Dermis

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Dermis
Skin.png
Cross-section of human skin
Normal Epidermis and Dermis with Intradermal Nevus 10x.JPG
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

The dermis or corium is a layer of skin between the epidermis (with which it makes up the cutis) and subcutaneous tissues, 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. [1] The dermis is tightly connected to the epidermis through a basement membrane. Structural components of the dermis are collagen, elastic fibers, and extrafibrillar matrix. [2] It also contains mechanoreceptors that provide the sense of touch and thermoreceptors 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.

Contents

Structure

The dermis is composed of three major types of cells: [3] fibroblasts, macrophages, and mast cells.

Apart from these cells, the dermis is also composed of matrix components such as collagen (which provides strength), elastin (which provides elasticity), and extrafibrillar matrix, an extracellular gel-like substance primarily composed of glycosaminoglycans (most notably hyaluronan), proteoglycans, and glycoproteins. [3]

Layers

Illustration of dermal circulation and layers Blausen 0802 Skin DermalCirculation.png
Illustration of dermal circulation and layers

Papillary dermis

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. [2] 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. [4]

Dermal papillae

Dermal papillae
Gray936.png
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, with neurolemma.
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) (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 fingerprints).

Blood vessels in the dermal papillae nourish all hair follicles and 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]

In mucous membranes, 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.

Reticular dermis

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. [2]

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 fibers give the dermis its properties of strength, extensibility, and elasticity. Within the reticular region are the roots 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 called Langer's lines, which are of some relevance in surgery and wound healing. [9]

See also

Related Research Articles

<span class="mw-page-title-main">Skin</span> Soft outer covering organ of vertebrates

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.

<span class="mw-page-title-main">Integumentary system</span> Skin and other protective organs

The integumentary system is the set of organs forming the outermost layer of an animal's body. It comprises the skin and its appendages, which act as a physical barrier between the external environment and the internal environment that it serves to protect and maintain the body of the animal. Mainly it is the body's outer skin.

<span class="mw-page-title-main">Scar</span> Area of fibrous tissue that replaces normal skin after an injury

A scar is an area of fibrous tissue that replaces normal skin after an injury. Scars result from the biological process of wound repair in the skin, as well as in other organs, and tissues of the body. Thus, scarring is a natural part of the healing process. With the exception of very minor lesions, every wound results in some degree of scarring. An exception to this are animals with complete regeneration, which regrow tissue without scar formation.

<span class="mw-page-title-main">Connective tissue</span> Type of biological tissue in animals

Connective tissue is one of the four primary types of animal tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops mostly from the mesenchyme, derived from the mesoderm, the middle embryonic germ layer. Connective tissue is found in between other tissues everywhere in the body, including the nervous system. The three meninges, membranes that envelop the brain and spinal cord, are composed of connective tissue. Most types of connective tissue consists of three main components: elastic and collagen fibers, ground substance, and cells. Blood, and lymph are classed as specialized fluid connective tissues that do not contain fiber. All are immersed in the body water. The cells of connective tissue include fibroblasts, adipocytes, macrophages, mast cells and leukocytes.

<span class="mw-page-title-main">Hair follicle</span> Organ found in the dermal layer of the mammalian skin that regulates hair growth

The hair follicle is an organ found in mammalian skin. It resides in the 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 complex interaction between hormones, neuropeptides, and immune cells. This complex interaction induces the hair follicle to produce different types of hair as seen on different parts of the body. For example, terminal hairs grow on the scalp and lanugo hairs are seen covering the bodies of fetuses in the uterus and in some newborn babies. The process of hair growth occurs in distinct sequential stages: anagen is the active growth phase, catagen is the regression of the hair follicle phase, telogen is the resting stage, exogen is the active shedding of hair phase and kenogen is the phase between the empty hair follicle and the growth of new hair.

<span class="mw-page-title-main">Skin condition</span> Any medical condition that affects the integumentary system

A skin condition, also known as cutaneous condition, is any medical condition that affects the integumentary system—the organ system that encloses the body and includes skin, nails, and related muscle and glands. The major function of this system is as a barrier against the external environment.

<span class="mw-page-title-main">Nevus</span> Mole or birthmark; visible, circumscribed, chronic skin lesion

Nevus is a nonspecific medical term for a visible, circumscribed, chronic lesion of the skin or mucosa. The term originates from nævus, which is Latin for "birthmark"; however, a nevus can be either congenital or acquired. Common terms, including mole, birthmark, and beauty mark, are used to describe nevi, but these terms do not distinguish specific types of nevi from one another.

<span class="mw-page-title-main">Subcutaneous tissue</span> Lowermost layer of the integumentary system in vertebrates

The subcutaneous tissue, also called the hypodermis, hypoderm, subcutis, or superficial fascia, is the lowermost layer of the integumentary system in vertebrates. The types of cells found in the layer are fibroblasts, adipose cells, and macrophages. The subcutaneous tissue is derived from the mesoderm, but unlike the dermis, it is not derived from the mesoderm's dermatome region. It consists primarily of loose connective tissue, and contains larger blood vessels and nerves than those found in the dermis. It is a major site of fat storage in the body.

<span class="mw-page-title-main">Loose connective tissue</span> Type of connective tissue in animals

Loose connective tissue, also known as areolar tissue, is a cellular connective tissue with thin and relatively sparse collagen fibers. They have a semi-fluid matrix with lesser proportions of fibers. Its ground substance occupies more volume than the fibers do. It has a viscous to gel-like consistency and plays an important role in the diffusion of oxygen and nutrients from the capillaries that course through this connective tissue as well as in the diffusion of carbon dioxide and metabolic wastes back to the vessels. Moreover, loose connective tissue is primarily located beneath the epithelia that cover the body surfaces and line the internal surfaces of the body. It is also associated with the epithelium of glands and surrounds the smallest blood vessels. This tissue is thus the initial site where pathogenic agents, such as bacteria that have breached an epithelial surface, are challenged and destroyed by cells of the immune system.

Protection from mechanical injury, chemical hazards, and bacterial invasion is provided by the skin because the epidermis is relatively thick and covered with keratin. Secretions from sebaceous glands and sweat glands also benefit this protective barrier. In the event of an injury that damages the skin's protective barrier, the body triggers a response called wound healing. After hemostasis, inflammation white blood cells, including phagocytic macrophages arrive at the injury site. Once the invading microorganisms have been brought under control, the skin proceeds to heal itself. The ability of the skin to heal even after considerable damage has occurred is due to the presence of stem cells in the dermis and cells in the stratum basale of the epidermis, all of which can generate new tissue.

Snakeskin may either refer to the skin of a live snake, the shed skin of a snake after molting, or to a type of leather that is made from the hide of a dead snake. Snakeskin and scales can have varying patterns and color formations, providing protection via camouflage from predators. The colors and iridescence in these scales are largely determined by the types and amount of chromatophores located in the dermis of the snake skin. The snake's skin and scales are also an important feature to their locomotion, providing protection and minimizing friction when gliding over surfaces.

<span class="mw-page-title-main">Stroma (tissue)</span> Part of a tissue or organ with a structural or connective role

Stroma is the part of a tissue or organ with a structural or connective role. It is made up of all the parts without specific functions of the organ - for example, connective tissue, blood vessels, ducts, etc. The other part, the parenchyma, consists of the cells that perform the function of the tissue or organ.

<span class="mw-page-title-main">Human skin</span> Organ covering the outside of the human body

The human skin is the outer covering of the body and is the largest organ of the integumentary system. The skin has up to seven layers of ectodermal tissue guarding muscles, bones, ligaments and internal organs. Human skin is similar to most of the other mammals' skin, and it is very similar to pig skin. Though nearly all human skin is covered with hair follicles, it can appear hairless. There are two general types of skin: hairy and glabrous skin (hairless). The adjective cutaneous literally means "of the skin".

Eimer's organs are sensory organs in which the epidermis is modified to form bulbous papillae. First isolated by Theodor Eimer from the European mole in 1871, these organs are present in many moles, and are particularly common in the star-nosed mole, which bears 25,000 of them on its unique tentacled snout. The organs are formed from a stack of epidermal cells, which is innervated by nerve processes from myelinated fibers in the dermis, which form terminal swellings just below the outer keratinized layer of epidermis. They contain a Merkel cell-neurite complex in the epidermis and a lamellated corpuscle in the dermal connective tissue.

<span class="mw-page-title-main">Syringocystadenoma papilliferum</span> Medical condition

Syringocystadenoma papilliferum is a rare non-malignant adnexal neoplasm that develops from apocrine or eccrine sweat glands and can be identified histologically by cystic, papillary, and ductal invaginations into the dermis lined by double-layered outer cuboidal and luminal high columnar epithelium and connected to the epidermis.

<span class="mw-page-title-main">Photoaging</span> Ultraviolet light-induced biological development over time

Photoaging or photoageing is a term used for the characteristic changes to skin induced by chronic UVA and UVB exposure. Tretinoin is the best studied retinoid in the treatment of photoaging.

Elaunin is a component of elastic fibers formed from a deposition of elastin between oxytalan fibers. It is found in the periodontal ligament and in the connective tissue of the dermis, particularly in association with sweat glands.

Role of skin in locomotion describes how the integumentary system is involved in locomotion. Typically the integumentary system can be thought of as skin, however the integumentary system also includes the segmented exoskeleton in arthropods and feathers of birds. The primary role of the integumentary system is to provide protection for the body. However, the structure of the skin has evolved to aid animals in their different modes of locomotion. Soft bodied animals such as starfish rely on the arrangement of the fibers in their tube feet for movement. Eels, snakes, and fish use their skin like an external tendon to generate the propulsive forces need for undulatory locomotion. Vertebrates that fly, glide, and parachute also have a characteristic fiber arrangements of their flight membranes that allows for the skin to maintain its structural integrity during the stress and strain experienced during flight.

Dermal fibroblasts are cells within the dermis layer of skin which are responsible for generating connective tissue and allowing the skin to recover from injury. Using organelles, dermal fibroblasts generate and maintain the connective tissue which unites separate cell layers. Furthermore, these dermal fibroblasts produce the protein molecules including laminin and fibronectin which comprise the extracellular matrix. By creating the extracellular matrix between the dermis and epidermis, fibroblasts allow the epithelial cells of the epidermis to affix the matrix, thereby allowing the epidermal cells to effectively join together to form the top layer of the skin.

<span class="mw-page-title-main">Dermoepidermal junction</span>

The dermoepidermal junction or dermal-epidermal junction (DEJ) is the interface between the epidermal and the dermal layers of the skin. The basal cells of the epidermis connect to the basement membrane by the anchoring filaments of hemidesmosomes; the cells of the papillary layer of the dermis are attached to the basement membrane by anchoring fibrils, which consist of type VII collagen.

References

  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.
  2. 1 2 3 Marks, James G; Miller, Jeffery (2006). Lookingbill and Marks' Principles of Dermatology (4th ed.). Elsevier Inc. Page 8–9. ISBN   1-4160-3185-5.
  3. 1 2 malvi (4 March 2011). "The Ageing Skin - Part 1 - Structure of Skin and Introduction - Articles". PharmaXChange.info.
  4. http://microvet.arizona.edu/Courses/vsc422/secure/VSC422AppledHistologyLabHandout.pdf%5B%5D
  5. "Dermal papillae". Probert Encyclopaedia. Archived from the original on 2011-06-08.
  6. "Friction Skin". Ridges and Furrows. Archived from the original on 2021-04-22. Retrieved 2016-12-23.
  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.
  9. Ross M, Pawlina W (2011). Histology: A Text and Atlas (6th ed.). Lippincott Williams & Wilkins. p. 498. ISBN   978-0-7817-7200-6.