Endo > Integument > Flashcards

Integument Flashcards

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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
Describe the function of the skin as an excretory organ
Small amounts of urea, uric acid, ammonia and lactic acid
26
Describe the function of skin in photoprotection
- 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
27
Describe the function of the skin in immunosurveillance
- 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
28
Name the antimicrobial proteins present in the skin
- Beta-defensin | - Cathelicidins
29
Describe the role of the skin in blood pressure regulation
- Stores Na+ (via cortisol and mineralocorticoids) | - Regulated by immune system cells and lymph capillaries
30
Describe the role of the skin in vitamin D production
- Previtamin D3 from 7-dehydrocholesterol then isomerised to vitamin D3 - Basal and suprabasal layers of skin - Transported to liver for further metabolism
31
Describe the role of the skin in nutrient storage
- Na+ - Fat, water, vitamins - Subcutis particularly
32
Describe the role of the skin as an absorptive substance
- Especially drugs | - Lipid soluble e.g. steroids
33
What separates the epidermis and the dermis?
Basement membrane
34
Where are the hairs and glands situated?
In the dermis
35
Where are nerves situated in the skin?
Bottom of the subcutical-dermal junction
36
Where are the blood vessels used for thermoregulation in the skin?
Under the epidermis
37
Where is the melanin layer?
On top of the basal membrane
38
Give the layers of the skin from outside to inside
- Epidermis (5 layers) - Free nerve endings - Dermis: superficial then deep (glands, hairs) - Blood vessels - Hypoderma - Adipose tissue
39
Describe the structure of the hypodermis
- 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
40
Describe the function of the hypodermis
- Energy reserve - Themogenesis and insulation - Protective padding and support - Maintaining surface contour/shape
41
Why is the hypodermis more susceptible to disease?
Small blood supply and so less lymphocytes
42
Describe the structure of the dermis
- 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
What are the insoluble fibres of the dermis and what is their function?
- Collagen and elastin | - Gives tensile strength
44
What are the soluble polymers of the dermis?
- Proteoglycans and hyaluronan - resist and absorb compressive forces - Give spongy structure
45
Describe the structure of the epidermis
- 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
What are the layers within the epidermis?
- Stratum basale - Stratum spinosum - Stratum granulosum - Stratum lucidum - Stratum corneum
47
Describe the structure of the melanocytes
- 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
Describe the function of melanocytes
- Production of melanin pigments - Melanosomes needed in ear for hearing - Hair pigment production
49
Describe the function of melanin
- Screen solar radiation (protection) | - Free radical scavenger
50
What are the different types of melanin?
- Eumelanin (blace/brown) | - Phaeomelanin (reddish yellow)
51
What is skin colour influenced by?
- Carotenoids - Oxyhaemoglobin - haemoglobin - Melanin
52
What controls skin pigmentation?
- Genetic - UV light - Horomones - Melanocyte stimulating hormone (MSH)
53
What is the function of the Langerhans cells?
- Act as immuno-surveillance units | - Professional APCs
54
Describe the structure of teh Langerhans cells
- Located in the epidermis | - Tennis racket shaped or rod shaped cytoplasmic organelles on EM
55
How do Langerhans cells carry out their function?
- Migrate from epidermis to dermis and regional lymph nodes on activation to stimulate T cell activation - Markedly reduced in UV light
56
Describe the nerves that enter the epidermis at the stratum spinosum layer
- Pain sensation | - Non-myelinated
57
Describe the structure of keratinocytes
- 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
Describe the differentiation of keratinocytes
- Under influence of [Ca2+] - K5 and K14 in basal layers - K10 in upper layers
59
Give the function of keratinocytes
Produce extracellular lipids (ceramides, cholesterols, fatty acids)
60
Describe hemidesmosomes
- 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
Outline how a disease is related to the complexity of teh hemidesmosome molecules
Bullous pemphigoid: antigens 1 and 2, collagen XVII, plectin and collagen VII - Are the anchoring fibrils
62
Describe the structure of desmosomes
- Anchor keratinocytes to each other | - Linking keratin intermediate filaments and providing intracytoplasmic signalling
63
Outline how the structure of desmosomes fallows congenital and autoimmune diseases
- Large number of proteins | - E.g. cadhedrins, protocadhedrins, desmogleins, desmocollins
64
What are cadhedrins?
Calcium dependent adhesion proteins
65
What layers of the epidermis are not usualy present in hair skin?
Stratum granulosum, stratum lucidum
66
Describe the structure of the stratum basale
- Single layer of cuboidal cells - Proliferative and anchoring - Hemidesmmosomes and desmosomes
67
What are the 2 types of cells in the stratum basale?
- Anchoring cells | - Proliferative cells (1/3 producing daughter cells, others padding)
68
Describe the anchoring cells within the stratum basale
- Structural role - Attached to dermis by hemidesmosomes - Attached keratinocyte to keratinocyte by desmosomes
69
Describe the proliferative cells of the stratum basale
- 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
Describe the stratum spinosum
- 1-20 cells thick - Thickest layer - Polyhedral cells - Prominent desmosomes - Upper layer produces involucrin (part of cornified layer)
71
Describe the stratum granulosum
- 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
Describe the stratum lucidum
- 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
Why does the stratum lucidum stain poorly with H&E?
High levels of intercellular lipids (ceramides, cholesterols, fatty acids)
74
Describe the stratum corneum
- 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
What are the proteins comprising the envelope in the stratum corneum?
- Involucrin - Loricrin - Periplakin
76
How does the concentration of Ca2+ moving up through the dermis?
Increases as move higher
77
Describe the innervation of the skin
- 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
Describe the sensory nerves of the skin
- Respond to touch, pressure, temperature, nociception, pruritus - Mechanoreceptors - free nerve endings - Rapid adapting and slow adapting
79
What are the rapid adapting sensory nerves of the skin?
- Meissener's and Pacinian corpuscles | - Tylotrich hair
80
What are the slow adapting sensory nerves of the skin?
- merkel cells - Ruffini corpuscles - Sinus hairs - Tylotrich pad
81
What are the 3 layers of blood supply in the dermis?
- Deep dermal vascular plexus - Mid-dermal vascular plexus - Superficial dermal vascular plexus
82
Describe the deep dermal vascular plexus
- Inteface of dermis and subcutis - Supply lower hair follicle and epitrichial sweat glands - Big vessels - Responsible for hair growth
83
Describe the mid-dermal vascular plexus
- 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
Describe the superficial dermal vascular plexus
- 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
What are the different types of secretion mechanism?
- Apocrine - Holocrine - Merocrine
86
What is apocrine secretion?
Apical portions of cells pinched off and lost during secretory process
87
What is holocrine secretion?
Involves death of cell, secreteory cell released and as it rbreaks apart, contents of cell become secretory product
88
What is merocrine secretion?
Form membrane bound secretory vesicles internal to cell
89
How do the cells of sebaceous glands form?
- Basal layer of germinative cells divide | - Differentiate to form large polygonal cells with abundant vacuolated cytoplasm
90
What type of secretion is used by the sebaceous glands and what is contained in the product?
- Holocrine | - Sebum contains TAGs, other lipids (e.g. linoleic acid), transferring, IgA, IgG
91
What are the functions of sebum?
- Lubricates hair and skin | - Required for normal hair shaft separation
92
How is sebum excreted from the sebaceous glands?
Via squamous duct to hair follicle
93
List some specialised sebaceous glands
- 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
What are the different types of sweat glands?
- Epitrichial | - Atrichial
95
Describe the epitrichial sweat glands
- 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
Describe the atrichial sweat glands
- 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
List specialised atrichial glands and give the type of secretion
- Apocrine secretion - Mammary glands - Interdigital glands of small ruminants - External ear canal - Nasolacrimal glands - Apocrine glands of anal sac
98
How is the watertight seal of the skin formed?
Various lipids and enzymes secreted extracellularly from the stratum granulosum
99
What are the growth factors and hormones that influence the proliferative cells of the stratum basale?
- Epidermal growth factor - Insulin-like GF - Keratinocyte GF - Cortisol - T4
100
Which species have epidermal rete ridges?
- Pigs - Horses at mane and tail base - Man
Endo
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