The Skin Flashcards
(21 cards)
What are the 7 .main f citing of the skin?
Protection Immunity Thermoregulation Sensitivity Serves as a blood reservoir Excretion Endocrine
What are the five layers of the epidermis
Stratum Corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum Basale
How is the skin adapted for protection?
The stratum corneum forms a physical barrier against pathogens
The presence of keratin protects underlying structures from microbes heat and chemicals
Lipids prevent the evaporation of water from the skin, preventing dehydration, and does not allow water back In
Sebaceous glands produce an oily serum to prevent drying out of skin and assist in the elimination of surface bacteria
PH of sweat is low, this can retard the reproduction of bacteria
Melanin provides some protection from UV light
Lamellar granules (produces by keratinocytes) release a water repellent sealant
What is the function of the sebaceous glands?
The sebaceous glands produce an oily serum to prevent the drying out of the skin and to assist in the elimination of surface bacteria
How does the skin play a part in immunity?
The epidermis has langerhan cells (produced in the red bone marrow which then migrate to the epidermis)
Langerhan cells are antigen producing dendritic cells.
Dendritic cells absorb a pathogen/antigen and migrate to the lymph nodes where they stimulate T cells to begin immune reactions to pathogens, they can also mediate immune responses
Macrophages in the dermis phagocytize bacteria and viruses
Describe the structure and function of the stratum Corneum and stratum Lucidium
The stratum Corneum - 25-30 layers of dead keratinocytes. These cells are continuously shed. Lipids from the lamellar granules create a water-repellant barrier.
The stratum lucidium - only present in areas of think skin e.g. palms and soles of the feet. Consists of 3-5 layers of flattened keratinocytes containing a large amount of keratin and thicker plasma membranes
Describe the structure of the stratum granulosum and stratum spinosum
Stratum granulosum 3-5 layers of flattened keratinocytes, this is the last living layer of the epidermis lamellar granules are also present here. Keratin is produced in this layer
Stratum spinosum - consists of 8-10 layers of keratinocytes interspersed with langerhan cells and melanocytes
Describe the structure of the stratum Basale
Consists of a single row of keratinocytes. Cell division takes place here. Is the last layer of the epidermis before the dermis
Describe how the skin is adapted for thermoregulation
Pilo erectile muscle raises and lowers hair as required to trap air underneath which will warm generating a layer of heat
Sweat glands secrete sweat which is released through pores to evaporate off and cool the skin
Vasoconstriction of superficial blood vessels to divert heated blood away from the surface where it will loose heat
Vasodilation of superficial blood vessels to bring more blood closer to the surface enabling greater heat loss
Hypodermis contains a layer of adipose tissue which insulates to prevent heat loss
How is the skin adapted for sensitivity
Meissner’s corpuscles are located amongst the dermal papillae. They are principally found in glabrous (hairless) skin. They respond to touch and dynamic pressure
Hair follicle receptors are very sensitive to vibration
Free nerve endings are present throughout the epidermis. They respond to pressure and crude touch
Merkals discs respond to touch and static pressure
Pacing an corpuscles are sensitive to vibration and pressure
What are merkel’s discs sensitive to?
Touch and static pressure
What are pacinian corpuscles sensitive to?
Vibration and pressure
What are meissner’s corpuscles?
Located amongst the dermal papillae. They are found in mainly glabrous (hairless) skin. They respond to touch and dynamic pressure
How does the skin cut as a blood reservoir .
The skin contains a network of blood vessels which hold 8-10% of the total blood flow in a resting adult
How is the skin adapted for excretion and adsorption?
Approx 400ml of water evaporates through the skin every day
Salt co2 ammonia and urea are also excreted in our sweat
Absorption: lipid soluble molecules can also penetrate the skin
What are the 2layers of the dermis.
The Papillary layer
The Reticular layer
What is the structure and function of the papillary layer of the dermis?
Approx 1/5 of the total thickness of the dermis. It is made up of thin collagen and fine elastic fibers.
Much of the area is taken up by dermal papillae.
Capillary loops, meissner corpuscles and free nerve endings can be found within the dermal papillae.
What are Dermal papillae?
Dermal papillae are villi like projections of the papillary layer that dramatically increase the surface contact between the epidermis and the dermis. This greatly strengthens the skin against shearing forces.
What is the structure and function of the reticular layer?
Attached to the subcutaneous layer
Consists of dense connective tissue containing thick collagen and course elastic fibers. These fibers provide the elasticity of the skin. Between these fibers adipose cells, hair follicles, nerves, sebaceous glands and sweat glands are located
what are the three pigments responsible for Skin colour and how to they work ?
Mainly determined by melamin. Everyone has approximately the same number of melanocytes. Skin colour is dictated by how much melanin your melanocytes produce and transfer to the keratinocytes.
Carotene is a yellow orange pigment stored in the stratum Corneum and fatty areas of the dermis it is broken down in the mucosa of the small intestine into retinal (a form of vitamin A)
Haemoglobin is the final pigment responsible for skin color, oxygen content in the capillaries beneath the skin affect the appearance of the skin
Describe the structure and function of the Hypodermis / subcutaneous layer
Not strictly part of the skin
Fibers extend from the dermis to the subcutaneous layer to anchor them together
Consists of adipose tissue (fat) and the blood vessels which perfuse the skin
The Subcutaneous layer attaches to the fascia surrounding the muscles and bones.
