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Seven Functions of Skin

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Presentation on theme: "Seven Functions of Skin"— Presentation transcript:

1 Seven Functions of Skin
Mechanical/Chemical damage – keratin toughens cells; fats cells cushion blows; and pressure receptors measure damage Bacterial damage – skin secretions are acidic and inhibit bacteria. Ultraviolet radiation – melanin produced to protect from UV damage

2 Thermal control – regulates body temperature
Heat loss: sweat to cool the skin Heat retention: prevents blood from losing heat & shivering Waterproofing – contains lipids to prevent drying out Excretion of waste – urea and uric acid secreted in sweat Makes vitamin D – changes cholesterol molecules in skin and converts it to vitamin D

3 Skin Structure Epidermis — outer layer Dermis – middle layer
Subcutaneous tissue – deepest layer also referred to as the ‘hypodermis’

4 A cell takes 40 – 56 days from creation to sloughing off
Epidermis Summary of layers from deepest to most superficial: Stratum basale Stratum spinosum Stratum granulosum Stratum lucidum Stratum corneum A cell takes 40 – 56 days from creation to sloughing off

5 Layers of the Epidermis
Stratum basale Deepest layer of epidermis Cells actively undergoing cell division New cells push older cells upward until they eventually fall off Cells are mostly keratinocytes and some melanocytes

6 Keratinization Keratin is a protein that helps harden skin cells, makes them tougher and helps prevent water loss by the body. Keratinocytes are responsible for making keratin Keratin makes the skin waterproof Keratin is found in cells of the basale and spinosum strata

7 Stratum spinosum – Made of keratinocytes
Some cells grow projections that connect to other cells making the cell layer stronger Prickle Cells with long projections Stratum granulosum – mostly flattened keratinocytes that have lost nuclei and organelles Death zone of keratinocytes

8 Vitamin D Production Cells of stratum spinosum and basale: Vitamin D:
UV energy + cholesterol = Vitamin D Vitamin D: used by kidney to make the hormone calcitriol Calcitriol: necessary to signal small intestine to absorb calcium from the blood No Vitamin D  no calcitriol  no calcium absorption  weak bones

9 Stratum lucidum Formed from dead cells of the deeper layers Occurs only in thick, hairless skin of the palms of hands and soles of feet Stratum corneum Outermost layer of epidermis Scale-like dead cells are filled with keratin which is a strengthening protein also preventing water loss from skin

10 Layers of Skin No Lucidum Layer

11 Melanin Pigment (melanin) produced by melanocytes
Melanocytes are mostly in the stratum basale Color is yellow to red to brown to black

12 Melanocytes: Cells deep in the epidermis and dermis that produce a pigment called melanin which protects the cells from UV damage Skin color determined by the size and quantity of melanin granules in the tissue

13 What’s your color? Determined by genetic, environmental, and physiological factors Your DNA determines how much MELANIN is produced UV radiation increases melanin production Circulation, vitamin deficiencies, physical ailments (liver failure)

14 Why the Spots…? Large amounts of melanin occur in some regions like freckles, moles, and nipples. Caused by uneven distribution of melanin Less melanin occurs in the lips, hands, and soles of the feet.

15 Albinism A single gene mutation can cause a deficiency or complete absence of melanin. Albinos have fair skin, white hairs, and unpigmented eyes (eyes appear red)

16 Fingerprints The up and down border between the dermis and epidermis helps bond the layers together In thick skin, epidermal ridges show on the surface as fingerprints: Function – enhance gripping

17 Dermis – the middle layer
Papillary layer: Thin (20%) Consists: Contains dermal papillae Capillaries, sensory neurons Function: feed epidermis Reticular Layer: Thick (80%) Elastic and Collagen fibers Sweat and oil glands Deep pressure receptors Function: provide strength and flexibility

18 Dermal Papillae small, nipple-like extensions of the dermis into the epidermis Blood vessels nourish all hair follicles and bring nutrients and oxygen to the lower layers of epidermal cells

19 What makes us stay young looking?
Elastic fibers gives skin elasticity fibers can stretch up to 1.5x their length and snap back to their original length when relaxed Collagen fibers gives skin support/firmness ~ one quarter of the human body is collagen support the skin’s mechanical strength and texture

20 Sensory Perception in Skin
Skin is highly sensitivity to touch because of large amounts of sensory structures found in dermis

21 Sensory Perception in Dermis
Merkel cells: deep layers of epidermis superficial touch Free Nerve Endings: superficial dermis pain and temperature Meissner’s Corpuscles: superficial dermis light touch Pacinian Corpuscles: deep dermis - pressure and vibrations

22 Skin Structure Subcutaneous tissue (hypodermis) is deep to dermis
Not part of the skin Anchors skin to underlying organs, bones and muscles Contains half of the body’s fat; acts as padding and insulation.


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