Flashcards in Introduction to Skin Deck (63)
What are the three main layers of skin?
Epidermis, dermis and hypodermis (fat layer)
What is keratin?
Keratin is an intermediate filament that is most abundant in the stratum corneum (top layer), hair and nails.
Where is keratin most abundant in the skin?
Epidermis, stratum corneum (top layer), hair and nails too
What are the two types of keratin?
Soft (alpha) and hard (beta) - determined by the secondary structure and suffice bridges
What are the four main layers of the epidermis?
Stratum corneum, stratum granulosum, stratum spinosum and stratum basale
Describe the stratum corneum layer of the epidermis
Protective layer of the skin with dead cells and intercellular lipids (ceramics) to maintain skin moisture
Describe the stratum granulosum layer of the epidermis
This is 2-3 cells thick and has large granules of keratohyalin
Describe the stratum spinosum layer of the epidermis
3-4 cells thick with many desmosomes to separate the keratinocytes which gives the layer a spiny appearance
Describe the stratum basale layer of the epidermis
Proliferation of epithelial cells occurs here and cells are slightly denser
Describe the composition of the basement membrane of the epidermis of the sin
ECM consists of laminin 332, collagen IV and collagen VII
What is the role of the basement membrane in the epidermis?
To provide cell polarity, regulate basal function and to anchor the epidermis to the dermis
What is the function of the hemidesmosomes in the basement membrane of the epidermis?
Bind the keratin cytoskeleton to the basement membrane
What is the role of the dermis?
Provides strength and elasticity to the skin
What is the most abundant cell in the dermis?
What is the function of fibroblasts in the dermis?
Produce elastin, collagen and proteoglycans
What is the neuromuscular supply to the dermis like?
Innervated and vascularised
What are the three layers of the dermis?
Papillary, reticular and adipose
Describe the papillary layer of the dermis
Contains fine, randomly organised type III collagen and elastin, and lies directly below the basement membrane of the epidermis
What type of collagen is present in the dermis?
Type III collagen
Describe the reticular layer of the dermis
The thickest layer densely packed with collagen providing mechanical strength
Which dermal layer is largely responsible for the mechanical strength of the skin, and why?
Reticular layer of the dermis as it is densely packed with collagen
What are adherens junctions?
These are more basal than tight joints and involve a cadherin receptor linked to an actin cytoskeleton
What are desmosomes?
Provide a connection between intermediate filaments of the cell cytoskeletons of adjacent cells; cadherin receptor is linked to the keratin cytoskeleton
What are tight junctions?
These seal adjacent epithelial cells in a narrow band just beneath their apical surface. Claudin and occluding molecules seal the intercellular space
What are gap junctions?
These form intercellular pores made up of connexins
Name four different types of cell-cell adhesions
Adherens, desmosome, tight junctions and gap junctions
Name three types of glands that may be present in the skin
Sebaceous, eccrine sweat gland, apocrine gland
What is a sebaceous gland?
Exocrine gland (secreted into duct) usually found attached to a hair follicle which produces sebum to lubricate skin
What is acne caused by?
Infection of the sebaceous glands