Skin Flashcards
What are the 3 layers of the skin and in which order are they in?
Epidermis (top layer)
Dermis (middle layer)
Hypodermis (lowest layer)
Where is the hypodermis thickest in men and women and in both sexes?
Men - thickest in abdomen and shoulders.
Women - thickest in hips, thighs and buttocks.
Both - thick on palms of hands.
What is the function of the hypodermis?
- Provides an energy store - able to generate heat.
- Insulator for underlying heat generation - e.g. stops heat escaping into upper layers.
- Shock absorber (e.g. fat on buttocks).
- Connects skin to underlying muscle + bone.
- Makes hormones (e.g. leptin to control eating habits).
Describe the structure of the hypodermis?
- Mainly contains adipose tissue - some neurovascular bundles/lymphatics.
- Contains loose connective tissue with fibroblasts, macrophages and fibres.
Describe the structure of the dermis:
Three layers:
- papillary (upper)
- reticular ( lower)
- dermal papillae ( interdigitating (interlocking)).
What are the functions of the dermis layer of the skin?
- Thermoregulation - contains hair + sweat glands.
- contains sensory structures to sense touch.
- give structure to the skin and so body shape.
What are the functions of the epidermis?
- Prevents water loss.
- Prevents entry to bacteria and parasites.
- Special cells that present pathogens to immune cells.
- synthesis of keratin
- prevents underlying tissue loss due to abrasion.
What are the 4/5 layers of the epidermis in skin? Acronym - come lets get sun burnt!
C - Stratum corneum L - Stratum lucidum (transparent layer) - only found on palms and soles of feet. G - Stratum granulosum (granular layer) S - Stratum spinosum B - Stratum basale
Apart from the 4/5 layers of the epidermis, describe its structure:
- Avascular
- Laterally held together by adherens junctions.
- Held together basal apical by desmosomes.
What are the characteristics of the stratum corneum:
- Outermost layer made of squames (dead keratinocytes).
- Continuously sheds.
- Tick on palms and soles of feet - used to be areas prone to injury.
What are the characteristics of the stratum granulosum?
- stratified squamous epithelium layer.
- lamellar granules (filament associates proteins that assemble keratin fibres and release it).
- tonoibrils
What are the characteristics of the stratum spinosum layer?
- cuboidal epithelium arranged in 3 layers (layers held together by desmosomes).
- producers of lamellar bodies.
What are the characteristics of the stratum basale layer?
- tall columnar epithelial cells.
- constantly renew keratinocytes by cell division.
- also home to melanocytes, which produce melanin.
What is the function of keratinocytes?
- To synthesise keratin (fibrous protein) that contributes to the strength of the epidermis.
- Keratin is the main constituents of hair, nails and animal horns.
What types of cells are you likely to find in the epidermis of the skin? What are the functions of each of these?
- melanocytes - produce melanin. (Found in basal layer of epidermis).
- keratinocytes - synthesise keratin fibres.
- langerhans’ cells - mediate immune reactions e.g. during allergic contact dermatitis. Found in the stratum spinosum.
Describe the main nerve cells found in the skin?
- Pacinian corpusles - percieve deep pressure and virbrational changes.
- Ruffini endings - detect deep pressure and stretching of the skin’s collagen fibres (joint movement and tissue stretch).
- Merkel receptors - associates with Merkel cells. Respond to sustained light touch on skin.
- Free nerve endings - have nociceptors that respond to pain.
- Krause end bulbs - have thermoreceptors that respond to temperature variations.
- Meissner receptors - detect light touch.
Explain the process of making the keratin layer of the skin:
- Undergo mitosis in the basal layer.
- Daughter cells move up through the prickle layer (stratum spinosum).
- As they migrate the keratinocytes lose their ability to divide and their nuceli, eventually forming the horny layer (stratum corneum).
- This layer provides a barrier for the skin due to the amounts of keratin.
Where would you find non-hairy (thick) skin?
- palmar surface of hand.
- plantar surface of the foot.
- area between fingers and toes (webs).
What is the structure of non-hairy thick skin?
- same as rest of body
EXECPT - no hair, no arrector pili muscles, no sebaceous glands. - thinner dermis
- increased density of mechanoreceptors.
- thicker stratum corneum.
What is the function of non hairy (thick) skin?
- Prevent tissue loss due to abrasion.
- Increased friction between skin and surfaces.
- Increased sensation.
Name some functions of the skin:
- Storage (white adipose cells provide lipids)
- Lubrication (sebaceous glands release oil onto surface).
- Temperature regulation and excretion of waste products (sweat glands - NaCl and water, urea).
- Protection and repair (wound healing - fibroblasts) (UV protection by melanocytes)
- Vitamin D synthesis.
- Absorption
- Sensation (due to specialised structures called mechanoreceptors).
- Absorption (absorb small amounts of water and oxygen).
Describe the structure of hairy skin:
- Presence of hair follicles, sebaceous glands and arrector pili muscles.
- Stratum lucidium absent.
What are skin appendages and give examples of some of these:
- They are skin associated structures that serve a particular function.
- hairs, arrector pili, sebaceous glands, sweat glnds and nails.
What are the 3 hair types and describe where each of these are found:
Lanugo - covers the developing foetus.
Vellus - replaces lanugo. Short, thin, light coloured and soft.
Terminal - head (scalp, eyebrows, nasal passage), external genital region. Long, wide, dark coloured and coarse.
Give some functions of hair:
- Thermoregulation.
- Partial barrier to UV rays e.g. hair on scalp.
- Sexual attraction
- sensation (sensory endings within the bulb)
- protection (eyelashes and nasal hair prevent pathogen entry into body, eyebrows reduce amount of sweat entering the eye).
What are the functions of nails?
- Protection of surrounding soft tissues from injury.
- Enhance precise delicate movements.
- Enhance sensitivity of the fingertips.
Where are sebaceous glands found?
All over the skin except in the palms of hand and the soles of the feet.
What is the difference between eccrine sweat glands and apocrine sweat glands?
- Eccrine sweat glands have a water based secretion (so are significant for cooling) and are found all over the body.
- Apocrine sweat glands are limited to the axilla (armpit) and perianal areas. Not significant for cooling - secrete oily sweat fluid.
What name would you give to a structure consisting of hair, hair follicle, arrector pili muscle and sebaceous gland?
Pilosebaceous glands
