by Daniel Laberge
Human grooming

The dermis

 Just below the epidermis lies the dermis.

SKIN

Skin layers; the dermis

The dermis may fold over on itself several times, as you can see on your face.

Old and new dermis theory

New dermis theory

The dermis is folded

Vertical folds

Horizontal folds

• Langer's lines

They are folds, not lines

Langer's lines; an erroneous theory

«Langer's lines were historically defined by the direction in which the skin of a human cadaver will split when struck with a spike».
                      Source; Wikipedia

«Spaltrichtungen» by K. Langer

Dr. Fr. Kopsch: Rauber's Lehrbuch der  Anatomie des Menschen. p. 825

Langer's lines

Langer's lines

Grooming proves that the lines are folds

Not only are they folds, but they can be unfolded

Erroneous maps and illustrations of folds

Taken from:
Journal of Dermatological Research
Biodynamic Excisional Skin Tension (BEST) Lines: Revisiting Langer’s Lines, Skin Biomechanics, Current Concepts in Cutaneous Surgery, and the (lack of) Science behind Skin Lines used for Surgical Excisions

Taken from:
The Open Access Atlas of Otolaryngology, Head & Neck Operative Surgery
BIOPSY OF HEAD & NECK TUMOURS & CERVICAL LYMPH NODES
Johan Fagan, Kathy Taylor & Ellen Bolding

• Sebum glands

Why do you have sebum glands?

Sebum is a lubricant for grooming

Sebum glands are attached to hair follicles;
so flexing the shaft releases the lubricant

Nail/hair/sebum interaction

As your fingertip curves the hair,

it forces out some sebum.

Sebum glands expelling their content into folds

Sebum glands pouring their content in a fold

Many glands ejecting their sebum inside a fold.

Sebum glands almost everywhere

• Skin pores

Are you looking at a pore or at the opening of a fold crossing?

• Fingerprints

Papillary ridges and fingerprints

• Skin orientation

Your skin is vertical

• Trapped hair

Imprisoned hair follicles and muscles

Traditional dermis theory

Dermis components

• Blood vessels

• Free nerve endings

• Hair follicles with sebum glands

• Sweat glands

• Specialized receptors

The hypodermis or subcutis

 Just below the dermis lies the hypodermis.

SKIN

Skin layers; the hypodermis