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Histology > Skin and breast > Flashcards

Skin and breast Flashcards

1
Q

functions of the skin

A

protection from damaging agents
thermoregulation
sensation
secretion of protective lipids, milk

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2
Q

what is the breast?

A

highly modified area of skin

specialised sweat glands to produce nutritious secretions under hormonal influences

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3
Q

layers of the skin

A

epidermis, dermis, subcutis

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4
Q

what is the epidermis?

A

surface epithelial layer
contacts external environment
downgrowths produce sweat glands, hair follicles and appendages

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5
Q

what is the dermis?

A

middle supporting layer

contains epidermal appendages, vessels, nerves and nerve endings

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6
Q

what are contents of the dermis contained in?

A

embedded in elastocollagenous stroma produced by fibroblasts

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7
Q

what is the subcutis?

A

deepest layer
varies in size and content
composed mainly of adipose tissue

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8
Q

structure of the epidermis

A

stratified epithelium

closely packed flat plates of protein (keratin)

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9
Q

what is on top of the epidermis?

A

closely packed flat plates of protein - keratin

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10
Q

what do the flat plates of protein on the epidermis form?

A

tough, water-repellant layer - stratum corneum

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11
Q

what is the stratum corneum?

A

tough, water repellant layer formed by the closely packed flat plates of keratin on the epidermis

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12
Q

stratum corneum

A

acellular
composed of intracytoplasmic keratin remnants bound to skin after death of keratinocytes that produced them
each plate conforms to shape of cell before its death

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13
Q

stratum corneum in skin exposed to trauma

A

thick (soles and palms)

usually thin

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14
Q

shape of epidermis layers/cells

A

stratified squamous
most superficial 2-3 living layers approach a squamous configuration
most keratinocytes are polyhedral/cuboidal

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15
Q

what are squames? what do they result from?

A

surface plates of keratin and flat dying keratinocytes preceding them

maturation of other layers of keratinocytes

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16
Q

layers of the epidermis

A

basal layer/stratum basale/germinativum
prickle cell layer/stratum spinosum
granular layer/stratum granulosum
keratin layer/stratum corneum

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17
Q

what is the stratum lucidium?

A

skin of the sole
narrow, pale staining layer of compact keratin between granular and thick keratin layers
no structural/functional significance
may be artefact of staining

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18
Q

what are the functions of the junction between the dermis and the epidermis?

A

tethers 2 layers together

minimises risk of dermoepidermal separation by shearing forces

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19
Q

how is the risk of dermoepidermal separation reduced?

A

tethering fibres connect dermis and epidermis to BM

basal cell membrane of basal cells and BM are convoluted

rete ridges

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20
Q

what are rete ridges?

A

downgrowths of epidermis and dermis

not evident in protected areas
highly developed in stressed areas

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21
Q

layers of the BM at the dermoepidermal junction

A

electron-lucent lamina lucida on the epidermal side

electron-dense lamina densa in middle

ill-defined fibroreticular lamina containing fibronectin on dermal side

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22
Q

how do basal cells connect to the lamina densa?

A

hemidesmosomes - anchoring proteins cross the lamina lucida

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23
Q

connections of the lamina densa

A

fine anchoring fibrils of type VII collagen attach it to collagen fibres in the papillary dermis (type I) and fibrillin microfibrils attach it to elastic fibres

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24
Q

shape/appearance of basal cells

A 
cuboidal/low columnar
round/oval nuclei
prominent nucleoli
cytoplasm rich in ribosomes and mitochondria
tonofilaments
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25
Q

what does the cytoplasm of basal cells contain in pigmented skin?

A

melanin granules and lysosomes

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26
Q

what other cells are found in the basal layer?

A

non-keratinocyte cells
melanocytes
Merkel cells

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27
Q

prickle cells appearance

A

polyhedral, central round nuclei, pinkish cytoplasm
tonofilaments, more numerous towards granular layer/desmosomes

cells of upper layer are flatter

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28
Q

how do prickle cells contact eachother?

A

intercellular bridges

formed from small cytoplasmic projections from cell surface to desmosomes

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29
Q

what are the interstices between prickle cells occupied by?

A

cytoplasmic projections of melanocytes and Langerhans’ cells

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30
Q

what do granular keratinocytes contain?

A

small/oval hematoxyphilic round bodies (keratohyaline granules) composed of proteinaceous material containing sulfur rich amino acids

tonofilaments

small round lamellated keratinosomes/Odland bodies

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31
Q

what do flat granular keratinocytes contain?

A

masses of keratinohyaline material
tightly packed tonofibrils
little cytosol/organelles

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32
Q

formation of keratin

A

death of nucleus and cytoplasm leaves keratohyaline and tonofibrils - combine to form keratin

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33
Q

what do keratinosomes produce?

A

complex hydrophobic glycophospholipid

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34
Q

when is the glycophospholipid released by the keratinosome? what is its function?

A

when superficial granular keratinocytes die

glue, cements flakes of keratin together
makes skin-surface unwettable

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35
Q

what does prolonged exposure to wetness lead to?

A

washes away complex hydrophobic glycophospholipid produced by keratinosomes

keratin absorbs water, swells and softens

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36
Q

turnover

A

faster (25-30 days) in traumatised areas
slower - 40-50 days
shortened in some diseases, e.g. psoriasis

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37
Q

when may turnover be shortened?

A

skin diseases, e.g. psoriasis

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38
Q

where are melanocytes derived from?

A

neuroectoderm

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39
Q

where are melanocytes located?

A

basal layer of keratinocytes

contact BM

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40
Q

appearance of melanocytes

A

pale staining
large ovoid nuclei
cytoplasm w/ processes between keratinocytes

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41
Q

what is in the melanocyte cytoplasm?

A

membrane-bound ovoid granules
premelanosomes and melanosomes
striated electron dense core

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42
Q

melanin function

A

skin colour

minimises tissue damage by UV radiation

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43
Q

melanin production

A

tyrosine is converted into intermediate pigment which polymerises into melanin

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44
Q

melanin reaction

A

binds to protein to form active melanoprotein complex
spherical masses of homogenous electron-dense material
obscures premelanosomes

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45
Q

what happens to melanoprotein complexes?

A

pass along cytoplasmic processes of the melanocyte and are transferred into cytoplasm of basal and prickle cell layer keratinocytes

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46
Q

where is the highest conc. of melanoprotein complexes?

A

cytoplasm of basal cell layer keratinocytes

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47
Q

what are Langerhans’ cells?

A

antigen recognition cells

role in immune system

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48
Q

where are Langerhans’ cells located?

A

all layers of epidermis, easily seen in prickle cell layer

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49
Q

appearance of Langerhans’ cells

A

ovoid, pale staining nucleus

pale staining cytoplasm, processes

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50
Q

what does the cytoplasm of Langerhans’ cells contain?

A

scattered characteristic Birbeck granules

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51
Q

what are Birbeck granules?

A

in Langerhans’ cells
rod-like structures w/ periodic cross-striations
most numerous near Golgi
one end may be distended to form spherical saccule

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52
Q

when are Langerhans’ cells increased in number?

A

chronic inflammatory skin disorders -> increased in number and extent/complexity of dendritic processes

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53
Q

what marker do Langerhans’ cells carry?

A

CD1 marker

clearly visualised by immunoperoxidase techniques

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54
Q

what are Merkel cells?

A

sensory receptors in the epidermis

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55
Q

where are Merkel cells located?

A

basal layer

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56
Q

appearance of Merkel cells in different cells

A

melanocytes by routine light microscopy

rounded membrane-bound cytoplasmic neuroendocrine-type granules - electron microscopy

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57
Q

attachments of Merkel cells

A

synaptic junctions with peripheral nerve endings at base of cell

scanty desmosomal attachments to adjacent keratinocytes

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58
Q

how can Merkel cells appear?

A

scattered solitary cells

aggregated when associated w/ hair disk immediately below BM

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59
Q

what are aggregates of Merkel cells sometimes called?

A

touch receptors

tactile corpuscles

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60
Q

what are the skin appendages?

A

pilosebaceous apparatus
isolated sebaceous glands
eccrine sweat glands and ducts
apocrine sweat glands and ducts

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61
Q

what does the pilosebaceous apparatus produce?

A

hair and sebum

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62
Q

what is sebum?

A

non-wettable secretion that protects the hair and augments the non-wettable characteristics of the keratin

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63
Q

what are the components of the pilosebaceous apparatus?

A

hair follicle
hair shaft
sebaceous glands
erector pili

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64
Q

where is hair derived from?

A

epithelium of the follicle

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65
Q

what is the hair follicle? what is its structure?

A

tubular epithelial structure
opens onto epidermal surface

at lower end, the hair bulb

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66
Q

what does the hair bulb contain?

A

concave lower surface

specialised area of dermis - hair papilla

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67
Q

what is the hair papilla? what is it supplied by?

A

specialised area of dermis in the hair bulb

supplied with myelinated and non-myelinated nerve endings and small blood vessels

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68
Q

what does the hair papilla contain?

A

numerous small, actively proliferating germinative cells

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69
Q

what do the germinative cells within the hair papilla produce?

A

hair shaft and internal root sheath - lie within the external root sheath

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70
Q

what is the appearance of the germinative hair bulb cells?

A

dark basophilic cytoplasm

scattering of melanocytes

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71
Q

layers of the internal root sheath

A

Henle’s layer - single cell layer

thicker layer w/ large eosinophilic trichohyalin granules

cuticle - overlapping keratin plates

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72
Q

how is the hair shaft produced?

A

internal root sheath undergoes keratinisation
extends up from hair bulb to insertion of sebaceous glands
leaves potential space around hair shaft into which sebaceous gland products are secreted

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73
Q

what is the external root sheath?

A

modified epidermis

near opening onto skin surface - basal, prickle cell and granular

below insertion of sebaceous glands - highly modified prickle cells and large pale staining cells rich in glycogen

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74
Q

what is outside the external root sheath?

A

thick BM
strongly eosinophilic
glassy membrane
separates it from the fibrocollagenous follicle sheath

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75
Q

what is the fibrocollagenous sheath?

A

surrounds the entire follicle

encloses the sebaceous glands as a thin layer

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76
Q

what is attached to the fibrocollagenous sheath?

A

arrector pili muscle

at or just below the sebaceous glands

77
Q

action of the arrector pili muscle

A

extends obliquely upward from its attachment below the sebaceous glands to its upper attachment in the papillary dermis

78
Q

what produces the internal root sheath?

A

outer cells of the hair bulb epithelium

79
Q

how do trichohyalin granules stain?

A

red

80
Q

what types of epithelium are there in the hair bulb?

A

premedullary, precortical, precuticular

81
Q

division of hair shaft

A

inner medulla, outer cortex, superficial cuticle

82
Q

what is the medulla?

A

division of hair shaft

inner

83
Q

where is the medulla not present?

A

finer vellus and lanugo hairs

84
Q

what is the medulla composed of?

A

layers of tightly packed polyhedral cells

85
Q

what is the cortex composed of?

A

tightly packed keratin

86
Q

what type of keratin is in the cortex? how is it produced?

A

hard

w/out keratohyaline granules

87
Q

what does the cuticle consist of?

A

single layer of flat keratinous scales

overlap in organised manner

88
Q

what is the erector pili muscle? where does it run? what is its function?

A

narrow band of smooth muscle

originates in fibrocollagenous sheath
runs obliquely upward into upper dermis

contraction - hair follicle and shaft more vertical

89
Q

what do sebaceous glands secrete

A

mixture of lipids called sebum

90
Q

activity of sebaceous glands

A

inactive until puberty

enlarge and become secretory after puberty

91
Q

structure of sebaceous glands

A

lobules of large polyhedral cells w/ lipid droplets and dark central nuclei

single layer of cuboidal/flattened precursor cells between BM of each lobule and central mass of cells

92
Q

how are sebaceous glands connected to the hair follicle

A

short ducts lined by stratified squamous epithelium

all layers in normal epidermis

93
Q

production of sebum

A

holocrine

large-scale death of sebaceous cells -> release of lipid contents into ducts, and space between formed hair shaft and external root sheath

94
Q

where are sebaceous glands abundant?

A

face, scalp, ears, nostrils, vulva, around anus

95
Q

where are sebaceous glands absent?

A

soles and palms

96
Q

where do sebaceous glands no open into hair follicles, but onto the epidermal surface?

A

labia minora

areolar skin around nipple

eyelids

lips and buccal mucosa

97
Q

what are sebaceous glands on the areolar skin called?

A

Montgomery’s tubercles

98
Q

what are sebaceous glands in the eyelids called?

A

Meibomian glands

99
Q

what is sweat? what are its contents?

A

hypotonic watery solution with neutral/slightly acid pH containing various ions, e.g. sodium, potassium, chloride

100
Q

where are eccrine glands numerous?

A

forehead, scalp, axillae, palms and soles

101
Q

how do eccrine glands arise?

A

downgrowths of the epidermis

16th week of intrauterine life

102
Q

where is the secretory gland component of the eccrine gland situated?

A

deep in dermis or upper subcutis near dermosubcutaneous junction

103
Q

how does the secretory gland component of the eccrine gland communicate with the exterior?

A

duct

104
Q

shape of the duct in the eccrine gland

A

proximal to the gland it’s coiled

proceeds in single direction up to dermoepidermal unction

coils in epidermis where it is thick

105
Q

cells of eccrine sweat glands

A

inner layer of secretory cells

outer layer of contractile myoepithelial cells bounded by a distinct, sometimes thick membrane

106
Q

structure of dermal ducts

A

2 layers of dark staining cuboidal cells surrounding distinct lumen

surface of lumen - eosinophilic

107
Q

what is the intraepidermal portion of the eccrine duct?

A

spiral
acrosyringium

lining cells may develop small keratohyaline granules and become keratinised when emerging through granular layer

108
Q

what causes secretion from apocrine glands?

A

external stimuli e.g. fear, sexual excitement

109
Q

how do apocrine glands develop?

A

downgrowths of the epidermis

scanty in humans

small and insignificant in childhood, become more prominent and functionally active after puberty

110
Q

where are apocrine glands concentrated?

A

mainly in perineal region, around anus and genitalia

axillae

modified apocrine glands in eyelids, areola, ear

111
Q

what are Moll’s glands?

A

modified apocrine glands in the eyelids

112
Q

what do apocrine glands in the ear do?

A

in external auditory canal

form ceruminous glands which produce ear wax

113
Q

what are apocrine glands composed of?

A

secretory glandular unit in lower dermis/dermosubcutaneous junction

straight duct which opens into a pilosebaceous unit near surface

114
Q

where are the secretory gland units in the apocrine glands located?

A

dermis/dermosubcutaneous junction

115
Q

where does the straight duct in apocrine glands open into?

A

pilosebaceous unit near surface

above entrance of sebaceous duct

116
Q

what is the secretory unit of an apocrine gland composed of?

A

inner layer of cuboidal epithelial cells and outer layer of discontinuous flat cells

surrounded by BM

large lumen

117
Q

what is the straight duct of the apocrine gland composed of?

A

double layer of cuboidal epithelium

118
Q

what does the dermis contain?

A

epidermal appendages, blood supply, nerve supply, lymphatic drainage

119
Q

what is the dermis?

A

supporting tissue on which the epidermis sits

120
Q

what is the dermis composed of?

A

fibroblasts, fibrocytes and their extracellular products

collagen and elastic fibres

GAG-containing matrix

blood vessels and nerves

small numbers of macrophages, lymphocytes and mast cells

121
Q

what are the zones of the dermis?

A

papillary dermis

reticular dermis

122
Q

what is the structure/contents of the papillary dermis?

A

upper, narrow, close to dermoepidermal junction
pale
contains less collagen and elastin, more matrix
thin collagen and elastin fibres more randomly arranged
many fibres perpendicular to skin surface

small blood vessels, fine nerve twigs and nerve endings

123
Q

what is the structure/content of the reticular dermis

A

bulk of dermis

thick, between papillary dermis and subcutaneous adipose tissue
broad bands of dense collagen w/ intervening long thick fibres of elastin
fibres parallel to sin surface

blood vessels, lymphatics, nerves of skin

124
Q

plexi within the dermis and where they’re located

A

deep vascular plexus - in lower reticular dermis close to its border w/ subcutis

superficial vascular plexus in upper reticular dermis close to junction w/ papillary dermis

125
Q

do blood vessels penetrate into the epidermis?

A

no

126
Q

loops of small vessels from superficial vascular plexus

A

run up into papillary dermis

small capillaries lie close to epidermal BM

127
Q

what vessels does the dermis contain?

A

many arteriovenous anastomotic channels

highly specialised shunts (glomus bodies) found in fingertips

128
Q

what are glomus bodies? where are they found?

A

highly specialised shunts

mainly in fingertips

129
Q

why is blood flow variation within the dermis important?

A

skin’s function as a thermoregulatory organ

130
Q

what are skin appendages supplied by?

A

branches from vessels connecting deep and superficial vascular plexuses

131
Q

what does the nerve supply of the skin consist of? what do they do?

A

rich, non-myelinated supply derived from sympathetic ANS - controls skin appendages and vascular flow

afferent myelinated and non-myelinated system - detects cutaneous sensation

132
Q

what nerve endings detect cutaneous sensation?

A

free nerve endings

Pacinian corpuscules

Meissner’s corpuscules

Merkel cells

133
Q

what are free nerve endings? what do they detect?

A

myelinated/non-myelinated

detect pain, itch, temp

134
Q

what are Pacinian corpuscles? what do they detect? where are they found?

A

encapsulated nerve endings w/ characteristic structure

detect pressure, vibration

deep dermis/subcutaneous fat of palms and soles

135
Q

what are Meissner’s corpuscles? what do they detect? where are they found?

A

structured nerve endings confined to dermal papillae

detect touch

feet and hands

136
Q

what does the subcutaneous tissue contain?

A

adipose tissue

extensions of skin structures - in scalp, lower parts of long hair follicles

some apocrine and eccrine glands

137
Q

what does the adipose tissue in the subcutaneous tissue contain?

A

separated by fibrocollagenous septa

contains main blood vessels and nerves supplying dermis

138
Q

what are the functions of the subcutaneous tissue?

A

heat insulator, food store and shock absorber

139
Q

what does the skin on the back, abdomen, thighs and arms have?

A

thin epidermis producing small amounts of loosely packed keratin

poorly formed rete ridge system

small numbers of hair follicles producing fine hair

variable numbers of eccrine glands

140
Q

what does the skin of the sole have?

A

thick epidermis w/ thick layer of compact keratin

well developed rete ridge system to prevent epidermal separation

no hair follicles

abundant eccrine glands and ducts

141
Q

what does the skin of the scalp have?

A

tightly packed hair follicles w/ associated sebaceous glnads

vertical/oblique

142
Q

what does the skin of the fingertip have?

A

thick epidermis w/ thick compact keratin layer

well developed rete ridge system

Meissner’s corpuscles in dermal papillae

Pacinian corpuscles in dermis and subcutis

specialised arteriovenous shunts (glomus bodies)

eccrine sweat glands and ducts

143
Q

what does the skin of the axilla have?

A

highly active apocrine glands

oblique hair follicles

eccrine glands

thin epidermis

144
Q

how do breasts develop?

A

downgrowths from the epidermis along a line (milk line/streak) which runs obliquely from the axilla towards the groin

145
Q

nipple

A

12-20 nipple duct openings arranged in ring

round, raised area of modified skin with convoluted epidermis with increased melanin pigmentation after first pregnancy

surrounded by areola

146
Q

areola

A

modified skin w/ large sebaceous units forming small nodular elevations

increased melanin pigmentation after pregnancy

147
Q

full development of the female breast

A

puberty - increasing estrogen secretions

breasts increase in bulk - increased adipose tissue

ductular system becomes more complex - branches extend into adipose tissue

148
Q

what is gynecomastia?

A

male breast enlarges at puberty due to an extension of rudimentary duct system and increased periductular fibrous tissue

149
Q

structure of the duct openings on the nipple

A

lined be keratinised stratified squamous epithelium

in inactive breast, they’re normally plugged with keratin

emergence of a single lactiferous duct, lined by 2 layered epithelium (basal layer - myoepithelial)

150
Q

what is the support tissue of the nipple

A

fibroadipose tissue containing longitudinal and circular smooth muscle bundles

151
Q

what is the parenchyma of the breast composed of?

A

12-20 distinct lobes

152
Q

what does the breast lobe consist of?

A

duct system (own separate opening in nipple)

embedded in adipose tissue containing fibrocollagenous septa

153
Q

what are septa in the breast?

A

fibrocollagenous
separate lobes

attached to overlying skin by fibrocollagenous bands (Cooper’s suspensory ligaments)

attached to fascia overlying the pectoralis muscle on deep surface

154
Q

what are mammary ducts composed of?

A

columnar/cuboidal epithelium w/ continuous surface layer of epithelial cells with oval nuclei and outer discontinuous layer of myoepithelial cells with clear cytoplasm

155
Q

how does the branching duct system terminate?

A

ends in a cluster of blind-ending terminal ductules, each cluster and its feeding duct comprising a mammary lobule

156
Q

what is a mammary lobule?

A

cluster of blind-ending terminal ductules

feeding duct

157
Q

what tissue surrounds the terminal ducts and lobules?

A

loose fibrous support tissue - rich in capillaries, has lymphocytes, macrophages, mast cells

tissue surrounded by more dense fibrocollagenous support tissue w/ adipose tissue

158
Q

what happens in the second half of the menstrual cycle?

A

gradually increasing progesterone and estrogen secretion by corpus luteum produced in ovary after ovulation

159
Q

what effect does progesterone have?

A

stimulates proliferation of epithelial cells in terminal ductules

become enlarged, early secretion

160
Q

what changes lead to slight enlargement of the breasts?

A

epithelial cells in terminal ductules become enlarged and show evidence of early secretory activity

fluid and GAGs accumulate in loose intralobular fibrocollagenous stroma

161
Q

what happens if fertilization occurs/doesn’t occur?

A

does occur -> ovarian corpus luteum persists and enlarges, secreting more progesterone and causing proliferation and secretory activity in terminal ductules

doesn’t occur -> progesterone levels fall dramatically, structure and secretion returns to normal

162
Q

breast structure changes early in pregnancy

A

vascularity and melanin pigmentation of nipple and areola increase and mammary lobules enlarge by hyperplastic proliferation fo terminal ductule epithelium

some vacuolation in luminal epithelial cells

second trimester: evidence of luminal cell secretion, copius by third trimester and accumulates within hyperplastic terminal ducts

increase in loose lobular support tissue and inflammatory cells

163
Q

functional maturation of the breast in pregnancy is under the influence of what?

A

pituitary and ovarian hormones - high conc. in pregnancy and breastfeeding

164
Q

where are the steroid hormone receptors in the breast tissue?

A

mammary epithelium, particularly in epithelium of terminal ductules of the lobule

165
Q

what is the outermost layer of the epidermis?

A

stratum corneum

166
Q

which layer of the epidermis contains melanocytes?

A

stratum basale

167
Q

which layer of the epidermis contains visible desmosomes?

A

stratum spinosum

168
Q

in which layer is keratin synthesised in the epidermis?

A

stratum granulosum

169
Q

top-bottom layers of epidermis

A 
stratum corneum
stratum lucidum
stratum granulosum
stratum spinosum
stratum basale
170
Q

what are keratohyaline granules?

A

mature keratinocytes which produce keratin

171
Q

why does the stratum spinosum look prickly?

A

desmosomes

172
Q

what is the epithelia of the skin?

A

stratified squamous keratinised epithelium

173
Q

what is a property of melanocytes?

A

synthesise melanin from tyrosine

174
Q

what do melanocytes synthesise melanin from?

A

tyrosine

175
Q

what do melanocytes protect us from?

A

UV a and b

176
Q

what cells in the body contain melanin?

A

melanocytes, substantia nigra, iris, around brain and in eye, oesophagus, mostly in skin

177
Q

which other cells in the skin contain melanin and where does it come from?

A

keratinocytes

melanocytes share made melanin with keratinocytes

178
Q

are hair follicles vascular?

A

yes

179
Q

how are hair follicles formed?

A

downgrowths of epidermis into dermis

180
Q

how can you tell something is an apocrine sweat gland?

A

columnar epithelium

blebs - how it produces secretions

prominent nuclei/nucleoli

181
Q

where are apocrine sweat glands found?

A

perineueum

armpit

182
Q

where do sebaceous glands discharge?

A

directly onto the skin

183
Q

where are sebaceous glands?

A

around genitals, face, scalp, ears, nostrils, not on palms and soles

184
Q

what do sebaceous glands secrete?

A

whole cells

often fatty secretions

185
Q

what do Pacinian corpuscles detect?

A

pressure

186
Q

what is the structure of a Pacinian corpuscle?

A

central axon w/ Schwann cell around it

187
Q

what is the difference between male and female breast tissue?

A

males only have a ductile system, no lobules

188
Q

why may prepubertal females lactate?

A

benign tumor producing lactin

Histology (10 decks)

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