New Deck Flashcards
epidermis: what kind of cells? what important molecule is produced?
stratified squamous that produces keratin.
desrcibe the dermis
fibrous connective tissue containing blood vessels, nerves and sensory receptors
hypodermis or subcutis: what kind of tissue is found here?
mainly adipose tissue, blood vessels and nerves.
often referred as the superficial fascia
what is desquamation?
friction and exposure to the environment that results in the sloughing off of the cells
what is keratinization?
keratinocytes in the basal layer are pushed up, and they mature as they go upwards.
keratinocyte die as they reach the surface; all that remains in the skin surface keratin
what is a keratinocyte?
keratinocyte is a generic name for the epithelial cells of the epidermis- but they look different depending on the layer that they are in.
stem cells in the basal layer undergo what kind of division?
asymmetric division- one a stem cell and other a keratinocyte that will begin maturation.
squamous or spinous layer- what kind of cells are in this layer? what are the characteristics of the cells in this layer?
formed by polyhedral keratinocytes.
they have pale nucleus, and very visible nucleolus- an indication that it is actively producing cytokeratin.
cytokeratin goes on to form bundles of tonofibrils in the cytoplasm, which are important for desmosome integrity
cytokeratin forms what?
tonofibrils in the cytoplasm, which are important for desmosome integrity
granular layer- what do keratinocytes in this layer produce? how ar ethe keratinocytes in this layer characterized?
keratinocytes in this layer produce keratohyaline granules, which attach to tonofibrils.
**keratin = ** tonofibrils + keratohyaline granules
keratinocytes in this layer are characterized by the presence of lamellar granules in their cytoplasm. these granules contain lipids that are exocytosed from cells to form a barrier to protect against water loss through skin.
at this layer, keratinocytes lose their nucleus and cytoplasm is packed with keratin.
psoriasis
increased number of proliferating stem cells in the basal and spinous layers of the epidermis. as a result, cells in the epidermis are replaced more quickly
leads to improper formation of tonofibrils and keratohyaline granules => defective keratinization
stratum corneum: what kind of cells are here?
non-nucleated keratinocytes called squames
melanocytes: where are they?
are they attached to other cells via desmosomes?
what are their specialized lysosomes called?
melanocytes have cell processes that extend into the squamous layer.
they are not attached to other cells
melanosomes : tyrosine is converted to DOPA then melanin
how does skin get its color?
when keratinocytes in the basal layer and lower squamous layer phagocytize the tips of the melanocyte processes which contain melanosomes (which contain melanin)
how do differences in skin pigmentation arise in different races?
number and size of melanosomes within each melanocyte.
melanocytes have pale staining cytoplasm
what are Langherhan’s cells (or dendritic cells)?
where are they generated?
where are they found?
are they anchored to adjacent cells by desmosomes?
what are their functions?
intra-edpidermal antigen recognition cells
generated in the bone marrow then they travel through the blood to reach the skin. they are part of the immune system
they are found in the squamous layer
they are not bound to adjacent cells.
they phagocytose foreign antigens, and travels through the lymphatic system to a lymph node to intiate a response there.
important in the rejection of skin allografts
protect the skin from tumor formation
what kind of cells are these:
Langerhan’s cells
what are Merkel cells?
what layer are they found in?
they are mechanoreceptors that are sensitive to light touch
they are found in the basal layer
what is the papillary layer?
thin, loose connective tissue layer
fibroblasts, mast cells, macrophages and extravasated leukocytes
what is the reticular layer?
thick dense connective tissue rich in collagen
(mainly type I), elastic fibers
less cells than papillary layer.
Paccinian corpuscles
sense deep pressure and vibration in the palms of the hand and soles of the feet.
cutaneous plexus
blood vessels, junction of hypodermis and dermis
papillary plexus
located at junction of papillary layer of the dermis and the epidermis.
hypodermis: what kind of cells are found here?
layer formed by collagenous fibrous septa filled with adipose tissue
Paccinian corpuscles
blood circulation to the skin orginates from which layer of the skin?
hypodermis
collagen type VII
found anchoring the **dermoepidermal basement membrane ** to the underlying dermis (which contains collagen type III and type I).
basal cells are connected to the dermoepidermal basement membrane by
hemidesmosomes
eccrine sweat glands
secrete sweat
apocrine glands
axilla and groin areas and secrete sweat
which muscle pulls the hair erect
arrector pilli muscle
what are the three layers of the hair follicle
medulla (innermost)
cortex
cuticle (outermost)
what is an acinus?
group of cells arranged in a cluster that produce sebum
has its own duct or conducting portion
histologically, a sweat gland contains
1) a secretory unit in the upper hypodermis or lower dermis
2) a duct that projects vertically towards the surface of the skin
B- sagittal section of eccrine sweat gland
S- secretory acini
D duct sectins
My myoepithelial cells
