Lecture 9 - Lecture 9 Integumentary System (Ch. 5) Cell...

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Lecture 9 - Integumentary System (Ch. 5) 14:22 Cell that are located in our stratum basale / stratum germinativum: Melanocytes Merkel Cells Basal Cells (stem cells) Question: All of the following cells are found in the most visceral layer of the epidermis except? All of the following cells are found in the layer of the epidermis that is connected to the basement membrane except? The layer of the epidermis that has ‘intergrens?’ - there are : Stem Cells = Basal Cells Melanocytes Merkel Cells = Mechanoreceptors Other Mechanoreceptors: - Meissner Corpusles - Pascinian Corpusles Melanocytes: - interesting cells that contain vesicles
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- these vesicles called melanosomes - melanosomes contain: o the amino acid – tyrosine o the enzymes – tyrosinase this stuff comes from golgi apparatus the golgi apparatus pinches off this vesicle called a melanosome that contains this amino acid and enzyme o Deep down in the stratum basale the enzyme is not active because it has to be actived by UV light to be activated. o Therefore, it needs to be moved up higher in the epidermis o The melaocyte reaches out these cytoplasmic projections and in these cytoplasmic projections are these melanosomes o Then, through a process called Cytocrine secretion these vesicles are picked up by these spinosome cells o Stratum Spinosome cells, right above the stratum ed off o Bottom line: the vesicle ends up IN the spinsome cell o Now, the spinosome cells contains these melanosomes o Then the melanosomes migrate towards the nucleus of the spinosome cell They are able to migrate to the nucleus by ‘jumping’ on a microtubule and are trafficed up there o Now the melanosomes are surrounding the nuclei of the spinosome cells forming a solar shield o It forms the solar shield by inpeding light because when light hits the melanosomes it activates the enzyme tyrosinase by UV light We have other enzymes in our skin that are UV activated, that allow us to make Vitamin D o The activated enzyme then converts the amino acid in the melanosome to a brownish/black pigment melanin (Melanin is a derived form of tyrosine) o There now there is a bunch of brownish/black pigment that is surrounding the nuclei in your stratum spinosum, which impeds light from moving any further in to the skin because light will be refracted
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o Now the UV cannot reach these cells deeper down in the epidermis that are dividing VERY important because if dividing cells are exposed to UV light we can form cancer very easily! VERY easy to cause DNA damage with UV light! o So we have this natural UV protection but the only way we can activate it is by exposing our skin to UV light So, by activating the enzyme by exposing it to light, tyrosine is converted to melanin, which acts as a sun block and protects our nuclei from UV damage At some point lysosomes fuses to melasomes and degrade all the melanin o When lysosomes fuse to melanosomes and degrade melanin they cause people’s skin to be a lighter pigmentation
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Lecture 9 - Lecture 9 Integumentary System (Ch. 5) Cell...

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