Skin Flashcards
What are the 4 primary tissue types?
- Epithelium
- Connective tissue]
- Muscle
- Nerve
What are epidermal cells termed as?
Keratinocytes
What is the function of the epidermis?
Prevents water loss by evaporation
What are the functions of the dermis?
- Reduces the risk of external injury
- Maintains the epidermis by its blood flow
- Permits body cooling
- Immune surveillance
- UV protection
- Energy storage
- Sensory information
What does the epidermis consist of?
Epithelium which forms boundaries between internal and external compartments
What does the dermis consist of?
Connective tissue which give structural support
How can epithelial be described?
Stratified squamous keratinising epithelium
What kind of origin does epidermis have?
Ectodermal origin
What are the 4 types of epidermal cells?
- Keratinocytes
- Melanocytes
- Langerhans cells
- Merkel cells
Describe keratinocytes.
- Most frequent
- Contain keratin
- Hard and resistant to abrasion
- Extrude lipids making it waterproof
- Constantly dividing
What is the function of melanocytes?
Pigment formation and injection of melanin in the str. germinaticum
What is the function of Langerhan cells?
Immune surveillance
What is the function of Merkel cells?
Touch receptors
What are the 5 layers of the epidermis from outside in?
- Stratum corneum
- Stratum lucidum
- Stratum granulosum
- Stratum spinosum
- Stratum basale
Describe the stratum spinosum.
- Spinous layer
- Cells shrink post mortem and desmosomes create spines
- Little structural evidence of activity
- Preparative layer for keratinisation
Describe the stratum granulosum.
- Presence of granules defines the layer
- Granules of keratohylain
What 2 layers can be difficult distinguish?
Stratum corneum and Stratum lucidum
Describe the stratum corneum.
- Conversion of keratohyalin to keratin
- Lots of disulphide linkages give strength
- No organelles
- Desmosomes bind cells
- Fortnightly turnover
What is keratinisation?
Organic process whereby keratin is deposited in cells and these become horny as in dead skin, nails and hair
How does epidermal thickness vary?
- Palms and soles of feet are thick skin
- Abdominal skin is thin
What are the 2 layers of the dermis?
- Papillary layer
- Reticular layer
Describe the papillary layer
- Loose connective tissue
- Cellular
- Irregular interface with epidermis
- Protective against pathogens
- Contains blood vessels and nerve endings
Describe the reticular layer.
- Dense irregular connective tissue
- Collagen bundles in three planes
- Elastic fibres
How does keratin originate?
Originates as lamellated granules in str. granulosum
How is skin waterproofed?
- Keratin in cells waterproofs
- Intracellular spaces filled with lipid cement
What is responsible for skin colour?
- Blood
- Carotene
- Melanin
What does melanin do?
Protects us against UV
Describe hair in relation to skin.
- Mainly for vanity but has a practical use in skin repair
- Derived from the epithelial layer
Describe the origin of hair follicles.
- From epidermis in utero
- Down growth of epithelial cells
- Invasion of know of blood vessels
- Growth of hair
- Continuity with layers of epidermis
What does a hair follicle consist of?
- Hair and sheath
- Arrector pili muscles
- Sebaceous glands
Describe arrector pili muscles?
- Attached to follicle root and base epidermis
- Follicle at angle
- Hair straightens when muscle contracts
Describe sebaceous glands?
- Between follicle and arrector pili muscle
- Secretes sebum
- Function uncertain
What skin glands are there?
- Sebaceous- hair follicles
- Apocrine sweat glands (BO)
- Eccrine sweat glands
Describe eccrine sweat glands.
- Simple tubular glands
- Located in the dermis
- Coiled secretory portion
- Coiled and straight duct in dermis
- Spiral channel in epidermis
- Watery secretion
- Thermoregulatory
What is involved in thermoregulation/
- Sweat glands
- Blood vessels
- Hair (but not in human)
What sensory endings are there in skin?
- Meissener’s corpuscles: light touch in fingertips
- Paccinian corpuscles: vibration and pressure
- Pain receptors
- Thermoreceptors
