The epidermis is composed of
keratinized stratified squamous
four principal types of cells
melanocytes, Langerhans cells, and Merkel cells
90% of epidermal cells are
tough, fibrous protein that helps protect the skin and underlying
tissues from heat, microbes, and chemicals
What produce lamellar granules, which release a water-repellent
sealant that decreases water entry and loss and inhibits the entry
of foreign materials.
About 8% of the epidermal cells are
a yellow-red or brown-black pigment that contributes to skin
color and absorbs damaging ultraviolet (UV) light
Type of cell that arise from red bone marrow
and migrate to the epidermis, where they constitute
a small fraction of the epidermal cells
Type of cell that participates in
immune responses mounted against microbes that invade the
skin, and are easily damaged by UV light
Langerhans role in the immune
help other cells of the immune system recognize
an invading microbe and destroy it.
least numerous of the epidermal cells?
are located in the deepest layer of the epidermis
Type of cell that are located in the deepest layer of the epidermis
Merkel cells and ___________ discs detect touch
The deepest layer of the epidermis
stratum basale composed of a single row of?
cuboidal or columnar keratinocytes
Superficial to the stratum basale and arranged in 8 to 10 layers of
many-sided keratinocytes fitting closely together.
At about the middle of the epidermis and consists of three to
five layers of flattened keratinocytes that are undergoing
A distinctive feature of cells in this layer is the presence
of darkly staining granules of a protein called
Also present in the keratinocytes are membraneenclosed which release a lipid-rich secretion called what?
only in the thick skin of areas such as the fingertips, palms, and
Which layer consists of three to five layers of flattened clear, dead
keratinocytes that contain large amounts of keratin and thickened
Which layer consists on average of 25 to 30 layers of flattened dead keratinocytes
Constant exposure of skin to
friction stimulates the formation of a
callus, an abnormal thickening
of the stratum corneum.
As the cells move from one epidermal layer to the
next, they accumulate more and more keratin, a process called
The second, deeper part of the skin and composed of
a strong connective tissue containing collagen and elastic fibers is called what?
The ___________ region makes up about one-fifth of the thickness of the total dermis layer
The dermis also has the ability to
stretch and recoil easily
vessels, nerves, glands, and hair follicles (epithelial invaginations
of the epidermis) are embedded in the
The Papillary regions surface area is greatly increased by
papillae also contain tactile receptors called
or corpuscles of touch, nerve endings that are sensitive to
touch, and free nerve endings, dendrites that lack any apparent
Which region is attached to
the subcutaneous layer?
reticular region consists of?
consists of dense irregular connective
tissue containing fibroblasts, bundles of collagen, and some
coarse elastic fibers
The study of the pattern of
epidermal ridges is called
impart a wide variety of colors to skin
Melanin, hemoglobin, and carotene
Which pigment cell is most plentiful in the epidermis of the penis,
nipples of the breasts, area just around the nipples (areolae),
face, and limbs?
the oxygen-carrying pigment in red
pigment that gives egg yolk and carrots their color.
stored in the stratum corneum and fatty areas of the
dermis and subcutaneous layer in response to excessive dietary
inability of an individual to produce melanin.
people affected by albinism, have melanocytes that are
or complete loss of melanocytes from patches of skin produces
irregular white spots.
buildup of the yellow pigment bilirubin in the skin.
someone who has stopped
breathing, the mucous membranes, nail beds, and skin appear bluish
redness of the skin, is caused by engorgement of capillaries
in the dermis with blood due to skin injury, exposure to heat, infection,
inflammation, or allergic reactions.
the skin, may occur in conditions such as shock and anemia.
A substance that removes hair is called
What are present on most skin surfaces except
the palms, palmar surfaces of the fingers, the soles, and plantar
surfaces of the feet
the superficial portion of the hair, which projects above the surface
of the skin
The shaft and root of the hair both
consist of three concentric layers of cells called?
medulla, cortex, and
cuticle of the hair
Layer of hair which
may be lacking in thinner hair, is composed of two or three
rows of irregularly shaped cells.
Layer of hair that forms the
major part of the shaft and consists of elongated cells.
the outermost layer, consists of a single layer
of thin, flat cells that are the most heavily keratinized
cuticle of the hair
Surrounding the root of the hair is
the hair follicle
downward continuation of the
epidermis is referred to as?
external root sheath
produced by the matrix
(described shortly) and forms a cellular tubular sheath of epithelium
between the external root sheath and the hair
internal root sheath
dermis surrounding the hair follicle is called
The base of each hair follicle and its surrounding dermal root
sheath is an onion-shaped structure is called?
the Bulb structure houses a nipple-shaped indentation called?
papilla of the
the papilla of the
hair contains what?
areolar connective tissue and many blood
vessels that nourish the growing hair follicle.
condition which results in the partial or complete
lack of hair, may result from genetic factors, aging, endocrine
disorders, chemotherapy, or skin disease
condition of excessive
the follicles produce
very fine, nonpigmented, downy hairs called
Prior to birth,
the lanugo of the eyebrows, eyelashes and scalp are shed and replaced
by long, coarse, heavily pigmented hairs called
The lanugo of the rest of the body are replaced by
hairs are commonly referred to as?
commonly called “peach fuzz,” which
are short, fine, pale hairs that are barely visible to the naked eye.
which glan that are also oil
glands which are simple, branched acinar glands.
Sebaceous glands secrete an oily substance called
There are three to four million sweat glands, or also called what?
glands release what?
sweat, or perspiration, into hair
follicles or onto the skin surface through pores
Sweat glands are
divided into two main types,
eccrine and apocrine
which gland are also known as merocrine sweat glands, are simple,
coiled tubular glands that are much more common than apocrine
Eccrine sweat glands
which gland is distributed
throughout the skin of most regions of the body, especially in the
skin of the forehead, palms, and soles
Eccrine sweat glands
The sweat produced by eccrine sweat glands consists of?
water, ions (mostly Na and Cl), urea, uric
acid, ammonia, amino acids, glucose, and lactic acid
Which glandare also simple, coiled tubular glands and
They are found mainly in the skin of the axilla (armpit), groin,
areolae (pigmented areas around the nipples) of the breasts, and
bearded regions of the face in adult males.
Apocrine sweat glands
Modified sweat glands in the external ear are called
combined secretion of the ceruminous and sebaceous glands is a
yellowish material called
what are the
three common forms of skin cancer
Basal cell carcinomas, Squamous cell
carcinomas, Malignant melanomas
which skin cancer account for
about 78% of all skin cancers. The tumors arise from cells in the stratum
basale of the epidermis and rarely metastasize
Basal cell carcinomas
which skin cancer account for about 20% of all skin cancers, arise
from squamous cells of the epidermis, and they have a variable tendency
which skin cancer arise from melanocytes and account for
about 2% of all skin cancers
Burn involves only the epidermis (Figure 5.9a). It is characterized by mild
pain and erythema (redness) but no blisters.
burn that destroys the epidermis and part of the
dermis (Figure 5.9b). Some skin functions are lost. In a second-degree
burn, redness, blister formation, edema, and pain result.
destroys the epidermis,
dermis, and subcutaneous layer (Figure 5.9c). Most skin functions are
lost. Such burns vary in appearance from marble-white to mahogany
colored to charred, dry wounds.
third-degree burn or full-thickness burn
Skin graft that transplanted skin is usually taken from the same individual
transplanted skin that is taken from identical twin?