The Skin - Topical Drug Delivery W5 Flashcards
What is the skin
- Largest organ in the body
- Weighs 2.5kg
- Performs protective, sensory and homeostatic functions
The skin serves to ….
- Protect the internal body structures by merging with respiratory, genitourinary and digestive tracts
- Limit entry into the body of noxious chemicals, allergens etc
- Stabilise body temperature, BP
- Act as sensory organ (heat, cold, touch, pain)
When skin comes in contact with noxious agent
◦ Some may pass across the top layer (stratum corneum)
◦ Some may be metabolised in the lower layers (viable epidermis)
◦ Sensing of and reaction to chemical damage in epidermis and dermis
◦ Removal of chemical by bloodflow through vessels in the dermis
What are keratinocytes
Keratinocytes represent the major cell type of the epidermis, the outermost of the layers of the skin, making up about 90 percent of the cells there.
They originate in the deepest layer of the epidermis, the stratum basale and move up to the final barrier layer of the skin, the stratum corneum.
What is keratinocyte differentiation
critical for epidermal stratification and formation of a protective stratum corneum.
involves a series of complex processes leading through gradual changes in characteristics and functions of up to their programmed cell death via cornification.
Keratinocytes at the basal layer of the epidermis are proliferative, and as the cells mature up the epidermis, they slowly lose proliferative potential and undergo programmed destruction.
What is the epidermis
the top layer of skin in your body
What is the stratum corneum
the outermost layer of the epidermis and marks the final stage of keratinocyte maturation and development.
- keratin rich dead cell layer and metabolically inactive
What are Melanocytes
highly differentiated cells that produces a pigment melanin inside melanosomes which is taken up by keratinocytes
What is the dermis
- Middle skin layer, 1-5mm fibrous and elastictissue
- Supportive and cushioning tissue composed mainly of collagen (70%), elastin and fibrillin
- Sparse cellular population
◦ Nerve endings
◦ Blood vessels
◦ Lymph vessels
◦ Hair follicles
◦ Sweat glands
◦ Sebaceous glands
What are skin appendages
Entry points
- eccrine sweat glands
- simple, coiled, tubular glands present throughout the body, most numerously on the soles of the feet - apocrine sweat glands
- Most apocrine glands in the skin are in the armpits, the groin, and the area around the nipples of the breast and have odour - hair follicles
- nails
Sebaceous glands
Together with the hair follicle forms the pilosebaceous unit
Holocrine glands that produce a lipid-rich secretion called sebum
Overactivity, especially during puberty, causes common acne (acne vulgaris)
Subcutaneous tissue (hypodermis)
Subcutaneous fat layer acts as a:
◦ Mechanical protector
◦ Thermal insulator
◦ Energy store
Heat regulation uses subcutaneous fat pad (hypodermis) and skin blood supply
Thickness depends on whole body adiposity but need a minimal amount for skeletal and organ protection
Topical delvery
Delivery of a medicament to the skin or mucous
membrane
1. Local treatment:
◦ Skin softening (emollient)
◦ Delivery of active agent to skin tissue
2. Systemic treatment (transdermal):
◦ Delivery of drug across skin into dermal blood
vessels → systemic circulation
◦ Potent drugs including nicotine, hormones
(contraceptive and menopausal hormone
replacement)
Targets for topical delivery
Skin surface treatment
◦ Sunscreens, surface antiseptics, deodorants, protective films, drugs
Stratum corneum/appendage treatment
◦ Anti-perspirants
◦ Anti-bacterials: e.g. benzoyl peroxide, clindamycin, erythromycin for acne
◦ Anti-fungals: e.g. ketoconazole, terbinafine
applied to skin or nails
Whether for local or systemic delivery the
drug must cross the stratum corneum
Intercellular route vs intracellar
Intercellular means between cells.
Intracellular, which means within the cell
