The Skin 1 Flashcards
What is Dermatology?
Dermatology is the study of the skin. It is a branch of internal medicine concerned with interpretation of symptoms, diagnosis, treatment of diseases of the skin.
Skin is the body’s?
Thinnest organ and largest organ.
Where is skin the thinnest and where is it the thickest?
Skin is thinnest on the eyelids (0.1 mm) and thickest on the soles of feet and palms of hands (0.6-0.8 mm). (stratum corneum)
What is skin composed of?
Skin is composed of soft keratin.
The skin is composed of three layers. What are they?
Epidermis
Dermis
Subcutaneous (Superficial Fascia)
The epidermis is much thinner than most people would guess, what areas of the skin are thicker and the exception to this?
Exceptions are areas chronically exposed to pressure or friction such as soles of feet and palms of hands.
What is the epidermis made up of?
The epidermis is made entirely of epithelial cells with no blood vessels.
What are the 5 layers of the epidermis? (from outer layer to inner layer)
Stratum Corneum, Stratum Lucidum, Stratum Granulosum, Stratum Spinosum, Stratum Germinativum
What is the stratum corneum made up of?
Stratum corneum is made up of flattened keratinized cells that have no nuclei.
How does the stratum corneum provide protection for the rest of the skin?
Its toughness and durability provide protection for the rest of the skin. Its ability to thicken in response to injury, forming callous adds to its protective function.
How long does it take a cell to move up to the stratum corneum, and how long before they are shed from the body?
It typically takes 15 to 30 days for a cell to move from the stratum germinativum to the stratum corneum, and they generally remain for an additional two weeks before they are shed or washed away.
What does exfoliation of the skin do to the stratum corneum?
Exfoliation techniques removes the superficial layers of the stratum corneum, leaving a thinner layer of protective keratinized cells, leaving the skin looking pinker, softer , and more flexible.
Is the stratum corneum waterproof?
The stratum corneum is waterproof in the sense that it keeps water out of the body.
What is insensible perspiration? How much water do you lose from insensible perspiration?
Water from interstitial fluid slowly penetrates the surface, to be evaporated into the surrounding air, this process is called insensible perspiration. You lose roughly 500ml of water through insensible perspiration.
What can happen if damage breaks connections between superficial layers and deeper layers of the epidermis?
If damage breaks connections between superficial and deeper layers of the epidermis, fluid will accumulate in pockets, or blisters within the epidermis.
Why is the second layer of the epidermis called stratum lucidum?
It was named this because its closely packed cells (a few layers of shapeless cells with flattened degenerated nuclei) contains a translucent compound (eleidin) from which keratin forms. However most skin on the body, the so-called thin skin, has no stratum lucidum.
What is accelerated in the stratum lucidum?
Keratinization is accelerated in this layer.
Why is the third layer of the epidermis called the stratum granulosum?
The third layer of the epidermis is called the stratum granulosum because granules are visible in the cytoplasm of cells.
What is the stratum granulosum?
The stratum granulosum is the outermost of the living layers of the epidermis, consisting of 3-5 layers. By the time cells reach this layer they have stopped dividing, and produce large amounts of keratin. This layer is composed of living and dead cells and the nuclei and other organelles disintegrate and cells die.
What is the function of skin crucial too?
Skin functions are crucial to survival.
What is the stratum spinosum?
The stratum spinosum is the largest layer of the epidermis and it contains alive cells with spine like projections that are joined together by connective fibres and consisting of 8-10 layers. The cells begin to mature and synthesize keratin.
What else does the stratum spinosum contain and what are they responsible for?
The stratum spinosum contains langerhans cells, which are participants in the immune response. Langerhans cells serve to fix and process cutaneous antigens.
What is the stratum germinativum?
The stratum germinativum is the basal cell layer and it contains cells that undergo mitosis. It is very thin, only one cell deep. Cells push outward from stratum germinativum into each successive layer of the epidermis, die, and become keratinized and eventually flake off, as do their predecessors.
What are Merkel cells?
Merkel cells are scattered among the cells of the stratum germinativum. They are cells that are sensitive to touch; when compressed they release chemicals that stimulate sensory nerve endings.
What are melanocytes and where are they located?
Melanocytes are located deep in the stratum germminativum, and manufacture the pigment melanin from molecules of the amino acid tyrosine. The melanin is packaged in intracellular vesicles called melanosomes, which are transferred into keratinocytes. Melanin is deposited in skin cells.
What is melanin?
Melanin is pigment that gives human skin its colour. The more melanin the deeper the brown.
What is the function of melanin?
Melanin serves a protective function. Largely baring penetration of ultraviolet rays and thereby prevents them from injuring dermis and underlying tissues.
How often does epidermis change?
The epidermis completely changes about once a month and varies based on age.
Define Keratin
Keratin is a water repellant protein. It can be soft as in skin or hard as in hair and/or nails. The protein is present in, and forming the main components of epidermal structures such as hair, nails, horns, feathers, and skin. It thickens and protects the skin and makes up hair and nails.
What is keratinization?
It is the formation of keratin or horny layers.
What is the dermis?
The dermis is the inner, thicker layer of dense, fibrous, connective tissue. The cellular components of the dermis consist of fibroblasts, mast cells, and macrophages. It is composed of two layers, the papillary layer and the reticular layer.
What does the papillary layer contain?
The papillary layer contains cone shaped projections of elastic tissue that point upward into the epidermis. These projections are papillae, which form ridges on surface of the skin. Epidermal ridges, are especially well defined on the finger tips and toes. Fingerprints and toe prints are unique for each individual.
What do papillae contain?
Looped capillaries or nerve fibre endings called tactile corpuscles.
What is the reticular layer?
The reticular layer is the innermost layer of the dermis. It is also the thickest layer. It is called the reticular layer because it consists of caliginous fibres which gives toughness to the skin.
