The skin has two main layers - the epidermis and dermis. The epidermis is made of stratified squamous epithelium and contains melanocytes, Langerhans cells, and keratinocytes. The dermis contains hair follicles, sweat and sebaceous glands, as well as blood vessels and nerves. Skin thickness varies in different regions. Thick skin is found on the palms and soles and contains several epidermal layers, while thin skin covers most of the body and has fewer layers. The skin provides protection, temperature regulation, sensation, and other important functions.

1. INTEGUMENT

2. THE SKIN
•The skin or cutis covers
the entire outer surface of
the body.
•Structurally, it has two
layers.
•The epidermis is formed
by an epithelium and is of
ectodermal origin.
•The dermis, consists of
CT and develops from the
mesoderm.
31

3. • Beneath the 2 layers is a
subcutaneous layer of
loose connective tissue,
the hypodermis or
subcutis.
• Hair, nails and sweat and
sebaceous glands are
called the appendages of
the skin.
• The skin and its
appendages together are
called the integumentary
system.
THE SKIN

4. Functions of skin
Protects against injury and dessication
Maintain water balance
Excrete various substances
Thermoregulation
Receive stimuli (temperature, pain,
pressure)
Fat metabolism in the subcutaneous
layer

5. CHARACTERISTIC THICK SKIN THIN SKIN
Surface Texture Alternating ridges
and grooves
Smooth
Epidermis/Dermis
Interface
Interdigitating ridges Less prominent ridges
Epidermal Strata • S. Basale
• S. Spinosum
• S. Granulosum
• S. Lucidum
• S. Corneum
• Same as thick skin,
except: no S.
Lucidum.
• The corneum,
granulosum, and
spinosum layers are
reduced in
thickness.
Hairs and
Sebaceous Glands
None Regionally variable
Sweat Glands Abundant Moderate

6. Regional Variation of the Epidermis
THICK SKIN – sole of foot
(1.4 mm thick)
THIN SKIN – eyelid and most
of body (0.07 TO 0.12 mm)
CORNEA OF EYE –
transparent
APPENDAGES – hair
follicles, follicles, nails,
glands

7. Regional Variation of the Epidermis
The thickness of the skin depends on the
epidermis. Once can have a very thick dermis
and still be considered thin skin.

9. Thick Skin (Layers)
Epidermis)
Dermis
Hypodermis

10. Epidermis
 The superficial, epithelially-derived
region of skin.
1. Stratum basale
2. Stratum spinosum
3. Stratum granulosum
4. Stratum lucidum
5. Stratum corneum

11. Thick Skin
Papillary
layer
Reticular layer
Dermal papillae
Epidermal peg
DERMIS
Papillary
layer
• Dermal
papillae
• Epidermal
pegs
• Meissner’s
corpuscles
Reticular
layer
• Hair follicles
• Sebaceous,
sweat
glands
• Krause’s
end bulb

12. Thick Skin – DERMIS
Dermal papillae
Meissner’s corpuscles
in dermal papillae
Epidermal peg
Dermis
Epidermis
Meissner’s
corpuscle is a
mechanoreceptor
nerve ending for
sensitivity to light
touch.
Epidermis

13. Skin hand monkey - DERMIS
Hypodermis
Papillary layer
Epidermal pegDermal
papillae
AdipocytesEccrine sweat glands
Pacinian corpuscles

14. Epidermal – dermal interphase
Epidermal-dermal interphase between the thin skin and thick skin. The thick
skin has a more elaborate dermal papillae. The interphase prevent the
separation of the 2 layers during mechanical stress.

15. Dermal side
of the Epidermal – dermal interphase

16. Epidermal – dermal interface
If the epidermis is pulled off, the dermal papillae can be seen
projecting into the holes (cavities) within the epidermis.

17. MELANIN is produced by MELANOCYTES
107
Dermal papillae projection

18. Epidermal – dermal interface
- finger pad

19. Thick Skin (Pacinian corpuscle and melanin)
Pacinian corpuscle Melanin pigment
Melanin capping of nuclei

20. Pacinian corpuscles are
mechanoreceptors that detect
vibration and pressure.
105 monkey finger
Pacinian corpuscles

21. Epidermis
STRATUM CORNEUM
• Keratinized flattened,
denucleated, dead cells
STRATUM GRANULOSUM
• Keratohyalin granules
STRATUM SPINOSUM
• Tonofibrils –
desmosomes
STRATUM BASALE
• Continual renewal of
epidermis

22. Thick Skin
5. Stratum basale
Hemidesmosomes
4. Stratum spinosum
3. Stratum granulosum
2. Stratum lucidum
1. Stratum corneum
Desmosomes
Keratohyalin granules
1
2
3
4
5
2
3
4
5

23. Thick Skin
Stratum basale
Hemidesmosomes
Stratum
spinosum
Stratum
granulosum
Stratum lucidum
Desmosomes
Keratohyalin granules
1
S. granulosum:
flattened cells
undergoing
the terminal
differentiation
process of
keratinization –
forming the skin’s
barrier against water
loss when sealed
with contents of
membrane coating
granules.
.

24. Thick Skin on finger
Stratum basale
Hemidesmosomes
Keratohyalin granules
1
The epidermis of
thick skin is subject
to continuous
friction and
pressure so the
abundant
desmosomes
(and tonofibrils)
withstand this and
hold the cell layers
together.
Stratum
spinosum
Dermis
Epidermis
Desmosomes

25. Cells in EPIDERMIS
KERATINOCYTES – main cell
type – ectoderm
MELANOCYTES –
pigmentation – neural
crest
LANGERHANS CELL –
immunologic role
MERKEL CELLS –
associated with nerve
endings

26. MELANOCYTE –
PIGMENT SYNTHESIS
NEURAL CREST ORIGIN (EYE & CNS)
The embryonic origin
of melanocytes is the
neural crest derivatives
that migrate into the
embryonic epidermis’
stratum basale.

27. 111 107
MELANOCYTES
Location: stratum basale;
they appear as clear cells

28. Melanocyte – Pigment Synthesis
Melanogenesis : tyrosine – RER – Golgi – production of melanin
granules
Melanocytes w/ projections – pass melanin granules to keratinocytes
through cytocrine secretion

29. CYTOCRINE SECRETION - PASS MELANIN GRANULES FROM
MELANOCYTES TO KERATINOCYTES

30. MELANOCYTE - PIGMENT SYNTHESIS
LOCATED IN THE STRATUM BASALE
CLEAR CELL – NO DESMOSOMAL CONNECTION

31. Melanin granules above nucleus – protects (UV) it as it is
the source of cells that are mitotically active.
Stratum basale
Stratum spinosum
Stratum granulosum
Stratum corneum
Melanin
capping
of nuclei

32. Melanocytes
respond to
melanocyte
stimulating
hormone
secreted by the
pars
intermedia.
Melanin granule accumulate over the nuclei of
mitotic cells of the stratum basale to protect
nuclear DNA from UV damage.
107

33. LANGERHANS CELLS
• BONE MARROW
ORIGIN
• LOCATED IN
STRATUM
SPINOSUM –
GOLD CHLORIDE
STAIN
• CLEAR CELL – NO
DESMOSOMES
• DENDRITIC CELL

34. LANGERHANS CELLS
• Dendritic cell
• Rod or racket-shaped
granules
• Function –
immunologic role as
antigen-presenting
cell
• Contact allergic
responses and other
cell-mediated
reactions of the skin

35. HAIR

36. External Root Sheath
Sebaceous Gland
(Holocrine Secretion)
Eccrine Sweat Glands
Arrector Pili muscle
Hair Bulb
Connective Tissue (Dermal) Papilla
Hair Shaft
Canal
107 Hair Follicle
?

37. Skin, scalp (Hair follicle)

38. Thin Skin (scalp)
Hair follicle
location
Arrector pili
muscle
Sebaceous glands
Arrector Pili
Muscle –
bundles of
smooth m.
extending from
hair follicle to the
papillary dermis.
• Elevate the
hair, forming
“goose
bumps”.

39. Skin, scalp (Hair)
209

40. Skin,
scalp
Mode of secretion of the
sebaceous glands is
holocrine where by the sebum is
released when cells burst.
sebaceous
glands
Eccrine sweat glands
Human Skin,
scalp 108

41. Simple
columnar
epithelium of
rectum with
goblet cells
Stratified
squamous
epithelium
of anal wall
66

42. THREE TYPES OF GRANULES IN
KERATINOCYTES
MELANIN
• SKIN PIGMENT
• PRODUCED BY MELANOCYTES
AND PASSED BY CYTOCRINE
SECRETION TO KERATINOCYTES
MEMBRANE COATING GRANULES
(LAMELLATED GRANULES)
• WATER PROOFING FUNCTION
• PRODUCED BY KERATINOCYTES
KERATINOHYALIN GRANULES
• PRODUCED BY KERATINOCYTES

43. THREE TYPES OF GRANULES IN
KERATINOCYTES
MEMBRANE COATING GRANULES
(LAMELLATED GRANULES)
• Small, ovoid structures from the
Golgi containing various lipids
and they undergo exocytosis to
produce a lipid-rich
impermeable layer around the
cells of the s. granulosum –
water proofing.

44. THREE TYPES OF GRANULES IN
KERATINOCYTES
KERATINOHYALIN GRANULES
• CHEMICAL NATURE NOT
CLEARLY ESTABLISHED
• MATRIX OF CELLS IN
STRATUM CORNEUM,
STABILITY DUE TO
DISULFIDE BONDS
• ABSENT IN HAIR AND
NAILS

46. Melanocytes in Skin111