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Flashcards in Physiology Deck (51):
1

What are skin appendages

Addition to the skin layers
Includes: hair follicles, melanocytes, glands etc

2

What are Blaschko's lines

Show the developmental growth pattern of skin
Does not follow vessels or nerves

3

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

Disease can present in the segment that that line covers
Allows you to determine that the skin abnormality was developmental

4

What does the skin consist of

Epidermis = 4 layers
Appendages - nails, hair etc
Dermo-epidermal junction
Dermis = connective tissue
Sub-cutis = mostly fat

5

What is the function of the dermis

Structural rigidity
Vessels, glands and follicles are found here

6

Are the epidermal layers the same across the whole body

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

7

What controls epidermal turnover

Growth factors
Cell death
Hormones

8

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

Skin cancer
Psoriasis

9

describe the basal layer

Usually one cell thick
Small cuboidal cells
Lots of intermediate filaments
Highly metabolically active - divide all the time

10

Describe the prickle cell layer

Large polyhedral cells
Lots of desmosomes - connections
Move up through layers erratically

11

Describe the structure of the granular layer

2-3 layers of flatter cells
Large granules containing structural filaggrin and protein
Have lamellar bodies
High lipid content
Cell nuclei lost

12

What is the function of the granular layer

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

13

What is the function of the keratin layer

Forms a tight waterproof barrier

14

Describe the structure of the keratin layer

Made up of overlapping cell remnants - corneocytes
80% keratin and filaggrin

15

What causes warts

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

16

What is the function of melanocytes

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

17

Describe the structure of melanocytes

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

18

What causes melanin to be produced

Exposure to UV light
Hormones

19

What causes vitiligo

T cells attack melanocytes
Causes loss of pigmentation
Autoimmune condition

20

What is albinism

Genetic condition
Melanocytes don't produce pigment

21

What is Nelson's syndrome

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

22

What is a tumour of the melanocytes called

Melanoma
Malignant

23

What is the function of Langerhan's cells

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

24

Describe Merkel cell cancer

Malignant transformation of the merkel cells
Very dangerous cancer with high mortality - 90%

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
Similar structure to a hair bulb - nail bed
Firm and rigid
If 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, macrophages, mast cells, lymphocytes and langerhans cells
Fibres: collagen and elastin
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

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
Activated during puberty - androgen dependent
Produce oily fluid that starts to smell

42

What is the function of eccrine sweat glands

Produce sweat to cool us down
Moistens palms
On the soles they improve grip 56

43

Where are eccrine glands found

Over the whole body
Axilla palms and soles in particular

44

What are the functions of the skin

Barrier
Metabolism and detoxification
Thermoregulation
Immune defence
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