Topic 6 - The skin Flashcards
What are the 3 main functions of the skin?
- Protection = barrier from mechanical impacts/pressure, temp changes, micro-orgs, radiation & chemicals
- Regulation = (homeostasis sorta) inc. body temp (sweat & hair), changes in peripheral circulation & fluid balance (sweat)
- Sensation = extensive networks of cells that detect & relay changes in environment
What are the layers of the skin?
- Epidermis = upper layer, mostly made of squamous cells (flat/scale-like), then basal cells. Also has melanocytes (protect melanin)
- Dermis = inner layer, contains blood/lymph vessels, hair follicles & glands (produce sweat & sebum- oily stuff)
*Note: under dermis is fatty tissue
What is the epidermis composed of?
-95% composed of keratinocytes
- melanocytes
- Langerhans cells
- Merkel cells
What is the base layer of the epidermis made up of and why is it important?
- Made up of basal keratinocyte cells
- Important b/c its the only cells of epidermis that can divide (mitosis). Divide to form keratinocytes of stratum spinosum (migrate towards skin surface)
What are the 4 layers of the epidermis?
- stratum basale (innermost/base layer)
- stratum spinosum (next layer)
- stratum granulosum (2nd outermost layer
- stratum corneum (outermost layer)
*As older cells move through layers, change shape & nuclear/chemical composition
*Note: palms of hands & soles of feet have extra layer = stratum lucidum
What important protein do keratinocytes produce and its role?
- produces keratin
- keratin = makes skin tough & provides protection from micro-orgs, physical harm & chemical irritation
What are the cells in the stratum corneum & their structure/role?
- Keratinocytes called corneocytes
- Structure = devoid of nucleus & almost all H2O. They’re filled with keratin
- Role = hard protective layer surrounded by lipids (repel water)
*Note: corneocytes shed into environ. e.g dandruff or dust
*Note: cycle of keratinocytes takes 25-45 days
What does the dermis contain & their functions?
- Nerve endings = sense pain/touch/pressure/temp.
- Blood vessels (provide nutrients & assist regulate body temp)
- sweat glands & oil glands (sebaceous)
- hair follicles
What are the skin appendages?
- Sweat glands
- sebaceous (oil) glands
- hair follicles
- nails
What do sweat glands do?
- produce sweat (composed of H2O, salt & other chemicals) in response to heat & stress
- It’s regulated by sympathetic nerves
What do Sebaceous glands do?
- secrete sebum into hair follicles
- acts to lubricate stratum corneum to prevent it dying & cracking
*sebum = oil containing triglycerides, free F.acids & wax esters (also has antibiotics to help bacteria invasion)
What do hair follicles do?
- produce various types of hair
- Has dermal papilla cells (constructs hair shaft)
- Hairs = protection from injury, enhance sensation & reg. body temp
- Goosebumps = sympathetic nerves connected to arrector pills (which will contract for goosebumps)
What do nails do?
- hard translucent structure made of keratin
- facilitate fine pinching & grasping movements
What are the phases of the Hair growth cycle?
- Anagen phase = growth phase (grows 1/2 inch/mth for around 3-5yrs)
- Catagen phase = transitional phase (end of anagen phase - lasts 10 days)
- Telogen phase = resting phase (hair released & falls out - follicle remains inactive 3mths & then restart process)
*Note: each hair follicle goes through cycle at diff. times
What is Acne?
- skin condition from clogged skin pores
- caused by overproduction of sebum & keratin (forms keratinous plugs)
What is sunburn?
- radiation burn of skin caused by ultraviolet rays (commonly from sun)
- causes redness, soreness, tenderness & occasionally itchiness
- can cause permanent damage to skin (e.g early wrinkling & increase risk skin cancer)
What is eczema?
- long-term condition affecting skin
- occurs b/c hypersensitivity reaction (could be dyes, fabrics, soaps, animals etc.)
- Appears on skin as red, inflamed, peeling, cracked, blistered or pus-filled (generally X covered with scaly dead skin)
- Can be anywhere on body & cause intense itching (causes damage to skin)
What is psoriasis?
- A chronic autoimmune condition & results in overproduction of skin cells
- T-lymphs cause release growth factors
- dead cells build up (too many produced) & look like silvery-white scales
- has raised lesion appearance
- skin becomes inflamed & red -> itching
What is fungal infections?
- Caused by diff. types of fungi
- many don’t cause issue when on skin (can be there for yrs)
- factors weakening immune system (e.g stress) can cause fungi to overgrow -> infection
- invade & grow in dead keratin
- localised & tend located in moist areas of body (circles sometimes)
