Introduction to Dermatology 1 Flashcards
(144 cards)
1
Q
The skin arises due to juxtaposition of which two major embryological elements?
A
Epidermis and the Dermis
2
Q
What does the epidermis originate from?
A
The ectoderm
3
Q
What does the mesoderm come into contact with?
A
inner surface of the epidermis
4
Q
What does the dermis originate from?
A
The mesoderm
5
Q
What is the mesoderm essential for enducing?
A
The differentiation of epidermal structures
6
Q
What is the epidermis formed as by week 5?
A
A single basal layer of cuboidal cells
7
Q
What is the periderm?
A
A secondary layer of squamous, non-keratinizing cuboidal cells which sits on top of the basal layer of the epidermis
8
Q
When does the periderm develop?
A
Week 5
9
Q
What is the vernix caseosa?
A
A white waxy protective substance which covers the skin during the last trimester of fetal development
10
Q
what is the stratum germinativum also called
A
stratum basale
11
Q
What happens to the basal layer of cuboidal cells from week 20?
A
The stratus germinativum proliferate to form a multi-layered intermediate zone which consists of four more superficial strata
12
Q
What are the four superficial strata called?
A
The Spinosum, granulosum, lucidum and corneum
13
Q
Where is the stratum lucidum found?
A
On the palms of hands and the soles of feet
14
Q
what is the purpose of rete ridges
A
increase the contact area between layers, enhancing adhesion
15
Q
when do dermal papillae form
A
weeks 12-14
16
Q
what are dermal papillae?
A
The thin top layer of the dermis (the inner layer of the skin).
17
Q
in what layer does the division of cells in epidermis occur?
A
basal layer
18
Q
when does the neurovascular supply in dermal papillae develop
A
weeks 12-14
19
Q
What are rete ridges?
A
When the epidermal ridges protrude as troughs into developing dermis beneath
20
Q
When does the development of hair follicles occur?
A
Between weeks 9-13
21
Q
In which superficial stratum layer do hair follicles develop?
A
In the stratum germinativum
22
Q
What is lanugo hair?
A
soft, feathery hair that can grow all over the body, most often on the back and shoulders.
23
Q
What cells is the epidermis composed of?
A
Keratinocytes
24
Q
How long does the progression from stratum basale to Stratum corneum take?
A
30-40 days
25
What is the order of cellular progression of cells in the epidermis?
Starts with basale - then Spinosum, Granulosum, Lucidum and finally Corneum
26
What process is accelerated in skin conditions like psoriasis?
The cellular progression from the basal layer
27
What happens to the morphology of the epidermal cells as they progress from basal layer to Stratum Corneum?
They become progressively flatter
28
What are the special features of the stratum corneum?
They lack nuclei or organelles
29
What does the filamentous cytoskeleton of keratinocytes consist of? - 3
Actin containing microfilaments
Tubulin-containing microtubules
Intermediate filaments (keratins)
30
What are the five roles of keratins?
Structural properties
Cell signalling
StressResponse
Apoptosis
Wound Healing
31
What are desmosomes?
Major adhesion complex in the epidermis which anchor keratin intermediate filaments to cell membrane and bridge adjacent keratinocytes - allowing tissue architecture
32
What do desmosomes provide the epidermis with?
Resilience -allow the withstanding of trauma
33
What are gap junctions?
Clusters of intercellular channels (connexons) which allow connections between cytoplasm of adjacent keratinocytes to allow ions and small molecule transport
34
What are gap junctions essential for? - 4
Cell synchronization
cell differentiation
cell growth
metabolic coordination
35
what is the role of adherens junctions?
Transmembrane structures that engage with actin skeleton for cell-cell adhesion and intracellular signalling
36
what do tight junctions do
regulate the passage of proteins and liquids across the cell monolayer
37
What is the primary roles of tight junctions? - 2
maintaining barrier integrity and cell polarity
38
what are melanocytes?
They are dendritic cells which distribute melanin pigment to keratinocytes
39
How does the number of melanocytes change between different ethnicities?
The number of melanocytes does not change, however the amount of pigment they produce does vary
40
What four other cells are present in the epidermis aside from keratinocytes
Melanocytes, Langerhans cells, Merkel cells and Mast cells
41
What are Langerhans cells?
Dendritic cells which are antigen presenting and found in the epidermis
42
What are Merkel Cells?
Mechanosensory receptors
43
What sits under the epidermis layer?
Basement membrane
44
What is the basement membrane also known as?
The dermal-epidermal junction
45
state the key proteins and glycoproteins found in the dermal-epidermal junction - 4
type 4 & 7 collagens, laminin and integrins
46
What is the dermal-epidermal junction composed of?
Proteins and glycoproteins
47
What is the role of the basement membrane? - 4
cell adhesion
cell migration
rete ridge formation
wound healing
48
What layer of the skin is under the basement membrane?
The dermis
49
where does the dermis arise from?
mesoderm
50
What are the two layers the dermis is split into?
Papillary dermis and Reticular dermis
51
What aspect of the dermis layer provides resilience?
The supporting ECM
52
Which layer of the dermis is closest to the epidermis?
The papillary dermis
53
Which dermal layer is highly vascular?
Papillary dermis
54
What is the reticular dermis composed of?
Dense connective tissue
55
Which dermal layer forms the bulk of the dermis?
The reticular dermis
56
What is the papillary dermis composed of?
Loose connective tissue
57
What is the papillary dermis composed of?
loose connective tissue
58
Which proteins are present in the dermis?
Collagen and elastin fibres (fibrillin and elastin)
59
Which collagen types are present in the dermis?
Type 1 and Type 3
60
What are the three glycoproteins found in the dermis?
Fibronectins, fibulin and integrins
61
What do the glycoproteins found in the dermis do?
They facilitate cell adhesion and cell motility
62
What is the ground substance found in the dermis composed of?
Glycosaminoglycan and proteoglycan
63
What does the ground substance lie between?
The dermal collagen and elastic tissue
64
What are the primary cells present in the dermis?
Fibroblasts
65
What do fibroblasts do?
Make collagen
66
What cells aside from fibroblasts are present in the dermis? - 5
Histiocytes, mast cells, neutrophils, lymphocytes and dermal dendritic cells
67
What does the subcuteanous layer contain?
Connective tissue and fat
68
What are melanocytes derived from?
The neural crest
69
What are melanocytes derived from?
The neural crest
70
Does the blood supply cross into the epidermis?
No
71
Describe the vascular supply of the skin?
The blood supply runs deep - composed of superficial vascular plexus which runs in the dermis
72
Which dermal layer has more vascular supply?
papillary dermis - the superficial dermal layer
73
What is the innervation of the skin composed of?
Both sensory and autonomic components
74
What two autonomic components are involved in the innervation of the skin?
Cholinergic and Adrenergic
75
What is meant by eccrine?
Opens directly onto the surface of the skin
76
What is meant by apocrine?
Apocrine sweat glands, which are usually associated with hair follicles, continuously secrete a fatty sweat into the gland tubule
77
What innervation do apocrine glands receive?
Adrenergic
78
What is a pilosebaceous unit?
A structure consisting of hair, hair follicle, arrector pili muscle and sebaceous gland
79
Which areas of the skin receive more innervation than any where else? - 4
Face, extremities, genitalia and hands
80
Describe the innervation found in the superficial dermis?
A branching network, often accompanying blood vessels which forms a mesh of interlacing nerves
81
What are the two types of afferent nerve endings?
Corpuscular and free
82
What type of receptors are found in free nerve endings
Non-encapsulated receptors
83
What type of receptors are found in corpuscular nerve endings?
Encapsulated receptors
84
Which layer of the skin are non-encapsulated receptors found in?
Epidermis
85
Which layer of the skin are encapsulated receptors found in?
Dermis
86
What are two examples of encapsulated receptors?
Pacinian and Meissners
87
What is a Meissner corpuscle?
It is an encapsulated, unmyelinated mechanoreceptor
88
Where are Meissner's corpuscle located, and where are they most concentrated?
Located in the superficial dermis and most concentrated in thick, hairless skin eg finger pads and lips
89
What do Meissner Corpuscles help to detect?
Light touch and slow vibration
90
What is another name for Meissners Corpuscle?
Tactile Corpuscle
91
What is a Ruffini Corpuscle?
A slow acting mechanoreceptor
92
Where is the Ruffini Corpuscle found?
Deeper in the dermis
93
What shape are Ruffini Corpuscles?
Spindle shaped
94
What are Ruffini Corpuscles sensitive to?
Skin stretch
95
Where are Ruffini Corpuscles found with the highest concentration?
Around fingernails
96
What do Ruffini Corpuscle monitor?
The slippage of object
97
What is a Pacinian Corpuscle?
An encapsulated, rapidly adapting mechanoreceptor
98
What are Pacinian Corpuscle involved in sensing?
Deep pressure and vibration
99
What is the shape of Pacinian Corpuscle?
Ovoid
100
Where are Pacinian Corpuscle most commonly found?
In the dermal Papillae of hands and feet
101
What is the Merkel Cell derived from?
A modified keratinocyte
102
What are Merkel cells used to detect?
Light and sustained touch, pressure
103
What are Merkel cells used to detect?
Light and sustained touch, pressure
104
What layer of the epidermis are Merkel cells found?
Basal layer
105
Where are Merkel cells most populous?
In fingertips
106
Aside from fingertips, where else are Merkel cells found? - 4
In the palms, soles, and oral and genital mucosa
107
What nerve ending helps to detect pain?
Noicoreceptors
108
what nerve endings can detect touch and pressure - 4
ruffini, pacinian, free and merkel
109
what nerve endings can detect vibration - 2
meissner and pacinian
110
What nerve ending helps to detect temperature?
Thermoreceptors
111
What three microbiota are found in the skin?
Bacteria, fungi and viruses
112
What is the role of the microbiome of the skin?
Immune modulation and epithelial health
113
What is the predominant bacteria found in the microbiome of skin? - 4
Actinobacteria, Firmicutes and Bacteroidetes and Proteobacteria
114
Is the microbiome involved in disease?
Yes
115
what are the 6 functions of the skin?
Immunological Barrier
Physical Barrier
Thermoregulation
Sensation
Metabolism
Aesthetic Appearance
116
What are the important immune cells in regards to the skin functioning as a immune barrier
Langerhans cells
117
what are sentinel cells?
cells in the body's first line of defense
118
Which cells acts as sentinel cells in the epidermis
The langerhans cells
119
How do Langerhans cells act against infection?
They initiate the immune response to microbial threats by detecting PAMPs
120
How are the dendritic processes of the Langerhans cells extended?
Through intercellular tight junctions to sample the outermost layer of the skin - stratum corneum
121
Which cells do Langerhans cells promote the expansion and activation of?
Skin resident regulatory cells (Tregs)
122
Which cells carry out immune surveillance in the dermis?
Tissue-resident T cells, macrophages and dendritic cels
123
What are the two keratinocyte derived endogenous antibiotics that are involved in the innate immune defense against bacteria and viruses?
Defensins and Cathelicidins
124
What does the cornified cell envelope and stratum coneum restrict?
Water and protein loss from the skin
125
What is one of the most toxic substance which the skin acts as a barrier against?
UV
126
How does the skin protect against UV-induced DNA damage?
Melanin helps prevent UV from actioning its mutagenic property
127
How does subcutaneous fat act as a physical barrier?
It acts as a shock absorber, helps cushion trauma
128
What happens when the skin loses the ability to restrict water and protein loss?
Leads to dehydration which can cause pre-renal failure and high-output cardiac failure
129
What type of sweat does eccrine glands secrete?
Salty sweat
130
Where are apocrine glands most commonly found?
In the axilla and groin
131
How does the skin regulate heat loss?
Through vasodilation and vasocontriction in deep or superficial vascular plexuses
132
Which glands are involved in the cooling effect?
Eccrine glands
133
What happens to the superficial vascular plexuses when we want to lose heat?
Vasodilation
134
How do we lose heat through vasodilation/constriction?
radiation
135
Aside from thermoregulation, what are the glands also important in?
FLuid regulation
136
Synthesis of what metabolic compound occurs partially in the skin?
Vitamin D
137
What percentage of total body fat is stored in the subcutaneous fat?
80%
138
How does subcutaneous fat have metabolic functions?
It acts as a calorie reserve
139
Which hormone is found in the subcuteaous fat?
Leptin
140
What does the hormone leptin do?
Acts on hypothalamus to regulate hunger and energy metabolism
141
What occurs when you do not produce leptin?
You have an insatiable appetite, gain unnecessary amount of adipose tissue = fat
142
What psychological impact can skin have?
Leads to feels of low self worth, feeling "ugly", not wanting to get into romantic relationships, increased risk of suicide
143
What skin condition can cause renal failure?
Transepidermal fluid loss
144
what is the stratum germinativum also called
stratum basale
