Layers of Skin
What is the primary function of the skin?
protect the body from the environment by serving as a barrier against microorganisms, ultraviolet radiation, loss of body fluids, and the stress of mechanical forces.
What are the dermal appendages?
nails, hair, sebaceous glands, and eccrine and apocrine sweat glands.
What causes pressure injuries?
localized damage to the skin that results from unrelieved pressure, shearing forces, friction and moisture.
FUN FACT: Usually developed over bony prominences, such as sacrum, heels, ischia, and greater trochanters.
Continuous pressure on tissue between the bony prominence and a resistant outside surface distorts capillaries and occludes the blood flow and oxygen supply.
What is a pustule?
Elevated, superficial lesion; similar to a vesicle but filled with purulent fluid
examples: impetigo, acne
What is a vesicle?
Elevated, circumscribed, superficial, does not extend into dermis; filled with serous fluid; less than 1cm in diamter
examples: varicella (chicken pox), herpes zoster (shingles), herpes simplex
What are the three major layers of the skin?
1) superficial or outer layer of epidermis
2) a deeper layer of dermis
3) the subcutaneous layer (hypodermis)
What are the six structural units of the nails?
What is a decubitus injury?
a pressure injury that results when an individual lies or sits in one position for a long time.
Mucosal membrane pressure injury is related to injury caused from use of medical devices, such as endotracheal tubes.
Vesicle greater than 1 cm in diamter
examples: blister, pemphigus vulgaris
What is telangiectasia?
Fine (0.5-1.0mm), irregular red lines produced by capillary dilation; can be associated with acne rosacea (face), venous hypertension (spider veins in legs), systemic sclerosis, or developmental abnormalities (port wine birthmarks).
What makes up the epidermis?
It renews itself by shedding the superficial layer of stratum corneum.
It is formed primarily of keratinocytes which produce keratin: a scleroprotein that provides protection from mechanical stress. Keratin is the main constituent of skin, hair, and nails.
Made up of three layers :
1) basal layer (stratum basale)
2) spinous layer (stratum spinosum)
3) germinative layer (stratum germinativum)
Cells of the dermis
Where do hair follicles arise from?
The matrix (or bulb) located deep in the dermis.
FUN FACT: They extend from the dermis at an angle and have an arrector pili muscle attached near the mid-dermis that straightens the follicle when contracted, causing hair to stand up.
What happens if pressure is unrelieved on skin?
The endothelial cells lining the capillaries become disrupted with platelet aggregation, forming microthrombi that block blood flow and cause anoxic necrosis of surrounding tissue.
What is vitiligo and what does it look like?
it's thought to be an autoimmune-related loss of melanocytes resulting in the depigmentation of patches of skin.
It is a flat, nonpalpable, irregular-shaped macule more than 1cm in diameter.
What is a wheal?
Elevated, irregular shaped area of cutaneous edema; solid, transient; variable diameter
examples: insect bites, urticaria, allergic reaction
What types of cells facilitate the epidermis?
Melanocytes: located near the base of the epidermis. They synthesize and secrete the pigment melanin with exposure to UV light in response to melanocyte-stimulating hormone. Also, determines skin color.
Langerhans cells: migrate to the epidermis from bone marrow. Initiate an immune response by presenting processed angitgen to T cells, thus providing a defense against environmental antigens.
Merkel Cells: associated with touch receptors and function as slowly adapting mechanoreceptors when stimulated by deformation of the epidermis.
What do sebaceous glands secrete?
They secrete sebum, composed primarily of lipids, that oils the skin and hair and prevents drying.
The growth of sebaceous glands is stimulated by androgens, and their enlargement is one of the early signs of puberty.
How many stages of pressure injuries are there?
4
see figure 47.3 for more information
What is a macule?
A flat, circumscribed area that is a change in color of the skin; less than 1cm in diamter
examples: freckles, flat moles (nevi), petechiae, measles, scarlet fever
What are keloids?
rounded, firm, elevated scars with irregular clawlike margins that extend beyond the original site of injury.
Most common in darkly pigmented skin types and generally appear weeks to months after a stable scar has formed.
They have excessive deposition of fibroblasts-derived extracellular matrix proteins, particularly types I and III collagen with persistent mitotic rates.
What makes up the dermis?
Composed of three types of connective tissue:
1)collagen
2) elastin and reticulin
3) gel like ground substance
It allows the skin to be mobile and to stretch and contract with body movement.
Hair follicles, sebaceous glands, sweat glands, blood vessels, lymphatic vessels, and nerves are contained in the dermis.
Why are errcrine glands important?
They are distributed over the body, with the greatest numbers in the palms of the hands, soles of the feet, and forehead.
These secretions are important in thermoregulation and cooling of the body through evaporation.
Who is at a greater risk for pressure injuries?
Individuals with darkly pigmented skin are at greater risk for developing pressure injuries because early signs of skin damage may not be clearly visible.
Itching, common symptom associated with many primary skin disorders, such as eczema, psoriasis, or lice infestations, or it can be a manifestation of systemic disease.
Peripheral pruritogenic mediators include histamine, neuropeptides, serotonin, prostaglandins, bradykinin, substance P, opioids, acetylcholine, interleukins 2 and 31, proteinases, and nerve growth factor.
What is a papule?
An elevated, firm, circumscribed area less than 1cm in diamter
examples: wart, elevated moles, lichen planus, fibroma, insect bite