Skin Flashcards
Functions of skin
Protection against chemical, thermal and mechanical insults, bacterial and fungal invasion, dessication and uv light
Has sensors for touch, pressure, pain and temperature
Thermoregulation
Production of vitamin D3
Significant energy store
Layers of skin
Epidermis, dermis and hypodermis
Epidermis
Composed of keratinised stratified squamous epithelium
Dermis
Composed of a layer of fibrocollageous and elastic connective tissue that contains blood vessels, nerves and sensory receptors
Hypodermis
Composed mainly of adipose tissue
Varies in thickness
Scattered septa made up of bundles of collagen
What is the function of septa in the hypodermis
Help anchor the skin to the underlying deep fascia
Layers of the epidermis
Stratum basale, stratum spinosum, stratum granulosum and stratum corneum
What is a possible 5th layer of the epidermis
Stratum lucidum
Statum basale
Single layer of cells sitting on basal lamina
Stem cells for the epidermis
Stratum spinosum
5 cells thick
Many desmosomes attaching cells to each other
Stratum granulosum
Cells aquire large numbers of dense cytoplasmic granules
Cells produce lamellar bodies
Further up the layer, the cells gain more keratin and organelles are being progressively lost
Stratum corneum
Composed of dead squamous cells packed with keratin in a specialised matrix
What are the dense cytoplasmic granules called
Keratohyalin granules
What do keratohyalin granules contain
Profilaggrin
What does profilaggrin promote
The aggregation of cytokeratin intermediate filaments
Aggregations of cytokeratin intermediate filiments known as
Keratin
Stratum lucidum
Thin layer found only in thick skin consisting of dead cells with abundant keratin
Non-keratinising cells of epidermis
Melanocytes, langerhans’ cells and merkel cells
Melanocytes
Many long cell processes
Produce melanin
What does melanin complex with and what does it form
Proteins to form melanoprotiens
What are melanoprotiens passed to and through
Keratinocytes and through granules called melanosomes
Two forms of melanin
Pheomelanin and eumelanin
Langerhans’ cells
Resident immune cells
Act as antigen presenting cells
Have a network of cell processes to increase surface area
Numbers increase during inflammatory conditions
Invade the skin from the blood stream
Merkel cells
Touch receptors found in basal layer of epidermis
Associated with a nerve ending and form low threshold/slowly adapting receptors
Two layers of dermis
Papillary dermis - superficial
Reticular dermis - deep
Papillary dermis
Forms dermal papillae which project upwards and interdigitate with downwards projections of the epidermis called rete ridges
Consists of bundles of fine collagen and elastic tissue
Reticular dermis
Forms dense irregular connective tissue with thick bundles of collagen fibres and elastic fibres embedded in small amounts of extracellular material
Other name for hypodermis
Subcutis
Epidermal skin appendages
Hair follicles, sebacous glands and sweat glands
Hair follicles
Tubular structure extending down through the epi into the dermis and hypo
Has 5 layers
At the bottom extension = hair bulb
Concave region = dermal hair papilla
Sebaceous gland
Usually associated with hair follicle
Produce sebum
Utilise holocrine secretion
Arrector pili muscles
Associated with hair follicle
Small band of muscle
Runs obliquely upwards and ends in upper part of dermis
Innervated by sympathetic nervous system
Sweat glands
2 types - eccrine and apocrine
Coiled tube located near junction of dermis and hypo
Made up of secretory and duct segements
Secretory segment of sweat gland
Coiled tubular gland
Pseudostratified epithelium
Duct segment of sweat gland
Initially coiled but then straightens
Stratified cuboidal epithelium
Apocrine sweat glands
Restricted to axillae, genitalia and areolae of the nipple Produce a milky fluid Ducts typically end on hair follicles Secretory sections have large lumen Utilise merocrine secretion
Nails
Hard plates of keratin
Formed by cells of the nail matrix
Nail bed is analogus and continuous with epidermis
Visible half moon portion of nail matrix
Lunula
Sensory receptors of skin can be classified by
Free nerve endings or encapsulated nerve endings
Free nerve endings form
Meissner’s corpusce
Encapsulated nerve endings from
Pacinian corpuscle
