Hand Anatomy

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Hand Anatomy

 

 

Welcome to Hicksville Physical Therapy's patient resource about the anatomy of your hand and the injuries it can receive. Please see the left hand menu for specific information.

If you think about it, the hand is an amazing body part. There’s no other structure that’s quite like it. The hand is able to perform many different motor tasks with fine precision, and is able to do so due to the muscles that let us bend our wrists, and the flexibility and coordination of our thumbs and fingers. Our hands are integral to our existence, and require proper alignment and control to function properly.

Our guide is here to help you understand:

  • The parts that the hand consists of
  • How these parts work together

Bones and Joints

The wrist and hand contain 27 bones. The wrist has eight small bones called carpals that pair with the forearm bones, the radius and ulna, to form the wrist joint. The carpals are in proximity to the five metacarpal bones that make up the palm; one metacarpal also connects to each of your fingers and thumbs. You also have bone shafts called phalanges that make up your fingers and thumbs.

Carpals

The phalange and metacarpal connect to form your metacarpals. The joints where the phalange and metacarpal meet are called metacarpophalangeal joints (MCP joints). These joints act like a hinge, and are the ones that allow for you to grip and pinch things.

Metacarpophalangeal Joints

 

 

There are three phalanges in each finger, and each of these phalanges are separated by two joints called the interphalangeal joints, or IP joints. The one closest to the knuckle, or the MCP joint, is called the proximal IP joint (PIP joint) while the one near the end of your finger is the distal IP joint, or the DIP joint. In contrast to the rest of your fingers, the thumb only has one IP joint between its two phalanges. Your IP joints are similar to your MCP joints, also working like hinges as your fingers bend and straighten.

 

These mentioned joints are covered by a rubbery, smooth white tissue called the articular cartilage. Your articular cartilage works as a shock absorber and facilitates movement, and allows your bones to move against each other with minimal friction, or articulate.

Articular Cartilage


Ligaments and Tendons

Ligaments are tough bands of tissue that connect and stabilize bones, holding them in place and allowing joints to move.  Two of these structures, your collateral ligaments, can be found on each side of your fingers and thumbs. Collateral ligaments are meant to prevent your finger joints from bending sideways, or abnormally.

Collateral Ligaments

 

Between the main knuckle and DIP joint in your PIP joint is the volar plate. This thick ligament is the one that connects the proximal phalanx to your middle phalanx on your joint’s palm side, and is responsible for tightening when the joint is straightened. It also keeps your PIP joint from hyperextending, or from bending back too far. If your finger is hit straight on or bent backwards, or you have a disease like arthritis, deformities to the plate can occur.

Volar Plate

Extensor tendons are the tendons that allow your fingers to straighten. They are attached to muscles in your forearms and continue into your hand, connecting to the extensor tendons located there before crossing over to your wrist. The extensor tendons become the extensor hood as they travel into your hand; the hood flattens out to cover the top of your fingers, and then branches on each side to connect to the bones in the middle and end of your fingers.

Extensor Hood

The central slip is the place where the extensor tendon is attached to the middle phalanx. As the extensor muscles contract, the extensor tendon is tugged and straightens the finger. Central slip injuries commonly happen if the finger is bent too far back (usually due to a sport ie: hit by a ball), or if the joint is dislocated.

Central Slip

Muscles

Many muscles that control your hands start at the forearm or elbow, and run down from the forearm to cross the wrist and hand. The muscles have a wide range of functions: some are limited to controlling your wrist’s ability to bend and straighten, while others contribute to the motion of your fingers and thumbs. These muscles are also responsible for positioning and stabilizing the wrist while your thumb and fingers perform actions like gripping or pinching things.

Your carpal bones have specific muscles that help your thumb and pinky function as well, allowing for your hand to hold and grip an object. Thumb opposition is the important function that makes humans and types of primates distinct; our muscles allow the thumb to move across the palm of the hand, lets our thumb touch our fingertips and allows us to grasp objects purposefully.

Hand Muscles

Thumb Opposition

Intrinsic muscles guide finger movements by positioning the fingers and stabilizing them during hand activities. They are small muscles that can be found in your wrist and hand.

Nerves

The nerves that control all of your hand’s muscles start at the shoulder: the radial nerve, median nerve, and ulnar nerve. These nerves are integral to all the things your hands do and to how your hands feel. They carry signals from the brain to the muscles that move your arms, hands, fingers and thumbs, and then carry signals from those body parts back to the brain about the sensations you feel (touching a texture, feeling pain and temperature).

 

The radial nerve wraps around the end of the radius bone towards the back of the hand, from the thumb side of your forearm. It allows for you to feel sensations in the back of your hand, from the thumb to the third finger. The radial nerve also gives sensation to the back of the thumb, to the main knuckle and backs of the ring and middle fingers.

Radial Nerve

The median nerve travels through the wrist in a vessel called your carpal tunnel. You’ve definitely heard of the carpal tunnel, as many people are prone to experiencing carpal tunnel syndrome. The median nerve is responsible for many of your fingers’ abilities to feel sensations (thumb, index finger, long finger, half of the ring finger), and also has a nerve branch that controls the thumb’s thenar muscles. These muscles are the ones that specifically help your thumbs be opposable, permitting your fingertips and the pads of your thumbs to touch if they are on the same hand.

Median Nerve

Meanwhile, the ulnar nerve proceeds through a different tunnel called the Guyon’s canal. The Guyon’s canal is formed by two carpal bones (pisiform and hamate) and a ligament that makes them attach. The ulnar nerve, traveling through the canal, supplies the little/pinky finger and the other half of the ring finger with sense capability. Ulnar branches also help muscles in the palm and thumb to feel as well.

Ulnar Nerve

Your hands are multifunctional and help you with pretty much everything in your daily life, thus the nerves that control them can be subject to many issues. Movements like constant bending, twisting and straightening of the wrists and fingers can lead to these nerves suffering irritation and pressuring their tunnels. Symptoms may include pain, numbness/lack of sensation, and your fingers/hands/thumbs becoming weak.

Blood Vessels

Alongside the nerves are vessels that supply your hands with blood, allowing for them to receive nutrients. The largest artery is called the radial artery, traveling across the front of the wrist; it is where you can feel your pulse. The ulnar artery runs in proximity to your ulnar nerve, through the Guyon’s canal. These two large arteries arch together in the palm of your hand and allow blood to course through the front of your hand, fingers and thumb. Different arteries travel on the back of your wrist to provide blood to the back of your hand, fingers, and thumbs.

Radial Artery


Summary

The hand consists of many different kinds of structures that work together and allow for your hands to function in daily life. If your hand is injured, or if you start to suffer from a disease or condition that affects your nerve health or muscles, your hand function may be compromised. This body part is amazingly complex, but easy to take for granted if they’re healthy. Be sure to take care of your hands so your daily life can continue with ease.

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