hand

 

How are the hand and wrist structured?

Your hand and wrist are structured to allow you to move, flex and rotate your wrist joint and to use your hand to grab and touch objects.

Your wrist acts like a pivot point that can move in almost any direction as you reach and flex your hand. Think about your hand and wrist like a crane game at an arcade. Your hand is the claw that grabs and holds prizes, and your wrist is the mechanical joint that lets the claw move up and down, and side to side.

Hand and wrist anatomy

The parts that make up your hand and wrist are layered upon each other to form a three-dimensional shape that gives them the ability to move and function.

Your hand and wrist are made of:

• Bones.
• Muscles.
• Nerves.
• Tendons.
• Ligaments.
• Blood vessels (arteries and veins).
• Lymphatic vessels.

Hand and wrist bones

Bones provide the main structural support in your hand and wrist. They give them their shape and are the anchors other pieces are connected to.

Hand bones

There are 19 bones in each of your hands. They’re grouped together by their location and function:

• Metacarpals: The bones that are in your palm and give it its shape.
• Phalanges: The individual bones that make up the segments of your fingers and thumb.
• Sesamoids: Small bones embedded in your tendons that help them move smoothly.

Wrist bones

Your wrist is a complex joint made of eight bones that are arranged into two rows.

The proximal row (on the back of your hand, closest to your forearm) includes the:

• Scaphoid.
• Lunate.
• Triquetrum.
• Pisiform.

The distal row (on the underside of your wrist closest to your palm) includes the:

• Trapezium.
• Trapezoid.
• Capitate.
• Hamate.

Your radius (the larger of the two bones in your forearm) forms a joint your scaphoid and lunate bones to form the part of your wrist that helps it move and rotate.

The carpal tunnel is a rounded space between your pisiform, hamate, scaphoid and trapezium. This space is a literal tunnel in your wrist that lets nine tendons, four ligaments and one nerve pass through it to reach the rest of your hand.

Your carpal tunnel is similar to the way that fiber optic cables are buried underground to deliver internet or cable TV service to your home.

Hand and wrist muscles

Muscles are soft tissue made of stretchy fiber. Intrinsic muscles inside your hand work with extrinsic muscles near the outside of your hand and in your forearm to give your hand its strength and dexterity.

Hand muscles

There are 34 muscles in each of your hands. Healthcare providers categorize them into groups, including:

• Thenar muscles: Muscles that control your thumb. You can feel them bulge at the base of your thumb in the palm of your hand.
• Hypothenar muscles: These muscles line the outer edges of your palm on the outside of your pinkie finger. They control the area of your hand that’s opposite your thumb.
• Interossei muscles: Interossei muscles are between the metacarpal bones in your palm. They help your fingers move side-to-side.
• Lumbrical muscles: Lumbrical muscles are at the base of your four non-thumb fingers. They help you flex your fingers.

Your muscles and all their possible movements perform two types of grip:

• Power: This is where your grip strength comes from. Think about picking up a heavy box or opening a jar.
• Precision: Precision is using your hand and fingers to move or touch a smaller object. Precision grip uses your fingers’ ability to meet your thumb (sometimes called an opposable grip) to pinch something between them. Picking up a pen off your desk and turning a key in a lock are precision grip motions.

Wrist muscles

Your wrist shares muscles with your forearm. Their groups include:

• Flexion: Muscles that let you move your wrist down, toward your palm.
• Extension: Muscles that pull your wrist up, like you would to make a “stop” gesture at someone in front of you.
• Adduction: Muscles that let you bend your wrist in, toward the center of your body.
• Abduction: Muscles that let you bend your wrist out, away from the center of your body.

Hand nerves and wrist nerves

Nerves control your muscles and help you feel and process sensations, including:

• Touch.
• Temperature.
• Pain.
• Pressure.

Three main nerves give your hand and wrist sensation:

• Radial nerve.
• Median nerve.
• Ulnar nerve.

All three of these nerves are connected to many branches of smaller nerves that spread out into your hand and wrist.

Hand and wrist tendons

Tendons link your muscles to your bones. They’re like strong, flexible ropes. Your hand and wrist have two groups of tendons:

• Extensor tendons: Tendons that help you extend and straighten your fingers, hand and wrist.
• Flexor tendons: Tendons that help you flex and curl your fingers, hand and wrist.

Hand and wrist ligaments

Ligaments are the other type of connective tissue in your hand. If tendons are like ropes, ligaments are more like thick rubber bands. Their main functions include:

• Helping your joints move smoothly.
• Protecting your joints from bending too far.
• Keeping your joints in the proper alignment.

Hand ligaments

There are lots of ligaments in your hand, including:

• Collateral ligaments: These ligaments run on the outside edges of your fingers and thumb. They protect your joints from moving too much from side to side.
• The volar plate: Volar plate ligaments connect your first two finger bones (phalanges) together on each finger. They run under your bones on the palmar side of your hand and keep your fingers from bending too far back when you extend them.
• Palmar fascia: Your palmar fascia is a thick, triangle-shaped ligament-like structure that runs under the skin of your palm. The narrow point of the triangle is at your wrist, and it gets wider toward the base of your fingers. It helps your hand keep its shape while you move it and prevents your skin from sliding when you’re holding something.

Wrist ligaments

Ligaments in your wrist include:

• Ulnocarpal and radiocarpal ligaments: Ligaments that stabilize your whole wrist while it moves.
• Collateral ligaments: These are the same ligaments as the ones in your hand. They run on both sides on the outside of your wrist and hold your wrist in place.
• Volar carpal ligaments: Ligaments that support and stabilize the bottom (palmar side) of your wrist.
• Dorsal radiocarpal ligaments: Ligaments that support and stabilize the back side of your wrist.

Hand and wrist arteries and blood vessels

Your hand and wrist get blood from two arteries. The radial artery runs along your radius (closer to your thumb). The ulnar artery runs along your ulna (closer to your pinkie finger). These arteries communicate with each other in “arches” that form in your hand. There’s a superficial and deep arch in your hand. Vessels branch off the arches and supply blood to your fingers.

Hand and wrist lymphatics

Your lymphatic system is a network of tissue, vessels and organs that collect excess plasma from your bloodstream and redistribute it throughout your body. Tiny capillaries in your hand capture extra plasma from the blood vessels that supply your hand and wrist. They connect to bigger lymph nodes and vessels in your upper arm