Skin Flashcards
What are the functions of skin?
- protection - light, chemical, thermal, mechanical, water, infection
- sensation - touch, pressure, temperature, pain
- thermoregulation - hair, sweat, blood flow, shivering, subcutaneous adipose tissue
- metabolism - vitamin D, adipose tissue (energy storage)
- immunologic - immune cells help to deal with invasion
- sexual attractant - appearance - in animals release hormones
What type of epithelium is in the epidermis?
keratinising stratified squamous
What are the layers of the epidermis?
basal layer, stratum spinosum, stratum granulosum, stratum corneum
What are the features of the basal layer of the epidermis?
cuboidal low columnar cells on the basement membrane - this is where replication occurs
What are the features of the stratum spinosum?
diamond shaped cells with intercellular bridges
What are the features of the stratum granulosum?
purple granules in the cells - involved in the process of keratinisation
What are the features of the stratum corneum?
cells have lost their nuclei and are full of keratin
What are epidermal rete ridges?
the down pouches of the epithelium
What are the dermal papillae?
the parts of the dermis between the epidermal rete ridges
What type of cell junctions are in the stratum spinosum?
desmosomes
What are tonofibrils?
keratin intermediate filaments - in the stratum spinosum
What other types of cells are present in the epidermis?
melanocytes, langerhans cells, merkel cells
How many melanocytes are there?
1 per 8-10 epithelial cells
What is the role of melanin?
to protect the nucleus of the epithelial cells from UV exposure
What is the role of langerhans cells?
antigen recognition and antigen presenting
What do sebaceous glands look like?
foamy cytoplasm because of lipid rich secretion
What is the embryological origin of adnexal structures?
epidermis
What are the two layers of cells in sweat glands?
superficial layer is cuboidal secretory cells and deep layer is myoepithelial cells
What are the two vascular plexuses in the skin?
the papillary plexus in the superficial dermis and the cutaneous plexus between the dermis and hypodermis
What are the two layers of the dermis?
the papillary dermis superficially and the reticular dermis deep - the reticular dermis has more coarse collagen bundles
What is different about the skin on the scalp?
the hair follicles are from deeper down
What is different about the skin on the palms and soles?
the keratin layer in the epidermis is thicker and there are no hair follicles
Where does the root of a nail attach?
to the periosteum of the distal phalynx
What are the stages of healing of the skin?
in the first 24 hours there is vasoconstriction and a blood clot forms and neutrophils infiltrate. Over 3-7 days granulation tissue is formed, bringing in macrophages, fibroblasts and myofibroblasts and there is angiogenesis. Over weeks a mature scar forms and the collagen changes from type 3 to type 1
What cytokines released by macrophages contribute to the chemotaxis and proliferation of fibroblasts and keratinocytes?
PDGF, TGFbeta, IL-1, TNF, KGF-7
What cytokines released by macrophages contribute to angiogenesis?
VEG-F, FGF-2, PDGF
What cytokines released by macrophages contribute to deposition and remodelling of the ECM?
TGF beta, PDGF, TNF, OPN, IL-1, collegenase, MMPs
What are the different types of burns?
superficial (epidermis only), partial thickness (epidermis and part of dermis) and full thickness (epidermis, dermis and parts of subcutaneous tissue)
What factors affect healing of burns?
burn depth, surface area, location
What local factors affect healing in general?
– Blood supply – Infection – Foreign material – Excessive blood clot – Movement – Tissue in which the injury has occurred – Size of wound – Previous radiotherapy
What systemic factors affect healing in general?
– Nutrition: deficiency of vitamin C, certain amino acids, zinc
– Old age: deterioration in immune system
– Diabetes - increased susceptibility to infection, narrowing of blood vessels
– Imunosuppressant drugs e.g. corticosteroid therapy, chemotherapy
What are cleavage lines?
the orientation of the collagen in the dermis - if incisions are made parallel to cleavage lines then healing will be quicker
