Integumentary System: Difference between revisions

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* Hair
* Hair
* Nails.  
* Nails.  
In addition to its barrier function, this system performs many intricate functions such as body temperature regulation, cell fluid maintenance, synthesis of [[Vitamin D Deficiency|Vitamin D]], and detection of stimuli. The various components of this system work in conjunction to carry out these functions<ref>Kim JY, Dao H. [https://www.ncbi.nlm.nih.gov/books/NBK554386/ Physiology, Integument]. InStatPearls [Internet] 2020 Feb 17. StatPearls Publishing.Available from:https://www.ncbi.nlm.nih.gov/books/NBK554386/ (last accessed 23.10.2020)</ref>.
In addition to its barrier function, this system performs many intricate functions such as body temperature regulation, cell fluid maintenance, synthesis of [[Vitamin D Deficiency|Vitamin D]], and detection of stimuli. The various components of this system work in conjunction to carry out these functions<ref name=":0">Kim JY, Dao H. [https://www.ncbi.nlm.nih.gov/books/NBK554386/ Physiology, Integument]. InStatPearls [Internet] 2020 Feb 17. StatPearls Publishing.Available from:https://www.ncbi.nlm.nih.gov/books/NBK554386/ (last accessed 23.10.2020)</ref>.


== An Introduction - Key Facts  ==
== An Introduction - Key Facts  ==


#Skin accounts for about 16% of your total body weight&nbsp;<ref name="One" />  
#Skin accounts for about 16% of your total body weight&nbsp;<ref name="One">Martini FH, Nath, JL. Fundamentals of Anatomy and Physiology. 8th ed. Pearson. San Francisco: Benjamin Cummings. 2009</ref>  
#Its surface area covers between 1.5-2m<sup>2&nbsp;</sup><ref name="One" />  
#Its surface area covers between 1.5-2m<sup>2&nbsp;</sup><ref name="One" />  
#Weighs approximately 3-5kg&nbsp;<ref name="Two">Turkington C, Dover JS. Skin Deep. 3rd ed. New York: Checkmark Books. 2007</ref>  
#Weighs approximately 3-5kg&nbsp;<ref name="Two">Turkington C, Dover JS. Skin Deep. 3rd ed. New York: Checkmark Books. 2007</ref>  
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#Skin is made up of the Epidermis and the Dermis, each having separate sublayers&nbsp;<ref name="p5">Mclafferty E Hendry C Farley A. The integumentary system: anatomy, physiology and function of skin. Nursing Standard 2010;27:35-42.</ref>
#Skin is made up of the Epidermis and the Dermis, each having separate sublayers&nbsp;<ref name="p5">Mclafferty E Hendry C Farley A. The integumentary system: anatomy, physiology and function of skin. Nursing Standard 2010;27:35-42.</ref>
== General Function  ==
== General Function  ==
[[File:Integumentary system.jpg|right|frameless]]
[[File:Integumentary system.jpg|right|frameless|450x450px]]
The skin has several functions that provide several purposes<ref name="one">Martini FH, Nath, JL. Fundamentals of Anatomy and Physiology. 8th ed. Pearson. San Francisco: Benjamin Cummings. 2009</ref>&nbsp;;  
The skin has several functions that provide several purposes<ref name="one">Martini FH, Nath, JL. Fundamentals of Anatomy and Physiology. 8th ed. Pearson. San Francisco: Benjamin Cummings. 2009</ref>&nbsp;;  


*Protection- The skin is the first line of defense against foreign pathogens  
*Physical protection: The integumentary is the covering of the human body and its' most apparent function is physical protection. The skin itself is a tightly knit network of cells, with each layer contributing to its strength. The epidermis has an outermost layer created by layers of dead keratin that can withstand wear and tear of the outer environment, the dermis provides the epidermis with blood supply and has nerves that bring danger to attention amongst other functions, the hypodermis provides physical cushioning to any mechanical trauma through adipose storage, and the glands secrete protective films throughout the body. The nails protect the digits, which are prone to repeated trauma by creating a hard covering and hairs throughout the body filter harmful particles from entering the eyes, ears, nose, etc.
*Excretion- Of salt, water and waste products through glands  
*Immunity: The skin is the body’s first line of defense acting as a physical barrier preventing direct entry of pathogens. Antimicrobial peptides (AMPs) and lipids on the skin also act as a biomolecular barrier that disrupts bacterial membranes. An additional aspect of the skin’s immunity lies in the resident immune cells. Both myeloid and lymphoid cells are present in the skin, and some, such as the Langerhans cells or dermal dendritic cells, possess the capability to travel to the periphery and activate the greater [[Immune System|immune system]]<ref name=":0" />
*Thermoregulation- Via vasocontriction and vasodialtion mechanisms
*Excretion: Of salt, water and waste products through glands<ref name=":0" />
*Calcium Metabolism- Vitamin D3 and Calcitrol
*Thermoregulation: The skin has a large surface area that is highly vascularized, which allows it to conserve and release heat through vasoconstriction and vasodilation, respectively<ref name=":0" />.
*Fat Stroage&nbsp;  
*Vitamin D synthesis: The primary sources of vitamin D are sun exposure and oral intake. With ultraviolet sunlight exposure, 7-dehydrocholesterol converts to vitamin D3 in the skin, which is then hydroxylated in the liver then kidney into its active metabolite form, 1,25-dihydroxy vitamin D (calcitriol). This metabolite ultimately leads to increased calcium absorption in the gut and is crucial for bone health<ref name=":0" />.
*Sensation- Touch, pressure, pain, and temperature
*Fat Storage&nbsp;  
*Sensation- Skin innervation is by various types of sensory nerve endings that discriminate pain, temperature, touch, and vibration. Each type of receptor and nerve fiber varies in its adaptive and conductive speeds, leading to a wide range of signals that can be integrated to create an understanding of the external environment and help the body to react appropriately<ref name=":0" />.


If not working correctly, each of the functions can have important clinical implications and all should be considered when working with patients. For example an important clinical association with the breakdown of the ability of the skin to provide protection is [[Pressure Ulcers|pressure sores]].  
If not working correctly, each of the functions can have important clinical implications and all should be considered when working with patients. For example an important clinical association with the breakdown of the ability of the skin to provide protection is [[Pressure Ulcers|pressure sores]].  
== Structure of the Skin  ==
== Structure of the Skin  ==


[[Image:EpidermalLayersHistology.png|thumb|right|200x350px|Layers of the Skin]]
[[Image:Skinlayers.png|right|332x329px|A diagram Showing the Layers of the Epidermis|frameless]]The skin is made up of two layers—the superficial epidermis and the deeper dermis.
=== Epidermis  ===


The epidermis is composed of a series of layers containing stratified keratinised squamous epitelial cells and is the uppermost surfaces of the skin. The epidermis is avascular and relies upon the lower dermis (dermal layer) for oxygenation and metabolism&nbsp;<ref name="p3" />. There are 4 main types of cells within the epidermis<ref name="p3" />;
Epidermis:
 
* Tough, outer layer that acts as the first line of defense against the external environment
#'''Keratinocytes''' which make up 90% of the cells and is why skin is waterproof
* Regenerates from stem cells located in the basal layer that grow up towards the corneum. The epidermis itself is devoid of blood supply and derives its nutrition from the underlying dermis
#'''Melanocytes''' which make up 8% of the cells and are responsible for producing the skin pigment, melanin.
Composed of stratified squamous epithelial cells that further break down into four to five layers (see image R). From superficial to deep, the primary layers are the  
#'''Langerhans''' cells which make up 1% of the cells and are involved in the immune response
* Stratum corneum
#'''Merkel cells''' &nbsp;which make up 1% of the cells and function in the sensation of touch
* Stratum granulosum
 
* Stratum spinosum
The epidermis is made up of the following layers (from bottom to top);
* Stratum basale  
 
* In the palms and soles where the skin is thicker, there is an additional layer of skin between the stratum corneum and stratum granulosum called the stratum lucidum.  
#'''Stratum Basale''' (or Stratum Germinativum)
[[Image:EpidermalLayersHistology.png|thumb|right|200x350px|Layers of the Skin]]Dermis  
#'''Stratum Spinosum'''
* Underlying connective tissue framework that supports the epidermis
#'''Stratum Granulosum'''
* The dermis as a whole contains blood and lymph vessels, nerves, sweat glands, hair follicles, and various other structures embedded within the connective tissue.
#'''Stratum Lucidum'''
Further subdivides into two layers
#'''Stratum Corneum'''
* Superficial papillary dermis -  forms finger-like projections into the epidermis, known as dermal papillae, and consists of highly vascularized, loose connective tissue.  
 
* Deep reticular layer -  has dense connective tissue that forms a strong network<ref name=":0" />. 
[[Image:Skinlayers.png|frame|right|332x329px|A diagram Showing the Layers of the Epidermis]]As the skin matures, the layers progress to the surface and are a clear, visible example of the effects of cell maturation and aging until they are finally shed.<br>
==== Stratum Basale  ====
 
This is deepest layer layer of the epidermis and is made up of a single row of columnar keratinocytes along with melanocytes and markel cells. The basale is the only layer within the epidermis which is able to divide through mitosis. It is the keratinocytes which undergo this mitosis, producing two daughter cells, one of which remains in the basale and the other migrates and matures to the surface progressing through the layers in a process which takes up to 28 days&nbsp;<ref name="p3" />. As the stratum basale is the closest layer to the dermis and therefore blood and nutrient supply, as the daughter cells mature and move away from this layer, they recieve less nutrition and subsequnelty die. Additionally the cells become more keratinised as they mature as they accumulate more of the fibrous protein keratin meaning they become more capable of protection as they mature. In healthy skin the balance of cells of formation and matration of cells is in balance&nbsp;<ref name="p3" />.<br>
 
==== Stratum Spinosum  ====
 
As one of the daughter cells, produced by the stratum basale, mature and progress to this layer they cannot divide and also become rounded and spikier (hence the name spinosum). This layer is 5-12 cells thick and the cells are connected by intercellular bridges called desmosomes and as the cells progress through the layers these connections are continually being broken and reformed <ref name="pringle">Pringle F, Penzer R. Normal Skin: its function and care. In: Penzer, R editor. Nursing Care of the Skin. Oxford: Butterworth Heinemann, 2002. p20-45.</ref>. These connections have a thorn like projections which draw cells together, contributing to the tensile strength and elasticity of the skin&nbsp;<ref name="Thibo">Thibodeau GA, Patton KT. Structure and Function of the Body. 14th ed. Missouri: Mosby. 2012.</ref>.
 
==== Stratum Granulosum&nbsp;  ====
 
After passing through the basale and spinosum, the cells then reach the granulosum. As they progress to this layer they become longer and flattened to form the 3-5 cells thick granulosum. In this layers the cells undergo apoptosis and are unable to form any metabolic function and as the cells lose their nuclues they become keratinised and are completely made of karatin&nbsp;<ref name="One">Martini FH, Nath, JL. Fundamentals of Anatomy and Physiology. 8th ed. Pearson. San Francisco: Benjamin Cummings. 2009</ref>.&nbsp;At the transition between this layer and the stratum corneum, cells secrete lamellar bodies (containing lipids and proteins) into the extracellular space. This results in the formation of the hydrophobic lipid envelope responsible for the skin's barrier properties <ref name="Ovaere">Ovaere P, Lippens S, Vandenabeele P, Declercq W. The emerging roles of serine protease cascades in the epidermis. Trends in Biochemical Sciences. 34: 2009;453–463</ref>.&nbsp;
 
==== Stratum Lucidum  ====
 
This layer is only found on areas of the body which have high levels of wear and pressure and is needed to be thick such as palms and heels. The lucidum is made up of 3-5 layers of clear, dead keratinocytes which are flattened and highly durable and also has a 'glassy' clear appearance&nbsp;<ref name="p5" />.
 
==== Stratum Corneum  ====
 
This is the '''cast off layer''' as this is the uppermost layer of the skin and consists of 25-30 layers of flat, dead keratinocytes and has a thickness between 10 and 40 μm.&nbsp;These cells are arranged in vertical stacks which are firmly connected to each other by a lipid (sort of cell cement) created in the stratum granulosum . As the cells move through the corneum they become less sticky and are shed in lumps known as '''squamae '''in a process known as&nbsp;'''desquamation'''&nbsp;<ref name="p5" />. The thickness of the stratum corneum varies throughout the body. In the palms of the hands and the soles of the feet this layer is typically thicker, since these regions require additional protection in order to grasp objects and avoid injury. If the skin is exposed to constant or high levels of friction, then it is the stratum corneum which adapts and forms a hard callus and this demonstrates this layers primary function of protection.&nbsp;
 
=== Dermis ===
 
The dermis lies beneath the epidermis and above the subcutaneous fat layer and, as mentioned above, is responsible for providing nutrients and blood supply to the epidermis&nbsp;<ref name="Burr">Burr S, Penzer R. Promoting Skin Health.Nursing Standard. 2005; 19: 57-65.</ref>. The dermis contains all of the appendages such as the lymph vessels, nerve endings, hair follicles and glands&nbsp;<ref name="pringle" />. The dermis is anchored to the epidermis by rete ridges (furrows) created by hemidesmosomes, which stabilise the surfaces and allow transfer of nutrients between the layers&nbsp;<ref name="Turkington">Turkington C, Dover JS. Skin Deep. 3rd ed. New York: Checkmark Books. 2007.</ref>. If there is a shearing force or a high level of friction on these ridges and between the two layers, the two layers may become separated and fluid allowed to collect in the space forming a blister.
 
The dermis is made up of two layers called the '''''reticular''''' and '''''papillary''''' layers. the papillary layer contains nerves and capillaries whilst the reticular layer is comprised of the strong connective tissue collagen<ref name="Pringle">Pringle F, Penzer R. Normal Skin: its function and care. In: Penzer, R editor. Nursing Care of the Skin. Oxford: Butterworth Heinemann. 2002;20-45</ref>. &nbsp;


== Links to other Areas or Topics to Consider  ==
== Links to other Areas or Topics to Consider  ==

Revision as of 07:52, 23 October 2020

Original Editor - Scott Buxton

Top Contributors - Scott Buxton, Lucinda hampton, Wendy Walker, Admin, Kim Jackson, WikiSysop, Joao Costa, 127.0.0.1 and Vidya Acharya  

The Integumentary System[edit | edit source]

Skin blank.jpg

The integumentary system is the largest organ of the body that forms a physical barrier between the external environment and the internal environment that it serves to protect and maintain.

The integumentary system includes

  • Skin (epidermis, dermis)
  • Hypodermis,
  • Associated glands,
  • Hair
  • Nails.

In addition to its barrier function, this system performs many intricate functions such as body temperature regulation, cell fluid maintenance, synthesis of Vitamin D, and detection of stimuli. The various components of this system work in conjunction to carry out these functions[1].

An Introduction - Key Facts[edit | edit source]

  1. Skin accounts for about 16% of your total body weight [2]
  2. Its surface area covers between 1.5-2m2 [2]
  3. Weighs approximately 3-5kg [3]
  4. Is generally 1-2mm thick, but varies depending on its function, 0.5mm on eyelids but 3.4mm on soles of your feet [4]
  5. It is your body's first line of defence [2]
  6. The system contains all of the appendages including hair, nails, sebaceous glands and sweat glands[5]
  7. Skin is made up of the Epidermis and the Dermis, each having separate sublayers [6]

General Function[edit | edit source]

Integumentary system.jpg

The skin has several functions that provide several purposes[7] ;

  • Physical protection: The integumentary is the covering of the human body and its' most apparent function is physical protection. The skin itself is a tightly knit network of cells, with each layer contributing to its strength. The epidermis has an outermost layer created by layers of dead keratin that can withstand wear and tear of the outer environment, the dermis provides the epidermis with blood supply and has nerves that bring danger to attention amongst other functions, the hypodermis provides physical cushioning to any mechanical trauma through adipose storage, and the glands secrete protective films throughout the body. The nails protect the digits, which are prone to repeated trauma by creating a hard covering and hairs throughout the body filter harmful particles from entering the eyes, ears, nose, etc.
  • Immunity: The skin is the body’s first line of defense acting as a physical barrier preventing direct entry of pathogens. Antimicrobial peptides (AMPs) and lipids on the skin also act as a biomolecular barrier that disrupts bacterial membranes. An additional aspect of the skin’s immunity lies in the resident immune cells. Both myeloid and lymphoid cells are present in the skin, and some, such as the Langerhans cells or dermal dendritic cells, possess the capability to travel to the periphery and activate the greater immune system[1]
  • Excretion: Of salt, water and waste products through glands[1]
  • Thermoregulation: The skin has a large surface area that is highly vascularized, which allows it to conserve and release heat through vasoconstriction and vasodilation, respectively[1].
  • Vitamin D synthesis: The primary sources of vitamin D are sun exposure and oral intake. With ultraviolet sunlight exposure, 7-dehydrocholesterol converts to vitamin D3 in the skin, which is then hydroxylated in the liver then kidney into its active metabolite form, 1,25-dihydroxy vitamin D (calcitriol). This metabolite ultimately leads to increased calcium absorption in the gut and is crucial for bone health[1].
  • Fat Storage 
  • Sensation- Skin innervation is by various types of sensory nerve endings that discriminate pain, temperature, touch, and vibration. Each type of receptor and nerve fiber varies in its adaptive and conductive speeds, leading to a wide range of signals that can be integrated to create an understanding of the external environment and help the body to react appropriately[1].

If not working correctly, each of the functions can have important clinical implications and all should be considered when working with patients. For example an important clinical association with the breakdown of the ability of the skin to provide protection is pressure sores.

Structure of the Skin[edit | edit source]

A diagram Showing the Layers of the Epidermis

The skin is made up of two layers—the superficial epidermis and the deeper dermis.

Epidermis:

  • Tough, outer layer that acts as the first line of defense against the external environment
  • Regenerates from stem cells located in the basal layer that grow up towards the corneum. The epidermis itself is devoid of blood supply and derives its nutrition from the underlying dermis

Composed of stratified squamous epithelial cells that further break down into four to five layers (see image R). From superficial to deep, the primary layers are the

  • Stratum corneum
  • Stratum granulosum
  • Stratum spinosum
  • Stratum basale
  • In the palms and soles where the skin is thicker, there is an additional layer of skin between the stratum corneum and stratum granulosum called the stratum lucidum.
Layers of the Skin

Dermis

  • Underlying connective tissue framework that supports the epidermis
  • The dermis as a whole contains blood and lymph vessels, nerves, sweat glands, hair follicles, and various other structures embedded within the connective tissue.

Further subdivides into two layers

  • Superficial papillary dermis - forms finger-like projections into the epidermis, known as dermal papillae, and consists of highly vascularized, loose connective tissue.
  • Deep reticular layer - has dense connective tissue that forms a strong network[1]. 

Links to other Areas or Topics to Consider[edit | edit source]

Other Resources[edit | edit source]

References[edit | edit source]

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Kim JY, Dao H. Physiology, Integument. InStatPearls [Internet] 2020 Feb 17. StatPearls Publishing.Available from:https://www.ncbi.nlm.nih.gov/books/NBK554386/ (last accessed 23.10.2020)
  2. ↑ 2.0 2.1 2.2 Martini FH, Nath, JL. Fundamentals of Anatomy and Physiology. 8th ed. Pearson. San Francisco: Benjamin Cummings. 2009
  3. ↑ Turkington C, Dover JS. Skin Deep. 3rd ed. New York: Checkmark Books. 2007
  4. ↑ Tortora GJ, Derrickson BH. Principles of Anatomy and Physiology: Organisation, Support and Movement and Control Systems of the Human Body. Volume 1. 12th ed. Hoboken: John Wiley and Sons. 2009
  5. ↑ National Library of Medicine. Medical Subject Headings (MESH) http://www.nlm.nih.gov/cgi/mesh/2011/MB_cgi?modeterm=Integumentary+System (accessed 11 June 2013)
  6. ↑ Mclafferty E Hendry C Farley A. The integumentary system: anatomy, physiology and function of skin. Nursing Standard 2010;27:35-42.
  7. ↑ Martini FH, Nath, JL. Fundamentals of Anatomy and Physiology. 8th ed. Pearson. San Francisco: Benjamin Cummings. 2009


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