Lecture 1 Flashcards
Anatomy of the skin - I
The skin is the…?
Largest and most visible organ of the body covering around 1.5-2m^2 and weighing around 16% of our total body mass
Evolution provided us with…?
Sweat glands as a cooling mechanism
What are the accessory structures?
Hair follicles, sweat glands, nail beds, sebaceous glands and receptors
What is the integumentary system?
The skin and accessory structues
What are the functions of the integumentary system?
Protection, excretion, temperature regulation, melanin production, keratin production, synthesis of vitamin D3 to calcitriol, lipid storage, receptor detection
What is a composite tissue?
A structure made up from more than one basic tissue type
What basic tissue types is the skin made up of?
Epithelial, connective, muscle and nervous
What are the three primary layers of the skin?
Epidermis, dermis and hypodermis
What is the epidermis?
An avascular stratified barrier of mostly keratinocytes
What is the dermis?
A vascular structure deep to the epidermis made from protein fibres (collagen and elastin) for strength
What is the hypodermis?
A vascular structure deep to the dermis made from mostly adipose tissue which stores fat to be mobilised during a time of fasting or extended starvation for energy
What is the cutaneous layer?
Epidermis and dermis
What is the subcutaneous layer?
Hypodermis
What is simple epithelia?
One layer of epithelial cells arranged as either squamous, cuboidal or columnar
What is stratified epithelia?
Many layers of epithelial cells arranged as either squamous, cuboidal or columnar
The epidermis is made primarily of…?
Stratified squamous epithelium
What are the four layers of the epidermis?
Stratum corneum, stratum granulosum, stratum spinosum, stratum basale
What is the stratum corneum?
Most superficial layer of the epidermis. Composed of dead, dried out hard cells without nuclei
What is the stratum granulosum?
Second layer of the epidermis which contains granules that promote dehydration of the cell, crosslinking of keratin fibre. A waxy material is secreted into the intercellular spaces
What is the stratum spinosum?
Third layer of the epidermis with intercellular bridges called desmosomes that link the cells together. The cells become increasingly flattened as they move upward. Contains immune cells
What is the stratum basale?
Deepest layer of the epidermis with columnar regenerative cells. As the basal cell divides, a daughter cell migrates upwards to replenish the layer above
What is a desmosome?
A structure which anchors adjacent cells together in the epidermis
What is a hemidesmosome?
A structure which anchors the stratum basale of the epidermis to the dermis
What is thick skin?
Skin with an extra layer of epidermis called the stratum lucidum found on the palms of our hands and soles of our feet. A seemingly translucent layer that functions to reduce friction between stratum corneum and stratum granulosum in these highly used areas.
What is an epidermal ridge?
Projections downwards of the epidermis
What is a dermal papilla?
Projection upwards of the dermis
What do the epidermal ridges and dermal papilla do?
Increase surface area and bind the dermis to the epidermis
What are the two layers of the dermis?
Papillary layer and reticular layer. Both contain blood vessels, lymphatics, sensory nerve fibres and accessory structures
What is the papillary layer of the dermis?
Consists of highly vascularised tissues for nourishment, most superficial layer
What is the reticular layer of the dermis?
A ‘mesh-like’ structure of collagen and elastin fibres for strength, deepest layer
What is a plexus?
A network of either blood vessels or nerves
What are the two plexuses of the dermis?
Cutaneous plexus and subpapillary plexus
What is the cutaneous plexus?
A network of blood vessels superficial to the subcutaneous layer (hypodermis) , at junction of the dermis to the hypodermis. It supplies the hypoermis, deeper dermis, including the capillaries for hair follicles and sweat glands.
What is the subpapillary plexus?
Network of branches of blood vessels from the cutaneous plexus. Lies deep to the papillary layer of the dermis and provides O2 and nutrients to the upper dermis and epidermis
What is the hypodermis (subcutaneous layer)?
Deepest layer of the skin which is dominated by adipocytes that produce subcutaneous fat for energy and insulation. Is a common site of injections using hypodermic needles.
What is a first degree burn?
Superficial (only outer layers of the epidermis), erythema, skin remains a water and bacterial barrier, usually heals within 3-10 days e.g. mild sun burn
What is a normal second degree burn?
Epidermis + varying amounts of dermis, painful, red and blistered. Usually heals within 1-2 weeks with good dressings
What is a deeper second degree burn?
Epidermis + varying amounts of dermis, can present whitish with waxy looking areas. Hair follicles and sweat glands may stay intact and some sensation may be lost. Usually heals within a month
What is a third degree burn?
Full thickness burn extended into the subcutaneous tissue which may involve muscle and bone. Varied colour including waxy white, deep red or black. Skin appears hard, dry and leathery. No pain as sensory nerve endings have been destroyed. May require skin grafting and can take weeks to months to heal/regenerate. Scarring occurs
