Skin Functions and Layers

8/12/2019 Skin Functions and Layers

1/23

Skin functions and Layers

Some facts about skin

Skin is the largest organ of the body. It has an area of 2 square metres (22 square feet) in adults, and weighs about 5 kilograms.

The thickness of skin aries from !.5mm thick on the eyelids to ".!mm thick on the heels

of your feet.

Skin is the ma#or barrier between the inside and outside of your body$

Functions of skin

%. Protection& it 'rotects against light, mechanical, thermal and chemical stresses,

dehydration and inasion by micro*organisms.2. Sensation& skin has rece'tors that sense touch, 'ressure, 'ain and tem'erature.

+. Thermoregulation& arious features of the skin are inoled in regulating tem'erature of

the body. or e-am'le sweat glands, hair, and adi'ose tissue.

". Metabolic functions& subcutaneous adi'ose tissue is inoled in 'roduction of itamin, and triglycerides.

This diagram shows the layers found in skin. There are three main layers& the epidermis, dermisand hypodermis. There are also sweat glands, and hairs, which hae sebaceous glands, and a

smooth muscle called the arrector 'ili muscle, associated with them.


2/23

/airs are only found in thin skin, and not in the thick skin 'resent on the fingerti's, 'alms and

soles of your feet. ind out moreabout hair.

Three layers of skin:

The epidermis& a thin outer 'ortion, that is the keratinised stratified squamous e'ithelium ofskin. The e'idermis is im'ortant for the 'rotectie function of skin. The basal layers of this

e'ithelium are folded to form dermal 'a'illae. Thin skin contains four ty'es of cellular layers,

and thick skin contains fie. 0lick hereto find out more about the e'idermis and its layers.

Thedermis: a thicker inner 'ortion. This is the connectie tissue layer of skin. It is im'ortant for

sensation, 'rotection and thermoregulation. It contains neres, the blood su''ly, fibroblasts, etc,

as well as sweat glands, which o'en out onto the surface of the skin, and in some regions, hair.The a'ical layers of the dermis are folded, to form dermal 'a'illae, which are 'articularly

'rominent in thick skin.

The hypodermis. This layer is underneath the dermis, and merges with it. It mainly containsadi'ose tissue and sweat glands. The adi'ose tissue has metabolic functions& it is resonsible for'roduction of itamin , and triglycerides.

This is an /1 section of thick skin. The outer layers of skin are towards the to'. See if you canidentify the e'idermis, dermis, dermal 'a'illae and sweat glands. 3otice that there are no hairs in

this region.

Dermal Papillae

The 'hotogra'h o''osite shows a section through thick skin. Thick skin like this is only found in

areas where there is a lot of abrasion * such as 'alms, fingerti's, and soles of your feet. 4hy do

you think this is
http://www.histology.leeds.ac.uk/skin/hair.phphttp://www.histology.leeds.ac.uk/skin/epidermis_layers.phphttp://www.histology.leeds.ac.uk/skin/epidermis_layers.phphttp://www.histology.leeds.ac.uk/skin/hair.php


3/23

6ou should notice that the dermis e-tends u' into the e'idermis in structures called dermal

'a'illae. These hae two functions.

irst, they hel' adhesion between the dermal and e'idermal layers.

Second, in areas of thick skin like this, they 'roide a large surface area, to nourish the e'idermallayer.

on7t forget the e'idermis is a stratified squamous e'ithelium, so it does not hae its own blood

su''ly. It relies solely on the blood su''ly from the dermis.

The Dermis and Hypodermis

The dermisis a connectie tissue layer, that contains collagen and elastin fibres, and fibroblasts,

macro'hages and adi'ocytes, as well as neres, glands and hair follicles. The dermis is tough,

and is the layer used to make leather.

It can be diided into two regions&

superficial region* ('a'illary dermis) the region around the dermal 'a'illae, which makes u'around 2!8 of the dermis. This layer contains loose connectie tissue, and it has many

ca'illaries. It e-tends u' into the e'idermis in small 'ro#ections called dermal 'a'illae. This

region also contains 9eissners cor'uscles, which are touch rece'tors, as well as free nereendings (non*myelinated) that are sensitie to tem'erature.

deeper region * (reticular dermis) this is a layer of dense irregular connectie tissue, which

contains collagen and elastin, which gie skin its strength and e-tensibility. The collagen bundles

are woen into a coarse network. This layer contains fibroblasts, macro'hages and fat cells.

The sweat glandsare found dee' in this region and in the hy'odermis.

0an you see the two regions of the dermis in the 'icture aboe

The hypodermislies under the dermis, and mainly contains adi'ose tissue.


4/23

This diagram shows the blood su''ly of skin.

The circulation of skinThe arteries su''lying the skin are dee' in the hy'dermis. :ranches from the arteries 'ass

u'wards to form a dee' and a su'erficial 'le-us.

The dee' cutaneous pleusis at the dermal;hy'odermal #unction. It su''lies the fatty tissue ofthe hy'odermis, and the dee'er 'arts of the dermis, including the ca'illaries for hair follicles,

dee' sebaceous glands and sweat glands.

The su'erficial subpapillary pleuslies #ust beneath the dermal 'a'illae, and su''lies theca'illaries in the dermal 'a'illae. The 'ink colour of skin is mainly due to the blood seen in

enules of this 'le-us.

There are many arterioenous anastomoses in the dermis, which can 'reent blood from entering

the su'erficial cutaneous 'le-us. This strategy is used as a res'onse to cold as a way ofconsering heat. The danger is that if the e'idermis loses its blood su''ly for too long, it will die

(frostbite$).


5/23

Thick and thin skin

This is a 'icture of an /1 stained section of the e'idermis of thin skin.

There are only four layers in the e'idermis of thin skin. The stratum lucidum layer is absent.

4hat do you notice about thicknesses of the different layers

/ow 'ronounced are the dermal 'a'illae com'ared to thick skin

Dermis: Thin skin actually has a thicker dermis than thick skin, which makes thin skin easier to

suture, if it gets damaged. Thin skin also has fewer eccrine;merocrine sweat glands.

This is a 'icture of an /1 stained section of the e'idermis ofthick skin!

0an you identify the fie ma#or layers of the e'idermis

Dermis: Thick skin has a thinner dermis than thin skin, and does not contain hairs, sebaceous

glands, or a'ocrine sweat glands.

Thick skin is only found in areas where there is a lot of abrasion * fingerti's, 'alms and the solesof your feet.

This is a 'icture of a diseased skin * a ery commoncondition * can you tell what it is


6/23

(/int, witches or wi=ards will charm them away for you$)

http://www.histology.leeds.ac.uk/index.php

PIGMENTATION

Skin Pigmentation

This shows two melanocytes in the basal layer of skin. 6ou can also see how the 'rickle cells in

the stratum s'inosum layers, a''ear to hae a eil of melanin oer the nucleus.

"#erall skin colour depends on:

%. 0arotene 'igments in subcutaneous fat (adi'ose tissue) (orange*yellow colour).

2.


7/23

' to >8 (% in eery 5 to %! cells) in the e'idermis is a melanocyte(melano means black) make

u' >8 of the e'idermal cells.

9elanocytes make the 'igment called melanin. Tyrosine is conerted intodihydro-y'henylalanine (?@


8/23

Glands

Three types of glands

$ccrine%merocrine Sweat &lands

This shows a 'hoto of the secretory portionofthe sweat glands at higher magnification. The

secretory 'arts are lined by sim'le cuboidal

e'ithelium. The ducts are lined by stratified (2layers) cuboidal e'ithelium. Aong thin

myoe'ithelial cells are arranged helically around

the 'eri'hery between the secretory cells and theirbasement membrane. 4hen they contract, more

sweat is 'roduced (i.e. in fear, an-iety or stress *

you will get sweaty 'alms$).


9/23

The sweat glands are sim'le tubular e-ocrineglands that are found in the su'erficial hy'odermis

bordering on the dermis. They discharge their contents onto the surface of the skin ia coiled

secretory ducts (see the diagram o''osite). The ducts o'en out onto e'idermal ridges at a sweat'ore. They can be further classified as merocrine (eccrine) glands. They secrete a watery fluid

which is hy'otonic to 'lasma. Its ea'oration is im'ortant for thermoregulation. Sweat contains

water, sodium, 'otassium, chloride, urea ammonia and lactic acid.

This diagram shows the main features of a hair, and its associated sweat gland.
http://www.histology.leeds.ac.uk/tissue_types/epithelia/epi_exocr_types.phphttp://www.histology.leeds.ac.uk/tissue_types/epithelia/epi_exocr_types.phphttp://www.histology.leeds.ac.uk/tissue_types/epithelia/epi_exocr_types.phphttp://www.histology.leeds.ac.uk/tissue_types/epithelia/epi_exocr_types.phphttp://www.histology.leeds.ac.uk/tissue_types/epithelia/epi_exocr_types.php


10/23

Take a look at this sebaceous gland. 0an you identify the sebaceous gland and duct, the hair,

arrector 'ili muscle, and the IBS and BS (internal and e-ternal root sheaths) of the hair

3otice the changes in the BS and IBS near the duct, the cells of the sebaceous glanddisintegrate near the duct, and the duct o'ens out u'wards onto the hair.

Sebaceous &lands

Sebaceous glands are branched acinar (s'herical) glands which make an oily substance called

sebum. The rounded cells are filled with li'id filled acuoles, and towards the end of the duct,the cells degenerate to release their contents into the duct * /?A?0BI3 secretion. This oil

coats hair and the surface of thin skin to hel' kee' it soft, su''le and water'roof.


11/23

Reticular dermis

The reticular layer of the dermis ((D) consists of dense irregular connectie tissue,which differs from the 'a'illary layer (PD), which is made u' of mainly loose

connectie tissue (note the difference in the number of cells). The reticular layer of

the dermis is im'ortant in giing the skin it oerall strength and elasticity, as well as

housing other im'ortant e'ithelial deried structures such as glands and hair follicles.

Skin Appendages


12/23

Skin Appendages

The skin contains a !a"iety o# appendages$ %ainly hai" #ollicles&HF'$ sweatglands$ and se(aceous glands&SG'$ which a"e all e%("ylogically epide"%al ino"igin.

)ason *. +wanson and )e##"ey ,. Melton$ M.-.http://www.%eddean.luc.edu/lu%en/MedEd/%edicine/de"%atology/%elton/title.ht%htt'&;;www.lumen.luc.edu;inde-.htmll
http://www.meddean.luc.edu/lumen/MedEd/medicine/dermatology/melton/skinlsn/hairfol.htmhttp://www.meddean.luc.edu/lumen/MedEd/medicine/dermatology/melton/skinlsn/sweatgl.htmhttp://www.meddean.luc.edu/lumen/MedEd/medicine/dermatology/melton/skinlsn/sweatgl.htmhttp://www.meddean.luc.edu/lumen/MedEd/medicine/dermatology/melton/skinlsn/sebgl.htmhttp://www.meddean.luc.edu/lumen/MedEd/medicine/dermatology/melton/title.htmhttp://www.meddean.luc.edu/lumen/MedEd/medicine/dermatology/melton/title.htmhttp://www.lumen.luc.edu/index.htmllhttp://www.meddean.luc.edu/lumen/MedEd/medicine/dermatology/melton/skinlsn/hairfol.htmhttp://www.meddean.luc.edu/lumen/MedEd/medicine/dermatology/melton/skinlsn/sweatgl.htmhttp://www.meddean.luc.edu/lumen/MedEd/medicine/dermatology/melton/skinlsn/sweatgl.htmhttp://www.meddean.luc.edu/lumen/MedEd/medicine/dermatology/melton/skinlsn/sebgl.htmhttp://www.meddean.luc.edu/lumen/MedEd/medicine/dermatology/melton/title.htmhttp://www.meddean.luc.edu/lumen/MedEd/medicine/dermatology/melton/title.htmhttp://www.lumen.luc.edu/index.htmll


13/23

Skin structure

The skin is the largest human organ. It coers between %.5 and 2 m2, com'rising about one si-th

of total body weight.

The skin consists of three functional layers&

$pidermis

Dermisor corium

Subcutis(hy'odermis)

In these layers are found the e'idermal a''endages& nails, hair and glands. The skin'erforms arious functions such as tem'erature regulation and insulation, energy storage,

sensory 'erce'tion and 'rotection from enironmental influences such as fungi, bacteria and

() radiation. Sebaceous and sweat glands belong to the e-ocrine glands. Sebaceous glandsare nearly always connected to hair follicles. Sweat glands delier their secretions directly to the

skin surface.

% 'idermis

2 ermis

+ Subcutis

" /air follicle

5 Sebaceous gland

E Sweat gland


14/23

http://www.eucerin.co.uk/links/index.html

SUMMARY

The skin consists of three functional layers:

Epidermis

Dermis or coriumSubcutis (hpodermis)

The epidermis is divided into 5 layers. The basal layer (stratum basale) contains thebasal or mother cells that ensure continual regeneration of the skin through cell division(proliferation). Above lie the cells of the prickle cell layer (stratum spinosum). Next comethe granular clear and horny layers (stratum granulosum lucidium and corneum) in thatorder. The horny layer consists of !5 " #$ cell layers that together %ith the epidermallipids form the permeability barrier. This performs t%o important functions:

&t hinders the invasion of certain substances such as microorganisms chemical

irritants and allergens.

&t minimi'es transepidermal %ater loss (T*) and so is of great importance to thebody.

The dermisis divided into t%o layers the stratum papillare forming the distinctundulated border %ith the epidermis and the stratum reticulare %hich continuallymerges into the subcutis. The main constituents of the dermis are the proteinousconnective tissue fibres %hich are connected to the glycosaminoglycans ormucopolysaccharides.

The epiderm!l !ppend!"esinclude the nails hair and skin glands (glandulae cutis).specially the s%eat and sebaceous glands play an important role in formation of thehydrolipid film.

The subcutisserves foremost as the energy reservoir of the skin: here nutrients in theform of li+uid fats are stored in the adipocytes. At the same time the subcutis providesinsulation and shock absorption.


15/23

Body Part -Merkel cell

Part type : pa"t

On both sides :

Digitisation

completed :

#als

e

Structure

9erkel cells are 'resent in small numbers in the stratum basale, or the dee'est layer, of the

e'idermis. They are located near areas of well*ascularised, richly innerated connectietissue. ach 9erkel cell is intimately associated with an afferent nere terminal, forming astructure known as a 9erkel cell*neuron com'le-, or a 9erkel disc. 9erkel cells 'ossess

desmosomes and keratin filaments, which suggests that they may hae an e'ithelial origin.

Their structure is characteristic of transducer sensory cells that act as intermediates betweenan initial stimulus and the afferent neuron im'ulse. They contain& 'ro#ecting microillF

granules containing neurotransmittersF and syna'ses with their associated neurons.

Function

9erkel cells are 'resent in small numbers in the stratum basale, or the dee'est layer, of the

e'idermis. They are located near areas of well*ascularised, richly innerated connectie tissue.

ach 9erkel cell is intimately associated with an afferent nere terminal, forming a structureknown as a 9erkel cell*neuron com'le-, or a 9erkel disc. This functions as a sensory

mechanorece'tor in the e'idermis. 9erkel cell structure is characteristic of transducer sensory

cells that act as intermediates between an initial stimulus and the afferent neuron im'ulse.eformation of the microilli stimulates neurotransmitter release by granule e-ocytosis at the

syna'se. This then stimulates the associated afferent neuron. This chemical syna'se actiity is

belieed to be too slow for 9erkel cells to be the 'rimary transducer, but 9erkel cells may

modify the neuron7s res'onse by affecting the threshold of res'onse.


16/23

A single strand of hair is made up of several components:-

The hair shaft: The visible part of the hair is dead. It gros from the narro tube belo the

surface of the scalp hich is called a follicle.

The hair follicle: !sac"- is the portion of hair belo the s#in$s surface% is a single structure

hich lives and gros at an average rate of &-' centimeters !&() to &*" per month.

At the base of hair follicle lie papilla% hich eventually form hair.

Sebaceous glands: +e,t to each follicle produce natural oil that #eeps the hair lubricated

and shiny.

The hair e,tends through epidermis into the dermis% from here it receives its blood supply

and sensitivity.


17/23

air groth cycles

or 'ro'er and successful hair remoal, a 'erson must know the cycles of hair growth, tounderstand why there may be re*growth in a cou'le of days after hair remoal.

It must be noted that hair growth can differ greatly from one 'erson to the ne-t * but the same

'hysiology of hair growth is followed by all healthy 'eo'le.

)hen waing should be done

If you wish to follow the 'erfect way to 'lan your hair remoal, wa-ing should be done in the

following manner&

In month one, you should wa- on day %, day %5 and day +!.

Thereafter you should wa- monthly for fie months and then in your seenth month you willagain re'eat the first cycleF days %, day %5 and day +!, followed again with monthly wa-ing.


18/23

Telogen

The time it takes to com'lete this three*'art cycle aries according to the site at which the hair

grows.

The difference in cycle times aries dramatically from one area to the other as mentioned aboe *for hair found on the scal' the anagen 'hase duration is on aerage three to four years (but can in

some cases be as long as nine years) with the catagen 'hase taking about two to three weeks and

the telogen 'hase being about three months.

0om'aring the times aboe, it is interesting to note that hair found on other body sites is ty'ifiedby much longer telogen 'hases (can take u' to nine months) and shorter anagen 'eriods (being

from four to seen months). /oweer the catagen 'hase normally remains ery constant ranging

from three to four weeks.

:ut to confuse the matter een more * eyelashes can com'lete the three*'art cycle in

a''ro-imately four months.

The hair growth cycles in humans are not synchroni=ed * as in some animals where a winter coat

is shed * and all three 'hases can be 'resent at any 'articular area under reiew.

In facial and body hair, where a 'erson is looking at hair remoal, the cycles 'lay an im'ortantrole and the timing should be well 'lanned.

The hair bulb 'osition also aries according to the 'hase it is in * anagen hair bulbs are located in

the subcutaneous fat, while catagen bulbs are found in the dermis, and the telogen bulbs are

located in the mid*to*u''er dermis.

'nagen

The anagen cycle of hair growth is the growing 'hase and this 'eriod for facial and body hair

may be as long as two to three weeks.

The anagen cycle can be subdiided into three sub*cycles * that being&

@roanagen

9esanagen

9etanagen

The 'roanagen stage marks the initiation of hair growth but then ra'idly 'rogresses through to

the mesanagen and to the metanagen stage.

*atagen
http://www.dermaxime.com/growth-cycles-hair.htm#Telogenhttp://www.dermaxime.com/growth-cycles-hair.htm#Hair%20growth%20cycleshttp://www.dermaxime.com/growth-cycles-hair.htm#Hair%20growth%20cycleshttp://www.dermaxime.com/growth-cycles-hair.htm#Telogen


19/23

This cycle is a 'eriod of regression or transition, and the hair is getting ready to shed.

4hen the hair enters the catagen 'hase the dermal 'a'illa condenses with the cells becoming

inactie. 4ithout dermal 'a'illa cell stimulation the hair fibers, as well as the root sheaths sto'growing.

Telogen

uring this cycle the hair rests and no growth is e-'erienced.

4hen entering the telogen 'hase, the dermal 'a'illa becomes isolated in the dermis and the hair

fiber is easily 'ulled out when washing or combing. 4hen the hair goes from the telogen toanagen (growing) 'hase, and the old hair fiber has not fallen out, it will be 'ushed out by the new

hair fiber growing underneath.

4e ho'e that this short e-'lanation on hair growth cycles gies you a better idea why re'eated

hair remoal has to be undertaken to achiee a smooth hairless body.

htt'&;;www.derma-ime.com;inde-.htm

*hris Harthttp:%%www!northernconcord!org!uk%hair+,!-pg
http://www.dermaxime.com/index.htmhttp://www.dermaxime.com/growth-cycles-hair.htm#Hair%20growth%20cycleshttp://www.dermaxime.com/index.htm


20/23

htt'&;;www.medgadget.com;archies;img;langerhansGcell.gif

htt'&;;www.marla*schnee*cosmetics.de;information;studien*fachartikel;images;hair*remoal*2*

%.#'g
http://www.marla-schnee-cosmetics.de/information/studien-fachartikel/images/hair-removal-2-1.jpghttp://www.marla-schnee-cosmetics.de/information/studien-fachartikel/images/hair-removal-2-1.jpghttp://www.marla-schnee-cosmetics.de/information/studien-fachartikel/images/hair-removal-2-1.jpghttp://www.marla-schnee-cosmetics.de/information/studien-fachartikel/images/hair-removal-2-1.jpg


21/23

htt'&;;www.ayurhel'.com;images;hair2.#'g
http://www.ayurhelp.com/images/hair2.jpghttp://www.ayurhelp.com/images/hair2.jpg


22/23

Merkel cell at the base of the skin (toe, rato" unla(elled o"iginal i%age click he"e$ please'

!01ytoplas%a&2ell#l3ssigkeit %it O"ganellen'4 "c0 Euch"o%atin4 "l05i("a elastica&elastische 5ase"'4G0 GolgiAppa"at4 Hc0 6ete"och"o%atin4 Hd0 6e%ides%oso%en4 #f 0 Inte"%edi7"#ila%ente&hie" 8e"atin#ila%ente'4$e0 8e"atinocyten &Epithel9ellen de" 6aut'4 $o0 8ollagen#i("illen&Typ und ;'4 %b0,a%ina(asalis&


23/23

Sba0 +t"atu% (asale &unte"ste 2ellschicht de" 6aut4 hie" liegt auch die Me"kel2elle'4Spi 0 +patiu% inte"cellula"e&2wischen9ell"au%$ de" haupts7chlich >asse" enth7lt'4Spn0 +patiu% pe"inuclea"epe"inucle7"e" *au% &Innen"au% de" 8e"nh3lle4 hie" 9u% Teil sta"ke"weite"t'4*s 0 ?esicula sec"eti&+ek"et!esikel$ die +e"otonin als Neu"ot"ans%itte" enthalten und wegenih"es elekt"onendichten 2ent"u%s

auch denseco"e ?esikel genannt we"den'.
http://www.uni-mainz.de/FB/Medizin/Anatomie/workshop/EM/EMHaut.htmlhttp://www.uni-mainz.de/FB/Medizin/Anatomie/workshop/EM/EMIZR.htmlhttp://www.uni-mainz.de/FB/Medizin/Anatomie/workshop/EM/EMKernmembran.htmlhttp://www.uni-mainz.de/FB/Medizin/Anatomie/workshop/EM/EMKernmembran.htmlhttp://www.uni-mainz.de/FB/Medizin/Anatomie/workshop/EM/EMSekret.htmlhttp://www.uni-mainz.de/FB/Medizin/Anatomie/workshop/EM/EMHaut.htmlhttp://www.uni-mainz.de/FB/Medizin/Anatomie/workshop/EM/EMIZR.htmlhttp://www.uni-mainz.de/FB/Medizin/Anatomie/workshop/EM/EMKernmembran.htmlhttp://www.uni-mainz.de/FB/Medizin/Anatomie/workshop/EM/EMSekret.html

Skin Functions and Layers

Documents

Transcript of Skin Functions and Layers