Dermis and Adnexal Structures (complete) Flashcards
What is the dermis?
- Structural and physiologic support network
- Provides major tensile strength of skin
- Thickness varies w/ location
Contains:
- Blood vessels
- Nerves
- Hair, glands
Describe the structure of the dermis
- Lies between epidermis and subq
Contains adnexal structures:
- Hair
- Sweat glands
- Sebaceous glands
- Vessels
- Nerves
What are the zones of the dermis?
- Papillary dermis
- Reticular dermis
Describe the papillary dermis
Upper layer of dermis
- Thin collagen bundles
- Interlocks w/ epidermal rete (increases strength and SA)
Describe the reticular dermis
Deeper layer of dermis
- Thick collagen bundles
- Visible elastic fibers
What are the three building blocks of the dermis?
Collagen: tensile strength
Elastic fibers: allow for resilience
Ground substance: facilitates diffusion
What is the most common/important collagen found in humans?
Collagen I (85% of adult dermis)
Describe the production of collagen
- Procollagen synthesized w/ fibroblasts
- Excreted extracellularly
- Cleaved enzymatically into tropocollagen
- Tropocollagen aggregates => becomes crosslinked
- Cross-links in presence of Vit C (co-factor)
What is scurvy?
- Deficiency of Vit C
- Deficiency => decreased mature collagen
- Signs/symptoms develop after 1-3 months of deprivation
An ACQUIRED disease
Key findings:
- keratoitic plugging of hairs
- perifollicular hemorrhage
- corkscrew hairs
- hemorrhagic gingivitis
What does hemorrhage occur w/ scurvy?
- Lack of collagen support for blood vessels
- Leads to rupture & hemorrhage
Bleeding gums!!! arrrr scurvyyy
What is Ehlers-Danlos Syndrome?
A CONGENITAL disease of collagen production
- family of disorders based on erroneous collagen synthesis
Mutations of collagen production cause:
- Hyperextensible skin
- Hyperextensible joints
- fragile blood vessels
- Poor wound healing
REMEMBER: It’s collagen disorder, not an elastic disorder!!!!
What are elastic fibers?
- Minor constituent of dermis => provides resiliency
- Thin fibers (1-3 microm)
- Intertwins among collagen bundles
- Special stains are required to visualize!!!
What is solar elastosis?
- Sun-damaged elastic fibers
- Happens over time — especially in Colorado
An ACQUIRED disease
Histology shows:
- basophilic (blue) material w/in superficial dermis
What is pseudoxanthoma elasticum?
A CONGENITAL disease of elastic tissue
- Caused by a mutation in MDR gene
- Premature calcified, brittle elastic fibers
Associated w/:
- Plucked chicken skin
- Systemic hypertension
- Angioid streaks in retina
- Arterial rupture
What is the ground substance?
- Pie filling of dermis
- Glued together w/ fibronectins
- Functions as a sponge
Contains:
- hyaluronic acid
- dermatan sulphate
Discuss the blood vessels of the dermis
- Provides nutritional support/diffusion to the epidermis
- Skin vessels considered as 2 plexi: superficial and deep!!
Remember: epidermis has NO VASCULATURE!
Describe generally disorders of capillary loops
- Dilated, tortuous capillaries are noted in these diseases
- these diseases have increased epidermal turnover
Ex:
- Psoriasis
- Verruca
Describe palpable purpura
- Combo of inflammation and hemorrhage
When you press on this, there is no blanching (w/ a sunburn there is — turns white when pressure is applied)
What are two important types of nerve fibers found in the skin?
Type A: heavily myelinated — conduct rapidly
Type C: unmyelinated — slow conducting
What is the clinical term for itch? What triggers itch?
Pruritus!!!
Triggers:
- dry skin
- infection (e.g. HIV)
- infestation (scabies, lice)
- metabolic disorders (renal failure)
Otherwise oftentimes you don’t know what causes itch!!!
What are two types of specialized skin receptors?
- Meissner’s Corpuscles
- Pacinian Corpuscles
Describe Meissner’s Corpuscles
- Found in fine touch!
- High density on pulps of digits
- Looks like a pine cone
Describe Pacinian Corpuscles
- Involved in pressure and vibration
- Highest density on genitals
- Look like an onion!
What are the different types of hair?
Types:
- Terminal (dark, thick, coarse)
- Vellus (peach fuzz, fine, thin)
Describe the anatomy of a hair follicle
Divided into thirds
1) Infundibulum
2) Isthmus
3) Matrical region
Describe androgenic hair loss
- AKA pattern baldness
- Characteristic loss
- Affects 50% of pop’n
- Converts testosterone to DHT => miniature follicle
What are some treatments for hair loss? How does it work?
Finasteride
- Selective inhibitor of 5-alpha-reductase
- Blocks conversion of testosterone to DHT
What are sebaceous glands?
- Lubricate thick terminal hairs
- Cause acne
Describe the pathogenesis of acne
- Disease of pilosebaceous unit
- Abnormal follicular maturation => white/black heads
- Causes overgrowth of bacteria => dermal inflammation
What are eccrine glands?
- Odorless, watery sweat secreted by these glands
- Vital for thermoreg
- On cutaneous lip, palms, soles
- Sympathetic innervation but utilizes Ach
Merocrine secretion
What are some acquired disorders of sweating?
- Heat shock
- Antiperspirants
What is miliaria?
- Blocked sweat ducts => Ruptured eccrine glands
- Manifestations depends on blockage site
What are apocrine glands?
- Outgrowths of upper bulge PEG
- Located in axillary and anogenital area
- Small/nonfunctional until puberty
- Produce stickier/gluier fluid than eccrine — SIALOMUCIN
- Odorless until contact w/ normal skin flora
What are apoeccrine glands?
- Hybrid sweat glands
- Located in axila
- Likely play role in axillary hyperhidrosis
Secrete 10x as much sweat as eccrine glands!!
How can you treat hyperhidrosis?
- Secretion is dependent upon Ach release
- SOOOO let’s block its release!!
Botulinum toxin blocks Ach release (aka botox) — expensive and painful!
