| Dermis | |
|---|---|
 Cross-section of human skin | |
 Cross section of skin under a microscope | |
| Details | |
| Part of | Skin |
| Identifiers | |
| MeSH | D020405 |
| TA98 | A16.0.00.010 |
| TA2 | 7047 |
| TH | H3.12.00.1.03001 |
| FMA | 70323 |
| Anatomical terminology | |
Thedermis orcorium is a layer ofskin between theepidermis (with which it makes up thecutis) andsubcutaneous tissues, that primarily consists ofdense 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.[1] The dermis is tightly connected to the epidermis through abasement membrane. Structural components of the dermis arecollagen,elastic fibers, andextrafibrillar matrix.[2] It also containsmechanoreceptors that provide the sense oftouch andthermoreceptors that provide the sense ofheat. In addition,hair follicles,sweat glands,sebaceous glands (oil glands),apocrine glands,lymphatic vessels, nerves andblood 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 ofcells:[3]fibroblasts,macrophages, andmast cells.
Apart from these cells, the dermis is also composed ofmatrix components such ascollagen (which providesstrength),elastin (which provideselasticity), andextrafibrillar matrix, an extracellular gel-like substance primarily composed ofglycosaminoglycans (most notablyhyaluronan),proteoglycans, andglycoproteins.[3]
Thepapillary dermis is the uppermost layer of the dermis. It intertwines with therete ridges of the epidermis and is composed of fine and loosely arranged collagen fibers.[2]The papillary region is composed of looseareolar connective tissue. It is named for its fingerlike projections calledpapillae ordermal papillae specifically, that extend toward the epidermis and contain either terminal networks ofbloodcapillaries or tactileMeissner's corpuscles.[4]
| Dermal papillae | |
|---|---|
 Papilla of the hand, treated with acetic acid. Magnified 350 times. A. Side view of a papilla of the hand. a. Cortical layer. b. Tactile corpuscle. c. Small nerve of the papilla, withneurolemma. d. Its two nervous fibers running in spiral coils around the tactile corpuscle. e. Apparent termination of one of these fibers. B. Tactile papilla seen from above so as to show its transverse section. a. Cortical layer. b. Nerve fiber. c. Outer layer of the tactile body, with nuclei. d. Clear interior substance. | |
| Details | |
| Identifiers | |
| Latin | papillae dermis |
| MeSH | D020405 |
| TA98 | A16.0.00.010 |
| TA2 | 7047 |
| TH | H3.12.00.1.03001 |
| FMA | 70323 |
| Anatomical terminology | |
The dermal papillae (DP) (singularpapilla, diminutive of Latinpapula, 'pimple') are small, nipple-like extensions (or interdigitations) of the dermis into theepidermis. At the surface of the skin in hands and feet, they appear as epidermal, papillary or friction ridges (colloquially known asfingerprints).
Blood vessels in the dermal papillae nourish allhair follicles and bring nutrients and oxygen to the lower layers of epidermal cells. The pattern of ridges produced in hands and feet are only partly genetically determined features that are developed before birth, the timing and events around the ridge formation area also contributing.[5] 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.[6]
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 the surface area prevents the dermal and epidermal layers from separating by strengthening the junction between them. With age, the papillae tend to flatten and sometimes increase in number.[7]
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.[8]
Dermal papillae also play a pivotal role in hair formation, growth and cycling.[9]
Inmucous membranes, the equivalent structures to dermal papillae are generally termed "connective tissue papillae", which interdigitate with therete pegs of the superficial epithelium.Dermal papillae are less pronounced in thin skin areas.
Thereticular dermis is the lower layer of the dermis, found under the papillary dermis, composed ofdense irregular connective tissue featuring densely-packed collagen fibers. It is the primary location of dermal elastic fibers.[2]
The reticular region is usually much thicker than the overlying papillary dermis. It receives its name from the dense concentration ofcollagenous,elastic, andreticular fibers that weave throughout it. Theseprotein fibers give the dermis its properties ofstrength,extensibility, and elasticity. Within the reticular region are theroots of the hair,sebaceous glands,sweat glands,receptors,nails, and blood vessels. The orientation of collagen fibers within the reticular dermis creates lines of tension calledLanger's lines, which are of some relevance in surgery and wound healing.[10]
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