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Bones of the Hand: Carpals, Metacarpals & Phalanges
Bones of the Hand: Carpals, Metacarpals & Phalanges
Includes labeled diagrams, downloadable notes, anatomy quizzes, and interactive learning tools
The human hand provides significant mobility and a wide range of motion for lifting, carrying, and manipulating objects. The bones of the hand include the carpal bones (eight bones), metacarpal bones (five bones), and phalanges (fourteen bones).
Carpal Bones
The wrist and the base of the hand are formed by eight small bones called carpal bones. These bones are arranged in two rows of four: a proximal row and a distal row.
In the proximal row, from the thumb (lateral) side to the little finger (medial) side, the bones are the scaphoid, lunate, triquetrum, and pisiform.
The scaphoid is the largest bone in this row and is shaped like a boat. The lunate has a crescent shape. The triquetrum is pyramidal in shape. The pisiform is small, rounded, and lies in front of the triquetrum. It forms a bony bump that can be felt on the inner side of the wrist.
In the distal row, from lateral to medial, the bones are the trapezium, trapezoid, capitate, and hamate.
The trapezium has a groove on its front surface and forms a saddle-shaped joint with the first metacarpal. The trapezoid is the smallest bone in this row and is wedge-shaped. The capitate is the largest carpal bone and sits in the center of the wrist. The hamate is wedge-shaped and has a hook-like projection on its front surface.
The carpal bones form the base of the hand and appear in a U-shaped arrangement. The proximal row is held together by ligaments and acts as a unit.
The scaphoid, lunate, and triquetrum bones take part in the wrist (radiocarpal) joint. The scaphoid and lunate connect directly with the radius, while the triquetrum connects through a fibrocartilaginous pad. The ulna does not directly articulate with the carpal bones.
The distal row is also held together by ligaments. The proximal and distal rows connect to form the midcarpal joint. Together, the radiocarpal and midcarpal joints allow all wrist movements. The distal carpal bones also connect with the metacarpal bones.
A strong ligament called the flexor retinaculum stretches across the front of the carpal bones, attaching laterally to the scaphoid and trapezium, and medially to the pisiform and hamate. This creates a passage called the carpal tunnel. The carpal bones form the walls and floor, while the ligament forms the roof. Tendons from nine forearm muscles and a nerve pass through this narrow space. Swelling in this area can compress the nerve, causing carpal tunnel syndrome, which leads to pain, numbness, and muscle weakness in the hand.
Metacarpal Bones
The palm contains five long bones called metacarpals, numbered one to five starting from the thumb. These bones lie between the carpal bones and the finger bones.
The first metacarpal, which belongs to the thumb, is shorter, stronger, and more mobile than the others. It is separate from the other metacarpals, allowing greater movement.
The second and third metacarpals are firmly fixed and do not move much.
The fourth and fifth metacarpals have some forward and backward movement, especially the fifth, which helps with strong gripping actions.
Each metacarpal has a base (near the wrist), a shaft (body), and a head (near the fingers). The base connects with the carpal bones and sometimes with neighboring metacarpals. The head connects with the proximal phalanx of each finger and forms the knuckles.
The shafts of the metacarpals are slightly curved, with rough areas for muscle attachment. The bases are broader and connect with the wrist bones, while the heads are rounded and form joints with the fingers.
Phalanges
The fingers and thumb contain 14 bones called phalanges. The thumb (digit 1) has two phalanges: a proximal and a distal. The other fingers (digits 2–5) each have three phalanges: proximal, middle, and distal.
Each phalanx has a body and two ends. The bodies are shaped so they are convex on the back and concave on the front. The ends form joints with neighboring bones.
The joints between phalanges are called interphalangeal joints.
Need a recap? Take a look at the bones of the hand anatomy notes here.
Need a recap? Take a look at the bones of the hand anatomy notes here.
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References
References
Gray, H. (1918). Anatomy of the human body (W. H. Lewis, Ed.; 20th ed.). Lea & Febiger.
J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix. (2013, April 25). Anatomy and Physiology. OpenStax. https://openstax.org/books/anatomy-and-physiology/pages/8-2-bones-of-the-upper-limb.
Based on OpenStax, Anatomy and Physiology (2013), licensed under CC BY 4.0.
Access for free at https://openstax.org/books/anatomy-and-physiology/pages/1-introduction.
Content paraphrased; adaptations were made.
Sobotta, J. (1914). Atlas and text-book of human anatomy (J. P. McMurrich, Ed.; W. H. Thomas, Trans.). W.B. Saunders Company.
Image Credis
Image Credis
Images used in this guide and games are from the following source:
Sobotta, J. (1914). Atlas and text-book of human anatomy (J. P. McMurrich, Ed.; W. H. Thomas, Trans.). W.B. Saunders Company.
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