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B9W1 > BIOLOGY OF SKIN > Flashcards

BIOLOGY OF SKIN Flashcards

1
Q

what are some functions of the skin?

A

physical barrier to water, chemicals, particles and infectious agents
temperature regulation
vitamin D synthesis
immune defence
protection against UV
site of pathology
specialised appendages e.g. skin and nails

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2
Q

what are the 3 layers of the skin?

A

epidermis
dermis
hypodermis

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3
Q

what is the histology of the epidermis?

A

continuous sheets of stratified squamous epithelium

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4
Q

what is the histology of the dermis?

A

a thick layer of dense, irregular connective tissue

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5
Q

what is the histology of the hypodermis?

A

loose connective tissues with adipose cells

has skin appendages e.g. hair follicles

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6
Q

describe the main differences between thick and thin skin?

A

thin skin is more abundant
thick skin has a much more prominent stratum corneum
thick skin doesnt contain hair or sebaceous glands like thin skin
thick skin may contain a stratum lucidum unlike thin skin

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7
Q

outline the structure of the epidermis?

A 
stratum corneum
stratum lucidum
stratum granulosum
stratum spinosum
stratum basale
basement membrane
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8
Q

describe the stratum basale?

A

this layer is on top of the basement membrane and is a single layer of cuboidal cells with stem like properties.

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9
Q

describe the stratum spinosum?

A

the cuboidal cells from the stratum basale migrate upwards, proliferating to form the stratum spinosum which is a few cells thick and is characterised by irregular cells and tight junctions forming tonofibrils

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10
Q

what are tonofibrils?

A

a tiny fibre occurring in bundles in the cytoplasm of cells that lie in contact

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11
Q

describe the stratum granulosum?

A

cells from the stratum spinosum migrate upwards again and differentiate to develop keratohyalin granules and lamellar bodies

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12
Q

what are keratohyalin granules?

A

granules containing proteins which bind to and aggregate keratin filaments

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13
Q

what are lamellar bodies?

A

they store and secrete lipids- important for keeping skin hydrophobic

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14
Q

describe the stratum corneum?

A

the cells from the stratum lucidum/stratum granulosum migrate upwards and undergo apoptosis to form the tough surface layer of the skin

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15
Q

what do keratinocytes do?

A

they produce keratin
the degree of keratinisation increases with increased proliferation and differentiation as you move up towards the epidermis

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16
Q

what do melanocytes do?

A

they produce melanin which is responsible for skin pigmentation and protection against UV damage

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17
Q

what do melanosomes do?

A

they are transferred from melanocytes into keratinocytes and contain melanin

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18
Q

what are rete ridges?

A

extensions of the epidermis into the dermal layer- forms the undulating structure of the epidermis with the dermal papillae

19
Q

what are dermal papillae?

A

protrusions of dermal connective tissue into the epidermal layer- forms the undulating structure of the epidermis with the rete ridges

20
Q

why is the undulating structure of the epidermis important?

A

it creates a greater surface area and increases attachment between the epidermis and dermis which prevents mechanical damage

21
Q

how does blood flow nourish the epidermal layers?

A

The epidermis does not contain blood vessels; instead, cells in the deepest layers are nourished by diffusion from blood capillaries that are present in the upper layers of the dermis and enter through the dermal papillae

22
Q

what is the structure of the dermis?

A

its formed of the papillary dermis and the reticular dermis

23
Q

whats the papillary dermis?

A

a thin layer underlying the epidermis made up of loose connective tissue with fine collagen and elastic fibres

24
Q

whats the reticular dermis?

A

a thick layer making up most of the dermis formed from dense, irregular connective tissue containing thick collagen bundles
contains fibroblasts, immune cells, blood vessels, nerves and skin appendages

25
Q

what is the hypodermis?

A

aka subcutaneous layer

the layer under the dermis thats composed of mature adipose tissue

26
Q

whats the function of the hypodermis?

A

insulation, protection and energy store

27
Q

what are the main skin appendages?

A

hair
nails
glands

28
Q

what are the 3 glands found in the skin?

A

sebaceous glands
eccrine sweat glands
apocrine glands

29
Q

what is the nail plate?

A

a hard keratinised plate at the distal end of each digit

30
Q

describe the structure of hair follicles?

A

at the base, there is a bulbous expansion containing the hair papilla where epithelial cells divide and develop
the hair shaft grows upwards
the 3 layers of the hair from inwards to outwards are the medulla, cortex and cuticle

31
Q

what are sebaceous glands?

A

glands that secrete sebum (lipid substance) to keep hair soft, supple and waterproof
they grow and burst to release their contents into the hair folllicles

32
Q

what are eccrine sweat glands?

A

tubular glands in the reticular dermis that secrete sweat directly onto skin surfaces by merocrine secretion

33
Q

what are apocrine glands?

A

coiled tubular structures in the reticular dermis localised to the axillae, mammary and groin that become activated during puberty. they secrete a substance containing pheromones and cause body odor upon reaction with skin bacteria

34
Q

how do superficial wounds heal?

A

the epidermis can regenerate from the basal layer

35
Q

how do wounds extending into the dermis heal?

A

haemostasis, inflammation, fibroplasia, angiogenesis, epithelisation and remodelling

36
Q

what is haemostasis?

A

formation of a fibrin clot to stop blood loss

37
Q

what is fibroplasia?

A

fibroblasts laying down new collagen

38
Q

what is angiogenesis?

A

formation of new blood vessels

39
Q

what is epithelialisation?

A

migration and mitosis of keratinocytes from wound edges to form a new basal layer

40
Q

how do deepest wounds heal?

A

if the dermis and deep parts of appendages are destroyed then spontaneous healing is not possible

41
Q

what is an ulcer?

A

loss of epidermis and papillary dermis

42
Q

what is a bruise?

A

leakage of blood into the dermis

43
Q

what is a callus?

A

hyperplasia of epidermis following pressure

B9W1 (8 decks)

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