DAVE WATTS, MD
Normal Hand Anatomy
Wrist, fingers, and palm make up the human hand. The hand is considered one of the softest parts of the human body. It enables us to perform many vital functions of our daily lives. The malfunction of hands or wrists can severely impact basic tasks like bathing, cooking, and drive a car.
Diseases and conditions affecting the hand need to be understood to get the right kind of medical assistance.
There are eight bones in the wrist, also known as carpal bones. These eight bones connect to 5 metacarpal bones. This entire structure forms palm of the hand. Each of the carpal bone connects to create one finger or thumb at a joint known as metacarpophalangeal or MCP joint or knuckle joint.
The bones in fingers and thumbs are called phalanges. Each of the fingers contains three phalanges separated by two joints. The first joint is closest to the knuckle joint and known as proximal interphalangeal or PIP joint. The second joint which is near to the end of the finger is called interphalangeal or DIP joint.
Soft Tissue Anatomy
Many soft tissues in the body support the hand and wrist. Let us have a look.
Cartilage is a shiny and smooth, allowing natural movement where two bones come in contact with one another.
Tendons connect muscles to bones to provide stability, structure, and support. The extensor tendons in our hand enable us to straighten the fingers.
The rope-like tissues are called ligaments. These muscular tissues help connect bones with other bones. They bridge tendons by providing stability in joints. Volar plate, considered the strongest hand ligament, prevents hyperextension of the PIP joint.
Muscles facilitate movement of the body parts by performing the contracting and flexing function. There are no muscles in the fingers. There are smaller muscles which originate from carpal bones of wrists by connecting them to finger bones using tendons. These muscles facilitate the movement of the thumb and little fingers. They help the hand to hold objects and grip things by enabling thumb movement across the palm. This movement is also called the thumb opposition. The smallest muscles of the wrist and hand help in perfecting fingers’ fine motor movements.
Nerves carry signals back and forth from brain muscles in the human body. These back and forth signals ensure movement, sensation, pain, and feeling of touch, hot, or cold.
These are the three nerves responsible for movement in hand.
The radial nerve running down the thumb side of the forearm helps feel sensation to the back of the hand from the thing and third finger.
The median nerve travels through wrist tunnel, also known as carpal tunnel. Median is responsible for providing sensation to the thumb, index finger, long finger, and part of the ring finger.
The ulnar nerve passes through a wrist tunnel called Guyon’s tunnel. Two carpal bones and ligament binding them together to form a tunnel. The ulnar nerve delivers feelings to the little finger and half the ring finger.
There are two main vessels in the hand and wrist area.
The radial artery is the largest in the hand and wrist area. It travels through the front of the wrist and is nearest to the thumb. This artery palpates when a pulse passes through the wrist.
Ulnar artery lies next to the ulnar nerve. It passes through Guyon’s canal in the wrist. This artery ensures blood flow to hand’s front, fingers, and thumb.