Skin Structure and Function Flashcards
What are the two main layers of the skin called?
Dermis and Epidermis
The epidermis is the outer layer of ________1________ and the dermis is beneath the epidermis and is _________2________
1) stratified cellular epithelium
2) connective tissue
What is the origin of the epidermis?
Ectoderm
What are the 4 layers of the epidermis from superficial too deep?
1- keratin layer
2- granular layer
3- prickle cell layer
4- basal layer
The basal layer is usually ____1_______ there are lots of intermediate filaments such as ____2_____ and it is __3_____ metabolically active as _____4______
1) one cell thick with small cuboidal cells
2) keratin
3) highly
4) keratinocytes are constantly being made and moving up from the basement membrane
The prickle cell layer contains _____1_____ The cells have lots of __2___ which anchor the cells to each other and contain tufts of intermediate filaments
1) larger polyhedral cells
2) desmosomes
In the granular layer ____1_______ are synthesised then secreted by ____2______ to form a _______3_______As cells move outwards they are beginning _____4_____
1) lipid and lipid hydrolyses
2) lamellar bodies
3) water tight intercellular lipid bilayer
4) to lose their nuclei and die
What do lamellar bodies in the granular cell layer of the epidermis produce? What is its function?
Pro-filaggrin which is concerted to filaggrin in the outer layer. Filaggrin has a dual role in holding moisture within cells and as a component of tough protein cell envelope.
The keratin layer is made up of ___1____ It forms a ___2____
1) overlapping non-nucleated cell remnants.
2) a tight, waterproof barrier
95% of epidermal cells are keratinocytes but name 3 other types of cells in the epidermis
melanocytes, langerhan’s cells and merkel cells
Where do melanocytes originate from and reside in?
Originate from the neural crest and reside in the basal layer
Describe the function of melanocytes
They contain organelles called melanosomes which convert tyrosine to melanin pigment. Melanin is transferred into the surrounding keratinocytes to give protection against UV radiation.
What causes racial differences in skin colour?
Variation in melanin production not melanocyte number.
Where are langerhan’s cells found?
In the prickle cell layer as well as the dermis and lymph nodes
Describe the function of langerhan’s cells
Play a role in antigen presentation and immunoregulation
Where are merkel cells found?
In the basal layer between keratinocytes and nerve fibres
Describe the function of merkel cells
They are mechanoreceptors and play a role in sensation. They are numerous on the fingertips and in the oral cavity.
Describe the hair cycle
Anagen- growth
Catagen- involution
Telogen- shedding
At any one time most hairs will be in the anagen phase (more than 90%) which is usually 3-5yrs for scalp hair
What are the three types of hair?
Terminal (medullated coarse hair e.g. scalp, pubic).
Vellus (non-medullated fine hairs e.g. women and children faces)
Lanugo (non-medulalted fetal hair)
Nails are tough plates of hardened ___1____ which arise from the ___2____ Growth rate is about __3___ Finger nails grow __4__ than toe nails and growth rate is ___5___ in summer than winter
1) keratin
2) nail matrix (just visible as the moon-shaped lunula)
3) 0.1mm/day
4) faster
5) faster
Function of the demo-epidermal junction?
It has a key role in epithelial-mesenchymal interactions. It helps with support, anchorage, adhesion, growth and differentiation of basal cells. It is also a semi-permeable membrane acting as a barrier and filter.
3 layers of the demo-epidermal junction/
Lamina lucida, lamina densa, sub-lamina densa zone
What is the origin of the dermis?
Mesoderm
What does the dermis contain?
Fibroblasts, mast cells, lymphocytes, dermal dendritic cells, langerhans cells and macrophages. It also contains blood and lymphatic vessels, nerves, muscle and appendages e.g. glands.
Describe blood vessels in the dermis
Supply is greater than metabolic need as they also help with temperature regulation. The vessel walls are well supported and there are horizontal plexuses.
Describe lymphatic vessels in the dermis
Sub epidermal meshed networks. There is continual drainage of plasma proteins, extravasated cells and excess interstitial fluid. Important immune functions like surveillance
Describe nerves in the dermis
Somatic sensory dermatomes have free nerve endings and special receptors e.g. pacinian (pressure) and Meissners (vibration) corpuscles
Autonomic nerve supply- acts on blood vessels, nerves and glands.
3 types of skin glands?
Eccrine, apocrine and sebaceous
Describe eccrine glands
these are found on all of the skin surface, responsible for thermoregulation and sweating
Describe apocrine glands
Found in the axillae and anogenital area and do not function until puberty. Function is not fully understood.
Describe sebaceous glands
These are also inactive until puberty when they excrete an oily substance called sebum under the influence of androgens. Sebum passes onto the skin surface via the pilosebaceous duct (hair follicle). Its lipids contribute to the skin barrier and have antimicrobial actions. Sebaceous glands are found in the highest density on the face, scalp and upper torso.
How is the skin involved in metabolism and detoxification?
Involved in vit d metabolism, thyroid hormone metabolism, defence against chemicals, drugs, pollution and sunlight.
How does the skin act as a barrier?
Physical barrier, chemical secretions stop pathogens
How is the skin involved in thermoregulation?
Thermoreceptors sense changes, then get sweating, shivering and changes in blood flow
How is the skin involved in the immune defence?
Takes part in the specific and non specific reaction
How is the skin involved in communication?
Visual and odour
How is the skin involved in sense?
Touch, pressure, temperature, vibration sensors.
What cells carry out vitamin D metabolism?
Keratinocytes
What percentage of GP consultations are for skin disease
15-23
The nail lunula is…
the visible part of the nail matrix. the nail matrix sits under
Developmental growth pattern of skin follows what lines
Blaschkos lines
Define the hyponychium of nails
The hyponychium is the area of epithelium, particularly the thickened portion, underlying the free edge of the nail plate on the nail. Basically the end of the nail.
Lamellar bodies are also called …. found in ….
odland bodies found in granular cell layer
What is ground substance? Where is it found?
FOUND IN THE DERMIS
Ground substance is an amorphous gel-like substance in the extracellular space that contains all components of the extracellular matrix (ECM) except for fibrous materials such as collagen and elastin.
