DERM 01: Intro to Derm Flashcards
1
Q
What are the 3 main layers of the skin?
A
- epidermis
- dermis
- subcutaneous tissue (hypodermis)
2
Q
What are the 5 layers of the epidermis?
A
- stratum corneum
- stratum lucidum
- stratum granulosum
- stratum spinosum
- stratum basale
3
Q
What is the stratum corneum?
- What is it made of?
- Where is it NOT present?
- What is its function?
A
outermost and non-viable layer of epidermis
- made of dead skin cells (corneocytes)
- not present in mucosal tissue
- semipermeable barrier – serves as barrier with ‘bricks’ (stacked corneocytes) and ‘mortar’ (lipid substances including ceramides, cholesterol, and fatty acids)
4
Q
Where is the stratum lucidum present?
A
only in palms and soles (thick skin)
5
Q
Stratum Granulosum
- What is its function?
- Where is it not present?
A
- produces corneocytes, lipids, and proteins for stratum corneum
- not present in mucosal tissue
6
Q
What is the stratum spinosum?
A
thickest layer of epidermis
7
Q
What is the stratum basale?
- Where is it?
- What is it made of?
A
innermost layer of epidermis
- located above basement membrane
- 10% is stem cells that produce the rest of the keratinocytes
8
Q
What are the 4 major cell types of the epidermis?
A
- keratinocytes – 99% of cells in epidermis
- melanocytes – 10% of cells in stratum basale layer
- langerhans cells – 3-5% of cells in stratum spinosum
- merkel cells – located just above basal layer
9
Q
What are keratinocytes?
- What is their function?
A
squamous epithelial cells
- produce keratin (structural protein that forms filaments) and is part of cytoskeleton
- differentiate as they move to the surface, helping skin maintain its structure and function
10
Q
Describe the life cycle of keratinocytes.
A
- old skin cells are shed through process called desquamation
- renewal of epidermis occurs approximately every 28 days
11
Q
What are corneocytes?
A
dead keratinocytes formed at the final stage of differentiation
12
Q
What is the function of melanocytes?
A
produce and secrete melanin, which provides skin with colour and photoprotection
- excessive melanin production can result in hyperpigmentation
13
Q
What are Langerhans cells?
- What is their function?
A
- derived from bone marrow
- function as antigen-presenting-cells (APC)
- tissue-resident macrophages by origin, but functionally more similar to dendritic cells
14
Q
What is the function of Merkel cells?
A
believed to function as slow adapting touch receptors
15
Q
What is the pathophysiology of minor fungal skin infections (such as ringworm, jock itch, and athlete’s foot) associated with the epidermis?
A
- caused by skin-loving fungi called dermatophytes
- use dead keratin in epidermis as source of nutrition and growth
- do not invade living tissue, and only affect top layer of epidermis
16
Q
What are the 2 layers of the dermis?
A
- papillary dermis (superficial layer)
- reticular dermis (deeper layer)
17
Q
What is the papillary dermis?
- What is its function?
A
loose connective tissue
- interdigitates with downward projections of epidermis (aka ‘rete ridges’) – epidermis has to get nutrients from dermis because there are no blood vessels in epidermis
18
Q
What is the reticular dermis?
A
thicker, less cellular, more dense connective tissue, contributing to skin overall structure
- contains larger blood vessels
19
Q
What are the main components of the dermis?
A
- fibroblasts
- adnexa
- blood vessels, lymphatics, nerves
20
Q
What do fibroblasts do?
A
produce collagen, elastin, and ground substance
21
Q
What is collagen?
- What is its function?
A
fibers that make up 70% of dry weight of skin
- provides skin’s tensile strength
- important role in wound healing
22
Q
What is elastin?
A
fibers responsible for skin elasticity
23
Q
What is ground substance?
A
gel-like extracellular matrix that fills spaces between components of dermis
- consists of glycosaminoglycans (ie. hyaluronic acid, proteoglycans, glycoproteins) which attract water, influencing both volume of water in the ground substance and its viscosity
- hyaluronic acid is often used in moisturizers and other cosmetics to maintain water volume in dermis
24
Q
What are adnexa and some examples?
A
skin appendages
- hair follicles
- nail
- sebaceous glands
- eccrine glands
- apocrine glands
25
What are hair follicles made of?
- What are their 2 main components?
- What is their function?
primarily made up of dead, keratinized cells, connected by extracellular proteins
- two main components: visible external hair shaft, and hair follicle located within skin
- provides mechanical protection, improves sensory function, helps regulate body temperature
26
What are nails?
- How do nails grow?
- What is the structure?
- What is their function?
clear, hard plate made up of dead keratinized epidermal cells
- nail growth starts in nail matrix where new cells are formed, and old cells are pushed outward
- nail plate (visible portion of nail) covers nail bed, where it adheres to finger
- protects fingertips and toes
27
What are sebaceous glands?
- What are they associated with?
- Where are they found?
- What is their function?
- What influences them?
exocrine gland
- associated with hair follicles – pilosebaceous unit
- found throughout body, except on palms and soles
- secrete sebum (composed of triglycerides, wax esters, squalene, and free fatty acids), which helps maintain moisture of skin and hair
- under hormonal influence – acne often triggered by puberty
28
What are eccrine glands?
- What is their function?
- Where are they located?
exocrine gland
- release sweat, which helps regulate body temperature
- located all over body – except lips, external auditory canal
29
What are apocrine glands?
- Where are they located?
- What is their function?
exocrine gland
- located in axillary and anogenital regions
- responsible for body odour – secrete variety of odourless proteins, carbohydrates, ammonia, lipids, and iron, which are digested by bacteria, resulting in production of odorous byproducts
30
How does the skin change as it ages?
- becomes drier, thinner, and more fragile – cell turnover slows down, takes longer for cells to move from basal layer to skin surface, skin becomes more wrinkled as its elasticity decreases
- nail growth, sweat production, and sebaceous gland activity decline
- reduced blood flow slows healing process of wounds
31
What is a dermatology condition associated with the dermis?
onychomycosis
32
What is onychomycosis?
- Describe the treatment process.
fungal infection of nails
- challenging to treat – topical medication penetration into nail is difficult due to their hard, keratinized structure, and often requires long and rigorous regimen
33
What are the characteristics of subcutaneous tissue (hypodermis)?
- loose connective tissue
- highly vascularized
- contains ~50% of body fat
34
What are the roles and functions of subcutaneous tissue (hypodermis)?
- energy store
- insulator
- endocrine organ
35
Describe subcutaneous injections compared to IM injections.
absorption is slower and more sustained than IM, as muscles have richer blood supply that allows for quicker absorption
36
What are the functions of the skin? (6)
- barrier and protection
- immunity
- thermoregulation
- sensation
- UV protection and synthesis of vitamin D
- benefits of topical drugs
37
Describe the barrier and protection function of skin.
- protects organs from mechanical, physical, and microbial damage
- contributes to regulation of body’s water content
- intact skin barrier is crucial for survival
- stratum corneum is main barrier of human skin – highly complex mixture of different types of ceramides, cholesterol, and fatty acids, and highly restrictive barrier
- only certain substances can penetrate skin efficiently – ideal physiochemical properties include moderate lipophilicity (1 < LogP < 3), MW ≤ 500 D
38
Describe the immunity function of skin.
- slightly acidic pH (~5.5-6.5) helps limit proliferation of microorganisms
- highly immunogenic organ – contains tissue-resident Langerhans cells, dendritic cells, and other immune cells such as T cells and macrophages, which are recruited when needed
- actively produces antimicrobial peptides
- hosts variety of commensal bacteria
39
Describe the thermoregulation function of skin.
regulates temperature through sweating, varying blood flow, and hair follicles
40
Describe the sensation function of skin.
various stimuli are processed by skin nerve fibres, which allows sensation of pain, pressure, temperature, and touch
41
What are the benefits of topical drugs? (4)
- non-invasive
- avoids first-pass effect
- simple dosing application by patients
- reduces systemic side effects
42
How does thicker skin affect topical drugs?
(ie. palms, soles, and scalp)
- more difficult for topical drugs to penetrate effectively
- stronger topical drugs (ie. high-potency corticosteroids) are often needed to penetrate skin
43
How does thinner skin affect topical drugs?
(ie. face, genitals, skin folds)
- require weaker topical drugs (ie. mild corticosteroids)
44
What is atopic dermatitis?
- What causes it?
- What is the treatment?
heterogeneous disease with etiology that is not fully understood
- factors linked to skin dysfunction are suggested to play a role – epidermal skin barrier dysfunction, altered skin microbiome
- one of the primary treatments involves barrier therapy, which aims to repair skin barrier
