Skin Flashcards
What are the four primary tissues that form skin?
Epithelium
Connective
Muscle
Nerve
Does skin have its own nerve and blood supply?
Yes
What are the three main layers of skin?
Epidermis
Dermis
Hypodermis
What is the epidermis layer of skin?
Formed from epithelium tissue.
Top layer
Stratified, which means cells form more than one layer
Formed from five layers which are stratified too
Ectodermal origin
What is the function of the epidermis layer?
Form boundaries between the internal and external environment
Prevent water loss by evaporation
What is the dermis layer of skin?
Layer underneath epidermis.
Formed from connective tissue.
What is the function of the dermis layer?
Give skin structural strength
Reduce risk of external injury
Permit body cooling
Maintain the epidermis by its blood flow
What is the hypodermis layer of skin?
Layer underneath skin.
Adipose layer
What is the function of the hypodermis layer?
Anchor skin to underlying structures
What are the four main functions of skin?
Immune surveillance
UV protection
Energy storage
Sensory information
What are the five layers of the epidermis?
Stratum basale
Stratum spinous
Stratum granulosum
Stratum lucidum
Stratum corneum
What are the four basic cell types that form the epidermis?
Keratinocytes
Melanocytes
Langerhan Cells
Merkel Cells
What are keratinocytes?
Most frequent cell type in epidermis.
Contain keratin, makes skin resistant to abrasion as it makes it hard.
Extrude lipids, which allows the cells to be waterproof
Constantly divide and regenerate which allows them to protect the skin from any damage
What are melanocytes?
Allow pigment formation
What are Langerhan cells?
Allow immune surveillance
What are Merkel cells?
Touch receptors
What is each epidermal layer formed from?
Squamous keratinising epithelium tissue.
Maturing keratinocytes from the basement membrane of the dermis
What is the stratum basal layer? What is its function?
Bottom layer
Formed from tall columnar cells
Cells are bound to the basement membrane through hemidesmosomes
Basement membrane allows the cell to form connections with the top dermis layer, the dermal papillae. Keeps skin together.
Continuously proliferates stem cells
What is the stratum spinosum layer? What is its function?
Cells in this layer shrink, meaning that their desmosome junctions form ‘spines’
Prepares for keratinisation
What is the stratum granulosum layer?
Cells within this layer contain granules of keratohyalin
What are the stratum lucidum and corneum layers? What are their functions?
Cells within these layers do not have any organelles and are bound together through desmosomes. There are also lots of disulphide linkages, which add to the layers strength.
These layers are replaced every 15-30 days.
Convert keratohyalin to keratin through a process known as keratinisation
What is psoriasis?
Autoimmune condition where the skin over produced keratin.
Why does the thickness of the epidermis and dermis vary around the body?
Dynamic tissue that responds to activity changes
Mainly due to stratum corneum
What are the two layers of the dermis?
Papillary layer
Reticular layer
What is the papillary layer?
Top layer of dermis
Composed of loose regular connective tissue - smooth
Filled with blood vessels
Nerve endings present
Connects with the bottom epidermis layer, status basale
What is the function of the papillary layer?
Protect the skin from any pathogens
Thermoregulation and supplies nutrients
What is the reticular layer?
Bottom layer of dermis
Composed of dense irregular connective tissue - rough
Fibrous layer - formed from collagen fibres and elastic fibres. Give skin its elastic property
How is skin waterproof?
Epidermis layer contains keratin and lipids
What is skin colour due to?
Blood, carotene and melanin
Melanocytes in the stratum basale produce melanin
What is the function of hair on our skin?
Thermoregulation
Skin repair
How are hair follicles formed in the skin?
Derived from epidermis layer, in utero
Form as a result of down growth of epithelial cells, which are then invaded by a knot of hair cells.
What are arrector pilli muscles? What are their function?
Attached to hair follicles and the base of the epidermis
Hold the hair follicle at a particular angle and straightening this follicle when the muscle contracts
Sebacous glands are found between the follicle and the arrector pilli muscle . They secrete sebum.
How is thermoregulation of skin obtained?
Sweat glands
Hair
Vessel dilation
What are the steps of skin repair?
- A blood clot forms at the site of injury as a result of an inflammatory reaction
- Clot starts to hard and dry out of form a scab
- Granulation tissue is new connective tissue and blood vessels which forms on the surface of the injury
- Scar forms
What are the nerve endings?
Where a neutron pathway terminates and interacts with a muscle or a gland cell.
Where are nerve endings found?
Papillary level of the dermis
What are the four types of nerve endings found in skin?
Meissners corpuscles - sensitivity to light touch and are found in fingertips
Paccinian corpuscles - vibration and pressure
Pain receptors
Thermoreceptors
What are the three glands found in the skin?
Sebaceous
Apocrine sweat
Eccrine sweat
What is the function of sebaceous glands?
To produce sebum
What is the function of apocrine sweat glands? Where are they located?
To produce sweat
Axilla (armpit)
What is the function of eccrine sweat glands? Where are they located in the skin?
To produce sweat
Thermoregulator
Coiled secretory portion of the dermis.
Forms a spiral channel in the epidermis
Simple tubular gland
What are the role of myopeithelial cells in relation to sweat glands?
To squeeze the glands and push the secretion onto the surface
What is the nail?
A strong plate of keratin that grows out from the nail bed
What is the nail bed?
A specialised form of skin epithelium
What are the six structures that form the nail?
Root
Nail bed
Nail plate
Eponychium
Paronchyium
Hyponchium
What is the nail root?
Also known as the lunula
Appears as a white crescent
What is the nail bed?
Extends from the edge of the nail root to the hyponchium
What is the nail plate?
Actual fingernail, pinkish appearance due to blood vessels underneath
What is the eponychium?
Cuticle
Situated between the skin of the finger and the nail plate
What is the perionchium?
Skin that overlaps onto the sides of the nail plate
What is the hyponchium?
Area between the edge of the nail plate and the skin of the fingertip