L5. The Skin Flashcards
Skin structure
Basic Structure:
- Epidermis
- Dermis
- Hypodermis
Accessory Structures:
- Hair
- Hair Follicles
- Sweat glands
- Sebaceous glands
- Nails
L.O.
- To recognise the main layers of skin
- To describe the major constituents of skin
- To outline the major functions of skin and skin cells
- To understand at a very basic level how the skin barrier can be compromised
Skin functions
- Largest organ of body
- 15-20% of total body mass
Functions:
- Physical Barrier
- Thermoregulation
- Sense organ
- Immunological
- Vitamin D production
- Excretion
Epidermis
- The most superficial layer = protective
- Keratinocytes are the main cell type
- Cells differentiate as they move up the layers of the epidermis until they are eventually exfoliated from the top layer
- Thicker in some areas with no hair follicles, eg palms and soles
Cells of the epidermis
- Keratinocytes (Barrier, external ~85%)
- Melanocytes (pigment-producing cells ~5%)
- Langerhans’ cells (Immune cells ~2-5%)
- Merkel’s cells (Sensation ~6-10%)
[SEE HEFT]
Dermatomes
An area of skin that is
mainly supplied by a single spinal nerve
Dermis
- The middle layer = tensile strength and stretch
- Contains collagen and elastin fibres & other structures
- Undulations under microscope between dermis and epidermis create fingerprint
Hypodermis
- Bottom Layer
- Subcutaneous fat, superficial fascia
- Loose connective tissue, adipose tissue
- Anchors to underlying structures
- Energy storage, insulation
- Variable thickness
Skin-associated structures
Apocrine sweat gland
- empties into hair follicle, smelly sweat
Eccrine sweat gland
- totally separate, temperature regulation
Sebaceous glands
- secrete sebum into hair follicle
Arrector pili muscle
- Goosebumps
- contracts sebaceous gland, causing secretion
Nails
- plates of keratinized cells
Nerve endings
- Gives sensation
Nerve endings in skin
Pacinian corpuscles:
- deeper dermis & hypodermis
- Fingertips
- Pressure Changes & Vibrations
Meissner’s corpuscles:
- Top of dermis
- lips, palms
- light touch
Sebaceous glands
- Produce and secrete sebum
- Coats hairs and skin surface by discharging into a hair follicle
- Cells produce sebum then die
Acne formation
- Accumulation of shed dead cells and keratin
- Excess sebum production
- Bacterial proliferation & inflammation
- Severe inflammation and scarring
Sunburn – ultraviolet radiation
- UV range damages dermis and epidermis
[SEE HEFT]
Melanin (Inbuilt Protection)
- Absorbs in UV, visible light
- Transfer melanin to keratinocytes
- Scatter & absorb UV
- Sunburn sensitivity is determined by melanin & skin thickness
Botox
Botulinum toxin blocks nerve
signals that cause:
- muscles to contract (relaxes wrinkles)
- sweat gland activation (to treat hyperhidrosis)
