General Information and Skin Lesions

Question 1

What does the integumentary system comprise?

Answer 1

It consists of the skin and its adnexal structures which are hairs, nails, sebaceous and sweat glands.

Question 2

How large and thick is the skin?

Answer 2

The skin is the largest organ with an extension of 1.5 to 2 meters squared and is of variable thickness. The thickest portion is in the palms and soles, about 3 to 6 mm, and the thinnest is in the eyelids about 0.5 mm.

Question 3

What are the functions of the skin?

Answer 3

1. Physical barrier against microorganisms
2. Maintenance of fluid and electrolytes balance ->prevention of water loss
3. Thermoregulatory action -> mediated especially by sweat
4. Pigmentation to protect the body against the excessive exposure to UV rays
5. Immune function -> both in innate and adaptive immunity
6. Sensory receptor
7. Endocrine function -> it is responsible for the synthesis of Vitamin D

Question 4

What are the three main layers of the skin?

Answer 4

Epidermis, dermis and subcutaneous fat.

Question 5

What is the epidermis and how is it divided?

Answer 5

It is the most superficial layer and is composed of stratified squamous keratinized epithelium with neuroectodermic origin. It is divided in 5 layers which are starting from the deepest : stratum basale, spinosum, granulosum, lucidum, corneum.

Question 6

What is the stratum basale?

Answer 6

It is the deepest layer formed by a single row of cylindrical keratinocytes with a large and basophilic nucleus. These cells specifically arise here thanks to the germinative function of this layer and then in around 4 weeks, they move upwards reaching the stratum corneum from which they will be eliminated.

Question 7

What is the stratum spinosum?

Answer 7

It is the thickest one, so called due to the presence of thorn-like cellular appendages. Here the keratinocytes are connected by specific adhesion molecules called desmosomes; if there are auto-antibodies directed against these structures we will have auto-immune blistering disorders leading to the formation of bullae.

Question 8

What is the stratum granulosum?

Answer 8

It is the site of synthesis of profilaggrin which can be altered in case of genetic defects leading to a disease known as atopic dermatitis.

Question 9

What is stratum lucidum?

Answer 9

It is a layer of dead cells which is present only on the palms and soles.

Question 10

What is the stratum corneum?

Answer 10

the most external one, protects us from trauma. Keratinocytes lose their nucleus here.

Question 11

What are the four types of cells in the epidermis?

Answer 11

Keratinocytes, melanocytes, langerhans cells, merkel cells.

Question 12

What are keratinocytes?

Answer 12

Most prevalent and of neuroectodermic origin.

Question 13

What are melanocytes?

Answer 13

They are dendritic cells with neuroectodermic origin. Characterized by cytoplasmatic granules called melanosomes responsible for the synthesis of melanin which is then injected in the keratinocytes to protect the skin from UV radiation.

Question 14

What are langerhans cells?

Answer 14

They are dendritic cells, originating from bone
marrow, with specific MHC class II receptors needed to
present the antigen to CD4 lymphocytes.

Question 15

What are merkel cells?

Answer 15

They have a sensory function. There is a tumor known as merkeloma, which is so called even if it is not certain that it originates from these cells since it is a dermal tumor, while these merkel cells are only present at the level of epidermis.

Question 16

What is the dermal epidermal junction?

Answer 16

It is the connection between the epidermis and the dermis composed by : membrane of basal keratinocytes with anchoring filaments, lamina lucida and lamina densa.

Question 17

What is the dermis? What cells are present?

Answer 17

Dermis is the second main layer and is of mesodermal origin. It is organized in papillary dermis, reticular dermis and elastic fibers. There are several types of cells : fibroblasts, leukocytes, derma dendritic cells, mast cells. In addition there is ground substance.

Question 18

What are the papillary dermis, reticular dermis and elastic fibers.

Answer 18

Papillary dermis: the most superficial portion directly connected to the epidermis.

Reticular dermis: containing the adnexal structures, is made by collagen fibers (80-90%)

Elastic fibers which are important for mechanical support to the epidermis, distensibility and elasticity.

Question 19

What is the importance of ground substance?

Answer 19

Mostly synthesised by fibroblasts, which contains glycosaminoglycans such as hyaluronic acid, proteoglycans, and glycoproteins -> all responsible for dermal hydration.

Question 20

What is the pilosebaceus unit?

Answer 20

It includes the hair follicle, hair shaft and sebaceous gland. We can specifically distinguish:
Permanent superficial portion made by isthmus and infundibulum.
Non-permanent lower portion made by supra-bulbar part and bulb.

Question 21

How is the hair cycle composed?

Answer 21

1. Anagen: corresponds to the growing phase, in which
   the hair follicle is pushing out the hair and it lasts around 4 years.
2. Catagen: corresponds to the transition phase, which
   tends to last about 10 days.
3. Telogen: corresponds to the resting phase, that
   typically lasts around 3 months, during which new
   hairs start to form in follicles that lost their hair during
   the catagen phase.
4. Exogen: also known as the shedding phase, it’s considered an extension of the telogen stage during
   which the hair is shed from the scalp.

Question 22

What are the two main types of glands in the dermis?

Answer 22

1. Sebaceous glands: their duct terminates into the hair follicle, also responsible for the production of sebum (a useful substance in the formation of the hydrolipidic film of our skin).
2. Sweat glands can be further classified as:

Eccrine glands which found all over the body e.g., at the level of hands, feet, arms, legs and forehead and they are characterized by ducts directly pointing towards the epidermis.

Apocrine glands which only present in axillae, anal-genital area, eyelids, and mammary areola and generally end at the hair follicle. They are responsible for the secretion of a complex system of odorous chemicals known as pheromones.

Question 23

What is subcutaneous fat? What is its role?

Answer 23

It is made by adipose cells, and it represents a sort of buffering between the skin and the underlying musculoskeletal system. It also plays an important role in mechanical protection of internal organs, thermal insulation and energy reserve.

Question 24

What is the difference between primary and secondary skin lesions?

Answer 24

Elementary or Primary lesions are those that arise de novo and therefore they are the most characteristic of the disease processes. While Secondary lesions are made by the modification of primary ones either by the individual or through the natural evolution of the lesion in the environment.

Question 25

What are some examples of primary lesions and secondary lesions?

Answer 25

Primary : Macules, papules, wheals, vesicles, bulla, pustule and nodule.

Secondary : Crusts, erosions, scales, fissures, sclerosis, atrophy and cheloids.

Question 26

What are macules?

Answer 26

It is a flat and non-palpable lesion measuring less than 1
cm in diameter; it differs in colour from normal skin and according to this it can be defined as :

a) Erythematous if it is red and it is formed following vasodilation or extravasation of red blood cells.

b) Hypopigmented if it is white.

c) Hyperpigmented if it is black due to an alteration of melanin.

Question 27

How can we discriminate between a red macule due to
extravasation of RBCs and erythema due to vasodilation?

Answer 27

We apply a method called diascopy, which consists in applying a little pressure with a finger or glass slide on the macula observing its color changes: the purpura does not disappear, while the erythema (rosacea) disappears because we remove the blood from dilated vessels and the skin becomes white.

Question 28

What is papule?

Answer 28

Primary lesion. It is an elevated, circumscribed, and solid lesion measuring less than 1 cm in diameter which has a variable shape and color. It can be epidermal if consists only in the thickness of the epidermis, dermal in case of dermal infiltrate or dermo-epidermal if it comprises both layers. Lichen ruber planus is the typical common disease in which we will find this type of lesion. When more papules merge, they form a specific type of secondary lesion called plaque.

Question 29

What is a wheal?

Answer 29

Primary lesion. It is a circumscribed and solid lesion measuring less than 1 cm in diameter which has variable shape and size characterized by extreme transience. It is typical of urticaria, and it is caused by capillary vasodilation and edema of the papillary and mid dermis.

Question 30

What is a vesicle?

Answer 30

Primary lesion. It is a rounded collection of intra or subepidermal serous fluid measuring less than 1 cm in diameter. According to its genesis it can be defined as :

Eczematous, if it arises from a histopathologic phenomenon known as spongiosis, consisting in accumulation of fluid (exudate) coming from the dermis and directed into the intercellular spaces of keratinocytes of epidermis.

Herpetic due to herpes infection which causes a direct damage of keratinocytes through the so called ‘ballooning degeneration’.

Question 31

What is a bulla?

Answer 31

Primary lesion. It is a collection of serous fluid or blood serum at an intra epidermal or dermo epidermal site with dimensions greater than 1 cm. The intra epidermal lesion is typical of pemphigus while the dermo epidermal is more common in pemphigoid.

Question 32

What is a pustule?

Answer 32

Primary lesion. It is a collection of purulent intra epidermal exudate made of neutrophils. It can be defined as follicular if it is at the level of the pilo sebaceous follicle or non follicle. It can have both microbial or amicrobial causative agent and its rupture can cause the formation of crusts.

Question 33

What is a nodule?

Answer 33

Primary lesion. It is a circumscribed lesion considered a large papule since it measure more than 1 cm in diameter. Most likely involved the dermis and subcutaneous fat and is caused by either inflammatory or tumoral processes.

Question 34

What are crusts?

Answer 34

Secondary lesions. They are secondary to the rupture of the blisters, pustules and to the continuous evolution of the skin such as erosions, ulcers and fissures, the dried exudate can be of composed of blood, serum or pus.

Question 35

What are scales?

Answer 35

Secondary lesion. They are due to an increased shedding or accumulation of keratinocytes from the stratum corneum as result of abnormal keratinization and exfoliation. This is the type of lesion that generally occurs in case of psoriasis in which an alteration in the duration of keratinization occurs. We distinguish different types of scales: pityriasiform small and delicate, psoriaform thick and multi-layered and lamellar or icthyosiform with a fish-like appearance.

Question 36

What are erosions?

Answer 36

Secondary lesions. Breakdown of only epidermis and more superficial layers of the skin. Generally follows the break fo vesico pustular bullous lesions.

Question 37

What are ulcers?

Answer 37

Secondary lesion. They consist in a break of the skin involving the epidermis, dermis and subcutaneous fat. Secondary to traumas, tumoral processes or inflammatory processes.

Question 38

What are fissures?

Answer 38

Secondary lesion. They are linear and often painful breaks of the skin within the epidermis or dermis due to excessively dry skin or thickness of skin.

Question 39

What is sclerosis?

Answer 39

Secondary lesion. It is a circumscribed or diffused alteration of dermis and sometimes of the subcutaneous fat due to induration of collagen, with a porcelain-like appearance of the skin. Scleroderma, as systemic disease involving the
internal organs and blood vessels, is a typical situation during which we can find this type of lesion; the same is true also for morphea the inflammatory disease involving only the skin.

Question 40

What is atrophy?

Answer 40

Secondary lesion. Limited or widespread reductions in skin thickness which are very difficult to recover.

Question 41

What are cheloids?

Answer 41

Secondary lesions. They are hypertrophic scars due to sclerosis of the skin. If we remove them there is immediately the formation of a new cheloid more extended than the previous one.

Question 42

What is a clinical approach like in dermatology?

Answer 42

Initial approach: collection of a detailed history of the current skin complaint, medication history and a full body skin examination.
• History of the skin lesion/eruption: time of onset, duration, location, evolution, and symptoms. We must collect additional info on family history, occupational exposures, comorbidities, social and psychologic factors.
• Physical examination: includes visual inspection and palpation of the skin through which we can describe the morphology, arrangement, and distribution of the lesions.
• Wood’s light examination: under this specific light, variations in epidermal pigmentation are more apparent than under visible light and some microorganisms may emit a fluorescence
• Dermoscopy: it is the specific skin examination technique performed with a handheld instrument called dermatoscope, a lens that magnifies the lesion, allowing us to visualize skin structures not visible to the naked eye.

Question 43

What is a verruca?

Answer 43

It is a benign cutaneous squamous-proliferative lesion of the skin, commonly HPV induced. Common sites of occurrence are hands and fingers, but also elbows, knees ad other locations. The HPVs involved are the squamous type of HPV, cutaneous type. This lesion may undergo spontaneous involution. It is rarely associated to other lesions, it does not evolve into SCC.