Humerus (paired)
Your Humerus is your upper arm bone. The Humerus articulates with your scapula (shoulder blade) and with your ulna and radius (your lower arm bones).
Ulna (paired)
Your ulna is one of your lower arm bones, the radius being the other. It sits next to your radius, and it articulates with your humerus, and with your wrist bones in your hand. When you stand in a correct anatomical position, (with your arms down and your palms facing forward), your ulna is closest to your pinky finger.
Radius (paired)
Your radius is your other bone that makes up your lower arm. It sits alongside of your ulna and articulates with your humerus and with two of your carpal bones (the navicular and the lunate). If you stand in a correct anatomical position, your radius is closest to your thumb. When your turn your arm around, your radius is the only lower arm bone that actually rotates. Your ulna does not. That's why, if you look at the diagram, you can see that the head is rounded, so it can rotate.
Hand Bones
There are 27 bones in each of your hands.
8 carpal bones; 5 metacarpal bones; and 14 phalanges.
Carpal Bones
Your carpal bones are your wrist bones. There are 8 carpal bones in each hand.
Metacarpal Bones
You have 5 metacarpal bones in each hand; they are the long bones of the hand.
Phalanges
There are 14 phalanges in each of your hands. There are 3 in each finger, and 2 in the thumb.
