Skin Anatomy

Question 1

1-What are the 5 overarching roles of the skin?

Answer 1

1-a) Protection from the environment e.g abrasions, fluid loss, harmful substances, UV radiation and microorganisms

b) Containment for body structures, preventing dehydration
c) Heat Regulation through the evaporation of sweat and/or the dilation or constriction of superficial blood vessels
d) Sensation via superficial nerves
e) Synthesis and storage or Vitamin D

Question 2

1-What are the three layers of the skin?

2-Describe the layers that make up the epidermis?

Answer 2

1-Epidermis, Dermis and Subcutaneous Tissue Layer

2-Superficial keratinised layer, which has a tough, horny protective outer surface; and the Basal layer, which is the regenerative pigmented layer.

NB: The entire epidermis is avascular, with no blood vessels or lymphatics. It is nourished by the underlying vascular Dermis.

Question 3

1-What tissues primarily make up the dermal layer and what role do they provide?

2-What determines the direction of a skin wrinkle?

3-What structures are contained inside the dermis?

Answer 3

1-Dermis has a dense layer of interlacing collagen and elastic fibers. These fibers provide skin tone and account for the strength and toughness of skin.

2-The predominant pattern of collagen fibers determines the characteristic tension/wrinkle lines on the skin.

3-Hair follicles, attached to smooth arrector muscles and sebaceous glands; sweat glands, arterioles.

NB: Contraction of the arrector muscles of hairs causes goosebumps

Question 4

1-What layer is located underneath the Dermis?

2-What is this layer composed of and what does is contain?

Answer 4

1-Subcutaneous Tissue (superficial fascia, just above the deep fascia)

2-Composed mostly of loose connective tissue and adipose tissue. It contains sweat glands, blood vessels, lymphatic vessels, cutaneous nerves and skin ligaments (L. retinacula cutis).

NB: Skin ligaments extend from the deep fascia to the dermal skin layer

Question 5

1-How much insensible water loss occurs across the skin on average?

2-What skin characteristics reduce this water loss?

Answer 5

1-Average water loss across the skin is 300-400ml p/day.

2-Cholesterol filled stratum corneum (epidermal) layer of the skin reduces this water loss and makes the skin highly resistant to water soluble substances. When this layer becomes denuded e.g. with burns, the rate of evaporation can increase as much as 10x

Question 6

1-How is vitamin D formed in the skin?

2-What is the effect of Testosterone on the skin?

3-What is the effect of oestrogens on the skin?

Answer 6

1-Vitamin D3 (cholecalciferol) is formed in the skin as a result of irradiation of 7-dehydrocholesterol, a substance normally in the skin, by UV rays from the sun.

2-Testosterone causes the thickness of the skin on the entire body to increase. It also increases the rate of secretion by the body’s sebaceous glands, which is particularly evident on the fave when it causes acne. After several years of testosterone secretion the skin adapts to it, allowing it to overcome the acne.

3-Oestrogens cause the skin to develop a soft and smooth texture and can cause the skin to become more vascular.