The dermis or corium is a layer of skin
between the epidermis
(with which it makes up the cutis
) and subcutaneous tissue
s, that primarily consists of dense irregular connective tissue
and cushions the body from stress and strain. It is divided into two layers, the superficial area adjacent to the epidermis called the papillary region and a deep thicker area known as the reticular dermis.
[James, William; Berger, Timothy; Elston, Dirk (2005). ''Andrews' Diseases of the Skin: Clinical Dermatology'' (10th ed.). Saunders. Pages 1, 11–12. .]
The dermis is tightly connected to the epidermis through a basement membrane
. Structural components of the dermis are collagen
, elastic fiber
s, and extrafibrillar matrix
[Marks, James G; Miller, Jeffery (2006). ''Lookingbill and Marks' Principles of Dermatology'' (4th ed.). Elsevier Inc. Page 8–9. .]
It also contains mechanoreceptor
s that provide the sense of touch
s that provide the sense of heat
. In addition, hair follicles
, sweat glands
, sebaceous glands (oil glands)
, apocrine glands
, lymphatic vessels
, nerves and blood vessels
are present in the dermis. Those blood vessels provide nourishment and waste removal for both dermal and epidermal cells.
The dermis is composed of three major types of cells
, and mast cells
Apart from these cells, the dermis is also composed of matrix
components such as collagen
(which provides strength
(which provides elasticity
), and extrafibrillar matrix
, an extracellular gel-like substance primarily composed of glycosaminoglycans
(most notably hyaluronan
, and glycoproteins
The papillary dermis is the uppermost layer of the dermis. It intertwines with the rete ridges
of the epidermis and is composed of fine and loosely arranged collagen fibers.
The papillary region is composed of loose areolar connective tissue
. It is named for its fingerlike projections called ''papillae'' or ''dermal papillae'' specifically, that extend toward the epidermis and contain either terminal networks of blood capillaries
or tactile Meissner's corpuscles
The dermal papillae (DP) (singular ''papilla'', diminutive of Latin ''papula'', 'pimple') are small, nipple-like extensions (or interdigitations) of the dermis into the epidermis
. At the surface of the skin in hands and feet, they appear as epidermal, papillary or friction ridges (colloquially known as fingerprint
Blood vessels in the dermal papillae nourish all hair follicle
s and bring nutrients and oxygen to the lower layers of epidermal cells. The pattern of ridges they produce in hands and feet are partly genetically determined features that develop before birth. They remain substantially unaltered (except in size) throughout life, and therefore determine the patterns of fingerprints, making them useful in certain functions of personal identification.
The dermal papillae are part of the uppermost layer of the dermis, the papillary dermis, and the ridges they form greatly increase the surface area between the dermis and epidermis. Because the main function of the dermis is to support the epidermis, this greatly increases the exchange of oxygen, nutrients, and waste products between these two layers. Additionally, the increase in surface area prevents the dermal and epidermal layers from separating from each other by strengthening the junction between them. With age, the papillae tend to flatten and sometimes increase in number.
The skin of the hands and fingers and the feet and toes is known by forensic scientists as friction ridge skin. It is known by anatomists as thick skin, volar skin or hairless skin. It has raised ridges, a thicker and more complex epidermis, increased sensory abilities, and the absence of hair and sebaceous glands. The ridges increase friction for improved grasping.
Dermal papillae also play a pivotal role in hair formation, growth and cycling.
In mucous membrane
s, the equivalent structures to dermal papillae are generally termed "connective tissue papillae", which interdigitate with the rete pegs
of the superficial epithelium.
Dermal papillae are less pronounced in thin skin areas.
The reticular dermis is the lower layer of the dermis, found under the papillary dermis, composed of dense irregular connective tissue
featuring densely-packed collagen fibers. It is the primary location of dermal elastic fibers.
The reticular region is usually much thicker than the overlying papillary dermis. It receives its name from the dense concentration of collagenous
, and reticular
fibers that weave throughout it. These protein
fibers give the dermis its properties of strength
, and elasticity. Within the reticular region are the roots of the hair
, sebaceous glands
, sweat glands
, and blood vessels. The orientation of collagen fibers within the reticular dermis creates lines of tension called Langer's lines
, which are of some relevance in surgery and wound healing.
* List of cutaneous conditions
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