Session 11 ILOs - Skin structure and Function and Dermatology

Question 1

Describe the macroscopic structure of human skin (i.e. as determined by the naked eye)

Answer 1

3 layers of the skin:

1. Epidermis (containing layers within it)
   - Has 4 layers in thin skin and 5 layers in thick skin (includes stratum leucidum)
   - Held together vertically by desmosomes and held together laterally by adherens junctions
   - NO blood vessels
2. Dermis
   - Has 2 layers (papillary and reticular)
   - Has dermal papillae (nipple structures)
3. Hypodermis (also known as the subcutaneous layer)
   - Mainly adipose tissue
   - Loose connective tissue containing fibroblasts/macrophages/fibres

Question 2

Describe the different regions of the epidermis:

• Horny layer (stratum corneum)
• Transparent layer (stratum lucidum)
• Granular layer (stratum granulosum)
• Prickle cell layer (stratum spinosum)
• Basal layer (stratum basale)

Answer 2

Horny layer (stratum corneum)

• Thick layer of squares (dead keratinocytes)
• Continuously shed
• Thicker on palms and soles

Transparent layer (Stratum lucidum)

• Only found on palms and soles (only in THICK skin areas)
• Transparent layer (smooth)

Granular layer (stratum granulosum)

• Stratified squamous epithelium
• Lamellar granules (layers of granules)
• Tonofibrils (keratin and keratohyalin granules - produced by the lamellar bodies)
• Increased golgi apparatus

Prickle cell layer (stratum spinosum)

• Cuboidal epithelium in 3 layers
• Producers of lamellar bodies

Basal layer (stratum basale)

• Tall columnar cells
• Make keratin filaments / constantly renew kartainocytes by division
• House melanocytes

Question 3

Describe the process of keratinocyte differentiation

Answer 3

• Basal cell divides and when it divides, it produces spinous cells
• The spinous cells start to produce laminar bodies (keratin-forming factories) and so kertain is packaged together on the RER
• As this happens, the spinous cell turns into a granular cell which then starts to produce golgi apparatus and packages all the keratohyalin into granules
• It puts these granules outside the granular cell and this is why we have the translucent layer
• As they die off, they become squames (outer layer)

Question 4

Describe the structure and functions of skin appendages: e.g. hair/hair follicles, sebaceous glands, sweat glands and nails

Answer 4

Hair:
Structure: 3 types - lanugo, velds or terminal
Function: thermoregulation, sexual attraction, sensing, protection

Sebaceous glands:
Structure: Exocrine gland in the skin that opens into a hair follicle
Function: Secretes oily sebum in fight or flight response and keeps skin soft and pliable

Sweat glands:
Structure: Small, coiled, simple tubular glands
Function: Thermoregulation

Nails:
Structure: Comprised solely of alpha-keratin (nail plate, nail matrix and the nail bed) and has no nerves
Function: Protection, enhances fine movements, enhances the sensitivity of the fingertip and acts as a tool

Question 5

Describe the contents and function of the hypodermis and immediate subcutaneous fat (adipose tissue)

Answer 5

Contents:
The hypodermic layer is mainly an adipose tissue layer (which contains neurovascular bundles and lymphatics)

Function: Insulation, shock absorption and the fat cells store nutrients and energy for the underlying muscle

Question 6

Differentiate between thick (non-hairy) and thin (hairy) skin

Answer 6

Thick layer has no hair follicles (and no arrestor pili muscles), whereas the thin layer has hair follicles

Thick layer has no sebaceous glands, whereas the thin layer has sebaceous glands

Thick layer has pronounced ridges and furrows (fingerprint) but thin layer only has small ridges

Thick layer has regular dermal papillae, whereas the thin layer has an irregular dermal papillae

Thick layer has 5 layers (stratum luecium) but the thin layer only has 4 layers

Question 7

Describe the structure and key components of taking a Dermatology history and in performing a clinical examination

Answer 7

HISTORY:

• Symptoms e.g. site of onset and evolution, distribution, asymmetrical or symmetrical etc.
• Exacerbating and relieving factors
• Past medical history
• Personal and family of skin disease including atopy
• Thorough drug history including timeline and non-prescribed treatments (over the counter)
• Social, occupational, travel, sexual history
• Psychosocial impact

EXAMINATION:

• Hair/scalp, mucous membranes and nails
• Comment on morphology i.e. how do individual lesions look and their distribution
• Palpate
• Examine other systems if appropriate e.g. joints (which are affected in psoriasis)

Question 8

Briefly describe what eczema is, how it is caused and how it impacts on quality of life and creates a psychosocial burden

Answer 8

ECZEMA:
Eczema is the name for a group of conditions that cause the skin to become itchy, inflamed, or have a rash-like appearance

CAUSE:
The exact cause of atopic eczema is unknown, but it’s clear it is not down to one single thing. Atopic eczema often occurs in people who get allergies e.g. hay fever

IMPACT ON LIFE:
Eczema can be extremely uncomfortable and painful at times. For those with moderate to severe eczema, it hugely disturbs their sleep and affects their performance of daily activities, e.g. sports or school.
Study has shown that those with eczema have a worse quality of life than several other common chronic illnesses including heart disease, diabetes and high blood pressure.

Question 9

List the 6 Cardinal signs of skin inflammation

Answer 9

1. Rubor (redness)
2. Tubor (swelling)
3. Calor (heat)
4. Dolor (pain)
5. Function laesa (loss of function)
6. Pruritis (itch)