Dermis
What is embedded in the dermal layer?
blood vessels, nerves, glands, and hair follicles
What occupies the spaces between fibers in the reticular region?
blood vessels, nerves, hair follicles, sebaceous glands, and sudoriferous glands
What does the reticular region contain?
bundles of thick collagen fibers, scattered fibroblasts, and various wandering cells such as macrophages
What do all dermal papillae contain?
capillary loops (blood vessels)
What do a few cells present in the dermis include?
predominately fibroblasts, with some macrophages, and a few adipocytes near the subQ layer
What forms fingerprints or footprints?
sweat and epidermal ridges
How do dermal papillae fit together, and what does this do?
with the complementary epidermal ridge to form an extremely strong junction between the two layers; strengthens the skin against shearing forces that attempt to separate the epidermis from the dermis
Do identical twins have the same fingerprint?
NO
What do epidermal ridges create?
a strong bond between the epidermis and dermis in a region of high mechanical stress
How much of the thickness of the total layer does the papillary region make up?
about one-fifth of the thickness
What does increased dermal contact surface and its extensive network of small blood vessels serve as?
an important source of nutrition for the overlying epidermis
What is the dermis composed of?
dense irregular connective tissue containing collagen, and elastic fibers
What is the papillary region's surface area increased by?
dermal papillae
When are epidermal ridges produced?
during the third month of fetal development as downward projections of the epidermis into the dermis between the dermal papillae
How are epidermal ridges and surface area related?
epidermal ridges increase the surface area, increasing the grip of the hand or foot by increasing friction, and increasing the number of corpuscles of touch, increasing tactile sensitivity
Why is the dermis essential?
for the survival of the epidermis
What do other dermal papillae contain?
free nerve endings, which are dendrites that lack apparent structural specialization
How do molecules diffuse?
from small blood capillaries in the dermal papillae, to the cells of the stratum basale
How is epidermal ridge pattern determined?
genetically and is unique for each individual
How are collagen fibers in the reticular region arranged?
in a netlike manner and have more regular arrangement the those in the papillary region
What do free nerve endings do?
initiate signals that give rise to sensations of warmth, coolness, pain, tickling, and itching
What helps the skin resist stretching?
more regular orientation of the large collagen fibers in the reticular region
What do some dermal papillae contain?
nerve endings of tactile receptors called corpuscles of touch or meissner corpuscles
How does ridge patter change during life?
only to enlarge with growth
Where are the regions of greatest thickness of dermis in the body?
palms, and soles
What does the combination of collagen and elastic fibers in the reticular region provide?
provides the skin with strength, extensibility, and elasticity
What are dermal papillae?
small, nipple shaped structures that project into the undersurface of the epidermis
What can be present in the deepest part of the reticular region?
some adipose cells, along with some coarse elastic fibers
What are epidermal ridges, and where are they?
straight lines, or a pattern of loops and whorls on the surfaces of palms, fingers, soles, and toes
What is dermatoglyphics?
study of the pattern of epidermal ridges
What is the reticular region attached to?
the subQ layer
What does the dermal papillae increase?
the surface contact between the dermis and epidermis
What does the papillary region contain?
thin collagen, and fine elastic fibers
What two regions can the dermis be divided into?
thin superficial papillary region thick deeper reticular region
What kind of ability does the dermis have?
to stretch and recoil easily