Structure and Function Flashcards
1
Q
is skin the largest vital organ in the body
A
yes
2
Q
what is the epidermis
A
outer layer of the skin
3
Q
what type of cells make the epidermis
A
stratified cellular epithelium
4
Q
where is the dermis
A
beneath the epidermis
5
Q
what makes the dermis
A
connective tissue
6
Q
what embryological layer makes the epidermis
A
ectoderm- forms a single layer periderm which then casts off
7
Q
what skin layer does the mesoderm make
A
dermis
8
Q
what embryological layer makes melanocytes
A
pigment cells from neural crest
9
Q
what is gastrulation
A
cellular organisation of embryo in days 7-10 into germ layers
10
Q
list from outermost to innermost the layer of skin at 4 weeks
A
periderm
basal layer
dermis
11
Q
list from outermost to innermost the layer of skin at 16 weeks
A
keratin layer granular layer prickle cell layer basal layer dermis
(same as adult skin, develops at 16)
12
Q
describe blaschko’s lines
A
developmental growth pattern of skin- not following vessels, nerves or lymphatics
13
Q
how can skin disease be traced back to the original diseased cell
A
by following blaschko’s lines
14
Q
what is between the epidermis and the dermis
A
dermo-epidermal junction
15
Q
what is the sub cutis
A
predominantly fat- gives elasticity
16
Q
what muscle controls movement of the hair
A
arrector pilli
17
Q
where in skin do blood vessels run
A
in dermis
18
Q
what are the structural keratins in the epidermis called
A
keratinocytes
19
Q
what other cells make up the epidermis (3)
A
melanocytes, langerhans cells, merkel cells
20
Q
what are the epidermal cell layers (outer to inner)
A
keratin layer
granular layer
prickle cell layer
basal layer
21
Q
what part of the epidermis is responsible for renewal and dividing
A
basal layer
22
Q
what do apocrine cells produce
A
sweat
23
Q
what are callouses
A
when mechanical trauma triggers extra skin to be put down to protect epidermis
24
Q
what regulates epidermal turnover
A
growth factors, cell death, hormones
25
when is regulation of epidermal turnover lost (goes too fast)
skin cancer psoriasis
26
when can regulation of epidermal turnover vary
with age, time of year (faster in summer), stress, genetics
27
what is the white stuff is psoriasis
thickened keratin that doesn't come off
28
why is psoriasis red
as broadened prickle layer- varies between thick and thin, shows blood vessels beneath
29
where do keratinocytes migrate from
basement membrane
30
describe the basal layer
usually one cell thick, small cuboidal cells, lots of intermediate filaments (keratin), highly metabolically active (stem cells)
31
where is the basal layer
between the dermis and epidermis
32
why is it called the prickle layer
as daughter cells move upward from the basal membrane erratically and don't permanently stick to each other
33
what are desmosomes
connections between cells in the prickle layer
34
what types of cells are in the prickle layer
larger polyhedral cells
35
what connects to desmosomes
intermediate keratin filaments
36
what creates the granular layer
when prickle cells surface they produce proteins (filaggrin and keratin) which make large keratohyalin granules. the cell then dies and granules are released creating a cornified envelope, sealing the skin (nucleus of cell lost)
37
how does the keratin layer help moisturise the skin
as proteins broken down into amino acid which bind to water
38
what cells make up the keratin layer
corneocytes- overlapping non- nucleated cell remnants
39
what are warts caused by and how
human papiloma virus infects keratinocytes, triggers body to have higher level of proliferation to get rid of virally infected cell= making warts
40
where are the mucosal membranes
eyes, mouth, nose, genito-urinary and GI tracts
41
why are the masticatory parts of the oral mucosa keratinised
to deal with friction and pressure
42
is the lining of the oral mucosa keratisied
no
43
why do mucosal surfaces become white
as mucosa has become thickened and can no longer see blood vessels
44
what cell type lines blood vessels
endothelium- simple squamous
45
describe the epithelia on the palm of the hand
thick keratin layer, undulation follow those of underlying dermis giving ridges of fingerprints
46
describe the epithelia of the sole of the foot
very thick keratin layer, helical structures in kerating layer are terminal parts of sweat ducts
47
describe eccrine sweat glands and list where they are found
found over the whole body except the lips and genitals.
coiled tubular structures which regulate hear and salt loss
48
where are sebaceous glands not present
in palm and sole of feet
49
where are the apocrine sweat glands
axillae, nipples, genitals
50
what provides the tensile and elastic quality of skin
collagen fibres and elastic fibres
51
what 'senses' tactile sensation
meissner's corpuscles
52
what 'senses' deep pressure
pacinian corpuscles
53
where are free nerve endings located in the skin and what do they sense
located in the basal layer of the epidermis, sense pain
54
where are the meissner's corpuscles located
in the dermis, just beneath the epidermis- abundant in tactile areas (fingers and toes)
55
where are pacinican corpuscles located
deep dermis- frequently in fingerpulp
56
describe the contents of a hair follicle
central medulla containing 'soft' keratin
outer cortex of 'hard' keratin
papilla (bulge at base)
57
what does the papilla of the hair molecule contain
multiple vascular channels, the hair matrix and dermal papilla
58
what does the matrix region of the hair follicle contain
keratin producing cells
59
what are nails and the four layers making them
plates of cells filled with hard keratin
nail plate- sits in nail bed
matrix- cells divide and then produce hard keratin
cuticle- extension of the skin fold covering the nail root
hyponychium- secures the nails free edge
60
what is seen histologically in acute dermatitis
intra-epidermal vesicles (containing white cells, fluid and cell debris)
spongiosis- intracellular oedema
61
what is seen histologically in psoriasis
parakeratosis in keratin layer
micro abscesses in epidermis
elongated rete pegs (downward projections of the epidermis into the dermis)
62
why does a bioposy of the sole of the foot have a prominent granular layer
as needed to maintain thick keratin layer
63
what is bullous pemphigoid
formation of blisters
64
what inflammatory cell is seen in bullous pemphigoid stained red
eosinophils (inside the fluid filled bulla) between the epidermis and dermis)
65
what forms a blisters roof
the epidermis
66
black dots on histological slides are what
lymphocytes= inflammation
67
what is parakeratosis
where cells retain their nuclei
68
what are the main functions of the skin (6)
barrier against water loss and entry of unwanted substances
metabolism and detoxification
immune defence
sociosexual
sensory function
thermoregulation
69
what induces toxic epidermal necrolysis (TEN)
drugs
70
what is toxic epidermal necrolysis
keratinocyte death resulting in epidermal detachment at the dermoepidermal junction (skin detaches in large necrotic sheets
71
what are the components of skin failure
loss of thermoregulation (may contribute to cardiovascular instability)
increased risk of infection
failure of homeostatic function (fluid and electrolyte losses, cardiovascular instability)
72
what is needed for healthy skin (6)
intact physical barrier (hydration, infections)
functioning immune system
functioning vasculature (oxygenation, venous and lymphatic drainage, temperature regulation)
sensory nerve function (injury)
sweat glands (thermoregulation)
nutrition
73
what is a wound
any break in the skin
74
what cell types are present in acute wound resolution in the three main layers of skin
epidermis- keratinocytes
dermis-fibroblasts
sub-cutaneous fat- macrophages
75
what are the three stages of healing
inflammation, proliferation and tissue remodelling
76
what is the role of platelets in healing
form the initial clot and release inflammatory mediators
77
what is the role of leucocytes in healing
debride the wound bed by phagocytosing bacteria and scavenging cellular debris
78
what is the role of fibroblasts in healing
lay down matrix and contract the wound (fibroplasia). then lay down collagen to improve the tensile strength of the scar and restore the normal dermal matrix
79
what is angiogenesis
when endothelial cells develop into new blood vessels
80
what is the differnce between primary and secondary intention
primary- an acute wound is closed is closed by approximating wound edges (eg suture)
secondary- an acute wound is left to heal on its own
81
describe the degrees of burns
first- epidermis only
second/partial thickness- epidermis and dermis
third/ full thickness- extends beyond dermis
82
when is a wound considered chronic
if it doesnt heal within three months
83
what is a surface slough
seen in chronic wounds- a mixture of dead cells, polymorphs and bacteria
it is yellow/ green and may stick to underlying tissue
should be removed as has inhibitory effects on healing
84
what can cause delayed healing
infection, poor arterial supply, poor nutrition, impaired venous return, repeated trauma/ pressure, systemic disease (diabetes, anaemia)
85
what leads to a diabetic foot ulcer
neuropathy and microvascular disease
86
what leads to a venous leg ulcer
leaky valves create high back pressure in leg veins (varicose) creating stasis and unhealthy skin which breaks down easily
87
what causes a bed sore
prolonged pressure over bony area + lack of blood flow (2-3 hours), + friction from bedding/ clothing + sweat, blood, urine or faeces = erosion and ulceration of the skin
88
what is a scar
a loss of appendages
89
what is a kerantinocyte
an epidermal cell which produces keratin
90
what are the types of epidermal cell
keratinocytes (95%), melanocytesm langerhans, merkel cells
91
where do melanocytes migrate from
neural crest to the epidermis (in first 3 months of foetal development)
92
where are melanocytes found
basal layer and above
93
what are melanocytes
pigment producing dendrititic cells
94
how do melanocytes produce produce pigment
organelles called melanosomes convert tyrosine to melanin pigment
95
what pigment creates brown and black pigment
and red and yellow
B+B eumelanin
R+Y phaeomelanin
96
what is the role of melanin
absorbs light, forms protective caps to protect the nuclear DNA in basal cells
97
what transforms full melanosomes (melanin granules' to adjacent keratinocyte (which absorbs them)
dendrites
98
what stimulates the formation of melanin
UV radiation and hormones
99
what is vitiligo
an autoimmune disease with loss of melanocytes (attacked by T cells) leading to patches lacking in pigment
100
why dont you want to treat a patient with vitiligo with melanotan
may transform into malignant melanoma
101
what causes albinism
genetic disorder with partial pigment production in melanocytes
102
what is nelson's syndrome
tumour producing too much ACTH which stimulates the pituitary gland to produce melanin stimulating hormone in excess leading to hyperpigmentation
103
where do langerhan cells come from
mesenchymal origin- bone marroe
104
where are langerhans cells in the skin
prickle cell level in the epidermis
105
where else other than skin are langerhans found
dermis and lymph nodes
106
what is the role of langerhan cells
involved in skin immune system:
- antigen presenting cells
- pick up antigen in skin and circulate to lymph nodes via lymphatic system
107
what is the racket shaped organelle in langerhan cells
birbeck granules
108
where are merkel cells
basal, between keratinocytes and nerve fibres
109
what are merkel cells
mechanoreceptors
110
what causes merkle cell cancer caused by
viral infection, rare with high mortality
111
what is a pilosebaceous unit
a hair follicle
112
what creates hair pigmentation
melanocyes above dermal papilla
113
what layer of skin does hair grow out of
basal layer
114
describe the structure of hair
medulla, internal root sheath, cortex, external root sheath
115
what is acne and its mechanism
bacteria living in pilo-sebaceous units, eating the complex sugar and breaking it down into small fatty acids which is oxidised on the skin and acts as a pro inflammatory
116
what do retinoids do
block the formation of sebum- drying the skin starving the bateria of food
117
what are the three phases of hair growth
anagen- growing
catagen- involuting
telogen- resting
118
name 2 hormones that can influence hair growth
thyroxine and androgens
119
what are the three types of hair follicle
lanugo (in utero), vellus, terminal
120
how much hair is shed a day
50-100
121
what is at the base of a hair follicle
the papilla which is surrounded by the matrix
122
can pregnancy affect hair growth
yes
123
what is virilisation
growth of facial hair on females do to excess androgen form a tumour
124
what is alopecia areara
autoimmune hair loss- usually reversible and grows back
125
what cell type are nails
specialised keratins
126
where do nails grow from
nail matrix/ root (similar to hair bulb)
127
what is the dermo-epidermal junction
interface between epidermis and dermis
128
what is the role of the DEJ
epithelial- mesenchymal interaction;
support, anchorage, adhesion, growth and differentiation of basal cells
semi permeable membrane acting as a barrier and filter
129
what are the layer (3) of the dermo epidermal junction
lamina lucida
lamina densa
sub-lamina densa zone
130
name two conditions caused by defects in the DEJ
- bullous pemphigoid
| - epidermolysis bullosa
131
what cells are found in the dermis
fibroblasts, macrophages, mast cells, lymphocytes, langerhans cells
132
what fibres are found in the dermis
collagen (gives strength)
| elastin (gives elasticity)
133
what do fibroblasts do
synthesises extracellular matrix and collagen
134
why is the blood vessel supply in the dermis greater than metabolic needs
to thermoregulate
135
how do blood vessels travel in the dermis
horizontal plexuses
136
what is the path of vasculature from arteriole to collecting venules
precapillary sphincters- arterial- venous capillaries- post capillary venules- collecting venules
137
what is angioma
overgrowth of blood vessels (benign)
138
what is dermographism
exaggerated wealing tendency when the skin is stroked
139
how do the lymphatic vessels travel in the skin
sub epidermal meshed networks (horizontal plexus same as vasculature)
140
what do lymphatic vessels continually drain
plasma proteins, extravasated cells, excess interstitial fluid
141
what are the immune functions of lymph vessels
immune surveillance by circulating lymphocytes and langerhans cells
channelling of microorganisms/ toxins
142
what is chronic lymphoedema
localised fluid retention and swelling due to a compromised lymph system
143
what is the most common infection in lymphoedema
cellulitis
144
what are dermatomes responsible for
somatic sensory (free nerve endings and special receptors)
145
what do free nerve endings do
open directly onto skin surface for pain and temp
146
what is neurofibromatosis
overgrowth of nerve endings
147
what are sebaceous gland and what is their role
holocrine secretion opening into pilary canal
produce sebum to control moisture loss and protect from fungal infection
148
what is the mechanism behind cystic acne
too much oil, oxidised on the ski surface blocking and inflaming pore
149
what and where are apocrine glands
only active when you hit puberty (androgen dependent), in the axiallae and perineum, produce oily fluid that has an odour after bacterial decomposition
150
where are eccrine sweat gland
whole skin surface (especially palms, soles and axillae)
151
what nerve supplies eccrine sweat glands
sympathetic cholingeric nerve supply
152
what stimulates eccrine sweat glands
mental, thermal and gustatory (food) stimulation
153
what is hyperhydrosis
excessive sweat production
154
what causes toxic epidermal nercolysis
drugs
155
what is acute skin failure
when over 90% of skin fails
156
why may you become hypoalbumaenic in TEN
as losing water, albumin in water also lost
157
what is erythroderma
intense and widespread reddening of the skin
158
what metabolic consequences arise from acute skin failure
disordered thyroxine metabolism
159
what causes steroid-sulphatase deficiency x-linked ichthyosis
deficiency in normal lipids in keratin layer
160
what is the ratio between melanocytes and keratinocytes
1:10
161
what is the skin role is metabolism
vit d metabolism and thyroid hormone metabolism
162
describe the metabolism of vitamin D
Vit d3 stored as hydroxycholecalciferol in liver then converted to 1,25-dihydroxycholecaliferol in kidney
163
why is vit d important
for calcium absorption, deficiency causes rickets
164
where does the conversion of thyroxine in thyroid hormone metabolism occur
20% in thyroid gland
80% in peripheral (to thyroid) tissues including skin
165
what is crusted scabies
a severe form a scabies which occurs in a person with a compromised immune system
166
what is hansens disease
tuberculoid leprosy
167
what is the mechanism of leprosy
intracellular mycobacteria act on the Schwann cells producing a chronic granulomatous reaction resulting in the destruction of both myelin and the underlying nerve cells.The damage to nerves and their protective outer layers leads to permanent neurological damage.
168
what is eczema herpeticum
disseminated herpes simplex virus infection in people with ectopic eczema tendency
169
define stigma
the situation of an individual who is disqualified from full social acceptance
170
what is dermatitis herpaformis
chronic blistering condition, autoimmune condition linked to coeliac disease
171
what is a neuropathic ulcer
skin sore cuased by lack of feeling (neuropathy commonly from diabetes mellitus or less commonly leprosy
