INTEGUMENTARY SYSTEM Flashcards
The integumentary system is composed of the skin
skin, or cutaneous membrane,
plus its accessory structures: hairs, nails, and glands.
Through the __________of sweat, waste products (including lactic acid and urea) are released onto the skin
excretion
Numerous sensory receptors in the
skin enable sensations,such as
touch, pain, temperature, pressure, and vibration.
Blood vessels and sweat glands in the skin enable it to act in ____________ by
removing excess heat or preventing heat loss.
thermoregulation.
___________blood
vessels constrict to reduce blood flow and heat loss through the skin, or dilate to
increase heat loss.
In response to nerve signals,
Finally, the skin is the site of the initial steps in ____________which is important for the absorption of calcium from the diet.
synthesis of
vitamin D,
The skin is made up of two distinct layers:
the superficial
epidermis and the underlying dermis.
-A third
layer of tissue
- lies
deep to the dermis, and although it is not considered a component of the skin, it does help the skin perform its functions.
-consists of loose connective tissue
with many blood vessels and adipose tissue.
hypodermis.
is avascular and composed of keratinized,
stratified squamous epithelium and contains four distinct
cell types: keratinocytes, melanocytes, dendritic (Langerhans) cells, and Merkel (tactile) cells.
epidermis.
produce the strong waterproofing protein keratin.
Keratinocytes.
produce the protective pigment melanin.
melanocytes.
are specialized white blood cells that migrate to the epidermis,
where they function as phagocytes.
dendritic cells.
are located at the epidermal–dermal junction and function in
light touch reception.
Merkel (tactile) cells.
Epidermal cells are arranged in layers (strata) of cells.
Thick skin, which is located only in
the palms of the hands.
the soles of the feet, contains five strata:
the stratum basale, stratum spinosum, stratum granulosum, stratum
lucidum, and stratum corneum.
Thin skin, which is located everywhere else in the body, contains only four strata
(the stratum lucidum is absent).
-the deepest layer of the epidermis,
consists of a single layer of cuboidal epithelial cells (keratinocytes) attached to a basement membrane.
- also contains melanocytes, cells that secrete the brown pigment melanin, which
is then transferred to neighboring keratinocytes.
-The accumulation of melanin granules between the keratinocyte’s nucleus and its apical surface shields the cell’s DNA from the damaging effects of ultraviolet radiation in sunlight.
stratum basale.
-contains 8–10 layers of cells,
mostly keratinocytes that have a “spiny” appearance in histological preparations.
-dendritic cells are prominent in the stratum spinosum.
stratum spinosum.
cells do not actually have spines; instead, the spines are artifacts caused
by the shrinkage of the cells during the preparation required for viewing them on a microscope slide
Living stratum spinosum.
consists of three to five
layers of keratinocytes that undergo a drastic change in appearance as they begin to fill with keratin (a process called
keratinization)
stratum granulosum.
the cells flatten and their
organelles, including the nucleus, disintegrate; the cells eventually die.
keratinization.
found only in the thick
skin of the palms and soles, consists of two to four translucent layers of flat, dead keratinocytes.
stratum lucidum.
The most superficial epidermal stratum.
-is the thickest stratum, consisting of 20–30 layers of cells
-Its cells are essentially flattened sacs of keratin that are continually
shed from the surface of the skin and are replaced by keratinocytes arising from deeper layers.
stratum corneum.
Underlying the epidermis is the highly vascular dermis, which consists of a papillary layer and a reticular layer
the dermis.
