lesson 9 gritti Flashcards
epidermis-embrio origin
epithelium derived from ectoderm. it the most outer part and is not vascularized
dermis-embrio origin
connective tissue derived from mesoderm. contains skin derivatives, sensory receptors, blood vessels and innervation
hypodermis
loose connective tissue. contains blood vessels, adipose tissue and innervation. it provides loose attachment to the underlying tissues
papillae
upward invaginations of the dermis into the epidermis
number of layers in the epidermis of thick skin
and thick skin main peculiarities
stratum corneum
stratum lucidum
stratum granulosum
stratum spinosum
stratum basale
5 layers of epidermis
bigger epidermis than dermis
bigger stratum corneum
no hair follicles
present in areas such as the sole of the feet or the palm of the hands where mechanical strength is needed
numb of layers of epidermis in thin skin and thin skin main peculiarities
stratum corneum
stratum granulosum
stratum spinosum
stratum basale
no stratum lucidum, 4 layers in total.
think skin has a bigger dermis (with hair follicles, glands, innervation and blood vessels) within respect to the epidermis
name of the typical cells of the skin
keratinocytes
what connects the keratinocytes to the basal lamina of the basement membrane at the epidermis-dermis junction?
hemidesmosomes connect the basal part of keratinocytes with the collagen type 4 fibers of the basal lamina
what connects laterally the cells of the stratum basale?
desmosomes
what’s the type of epithelium that constitute the epidermis?
stratified squamous keratinized epithelium
direction of the differentiation process
from the stratum basale-upwards
Cytokeratins
-core structural components of the intermediate filaments of keratinocytes (cytokeratinocytes).
-the type of cytokeratins expressed in keratinocytes vary depending on the layer of the epidermis and the differentiation stage of the cells.
-can be consider as a marker of the layer as they have different molecular weights and diff. isoelectric properties (at least 25 diff types)
melanocytes and merker cells (tactile cells), primarily where?
in the stratum basale
layers of keratinocytes in the stratum spinosum
8-10 layers
langherans cells primarily where?
primarily in the stratum spinosum but present in every layer
antigen presenting cells
what is the cytokeratin typical of the stratum basale?
K5 and K14
what is the cytokeratin typical of the stratum spinosum?
K1 and K10
tonofibrils
-primarly found in the stratum spinosum of the epidermis
-bundles of intermediate filaments (keratin filaments made of cytokeratins) that terminate at each desmosome
-the cells extend at both sides of each desmosome creating sort of spines
-the thick skin has a bigger stratum spinosum
keratohyaline granules
granules present in the stratum granulosum that contain filaggrin and other proteins that help the formation of the outermost keratinized layer
lamellar granules
granules present in the stratum granulosum that contain keratin, keratohyalin, lipids and other enzymes.
they are released by exocytosis and contribute to the formation of the impermeable skin layer
–>this layer has the role to prevent water to exit the skin
the stratum granulosum as a transitional layer
it it a transitional layer between the metabolically active stratum spinosum and the dead cells of the stratum corneum.
The cells in the stratum granulosum start to lose their nuclei and are filled up by keratin
layers of cells in the stratum granulosum
3-5 layers
stratum lucidum
specify layer/s
present only in the thick skin. one single layer of keratinocytes that have lost their nuclei and their organelles. their cytoplasms is only composed of packed keratin
stratum corneum layers of keratinocytes
15-20 layers of keratinocytes only filled up with keratin of different types
name of keratinocytes in the stratum corneum
squames and are continuously shed periodically (every 2 weeks)
junctions are mostly absent in which layers of the epidermis?
stratum lucidum and stratum corneum
which is the cytokeratin typical of the stratum granulosum?
cytokeratin 2 and 9
how are Merkel cells connected to the sorrounding keratinocytes in the stratum basale?
through desmosomes
are melanocytes connected through desmosomes to the surrounding keratinocytes
no
how are melanocytes and merkel cells attached to the stratum basale?
through hemidesmosomes
embryological origin of melanocytes and merkel cells
derive from the neural crest
melanocytes metabolic function
they produce melanin so they are metabolically very active. they have short cisternae of RER, multiple mitochondria and a well developed Golgi to undergo this function.
they look pale in histo samples.
what is the brown that we see in the stratum basale of histo samples?
melanin granules that are internalized by the keratinocytes that surround the melanocytes
melanosomes
Melanosomes are specialized vesicles or organelles in melanocytes (the pigment-producing cells in the skin).
how are the melanosomes transported to the tip of the cytoplasmic extensions of melanocytes?
by kinesin
how are melanosomes transported close to the keratinocytes nuclei to create the supranuclear caps?
by dynein
what’s the intermediate filament that melanocytes
contain?
vimentin
what do we mean by saying epidermal melanin unit
one melanocyte plus one keratinocyte
what do langherans cells do for adaptive immunity?
they are dendritic cells of the epidermis
they are antigen-presenting cells
they take the antigen in the skin, they bring it to T lymphocytes in lymphonodes and start an adaptive immune response.
langherans cells communicate with keratinocytes by the expression of?
E cadherins on their surface
langheran cells and surrounding keratinocytes, are they attached or separated?
separated by small clefts
merkel disc
merkel cell + nerve terminal associated
nutrients for keratinocytes arrive from?
the dermis
2 layers of the dermis
papillary dermis and reticular dermis
indistinct boundaries
in the papillary dermis, more cells or more fibers?
more cells
collagen present in the papillary dermis
type I, II and VII
thinner collagen fibers
in the reticular dermis, more cells or fibers?
more fibers
where do we have large vessels and where do we have small vessels in the dermis
small vessels->papillary
large vessels–>reticular
Both dermal regions contain:
-blood and lymphatic vessels
-sensory afferent nerve fibers
2 networks of vessels in the dermis
subpapillary plexus: small capillaries that extend inside the papillae
deep cutaneous plexus: larger vessels in the reticular dermis
between them we can spot anastomosis (glomus body) with thermoregulation function
where is the fat deposited?
in the hypodermis
in which part of the hypodermis depends on hormones and genetic factors
white adipose tissue
consists of cells containing one big white-yellow lipid droplet each
these cells are specialized for fat storage
brown adipose tissue
consist of cells containing multiple lipid droplets surrounded by mitochondria that give them the darker appearance
they release heat
which collagen is present in the lamina surrounding adipocytes?
type IV collagen
Meissner corpuscles
-in the papillary dermis
-initiate impulses when light stimuli deform their shape
-formed by an unmyelinated nerve fiber and flattened Schwann cells perpendicular to the epidermis
-numerous in finger tips, palms, soles
-connective capsule enwrapping the structure
pacinian corpuscle
-in the reticular dermis and hypodermis
-unmyelinated nerve fiber with Schwann cells that form concentric lamellae around
-sorrounded by a connective capsule
-detect pressure and high frequency vibration
Ruffini corpuscles
stimulated when stretching or twisting the skin
3 layers of the hair
central medulla
keratinized cortex
cuticle
from in to out
hair matrix
formed by keratinocytes around a dermal papilla.
they move up become keratinized and form the hair
where are the 2 regions in the hair follicles where stem cells reside in the adult life?
in the bulge and in the papilla
name of the typical granules of Langherans cells
Birbeck granules
huxley’s layer in hair follicle
part of internal root sheet
one or two layer of flatten cells
henle’s layer in hair follicle
part of internal root sheet
one layer of cuboidal cells
