[W9+10] The skin Flashcards
1
Q
what is the technical term for the skin?
A
The Integumentary System
2
Q
what are the 3 layers to the integument?
A
- epidermis
- dermis
- subcutaneous layer (hypodermis)
3
Q
what are the 2 layers of the dermis?
A
- papillary layer
- reticular layer
4
Q
what is the largest organ of the body?
A
the skin
5
Q
what is the surface area of the skin in an adult?
A
1.5-2 m^2
6
Q
what are the 2 main layers of the skin?
A
epidermis and dermis
7
Q
what makes up the subcutaneous layer?
A
areolar and adipose tissue
8
Q
what are the 5 layers to the epidermis? top->bottom
A
Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basale
9
Q
describe the stratum corneum
A
Most superficial layer of epidermis; 20–30 layers of dead, flattened,
anucleate, keratin-filled keratinocytes
10
Q
describe the stratum lucidum
A
2–3 layers of anucleate, dead keratinocytes; seen only in thick skin (i.e., palms of hands, soles of feet)
11
Q
describe the stratum granulosum
A
3–5 layers of keratinocytes with distinct granules in cytoplasm; keratinization begins in this layer
12
Q
describe the stratum spinosum
A
Several layers of keratinocytes attached to neighbors by desmosomes; epidermal dendritic cells present
13
Q
describe the stratum basale
A
Deepest, single layer of cuboidal to low columnar keratinocytes in contact with basement membrane; cell division occurs here; also contains melanocytes and tactile cells
14
Q
describe the papillary layer
A
Superficial layer of dermis; composed of areolar connective tissue; forms dermal papillae; houses capillaries and tactile receptors
15
Q
describe the reticular layer
A
- Deeper layer of dermis;
- composed of dense irregular connective tissue;
- surrounds and supports hair follicles, sebaceous glands and sweat glands, nerves, and blood vessels
16
Q
what type of tissue is the epidermis?
A
Stratified keratinised squamous epithelium
17
Q
true or false:
the epidermis has no blood vessels or nerve endings
A
true
18
Q
where do the cells from the epidermis originate from?
A
- the basal layer (stratum basale)
- Progress and migrate towards the skin surface
19
Q
what are the depper layers of the epidermis bathed in? why?
A
- bathed in interstitual fluid
- from the dermis
20
Q
what happens to the epidermal cells when they reach the skins surface?
A
- they are flat, thin, non-nucleated
- cytoplasm replaced by keratin
21
Q
how long does complete replacement of the epidermis take?
A
~1 month
22
Q
state 4 things about thick skin
A
- found on palms of hands and soles of feet
- all 5 epidermal strata
- 0.4-0.6mm thick
- Has sweat glands but no hair follicles or sebaceous glands
23
Q
state 4 things about thin skin
A
- found everywhere else
- 4 epidermal strata (excluding stratum lucidum)
- 0.075-0.15mm thick
- Contains sweat glands, hair follicles, sebaceous glands
24
Q
what determines skin colour?
A
- Determined predominantly by melanin
- Also by haemoglobin and carotene
- Type and amount of melanin varies, NOT number of melanocytes
25
what 2 things determine the amount of melanin in the skin?
- genetics
- sun exposure
26
what is the difference between darker skinned people and lighter skinned?
- Darker skinned people produce more and darker melanin
- and package melanin into more superficial layers
27
what forms the dermis?
connective tissue:
- collagen
- elastin
28
what gives the dermis its tensile strength?
Collagen fibres bind water and give dermis its tensile strength
29
what allows the dermis to stretch and recoil?
elastin fibres
30
what causes stretch marks/striae?
overstretching/tearing of fibres
31
what 3 cells are found in the dermis?
- fibroblasts
- macrophages
- mast cells
32
describe the dermal papillae
Upward projections of dermal layer, interdigitating with epidermal ridges (downward projections of epidermis)
33
how are blisters formed?
separation of the dermis and epidermis, collection of serous fluid between the layers
33
what are the 2 functions of the dermal papillae?
- Anchor dermis securely to epidermis
- Allow passage and exchange of nutrients and waste products to lower epidermis
33
where is the epidermis thicker? why?
- thicker on palms and soles
- subject to greater wear and tear
34
what creates finger prints?
- Friction ridges formed by meeting of dermal papillae and epidermal ridges
- Where arranged in parallel lines are fingerprints
35
what injury may cause a gape and delay healing?
An incision perpendicular
to cleavage lines
36
what are langer lines?
lines of cleavage
– indicate predominant direction of collagen fibres in reticular layer
37
state 5 things that are found in the reticular layer of the dermis
- Small blood and lymph vessels
- Sensory nerve endings
- Sweat glands and ducts
- Hairs and arrector pili muscles
- Sebaceous glands
38
what do the arterioles and cappilaries in the dermis supply?
- sweat glands
- hair follicles
- sebaceous glands
the dermis
39
what are the 4 things that the sensory receptors in the dermis detect?
- touch
- temperature
- pressure
- pain
40
what corpuscle detects light pressure and low frequency vibration?
Meissner’s corpuscle
41
what does the Meissner’s corpuscle detect?
light pressure and low frequency vibration
42
what corpuscle detects deep pressure and high frequency vibration?
Pacinian corpuscle
43
what does the pacinian corpuscle detect?
deep pressure and high frequency vibration
44
what detects pain, extreme temperature, chemical irritants?
Free nerve ending (nociceptor)
45
what do free nerve ending (nociceptor) detect?
pain, extreme temperature, chemical irritants
46
where is body hair found?
Everywhere except palms and soles, lips and parts of genitalia
47
what are hair follicles?
downgrowths of epidermal cells into der
48
what is the papilla? where is it found?
- hair bulb
- found at the base of the follicle
49
how is hair formed?
- hair is formed by multiplication of cells in the bulb
- As cells are pushed upwards, they die and become keratinised
- Hair above the skin is the shaft, remainder is the root
50
what determines hair colour?
Colour is genetically determined, dependent on the amount and type of melanin
51
what are arrector pili?
little bundles of smooth muscle fibres attached to hair follicles
52
what are nails derived from?
derived from same cells as epidermis and hair
53
what are nails?
keratin plates
54
what are the function of nails?
protect the tips of fingers and toes
55
when do nails grow faster?
when the environmental temperature is higher
56
where are sweat glands found?
- Widely distributed throughout the skin
- Most numerous in the palms and soles
57
what forms sweat glands?
formed from epithelial cells
58
where are the bodies of sweat glands found?
lie coiled in subcutaneous tissue
59
what are the 2 types of sweat glands?
- Eccrine/merocrine
- Apocrine
60
describe eccrine/merocrine sweat glands
- more common
- open onto skin via pores
61
describe apocrine sweat glands
- open into hair follicles
- become active at puberty
62
where are spocrine sweat glands predominantly found?
in axillae, groins, genital area
63
what causes the odor in apocrine sweat glands?
Bacterial decomposition causes odour
64
what is a specialised example of apocrine sweat glands?
ceruminous gland of outer ear – secretes earwax
65
where are sebaceous glands from?
From secretory epithelial cells (same as hair follicles)
66
how do most sebaceous glands secrete?
via the hair follicles
67
where are sebaceous glands found?
everywhere except palms and soles
68
where are most sebacous glands found?
Most numerous in scalp, face, axillae and groins
69
what sebaceous glands are independant of hair follicles? where do they secrete?
- lips, eyelids, nipple, labia majora, glans penis
- secrete directly onto skin
70
what are the 8 functions of skin?
- thermoregulation,
- water balance,
- protection,
- immune function
- sensation,
- calcium & phosphorus regulation,
- secretion
- absorption
71
how is body temperature regulated?
Negative feedback system regulates balance between heat produced by and heat lost from body
72
what controls the bodies thermoregulation?
hypothalamus
73
where does most heat loss occur? where else is it lost?
- Most heat loss occurs through skin
- Small amounts via expired air, urine and faeces
74
what affects thermoregulation?
difference between body and environmental temperatures
75
what does core temperature reduction lead to?
Core temperature reduction leads to nerve impulses which stimulate dermal arteriolar constriction and arrector pili
76
what are arrector pili?
- Contraction makes the hair stand erect and raises the skin around the hair
- Stimulated by sympathetic nerve fibres in response to cold (or fear)
77
what is the function of arrector pili?
The erect hairs trap air, acting as insulation layer
78
what are the 4 mechanisms for heat loss via skin?
- conduction
- radiation
- convection
- evaporation
79
explain how heat is lost via conduction
heat transferred to clothing and other objects in direct contact with skin
80
explain how heat is lost via radiation
exposed skin radiates heat away from body
81
explain how heat is lost via convection
air passing over exposed skin rises and is replaced by cooler air
(facilitated by nerve impulses from hypothalamus stimulating dermal arteriolar dilatation)
82
explain how heat is lost via evaporation
body heat converts sweat into water vapour
83
when do you sweat in regards to heat?
- When body temperature increases by 0.25-0.5 degrees C, sweat glands secrete sweat
- Still occurs when environmental temperature low (insensible heat loss and water loss)
84
what does excessive sweating lead to?
lead to loss of water and sodium
85
what sweat is produced by eccrine glands?
produce watery sweat
86
what is the main function of eccrine glands
sweat to control body temperature
87
what type of sweat do apocrine glands produce?
thicker oilier sweat
88
what stimulates sweat production by apocrine glands?
stimulated more by stress than heat
89
how is excessive water gain prevented by the skin?
- Epidermis is water resistant (not waterproof)
- Excessive water gain prevented by intact epidermis
90
how is water lost via the skin?
via sweating or transpiration
91
when is water loss much more significant?
when there is epidermal loss eg in burns
92
name a ways the skin acts as protection
Physical barrier
93
what does the skin protect against?
Non-specific defence mechanism, protecting against:
- Microorganisms
- Chemicals
- Physical agents (mild trauma, water)
- Dehydration
94
what does melanin in the skin protect against?
against UV light
95
what in the dermis acts as protection? how?
- Sensory nerve endings in the dermis
1. Reflex (withdrawal) action to unpleasant or painful stimuli
2. Mediated by nociceptors and the spinal cord
3. Protects from further injury
96
what are the 4 functions of sebum?
- Sebum keeps hair soft and pliable
- Waterproofs the skin
- Prevents drying and cracking
- Bactericidal and fungicidal action - prevents infection
97
what creates the skins immune function?
- Epidermis contains Langerhans/dendritic cells – fixed macrophage which can phagocytose antigens and stimulate lymphocyte response
- Dendritic cells also present in dermis
98
what are the tactile repceptors in the epidermis called?
merkel cells
99
what 2 things create sensation for the skin? how?
- Few tactile receptors in epidermis – Merkel cells
- Nerve impulses generated in sensory receptors in dermis
- Transmitted to spinal cord by sensory nerves
- Impulses conducted to somatosensory cortex
100
how is calcium and phosphorus regulated by the skin?
7-dehydrocholesterol present in the skin (lipid)
Converted to Vitamin D (cholecalciferol) in the lower epidermis in response to UV exposure
(hydroxylated in liver and kidneys to become active)
Regulates calcium and phosphorus in the body
101
what are the 4 steps of wound healing?
1. Cut blood vessels bleed into the wound
2. Blood clot forms, and leukocytes clean wound
3. Blood vessels regrow, and granulation tissue forms
4. Epithelium regenerates, and connective tissue fibrosis occurs
102
how do cut blood vessels bleeding into the wound start healing?
Introduces clotting factors, leucocytes and antibodies into the wound
103
how does the formation of a blood clot contribute to wound healing?
- Temporary patch to edges of wound
- Acts as a barrier to prevent entry of pathogens
- Macrophages clean the wound of cellular debris
104
explain how the formation of new blood vessels and granulation tissue support wound healing (4)
- Cut blood vessels regenerate and grow into wound
- Granulation tissue grows deep in the wound – vascular connective tissue
- Macrophages remove clotted blood
- Fibroblasts produce new collagen fibres
105
explain how epithelial regeneration is the final step in wound healing (4)
- Division of epithelial cells at edge of wound results in epithelial regeneration of epidermis
- New epithelial cells migrate over wound
- Connective tissue replaced by fibrosis
106
what is a superficial sunburn charaterised by?
redness, pain, itching, mild oedema
107
what is a severe sunburn characterised by?
- can involve upper dermis (second degree/partial thickness)
- with blistering and more severe pain
108
what are the 6 types of skin on the fitzpatrick skin type scale?
1. light, pale white (always burns)
2. white, fair (usually burns, tans with difficulty)
3. medium, white to olive (burns midly, tans gradually)
4. olive, moderate brown (rarely burns, tans with ease)
5. brown, dark brown (very rarely burns, tans very easy)
6. black, very dark brown to black (never burns, tans very easily)
109
what type of follicle does asian hair grow from?
round hair follicle
110
what type of follicle does afro hair grow from?
oval to eliptical hair folicle
111
what is the hair growth rate of caucasian hair?
1.2cm/month
112
how many hairs are their on a blonds head?
~146,000
113
how many hairs are their on a black-haired peoples head?
~110,000
114
how many hairs are their on a brunettes head?
~100,000
115
how many hairs doesa redhead havr on their head?
~86,000
116
how many hairs are on the afro heads?
50,000-100,000
117
what is the growth rate of afro hair?
0.9cm/month
118
what is the growth rate of asian hair?
1.3cm/month
119
how many hairs are on the average asians hair?
80,000-140,000
120
who are more vulnerable to problems with thermoregulation?
extremes of age
121
when do most skin changes become obvious?
when middle age is reached
122
why do most skin changes become obvious around middle age?
- Skin repair processes take longer (reduced number and activity of stem cells)
- Reduced stem cell activity in epidermis
123
why are babies and childrens skin more prone to cracking?
Sebaceous glands less active
124
what makes babies and children more prone to hypothermia?
increased body surface area
125
what makes babies and children more prone to hyperthermia?
sweat glands less active
126
why do you get more oily skin at puberty?
Activity of sebaceous glands increases
127
why is the sweat more prone to odour once you reach puberty?
Apocrine glands start to secrete sweat
128
what are the 5 stages of acne?
- blackhead (open comedo)
- whitehead (closed comedo)
- pustule
- nodule
- cyst
129
why does hair turn white as you age?
hair follicles stop producing melanin
130
why do wrinkles deverlop as you age?
collagen fibres lose ability to bind water
131
why does hair thin as you age?
fewer active hair follicles
132
why is skin more prone to cracking as you age?
Sebaceous gland activity reduces
133
what does chronic UV exposure lead to?
- Can damage DNA in epidermal cells
- Accelerates ageing of skin
Involved in development of most skin cancers
- Occurs most frequently on head and neck
134
who are most at risk from damage due to chronic UV exposure?
pale-skinned people
135
what is the most common type of skin cancer?
basal cell carcinoma
136
what is the least dangerous type of skin cancer? why?
- basal cell carcinoma
- as it seldom metastasizes (i.e., spreads to other locations within the body)
137
where does basal cell carcinoma usually occur? how is it treated?
- on the face
- surgical remove of lesion
138
where does basal cell carcinoma originate?
- In stratum basale
- First appears as small, pearly white or pink, shiny elevation with small blood vessels running along it; later lesion may enlarge and develop central depression with pearly edge
139
where does squarmous cell carcinoma arise from?
Arises from keratinocytes of stratum spinosum
140
where do the lesions on squarmous cell carcinoma usually appear?
- scalp
- ears
- lower lip
- dorsum of hand
141
what is the progression of squarmous cell carinoma?
Early lesions are raised, reddened, scaly; later lesions form concave ulcers with elevated edges.
142
how is squarmous cell carinoma treated?
surgical removal of the lesion
143
true or false:
squarmous cell carcinoma cannot metastasize
false (it can)
144
what is the most deadly type of skin cancer? why?
- malignant melanoma
- due to agressive growth and metastasis
145
where does malignant melanoma arise from?
Arises from melanocytes, usually in a preexisting mole
146
what is maligant melanoma charcterised by?
change in mole diameter, color, shape of border, and symmetry
147
what improves survival rate for malignant melanoma?
Survival rate improved by early detection and surgical removal of lesion
148
what are the ABCDE's of recognising maligant melanoma?
A= Asymmetry
B= Border
C= Colour
D= Diameter
E= Evolving
149
what are the 13 ways in which skin can be an indicator of health?
- Colour & variation in presentation
- Condition/hygiene/bruising
- Temperature - hot/cold
- Dry/moist/wet/clammy
- Turgor (bounce)
- Perfusion: pink/blue/grey/white
- Capillary refill time
- Hair distribution
- Fat distribution
- Healing rates
- Lesions/rashes
- Scars
- Nail changes
