Flashcards in Skin Deck (57)
What are the four layers of the epidermis?
What is the main function of the epidermis?
Replace damaged cells - to maintain skin's protective properties
Which two cells are contained in the stratum basale layer?
How does the skin replace damaged cells?
Continual production of keratinocytes - these are pushed up through the four layers of the epidermis until they are shed
What is the role of melanocytes?
Production of melanin which acts to protect the skin from UV by absorbing it. Melanin is produced on exposure to sunlight
What is the role of the stratum spinosum?
Anchors cells together by interlocking cytoplasmic processes
What takes place in the stratum granulosum?
Cells undergo enzyme-induced destruction - losing their nuclei and cytoplasmic organelles.
Lipid-rich secretions acting as the skins water sealant
Keratin is laid down, further meshing structures together
What does the stratum corneum consist of?
Dead cells which are flattened and contain densely packed keratin
Corneocytes are shed from the skin
What is the function of the dermis?
Provides strength (contains fibroblasts and collagen) but also provides elasticity (contains elastin)
Name some specialised structure that are present within the dermis
What is the function of the hypodermis?
Cushions and insulates tissue below the hypodermis
Which layer of the skin contains fat?
What are the three layers of the skin from top to bottom?
What are the four main functions of the skin?
Production of Vitamin D
Sensory organ for touch, pain and temperature
Controls body temperature
Barrier to protect tissues and organs
Describe the function of the skin in producing vitamin D
7-dehydrocholestrol in the skin produces vitamin D3 (cholecalciferol) in the presence of sunlight/UV
Vit D3 is then converted into calcidiol in the liver
calcidiol -> calcitriol in the kidney
calcitriol is the active form of vitamin D
How does vitamin D increase calcium levels?
It stimulates intestinal epithelium to produce more carrier protein molecules for calcium transport
Name three sensory receptors in the skin and outline their role
Mechanoreceptors - light touch and deep pressure detection
Thermoreceptors - warmth and cold detection
Nociceptors - respond to pain
Describe the role of the skin in controlling body temperature
In hot weather - capillaries open, increasing blood flow = vasodilaton -> heat loss at surface of skin
In cold weather - vasoconstriction -> minimising heat loss
Sweat glands actively secrete water and salts when body temperature is above 37 to cool body down
The skin acts as a protective barrier for tissues and organs. Name four things it protects against
Mechanical damage and trauma
Which cells in the skin are involved in the immune response against foreign matter and where are they found?
Langerhans cells found in the epidermis. They are antigen-presenting and so ingest the foreign particles and present them to T and B cells to induce immune response
What are the four phases in the healing process of the skin?
What events take place if the epidermis of the skin is broken as a result of a burn/graze?
Keratinocytes in the stratum basale break from the basement membrane.
They enlarge and move across the wound until they meet another cell = contact inhibition, where growth and stops
What happens in the haemostasis stage of skin healing, following injury to the epidermis and dermis?
Main priority is to stop bleeding
Platelets recognise exposed collagen in the exposed dermis. They become sticky and release thromboxane A2. Platelets are now activated and begin to aggregate, forming a temp. plug.
Seratonin is released from activated platelets and works to reduce blood supply around the wound.
Both the plug and vasoconstriction reduce blood loss from the injury.
Thromboplastin, released from damaged tissues combines with calcium to form insoluble fibrin at the end of the clotting cascade
The fibrin combines with platelet aggregates to form a clot, and if this is left uncovered -> dries -> scab
What takes place in the inflammatory phase of skin healing?
The main aim is to clean the wound
Langerhans cells are activated and release inflammatory mediators
Bradykinin increases pain at the site
Leukotrienes increase blood flow causing the skin to warm
There is an increase in vascular permeability, allowing WBCs to move to the wound from the blood
WBCs produce neutrophils which digest bacteria
Monocytes then move to the wound, maturing into macrophages which continue the wound cleaning process throughout healing
What takes place in the proliferative stage of skin healing?
Main aim is dermis repair and epidermis regeneration
Macrophages commence this stage
If the wound has low oxygen levels, macrophages release angiogenic growth factors to develop new blood vessels
Macrophages release chemicals to attract granulation tissue to the wound -> new connective tissue
Platelet derived growth factors and macrophages activate fibroblasts which grow and divide to produce a collagen network to strengthen the wound
Epithelial cells move over the top of the moist granulation tissue. Once the cells meet at the top of the wound, they stop due to contact inhibition
What takes place in the maturation stage?
The phase forms a scar. This can take up to 2 years
Collagen is re-aligned to improve strength. Collagen strands pull the wound inwards
Extra blood vessels close
Which intrinsic patient factors affect the wound healing process?
Nutrition - vitamins and proteins needed
Skin perfusion - disease such as peripheral vascular disease can affect this and so reduce O2 levels
Age - younger patients better perfusion
Which extrinsic factors affect the wound healing process?
Moist wound - better
Wound temp - 37 degrees optimal
Clean wound surface
Where are sebaceous glands found?