BIO

• Mark Twain: 'The finest clothing made is a person's own skin, but, of course, society demands something more than this.'
• General Biology 2, Science, Technology, Engineering, and Mathematics
• Skin types


  • All skin types can benefit from daily cleansing and moisturizing, but different skin types—which include oily, dry, normal, combination, and sensitive skin—have different needs. That's why understanding your skin type is the first step in properly caring for it.
  • Although a healthy skin barrier is essential for all skin types, it's also important to remember that each individual's skin is unique in many ways. This means that there's no "one size fits all" approach to achieving radiant, healthy-looking skin.

  
• Integumentary system


  Your body's outer layer

  
• Integumentary system


  • Consists of skin, nails, hair and glands, along with the nerves and blood vessels that support them
  • These organs and structures are your first line of defense against bacteria and help protect you from injury and sunlight
  • The average person's skin weighs 10 pounds
• Functions of the integumentary system

  • Excretion – small amounts of waste products are lost through perspiration
  • Protects underlying tissues and organs
  • Sensation- the sensory receptors, detects touch, pressure, pain, and temperature
  • Inhibits excessive loss of water and electrolytes
  • Body temperature regulation
• Body temperature regulation


  • If too hot, the dermal vessels dilate. Vessels carry more blood to surface so heat can escape (evaporation)
  • If too cold, dermal vessels constrict which prevents heat from escaping (insulation)

  
• Parts of the integumentary system


  • Cutaneous membrane (skin)
  • Accessory structures (hair, nails, exocrine glands)

  
• Skin


  The largest and heaviest organ in your body, weighing about six pounds (or more) and approximately 2 millimeters thick, making up 15% of the total body weight of a human being
• Thick and thin skin


  • Thick skin covers the palms of the hands and soles of the feet, with a thick layer of dead skin called the stratum corneum, rich in sweat glands but lacking oil glands and hair follicles
  • Thin skin covers the rest of the body, rich in sebaceous glands and hair follicles but lacking sweat glands
• Layers of the human skin


  • Epidermis
  • Dermis
  • Hypodermis (subcutaneous tissue)

  
• Epidermis


  The top layer of your skin, made up of three types of cells: melanocytes, keratinocytes and Langerhans, protecting your body from harm, keeping your body hydrated, producing new skin cells and containing melanin, which determines the color of your skin and provides a waterproof barrier

  
• Melanin


  • Eumelanin primarily makes dark colors in your hair, skin and eyes
  • Pheomelanin primarily makes pink or red colors in your body, including lips, nipples, the vagina and the glans penis, as well as hair
• Quartet of epidermal cells


  • Melanocytes
  • Keratinocytes
  • Langerhans cells
  • Merkel cells
• Layers of the epidermis

  • Stratum corneum
  • Stratum lucidum
  • Stratum granulosum
  • Stratum spinosum
  • Stratum basale (stratum germinativum)
• Stratum corneum


  The outermost layer and roughest of the epidermis, exposed surface of the skin, water resistant, shed and replaced every 2 weeks
• Stratum lucidum


  A thin, transparent layer of keratinocytes that are becoming less round and have a flatter shape, only found in the thick skin of the palms and foot soles
• Stratum granulosum


  The "granular layer", looks grainy as cells are getting compressed and flattened as they move up through the epidermal layers, maturing as they go, containing living keratinocytes with granules within them
• Stratum spinosum


  The "spiny layer", helps make your skin flexible and strong, containing Langerhans cells which are active in immune response, closer to the point where cell regeneration, or mitosis, is active
• Stratum basale (stratum germinativum)


  The deepest and thinnest layer of the epidermis, forms epidermal ridges (e.g. fingerprints), where new skin cells develop and it also contains the keratinocyte stem cells and melanocytes

  
• The deeper you go through the layers of the epidermis, the younger the cells get. Regeneration happens in the lower layers, and new cells move up toward the surface, maturing along the way, where they eventually die and slough off from the surface of your skin.
• Ultraviolet radiation in the sun can damage the epidermis, causing elastic fibers to clump up, leading to that tell-tale leather-face condition. Getting sunburned temporarily depresses your immune system—because, remember, you have immune cells in your epidermis too. The radiation can actually alter your skin cells' DNA, leading to skin cancer. Seriously, wear your sunscreen!
• Dermis


  The middle layer of your skin, the thickest layer, containing sweat and oil glands and hair follicles, and housing the nerve fibers that register sensations like temperature, pressure, and pain
• Layers of the dermis


  • Papillary dermis
  • Reticular dermis
• Papillary dermis


  The top layer of the dermis, much thinner than the reticular dermis, consisting of collagen fibers, fibroblast cells, fat cells, blood vessels, nerve fibers, touch receptors and cells that fight bacteria, forming a strong bond with the epidermis
• Reticular dermis


  The bottom layer of the dermis, thick, containing blood vessels, glands, hair follicles, lymphatics, nerves and fat cells, making up 80% of the dermis, with a net-like structure of elastin fibers and collagen fibers that support the skin's overall structure and allow it to move and stretch
• All of the dynamic parts contained within the dermis—like nerve fibers and capillaries—are distributed between both the papillary and reticular layers. So anytime you get cut enough to bleed or feel pain, you know that you've broken through the epidermis and lacerated the dermis. This is the layer that tattoo needles have to reach in order to work: It's the only way to make tattoos permanent, but also it means getting tattoos hurts and bleeds.
• Hypodermis (subcutaneous tissue)


  The innermost layer of skin, the fatty layer that helps insulate your body, store energy, absorb shock and anchor the skin to the muscles and bones
• Nails


  • Protect the ends of your fingers and toes, consisting of the nail plate, nail bed, cuticle, matrix, and lunula
• Hair


  • For covering and protection, made of the protein keratin, consisting of the shaft, follicle and bulb
• Hair follicles sense changes in the surrounding environment and transmit the signal to the neurons in the underlying skin, which then transmit this information via the central nervous system to the brain that facilitates an appropriate reaction. Goosebumps are caused by the hair erector muscles connected to the hair follicles and skin contracting, making the hair stand up.

  
• Glands in the integumentary system


  • Sebaceous glands
  • Ceruminous glands
  • Mammary glands
  • Sudoriferous glands (eccrine and apocrine)
• Sebaceous glands


  Produce sebum (oil) and give the face its oil, secreting sebum into the follicle which flows over the hair keeping it lubricated and soft, protecting the skin from drying out
• Ceruminous glands


  The glands in the ear that secrete ear wax, which plays an important role in protecting the ear canal against physical damage and microbial invasion
• Mammary glands


  The glands on a person's chest that produce milk after giving birth, also called breasts
• Types of sweat glands


  • Eccrine (merocrine) glands
  • Apocrine glands
• Eccrine (merocrine) sweat glands


  Widely distributed on the body surface especially on the palms and soles, cooling the skin by excreting water and electrolytes, flushing microorganisms and harmful chemicals from the skin
• Apocrine sweat glands


  Coiled tubular sweat glands associated with the hair follicles of the skin, found in the skin of the axilla, areola, nipples, and other areas
• Ear canal


  Protects against physical damage and microbial invasion
• Mammary glands


  Glands on a person's chest that produce milk after giving birth in people assigned female at birth (AFAB)