Dermis

Dermal papillae
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 [edit on Wikidata]

Dermis
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 [edit on Wikidata]

Thedermisorcoriumis a layer ofskinbetween theepidermis(with which it makes up thecutis) andsubcutaneous tissues,that primarily consists ofdense irregular connective tissueand 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 containsmechanoreceptorsthat provide the sense oftouchandthermoreceptorsthat provide the sense ofheat.In addition,hair follicles,sweat glands,sebaceous glands (oil glands),apocrine glands,lymphatic vessels,nerves andblood vesselsare 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 ofcells:^[3]fibroblasts,macrophages,andmast cells.

Apart from these cells, the dermis is also composed ofmatrixcomponents such ascollagen(which providesstrength),elastin(which provideselasticity), andextrafibrillar matrix,an extracellular gel-like substance primarily composed ofglycosaminoglycans(most notablyhyaluronan),proteoglycans,andglycoproteins.^[3]

Layers

Papillary dermis

Thepapillary dermisis the uppermost layer of the dermis. It intertwines with therete ridgesof 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 calledpapillaeordermal papillaespecifically, that extend toward the epidermis and contain either terminal networks ofblood capillariesor tactileMeissner's corpuscles.^[4]

Epidermis, papillary dermis and reticular dermis.

Dermal papillae

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 folliclesand bring nutrients and oxygen to the lower layers of epidermal cells. The pattern of ridges produced in hands and feet are partly genetically determined features that are developed 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.^[5]

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.^[6]

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.^[7]

Dermal papillae also play a pivotal role in hair formation, growth and cycling.^[8]

Inmucous membranes,the equivalent structures to dermal papillae are generally termed "connective tissue papillae", which interdigitate with therete pegsof the superficial epithelium. Dermal papillae are less pronounced in thin skin areas.

Reticular dermis

Thereticular dermisis the lower layer of the dermis, found under the papillary dermis, composed ofdense irregular connective tissuefeaturing 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 fibersthat weave throughout it. Theseproteinfibers 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.^[9]

References

^James, William; Berger, Timothy; Elston, Dirk (2005).Andrews' Diseases of the Skin: Clinical Dermatology(10th ed.). Saunders. Pages 1, 11–12.ISBN 0-7216-2921-0.
^^a ^b ^cMarks, James G; Miller, Jeffery (2006).Lookingbill and Marks' Principles of Dermatology(4th ed.). Elsevier Inc. Page 8–9.ISBN 1-4160-3185-5.
^^a ^bmalvi (4 March 2011)."The Ageing Skin - Part 1 - Structure of Skin and Introduction - Articles".PharmaXChange.info.
^http://microvet.arizona.edu/Courses/vsc422/secure/VSC422AppledHistologyLabHandout.pdf^{[permanent dead link]}
^"Dermal papillae".Probert Encyclopaedia. Archived fromthe originalon 2011-06-08.
^"Friction Skin".Ridges and Furrows. Archived fromthe originalon 2021-04-22.Retrieved2016-12-23.
^Hicklin, R. Austin (2009)."Anatomy of Friction Ridge Skin".Encyclopedia of Biometrics.Springer US: 23–28.doi:10.1007/978-0-387-73003-5_48.ISBN 978-0-387-73002-8.
^Lin, Chang-min; et al. (October 2008). "Microencapsulated human hair dermal papilla cells: a substitute for dermal papilla?".Archives of Dermatological Research.300(9). Springer: 531–535.doi:10.1007/s00403-008-0852-3.PMID 18418617.S2CID 21632556.
^Ross M, Pawlina W (2011).Histology: A Text and Atlas(6th ed.). Lippincott Williams & Wilkins. p. 498.ISBN 978-0-7817-7200-6.

[Andrews-1] James, William; Berger, Timothy; Elston, Dirk (2005).Andrews' Diseases of the Skin: Clinical Dermatology(10th ed.). Saunders. Pages 1, 11–12.ISBN 0-7216-2921-0.

[Lookingbill-2] Marks, James G; Miller, Jeffery (2006).Lookingbill and Marks' Principles of Dermatology(4th ed.). Elsevier Inc. Page 8–9.ISBN 1-4160-3185-5.

[ageingskin-3] vi (4 March 2011)."The Ageing Skin - Part 1 - Structure of Skin and Introduction - Articles".PharmaXChange.info.

[4] ttp://microvet.arizona.edu/Courses/vsc422/secure/VSC422AppledHistologyLabHandout.pdf^{[permanent dead link]}

[5] "Dermal papillae".Probert Encyclopaedia. Archived fromthe originalon 2011-06-08.

[6] "Friction Skin".Ridges and Furrows. Archived fromthe originalon 2021-04-22.Retrieved2016-12-23.

[7] Hicklin, R. Austin (2009)."Anatomy of Friction Ridge Skin".Encyclopedia of Biometrics.Springer US: 23–28.doi:10.1007/978-0-387-73003-5_48.ISBN 978-0-387-73002-8.

[8] Lin, Chang-min; et al. (October 2008). "Microencapsulated human hair dermal papilla cells: a substitute for dermal papilla?".Archives of Dermatological Research.300(9). Springer: 531–535.doi:10.1007/s00403-008-0852-3.PMID 18418617.S2CID 21632556.

[ross-9] Ross M, Pawlina W (2011).Histology: A Text and Atlas(6th ed.). Lippincott Williams & Wilkins. p. 498.ISBN 978-0-7817-7200-6.

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