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Pharmacy > Structure (& Function) of the Skin > Flashcards

Structure (& Function) of the Skin Flashcards

1
Q

Function

A

protection, regulation and sensation

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2
Q

The integumentary system

A

Skin, cutaneous glands, fingernail, hair

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3
Q

what is the Skin

A

largest and fastest growing organ in body

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4
Q

Cutaneous glands

A

sebaceous (sebum) and sweat glands

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5
Q

Fingernails

A

densely packed cells covered in keratin

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6
Q

Hair

A

pigmented filament (mostly keratinised cells)

Part of the integumentary system

Hair grows in the dermis from the hair follicle (from downward extension of epidermis)

Growth of hair is like skin: keratinocytes get pushed up, become flattened, dead, keratinised cells

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7
Q

Small muscles (arrector pili) contract when

A

you experience physical/ emotional changes to give you goosebumps

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8
Q

Two types of skin on the body

A

hairy and glabrous (non-hairy)

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9
Q

Hairy skin

A

covering more than 90% of the body. Hair contribute to tactile sensations, forms part of our social interaction and can detect foreign objects

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10
Q

Glabrous skin

A

mainly on palms and soles of feet. Specialised nerves to detect tactile details. Thicker than hairy skin.

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11
Q

Skin-function

A

Protection (against external environment including invasion from bacteria)

Thermoregulation
Humidity control
Produces vitamin D

Viruses, bacteria and fungi live on your skin (ecosystem)! Demodex

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12
Q

Stratified epithelium

A

(usually thinner than dermis)

Outer layer of skin with no
blood vessel supply (squamous epithelium receives blood by diffusion)

Layers (strata) of keratinocytes. Continuous cycle of cell division and death

Also contains melanocytes, Merkel cells and Langerhans cells
30-45 days for basal cells to mature and migrate to top of epidermis

Production of keratin

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13
Q

Basement membrane separates

A

the epidermis and dermis-
connection between the two allows cells and bioactive molecules to move between the two regions

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14
Q

Stratum corneum

A

flat dead keratinocytes and cross-linked keratin fibres (squamous cells) protect body from water loss. Often described as ‘bricks’ (corneocytes) and ‘mortar’ (intercellular lipids). Loss of cells from this layer (desquamation) causes barrier to become weak (entry point for irritants)

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15
Q

Stratum lucidum

A

rows of dead keratinocytes only in glabrous skin. Lipid-rich eleidin keeps out water

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16
Q

Stratum granulosum

A

mostly mature keratinocytes migrating from spinosum, keratohyalin granules and lamellar bodies (also to waterproof skin)

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17
Q

Stratum spinosum

A

mature keratinocytes linked by desmosomes producing keratin. Also contains Langerhans cells (protection form microbes)

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18
Q

Stratum basale

A

deepest layer. Basal cells push older cells up. New keratinocytes made.
Also contains melanocytes (skin pigment)

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19
Q

corgis lick grandpas saggy bums - make up the epidermis

A

stratified corneum, Stratum lucidum, Stratum lucidum, Stratum granulosum, Stratum spinosum, Stratum basale

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20
Q

Dermis Two parts

A

papillary (20% of dermal thickness) and reticular (80% of dermal thickness)

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21
Q

Dermis- Papillary

A

mostly loose connective tissue some elastic fibres, capillary loops and nerves

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22
Q

dermis-Reticular

A

dense irregular connective tissue containing collagen fibres, elastin, proteoglycans and glycosaminoglycans

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23
Q

Fibroblasts and keratinocytes

A

principal cell of dermis. Production of collagen, elastic and reticular fibres and extracellular matrix

Cells of the dermis

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24
Q

Adipocytes

A

Cells of the dermis

fat cells (insulation, energy storage and wound healing)

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25
Mast cells
Cells of the dermis inflammatory cells that help with collagen remodelling and wound healing
26
Myofibroblasts
Cells of the dermis rich in smooth muscle actin and myosin (contractile cells)
27
Myoepithelial cells
Cells of the dermis cells in sweat glands
28
Keratinocytes
Make up more than 90% of the cells in the epidermis Essential for stratification and forming protective barrier Changes in structure and function as you move towards outer layer
29
Keratins
80% of internal cell structure of differentiated keratinocytes bundles are major component of the cytoskeleton of the keratinocytes Network of fibre bundles extending from periphery to nucleus Bundles composed of keratin subunits wrapped around each other (coil). Different types of keratin expressed Contribute to structural integrity of epidermis (dissipate force) Few drugs can disrupt keratin intermediate filaments (though mutations in the keratin genes can lead to weak filaments)
30
Desmosomes
anchors (cells to each other and to basement membrane Multiprotein complexes important in adhesion and signalling connect cells to each other (junctions) via cadherin proteins. Also provide strength as they link intracellularly (through the filaments in the cytoskeleton) Loss of connection can cause significant issues e.g., skin blistering (pemphigus- an autoimmune disease)
31
Lamellar granules-Also known as: lamellar bodies, membrane-coating granules, keratinosomes, Odland bodies
help form lipid protective barrier Produced by keratinocytes (also found in lungs) Round/ oblong in shape (though some say they’re branched) approx. 300-400nm width and 100-150 nm length Secretory organelles: contain glucosylceramides, lipids, enzymes and other proteins. These are required for desquamation (skin shedding) Skin function: help form the impermeable lipid-containing barrier Abnormalities can cause eczema and other skin conditions
32
Hemi-desmosomes
anchors (cells to each other and to basement membrane Multiprotein complexes important in adhesion and signalling connect keratinocytes to the basement membrane via integrin receptors and also contribute to strength Loss can again lead to skin blistering (tissue separation)
33
Why does our skin not constantly rupture from the mechanical forces of the outside world?
Keratinocytes >70 times stiffer than other cell types (even after they die!) Due to their cytoskeleton and keratin filaments
34
Melanocytes
Produce melanin (skin colour) and protects against UV radiation while supporting the immune system. Found in bottom layer of epidermis. transfer melanosomes to keratinocytes (through dendrites)
35
Langerhans cells
also known as dendritic cells and contain Birbeck granules (rod shaped with function not clear). Found throughout epidermis and support immune system.
36
Merkel cells
oval shaped and responsible for light touch and sensation through their connection to nerve fibres
37
Melanosomes
formed in melanocytes and contain melanin
38
Epidermal melanin unit
anatomical relationship between melanocytes and keratinocytes (each melanocyte is in contact with approx. 40 keratinocytes)
39
Hyperpigmentation- causes
increased melanin production or increased number of melanocytes (less common as melanocyte number is approx. similar in all individuals)
40
Hyperpigmentation-epidermal
too much melanin or too many melanosomes transferred
41
Hyperpigmentation- dermal
melanin crosses damaged basement membrane. Deeper and harder to treat
42
Hyperpigmentation-Treatment
varied from photoprotection to prevent new spots to inhibitors of melanin production
43
Merkel cells: allodynia
Hypersensitivity to touch which can manifest as pain A type of neuropathic pain Everyday tasks become difficult, e.g., combing hair, putting on a t-shirt, even temperature changes Causes: many e.g., diabetes, fibromyalgia, migraines
44
Langerhans cells and immunity
Dendritic cells: ‘sense’ by extending dendrites through intercellular tight junctions towards stratum corneum Able to interpret the external environmental threats (inflammation or tolerance) Non-dangerous: coordinate immune tolerance (no immune activation) Dangerous: work with keratinocytes to instruct T lymphocytes to mount a response As they interact with keratinocytes to ‘activate’, any damage to keratinocytes could affect immune response
45
Langerhans cell histiocytosis
Buildup of excess immature Langerhans cells form granulomas (tumors) in skin and other organs. Stimulus for excess proliferation unknown Cancer? Labelling controversial Rare (1 in 5 million) Can severely affect the immune system (can involve multiple organs and can be fatal) Treatments: depends on severity from topical to chemotherapy and surgery
46
Shaft
Hair exposed on skin surface
47
Hair root
Rest of the follicle
48
Hair bulb
Bulge at the base of the hair root (contains a layer of basal cell: ‘hair matrix’ which form the hair)
49
4 different hair growing stages
anagen: growing phase catagen: transition phase telegen: resting phase exogen: shedding phase
50
hair- function
protect from sun, prevent heat loss, trap particulates (hair in nose and ears), prevent sweat from running into eyes (eyebrows) Much more sensitive than skin to changes in environment (see arrector pili muscle) Hair grows at approx. 0.3 mm a day Approx. 50 hairs lost per day Like skin melanin gives it colour (melanin production decreases with age: grey hair)
51
Alopecia and baldness
genetic sensitivity to androgen hormone dihydrotestosterone (DHT): less blood flow at hair follicle
52
Male pattern baldness
mutation on X chromosome (women can be carriers!)
53
Nails - anatomical
Part of the integumentary system Nail body formed on the nail bed (rich in blood vessels making the nail appear pink) Lunula: Crescent shape at the base of the nail Nail folds anchor the nail to the body Keratin-rich and densely packed dead keratinocytes
54
nail function
protective as they are the furthest extremities that experience the maximum mechanical stress Infections and trauma to nail easily seen Changes in shape could be a symptom of something else (e.g., iron deficiency)
55
Exocrine glands
excrete substances via a duct
56
Glands of the integumentary system
sudoriferous glands, sebaceous glands, ceruminous glands, mammary glands (all exocrine
57
Subcategories of exocrine glands; Structure:
Simple- a single duct Compound- multiple, branched ducts
58
Subcategories of exocrine glands; Secretion method
Merocrine- most common. Excretion via exocytosis Apocrine- cell membrane buds off into the duct Holocrine- cell membrane ruptures to release the product
59
Sweat glands
eccrine (open directly onto surface of skin) and apocrine (opens into hair follicles)
60
Eccrine glands
cover most of the body. Opens to epidermal surface Starts at birth Merocrine excretion Thermoregulatory function and ion excretion 500-750mL water lost per day
61
Apocrine glands
mostly where hair follicles are abundant (scalp, beard, armpits, groin) Active from puberty (linked to emotions: pheromone excretion) Viscous and protein rich
62
Oil-producing glands
release sebum into follicular duct
63
sebum
Sebum coats, moisturises and protects skin Several types of lipids. 57.5% triglycerides and fatty acids 26% wax esters 12% squalene
64
Ceruminous glands
Modified apocrine glands: found in the external auditory canal Together with sebaceous glands, produce cerumen (ear wax). Important protective role but also trap and take particulates away for tympanic membrane (eardrum) 1000-2000 ceruminous glands in a normal ear
65
Mammary glands
Type of apocrine gland Production of milk after birth2 (in both men and women) on either side of the front of the chest wall Semicircular when young but begin to lose shape Each weighs 500-1000g
66
Mechanoreceptors; sensory receptors
Respond to physical changes Hair: light touch Meissner’s corpuscle: indentation and slipping Pacinian corpuscle: vibrations Merkel’s disk: texture Ruffini corpuscle: stretch
67
Thermoreceptors : sensory receptors
Body has both cold receptors (sensing 25-30°C) and warm receptors (sensing 30-46°C) When changes in temperature occur, the opposite receptor stops discharging Some proteins involved are known (TRPV1, TRPM3, ANO1 etc.) but largely mechanisms are unknown
68
Nociceptors
Signal pain related to pressure, temperature and chemicals The receptors only signal when tissue damage occurs- inflammatory markers caused by tissue damage binding to the receptors are the trigger TRP (transient receptor potential) ion channels: one of the ion channel families present on nociceptor neurons A-delta fibres: relay pain information related to painful temperatures, uncomfortable pressures, and chemicals C fibres: relay pain information related to thermal and mechanosensitive pain

Pharmacy (15 decks)

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