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Endo > Integument > Flashcards

Integument Flashcards

1
Q

What are the 2 layers of the integument?

A
  • Epidermis

- Dermis

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2
Q

Describe the embryological development of the epidermis

A
  • Is the superficial layer
  • Ectodermal origin
  • Basal ayer of ectodermal cells divide to form periderm
  • Further division of basal cells produces intermediate layers
  • Result is multilayered epidermis
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3
Q

What happens to the epidermis in mid-pregnancy?

A
  • Basal layers give rise to typical layers of stratified squamous epithelium
  • Periderm lost
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4
Q

What are the cells of the epithelium called?

A

Keratinocytes

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5
Q

Describe the embryological development of the dermis

A
  • Deeper
  • Derived from mesoderm
  • Mesenchymal mesodermal cells differentiate to connecive tissue cells (collagen fibres and elastic fibres)
  • Denser deeper into dermis
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6
Q

Describe the hypodermis/subcutis

A
  • Layer of loose connective tissue below dermis
  • Anchors skin to underlying structures
  • Thickness varies between species adn area of body
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7
Q

List some adaptations of the integumen

A
  • Hair
  • Skin glands
  • Footpad
  • Planum nasale
  • Hoof
  • Claw
  • Horn
  • Antler
  • Feather
  • Avian/fish scales
  • Beak
  • Ear
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8
Q

Briefly describe the structure of hair

A
  • Present in mammals
  • Epidermal basal cells proliferate into dermis to form hair bud
  • Aggregation of mesenchymal cells (from dermal papilla) projects into tip of hair bud
  • Epidermal cells grow around papilla forming hair bulb from which hair grows
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9
Q

Briefly describe skin glands

A
  • 2 types
  • Sebaceous and sweat
  • Derive from basal layer of epithelium
  • Presence varies with species and body site
  • some glands may be more specialised
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10
Q

Briefly describe the structure of the planum nasae

A
  • Prominent grooves in thick epidermal layer
  • No hair follicles or glands
  • Makes up black part of nose
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11
Q

Briefly describe the structure of the hoof

A
  • Keratinised epidermis
  • Arranged as wall (unguis) and sole (subunguis)
  • Attached to bone by folded dermis (corium)
  • Epidermis form outer wall of hoof
  • Periople is a rubbery band
  • Lamellae are interdigitations between epidermis and dermis
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12
Q

Describe the formation of the solar horn of the hoof

A
  • More similar to skin
  • Dermal area produces epidermal cells
  • Gradually become more flattened and keratinised
  • Migrate towards outside
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13
Q

Briefly describe claws

A
  • Equivalent to laterally compressed hoof
  • Softer horn on underside of claw
  • Adapted for tearing prey, running etc - very tough and highly keratinised
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14
Q

Briefly describe the structure of horns

A
  • Permanent, grow continuously
  • Heavily keratinised epidermis
  • Dermis (corium) closely applie to bone
  • Hypodermis minimal/absent
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15
Q

Briefly describe the structure of feathers

A
  • Highly specialised epidermal structures

- Core of areolar connective tissue inside feather

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16
Q

Briefly describe the structure of scales and beak

A
  • Overlapping plates of heavily keratinised epidermis

- Beak very compact keratinised epidermis appliec to bone

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17
Q

Briefly describe the structure of fish scales

A
  • Overlapping bondy plates derived from dermis

- Covered with epidermis

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18
Q

List the functions of the integument

A
  • Protection (pathogens, infection, physical damage, allergens)
  • Movement
  • thermoregulation
  • Display, communication
  • Production of glandular secretions
  • Storage (fat, vit D)
  • Sensory
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19
Q

List categories of disease processes that may affect integumentary function

A
  • Wounds
  • Inflammation, hypersensitivities
  • Parasites
  • Microbial infections
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20
Q

Describe armadillo skin

A
  • Demal plates making up armour

- Small overlapping epidermal scales called scutes (composed of bone with a covering of horn)

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21
Q

Describe the features of the skin that act as a protective barrier

A
  • Hair, stratum corneum, sebum, sweat
  • Prevents dessication
  • Chemical barrier (inorganic acids, proteins, fatty acids)
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22
Q

Describe the feature of skin that inhibits infectious agents

A
  • Normal microflora
  • esp coagulase negative Staphylococci, Micrococcus spp, Propionibacterioum acnes and Acinetobacter spp
  • Break down lipids to form antibacterial free fatty acids
  • Hair also has high microbial carriage but is not an active surface
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23
Q

Describe the function of the skin in thermoregulation

A
  • Blood flow
  • Sweat production
  • Hair also forms insulative layer
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24
Q

Describe the function of the skin as a sensory organ

A
  • Sensory nerve endings in dermis and epidermis
  • Sensitive to temp, pressure, vibrations, touch and pain
  • Merkel cells: pressure
  • meissener’s corpuscles: gentle pressure
  • Pacinian corpuscles: deep pressure
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25
Q

Describe the function of the skin as an excretory organ

A

Small amounts of urea, uric acid, ammonia and lactic acid

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26
Q

Describe the function of skin in photoprotection

A
  • Urocanic acid and melanin absorb UVA and UVB
  • Nuclear capping by melanin protects progenitor cells from damage by UVA, prevents development of tumour cells
  • Skin thickness
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27
Q

Describe the function of the skin in immunosurveillance

A
  • Keratinocytes immunologically active (IL-1, thymic stromal lymphopoeitin) , can process antigens and stimulate response
  • Langerhans cells provide immunity and direct inflammation
  • T cells and mast cells in dermis (dermal dendrocytes)
  • Antimicrobial proteins
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28
Q

Name the antimicrobial proteins present in the skin

A
  • Beta-defensin

- Cathelicidins

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29
Q

Describe the role of the skin in blood pressure regulation

A
  • Stores Na+ (via cortisol and mineralocorticoids)

- Regulated by immune system cells and lymph capillaries

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30
Q

Describe the role of the skin in vitamin D production

A
  • Previtamin D3 from 7-dehydrocholesterol then isomerised to vitamin D3
  • Basal and suprabasal layers of skin
  • Transported to liver for further metabolism
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31
Q

Describe the role of the skin in nutrient storage

A
  • Na+
  • Fat, water, vitamins
  • Subcutis particularly
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32
Q

Describe the role of the skin as an absorptive substance

A
  • Especially drugs

- Lipid soluble e.g. steroids

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33
Q

What separates the epidermis and the dermis?

A

Basement membrane

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34
Q

Where are the hairs and glands situated?

A

In the dermis

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35
Q

Where are nerves situated in the skin?

A

Bottom of the subcutical-dermal junction

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36
Q

Where are the blood vessels used for thermoregulation in the skin?

A

Under the epidermis

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37
Q

Where is the melanin layer?

A

On top of the basal membrane

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38
Q

Give the layers of the skin from outside to inside

A
  • Epidermis (5 layers)
  • Free nerve endings
  • Dermis: superficial then deep (glands, hairs)
  • Blood vessels
  • Hypoderma
  • Adipose tissue
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39
Q

Describe the structure of the hypodermis

A
  • Connective tissue of mesenchymal origin
  • Deepest and thickest layer
  • Variably present
  • Projects into dermis to protect hair follicles, sweat glands and vessels
  • Predominant cell is lipocyte
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40
Q

Describe the function of the hypodermis

A
  • Energy reserve
  • Themogenesis and insulation
  • Protective padding and support
  • Maintaining surface contour/shape
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41
Q

Why is the hypodermis more susceptible to disease?

A

Small blood supply and so less lymphocytes

42
Q

Describe the structure of the dermis

A
  • Connective tissue of mesenchymal origin
  • Insoluble fibres
  • Soluble polymers
  • Thickness of dermis determines thickness of skin
  • Divided into deep and superficial dermis
  • Contains epidermal appendages, erector pili muscles, blood and lymph vessels and nerves
43
Q

What are the insoluble fibres of the dermis and what is their function?

A
  • Collagen and elastin

- Gives tensile strength

44
Q

What are the soluble polymers of the dermis?

A
  • Proteoglycans and hyaluronan
  • resist and absorb compressive forces
  • Give spongy structure
45
Q

Describe the structure of the epidermis

A
  • No blood supply
  • 5 layers within epidermis
  • Cornified envelope
  • Melanocytes present
  • Langerhans cells
  • Some nerves in the epidermis at the stratum spinosum layer
  • Thickness varies by location and species
  • Keratinocytes
  • Hemodesmosome between epidermis and dermis
  • Desmosomes between keratinocytes
46
Q

What are the layers within the epidermis?

A
  • Stratum basale
  • Stratum spinosum
  • Stratum granulosum
  • Stratum lucidum
  • Stratum corneum
47
Q

Describe the structure of the melanocytes

A
  • Derived from neural crest
  • Immersed in epidermis
  • Close contact with number of keratinocytes via dendritic processes forming epidermal melanin unit
  • Release melanin as membrane bound structres for transfer of pigment to keratinocytes (melanosome)
  • Long podocytes
48
Q

Describe the function of melanocytes

A
  • Production of melanin pigments
  • Melanosomes needed in ear for hearing
  • Hair pigment production
49
Q

Describe the function of melanin

A
  • Screen solar radiation (protection)

- Free radical scavenger

50
Q

What are the different types of melanin?

A
  • Eumelanin (blace/brown)

- Phaeomelanin (reddish yellow)

51
Q

What is skin colour influenced by?

A
  • Carotenoids
  • Oxyhaemoglobin
  • haemoglobin
  • Melanin
52
Q

What controls skin pigmentation?

A
  • Genetic
  • UV light
  • Horomones
  • Melanocyte stimulating hormone (MSH)
53
Q

What is the function of the Langerhans cells?

A
  • Act as immuno-surveillance units

- Professional APCs

54
Q

Describe the structure of teh Langerhans cells

A
  • Located in the epidermis

- Tennis racket shaped or rod shaped cytoplasmic organelles on EM

55
Q

How do Langerhans cells carry out their function?

A
  • Migrate from epidermis to dermis and regional lymph nodes on activation to stimulate T cell activation
  • Markedly reduced in UV light
56
Q

Describe the nerves that enter the epidermis at the stratum spinosum layer

A
  • Pain sensation

- Non-myelinated

57
Q

Describe the structure of keratinocytes

A
  • Large cells, epithelial origin
  • Complex internal cytoskeleton
  • Mainly keratins, some actin (provide strength)
  • Cytoskeleton attached to tight juctions (cell to cell), desmosomes (cell to cell) and hemidesmosomes (cell to dermal proteins)
58
Q

Describe the differentiation of keratinocytes

A
  • Under influence of [Ca2+]
  • K5 and K14 in basal layers
  • K10 in upper layers
59
Q

Give the function of keratinocytes

A

Produce extracellular lipids (ceramides, cholesterols, fatty acids)

60
Q

Describe hemidesmosomes

A
  • Epidermis to dermis
  • Strong link between keratin intermediate filaments and interstitial collagen in dermis
  • Pin dermis to dermis by long stetches of protein with loops around meshwork of dermis
61
Q

Outline how a disease is related to the complexity of teh hemidesmosome molecules

A

Bullous pemphigoid: antigens 1 and 2, collagen XVII, plectin and collagen VII
- Are the anchoring fibrils

62
Q

Describe the structure of desmosomes

A
  • Anchor keratinocytes to each other

- Linking keratin intermediate filaments and providing intracytoplasmic signalling

63
Q

Outline how the structure of desmosomes fallows congenital and autoimmune diseases

A
  • Large number of proteins

- E.g. cadhedrins, protocadhedrins, desmogleins, desmocollins

64
Q

What are cadhedrins?

A

Calcium dependent adhesion proteins

65
Q

What layers of the epidermis are not usualy present in hair skin?

A

Stratum granulosum, stratum lucidum

66
Q

Describe the structure of the stratum basale

A
  • Single layer of cuboidal cells
  • Proliferative and anchoring
  • Hemidesmmosomes and desmosomes
67
Q

What are the 2 types of cells in the stratum basale?

A
  • Anchoring cells

- Proliferative cells (1/3 producing daughter cells, others padding)

68
Q

Describe the anchoring cells within the stratum basale

A
  • Structural role
  • Attached to dermis by hemidesmosomes
  • Attached keratinocyte to keratinocyte by desmosomes
69
Q

Describe the proliferative cells of the stratum basale

A
  • 1 in 3
  • Mitotically active
  • One cell germinative, other differentiate
  • Influenced by variety of factors e.g. growth factors and hormones, inflammatory mediators (IL-1, IL-6, TGFalpha), drugs and vitamins e.g. vit D, retinoids
70
Q

Describe the stratum spinosum

A
  • 1-20 cells thick
  • Thickest layer
  • Polyhedral cells
  • Prominent desmosomes
  • Upper layer produces involucrin (part of cornified layer)
71
Q

Describe the stratum granulosum

A
  • Variably present in haired skin
  • Flattened cells
  • Shrunken nuclei with intracellular keratohyaline ganules containing profilaggrin and loricrin
  • Various lipids and enzymes secreted extracellularly to form water tight seal of skin
72
Q

Describe the stratum lucidum

A
  • Not present in haired skin
  • Variably present in hairless thickened skin
  • Slightly flattened cells, shrunken nuclei
  • Intracellular keratohyaline
  • Increased intercellular lipids (ceramides, cholesterols, fatty acids)
73
Q

Why does the stratum lucidum stain poorly with H&E?

A

High levels of intercellular lipids (ceramides, cholesterols, fatty acids)

74
Q

Describe the stratum corneum

A
  • Anucleate flattened cells (squames) of variable thickness
  • Plasma membrane replaced by cornified envelope comprising intracellular proteins
  • Cross linked with aid of filaggrin and keratins
  • Envelope is complex set of building blocks slowly replacing basement membrane
  • Hydrophilic bonding of lipids forms organised mortar between squames (lipids from lamellar bodies)
75
Q

What are the proteins comprising the envelope in the stratum corneum?

A
  • Involucrin
  • Loricrin
  • Periplakin
76
Q

How does the concentration of Ca2+ moving up through the dermis?

A

Increases as move higher

77
Q

Describe the innervation of the skin

A
  • Sensory nerves
  • Motor nerves
  • Free nerves enter epidermis
  • End at lever of water barrier - top of stratum spinosum, early granulosum
  • When injured, nerves increase over time
78
Q

Describe the sensory nerves of the skin

A
  • Respond to touch, pressure, temperature, nociception, pruritus
  • Mechanoreceptors
  • free nerve endings
  • Rapid adapting and slow adapting
79
Q

What are the rapid adapting sensory nerves of the skin?

A
  • Meissener’s and Pacinian corpuscles

- Tylotrich hair

80
Q

What are the slow adapting sensory nerves of the skin?

A
  • merkel cells
  • Ruffini corpuscles
  • Sinus hairs
  • Tylotrich pad
81
Q

What are the 3 layers of blood supply in the dermis?

A
  • Deep dermal vascular plexus
  • Mid-dermal vascular plexus
  • Superficial dermal vascular plexus
82
Q

Describe the deep dermal vascular plexus

A
  • Inteface of dermis and subcutis
  • Supply lower hair follicle and epitrichial sweat glands
  • Big vessels
  • Responsible for hair growth
83
Q

Describe the mid-dermal vascular plexus

A
  • Level of sebaceous glands
  • Supply erector pili muscles mid hair follicles and sebaceous glands
  • Smaller
  • Around middle of hair level
  • Is the blood supply in telogen
84
Q

Describe the superficial dermal vascular plexus

A
  • Just below epidermis
  • Capillary loops supply epidermis and upper hair follicles
  • Bypass vessels that avoid taking blood to skin, more control of vasoconstriction and dilation for heat loss
85
Q

What are the different types of secretion mechanism?

A
  • Apocrine
  • Holocrine
  • Merocrine
86
Q

What is apocrine secretion?

A

Apical portions of cells pinched off and lost during secretory process

87
Q

What is holocrine secretion?

A

Involves death of cell, secreteory cell released and as it rbreaks apart, contents of cell become secretory product

88
Q

What is merocrine secretion?

A

Form membrane bound secretory vesicles internal to cell

89
Q

How do the cells of sebaceous glands form?

A
  • Basal layer of germinative cells divide

- Differentiate to form large polygonal cells with abundant vacuolated cytoplasm

90
Q

What type of secretion is used by the sebaceous glands and what is contained in the product?

A
  • Holocrine

- Sebum contains TAGs, other lipids (e.g. linoleic acid), transferring, IgA, IgG

91
Q

What are the functions of sebum?

A
  • Lubricates hair and skin

- Required for normal hair shaft separation

92
Q

How is sebum excreted from the sebaceous glands?

A

Via squamous duct to hair follicle

93
Q

List some specialised sebaceous glands

A
  • Meibomian glands (eyelid, fat, prevent dessication)
  • Circumanal gland (pheromones)
  • Supracaudal gland of dogs and cas (bald patch on tail)
  • Submental glands in cats
  • Preputial glands in horses
  • Infraorbital, inguinal and interdigital glands
94
Q

What are the different types of sweat glands?

A
  • Epitrichial

- Atrichial

95
Q

Describe the epitrichial sweat glands

A
  • Associated with hair follicle
  • Single layer of flattened cuboidal cells
  • Surrounded by myoepithelial cells
  • Holocrine
  • Coild and saccular or tubular
  • Below sebaceous
  • Swet into piliary canal just above sebaceous opening
  • Not innervated
  • Pheromonal and antimicrobial properties
96
Q

Describe the atrichial sweat glands

A
  • Not associated with hair follicles
  • Single layer of flattened cuboidal cells surrounded by myoepithelial cells
  • Merocrine secretions (variants are apocrine)
  • Small tightly coiled glands
  • Restricted to non-haired areas e.g. nose, footpad
  • Nervous control
97
Q

List specialised atrichial glands and give the type of secretion

A
  • Apocrine secretion
  • Mammary glands
  • Interdigital glands of small ruminants
  • External ear canal
  • Nasolacrimal glands
  • Apocrine glands of anal sac
98
Q

How is the watertight seal of the skin formed?

A

Various lipids and enzymes secreted extracellularly from the stratum granulosum

99
Q

What are the growth factors and hormones that influence the proliferative cells of the stratum basale?

A
  • Epidermal growth factor
  • Insulin-like GF
  • Keratinocyte GF
  • Cortisol
  • T4
100
Q

Which species have epidermal rete ridges?

A
  • Pigs
  • Horses at mane and tail base
  • Man

Endo (30 decks)

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