Histo - Integumentary System Flashcards
What are the components of integumentary system?
Skin and epidermal derivatives
What are epidermal derivatives?
Hair follicles, hair, sweat glands, oil glands, nails
What are the 6 major functions of the integumentary system?
- Protective
- Immunologic
- Homeostasis
- Sensory
- Endocrine
- Exocrine
What are the 2 layers of the skin?
Epidermis and dermis
Which is superficial/deep: epidermis vs dermis?
epidermis = superficial dermis = deep
What is the epidermis made up of? What is the dermis made up of?
EPDIERMIS =
keratinized stratified squamous epithelium,
DERMIS =
connective tissue
What are the epidermis/dermis derivatives of?
Epidermis - ectoderm derivative
Dermis - mesoderm derivative
Which is avascular/vascular: epidermis vs dermis?
epidermis - avascular, receives nourishment from dermis
dermis - highly vascularized
What is the layer deep to the skin? All names for it.
Hypodermis
aka subcutaneous layer aka subcutaneous fascia
What is the hypodermis composed of? Is it vascularized? How thick is it?
adipose tissue
vascularized
thickness varies from person to person
Where is this found: thick skin vs thin skin
thick skin = palms of hands / feet
- hairless skin, areas subject to most abrasion
thin skin = everywhere else
- hair follicles are present in most locations
Which layer being thick qualifies an area of skin as being “thick skin”?
How many layers = thick skin?
Epidermis.
Must be 5 layers to be thick skin.
Why is upper portion of back not “thick skin”?
because the DERMIS is thick. But the epidermis is comparable to other portions of the body, and the epidermis qualifies skin as “thick skin”
What is a strata?
a layer
What are the layers of thick skin from deep to superficial?
- Stratum basale
- Stratum spinosum
- Stratum granulosum
- Stratum Lucidum
- Stratum Corneum
What are 4 cells present in epidermis?
- Keratinocytes
- Melanocytes
- Langerhan’s cells
- Merkel’s cells
What are melanocytes?
cells present in epidermis
pigment producing cells
What are langerhan’s cells?
cells present in epidermis
antigen-presenting cells of immune system
What are merke’s cells?
cells present in epidermis
mechanoreceptor cells associated with sensory nerve endings
What is the principle cell type in epidermis?
keratinocytesw
What do keratinocytes produce?
keratin (major structural protein of epidermis)
What does keratin form?
keratin filaments (type of intermediate filaments aka tonofilaments)
Which cell type produces the water-barrier?
Why is this necessary?
keratinocytes
essential for establishing dry epithelial characteristics in mammals
What are lamellar bodies? What produces them? Where?
Produced by keratinocytes
In the stratum spinosum
They are tubular/ovoid shaped membrane-bound organelles
lipid-containing structures
Describe the cells in the stratum basale layer
single layer of basophilic cells
small, cuboidal/low columnar
Production of ____ begins in the stratum basale layer
intermediate (keratin_ filaments begin here and differentiate as they move upwards
Which epidermis layer is mitotically active?
Stratum basale
What does it mean to say that the stratum basale layer is mitotically active?
that the stratum basale contains stem cells that give rise to keratinocytes
Describe the cell type in stratum spinosum
Keratinocytes exhibit numerous cytoplasmic processes (“spines”)
these processes attached to adjacent cells via DESMOSOMES
What happens during histological preparation of stratum spinosum?
Cells shrink, leaves expanded intercellular space between spines
this contributes to spiny / prickly appearance - aka stratum SPINosum
Why is the stratum spinosum named that?
because histo processing leaves expanded intercellular space between cytoplasmic processes “spines”
which leads to a spiny/prickly appearance
How are adjacent cytoplasmic processes of keratinocytes attached to one another in stratum spinosum layer?
desmosomes
Tonofibrils are formed where?
What are they?
Stratum spinosum.
Intermediate filaments (tonofilaments) are bundled together and grouped into tonofibrils
Intermediate filaments are bundled together to form ____ in the ___ layer.
tonofibrils
stratum spinosum
What initiates the intermediate filament bundling in the stratum spinosum?
keratohyalin granules
contain proteins that promote aggregation
Where does synthesis of keratohyalin granules and lemallar bodies begin?
upper portion of stratum spinosum
What 3 things are produced in stratum spinosum?
- tonofibrils
- keratohyalin granules
- lamellar bodies
What are the distinguishing features of stratum granulosum?
intensely basophilic keratinocytes containing keratinohyalin granules
and bundled tonofilaments into tonofibrils (because these are present everywhere in this layer)
Conversion of granular cells into ___ takes place in which layer?
granular cells into cornified cells
takes place in stratum granulosum
Keratinization converts ___ into ___ in which layer?
conversion of granular cells into cornified cells in the stratum granulosum
What are cornified cells?
dead, a-nucleus cells filled with keratin filaments
produced via keratinization in the stratum granulosum
What happens to the lamellar bodies in the stratum granulosum?
lamellar bodies contents are released in the intercellular space between the stratum granulosum and stratum corneum
Where is the stratum lucidum found?
thick skin
Which extra layer is found in thick skin?
stratum lucidum
Describe the histology of stratum lucidum
thin, translucent, eosinophilic cells
nucleus and cytoplasmic organelles are disrupted and disappear because they are mostly keratinized
(because the cells are filling up with keratin)
Describe the cells of the stratum corneum
Cells have lost their nuclei and cytoplasmic organelles (consists of flattened, dessicated, a-nucleus cells)
What happens to most superficial cells in the stratum corneum?
sloughed off
Which layer of epidermis is the “mitotically active” layer?
stratum basale
Which layer of epidermis is the “packaging and releasing” layer?
stratum spinosum and stratum granulosum
Which layer of epidermis is the “dead packaged cells” layer?
stratum corneum
Describe the layers involved in the synthesis and bundling of tonofilaments
Synthesis begins in stratum basale
Synthesis continues in the stratum spinosum
Bundling into tonofibrils via keratoyhyalin granules takes place in stratum spinosum
Which layer is characterized by intensely basophilic keratohyalin granules and releases lamellar bodies?
Stratum granulosum
Which layer has cornified cells in it?
stratum corneum
What is the primary function of melanocytes?
produce and secrete pigments
Where is melanin synthesized and stored?
melanosmes
Where are melanocytes located?
Rounded cell bodies in stratum basale
long processes (dendritic ends) extend upward between keratinocytes in stratum psinosum
How are melanosomes transferred?
melanosomes (containing melanin) transfered from cell bodies of melanocytes to the dendritic ends of melanocytes.
Once in stratum spinosum, they are transferred to the adjacent keratinocytes
Why are melanosomes transferred from melanocytes to keratinocytes?
so that the melanin can accumulate over keratinocytes nuclei to protect DNA from UV radiation
Describe melanocytes on a histology slide
elongated nuclei surrounded by clear cytoplasm
Langerhan cells are ____-presenting cells typically found in the ____.
antigen-presenting cells
found in stratum spinosum
How do langerhan cells interact with antigens?
encounter and process antigens at the skin and bring them to T-lymphocytes within the nearby lymph nodes
What are langerhan cells derived from?
common lymphoid progenetor cells within bone marrow
“bone marrow derived” cells
Which cells are “bone marrow derived” cells? What does this mean?
langerhan cells
they are derived from lymphoid progenitor cells within bone marrow
Where are merkel cells located?
stratum basale
Which cell type contains neurosecretory granules?
merkel’s cells
Which cell type is a mechanoreceptor associated with sensory nerve endings?
Merkel’s cells
What is special about the base of merkel’s cells?
base of merkel’s cells are associated with expanded, plate-like terminal of AFFERENT nerve fibers called MERKEL’S CORUSCLE
What is merkel’s corpuscle?
Base of merkel’s cells are associated with expanded, plate like terminals of afferent nerve fibers called merkel’s corpuscle
Where are merkel cells most abundant?
In areas of acute sensory perception
What are the three types of cancer’s with epidermal origin?
- Basal Cell Carcinoma
- Squamous Cell Carcinoma
- Malignant Melanoma
Describe basal cell carcinoma and treatment
most common type of epidermal cancer
resembles cells of stratum basale
slow growing tumor, least aggressive, least likely to metastisize
treatment = surgical removal of lesion
Describe squamous cell carcinoma and treatment
second most common type of epidermal cancer
characterized by highly atypical cells at all levels of epidermis (yields variable differentiation patterns)
more aggressive than basal cell carcinoma therefore more likely to metasticize
treatment = varies depending on histo type, size, location
Describe malignant melanoma and treatment
Most serious form of epidermal cancer
originates from melanocytes
presents as irregularly pigmented, multi-color lesion
localized treatment = surgical removal
advanced treatment = chemotherapy, immunotherapy and surgery
What are the 2 layers of the dermis?
1 papillary layer
2 reticular layer
Describe the type of connective tissue found in the 2 layers of the dermis
1 pappillary layer (loose areolar ct)
2 reticular layer (dense irregular ct)
describe dermal papillae.
where are they found?
finger-like connective tissue protrusions that project upward into epidermis at the epidermal-dermal junction
have sensory nerve endings and blood vessels
Which layer of the dermis is thickest?
reticular layer is considerably thicker than papillary layer
Which layer of the dermis has fewer cells?
reticular layer has fewer cells than the papillary layer
Where are pacinian corpuscles found?
dermis and hypodermis
Describe pacinian corpuscles
large ovoid structures
myelinated nerve endings surrounded by capsule consisting of concentric lamellae
What is the inner core of pacinian corpuscles?
inner core of pacinian corpuscles =
series of tightly packed, flattened schwann cell lamellae surrounding unmyelinated axons
What do pacinian corpuscles detect?
pressure and vibrations
Describe meissner’s corpucsles
tapered, cylindrical structures
flattened schwann cell forms lamellae
unmyelinated nerve endings follow spiral paths in corpuscle
Where are meissner’s corpuscles located?
dermal papillae of hairless skin
What do meissner’s corpuscles detect?
light touch
What are epidermal skin appendages derived from?
epidermal epithelium during development
What are 4 examples of epidermal skin appendages?
hair/hair follicles
eccrine sweat (sudoriferous) glands
apocrine sweat (sudoriferous) glands
sebacious (oil) glands
Define hair and hair follicles
hair = elongated filamentous, keratinized structures that project through hair follicles
hair follicles = responsible for production/growth of hair
Where are hair/hair follicles found?
along surface of most of skin but NOT on thick skin (also not on urogenital orifices/lips)
What type of muscle is the arrector pili muscle?
smooth muscle
Where does the arrector pili muscle extend to/from?
extends from connective tissue sheath surrounding hair follicle to papillary layer of dermis
What happens with contraction of arrector pili muscle?
hair “stands up” resulting in “goosebumps”
Arrector pili muscle plays a role in ___ .
Controlled by what?
has a role in insulation
controlled by sympathetic innervation
Describe where it is found: eccrine gland vs apocrine gland
eccrine gland = widely distributed on most parts of skin (mostly on thick skin)
apocrine gland = axillary and perineal regions of skin
Describe the tubular gland: eccrine gland vs apocrine gland
eccrine - simple coiled tubular gland
apocrine - coiled tubular with wide lumen
Describe mode of secretion: eccrine gland vs apocrine gland
both are merocrine secretion
apocrine secretion through hair follicle canal
Describe secretion: eccrine gland vs apocrine gland
eccrine gland - excretes wastes/excess salts
apocrine gland - viscous, protein rich sweat
Why does apocrine gland cause body odor?
because of bacterial breakdown of sweat.
without bacterial breakdown of sweat = apocrine gland secretion is odorless
Eccrine sweat gland: describe secretory portion
double layer epithelial cells
layer/lighter staining than cells in duct
located in deep dermis (mostly) but also in upper hypodermis
Eccrine sweat glands: describe duct portion
narrower outside diameter and lumen than secretory portion
double layer of small cuboidal cells
ducts smaller/darker than secretory cells
Apocrine sweat glands: describe secretory portion
wide lumen (wider than eccrine glands)
simple cuboidal epithelium
eosinophilic cytoplasm
upper part of hypodermis (mostly) but also deep in dermis
Apocrine sweat glands: describe duct portion
stratified cuboidal epithelium (2-3 layers)
narrower lumen, similar to eccrine glands
where do the duct portions of eccrine and apocrine secrete?
eccrine - secretes onto epoidermal surface
apocrine - secretes into follicle canal of hair follicle
When is the onset of function? eccrine vs apocrine glands
eccrine - soon after birth
apocrine - puberty
Where are sebacious (oil) glands found?
found everywhere except thick skin
Why are sebacious (oil) glands not found in thick skin?
because sebacious (oil) glands are associated with hair follicles
and hair follicles are not found on thick skin
What is sebum?
lipid-containing substance that is produced/secreted by sebacious oil galnds
Sebacious (oil) glands produce and secrete ____
Sebum
What mode of secretion do sebacious glands use?
Holocrine (apoptosis type)
Sebacious glands are involved in ___ development. Therefore there is an increase activity during ___
acne
puberty
Nails are what type of epithelium?
keratinized
Epithelium of nails is continuous with ________
stratum basale and stratum spinosum of epidermis
Are nails easy to stain histologically?
no. difficult to distinguish between other structures.
