L1-SKIN-Science of Epidermis, Dermis and Subdemis(Histology and molecular biology of the Skin).ppt

The Integumentary system includes:

1. Skin (Cutis or Derma or Integument)

2. Appendages of the skin
Hair
Sebaceous glands
Sweat glands
Nails
Arrectores pilorum muscle

1. PPT Presentation by:
DR G RAVINDRANATH MBBS; MS
Professor of Anatomy
E-mail: [email protected]
1
All the information, including the images and pics collected from
different sources is strictly for teaching purposes only.
Science of Epidermis, Dermis and Subdemis-1
(Histology and molecular biology of the Skin)

2. TheIntegumentarysystem includes:
1. Skin (Cutis or Derma or Integument)
2. Appendages of the skin
–Hair
–Sebaceous glands
–Sweat glands
–Nails
–Arrectores pilorum muscle
Skin is an organ -because it consists of different tissues that
are joined to perform a specific function.

3. Deep(underlying) to the skin is hypodermis ( sub dermis or subcutaneous tissue
or superficial fascia).

4. Note the appendages of the Skin

5. Identify the appendages of the
Skin

6. 1. The Skin (Derma, Cutis or Integument)
It is the largest organ (4-10kg) of the body(~
16%of total body mass)
Total surface area of skin is about 1.7 –2 m²
in adults.
The skin-thickness(epidermis + dermis) varies
between 1.5 mm and 4mm.
Dermatology is the medical specialty
concerning with diagnosing and
treatment of skin disorders.

7. The rule of nine of Wallace
•Head and neck -9%
•Each upper limb-9%
•Front of the trunk-18%
•Back of the trunk -18%
•Each lower limb-18%
•Perineum - 1%

8. Skin
Theskin(orcutis)coverstheentireexternalsurfaceofthe
body,includingtheexternalacousticmeatusandtympanic
membrane.
Itiscontinuousatthemuco-cutaneousjunctionswith
themucosaofthealimentary,respiratoryandgenito-
urinarytracts.
Atthemarginsoftheeye-lidsitblendswiththe
conjunctivaandatthepunctalacrimaliawiththelining
epitheliumoflacrimalcanaliculi.

9. Structurally skin is composed of
the epidermis-an epithelial layer
of ectodermal origin, and the
dermis-a layer of mesodermal
connective tissue.
At the junction between the
dermis and epidermis, projections
called dermal papillae interdigitate
with invaginating epidermal ridges
to strengthen adhesion of the two
layers.
Integument(Skin)
These dermo-epidermal interdigitations are of the peg-and socket variety in
most skin but in the thick skin of the palms and soles, they occur as well-
formed ridges and grooves which are unique for each individual( form
distinctive patterns), appearing as combinations of loops, arches, and whorls,
called dermatoglyphs, also known as fingerprints and footprints

11. Fingerprints
Fingerprints are impressions left on surfaces by the friction ridges.A friction ridge is a
raised portion of the epidermison the hand (palm and fingers) or sole of the foot

12. The basal layer of the epidermis of friction skin(palm, sole, digits) has a series of folds
protruding into the dermis, which correspond to the ridges and furrows on the outer
surface of the epidermis. The ridges or folds of the basal layer containing ducts from
the eccrine sweat glands of volar skin are termed primary ridges andcorrespond to
the surface ridges of friction skin. Secondary ridges, alternating between primary
ridges, also protrude into the dermis, but correspond to the furrows on the surface of
the skin.
These unique features are formed at around the 15th week of fetal development and
remain until after death, when decomposition begins.

13. 1. Epidermis(outer layer of skin)-0.1mm (or 100 μm) thick
( on palms and soles: 0.8-1.4mm)
It is stratified squamous keratinized epithelium composed of
cells called keratinocytes(most abundant cell type) and 3 kinds
of much less abundant epidermal cell types:pigment-producing
melanocytes, antigen-presenting Langerhans cells, and tactile
epithelial cells called Merkel cells
Epidermis is avascular (no blood vessels) like other epithelia.
Epidermis receives nourishment from dermis, hence Cells lying
far away from nourishment die
2. Dermis(Dense connective tissue layer of Skin): 2-3 mm thick
-Dermis is highly vascular (has blood vessels)

14. Friction blisters are lymph-filled spaces created between the epidermis and
dermis of thick skin caused by excessive rubbing, as with ill-fitting shoes or
hard use of the hands. If continued, such activity produces protective thickening
and hardening of the outer cornified epidermal layers, seen as corns and
calluses.

15. 4 Cell types seen in the epidermis
•Keratinocytes(most
abundant cell type),
•Melanocytes(one
melanocyteforeveryfiveor
sixbasalkeratinocytesi.e.
600-1200cells/mm2ofskin),
•Langerhanscells(2%-8%of
thecellsinepidermis)
•Merkelcells.

16. Traditionally skin divided into 2 types:
Thin skin–hairy and seen in most parts of
the body.
Thick skin(Glabrous skin) –seen in palms &
soles and is hairless.
“thick” and “thin” refer to the
thickness of the epidermal layer,
which alone varies from 75 to 150
μm for thin skin
and from 400 to 1400 μm (1.4 mm)
for thick skin.
Hair is absent on the dorsal surface of the last segment of the digits, nipples,
lips, glans penis, prepuce, glans clitoris, labia minora and inner surface
of labia majora.

17. Thick skin Thin skin
Present in palm and sole Present in other parts of
bodyexcept palm and sole
Epidermis is thick and all the
5 layers are seen clearly.
Epidermis is thin and
lucidumis not seen clearly
Dermis shows onlysweat
glands
Dermis contains sweat
glands,hairfollicles,
sebaceous glands and
arectorpilimuscle (smooth
muscle)

18. THICK SKIN

19. THIN SKIN

20. Layers of the epidermis

21. Dermal blood vessels
Tactile cell
Melanocyte
Dead keratinocytes
Exfoliating
keratinocytes
Living keratinocytes
Dendritic cell
Stem cell
Dermis
Stratum lucidum
Stratum basale
Stratum granulosum
Stratum spinosum
Stratum corneum
Sweat pore
Tactile nerve fiber
Dermal papilla
Sweat duct
The epidermis(cells of epidermis) arranged as four(4) layers
in thin skinbut in thick skin -five (5) layers

22. •Layersofepidermis(fromdeeptosuperficial):
a.Stratumbasale(basalcelllayer);
b.Stratumspinosum(Spinous/pricklecelllayer);
c.Stratumgranulosum(Granularcelllayer);
d.Stratumlucidum(clearcelllayer)
e.Stratumcorneum(Hornycelllayer).
•LayersofDermis:
a)papillarylayerand
b)reticularlayer

25. Note the cell types in the
epidermis

26. The basal layer (stratum basale)–
Contains Single layer of basophilic
cuboidal or columnar cells on the
basement membrane at the dermo-
epidermal junction.
Desmosomes bind the cells of this
layer together in their lateral and
upper surfaces. Hemidesmosomes
in the basal cell membranes join
these cells to the basal lamina.
The stratum basale is characterized
by intense mitotic activity and
contains progenitor cells for all the
epidermal layers lying superficially
(in simple words stem cells for
keratinocytes found here).
Layers of epidermis

27. A small pink growthwith a slightly
raised, rolled edge and a crusted
indentation in the center
In adults, one-third of all cancers originate in the skin. Most of
these derive from cells of the basal or spinous layers,
producing, respectively, basal cell carcinomas and squamous
cell carcinomas.
Basal cell carcinomas

28. Keratinocytes
•Most abundant cell type
in epidermis
•Derived by continuous
mitosis of the cells of the
stratum basale
•Cells push their way up
to the surface where they
are dead and slough off
(desquamation).
•Cell turnover time 40-56
days but reduced to 6-8
days in psoriasis.
An important feature of all keratinocytes in the stratum basale is the cytoskeletal
keratins, intermediate filaments about 10 nm in diameter. During differentiation, the
cells move upward and the amount and types of keratin filaments increase until they
represent half the
total protein in the superficial keratinocytes.keratin (fibrous protein) gives waterproofing to
the skin

30. 2-Melanocytes(5-10%):
•Other cell type found in the stratum basale and also in hair
follicles. Melanocytes are neural crest derivatives that migrate into
into the embryonic epidermis’ stratum basale.
•Histologically they have pale-staining, rounded cell bodies
attached by hemidesmosomes to the basal lamina, but no
attachments to the neighboring keratinocytes.
•Several long irregular cytoplasmic extensions (branching
processes) from each melanocyte cell body penetrate and run
between the cells of epidermis of the basal and spinous layers and
and terminating in invaginations of 5-10 keratinocytes.

31. Melanocytes(5-10% of
the total epidermal cell
population):

32. •Melanocytes produce brownish or black pigments(Eumelanins).similar
pigment in red hair is called pheomelanin (Gr. phaios, dusky + melas, black
•Melaninaccumulates in melanosomes and transported along branching process
of the melanocytes to keratinocytes.
•The first step in melanin synthesis is catalyzed by tyrosinase, a transmembrane
enzyme in Golgi-derived vesicles.
•Tyrosinase activity converts tyrosine into 3,4-dihydroxyphenylalanine (DOPA),
which is then further transformed and polymerized into the different forms of
melanin.
•Melanin pigment is linked to a matrix of structural proteins and accumulates in
the vesicles until they form mature elliptical granules about 1-μm long called
melanosomes

34. Melanosomesare then transported via kinesin to the tips of the
cytoplasmic extensions. The neighboring keratinocytes
phagocytose the tips of these dendrites, take in the
melanosomes, and transport them by dynein toward their
nuclei.
One melanocyte plus the keratinocytes into which it transfers
melanosomes make up an epidermal-melanin unit.
In keratinocytes the melanin granules are transported to a
region near the nucleus, where they accumulate as a
supranuclear cap shading the DNA against the harmful
ionizing, mutagenic effects of UV radiation.
Although melanocytes produce melanosomes, the
keratinocytes are the melanin depot and thus contain more of
this than the cells that make it!

35. Mole/Nevus(pluralneviornaevi, from L: for "birthmark")
Melanocytes can normally proliferate
in
skin to produce moles, or benign
melanocytic nevi of various types.
Nevi (clusters of melanocytes)-
arebenign! However, 25% of
malignant melanomas (a skin cancer)
arise from pre-existing nevi/moles
Nevi(moles) can be -
1.Junctional (more pigmented, more
associated with melanoma)
2.Intradermal
3.Compound (both)

36. MALIGNANT MELANOMA
-is a tumor produced by the
rapidly dividing, malignantly
transformed melanocytes
•often penetrate the basal lamina,
enter the dermis,
and metastasize by invading
blood and lymphatic vessels.
Melanomas may be
differentiated from benign nevi by
the ABCDE criteria:
A -Asymmetry
B -Border irregularity
C -Color that tends to be very dark black or
blue and variable
D -Diameter ≥6 mm
E -Evolution over time

38. Vitiligo-Localized
depigmentation. An acquired
condition due to the loss or
decreased activity of
melanocytes.
The causes of melanocyte loss
are not clear, but they may
include environmental, genetic,
orautoimmune conditions.
Albinism-
Total depigmentation of
the skin.
is a congenital
(autosomal recessive)
disorder.
Absence of tyrosinase

39. Freckles(EPHELIS)
Frecklesare clusters of
concentratedmelanin often
visible on people with a
faircomplexion.
Freckles do not have an
increased number of
melanin producing cells
(melanocytes), but instead
have cells that overproduce
melanin granules changing
the coloration of the skin.

40. Melasmais a skin condition characterized by brown or blue-gray
patches or freckle-like spots. It’s often called the “mask of
pregnancy.” Melasma happens because of overproduction of
pigment by the cells that make the color of skin. It is common,
harmless. It is most common in women 20 to 50 years of age. Men
can also be affected.

41. Skin color
•Attributed to melanin, Hemoglobin and carotene.
•Color determined by amount of melanin not by # of
melanocytes.
•UV light stimulates melanin production. Excessive UV light
can damage DNA and cause solar elastosis (elastin fibers
clump)
•Local accumulation of melanin will result in freckles and
pigmented areas.

42. Hemoglobin (blood) & related pigments will
impart tones to skin.
1-Redness (erythema) -reddened skin, embarrassment, fever,
hypertension, inflammation, or allergy
2-Pallor/blanching -pale skin, emotional distress or anemia, low
blood pressure
3-Jaundice -liver disease, bile deposited in tissue
4-Bronzing -bronze coloration (Addison's disease) hypofunction
of adrenal cortex
5-Black & blue -bruises, escaped blood clots in tissue spaces
(clotted blood masses = hematomas)

43. 3-Merkel cellsor epithelial tactile cells :
also found in stratum basale,Joined by desmosomes to keratinocytes
of the basal cell layer (resemble the surrounding keratinocytes but
contain few, if any, melanosomes). Merkel cells originate from the
same stem cells as keratinocytes .
Make contact with a sensory neuron ending called a Merkel disc
and act as sensitive mechanoreceptors, essential for light touch
sensation.
They are abundant in highly sensitive skin like that of fingertips and at
the bases of some hair follicles.
Merkel cells are of clinical importance because Merkel cell
carcinomas, (though uncommon -40 times less common than
malignant melanoma), are very aggressive and difficult to treat with
high mortality.

45. Summary of Stratum basale:
-deepest epidermal layer
-attached to dermis
-Made of single row of columnar / cuboidal cells, which
rests on a basal lamina –keratinocytes,
-Show rapid mitotic divisions (stratum germinativum)
-Other cell types seen in Stratum basale are the Merkel
cells and melanocytes(5-10%of total cells)

46. 2.Stratum spinosum(spiny or prickle cell layer)
-This layer contains 8-10 rows ofkeratinocytes. The keratin
filaments assemble here into microscopically visible bundles
called tonofibrilsthat converge and terminate at the numerous
desmosomes holding the cell layers together
-Cells are polyhedral (many sided) withappearance of prickly
spines( Cells retract/ shrink while preparing a section except at
desmosomes. As a result the cells appears to have spines(prickle
cells)-so the name spinosum.
-Cytoplasm contains melanosomes(pigment granules)
-Langerhans's cells are seen in this layer of epidermis
apart from keratinocytes,

49. Langerhans’ cells (2-8% of the cells in epidermis ):
•Star -shaped , arising from bone marrow that migrate to
epidermis (epidermal macrophages)
•Easily damaged by UV light.
•Usually seen in the spinous layer(Stratum Spinosum).
•
•These are the antigen-presenting cells (APCs). Cytoplasmic
processes extend from these dendritic cells between keratinocytes
of all the layers, forming a fairly dense network in the epidermis.
•Langerhans cells bind, process, and present antigens to T-
lymphocytes in the same manner as immune cells in other organs

50. •3-5 rows of flattened cells
•Nuclei of cells flatten out
•Intensely (darkly stained)
basophilic masses called
keratohyaline granules. These are
dense, non–membrane-bound
masses of filaggrin and other
proteins associated with
tonofibrils, linking them further
into large cytoplasmic structures.
3. Stratum granulosum

51. •Characteristic feature in cells of the
granular layer also include Golgi-
derived lamellated granules( elliptical
membrane bound vacuoles with many
lamellae also called asOdland
bodies’)-containing various lipids and
glycolipids.
•These lamellar granules undergo
exocytosis, producing a lipid-rich,
impermeable layer around the cells.
This material forms a major part of
the skin’s barrier against water
loss(crucial sealing effect).Formation
of this barrier, was a key in
evolutionary process?
•Once organelles disintegrate, cells
eventually die and pushed upwards
3. Stratum granulosum

53. Seen in thick skin -palms and
soles)
•Lucid =clear ,so called because
homogenous, cell boundaries are
not seen.
Translucent layer of flattened
eosinophilic keratinocytes
held together by desmosomes .
Nuclei and organelles have been
lost, and the cytoplasm consists
almost exclusively of packed
keratin
filaments embedded in an
electron-dense matrix.
This layer stains strongly with acidic
dyes(eg: eosin).
4. Stratum Lucidum:

54. 5. Stratum corneum:
Most superficial layer,20-30 cell layers thick
but acellular
consists of flat scale like elements
(squames)containing keratin filaments.
Keratin filaments contain at least six different
polypeptides with molecular masses ranging
from 40 to 70 kDa, synthesized during cell
differentiation in the immature layers.
•Thickest where skin is exposed to maximum
friction.
Continuously shed off at the epidermal
surface as the desmosomes and lipid-rich
cell envelopes break down(desquamation).
Effective barrier against water, light, heat and
bacteria

59. Skin color
•Attributed to melanin,
Hemoglobin and carotene.
•Color determined by amount of melanin
not by # of melanocytes.
•UV light stimulates melanin production. Excessive UV light
can damage DNA and cause solar elastosis (elastin fibers
clump)
•Local accumulation of melanin will result in
freckles and pigmented moles.

60. Clinical anatomy
1. Intradermal injections-
2. Subcutaneous/Subdermal/
hypodermal injections-
the ideal sites can be
Posterior aspect of arm, Anterior
aspect of forearm, Anterior abdominal wall
Anterior aspect of thigh

61. ?

62. GRN 62
A physician delivers an intramuscular injection into the lateral aspect of the
shoulder. Which of the following sequences describes the correct order of
tissue layers pierced by the needle, passing from superficial to deep?
(A)Epidermis, dermis, superficial fascia, epimysium, deep fascia
(B)Dermis, epidermis, superficial fascia, deep fascia, epimysium
(C)Dermis, epidermis, superficial fascia, epimysium, deep fascia
(D)Epidermis, dermis, superficial fascia, deep fascia, epimysium
(E)Epidermis, superficial fascia, dermis, deep fascia, epimysium