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PBL 1 Glasgow 2012


What are the three structural layers of the skin? Epidermis(top), Dermis, Subcutaneous tissue
What are the four layers of the epidermis in THIN skin? From lower layers upwards to surface? Stratum Basale (Basal Layer), Stratum Spinosum(spinious or prickle cell layer), Stratum granulosum, Stratum Corneum (horny Layer)
What is the extra layer of the epidermis called that occurs in thick skin? stratum lucideum
What cells are present in the Stratum Basale? Majority = keratinocytes 1 in 10 = melanocytes Merkel Cells = in thicker areas ie palms and soles Stem cells= responsible of regeneration of keratinocytes
How are the cells in the Stratum basale bound to the membrane anchored to the basement membrane by hesmidesmososmes
What are desmosomes? what layer of the epiderimis are they found? and how do they form? Found in the stratum spinosum. Forms fribrillar prtoein cytokeratin, which accumulates to form tonofribils, which then forms bundles which become desmosomes. structure that forms site of adhesion between two cells.
What cell types are found in the stratum spinosum? Mainy sided keratinocytes Langerhan cells melanocytes
Stratum Basale? deepest layer, composed of a single row of cuboidal or columnar keratinocytes that contain scattered tonofilaments (intermediate filaments); stem cells undergo cell division to produce new keratinocytes;melaoncytes, langerhan cells and merkel cells.
Stratum spinosum? eight to ten rows of many-sided keratinocytes with bundles of tonofilaments; includes projections of melanocytes and langerhan cells
Stratum granulosum? 3 to 5 rows of flattened keratinocytes, in which organelles are beginning to degenerate; cells contain the protein keratohyalin, which converts tonofilaments into keratin, and lamellar granules, which releases a lipid rich, water-repellant secretion.
Stratum lucideum? present only in fingertips, palms and soles; consists of three to five rows of clear flat, dead keratinocytes with large amounts of keratin
Stratum Corneum? twenty-five to 30 rows of dead, flat keratinocytes that contain mostly keratin. Also, has sheets of overlapping corneocytes
Describe the process of keratinization? Newly formed cells in the stratum basale are slowly pushed to the surface. As the cells mover from one epidermal layer to the next, they accumulate more keratin, a process called keratinization.
when does the rate of cell division in the stratum basale increase? when the outer layers of the epidermis are stripped away, as occurs in abrasions and burns
Describe the process of maturation? The four separate layers represent the stages of maturation of keratin of keratinocytes. The epidermis undergoes continual renewal; cells are constantly being shed from the surface and replaced by those moving upwards from below
Dermo-epidermal junction / basement membrane Complex region holding epidermis to dermis.
What are the two regions of a dermo/ epidermal junction called? Lamina lucidia and lamina densa
What cells does the epidermo/dermo junction consist of? keratinocytes and fibroblasts
What are melaoncytes? Melanocytes are responisble fro manufacturing melanin, the pigment that gives skin it's colour. Melanin pigment provides protection against UV radiation; chronic exposure to light increases the ratio of melanocytes to keratinocytes
Is there a difference in the number of melanocytes in racial groups? No, but in dark skin larger and more processes.
What are langerhan cells? are immunolgocally active, dendritic cells derived from the bone marrow. Make up 2-4% of the epidermal population.
What is the function of langerhan cells? play a significant role in immune reactions of the skin acting as anti-gen presenting cells. Numbers not affected by UV but increases in allergic reactions.
What are the two layers of the Dermis called? papillary dermis and reticular dermis
papillary dermis? top 1/5th the thin upper layer of the dermis. Composed of loosely interwoven collagen, areolar connective tissue, elastic fibres, dermal papillae that houses capillaries, corpuscles of touch and free nerve endings
Reticular dermis? bottom 4/5th contains dense, coarser and horizontally running bundles of collagen and elastic fibres. Spaces between fibres contain some adipose cells, hair follices, nerves, and sebaceous glands.
Subcutaneous tissue? mainly adipose tissue and fat which is responsible for - energy reservoir -padding -site of disease inflammation
What are skin appendages? Specialised structures such as: -hair folicles -sweat glands -sebaceous glands; and -nails
How do the skin appendages arise? arise as downgrowths into the dermis from the epidermis during embryological development. Occupy mainly the dermis and occasionally the upper subcutis
Sebaceous glands? OIL glands. They are connected to hair folicles. Absent in palms and soles. Secrete an oily substance called sebum. Coats the surface of the hair to prevent them becoming brittle.
What are the two types of sudoriferous glands? eccrine and apocrine glands
Eccrine glands? throughout skin of most egions of the body especially in skin of forehead, palms and soles. Mostly in deep dermis. Secretions are less viscous: consists of water, ions, urea, ureic acid, ammonia, amino acids, glucose and latic acid.
What is the function of eccrine glands? regulation of body temperature and waste removal. Onset of function soon after birth
Apocrine glands? skin of the axilla, groin, areolae, bearded regions of the face, clitoris, and labiae minora. Mostly in subcutaneous layer. Secretions are more viscous consists of the same components as eccrine glands plus lipids and proteins
What is the functions of apocrine glands? Stimulated during emotional stress and sexual excitement. Onset of function at puberty
What are the three main functions of the skin? Protection, regulation, sensation
What is the protectory role of the skin? primary function barrier against: Mechanical impacts, pressure, variations in temperature, micro-organisms, radiation/ chemicals
what is the physiological regulatory role of skin? regulation of: body temperature, changes in peripheral circulation, fluid balance via sweat and synthesis of vitamin D
What is the sensatory role of the skin? network of nerve cells that detect and relay changes in the environment.
what is a wound? The breakdown in the protective function of the skin, the loss of continuity of epithelium following injury to the skin or caused by sugery, a blow, a cut, or as a result of disease.
By what two processes do wounds heal? primary intention or secondayr intention
Primary Intention When healing can start immediately, because there is no gap to close and no infection to overcome
Secondary intention If the margins are separated, and/or infected, and/or bruised, the wound must correct these three actions before it can close.
In relation to the depth of injury what does the following terminology mean? EROSION ULCERATION PARTIAL THICKNESS FULL THICKNESS EROSION: only epidermis is lost ULCERATION: structures deep to epidermis PARTIAL THICKNESS: epidermis+ varying parts of dermis. FULL THICKNESS: epidermis+ all of dermis+ depper structures
what are the advantages of primary intention? process is fairly rapid; 7-10 days. Minimal amount of scar tissue formed as surface area if wound is reduced due to "closing" the wound. less oppertunity for colonisation or infection to enter the wound from outside sources
What are the disadvantages of primary intention? as the wound edges are closed, possibility that foreign material or bacteria may be enclosed within the wound. IMPORTANT TO REMOVE FOREGIN MATERIAL BEFORE CLOSURE.
Healing involves three phases which overlap. Name the three phases? Inflammation, Tissue profliferation and Tissue remodelling
Describe the inflammation stage of wound healing. Platelets are the first cell to appear after wounding. They initiate haemostasis/blood clot but also the healing cascade by releasing growth factors. This then attracts other cells to the wound to fight infection i.e WBCs.
During inflammation why is there redness/swelling? All the new cells migrating to the area (WBCS, neutrophils,monocytes,macrophages)
What is the role of growth factors in wound healing? GFs produced by neutrophils and macrophages allow different stages of wound healing to be initiated by communication.
Give examples of growth factors released in wound healing. Platelet derived GF Fibroblast GF Angiogenesis GF Epidermal GF Transforming GF Vascular Endothelial GF
Describe STEP 2 of wound healing, The proliferation phase. what are the two processes involved? Initial responses to injury provide a framework for the production of a new barrier by : re-epithelialsiation neo-vascularisation
How long does re-epithlialisation take from time of injury? within 1-2 days pf wounding, keratinocytes move from the skin appendages and near the edge of the wound
How do the keratinocytes adapt during re-epithelisation loose cell-cell adhesion properties, become flatter
How does re-epithelisation of the wound surface occur? -Classic "leap" frog model: cells move2-3 cell length from their orginial position and roll over other cells previously implanted in the wound. They then fix and other cells leap frog over them - "train method" cell migrate in order
What happens at the end of re-epithelisation? once the wound is covered in a single layer of keratinocytes all the keratinocytes start to proliferate
What happens that is similar to re-epithelialisation during the neo-vascularisation stage? chemotactic factors promote endothelial cell to migrate and proliferate.
what mupltiplies during neo-vascularisation? fibroblasts multiply and fibroblasts begin to produce collagen.
Why is the multiplication of Fibroblasts inportant in neo-vascularisation? collagen strands are depositited in a haphazardous way and form a fibrous network that supports the new capillary loops. The tissue formed is called granulation tissue.
What physical properties happen during neo-vascularisation? Signs of inflammation disappear and fibroblasts contract pulling the wound edges together.
Why is wound contraction important during neo-vascularisation? less granulation tissue is required to fill the would cavity.
Tissue remodelling? collagen is orgaised into thick bundles and extensively cross-linked to form the mature scar.
What is an incised wound? clean surface cut from sharp-edged object/ Blood vessels cut clean across, may bleed alot. May be tendon or nerve damage.
What is a laceration? caused by crushing or ripping. May bleed less than incised but more tissue damage likely. can be contaminated with germs and therefore increased risk of infection.
What is an abrasion? topmost layer of skin removed. Raw but superficial. Slide fall or friction burn can contain embedded particles, therfore increased risk of infection
What is a contusion? Blunt blow. Ruptured capillaries beneath skin and blood leaks into surrounding tissues. Skin may split. Serious contusions may show deeper damage i.e fracture or internal bleeding
what is a puncture wound? caused by entry of object that breaks skin/bones into skin. Small entry side but deep internal damage. Increased infection risk due to passage of germs deep into wound
What is a stab wound? caused by long/bladed object e.g knife. Stab injury to trunk should be treated as very serious because of risk to vital organs
What is a gunshot wound? Sucks in clothing and contaminants rom the air. entry wound may be small and neat, whilst exit wound may be large and ragged.
What factors affect wound healing? size of wound, blood supply to the area, presence of foreign anti-bodies, age and health, nutritional status, drugs i.e steriods inhibit the growth of new blood vessels, variety of systematic diseases i.e diabetes, oxygen suppply
Created by: Taryn Miller