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The dermis or corium is a layer of
skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have differe ...

skin
between the
epidermis The epidermis is the outermost of the three layers that make up the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the am ...
(with which it makes up the cutis) and
subcutaneous tissue The subcutaneous tissue (), also called the hypodermis, hypoderm (), subcutis, superficial fascia, is the lowermost layer of the integumentary system The integumentary system is the set of organs forming the outermost layer of an animal's body. ...
s, that primarily consists of
dense irregular connective tissue Dense irregular connective tissue has fibers that are not arranged in parallel bundles as in dense regular connective tissue Dense regular connective tissue provides connection between different tissues in the human body. The collagen upright=1.5 ...
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 The basement membrane is a thin, pliable sheet-like type of extracellular matrix In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes ...
. Structural components of the dermis are
collagen upright=1.5, Tropocollagen molecule: three left-handed procollagens (red, green, blue) join to form a right-handed triple helical tropocollagen. Collagen () is the main structural protein Proteins are large biomolecules or macromolecules that ...
,
elastic fiber Elastic fibers (or yellow fibers) are an essential component of the extracellular matrix composed of bundles of proteins (elastin) which are produced by a number of different cell types including fibroblasts, endothelial, smooth muscle, and airw ...
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 A mechanoreceptor, also called mechanoceptor, is a sensory cell that responds to mechanical pressure Pressure (symbol: ''p'' or ''P'') is the force In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epi ...
s that provide the sense of
touch The somatosensory system is a part of the sensory nervous system. The somatosensory system is a complex system of sensory neurons and neural pathways that responds to changes at the surface or inside the body. The axons (as afferent nerve fibers) ...

touch
and
thermoreceptorA thermoreceptor is a non-specialised sense receptor, or more accurately the receptive portion of a sensory neuron Sensory neurons, also known as afferent neurons, are neurons in the nervous system In Biology, biology, the nervous system ...
s that provide the sense of
heat In thermodynamics, heat is energy in transfer to or from a thermodynamic system, by mechanisms other than thermodynamic work or transfer of matter. The various mechanisms of energy transfer that define heat are stated in the next section ...

heat
. In addition,
hair follicles The hair follicle is an organ found in mammalian skin. It resides in the dermal layer of the skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulat ...

hair follicles
,
sweat glands Sweat glands, also known as sudoriferous or sudoriparous glands, , are small tubular structures of the skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection ...
, sebaceous glands (oil glands),
apocrine glands Apocrine () is a term used to classify exocrine glands in the study of histology Histology, also known as microscopic anatomy or microanatomy, is the branch of biology Biology is the natural science that studies life and living organism ...
,
lymphatic vessels The lymphatic vessels (or lymph vessels or lymphatics) are thin-walled vessels (tubes) structured like blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels t ...
, nerves and
blood vessels The blood vessels are the components of the circulatory system The circulatory system, also called the cardiovascular system or the vascular system, is an Biological system, organ system that permits blood to circulate and transport nutrien ...
are present in the dermis. Those blood vessels provide nourishment and waste removal for both dermal and epidermal cells.


Structure

The dermis is composed of three major types of
cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic cell, a small room, hut, or cave in which a monk or religious recluse lives * Prison cell, a room used to hold peopl ...
:
fibroblasts A fibroblast is a type of biological cell that synthesizes the extracellular matrix and collagen, produces the structural framework ( stroma) for animal tissues, and plays a critical role in wound healing Wound healing refers to a living organi ...
,
macrophages Macrophages (abbreviated as MPhi, φ, MΦ or MP) ( el, large eaters, from Greek ''μακρός'' (') = large, ''φαγεῖν'' (') = to eat) are a type of white blood cell of the immune system that engulfs and digests anything that does not have ...
, and
mast cells A mast cell (also known as a mastocyte or a labrocyte) is a resident cell of connective tissue that contains many granules rich in histamine and heparin. Specifically, it is a type of granulocyte derived from the myeloid stem cell that is a par ...

mast cells
. Apart from these cells, the dermis is also composed of
matrix Matrix or MATRIX may refer to: Science and mathematics * Matrix (mathematics), a rectangular array of numbers, symbols, or expressions * Matrix (logic), part of a formula in prenex normal form * Matrix (biology), the material in between a eukaryoti ...
components such as
collagen upright=1.5, Tropocollagen molecule: three left-handed procollagens (red, green, blue) join to form a right-handed triple helical tropocollagen. Collagen () is the main structural protein Proteins are large biomolecules or macromolecules that ...
(which provides
strength Physical strength *Physical strength, as in people or animals *Hysterical strength, extreme strength occurring when people are in life-and-death situations *Superhuman strength, great physical strength far above human capability *A common attrib ...
),
elastin Elastin is a key protein Proteins are large biomolecules or macromolecules that are comprised of one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzy ...
(which provides
elasticity Elasticity often refers to: *Elasticity (physics), continuum mechanics of bodies that deform reversibly under stress Elasticity may also refer to: Information technology * Elasticity (data store), the flexibility of the data model and the clu ...
), and extrafibrillar matrix, an extracellular gel-like substance primarily composed of
glycosaminoglycans . For polysaccharide nomenclature see here. R1, R2, R3 may have different values. Image:Hyaluronan.svg, 240px, Hyaluronic acid, Hyaluronan (-4GlcUA''β''1-3GlcNAc''β''1-)n Glycosaminoglycans (GAGs) or mucopolysaccharides are long linear polysac ...

glycosaminoglycans
(most notably
hyaluronan Hyaluronic acid (; abbreviated HA; conjugate base hyaluronate), also called hyaluronan, is an anionic, nonsulfated glycosaminoglycan distributed widely throughout connective, epithelial, and neural tissues. It is unique among glycosaminogly ...

hyaluronan
),
proteoglycans Proteoglycans are protein Proteins are large biomolecules or macromolecules that are comprised of one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including E ...
, and
glycoproteins Glycoproteins are protein Proteins are large biomolecules or macromolecules that are comprised of one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including ...
.


Layers


Papillary dermis

The papillary dermis is the uppermost layer of the dermis. It intertwines with the
rete ridges Rete pegs (also known as rete processes or rete ridges) are the epithelial extensions that project into the underlying connective tissue in both skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate anima ...
of the epidermis and is composed of fine and loosely arranged collagen fibers. The papillary region is composed of loose
areolar connective tissue Loose connective tissue (also called areolar connective tissue) is a category of connective tissue Connective tissue is one of the four basic types of animal tissue (biology), tissue, along with epithelial tissue, muscle tissue, and nervous tis ...
. 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 Blood is a body fluid Body fluids, bodily fluids, or biofluids are liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an applied shear s ...

blood
capillaries A capillary is a small blood vessel from 5 to 10 micrometres (μm) in diameter, and having a wall one endothelial cell thick. They are the smallest blood vessels in the body: they convey blood between the arterioles and venules. These microvessel ...

capillaries
or tactile
Meissner's corpuscles Tactile corpuscles or Meissner's corpuscles are a type of mechanoreceptor discovered by anatomy, anatomist Georg Meissner (1829–1905) and Rudolf Wagner. This corpuscle is a type of nerve ending in the skin that is responsible for sensitivity to li ...
.


Dermal papillae

The dermal papillae (DP) (singular ''papilla'', diminutive of Latin ''papula'', 'pimple') are small, nipple-like extensions (or interdigitations) of the dermis into the
epidermis The epidermis is the outermost of the three layers that comprise the skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Oth ...
. At the surface of the skin in hands and feet, they appear as epidermal, papillary or friction ridges (colloquially known as
fingerprint A fingerprint is an impression left by the friction ridge The dermis or corium is a layer of skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, reg ...

fingerprint
s). Blood vessels in the dermal papillae nourish all
hair follicle The hair follicle is an Organ (anatomy), organ found in mammalian skin. It resides in the Dermis, dermal layer of the skin and is made up of 20 different cell types, each with distinct functions. The hair follicle regulates hair growth via a comple ...

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 A mucous membrane or mucosa is a biological membrane, membrane that lines various cavities in the body and covers the surface of internal organs. It consists of one or more layers of Epithelium, epithelial cells overlying a layer of loose connecti ...
s, the equivalent structures to dermal papillae are generally termed "connective tissue papillae", which interdigitate with the
rete pegs Rete pegs (also known as rete processes or rete ridges) are the epithelial extensions that project into the underlying connective tissue in both skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate anima ...
of the superficial epithelium. Dermal papillae are less pronounced in thin skin areas.


Reticular dermis

The reticular dermis is the lower layer of the dermis, found under the papillary dermis, composed of
dense irregular connective tissue Dense irregular connective tissue has fibers that are not arranged in parallel bundles as in dense regular connective tissue Dense regular connective tissue provides connection between different tissues in the human body. The collagen upright=1.5 ...
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, elastic, and reticular fibers that weave throughout it. These
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metabol ...

protein
fibers give the dermis its properties of
strength Physical strength *Physical strength, as in people or animals *Hysterical strength, extreme strength occurring when people are in life-and-death situations *Superhuman strength, great physical strength far above human capability *A common attrib ...
,
extensibility Extensibility is a software engineering and systems design principle that provides for future growth. Extensibility is a measure of the ability to extend a system A system is a group of Interaction, interacting or interrelated elements that ...

extensibility
, and elasticity. Within the reticular region are the roots of the hair,
sebaceous glands A sebaceous gland is a microscopic exocrine gland in the skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, ...
,
sweat glands Sweat glands, also known as sudoriferous or sudoriparous glands, , are small tubular structures of the skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection ...
,
receptors Receptor may refer to: *Sensory receptor, in physiology, any structure which, on receiving environmental stimuli, produces an informative nerve impulse *Receptor (biochemistry), in biochemistry, a protein molecule that receives and responds to a ne ...
, nails, and blood vessels. The orientation of collagen fibers within the reticular dermis creates lines of tension called
Langer's lines Langer's lines, Langer lines of skin tension, or sometimes called cleavage lines, are Topological map, topological lines drawn on a map of the human body. They are parallel to the natural orientation of collagen fibers in the dermis, and perpendicul ...

Langer's lines
, which are of some relevance in surgery and wound healing.


See also

*
List of cutaneous conditions Many conditions affect the human integumentary system—the organ system covering the entire surface of the Human body, body and composed of Human skin, skin, hair, Nail (anatomy), nails, and related muscle and glands. The major function of t ...
*
Epidermis The epidermis is the outermost of the three layers that comprise the skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Oth ...

Epidermis
* Subcutaneous layer


References

{{Authority control Skin anatomy Routes of administration