Arm and hand skeleton (humerus, radius/ulna, hand)
Use the humerus, radius, ulna, and hand bones to place arm joints, rotate the forearm, and structure fingers from different angles.
What it is
The upper limb has one upper-arm bone, the humerus, two forearm bones, the radius and ulna, and small wrist and hand bones. You can sketch this structure before adding muscles, skin, or clothing.
Place the humerus from the shoulder to the elbow. From elbow to wrist, the radius and ulna cross and uncross during pronation and supination, turning the palm down or up. Their positions affect the forearm contour.
Treat the wrist as a solid block that leads into five rays: an angled thumb metacarpal and four finger metacarpals. The palm has depth, and each finger has three small bones connected to the palm block.
Why it matters
A usable mental skeleton helps you place elbows, wrists, knuckles, and finger joints. Weak control can make arms bend in the wrong place, forearms twist without a joint, and hands flatten into simple shapes.
You can check it when
- ✓Draw the humerus, radius and ulna, hand block, and finger segments from multiple angles without reference.
- ✓Place the elbow and wrist at the ends of the correct arm segments, and make the arm bend at those joints.
- ✓Rotate the forearm with the palm up, palm down, and thumb up while keeping the wrist, thumb base, and knuckles aligned.
- ✓Build hands with a thick wrist block, a palm with length and an arch, and fingers divided into three segments.