  which include carpus, metacarpus and the phalanges. Layer 10 is the layer of bones. The carpal bones are arranged in two rows. The scaphoids, lunate, triquetrum and pisiform are proximal row, while the trapezium, trapezoid, capitate and hamate are in distal row of bone. You have the metacarpus which are 5 in number and the phalanges which are 14 in number.

Let us now examine the spaces/ compartments of the palm - there are -thenar space, hypothenar space, midpalmar space, ulna bursa, radial bursa, adductor pollicis compartment, pulp spaces. Let us recapitulate on the 10 layers of the palm.

 


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Creator: Oluwole Ogunranti