Skin Structure, Skin Permeation and Fick's first law

Question 1

What substances does the skin synthesize?

Answer 1

Synthesizes vitamin D, sex hormones and pheromones

Question 2

What is the subcutaneous layer of the skin?

Answer 2

The layer of fatty tissue located below the dermis.
Cells synthesize and store fat as energy reserve, as insulation from
extreme temperatures, and as buffer against trauma.
It provides body contours – attractive curves or unsightly bulges.

Question 3

What is the dermis layer of the skin and what is it comprised of?

Answer 3

1. Dermis is the region between the epidermis and hypodermis.
2. It is made up of a dense network of structural collagen and elastin fibres (connective tissues).
3. It consists of blood vessels, network of sensory nerves (pressure, temperature, pain), hairs, hair erector muscles, sebaceous glands and sweat glands.

Question 4

What is the outermost layer of the epidermis called?

Answer 4

Stratum corneum (SC) or horny layer is the outermost layer of the epidermis.

Question 5

What is the stratum corneum composed of?

Answer 5

SC layer is composed of corneocytes (flattened dead cells) cemented by SC lipids → brick and cement morphology (aka the brick-and-mortar model).

Question 6

What are the stratum corneum lipids composed of?

Answer 6

Ceramides (50%)
Cholesterol (25%)
Fatty acids (10 to 20%)
They are filled with keratin filaments
They contain natural moisturizing factors (NMFs) acting as a water reservoir, retaining moisture in SC layer, keeping the skin supple.