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Human Epithelial Biology > Introduction to the Integumentary System > Flashcards

Introduction to the Integumentary System Flashcards

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1
Q

What is the function of the skin?

A
  • Secretion e.g. sweat and smell
  • Absorption
  • Protection
  • Sensory
  • Appearance
  • Body temperature control
  • Blood reservoir
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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 are the characteristics of the epidermis?

A
  • Epithelial
  • Non-vascular
  • Protective
  • Outermost layer
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4
Q

What are the characteristics of the dermis?

A
  • Vascular
  • Fibrous connective tissue
  • Epithelial gland structures e.g. sebaceous glands and sweat glands
  • Smooth muscle
  • Sensory
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5
Q

Describe the vasculature of the dermis

A

It is capillaries which have extended upwards from large blood vessels within the hypodermis
Provides skin pigmentation

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6
Q

Function of connective tissue in the dermis

A

holds the skin together

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7
Q

Function of smooth muscle in the dermis

A

attached to smooth muscle which when it contracts causes goose bumps
Provides the pungent smell of animals as a defence mechanism

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8
Q

What is the sensory purpose in the dermis?

A

Allows the detection of pressure, temperature etc.

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9
Q

What are the characteristics of the hypodermis?

A
  • Not skin
  • Protective
  • Adipose and loose
  • Connective tissue
  • Vascular
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10
Q

What is the function of connective tissue in the hypodermis?

A

Strength

A base structure for the dermal attachment

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11
Q

What is the 5 layers of the epidermis?

A
  • Stratum basale
  • Stratum spinosum
  • Stratum granulosum
  • Stratum lucidum
  • Stratum corneum
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12
Q

Describe the stratum basale

A
  • Bottom layer of the epidermis
  • Contacts the dermis
  • made mainly of keratinocytes
  • Has specialised epithelium and immune cells
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13
Q

Describe the stratum spinosum

A

Has weakly differentiated keratinocytes which express the karatin fibres and lamellar bodies

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14
Q

What are keratohyalin?

A

Keratinocytes which have gone to their next stage of differentiation

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15
Q

Describe the stratum granulosum

A

Keratohyalin and a hard protein envelope form

Lamellar bodies release lipids and cells die

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16
Q

Describe the stratum lucidum

A

Dead cells containing dispersed keratohyalin’s

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17
Q

Describe the stratum corneum

A

Dead cells with a hard protein envelope

The cells contain keratin and are surrounded by lipids

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18
Q

What is a keratinocyte?

A

A cell which is involved in wound healing due to its stem cell properties
Primary cell of the epidermis
It produces keratin

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19
Q

Where are keratinocytes formed?

A

Stratum basale

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20
Q

How do keratinocytes move to the surface

A

mitosis

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21
Q

How are keratinocytes connected to one another?

A

desmosomes

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22
Q

When is keratin produced?

A

as cells migrate

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23
Q

what is the function of filaggrin?

A

causes keratin to dimerise (keratinisation)

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24
Q

If a wound bleeds what does this mean and what is the function of keratinocytes?

A

You have cut the dermis

Keratinocytes heal the wound and they recruit immune cells to remove pathogens

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25
How are the squamous epithelium made?
Through the binding of keratin and filaggrin
26
Within normal cells, what is the process of skin production
1) Within the stratum granulosum - profilaggrin is cleaved to small peptides 2) Filaggrin binds to keratin fibres causing cell flattening to squamous epithelium 3) Stratum corneum - keratin fibres tightly bound. Filaggrin degrades to hydrophobic amino acids and maintains skin moisture. 4) Intact barrier - prevention against pathogens
27
Within aczema patients, how is skin formed?
1) Filaggrin mutations reduce the amount of filaggrin in the skin 2) Keratin fibres do not form a dense, flattened barrier 3) Cracks in the skin barrier enable allergens and pathogens to penetrate dermis 4) Inflammation occurs causing irritation in the skin and other organs
28
How is eczema linked to asthma?
Due to the breakage in the skin, there is a higher chance of pathogens entering the skin
29
What can be used to reduce eczema-induced asthma?
Barrier creams
30
Function of melanocytes
produce pigment, melanin
31
How does melanin work?
Within the stratum basale, transfer of melanin to keratinocytes causes melanin accumulation to protect the nucleus from UV
32
What are merkel cells?
Neuroepithelial cells associated with sensory nerve endings
33
What receptor does merkel cells act on?
Mechanoreceptors
34
What is the neurotransmitter of merkel cells?
Glutamate
35
What are merkel cells sensitive to?
shear and pressure through desmosomal junctions
36
What are langerhan's cells?
Epidermal dendritic cells
37
where are langerhan's cells made?
Bone marrow
38
Where do langerhan's cells migrate to?
Epidermis
39
What is the function of langerhan's cells?
Function as macrophage-like antigen presenting cells (activate T cells) - the skin's immune cell
40
How is melanin made?
Conversion of tyrosine using tyrosinase
41
Where is melanin made?
In melanocytes
42
What are the two products of melanin production?
Eumelanin (black) | Pheomelanin (red)
43
When are you likely to express eumelanin?
If you express dopaquinone
44
When are you likely to express pheomelanin?
If you do not express dopaquinone
45
Three types of UV
UVA UVB UVC
46
Describe UVB and UVC
- short wavelength - extremely damaging - causes sunburn - low dose
47
Describe UVA
- longer wavelength - penetrates dermis - promotes tanning
48
Why is UVB and UVC dangerous?
The short wavelength means that it can penetrate the epidermis and occasionally the keratinocytes - can be carcinogenic
49
Describe the process of tanning
UVA -> DNA damage in Dermis (mild) -> Epithelial DNA damage response -> alpha-melanocyte stimulating hormone (alphaMSH) synthesised and released from the damaged dermal cells -> Diffusion into the melanocortin receptor, MC1R -> Transcription factor (MITF) increases expression of tyrosinase -> eumelanin synthesis by melanocytes
50
When is someone a darker colour?
When eumelanin > pheomelanin
51
Why do tan's fade?
Eumelanin is transported to surrounded keratinocytes and your keratinocytes are constantly regenerating
52
what is MC1R
a G protein coupled receptor which is expressed in melanocytes cell membranes
53
Where is alphaMSH produced?
the dermis
54
What other factors dictate colouring?
``` Bruising Jaundice Nervous Erythema Erythema Carotene ```
55
What is carotene?
Produced by diet - carrots and oranges | Deposited into the stratum corneum and fatty tissue of the hypodermis
56
What is erythema?
Re-direction of blood flow to superficial skin capillaries due to irritation, infection or part of a response to fever
57
What is nervous erythema?
Blushing | Catecholamine induced vasodilation which pushes blood to the skin surface in well perfused areas of the skin
58
What is jaundice?
A liver disease - releases bile pigments to blood which are deposited in the hypodermis and cornea of the eye
59
What causes bruising?
Damage to capillaries of dermis and hypodermis causing deposits of bilirubin in skin
60
What two layers provides dermal strength?
Papillary and Reticular
61
Describe the papillary layer
thin, connective tissue with blood vessels
62
Describe the reticular layer
dense, irregular connective tissue with collagen and elastin
63
Why is the dermis multifunctional?
contains sweat glands, hair follicles, vascular and sensory components
64
What cell types are in the dermis?
- Epithelial cells - Fibroblasts - Macrophages - Mast cells - WBC's - Smooth muscle (Arrector Pili)
65
Characteristics of an endocrine secretion
Secretion through exocytosis Using accompanied by fluid movement Do not lose cytoplasm
66
Example of an endocrine secretion
Fluid secreting cells in a sweat gland
67
Characteristics of an apocrine secretion
lipid, protein and amino acid laden secretion Contribution to scent cells lose cytoplasm but they do not die and regenerate
68
Example of apocrine secretion
Mammary glands | Sweat glands
69
Characteristics of a holocrine secretion
Lipid, protein and amino acid secretions - often waxy Thicker secretion responsible for pungent scent Entire cell ruptures Continual cell growth and replacement
70
What are the two major components of the eccrine sweat glands?
Secretory coil | Re-absorptive duct
71
What happens in the secretory coil?
1) CFTR driven Cl- secretion (blood to lumen) 2) Na+ follows via paracellular route 3) Causes an isotonic solution 4) Water moves into duct via aquaporin channels
72
What happens in the re-absorptive coil?
1) ENaC driven Na+ absorption 2) Cl- moves through CFTR or paracellular channels to the blood 3) No aquaporins for water movement 4) Hypotonic sweat produced
73
Where are apocrine glands found?
In armpits and anogenital regions
74
Where do the apocrine glands empty?
Into hair follicles and mix secretions with sebaceous oils and other secretions on the skin surface
75
Where do sebaceous glands empty?
Into a hair follicle shaft
76
What is the function of the sebaceous glands?
Waterproofs and lubricates the skin and hair
77
What does sebaceous glands secrete?
acid mantle
78
Condition associated with sebaceous glands?
Acne
79
What are ceruminous glands?
modified apocrine gland
80
Where are ceruminous glands secreted?
onto guard hairs in the ear, producing ear wax
81
What do mammary glands produce?
Milk
82
What is a mammary gland?
Either a modified apocrine gland or sebaceous gland
83
What are the 5 types of skin glands?
- Eccrine sweat glands - Apocrine glands - Sebacous glands - Ceruminous glands - Mammary glands
84
What is hair composed of?
Keratin secreted from hair follicle stem cells
85
What is hair involved in?
Thermoregulation | Protection of the epidermis from UV, abrasions and bites
86
What are the 3 phages of hair formation?
Telogen (rest) Anagen (Growth) Catagen (cessation)
87
What controls growth of hair follicles?
Bone morphometric protein (BMP) - a growth factor
88
What are nails made from?
composed of keratin secreted from the epidermal cells in the root nail
89
Function of nails?
Protect fingertips and toes from damage | Aids in the precision of movement
90
What pathway does BMP control hair growth through?
Winglet pathway (Wnt7b)
91
What does the Wnt7b pathway control?
Release of beta-catenin from the adherence junction and it's ability to go to the nucleus and drive cell cycle activity
92
What happens in Telogen?
Around the base of the hair follicle, there is high concentrations of BMP
93
What happens in telogen-anagen?
decrease levels of BMP Deactivate Wnt7b Activation of beta-catenin increase in size of sebaceous glands
94
What happens in the full anagen process?
Same process Full keratin secretion Growth of hair shaft Decrease BMP
95
What happens in catagen?
Suppression of Wnt signalling Increase BMP Apoptosis

Human Epithelial Biology (6 decks)

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