Lecture One - Skin Flashcards
How much of your body weight is contributed by skin
16%
How much surface are does skin cover
1.5-2m^2
Why did we adapt to have bare sweaty skin
- climate change meant we started running in open grass land
- no hair meant efficient heat loss - through sweat glands
Functions of skin and accessory structures
- Protect underlying tissue and organs from impact, abrasion, fluid loss and chemical attack
- Ecrete salt, water and organic wast through intergumentary glands
- Maintain a constant body temperature through evaporative cooling and insulation
- Production of melanin which protects underlying tissue from ulatraviolet radiation
- Produciton of keratin which protects from abrasion and serves as a water repellant
- Synthesis of vitamin D3, a steroid which is subsequently converted into calcitriol, a hormone important to normal calcium metabolism
- Store lipids in adipocytes in the dermis and in adipose tissue in the subcutaneous layer
- Detect touch, pressure, pain and temperature stimuli, and reply that information to the nervous system
Skin is a ____ organ
- composite
- made of all tissue types
Primary layers of the skin
- epidermis (cutaneous)
- dermis (cutaneous)
- hypodermics (subcutaneous)
Features of the epidermis
- stratified barrier
- mostly keratinocytes
- no blood circulation (avascular)
Features of the dermis
- protein fibres for strength (collagen and elastin)
- vascular (nourishes epidermis)
Features of the hypodermis
- adipose tissue
What is the predominant tissue of the epidermis
Epithelial tissue
What kind of epeithelia is the epidermis made of
Stratified squamous epithelium
Simple squamous
Simple Cuboidal
Simple columnar
Stratified squamous
Stratified cuboidal
Stratified columnar
Layers of the epidermis (thin skin)
Stratum cornerman
Stratum granulosum
Stratum spinosum
Stratum basale
Stratum cornerman
- dead, dried out hard cells without nuclei
Stratum granulosum
- contain granules that promote dehydration of the cell, cross linking of keratin fibre
- waxy material is secreted into the intercellular spaces
Stratum spinosum
- intercellular brindles called desmosomes link the cells together
- the cells become increasingly flattened as they move upward
Stratum basale
- columnar (tall) regenerative cells
- as the basal cell divides, a daughter cell migrates upwards to replenish the layer above
Desmosomes
Anchours adjacent/ neighbouring cells in epidermis
Hemidesmosomes
Anchors stratum basale to the dermis
How thick skin differes from thin skin
- no hair
- extra epidermal layer (stratum lucidum)
Where is thick skin found
- palms of hands and soles of feet
Layers of the epidermis (thick)
Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basale
Layers of epidermis
Stratum corneum
Stratum granulosum
Stratum spinosum
Stratum basale
Features of the dermis
- situated below the epidermis and anchors via hemidesmosomes
- doesn’t get shed
- divided into two layers: papillary layer and reticular layer
Pappilary layer
Consists of highly vascularised tissues (for nourishment)
Reticular layer
‘Mesh-like’ structure of collagen and elastin fibres (for strength)
Similarities between reticular and papillary layer
Both layers contain:
- blood vessels
- lymphatics
- sensory nerve fibres
- accessory structures
Plexuses of the dermis
Cutaneous plexus
Subpapillary plexus
What is the cutaneous plexus and what does it do?
- a network of blood vessels present at the junction of the dermis/ hypodermis
- supplies the hypodermis, deeper dermis, including the capillaries for hair follicles and sweat glands
Subpapillary plexus
- branches from the cutaneous plexus
- lies deep to the papillary layer of the dermis
- network of blood vessels providing O2 and nutrients to the upper dermis and epidermis
Features of the hypodermis
- the subcutaneous layer
- is a part of the skin
- dominated by adipocytes that produce subcutaneous Fat
- the subcutaneous fat stores energy and provides insulation
- common site of injections using hypodermic needles
First degree burn
- superficial - only in love the outer layers of the epidermis
- red/pink, dry, painful
- usually no blisters e.g a mild sunburn
- skin remains a water and bacterial barrier
- usually heals 3-10 days
Normal second degree burn
- epidermis and varying amounts of dermis effected
- painful, moist, red and blistered
- usually heal in approx 1-2 weeks
Deeper second degree burns
- may include whiteish, waxy looking areas
- hair follicles, sweat glands may remain intact
- usually heal in one month
- may have some loss of sensation and scarring
Third degree burn
- full thickness burns ie extend into subcutaneous tissue and may involve muscle and bone
- varied colour from waxy white through to deep red or black
- hard, dry and leathery skin
- no pain in these areas as sensory nerve endings are destroyed
- may require skin graftin
- weeks to regenerate + scarring
