What do the following words have in common?

PINS
GUN
INK
MAP
VEIL
SON
BOWL
LEAN

HINTS:
#1: Each word is missing a letter.
#2: With the missing letter added, the words can be anagrammed.
#3: The anagrammed words share a common theme.

Answer:

SPINE
LUNG
SKIN
PALM
LIVER
NOSE
ELBOW
ANKLE