Physiology Flashcards
1
Q
Name the 3 main layers of the skin from outside inwards
A
Epidermis
Dermis
Subcutis
2
Q
What is the epidermis
A
Outer layer of stratified squamous epithelium
3
Q
What is the dermis
A
Layer of connective tissue beneath the epidermis
4
Q
What is found between the epidermis and dermis
A
Dermo-epidermal junction
5
Q
What is the subcutis
A
The fat layer beneath the dermis
6
Q
Where does epidermis originate from embryonically
A
Ectodermal germ layer
7
Q
Where does the dermis originate from originally
A
Mesoderm germ layer
8
Q
Where do melanocytes originate from
A
The neural crest
9
Q
What happens to the skin in week 4 of development
A
Differentiation into periderm, basal layer and dermis
10
Q
What happens to the skin in week 16 of development
A
Formation of layers: keratin, granular, prickle cell, basal
Melanocytes migrate from the neural crest
11
Q
By what time is the skin fully formed during development
A
26 weeks
12
Q
What are blaschko’s lines
A
Developmental growth pattern of skin thought to represent pathways of cell migration during fetal development
13
Q
What are the 4 layers of the epidermis
A
Keratin
Granular
Prickle cell
Basal
14
Q
What controls epidermal turnover
A
Growth factors, cell death and hormones
15
Q
Role of the basal layer of the epidermis
A
Epidermal renewal and regeneration
Contains melanocytes for protection from UV
16
Q
The 3 main types of cells in the basal layer of the epidermis
A
Basal cells
Keratinocytes
Melanocytes
17
Q
What are basal cells
A
Columna or cuboidal cells that undergo rapid mitotic divisions to produce new keratinocytes
18
Q
Structure of the basal layer of the epidermis
A
Usually one cell thick
19
Q
Structure of the prickle cell layer of the epidermis
A
Larger polyhedral cells
Lots of desmosomes
Intermediate filaments connect to desmosomes
20
Q
What cells are found in the prickle cell layer of the epidermis
A
Prickle cell
Keratinocytes
Langerhans cells
21
Q
2 main function of the prickle cell layer of the epidermis
A
Structural support and immune function
22
Q
Structure of the granular layer of the epidermis
A
2-3 layers of flatter cells
23
Q
What cells are found in the granular layer of the epidermis
A
Keratinocytes
Keratohyalin granules
Odland bodies
24
Q
What are odland bodies
A
Secretory organelles that contribute to skin barrier
25
What do keratohyalin granules contain
Filaggrin
Natural moisturising factor
26
Role of filaggrin
Binds to keratin intermediate filaments promoting aggregation and cross linking
27
What do odland bodies secrete
Keratohyalin granules
28
Role of the keratin layer of the epidermis
Tight waterproof barrier
29
Main cellular component of keratin layer
Corneocytes
30
What are corneocytes
Flattened non-viable cells that have undergone keratinisation, transforming them into tough and resilient structures
31
Posh name for keratin layer
Stratum corneum
32
Posh name for granular layer
Stratum granulosum
33
Posh name for prickle cell layer
Stratum spinosum
34
Posh name for basal layer
Stratum basale
35
What are melanocytes
Pigment producing dendritic cells
36
Role of melanosomes
Convert tyrosine to melanin pigment
37
What are the 2 melanin pigments
Eumelanin
Phaeomelanin
38
What is the role of melanin
Absorbs UV rays to protect DNA in the cells nuclei
39
What gene is important skin pigmentation
MC1R gene
40
Risk associated with mutation in MC1R gene
Most vulnerable to sun exposure
41
What does 1 defective copy of MC1R causes
Ginger hair
42
What does 2 defective copies of the MC1R gene cause
Ginger hair and freckles
43
Characteristics of darker skin
Larger melanosomes containing more melanin
More Eumelanin
Melanosomes exist through the epidermis
44
Characteristics of fairer skin
Smaller amounts of melanin
More phaeomelanin
Melanosomes confined to the basal layer in unexposed skin
45
Where do langerhans cells come from
The bone marrow
46
Role of langerhans cells
Antigen presenting cells
47
Where are langerhans cells found (3)
Prickle cell layer of the epidermis
Dermis
Lymph nodes
48
Where are merkel cells found
Basal layer of the epidermis
49
What is the role of a merkel cell
Mechanoreceptors
50
Role of masticatory oral mucosa
Keratinised to deal with friction and pressure
51
Role of the dermo-epidermal junction
Support and anchorage of basal cells
Semi-permeable membrane acting as a barrier and a filter
52
Cells found in the dermis
Fibroblasts
Macrophages
Mast cells
Lymphocytes
Langerhans cells
53
Role of fibroblasts in the dermis
Maintain ground substance
Produce collagen
54
Fibres found in the dermis
Collagen and elastin
55
Difference in the dermis in different skin types
Caucasian skin has a thinner dermis and bigger collagen fibres
AA skin has larger and more numerous fibroblasts
56
Organisation of blood vessels in the dermis
Horizontal plexuses
57
Name 2 special nervous receptors found in the dermis
Meissners corpuscle
Pacinian corpuscle
58
Where are meissners corpuscles abundantly found
Tactile areas of fingers and toes
59
What do meissners corpuscles detect
Tactile stimuli, light touch
60
What do pacinian corpuscles detect
Pressure
61
Where are pain receptors located in the skin
Basal layer of the epidermis
62
Role of collagen and elastic fibres in the dermis
Provide tensile strength and elastic qualities of skin
63
Name the 3 types of skin glands
Eccrine
Sebaceous
Apocrine
64
What do sebaceous glands produce
Sebum
65
What is sebum associated with
Acne
66
Where are sebaceous glands usually found
Chest, face, back
67
Functions of sebaceous gland (3)
Control moisture loss
Protect against fungal infection
Lubricate hair follicle
68
Sebaceous gland
Holocrine secretion opening into pilary canal
69
What is an apocrine gland
Develop as part of the philosebaceous unit
70
Where are apocrine glands found
Axillae, groin, eyelids, mammary and perineal regions
71
Role of apocrine glands
Produce oily fluid
72
What are apocrine glands dependent on
Androgens
73
Where are eccrine glands found
EVERYWHERE
particularly palms, soles, forehead and axilla
74
Role of eccrine glands (3)
Filtration
Cooling by evaporation
Moistens palms and soles for grip
75
What causes eccrine gland stimulation
Mental, thermal and gustatory stimulation
76
What is the pilosebaceous unit composed of
Hair follicle
Hair shaft
Arrector pili muscle
Sebaceous glands
77
What are the 3 main segments of the hair follicle
Infundibulum
Isthmus
Hair bulb
78
What does the hair bulb contain
Hair matrix and dermal papilla
79
What does the hair matrix contain
Keratin producing cells
80
What gives hair pigment
Melanocytes above the dermal papilla
81
Difference in keratin between the central medulla and the outer cortex
Medulla contains soft keratin, and the outer cortex and cuticle contain hard keratin
82
What hair type has the highest hair density
Caucasian hair
83
What hair type has the most moisture content
Caucasian hair
84
What type of hair has the fastest growing rate
Asian hair
85
Which type of hair is the most fragile
Black hair
86
Name the 3 phases of hair growth
Anagen, catagen, telogen
87
What is the anagen phase of hair growth
The growing phase
88
How long does the anagen phase usually last
3-7 yrs
89
What proportion of hair is in the anagen phase
90%
90
What is the catagen phase of hair growth
Involuting phase
91
How long does the catagen phase last
3-4 weeks
92
What proportion of hair is in the catagen phase
10%
93
What is the telogen phase of hair growth
Resting phase
94
What happens in the telogen phase
Shedding
95
What is important about the telogen phase
It is asynchronous
96
What is the growth rate of nails
0.1mm per day
97
Name 2 factors that influence nail growth
Fingers grow faster
Grows faster in summer
98
Give an example of a type of drug that can increase nail growth
Anti-fungals
99
Role of the cuticle
Protects from infection
100
Role of the hyponychium
Secures the free nail edge
101
What is the main role of vitamin D
Increase the flow of calcium into the blood stream enabling the normal mineralisation of bone
102
How does vitamin D do its job
Promotes absorption of calcium and phosphorus from food into the intestines and reabsorption of calcium in the kidneys
103
What is another name for vitamin D2
Calciferol
104
How is vitamin D2 made
From inactive provitamin ergosterol in plants by the action of sunlight
105
What is the most effective type of vitamin D
D3
106
Where can you find vitamin D2
In mushrooms
107
How is vitamin D3 made
In the skin by the action of sunlight
108
Where can you also find vitamin D3
Small amounts in oily fish and meat
109
What is another name for vitamin D3
Cholecalciferol
110
How is vitamin D3 stored
As hydroxycholecalciferol in the liver
111
Where is the active, hormonal form of vitamin D found
In the kidneys
112
Give 2 consequences of vitamin D deficiency
Rickets and osteomalacia
113
Name the 2 places the conversion of T4-T3 can occur
MOSTLY in peripheral tissues including the skin
Some in the thyroid gland
114
Consequences of loss of barrier function of skin
Fluid loss- dehydration
Protein loss- hypoalbuminaemia
Infection
115
Consequences of the loss of thermoregulation function of the skin
Heat loss - hypothermia
116
Consequence of loss of metabolic function of the skin
Disordered thyroxine metabolism
117
What is a wound
Any break in the skin
118
What is healing by primary intention
Edges are approximated by stitches leading to rapid healing
119
What is healing by secondary intention
Sides of the wounds are not opposed so healing occurs from the bottom of the wound upwards
120
When is healing by secondary intention used
Larger wounds that are too tight to stitch
Areas where direct closure would cause significant distortion of the surrounding tissue
121
What are the 3 stages of wound healing
Inflammation
Proliferation
Remodelling
122
What happens in the inflammation stage of wound healing
Platelets form initial clot and release inflammatory mediators
Leukocytes debride wound
Inflammation starts to decrease as keratinocyte proliferation and new tissue formation start
123
How do leukocytes debride a wound (2)
Phagocytose bacteria
Scavenging cellular debris
124
What happens in the proliferation stage of wound healing
Cells divide and re-epithelialise the wound surface
Granulation tissue formation is stimulated
Fibroplasia and angiogenesis
125
What is fibroplasia
The formation and proliferation of fibrous tissue mostly composed of fibroblasts and collagen fibres
126
What happens in the tissue remodelling phase of wound healing
New tissue converted into mature scar tissue
Fibroblasts lay down collagen to improve the tensile strength
127
How long does a wound have to be present to be chronic
>6 weeks
128
Give an example of a chronic wound
Leg ulcer
129
Common characteristic of a chronic wound
Slough
130
How do chronic wounds tend to heal
From the edges
131
What are 4 factors that contribute to pressure sores
Prolonged pressure over bony area
Lack of blood flow
Irritation from bodily fluids
Friction from bedding or clothing
132
What is hyperkeratosis
Increased thickness of the keratin layer
133
What is parakeratosis
Persistence of nuclei in the keratin layer
134
What is acanthosis
Increased thickness of epithelium
135
What is papillomatosis
Irregular epthelial thickening
136
What is spongiosis
Intercellular fluid accumulation within the epidermis in the spaces between keratinocytes
137
What are the 4 main classifications of inflammatory skin diseases
Spongiotic
Psoriaform
Lichenoid
Vesicubullous
138
What characterises spongiotic skin diseases
Interaepidermal oedema
139
What characterises psoriaform skin diseases
Elongation of the rete ridges
140
What characterises lichenoid skin diseases
Basal layer damage
141
What characterises vesicubullous skin diseases
Blistering
142
Give an example of a spongiotic skin disease
Eczema
143
Give an example of a psoriaform skin disease
Psoriasis
144
Give an example of a lichenoid skin disease
Lichen planus
Lupus
145
Give an example of a vescubullous skin disease
Pemphigus, pemphigoid
Dermatitis herpetiformis
146
What is Pruritus
An unpleasant, poorly localised, non-adapting sensation that provokes the desire to scratch
147
What nerve fibres sense the itch sensation
Unmyelinated C fibres
148
Where in the brain is the itch sensation processed
Parts of the forebrain and hypothalamus
149
How is information on itch conveyed
Centrally in 2 separate systems that use the lateral spinothalamic tract
150
Pruritoceptive itch
Something in skin triggers the itch
151
Neuropathic itch
Damage to central or peripheral nerves causes an itch
152
Neurogenic itch
No evident damage in CNS, but itch caused by e.g. opiate effects on CNS receptors
153
Name some systemic diseases associated with itch
Haematological, paraneoplastic, liver and bile duct, kidney disease, thyroid issues
154
Psychogenic itch
Psychological causes with no CNS damage
155
Name some non-specific anti-itch treatments
Sedative anti-histamines
Emollients
Antidepressants
Anti-epileptics for neuropathic itch
Phototherapy
156
When does skin aging usually occur from
35
157
What occurs during skin aging (4)
Skin becomes thinner
Subcutaneous fat is lost
Fine wrinkles develop
Number of hair follicles etc. reduce and skin becomes dry
158
What is solar elastosis
Degeneration and clumping of elastin fibres in the dermis as a result of chronic exposure to UV radiation
159
How does the skin appear in solar elastosis
Yellow-brownish hue, wrinkles
160
Difference between a food allergy and intolerance
Allergy is IgE mediated, intolerance is a non-immune reaction
161
Effect of obesity on collagen structure and function and wound healing
Reduced mechanical strength due to failure of collagen deposition to match the increased surface area
162
Effect of obesity on sebaceous glands
Increased androgens produced in peripheral fat stimulate glands leading to acne
163
Effect of obesity on subcutaneous fat
Increased hormone production e.g. testosterone
164
Effect of obesity on lymphatics
Pressure from fat stops flow and causes leakage into subcutaneous tissues
165
Effects of obesity on circulation
Microvascular dysfunction resulting in increased skin blood flow - may contribute to hypertension
166
Effect of obesity on apocrine and eccrine glands
Increased activity in skin folds increases moisture
Maceration and friction increases irritation
167
Effect of obesity on barrier function of the skin
Increased trans-epidermal water loss so skin tends to be dry
168
What is acanthosis nigricans associated with
Insulin resistance
169
What is acanthosis nigricans
Velvety thickening and pigmentation of skin folds
170
Where is acanthosis nigricans usually seen
In the axilla
171
What is hidradenitis suppurative
Chronic inflammatory disease where boils and abscesses form and scar apocrine gland areas
172
What is hidradenitis suppurative associated with
Hyper-androgenism
173
What is intertrigo
Macerated red plaques which develop in skin folds due to high moisture levels, friction, increased pH and reduced barrier function
174
What kind of psoriasis is aggravated by obesity
Flexural
175
What are keratinocytes
The structural and functional cells of the epidermis
176
Roles of keratinocytes
Produce antimicrobial peptides to kill pathogens
Produce cytokines and chemokines
177
What are langerhans cells characterised by
Birbeck granules
178
What is the main type of T cell found in the epidermis
CD8+ T cells
179
What is an Arthus reaction
Localised vasculitis associated with deposition of immune complexes and activation of complement
180
Name the 2 types of dendritic cells found in the dermis
Dermal and plasmacytoid
181
Role of dermal dendritic cells
Involved in antigen presenting and secreting cytokines and chemokines
182
Role of plasmacytoid dendritic cells
Produce INFalpha, found in diseased skin
183
Role of class I MHC
Present endogenous antigens to cytotoxic T cells
184
Role of class II MHC
Present exogenous antigens to Th cells
185
Role of TNFalpha
Mediated communication between T cells and macrophages
186
What secretes IL17
Th17 cells
187
Role of IL17
Activates keratinocytes and fibroblasts
188
What secretes IL23
Dendritic cells and macrophages
189
Role of IL23
Triggers differentiation and growth of Th17 cells
