Dermis and Subcutaneous Tissue Flashcards
Describe the structure and function of the dermis
Provides structural integrity to the skin and elasticity for response to external trauma. Varies in thickness from 1-4 mm, depending on location. Overlies and is contiguous w/ subcutaneous fact at dermal-subQ junction.
Describe the function of the subcutaneous tissue.
Metabolism and protection from physical injury
Components of the dermis
ECM: collagen and elastin (for support, strength, elasticity, and shape), glycoproteinds, and proteoglycans in ground substance. Also contains blood vessels, nerves, and adnexal structures (hair, sebacous glands, apocrine and eccrine sweat glands).
Cell types found within the dermis
dermal dendrocytes, macrophages, fibroblasts, and mast cells.
Primary collagen of the dermis
Type 1 collagen
Role and composition of collagen in skin
Provides integrity and structure and accounts for 75% of dry weight of skin (12 total types).
Mutations in collagen and enzymes for its post-translational modifications
Ehlers-Danlos Syndrome
Characteristics of Type 1 (classic) Ehlers-Danlos syndrome
hypermobility of joints, excessive stretching of skin w/ elastic recoil, fragile skin, atrophic “fish-mouth” scars.
Characteristics of Type 4 Ehlers-Danlos syndrome
involvement of blood vessels that leads to bruising and GI and arterial rupture. No tx, so minimize injury w/ no contact sports.
Structure of elastic fibers
composed of elastin and fibrillin that move readily over each other for stretch and recoil.
Pathology of Pseudoxanthoma elasticum
autosomal recessive disease resulting in clumping of elastin fibers. Onset in 1st or 2nd decade of life, symptoms in 3rd or 4th.
Clinical expression of pseudoxanthoma elasticum
Cutaneous findings of yellow papules on lateral neck and axilla. Ocular involvement may result in decreased visual acuity or blindness (rare). CV complications of claudication, HTN, angina, and MI because of elastin fibers in medium arteries.
Describe Marfan’s Syndrome
an autosomal dominant disease characterized by tall stature, disproportionately long limbs, ectopic lentis, mitral valve prolapse, aortic root dilation, aortic dissection, and possibly arachnodactyly, scoliosis, pectus excavatum, joint hypermobility.
When a wound heals, what fibers get replaced and what fibers don’t?
Collagen repaired, elastin not. Less elastin leads to scar formation.
Function of dermal blood vessels
circulate cellular and non-cellular material throughout the body, healing wounds, regulate temperature, control homeostasis, modulation of inflammation and leukocyte trafficking.
Major networks of venules, capillaries, and small arterioles (2)
- superficial plexus at junction of papillary and reticular dermis 2. deeper horizontal plexus along the dermal-subQ junction. Shunt blood b/w the two for flow regulation and tissue perfusion.
Clinical appearance of Livedo Reticularis
reticulated macular erythema of the skin, common on lower extremities, seen on trunk and upper extremities.
Pathology of Livedo Reticularis
Hypoperfusion of the skin, mostly due to cold exposure.
Clinical appearance of Leukocytoclastic vasculitis
Palpable purpura (reddish-purple, domed papules that don’t blanch w/ pressure). Common in legs and ankles. Tx: elimination of causative agent. Watch renal function (a common cause)
Pathology of Leukocytoclastic vasculities
Inflammation of the blood vessels, caused by medication, infection, and autoimmune disease.
Wounds that affect the epidermis only
erosions
Wounds that affect the epidermis and dermis
ulcers
Type of wound arising from injury to epidermis and superficial dermis only
partial thickness (less scarring)
Wounds that involve deep dermis and result in loss of adnexal structures and wounds that contract during healing
Full thickness
Three phases of wound healing
Inflammatory (clotting, vascular permeability, and influx of neutrophils and macrophages), proliferative (fibroblasts stimulate new ECM, keratinocyte migration), and maturation.(wound contraction and remodeling)
A firm scar that extends beyond the margins of the original wound, common in blacks and Mediterraneans.
Keloid
Common sites of keloids
upper trunk, neck, arms, and ears.
Treatment of keloids
intralesional steroids, compression, and scar massage to promote thinning and remodeling.
The word for a “scab” that represents neovascularization for supporting healing skin
granulation tissue
Local factors that interrupt healing:
decreased blood supply, tissue edema, infection, dry wound bed, excessive granulation tissue, chronic radiation injury
Systemic factors that interrupt healing:
advanced age, malnutrition, diabetes mellitus, CT disease, other chronic illness.
Pathology of schleroderma
hypocellular thickening of collagen
Clinical expression of localized schleroderma (Morphea)
expanding erythematous plaques that progessively become indurated. Central portion of lesion hypopigmented and surrounded by lilac-colored ring. On trunk, no systemic disease.
Clinical expression of limited systemic schleroderma
Limited: affects face and distal extremities w/ tight and thickened skin. Associated with Raynaud’s phenomenon (color change in fingers and toes in cold response) Associated with CREST syndrome
CREST syndrome
calcinosis cutis (calcium in skin), Raynaud’s phenomenon, esophageal dysmotility, scleradactyl (induration of fingers), and telangiectasis (capillaries visible through skin)
Clinical expression of diffuse systemic schleroderma
Trunk and proximal extremities. Commonly see cutaneous fibrosis, Raynaud’s syndrome, pulmonary fibrosis, renal insufficiency, and cardiac disease. Poorer prognosis than limited systemic.
Describe photoaging
Repeated, prolonged UV radiation exposure leading to skin atrophy, lentigines (large freckles), rhytides (wrinkles), dilated pores, and yellow quality to skin (degenerating elastin fibers).
Describe Poikiloderma of Civatte
telangiectasis, hyperpigmentation, hypopigmentation, and atrophy, most common in lateral neck and V of the chest
Focal bleeding into the skin
actinic purpura
Functions of the SubQ tissue
insulation, energy store, and mechanical buffer
Pathology of Panniculitis
inflammation of the subQ tissue. Histo shows inflammation of fibrous separation b/w fat lobules. Causes: medications, infection, sarcoidosis, inflammatory bowel disease, idiopathic.
Clinical expression of Panniculitis and its most common subtype and tx:
Tender, erythematous, non-ulcerated nodules w/ ill-defined borders, most often in lowe extremities. Erythema nodosum most common subtype, a delayed hypersensitivity to Ag stimulation. Tx: eliminate causative agent, rest, elevate, compression, and NSAIDS.
