Wednesday, February 25, 2015

Thumb Anatomy


IN THIS ARTICLE:
  • Bones of the thumb
  • Joints of the thumb
  • Muscles of the thumb
  • Blood supply to the Thumb
The thumb is the first of the hands five digits, but it is not commonly referred to as a finger. The thumb possesses a unique and wide range of motion not shared by the hands other digits. Not only does it bend its knuckle, but the tip of the thumb can touch the tips of the fingers. This range of motion greatly assists in the ability to grasp and hold items. Anatomically, the thumb comprises of the metacarpal connected to the wrists trapezium carpal bone. This first metacarpal connects to the proximal phalanx. This connects to the thumbs distal phalanx, which is also the tip of the digit. Unlike fingers, the thumb does not possess an intermediate phalanx bone. The thumb is generally served oxygenated blood by the princip pollicis artery. The muscles of the thumb all contain the word "pollicis," and are distinguished by extensor, flexor, oppenens, and abductor designations. This includes longus and brevis descriptions. The first dorsal interosseus also serves the thumb.

Each thumb is made of three bones and two joints. 


Bones of the thumb
  • Distal Phalaynx
  • Proximal Phalaynx
  • 1st Metacarpal

Joints of the thumb
  • Inter-phalangeal or IP joint between the distal and proximal phalaynx.
  • The Metacarpo-phalangeal or MP joint between the 1st Metacarpal and the proximal phalanx.
Muscles of the thumb


Intrinsic (thenar)
Abductor Pollicis Brevis 
Adductor Pollicis 
First Dorsal Interosseous 
Flexor Pollicis Brevis 
Opponens Pollicis
Extrinsic 
Abductor Pollicis Longus 
Extensor Pollicis Brevis 
Extensor Pollicis Longus 
Flexor Pollicis Longus


Blood supply to the Thumb
The thumbs arterial supply is provided mainly through the terminal branch of the radial artery, the princeps pollicis. This artery crosses the first intermetacarpal space to run on the volar aspect of the MCP joint, where it divides into the ulnar and radial collateral arteries. The ulnar collateral artery is usually larger than the radial collateral artery, and it is often easier to repair during replantation.

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