skin, body, grain, texture, disposition
膚 centers on the physical surface and substance of a living thing: skin, body, and the texture or grain of that surface. The disposition sense extends this idea to one's innate bodily or temperamental makeup.
skin
unwounded skin
shiitake dermatitis
inflamed skin
atopic dermatitis
allergen skin test
exfoliative dermatitis; erythroderma
completely; thoroughly; decisively; unsparingly; beyond recognition; until there's no untouched (undamaged) part
cradle cap
Japanese Society for Dermatologic Surgery; JSDS
cutaneous candidiasis
dermatome
cutaneous respiration
flap; skin flap
cutaneous sensation
skin ulcer
dermatitis
cutaneous anthrax
skin disease
skin cancer
膚 combines 虍 (tiger stripes) with 胃 (stomach), originally referring to the skin or surface of the body, possibly by analogy to the striped surface of a tiger. The exact historical development is uncertain, but the association with skin is well established.
The outer enclosure 虍 suggests tiger stripes, and inside is 胃 (stomach). Imagine a tiger's striped skin stretched over a belly: 膚 is the skin that covers the body.
For フ, picture a full-body skin suit: full -> フ, and the suit covers every inch of your skin.