Derm Structures Flashcards
- Identify the structural components of the dermis.
Has everything to keep the skin alive ( hair follicles, sweat glands, vessels, nerves, etc)
Papillary layer interlocks with epidermal base to provide shear strength and increase area available for diffusion.
The reticular layer contains everything else.
Collagen: provides most of the tensile strength in the skin (doesn’t come from the epidermis)
Collagen is secreted as procollagen by fibroblasts and assembled into collagen extracellularly– requires vitamin C as cofactor; stains eosinophilic.
No Vit C = Scurvy: easy bruising, abnormal hair structure, bleeding gums, delayed wound healing. Easy bleeding due to lack of collagen sheath around blood vessel.
Fibroblasts make collagen, ground sub, elastic fibers
Ground substance: between collagen, allows for diffusion in dermis.
Elastic fibers: allow resiliency (elasticity), much thinner than collagen fibers.
Distinguish between the types of collagen relevant to the skin
Collagen I: 85% of adult dermis; also a major component of bone.
Collagen III: large part of the fetal dermis (hence babies don’t scar)
Collagen IV: found in basement membrane zone. Prominent around some vessels in the dermis.
Collagen VII: anchoring fibrils between dermis and epidermis.
Understand the function of elastic fibers in the skin
Collagen fibers provide the skin with tensile strength, but elastic fibers provide the skin with resiliency - SNAP BACK
Be familiar with the ground substance components of the dermis
Protein-sugar moieties, ie GAGs, like hyaluronic acid and derma tan sulphate
Absorb a tremendous amount of water
“pie filling.”
helps to facilitate nourishment by making a water-based environment for diffusion
Identify disorders associated with defects in collagen and elastin
Ehlers-Danlos Syndrome: A defect of COLLAGEN, not elastin
- Hyperextensible skin and joints.
- “Molluscoid psuedotumors” (soft, spongy tumors, made of fat and collagen) in easily damaged locations.
- Often don’t have a lingual frenula
Solar elastosis: ACQUIRED disorder of elastic fibers.
- ELASTIC FIBERS are damaged due to UV exposure, making them basophilic (blue-staining)
Psuedoxanthoma elastica (PXE):
- GENETIC elastin disease, defect in MDR gene
- Elastin becomes calcified and brittle.
- Arterial rupture in the retina, blindness.
- Chicken skin appearance
Know the vascular supply of the skin as well as associated disorders.
BV of the dermis is divided into superficial and deep plexi; terminate in the papillary dermis
Important for wound healing, thermoregulation (Sucquet-Hoyer canal), and leukocyte trafficking
Dilated, torturous dermal capillaries are noted in diseases with increased epidermal turnover: Psoriasis, Verruca (warts)
Note removal of scales in psoriasis causes pinpoint bleeding– this still doesn’t mean there are blood vessels in the epidermis, just that you’ve ripped open the capillaries right under the epidermis.
Can get vasculitis in the dermis from immune complex deposition in the dermal vasculature (standard type III immunopathology, here called “Gell and Coombs” reaction pattern).
Tends to manifest, on this scale, as PALPABLE PURPURA and nonblanching petechiae.
Innervation of the skin
Nerves: can end in a variety of ways in the dermis:
- Pacinian corpuscles: sensitive to pressure & vibes (Pacinian = Pressure), look like ONION
- Meissner’s corpuscles: sensitive to light touch (finger pads of hands), look like… pine cone?
- Free nerve endings in dermis: itch, pain, temperature, etc.
Types of neurons in the skin:
A: heavily myelinated, conduct quickly
C: unmyelinated, conduct slowly
Important because various anesthetics block different types of neurons. Local anesthetics block conduction of type A (pain) fibers.
Identify the major adnexal structures of the skin
Hair follicles:
- “Terminal hair” (dark thick, coarse)
- “Vellus hair” (fine, thin, apigmented)
Three regions of hair:
- Top third = infundibulum;
- Middle third = isthmus;
- Bottom third = matrical area.
Sebaceous glands: next to hair follicles; lubricate the hair and prevent splitting.
Eccrine glands = sweat glands (watery, odorless). Used primarily for thermoregulation. Numerous on forehead, palms/soles, axilla, cutaneous lips, etc.
Sweat glands are stimulated by acetylcholine, but are sympathetic glands.
Apocrine glands = secrete a different kind of sweat (give off body odor when acted upon by bacteria). Called apocrine due to their method of secretion: membrane ‘blebs’ off in apical direction.
Apoeccrine glands = hybrid, produce both eccrine sweat (watery, odorless) and apocrine sweat (odiferous); located mainly in the axilla and can produce an enormous volume of sweat.
“Hyperhidrosis”: excess production of sweat. Note can use botox (botulinum toxin) to prevent acetylcholine release to treat this condition.
