The perinychium includes the nail, the nailbed, and the surrounding tissue.
The paronychia is the lateral nail folds
The hyponychium is the palmar surface skin distal to the nail.
The lunula is that white semi-moon shaped proximal portion of the nail.
The sterile matrix is deep to the nail, adheres to it and is distal to the lunule.
The germinal portion is proximal to the matrix and is responsible for nail growth.
Lateral nail edge grows deep into nail wall → cycle of inflammation and hypertrophic granulation tissue can lead to abscess
Ingrown toenail
Foot and toe fractures
Nematocysts
Subtalar dislocation
Closed fist infection
Metatarsophalangeal joint sprain 
Weapon of mass destruction
Acute arterial ischemia