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Dermatology > Physiology > Flashcards

Physiology Flashcards

1
Q

What are skin appendages

A

Addition to the skin layers

Includes: hair follicles, melanocytes, glands etc

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2
Q

What are Blaschko’s lines

A

Show the developmental growth pattern of skin

Does not follow vessels or nerves

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3
Q

What can happen if there is a malformation in a Blaschko line

A

Disease can present in the segment that that line covers

Allows you to determine that the skin abnormality was developmental

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4
Q

What does the skin consist of

A

Epidermis = 5 layers
Dermo-epidermal junction
Dermis = connective tissue
Sub-cutis = mostly fat

Also appendages - nails, hair etc

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5
Q

What is the function of the dermis

A

Structural rigidity
Blood vessels, lymphatics, glands and follicles are found here
Also contains numerous nerve endings - sensory functions

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6
Q

Are the epidermal layers the same across the whole body

A

NO
They vary depending on functions
E.g. Thicker keratin layer on palms and soles
Differences in number of hair follicles and sweat glands

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7
Q

What controls epidermal turnover

A

Growth factors
Cell death
Hormones

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8
Q

What can occur if there is loss of control of epidermal turnover

A

Skin cancer

Psoriasis - cycle is accelerated

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9
Q

Describe the basal layer (stratum basal)

A

4th layer of epidermis Usually one cell thick
Small cuboidal cells
Lots of intermediate filaments
Highly metabolically active - divide all the time
Contains the Merkel Cells

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10
Q

Describe the prickle cell layer (stratum spinosum)

A

3rd layer of epidermis Large polyhedral cells
Lots of desmosomes - connections
Move up through layers erratically

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11
Q

Describe the structure of the granular layer

A 
2nd layer of epidermis 
2-3 layers of flatter cells 
Large granules containing structural filaggrin and protein 
Have lamellar bodies 
High lipid content 
Cell nuclei lost
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12
Q

What is the function of the granular layer

A

Goes on to form the ‘glue’ that seals the skin
The cells shrink and die, releasing their granules
Lipids and proteins released seal the skin

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13
Q

What is the function of the keratin layer

A

Forms a tight waterproof barrier

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14
Q

Describe the structure of the keratin layer (stratum corneum)

A

Made up of overlapping cell remnants - corneocytes
Cells have lost their nucleus and cytoplasm
80% keratin and filaggrin

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15
Q

What causes warts

A

Infection that affects the keratinocytes
Viruses infect the cells and cause increased proliferation
Tries to push infected cells out but just forms a thickened layer on top = wart

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16
Q

What is the function of melanocytes

A

Creates melanin pigment by converting tyrosine - occurs in melanosomes
This absorbs light so works as a natural sun protection
Forms a cap over the nucleus to protect DNA

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17
Q

Describe the structure of melanocytes

A

Have long dendrites
Forms synapses with the basal layer to produce pigment
Found in the keratin layer

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18
Q

What causes melanin to be produced

A

Exposure to UV light

Hormones

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19
Q

What causes vitiligo

A

T cells attack melanocytes
Causes loss of pigmentation
Autoimmune condition

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20
Q

What is albinism

A

Genetic condition

Melanocytes don’t produce pigment

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21
Q

What is Nelson’s syndrome

A

A disorder where melanin stimulating hormone is produced in excess by the pituitary gland
Causes hyperpigmentation
Sometimes occurs as result of a tumour

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22
Q

What is a tumour of the melanocytes called

A

Melanoma

Malignant

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23
Q

What is the function of Langerhan’s cells

A

Part of skin immune system
Pick up antigens in skin and transport them to the lymph nodes
Act as antigen presenters

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24
Q

Describe Merkel cell cancer

A

Malignant transformation of the merkel cells

Very dangerous cancer with high mortality - 90%

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25
Describe the structure of a pilosebaceous unit
Has an epidermal component plus dermal papilla Contains specialised keratins Has an adjacent sebaceous gland - moisturises skin Melanocytes above papilla give hair colour
26
Which hormones can influence hair growth
Androgens | Thyroxine
27
What is Virilisation
Excess hair growth in male pattern due to excess androgen | May be due to an androgen-producing tumour
28
What is alopecia areata
Autoimmune condition where T lymphocytes attacks the hair follicle Causes hair loss
29
Describe the structure of the nails
Contains specialised keratins Come from specially differentiated skin cells Nail plate of hard keratin sits on nail bed Matrix contains dividing cells which grow the nails Firm and rigid If bed is damaged it is often irreversible and the nail will continue to grow in a abnormal way
30
What can happen if the DEJ fails
The skin can slip, split and blister
31
What is Bullous Pemphigoid
A skin condition where antibodies form against parts of the dermo-epidermal junction Causes large blisters Seen in elderly patients
32
What is epidermolysis bullosa
A genetic condition caused by a mutation in one of the proteins of the DEJ Skin is extremely fragile and blisters/falls off easily Can be life threatening
33
What makes up the dermis
Ground substance Cells: mainly fibroblasts (connective tissue), macrophages, mast cells, lymphocytes and langerhans cells Fibres: collagen and elastin - given tensile strength and elasticity Muscles, blood vessels, lymphatic system and nerves
34
Describe the fibres found in the dermis
Most are collagen which provides strength and support Elastin provides skin elasticity Becomes less functional as we age
35
What is photo ageing
Exposure to UV light can attack the fibres in the dermis and cause ageing - more wrinkles etc Smoking can also have this effect
36
Why does the skin have more blood supply than necessary
Partly due to role in thermoregulation - arteriovenous anastomoses are particularly important in this
37
What is an angioma
Benign overgrowth of blood vessels | Presents as large purple patches
38
Describe the nerves within the skin
Somatic sensory - free nerve ending for pain and heat - Pacinian (pressure) receptors - Meissners (vibration) corpuscles Autonomic nerves - for blood vessels, nerves and glands
39
What is the function of the sebaceous gland
Lubricate and moisturise hair and skin | May offer immune protection by preventing bacteria from entering the follicle
40
What can cause acne
Overproduction of sebum by sebaceous glands Blocks the pores Occurs during puberty due to hormones
41
Describe apocrine sweat glands
Part of pilosebaceous unit - open into hair follicle Activated during puberty - androgen dependent Produce oily fluid that starts to smell Found in axillae, nipple and genitals
42
What is the function of eccrine sweat glands
Produce sweat to cool us down - regulate heat and salt loss Moistens palms On the soles they improve grip
43
Where are eccrine glands found
Over the whole body Axilla palms and soles in particular Not in lips and genitals
44
What are the functions of the skin
``` Barrier Metabolism and detoxification Fluid balance Thermoregulation Immune defense Communication - sensory function ```
45
What is toxic epidermal necrolysis
Drug causes failure of cohesion between the epidermis and dermis - usually across 90% of the body Increases infection risk, pain, loss of moisture and protein
46
What does the skin act as a barrier against
Friction, mechanical trauma, UV Irritants, allergens, toxins Bacteria, viruses, fungi
47
What is the function of vitamin D
Calcium absorption
48
What can vitamin D deficiency cause
Rickets in children | Osteoporosis in the elderly
49
How does the skin help with thermoregulation
Has thermoreceptors This will induce behavioural changes Blood vessels dilate or constrict to control heat Sweating cools us down
50
How does the skin act in immune defence
Langerhan's and T cells are important | An intact dermis & epidermis are key
51
What are the sensory functions of the skin
Touch, pressure and vibration Pain and itch Temperature
52
The epidermis is composed primarily of which cell type
Keratinocytes
53
Where are keratinocytes produced
In the basal layer of the epidermis | They then undergo a process of migration starting from the basal layer, upwards to the stratum corneum
54
What are the 5 layers of the epidermis from top to bottom
``` Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basal ```
55
What are the two main layers of the dermis
Papillary dermis - loose CT and lots of cells | Reticular dermis - denser CT and fewer cells
56
Do people with darker skin tones have more melanocytes
No - we all have the same number | Darker skin has larger melanosomes containing more melanin and the melanosomes degrade slowly compared to fair skin
57
How does the keratin layer differ in dark skin
Keratin layer in darker skin tones is more compact
58
Why are those with darker skin at higher risk of keloid scars
Larger and more numerous fibroblasts | The higher fibroblast activity increases keloid risk
59
List the 3 phases of the hair cycle
Anagen – growth phase, 2-7years, most hairs in this phase 85% Catagen – transitional stage, 2 weeks, hair detaches from the blood supply Telogen - approx 3 months, hair falls out, ‘released from the follicle’ and new hair grows behind it
60
Which parts of the body lack sebaceous glands
Palms and soles
61
Name the muscles associated with hair follicles
Arrector pili | Can pull the hair perpendicular to the skin during cold / fright ( goose bumps)
62
Meissener's corpuscles detect what
Tactile sensation | Found in dermis
63
Pacinian corpuscles detect what
Deep pressure | Found in dermis
64
What is primary intention healing
When the edges of a wound are brought together - leads to rapid healing Usually with stitches etc
65
What is healing by secondary intention
Wound is left open and heals from the bottom up Inflammation then granulation then tissue remodelling Used for for larger wounds that are too tight to stitch, or areas where direct closure would cause significant distortion
66
Describe the different degrees of burn
First degree: epidermis only. Second degree/Partial thickness: epidermis and dermis. Third degree/ Full thickness: extends beyond dermis

Dermatology (14 decks)

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