The Skin – Structure, Functions & Healing

30 question-and-answer flashcards covering structure, functions, cells, disorders, and accessory components of the skin, aligned with the lecture content.

What are the three primary layers of the skin?

Epidermis, Dermis, and Hypodermis.

List five principal functions of the skin mentioned in the lecture.

Sensory reception; Protection from impacts, chemicals, and pathogens; Thermoregulation (heat retention or loss); Synthesis and storage of nutrients (e.g., vitamin D3, lipids); Excretion and secretion of salts, water, and wastes.

Which epidermal layer contains epidermal ridges that bind to dermal papillae?

The Stratum Basale (bottom layer of the epidermis).

Which epidermal cells produce a fibrous protein that provides structure to the skin, and what is that protein called?

Keratinocytes produce keratin.

Which immune-related cells patrol the epidermis and where are they originally produced?

Langerhans (dendritic) cells; they are macrophages produced in the bone marrow.

Which cells in the epidermis synthesize the pigment responsible for skin colour?

Melanocytes synthesize melanin.

Which specialized epidermal cells are sensitive to light touch?

Merkel cells.

What structural feature of the epidermis is responsible for fingerprints and increased surface grip?

Unique patterns of epidermal ridges formed by the up-and-down border between epidermis and dermis.

Briefly explain the pathological process behind psoriasis.

Basal cells in the stratum basale divide almost daily instead of every ~20 days, causing excess keratin (hyperkeratosis), flaky skin layers that can’t be shed fast enough, and possible pus from immune responses.

Which vitamin is produced when epidermal cells are exposed to UV light, and into which hormone is it converted to enable calcium and phosphorus absorption?

Vitamin D3; converted by the liver into calcitriol.

Name the two sub-layers of the dermis and the dominant connective tissue in each.

Papillary layer – areolar connective tissue; Reticular layer – dense irregular connective tissue.

What is dermatitis, and which dermal layer does it primarily involve?

An inflammation of the skin, mainly involving the papillary layer of the dermis.

Describe the basic hair growth cycle covered in the lecture.

Hair grows for about 2–5 years at ~0.3 mm/day, may become inactive for another 3–5 years, after which new growth pushes out the old hair.

Which tiny muscle makes hair stand erect to trap warm air, aiding insulation?

The arrector pili muscle.

What oily substance do sebaceous glands secrete, and list two of its functions.

Sebum; it waterproofs/conditions skin, lubricates hair, and is bactericidal.

Explain how acne forms according to the notes.

During hormonal changes, excess sebum blocks ducts; trapped secretions foster bacterial growth, leading to inflammation.

State the primary function of sweat and its main composition.

Thermoregulation (cooling); sweat is ~99 % water with small amounts of salts, nutrients, and urea.

Why does body odour develop despite sweat being mostly water?

Bacteria multiply in and metabolize sweat, producing odorous by-products.

List three key roles of adipose tissue in the hypodermis.

Reduces heat loss, serves as an energy reserve, and acts as a shock absorber.

Why is the hypodermis a preferred site for hypodermic injections?

It is elastic, contains few vital organs, and easily accommodates injected fluids.

How do epidermal ridges and dermal papillae improve nutrient delivery to the epidermis?

Their interlocking folds increase surface area, enhancing diffusion of nutrients and oxygen from dermal capillaries.

Identify the connective tissue type that predominates in the papillary dermis.

Areolar connective tissue.

Approximately how thick is the stratum corneum, and what type of cells compose it?

Roughly 0.08 mm thick; composed of 4–5 layers of dead keratinocytes rich in keratin.

Roughly how many sweat glands are found per square centimetre of skin?

About 500 sweat glands per cm².

Up to how many Langerhans cells can be found per square millimetre of epidermis?

Up to about 800 Langerhans cells per mm².

For how long does a typical human hair remain in an active growth phase?

Approximately 2–5 years.

In normal skin, how often do basal cells divide compared to their rate in psoriasis?

Normally once every ~20 days; in psoriasis nearly every day.

What is the role of calcitriol formed from vitamin D3?

Calcitriol enables the intestines to absorb calcium and phosphorus, supporting healthy bones.

Thermoregulation by the skin involves what two opposite processes?

Conserving heat and losing heat to maintain body temperature.

Besides water and salts, name one waste product excreted through sweat.

Urea.