Panopto 27: integument Flashcards
what do melanocytes make?
melanin
How numerous are melanocytes in the epidermis?
they are the third most numerous and make up 5% of the total cells
what are melanocytes similar to
dendrites
where do melanocytes come from?
the ectoderm-> neural crest
where are melanocytes located?
stratum basale or the bottom of the epidermis
are melanocytes uniform throughout the skin?
no we have more in our foreheads and places that have increased sun exposure. they’re a form of protection
where is the one place in the body that has increased melanocytes even though it isn’t exposed to the sun?
the male scrotum and its so it looks physically more appealing
does every human have the same number of melanocytes?
yes the total number of melanocytes is uniform in all humans (a black person doesn’t have more than a white person)
do melanocytes form junctions with surrounding keratinocyte cells?
no
where do melanocytes attach
attach and rest on the basement membrane by hemidesmosomes so they do attach just not with other cells
where do melanocytes extend to
extend out of the stratum basale and into the spinosum (penetrating in between the individual cells)
what are melanosomes?
membrane bound vesicles that hold melanin so they are not free in the cytoplasm
stage 1 melanosomes
golgi a 250nm membrane bound vesicle that arises from the golgi apparatus (membrane bound, secretory) variety of proteins like the enzyme tyrosinase
stage II melanocyte
structural protein builds a grid like structure that has a periodicity, framework for how melanin will be deposited
what’s another word for a stage II melanosome?
premelanosome
stage III melanosome
Over time, the stage II melanosomes take up the amino acid tyrosine. The enzyme inside is the tyrosinase, which converts the tyrosine into DOPA, which then is converted to melanin. This melanin is deposited on the surfaces of the previous frameworks. When the melanin becomes visible, we have a stage III melanosome.
Stage IV melanosome
When enzyme activity disappears, and now its a mature melanosome filled with melanin. These mature melanosomes are transported into the cell processes where they are transferred to the surrounding keratinocytes (stratum spinosum). This is done through a process called cytocrine secretion: a cell to cell transfer where the melanosomes never enter the extracellular space, and the process involves the phagocytosis of this. Melanin is made by melanocytes, but our skin’s pigmentation is a result of melanin in the keratinocytes.
whats another name for Langerhans cells
epidermal dendritic cells and antigen presenting cells
How numerous are Langerhans cells?
least numerous in the epidermis account for 3% of the total cells
where do you find langerhan cells?
in the middle or center parts of the epidermis known as the epidermal ridge or reed ridges which is epidermal tissue, surrounded by cells of the stratum spinosum
where do langerhan cells arise from
blood cells in bone marrow, which come from the mesoderm that differentiates forming langerhan cells, migrate out of the bone marrow and into the epidermis at the center of a reed ridge
what do langerhan cells belong to
the mononucelar phagocytic system (MPS) of cells so they are macrophages
what is the function of langerhan cells
monitor the epidermis for antigens that are passing through the skin, if they encounter an antigen, it will be phagocytized, broken down into smaller fragments and be displayed on the cell surface, it will then migrate out of the epidermis to the lymph node, where it feeds the lymphocytes and will respond to the digested antigen information (antigen presenting cells: ACP)
what immune response are langerhan cells involved in
involved in an immune response called the delayed type hypersensitivity reaction, it includes contact dermatitis (poison ivy)
what is something thats unique to langerhan cells
Birbeck granules: In the cytoplasm we find small membranous inclusions, but we don’t know what they do
whats another name for merkel cells
epidermal tactile cell
how numerous are merkel cells
second most numerous in the epidermis 8%
origin of merkel cells
Epithelial cell origin but not 100% sure: modified basal cells found in the stratum basale
what are merkel cells cell processes similar to
dendrites on a cell body
which epidermal cell is the only one that attaches to keratinocytes
Merkel cells are attached to the surrounding keratinocytes by desmosomes
how big are merkel cells
small secretory vesicles less than 100nm in diameter
what are merkel cells classified as
dense core neurosecretory granules and contain catecholamines: epinephrine and norepinephrine
function of merkel cells
specialized for light touch, sensory neurons, and pseudo-unipolar neurons. The catecholamines function as neurotransmitters, and we have a specialized epidermal cell functioning as a sensory receptor
what is the merkels corpusule
the sensory pseudounipolar neuron + merkel cell. classified as a mechanoreceptor specialized for light but we find them in our fingertips
what are the three receptors in the skin
free nerve endings, pacinian corpusle, and messiners corpusle
free nerve endings
penetrate into the epidermis and go as far up as the stratum granulosum. Free in this term means the endings are naked not capsulated. Free nerve endings have a broad range of senses including pain: nociceptors. Free nerve endings are the most numerous in the epidermis
pacinian corpusle
encapsulated deep in the dermis, down by the hypodermis, because its so far we need additional pressure to stimulate these
messiners corpusle
encapsulated, sensitive to lighter pressure because located in the tips of the dermal papilae
what are Langerhan cells similar to
similar to melanocytes and dendrites
