Skin Flashcards
What is the epidermis made up of?
Stratified squamous keratinising epithelium
What are the 8 functions of skin?
protection control of evaporation sensation absorption manufacture of vitamin D Thermoregulation Storage and synthesis Excretion
How does skin act as protection?
an anatomical barrier
langerhans cells in the skin are part of the adaptive immune system
How does skin control evaporation?
Provides a relatively dry and semi-impermeable barrier to reduce fluid loss and prevent dehydration
How does the skin show sensation?
Variety of nerve endings that respond to hot and cold
pressure , vibration , and tissue injury
How does the skin absorb?
route of exposure for bioactive substances including medications
What is the role of skin on the manufacture of vitamin D?
Vitamin D3 is synthesised when exposed to UV radiation mainly in the keratinocytes
What is the role of skin in thermoregulation?
Sweat glands and dilated blood vessels aid heat loss while constricted vessels greatly reduce cutaneous blood flow and conserve heat
What is the role of skin in storage and synthesis?
Acts as a storage centre for lipids and water
What is the role of skin in excretion?
Sweat glands excrete perspiration through skin pores.
What are the three primary layers of skin?
Epidermis
Dermis
Hypodermis
What is the dermis made up of?
Dense irregular CT abundant in collagen
What is the hypodermis made up of?
Adipose Tissue
How many layers in thick skin?
5
How many layers in thin skin?
4
What are the 5 layers and which is only present in thick skin?
Stratum Coreum Stratum Lucidum (thick skin only) Stratum Granulosum Stratum Spinosum Stratum Basale
Describe the stratum corneum?
Surface stratum- cells have no organelles-almost entirely composed of keratin
Describe the Stratum lucidum?
Thick skin only and not always observed
Describe Granulosum
2-3 layers of flattening cells ; granules contain a lipid rich scecretion, which acts as a water sealant
Describe the stratum spinosum
2-8 layers: “prickle cells”; desmosomes and tonofilaments
Describe the stratum basale
Deepest stratum; single layer of cubodial cells; hemidesmosomes bond layer to basal lamina and dermis. It is here that new cells are generated for the renewal of the epidermal layers of skin
lots of mitosis occurs here and the cuboidal cells are tightly packed together
What are the four cells of the epidermis?
Keratincoytes
Melanocytes
Langerhans cells
Merkel cells
What is the role of keratinocytes?
Make up the majority of cells - produce keratin
What is the role of melanocytes?
Synthesis of melanin- skin colour is due to the production and breakdown
What is the role of langerhans cells?
Antigen presenting cells
What is the role of merkel cells?
sensitive mechanoreceptors essential for light touch sensation
Describe the stages of keratinocyte development
Proliferation- DNA synthesis and mitosis
Early differentiation- growth arrest, exit from cell cycle
Intermediate differentiation- reinforcement of the cytoskeleton
Late differentiation- expression of late markers
Cornification- Cornified cell envelope- nuclear breakdown
What are the two indistinct layer of the dermis?
Papillary layer(superficial) and reticular layer (deeper)
How does skin become wrinkled?
With age collagen and elastin breaks down
What is hypodermis also known as?
Subcutabneous tissue
What is the role of the hypodermis?
Provides padding to the body and helps skin anchor to underlying tissue
What appendages are there on the epidermis?
Sweat glands
Hair follicles
Sebaceous glands
What are two sweat glands present on the epidermis and where are they located?
Merocine- highest density in palms and soles
Apocrine- axillary and anogenital regions
What smooth muscle attaches to hair follicles?
Arrector pili
What do sebaceous glands do?
Secrete sebum into base of hair follicle
sebum softens & lubricates hair and skin
prevents brittleness, slows water loss and kills bacteria
What are hair follicles?
Hairs are elonagted keratinised structures that form within epidermal invaginations
What is acne vulgaris?
An inflammatory disorder of the pilosebaceous unit occuring during adolescence.
What are the three unencapuslated receptors?
Merkel cells
Freee nerve endings
Root hair plexuses
What are the four encapsualted receptor?
Meissner corpuscles
Pacinian corpuscles
Krause end bulbs
Ruffini corpuscles