Our bodies are home to miles of veins, muscles, bones, and ligaments that allow us to do everything from breathing to mastering an instrument. We tend not to think about our bodies until something goes wrong, though.
What use is knowing about the anatomy of the hand unless you need to mend a broken finger or ease pains from carpal tunnel? For one, knowing the ins and outs of your body can help you to keep it healthy.
Additionally, the function of our bodies is pretty amazing when you put all of the pieces together. We’re going to talk about the hand and wrist today, unpacking the specifics of what they’re made of and how they work.
Anatomy of the Hand and Wrist
You’re reading this on some sort of device. Whether it’s a laptop, cell phone, or a tablet doesn’t matter.
Any process that led you to this article involved a highly sophisticated performance from your hands and wrists. Precise movements carried out in sequence by your fingers allowed you to pick up the device, press specific buttons, and end up here.
While it feels natural to use your hands and wrists in this way, the anatomy involved in the process consists of numerous, finely-tuned body parts that work without you ever having to think about them.
We’re going to break down that anatomy in this article, hopefully giving you a deeper understanding of the ways in which you work and how to keep yourself healthy.
Bone System
We’ll start by describing the right hand resting in a palmar position. This simply means you can imagine your hand flipped up, with the palm facing you and the top of the hand (the dorsal side) resting on some surface.
The wrist is started by a couple of large bones that actually start at the elbow and move down to the base of the wrist. These are called the ulna and the radius.
These two bones are the primary elements of your forearm. The radius has the smaller base at the elbow, but a larger base at the wrist. So, looking at our palmar right hand, the ulna comes in smaller on the left side while the radius is larger and sits at the right side of the base of your hand.
You can think of the side of your hand with the thumb as the “radial side,” and the side with your pinky as the “ulnar side.”
Moving upward from the ends of the ulna and radius, we have the carpal bones.
The Carpal Bones
Medical professionals may refer to the wrist as the “carpus.” Carpus is simply another name for the wrist. So, when you think of the carpal bones, remember that they are the bone system that makes up the wrist.
These are a cluster of eight bones that exist at the bases of the radius and ulna. Starting on the radial side near the base of the wrist and moving toward the ulnar side, we have the scaphoid, lunate, triquetral, and pisiform. Because this row is effectively closer to us than the next, we call it the proximal row.
Proximal and distal are terms that indicate the distance from a point of reference.
So, the next row is going to be the distal row. Starting on the radial side nearest to the thumb, we have the trapezium, trapezoid, capitate, and hamate. These bones form a tighter cluster.
You can think of the two rows of the carpal bones as two rows of seats in an auditorium: as space gets tighter, the seats must get closer to one another. The distal “row” of carpal bones has the same number, they are just contained closer to one another.
We’re going to come back to the carpal bones when we discuss tendons and nerves, seeing as the carpal area plays a huge role in directing and containing tendons and nerves. Additionally, many people are likely curious about the nature of carpal tunnel syndrome, which we will discuss.
Confused Yet?
If you’re feeling a little lost already, don’t worry too much. There’s an easy way to remember the first letters and positions of all of the carpal bones.
Remember, “So Long To Pinky, Here Comes The Thumb.”
Imagine the carpal bones moving in a clockwise circle, starting on the radial side of the lower row.
Scaphoid, Lunate, Triquetral, Pisiform, Hamate, Capitate, Trapezoid, Trapezium.
The first letter of each word in the “So Long To Pinky, Here Comes The Thumb” phrase matches that of the carpal bone in its place. Additionally, the “P” bone is actually the one closest to the pinky, and the bones then progress closer to the thumb as the phrase suggests.
The Metacarpal Bones
The metacarpal bones consist of five bones, each one of them associated with a finger. These bones form the base of each finger and are referred to by a digit. The thumb’s metacarpal is “metacarpal 1,” and the process continues all the way down to the pinky which is, you guessed it, “metacarpal 5.”
These bones are made up of a head, body, and base. The base is where the metacarpal connects down to the carpal bone, followed by the body, which connects at the head to the phalanges, which we’ll cover next.
The Phalanges
The metacarpal bones and phalanges are connected by joints that we refer to as knuckles. These joints are called metacarpophalangeal joints and work like hinges when we want to move and bend our fingers.
Each finger consists of three phalanges, except for the thumb which only has two. You can clearly see the separate phalanges from the outside of your hand. Phalanges are connected by interphalangeal joints which operate similarly to metacarpophalangeal joints.
Muscle System
When thinking of hand muscles, we must think in two categories: intrinsic and extrinsic.
Extrinsic muscles of the hand are ones that originate outside of the hand or enter the hand from the arm and forearm. These muscles control the fundamental, broader movements of the hand.
Intrinsic muscles are ones that exist solely within the hand and are responsible for fine, more specific movements. This duality is easy to recognize when you think of extrinsic muscles predominantly controlling the wrist and intrinsic muscles controlling the fingers.
For the purposes of this article, we’ll focus more closely on the ligaments and tendons of the hand, as they are more pertinent to most people’s concerns about hand and wrist health.
Tendons
Most of the movement you experience in your fingers originates back into the forearm. Tendons called “flexor tendons” continue through your wrist from your forearm and connect to the base of your metacarpal bones.
Each time you move any finger, these tendons slide through tendon sheaths that lie in your carpal bones. Tendon sheaths keep your tendons in line and connected to their respective bones.
Tendons attach to the end of muscles and serve as a connection from muscles to bone. Muscles contract to dictate movements and tendons respond accordingly to move the bones associated with those movements.
There are a number of tendons in the hand and wrist.
Superficialis tendons move through the wrist on the palmar side and connect all the way up to the middle phalanges. These serve to move the wrist and base of fingers.
Profundus tendons pass through a similar area of the carpal bones and attach to the middle and upper phalanges. They offer additional movement of the wrist and provide more specific movements for the fingers.
Extensor tendons exist primarily in the fingers and serve to extend the wrist, attach the distal and middle phalanges. Flexor tendons pass through the carpal tunnel and split when they reach the palm.
There are nine flexor tendons, and two are assigned to each of the primary fingers while one is assigned to the thumb.
Ligaments
Ligaments consist of connective tissue and ensure that the bones of the hand are kept where they’re supposed to be.
The collateral ligaments exist on both sides of your fingers and thumbs, keeping the joints from moving too far on either side. Essentially, they ensure that your fingers don’t slide and bend in unnatural directions.
The volar plate is a ligament that serves to keep your phalanges from bending too far backward. Radial and ulnar joints are found at the root of the wrist and support the area where the radial and ulnar bones connect to the carpal bones.
The volar radiocarpal ligaments are in place to support the palmar side of the base of your hand. Dorsal radiocarpal ligaments serve the same purpose, except for they function on the back of your hand.
The ulnocarpal and radioulnar ligaments are two primary ligaments that do the heavy lifting of support for your wrists.
Finally, the transverse carpal ligament is a group of connective tissue that extends horizontally over the palmar side of your carpal bones. This is a ligament that covers up the nerves and other ligaments that pass through the carpal tunnel. The ligament “transverses” the carpal bones, hence its name.
Carpal Tunnel Syndrome (CTS)
Carpal tunnel syndrome is the reason that a lot of people look into the anatomy of the hand. The carpal tunnel is the space between the carpal bones where the flexor tendons pass.
In order to understand the syndrome and how it works, we’ll have to do a brief exploration of a few nerves.
Essential Nerves of the Hand and Wrist
We’ll discuss two of the main nerves involved in the sensation of our hands. First, we have the median nerve.
This is a nerve that passes through the carpal tunnel and branches out at the palm to your thumb, pointer, and middle finger. Remember that the median nerve rests under the transverse carpal ligament. When the nerve arrives at each respective finger, it branches out into a few arms to reach all of the areas it needs to.
The next nerve is the ulnar nerve. This is the nerve that moves up to your fourth and little fingers. The difference between the median and ulnar nerves, though, is that the ulnar nerve runs up the ulnar side of your hand and doesn’t pass under the transverse carpal ligament.
How CTS Develops
Carpal Tunnel Syndrome develops when the median nerve is pinched or compressed. Because it sits at the top of the stack, just below the transverse carpal tendon, compression or pinching can occur as a result of contact with the nerve.
There are a number of ways a person could develop CTS, and any inflammation or irritation can be amplified by the transverse carpal tendon. The disorder gets progressively worse and can be extremely painful.
People experience distinct, sharp pain of the wrist, some numbness, and more. Early signs of CTS are typically related to fingers falling asleep and general tingling. Because the median nerve runs all the way up to the shoulder, you might notice these symptoms throughout your arm.
The syndrome is usually developed as a result of repetitive motions of the hand and wrist. Things like typing, knitting, and any other activity that involves long, repetitive actions can eventually lead to CTS.
If you never treat the symptoms, they are likely to get worse. Untreated Carpal Tunnel Syndrome can lead to loss of sensation in the fingers affected by the median nerve, slower nerve impulses and responses to stimuli, even the loss of the ability to use your thumb.
What To Do if You’re Experiencing Symptoms
If you feel like you might be experiencing symptoms of carpal tunnel, your best bet is to go in and talk to a professional. While braces and lifestyle changes can benefit the symptoms, you’ll develop a deeper understanding and get specific instructions for recovery through a professional.
Carpal Tunnel Syndrome is also something you should try and catch early. Waiting will only cause you to experience intense pain that may have been prevented if it were treated early on.
Want to Learn More?
The anatomy of the hand and wrist is an amazing, complicated thing. Hopefully, this article helped you to get a better grasp of that anatomy, especially as it relates to Carpal Tunnel Syndrome.
If you’re interested in learning more about the hand and wrist and how to keep it healthy, explore our site for the information you need.
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