Layers of Skin and other stuff from Lecture #1 Flashcards
Which layer of skin is the first barrier against infection and foreign substances?
Epidermis
Which layer of skin retains moisture?
Epidermis
Which layer of skin nourishes and supports the epidermis?
Dermis
Which layer of skin assists with infection control?
Dermis (Houses mast cells and macrophages)
Which layer of skin assists with thermoregulation?
Both Dermis AND Epidermis
Which layer of skin houses skin appendages
Dermis
Which layer of skin provides light touch sensation?
Epidermis for light touch, but dermis also provides sensation
Which layer of skin assists with excretion (sweat)
Epidermis
Which layer of skin assists with Vitamin D production?
Epidermis
Which layer of skin contributes to cosmesis (appearance and identity)?
Epidermis
What makes up the Integumentary System?
- Skin
- Appendages
- Hair / hair follicles
- Nails*
- Glands
- -Eccrine sweat glands
- -Apocrine sweat glands
- -Sebaceous sweat glands
Skin receives how much resting cardiac output?
1/3
How much % of body weight is the skin?
15-20%
What determines the color of skin?
How active melanin production is (Melanocytes produce the protein pigment melanin).
Also influenced by Carotene (pigment) and oxygenated hemoglobin
What is the pH of our skin?
4-6.5
What is another name for the Basement Membrane Zone?
Rete Ridges - decreases overall shearing forces
Connects epidermis and dermis
Rete bridges lost in full-thickness burn victims and the elderly
What is the most plentiful of all the epidermal cells?
Keratinocytes
- Produce Keratin / “horny layer”
- Migrate from s. basale to s. corneum
What are Langerhans’ Cells
Immune cells - found in s. basale
provide antigens to T-lymphocytes
What are Merkel Cells?
Mechanoreceptors - found in s. basale
The Merkel cell is located in or near the basal layer of the epidermis and is closely associated with terminal axons.
Which layer of skin is known as the “true skin?”
Dermis - primarily connective tissues to provide structure for skin
What protein fibers make up the dermis?
Collagen, elastin, and reticular
What are the two layers of the dermis?
Papillary dermis (highly vascular) and Reticular Dermis (deepest layer, contains appendages)
What layer of skin is “dead but waterproof?”
Stratum corneum – layer of dead skin cells – contributes to thickness of skin (i.e. around the eye vs. the sole of the foot). P. 86 Sussman – “the acid mantle and stratum corneum make the skin less permeable to water & other polar compounds, and indirectly protect the skin from invasion by microorganisms.”
What is the pH of an open wound?
Open wound pH 6.5 – 8.5. As resurfacing occurs 5.9
What are the majority of epidermal cells?
Keratinocytes: majority of epidermal cells –form deepest sublayer - produce keratin – fibrous protein that is water insoluble
What layer of the epidermis is only found in thick skin?
Stratum lucidum – only in thick skin like palms and soles of feet. Stratum corneum – dead keratinocytes
What layer of skin gives you your fingerprint
Dermis - see class notes
I am “hairy and sweaty”. What layer am I?
Epidermis?
How many layers comprise the epidermis of the skin on the dorsum of your hand?
Only 4. No s.l. because it’s not thick
What are the 3 Stages of Healing
(Hemostasis)
- Inflammation
- Repair (granulation, epithelialization, contraction)
- Remodeling
What are the 5 cardinal signs of inflammation?
Pain Erhythema (redness) Calor / incr. temp Swelling Loss of function
What is hemostasis?
Retraction and sealing off of blood vessels
Achieved as a direct effect of formation of PLATELET plug
What are the cells present in the highest number shortly after wounding?
Platelets
- Activated by exposed collagen in the subendothelial CT of blood vessels
- Release a number of factors into the blood
- -Growth factors / cytokines
- -Pro-inflammatory factors (e.g. serotonin)
What is a fibrin clot?
A stable matrix of fibrinogen
Serves as structure for other cells during wound healing process
How long does the inflammation stage last?
4-6 days
What makes up the inflammation stage?
Leukocytes:
- Mast Cells
- -Histamine
- Neutrophils
- Marcophages
- Lymphocytes
Who do Neutrophils do?
NEUtrophils Predominate during the first 1-24 hours
Purpose is to fight infection
Pus is an accumulation of dead neutrophils that have phagocytized debris and bacteria
May not occur in asceptic wound
What do monocytes do?
Convert into macrophages as they enter the wound
Predominate during 24-48 hours
What to macrophages do?
Main role in inflammation is PHAGOCYTOSIS
Initially function in hypoxic environments to promote angiogenesis and transition to repair phase through cytokine secretion
When does the Proliferation / Repair stage take place?
Day 4-14 (after angiogenesis)
Granulation, Wound contraction, and epilethelialization
What is Granulation?
Granulation tissue is dependent on neovascularization / angiogenesis
Tissue is rich in fibroblasts & collagen
When does Wound Contraction start?
Around Day 4
MYOFIBROBLASTS pull the entire wound together, thereby shrinking the defect and amount of scar tissue that will form
Wound closure – skin & mm 5-8 days
Tendon – lig 3-5 weeks
What does Epithelialization do?
Creates a barrier between wound surface and environment
- Keratinocytes
- To decrease risk of infection
- To prevent loss of fluid / electrolytes
Requires oxygen and moist environment
- O2 comes from blood supply
- It is best to cover wound
- Different coverings available for “moisture balance”
Like a train, migrates adjacent to each other?
When does Remodeling / Maturation take place?
From Day 8 onward up to 1 year (or more)
Remodeling scar / collagen reorganization:
- To fit the tissue
- To fit the function
- Balance between synthesis and lysis
Keloid = mushrooms beyond margin of scar - similar but not hypertrophic
What is the difference between regeneration and repair?
Regeneration = “epithelialization or new skin formation”
Repair = “wound healing that involves granulation tissue formation, wound contraction, and epithelialization
What are some factors that determines scarring?
- Depth of initial wound
- What was the healing environment
What makes a wound chronic?
Gets stuck somewhere in the normal healing process
-Fail to follow normal healing
Typically has one of the following:
- Prolonged inflammation
- Failure to progress through the proliferative phase
- Failure to epithelialize
Which macronutrient is essential for wound healing?
PROTEIN!
What are some factors that influence healing?
Wound characteristics / Local Factors
Systemic factors
Clinician induced
Local- wound environ, size-location-type of wound, infection, vascular supply, oxygen, external forces, movement
Clinician induced + / -
MEDS: steroids, anticoagulants, immunosupression drugs all -, nutrition – need protein, vit C, zinc, iron
Systemic- age, nutrition, circulation, disease, medication, immune status VITAMIN C – critical for collagen cross-linkage & tensile strength
Moffat et al. – age, nutrition, hydration, co-morbidities, immunosuppression, stress, infection, smoking
What are some Wound / Local Factors that influence healing?
pH
-Incontinence
Local ischemia, moisture, infection, repeated trauma from inapprorpiate care (e.g. pressure, dressing changes)
What are some Systemic Factors that influence healing?
Medications, age, comorbidities, bloodflow (perfusion and oxygenation - smokers), infection, nutrition, stress
What are some clinician induced factors that influence healing?
Poor management of medications, topical agents, dressing changes
How is the Epidermis nourished?
By diffusion from the dermis!
The epidermis contains no blood vessels
How long does it take for Keratin to travel from the deepest layer (s. basale) to s. corneum?
28 days
Most common stage chronic wound is stuck in?
- Proliferation / Repair
