Skin and breast Flashcards
1
Q
functions of the skin
A
protection from damaging agents
thermoregulation
sensation
secretion of protective lipids, milk
2
Q
what is the breast?
A
highly modified area of skin
specialised sweat glands to produce nutritious secretions under hormonal influences
3
Q
layers of the skin
A
epidermis, dermis, subcutis
4
Q
what is the epidermis?
A
surface epithelial layer
contacts external environment
downgrowths produce sweat glands, hair follicles and appendages
5
Q
what is the dermis?
A
middle supporting layer
contains epidermal appendages, vessels, nerves and nerve endings
6
Q
what are contents of the dermis contained in?
A
embedded in elastocollagenous stroma produced by fibroblasts
7
Q
what is the subcutis?
A
deepest layer
varies in size and content
composed mainly of adipose tissue
8
Q
structure of the epidermis
A
stratified epithelium
closely packed flat plates of protein (keratin)
9
Q
what is on top of the epidermis?
A
closely packed flat plates of protein - keratin
10
Q
what do the flat plates of protein on the epidermis form?
A
tough, water-repellant layer - stratum corneum
11
Q
what is the stratum corneum?
A
tough, water repellant layer formed by the closely packed flat plates of keratin on the epidermis
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
13
Q
stratum corneum in skin exposed to trauma
A
thick (soles and palms)
usually thin
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
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
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
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
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
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
20
Q
what are rete ridges?
A
downgrowths of epidermis and dermis
not evident in protected areas
highly developed in stressed areas
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
22
Q
how do basal cells connect to the lamina densa?
A
hemidesmosomes - anchoring proteins cross the lamina lucida
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
24
Q
shape/appearance of basal cells
A
cuboidal/low columnar round/oval nuclei prominent nucleoli cytoplasm rich in ribosomes and mitochondria tonofilaments
25
what does the cytoplasm of basal cells contain in pigmented skin?
melanin granules and lysosomes
26
what other cells are found in the basal layer?
non-keratinocyte cells
melanocytes
Merkel cells
27
prickle cells appearance
polyhedral, central round nuclei, pinkish cytoplasm
tonofilaments, more numerous towards granular layer/desmosomes
cells of upper layer are flatter
28
how do prickle cells contact eachother?
intercellular bridges
| formed from small cytoplasmic projections from cell surface to desmosomes
29
what are the interstices between prickle cells occupied by?
cytoplasmic projections of melanocytes and Langerhans' cells
30
what do granular keratinocytes contain?
small/oval hematoxyphilic round bodies (keratohyaline granules) composed of proteinaceous material containing sulfur rich amino acids
tonofilaments
small round lamellated keratinosomes/Odland bodies
31
what do flat granular keratinocytes contain?
masses of keratinohyaline material
tightly packed tonofibrils
little cytosol/organelles
32
formation of keratin
death of nucleus and cytoplasm leaves keratohyaline and tonofibrils - combine to form keratin
33
what do keratinosomes produce?
complex hydrophobic glycophospholipid
34
when is the glycophospholipid released by the keratinosome? what is its function?
when superficial granular keratinocytes die
glue, cements flakes of keratin together
makes skin-surface unwettable
35
what does prolonged exposure to wetness lead to?
washes away complex hydrophobic glycophospholipid produced by keratinosomes
keratin absorbs water, swells and softens
36
turnover
faster (25-30 days) in traumatised areas
slower - 40-50 days
shortened in some diseases, e.g. psoriasis
37
when may turnover be shortened?
skin diseases, e.g. psoriasis
38
where are melanocytes derived from?
neuroectoderm
39
where are melanocytes located?
basal layer of keratinocytes
| contact BM
40
appearance of melanocytes
pale staining
large ovoid nuclei
cytoplasm w/ processes between keratinocytes
41
what is in the melanocyte cytoplasm?
membrane-bound ovoid granules
premelanosomes and melanosomes
striated electron dense core
42
melanin function
skin colour
| minimises tissue damage by UV radiation
43
melanin production
tyrosine is converted into intermediate pigment which polymerises into melanin
44
melanin reaction
binds to protein to form active melanoprotein complex
spherical masses of homogenous electron-dense material
obscures premelanosomes
45
what happens to melanoprotein complexes?
pass along cytoplasmic processes of the melanocyte and are transferred into cytoplasm of basal and prickle cell layer keratinocytes
46
where is the highest conc. of melanoprotein complexes?
cytoplasm of basal cell layer keratinocytes
47
what are Langerhans' cells?
antigen recognition cells
| role in immune system
48
where are Langerhans' cells located?
all layers of epidermis, easily seen in prickle cell layer
49
appearance of Langerhans' cells
ovoid, pale staining nucleus
| pale staining cytoplasm, processes
50
what does the cytoplasm of Langerhans' cells contain?
scattered characteristic Birbeck granules
51
what are Birbeck granules?
in Langerhans' cells
rod-like structures w/ periodic cross-striations
most numerous near Golgi
one end may be distended to form spherical saccule
52
when are Langerhans' cells increased in number?
chronic inflammatory skin disorders -> increased in number and extent/complexity of dendritic processes
53
what marker do Langerhans' cells carry?
CD1 marker
| clearly visualised by immunoperoxidase techniques
54
what are Merkel cells?
sensory receptors in the epidermis
55
where are Merkel cells located?
basal layer
56
appearance of Merkel cells in different cells
melanocytes by routine light microscopy
rounded membrane-bound cytoplasmic neuroendocrine-type granules - electron microscopy
57
attachments of Merkel cells
synaptic junctions with peripheral nerve endings at base of cell
scanty desmosomal attachments to adjacent keratinocytes
58
how can Merkel cells appear?
scattered solitary cells
aggregated when associated w/ hair disk immediately below BM
59
what are aggregates of Merkel cells sometimes called?
touch receptors
tactile corpuscles
60
what are the skin appendages?
pilosebaceous apparatus
isolated sebaceous glands
eccrine sweat glands and ducts
apocrine sweat glands and ducts
61
what does the pilosebaceous apparatus produce?
hair and sebum
62
what is sebum?
non-wettable secretion that protects the hair and augments the non-wettable characteristics of the keratin
63
what are the components of the pilosebaceous apparatus?
hair follicle
hair shaft
sebaceous glands
erector pili
64
where is hair derived from?
epithelium of the follicle
65
what is the hair follicle? what is its structure?
tubular epithelial structure
opens onto epidermal surface
at lower end, the hair bulb
66
what does the hair bulb contain?
concave lower surface
| specialised area of dermis - hair papilla
67
what is the hair papilla? what is it supplied by?
specialised area of dermis in the hair bulb
| supplied with myelinated and non-myelinated nerve endings and small blood vessels
68
what does the hair papilla contain?
numerous small, actively proliferating germinative cells
69
what do the germinative cells within the hair papilla produce?
hair shaft and internal root sheath - lie within the external root sheath
70
what is the appearance of the germinative hair bulb cells?
dark basophilic cytoplasm
| scattering of melanocytes
71
layers of the internal root sheath
Henle's layer - single cell layer
thicker layer w/ large eosinophilic trichohyalin granules
cuticle - overlapping keratin plates
72
how is the hair shaft produced?
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
73
what is the external root sheath?
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
74
what is outside the external root sheath?
thick BM
strongly eosinophilic
glassy membrane
separates it from the fibrocollagenous follicle sheath
75
what is the fibrocollagenous sheath?
surrounds the entire follicle
| encloses the sebaceous glands as a thin layer
76
what is attached to the fibrocollagenous sheath?
arrector pili muscle
| at or just below the sebaceous glands
77
action of the arrector pili muscle
extends obliquely upward from its attachment below the sebaceous glands to its upper attachment in the papillary dermis
78
what produces the internal root sheath?
outer cells of the hair bulb epithelium
79
how do trichohyalin granules stain?
red
80
what types of epithelium are there in the hair bulb?
premedullary, precortical, precuticular
81
division of hair shaft
inner medulla, outer cortex, superficial cuticle
82
what is the medulla?
division of hair shaft
| inner
83
where is the medulla not present?
finer vellus and lanugo hairs
84
what is the medulla composed of?
layers of tightly packed polyhedral cells
85
what is the cortex composed of?
tightly packed keratin
86
what type of keratin is in the cortex? how is it produced?
hard
| w/out keratohyaline granules
87
what does the cuticle consist of?
single layer of flat keratinous scales
| overlap in organised manner
88
what is the erector pili muscle? where does it run? what is its function?
narrow band of smooth muscle
originates in fibrocollagenous sheath
runs obliquely upward into upper dermis
contraction - hair follicle and shaft more vertical
89
what do sebaceous glands secrete
mixture of lipids called sebum
90
activity of sebaceous glands
inactive until puberty
enlarge and become secretory after puberty
91
structure of sebaceous glands
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
how are sebaceous glands connected to the hair follicle
short ducts lined by stratified squamous epithelium
all layers in normal epidermis
93
production of sebum
holocrine
large-scale death of sebaceous cells -> release of lipid contents into ducts, and space between formed hair shaft and external root sheath
94
where are sebaceous glands abundant?
face, scalp, ears, nostrils, vulva, around anus
95
where are sebaceous glands absent?
soles and palms
96
where do sebaceous glands no open into hair follicles, but onto the epidermal surface?
labia minora
areolar skin around nipple
eyelids
lips and buccal mucosa
97
what are sebaceous glands on the areolar skin called?
Montgomery's tubercles
98
what are sebaceous glands in the eyelids called?
Meibomian glands
99
what is sweat? what are its contents?
hypotonic watery solution with neutral/slightly acid pH containing various ions, e.g. sodium, potassium, chloride
100
where are eccrine glands numerous?
forehead, scalp, axillae, palms and soles
101
how do eccrine glands arise?
downgrowths of the epidermis
16th week of intrauterine life
102
where is the secretory gland component of the eccrine gland situated?
deep in dermis or upper subcutis near dermosubcutaneous junction
103
how does the secretory gland component of the eccrine gland communicate with the exterior?
duct
104
shape of the duct in the eccrine gland
proximal to the gland it's coiled
proceeds in single direction up to dermoepidermal unction
coils in epidermis where it is thick
105
cells of eccrine sweat glands
inner layer of secretory cells
outer layer of contractile myoepithelial cells bounded by a distinct, sometimes thick membrane
106
structure of dermal ducts
2 layers of dark staining cuboidal cells surrounding distinct lumen
surface of lumen - eosinophilic
107
what is the intraepidermal portion of the eccrine duct?
spiral
acrosyringium
lining cells may develop small keratohyaline granules and become keratinised when emerging through granular layer
108
what causes secretion from apocrine glands?
external stimuli e.g. fear, sexual excitement
109
how do apocrine glands develop?
downgrowths of the epidermis
scanty in humans
small and insignificant in childhood, become more prominent and functionally active after puberty
110
where are apocrine glands concentrated?
mainly in perineal region, around anus and genitalia
axillae
modified apocrine glands in eyelids, areola, ear
111
what are Moll's glands?
modified apocrine glands in the eyelids
112
what do apocrine glands in the ear do?
in external auditory canal
form ceruminous glands which produce ear wax
113
what are apocrine glands composed of?
secretory glandular unit in lower dermis/dermosubcutaneous junction
straight duct which opens into a pilosebaceous unit near surface
114
where are the secretory gland units in the apocrine glands located?
dermis/dermosubcutaneous junction
115
where does the straight duct in apocrine glands open into?
pilosebaceous unit near surface
above entrance of sebaceous duct
116
what is the secretory unit of an apocrine gland composed of?
inner layer of cuboidal epithelial cells and outer layer of discontinuous flat cells
surrounded by BM
large lumen
117
what is the straight duct of the apocrine gland composed of?
double layer of cuboidal epithelium
118
what does the dermis contain?
epidermal appendages, blood supply, nerve supply, lymphatic drainage
119
what is the dermis?
supporting tissue on which the epidermis sits
120
what is the dermis composed of?
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
what are the zones of the dermis?
papillary dermis
reticular dermis
122
what is the structure/contents of the papillary dermis?
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
what is the structure/content of the reticular dermis
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
plexi within the dermis and where they're located
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
do blood vessels penetrate into the epidermis?
no
126
loops of small vessels from superficial vascular plexus
run up into papillary dermis
small capillaries lie close to epidermal BM
127
what vessels does the dermis contain?
many arteriovenous anastomotic channels
highly specialised shunts (glomus bodies) found in fingertips
128
what are glomus bodies? where are they found?
highly specialised shunts
mainly in fingertips
129
why is blood flow variation within the dermis important?
skin's function as a thermoregulatory organ
130
what are skin appendages supplied by?
branches from vessels connecting deep and superficial vascular plexuses
131
what does the nerve supply of the skin consist of? what do they do?
rich, non-myelinated supply derived from sympathetic ANS - controls skin appendages and vascular flow
afferent myelinated and non-myelinated system - detects cutaneous sensation
132
what nerve endings detect cutaneous sensation?
free nerve endings
Pacinian corpuscules
Meissner's corpuscules
Merkel cells
133
what are free nerve endings? what do they detect?
myelinated/non-myelinated
detect pain, itch, temp
134
what are Pacinian corpuscles? what do they detect? where are they found?
encapsulated nerve endings w/ characteristic structure
detect pressure, vibration
deep dermis/subcutaneous fat of palms and soles
135
what are Meissner's corpuscles? what do they detect? where are they found?
structured nerve endings confined to dermal papillae
detect touch
feet and hands
136
what does the subcutaneous tissue contain?
adipose tissue
extensions of skin structures - in scalp, lower parts of long hair follicles
some apocrine and eccrine glands
137
what does the adipose tissue in the subcutaneous tissue contain?
separated by fibrocollagenous septa
contains main blood vessels and nerves supplying dermis
138
what are the functions of the subcutaneous tissue?
heat insulator, food store and shock absorber
139
what does the skin on the back, abdomen, thighs and arms have?
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
what does the skin of the sole have?
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
what does the skin of the scalp have?
tightly packed hair follicles w/ associated sebaceous glnads
vertical/oblique
142
what does the skin of the fingertip have?
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
what does the skin of the axilla have?
highly active apocrine glands
oblique hair follicles
eccrine glands
thin epidermis
144
how do breasts develop?
downgrowths from the epidermis along a line (milk line/streak) which runs obliquely from the axilla towards the groin
145
nipple
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
areola
modified skin w/ large sebaceous units forming small nodular elevations
increased melanin pigmentation after pregnancy
147
full development of the female breast
puberty - increasing estrogen secretions
breasts increase in bulk - increased adipose tissue
ductular system becomes more complex - branches extend into adipose tissue
148
what is gynecomastia?
male breast enlarges at puberty due to an extension of rudimentary duct system and increased periductular fibrous tissue
149
structure of the duct openings on the nipple
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
what is the support tissue of the nipple
fibroadipose tissue containing longitudinal and circular smooth muscle bundles
151
what is the parenchyma of the breast composed of?
12-20 distinct lobes
152
what does the breast lobe consist of?
duct system (own separate opening in nipple)
embedded in adipose tissue containing fibrocollagenous septa
153
what are septa in the breast?
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
what are mammary ducts composed of?
columnar/cuboidal epithelium w/ continuous surface layer of epithelial cells with oval nuclei and outer discontinuous layer of myoepithelial cells with clear cytoplasm
155
how does the branching duct system terminate?
ends in a cluster of blind-ending terminal ductules, each cluster and its feeding duct comprising a mammary lobule
156
what is a mammary lobule?
cluster of blind-ending terminal ductules
feeding duct
157
what tissue surrounds the terminal ducts and lobules?
loose fibrous support tissue - rich in capillaries, has lymphocytes, macrophages, mast cells
tissue surrounded by more dense fibrocollagenous support tissue w/ adipose tissue
158
what happens in the second half of the menstrual cycle?
gradually increasing progesterone and estrogen secretion by corpus luteum produced in ovary after ovulation
159
what effect does progesterone have?
stimulates proliferation of epithelial cells in terminal ductules
become enlarged, early secretion
160
what changes lead to slight enlargement of the breasts?
epithelial cells in terminal ductules become enlarged and show evidence of early secretory activity
fluid and GAGs accumulate in loose intralobular fibrocollagenous stroma
161
what happens if fertilization occurs/doesn't occur?
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
breast structure changes early in pregnancy
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
functional maturation of the breast in pregnancy is under the influence of what?
pituitary and ovarian hormones - high conc. in pregnancy and breastfeeding
164
where are the steroid hormone receptors in the breast tissue?
mammary epithelium, particularly in epithelium of terminal ductules of the lobule
165
what is the outermost layer of the epidermis?
stratum corneum
166
which layer of the epidermis contains melanocytes?
stratum basale
167
which layer of the epidermis contains visible desmosomes?
stratum spinosum
168
in which layer is keratin synthesised in the epidermis?
stratum granulosum
169
top-bottom layers of epidermis
```
stratum corneum
stratum lucidum
stratum granulosum
stratum spinosum
stratum basale
```
170
what are keratohyaline granules?
mature keratinocytes which produce keratin
171
why does the stratum spinosum look prickly?
desmosomes
172
what is the epithelia of the skin?
stratified squamous keratinised epithelium
173
what is a property of melanocytes?
synthesise melanin from tyrosine
174
what do melanocytes synthesise melanin from?
tyrosine
175
what do melanocytes protect us from?
UV a and b
176
what cells in the body contain melanin?
melanocytes, substantia nigra, iris, around brain and in eye, oesophagus, mostly in skin
177
which other cells in the skin contain melanin and where does it come from?
keratinocytes
melanocytes share made melanin with keratinocytes
178
are hair follicles vascular?
yes
179
how are hair follicles formed?
downgrowths of epidermis into dermis
180
how can you tell something is an apocrine sweat gland?
columnar epithelium
blebs - how it produces secretions
prominent nuclei/nucleoli
181
where are apocrine sweat glands found?
perineueum
armpit
182
where do sebaceous glands discharge?
directly onto the skin
183
where are sebaceous glands?
around genitals, face, scalp, ears, nostrils, not on palms and soles
184
what do sebaceous glands secrete?
whole cells
often fatty secretions
185
what do Pacinian corpuscles detect?
pressure
186
what is the structure of a Pacinian corpuscle?
central axon w/ Schwann cell around it
187
what is the difference between male and female breast tissue?
males only have a ductile system, no lobules
188
why may prepubertal females lactate?
benign tumor producing lactin
