Hand Anatomy
Your hands play an essential role in your everyday functioning. House chores, using a mobile phone, typing and playing sports—they all require critical functions to help you carry out fine and gross motor skills.
Several structures work together to make up your hands. They include:
- Blood vessels: Including your radial and ulnar arteries, these blood vessels deliver blood to your hands and fingers.
- Bones: Each hand contains 27 bones.
- Joints: Each hand has multiple joints that join two or more bones, allowing you to flex and bend your hands and fingers.
- Ligaments: Ligaments are connective tissues that hold joints and bones together.
- Muscles: Muscles in your hand extend from muscles in your arm. They work together to allow you to grip, grasp and do other hand movements.
- Nerves: Your brain sends pain and other sensations to your hands through nerves.
- Tendons: Tendons act as ropes and connect muscles to bones. When a muscle contracts, the tendon moves the bone.
- Summit Orthopedics hand experts in the Minneapolis/St. Paul area provide local care for hand injuries large and small.
Bones of the Hand
The 27 bones in your hand are distributed in your fingers, palms and wrists, divided into these three categories:
- Carpal bones: These eight bones are in your wrist. They connect to the two forearm bones to form the wrist joint.
- Metacarpal bones: Your palm contains the five metacarpal bones. They connect to the carpal bones in your wrist. Along the top of the palm, one metacarpal bone is connected to the small shafts of bone that form each of the fingers and thumb, forming your knuckle joints.
- Phalanges: These 14 bones make up your fingers and thumb on each hand. Each finger has three phalanges that connect, forming three joints in each finger. Each thumb has only two phalanges and one joint.
Joints
Your hand contains several joints that allow you to bend and straighten it, among other functions. There are three types of joints, which are classified by their location in the hand:
- Metacarpophalangeal joints: These joints are located where your fingers meet your palm. In everyday terms, these are called your knuckles. The ends of these bones are covered in smooth cartilage, which helps them glide easily.
- Proximal interphalangeal joints: Between the phalanges (but not in your thumb), you have small hinge joints that allow your fingers to bend and straighten.
- Distal interphalangeal joints: These joints connect the bones at the tips of the fingers. They’re essential to carrying out delicate hand movements, like playing a string instrument.
Ligaments and Tendons
The major ligaments in your hand help stabilize your hand movements, preventing joints from bending too far sideways or backward.
- The tendons in your hands are collagen-rich tissues that attach to muscles in the forearm. They travel from the forearm through the wrist and into the fingers. Your hands have two types of tendons:
- Flexor tendons: These tendons act as cables. They attach to the underside of the forearm bones, which bend the thumb and fingers. Your flexor tendons work when you make a fist or grasp an object.
Extensor tendons: The extensor tendons attach under your skin on the back of your wrist and fingers. They allow you to straighten your thumb and fingers.
Muscles
Many of the muscles that operate the hand are attached in the elbow or forearm and extend down to your hands. Some muscles are responsible for bending or straightening the wrists; others move the fingers or thumbs. Some small muscles that work our fingers and thumbs are anchored on our carpal bones.
Blood Vessels and Nerves
Your hand nerves begin at your shoulder. They travel down the arm into the hand alongside the blood vessels that supply the hand with blood. Nerves carry signals from the brain to move the muscles in the arm, hand, fingers and thumb. They also carry signals from the hand back to the brain to communicate sensations like touch, pain and temperature.
Conditions That Affect Hand Anatomy
Your hands are powerful, yet delicate structures. Issues within any part of the hand can lead to swelling and pain that limit your ability to use your hands.
Conditions That Affect Bones and Tendons
- Boxer’s fracture: A fracture in the fifth metacarpal bone of the hand, typically from a punching injury
- De Quervain’s tendinitis: Inflammation of the tendons that extend the thumb, leading to pain and weakness during thumb or wrist motion
- Dupuytren’s contracture: A thickening of the hand tissue and skin that could lead to mild to severe contractures of the hand or fingers
- Finger dislocation: When the finger bone pops out of its joint, causing a visible deformity
- Ganglion cysts: Fluid-filled sacs that typically originate from a joint or tendon sheath and can develop throughout the wrist or hand
- Hand arthritis: Swelling and irritation in the hand joints
- Hand and wrist fractures: A break in one of the bones of the hand or wrist
- Mallet finger: Occurs when a fingertip injury in the top joint of the finger prevents the fingertip from fully extending
- Trigger finger: When a swollen tendon prevents one of the fingers from straightening, which can cause the finger to click or catch
Conditions That Affect Hand Nerves
Carpal tunnel syndrome: Narrowing of the carpal tunnel at the wrist, causing compression of the median nerve. This can cause numbness or tingling in the thumb or index, middle and ring fingers.
- Nerve injuries: Trauma, hand compression and underlying medical conditions, such as diabetes, can injure your hand nerves, causing numbness, tingling, weakness, sensitivity to temperatures and other symptoms.
- Ulnar neuritis: The ulnar nerve (a nerve that travels from your shoulder to your hand) becomes compressed, causing pain, weakness, numbness or tingling along the ring and pinky finger.
Sprains and Strains
A hand sprain involves damage to a ligament, the tissue that connects bones. Hand strains affect muscles and tendons, the tissues connecting your muscles to a bone. Falling on an outstretched hand is one of the main causes. These falls typically happen during sports or other high-impact activities. Both strains and sprains cause pain and can make it difficult to move your hand as you usually would.
Find your Summit Orthopedics hand and wrist care expert, request an appointment or call us at (651) 968-5201 to schedule a consultation.
