Dermatology

Question 1

Explain the steps in a dermatological examination

Answer 1

• Adequate exposure and good lighting are essential – dermatology is a visual specialty!
• Examination should include hair/scalp, mucous membranes and nails
• Comment on morphology i.e. how individual lesions look and distribution/ sites involved
• Palpate!
• Examine other systems if appropriate e.g. Joints, lymph nodes

Question 2

What are the 3 major events that lead to inflammation

Answer 2

– Vasodilation (causing rubor and calor)
– Increased microvascular permeability resulting
in production of a protein-rich exudate (causing tumor)
– Influx of leukocytes

Question 3

What are the 6 signs of inflammation

Answer 3

Pain (dolor)
Heat (calor)
Redness(rubor)
Swelling (tumor)
Loss of function (functio laesa)
Itch

Question 4

What is toxic epidermal necrolysis?

Answer 4

• Severe muco-cutaneous drug reaction
• Full thickness epidermal damage
• Skin separated to leave raw, oozing dermis
• Life threatening, high mortality

Question 5

Name some basic functions of skin

Answer 5

Barrier from external insults - infection, physical, chemical 
Physiological - electrolyte and fluid balance 
Temperature regulation 
Sensation 
Immunological 
Vitamin D synthesis 
Psychosocial/cosmetic
Excretion and secretion 
Endocrine
Thermal regulation

Question 6

Describe the basic structure of skin

Answer 6

◦ Outermost portion = epidermis, 4 specialised cells
‣ Keratinocytes (secrete keratin), melanocytes, langerhan cells, merkel cells
◦ Middle section = dermis
‣ Blood vessels, excretory glands such as sebaceous oil gland and sweat Gand
◦ Hypodermis aka subcutaneous layer
‣ Adipose cells, macrophages

Question 7

How does the skin protect from physical damage?

Answer 7

◦ The skin consists of strong and elastic protein fibres (collagen, keratin, and elastin) that protect the body from physical and mechanical forces. This ensures that the internal organs are not damaged
‣ Keratin makes skin impermeable to water
‣ Collagen and elastin (in dermis and hypodermis) along with keratin give skin elasticity, allows skin to resist physical as well as mechanical pressures and forces
‣ Ensures internal organs are well protected

Question 8

Aside from physical damage, what else does the skin protect from?

Answer 8

‣ Excessive UV radiation (uv used to synthesise vitamin D a hormone to regulate calcium and phosphate)
• UV is ionising radiation, can damage DNA etc, lead to cancer
• Melanocytes release melanin absorbs UV radiation to protect skin
‣ Bacterial and viral micro-organisms
• Physical barrier
‣ Dehydration
‣ Dangerous chemicals
• If harmful molecule gets into skin, skin blocks it from getting in rest of body

Question 9

How the skin sense?

Answer 9

◦ The skin contains somatic sensory receptors that aid in sensations. It also contains cells called Merkel cells that are believed to be involved in sensation. The skin contains pressure receptors, light receptors, pain receptors, thermal receptors, among others.

Question 10

How does the skin insulate?

Answer 10

◦ Subcutaneous layer contains adipose cells to create layer of insulation
◦ Every exothermic process in the body produces excessive energy (heat) that must be dissipated by the body to prevent overheating. Heat needs to be removed or else core temp increases, heat carried in blood.
◦ The blood vessels that run in the dermis of the skin can expel this heat via radiation. The skin an also expel heat via the endothermic process of evaporation. The skin can also prevent heat loss by directing blood flow away from the skin
◦ (Homeostasis stuff)
◦ Radiation, sweating, vasodilation, shunt vessel

Question 11

Describe the excretion and secretion that occurs in the skin

Answer 11

◦ The skin is an excretion organ. It can excrete water to the skins surface via diffusion. Waste products such as urea, salts such as sodium or water can also be excreted via sweating
◦ Sweat glands produce sweat and secrete/excrete via sweat pores and hear rising from blood vessels vaporises it
◦ Transempidermal water loss - water diffuses across upper portion of skin, water lost through process of diffision - DIFFERENT FROM DIFFUSION

Question 12

Describe the immunological function of the skin

Answer 12

◦ Langerhans cells of the epidermis can interact with T-calls to help protect the body from bacterial agents. Phagocytosis cells in the hypodermics can engulf bacterial cells
‣ Antigen presenting cells found in all layers but mainly…..
◦ Stratus spinoum (prickly) langerhan cells present here
◦ Subcutaneous layer contains macrophages to engulf cells

Question 13

Describe the endocrine function of the skin

Answer 13

◦ Cells in the epidermis can produce vitamin D3 (cholecalciferol) by using the energy stored in UV radiation. This can be ultimately activated to the hormone calcitreol in the kidneys
◦ Cholecalciferol an inactive from of vit d3. Travels into liver and transformed into calcideiol and then travels to kidneys, becomes calcitreol, final form

Question 14

How does the skin grow?

Answer 14

Skin can expand due to elastin fibres - skin grows as the organism grows

Question 15

How did different skin colours evolve?

Answer 15

• 2 mil to 1.5 mil years ago everyone darkly pigmented
• Early days o evolution, high levels of UV rad
◦ UVC blocked by atmosphere
◦ UVA and UVB enter
◦ UVB destructive but catalyses the production of vitamin D in the skin, for bones. And health of immune system etc
◦ Melanin = natural sunscreen, protects against DNA damage and breakdown of folate
‣ Present in many different organisms
‣ Around a billion years
‣ In our earliest ancestors in Africa to be a natural sunscreen to protect against UV
‣ Protect against damage o folate which fuels cell production and reproduction
◦ humans dispersed away from equator
◦ Colder conditions, less intense UV
‣ UVB missed (dissipated through atmosphere) but only a dose of UVA
‣ UVA has no ability to make vitamin D in skin
‣ People in northern hemisphere - no vitamin D for most of the year
‣ In order to ensure health, they lost pigmentation to maximise vitamin D production

Question 16

What are melanocytes?

Answer 16

• Melanocytes to melanoma
◦ Melanocytes are cells that produce melanin,, a brown-black pigment that determines colour of skin hair and eyes
◦ Guards against damaging effects of skin
◦ At epidermal-dermal junction
◦ Regular extensions called denstrites
◦ Formation occur in cell body

Question 17

Describe the steps from melanocyte to melanoma

Answer 17

‣ In membrane bound organelle called melanosome
‣ Melanosome transported by microtubules to surface of melanocyte to a keratinocyte
‣ Melanosomes released into matrix of cytoplasm of keratinocyte, accumulate above nucleus
‣ Protect nuclei of dividing cells from UV
‣ Heritable predisposition and genetic mutation increase the risk of malignant melanoma
‣ UV directly absorbed by DNA - major risk factor for skin cancers
‣ When UV absorbed by double bond in thymine, the thymine opens allowing base to react with nearby molecules
‣ If T next to another T they join to dorm a thymine dimer - covalent bonding
‣ 2 new bonds with adjacent bases forming a 4 base ring
‣ Structural consequences include distortion in the helix and kink in DNA strand
‣ If UV damage not corrected by molecular repair mechanisms then DNA transcription and replication are blocked, may be permanently mutated
‣ Genetic mutations are associated with histology changes along a continuum that may culminate invasive malignancy
‣ The change from a melanocyte to melanoma may involve several histologic changes such as atypical/says plastic nevus of varying severity or melanoma in situ and invasive melanoma
‣ Melanoma diagnosed in radial growth phase have excellent prognosis
‣ No cure for late stage melanoma
‣ Early detection important for reducing morbidity and mortality

Question 18

What is psoriasis?

Answer 18

Psoriasis is a skin condition that causes red, flaky, crusty patches of skin covered with silvery scales.
These patches normally appear on your elbows, knees, scalp and lower back, but can appear anywhere on your body. Most people are only affected with small patches. In some cases, the patches can be itchy or sore.
Psoriasis affects around 2% of people in the UK. It can start at any age, but most often develops in adults under 35 years old. The condition affects men and women equally.
The severity of psoriasis varies greatly from person to person. For some people it’s just a minor irritation, but for others it can have a major impact on their quality of life.
Psoriasis is a long-lasting (chronic) disease that usually involves periods when you have no symptoms or mild symptoms, followed by periods when symptoms are more severe.
Read more about the symptoms of psoriasis.

Question 19

Why does psoriasis happen?

Answer 19

People with psoriasis have an increased production of skin cells.
Skin cells are normally made and replaced every three to four weeks, but in psoriasis this process only lasts about three to seven days. The resulting build-up of skin cells is what creates the patches associated with psoriasis.
Although the process isn’t fully understood, it’s thought to be related to a problem with the immune system. The immune system is your body’s defence against disease and infection, but for people with psoriasis, it attacks healthy skin cells by mistake.
Psoriasis can run in families, although the exact role that genetics plays in causing psoriasis is unclear.
Many people’s psoriasis symptoms start or become worse because of a certain event, known as a “trigger”. Possible triggers of psoriasis include an injury to your skin, throat infections and using certain medicines.

Question 20

What is atopic eczema

Answer 20

Atopic eczema (atopic dermatitis) is the most common form of eczema, a condition that causes the skin to become itchy, red, dry and cracked.
Atopic eczema is more common in children, often developing before their first birthday. However, it may also develop for the first time in adults.
It’s usually a long-term (chronic) condition, although it can improve significantly, or even clear completely, in some children as they get older.
Symptoms of atopic eczema
Atopic eczema causes the skin to become itchy, dry, cracked, sore and red. Some people only have small patches of dry skin, but others may experience widespread red, inflamed skin all over the body.
Although atopic eczema can affect any part of the body, it most often affects the hands, insides of the elbows, backs of the knees and the face and scalp in children.
People with atopic eczema usually have periods when symptoms are less noticeable, as well as periods when symptoms become more severe (flare-ups).