Basic Skin Structure Prepared By RASHIDUL HASAN ROBEL B. PHARM (RU), M. PHARM (RU) REG. NO. A4968 PGD-HRM (BIM) EMBA (ULAB)

1. PREPARED BY
RASHIDUL HASAN ROBEL
B. PHARM (RU), M. PHARM (RU)
REG. NO. A4968
PGD-HRM (BIM)
EMBA (ULAB)

2. INTEGUMENTARY SYSTEM
 In biology, integument is the natural
covering of an organism or an organ,
such as its skin, husk or shell. It
derives from integumentum, which
means ‘a covering’ in Latin and is an
alternative name of skin.
 The integumentary system is an
organ system consisting of the skin,
hair, nails, and exocrine glands.
 Dermatology is the branch of
medicine dealing with the skin, nails,
hair and its diseases.

3. SKIN
• Largest organ of the body
• Completely covers the body
• Average thickness: 1-2 mm. (0.5mm eyelids, 6mm palms and soles)
• pH: 4 - 5.6
• Renewal of skin takes place in 28-50 days by
shedding of the outer layer.
The thin layer of tissue forming the natural outer
covering of the body of a person or animal. Skin is an
organ because it consists of different tissues that are
joined to perform a specific function.

4. FUNCTIONS OF SKIN
1. Protection
- Physical barrier that protects underlying tissues from injury,
UV light and bacterial invasion.
- Mechanical barrier is part non specific immunity (skin,
tears and saliva).
2. Regulation of Body Temperature
- High temperature or strenuous exercise; sweat is evaporated
from the skin surface to cool it down.
- vasodilation (increases blood flow) and vasoconstriction
(decrease in blood flow) regulates body temperature.

5. 3. Sensation
- Nerve endings and receptor cells that detect stimuli to
temperature, pain, pressure and touch.
4. Excretion
- Sweat removes water and small amounts of salt, uric acid
and ammonia from the body surface
5. Blood Reservoir
- Dermis houses an extensive network of blood vessels
carrying 8-10% of total blood flow in a resting adult.
6. Synthesis of Vitamin D (cholecalciferol)
- UV rays in sunlight stimulate the production of Vit-D.
Enzymes in the kidney and liver modify and convert to final
form; calcitriol (most active form of Vit-D.) Calcitriol aids
in absorption of calcium from foods and is considered a
hormone.

6. SKIN STRUCTURE
3 layers of skin structure
 Epidermis
Epithelial tissue
 Dermis
Dense connective tissue proper (irregular)
 Hypodermis
Subcutaneous tissue (loose connective tissue proper and adipose tissue)

7. 3 LAYERS OF SKIN

8. EPIDERMIS
 Epidermis
 It is avascular stratified squamous epithelium
 Nutrients and oxygen diffuse from capillaries in the dermis
 Cells of Epidermis
 Keratinocytes (90%) : Waterproofs & protects skin, nails, hair,
stratum corneum and also provides rigidity by producing tough,
triple-helix-shaped protein strand called Keratin.
 Melanocytes (8%) : Produce melanin that gives skin color
 Merkel Cells : Slowly adapting mechanoreceptors that
mediate the senses of touch and hair movement.
 Langerhans’ Cells : Immunological defense

9. EPIDERMIS
The structural relationship and
interface between the epidermis
and underlying dermis. The
proportions of the various layers
differ with the location sampled.
Dermis
Epidermis
Epidermal
ridge
Dermal
papilla

10. SKIN STRUCTURE: EPIDERMIS
 Thin Skin
 Covers most of the body
 Has four layers of keratinocytes
 Thick Skin
 Covers the palms of the hands and soles of the feet
 Has five layers of keratinocytes

11. SKIN STRUCTURE: EPIDERMIS
 The five strata of keratinocytes in thick skin
 From basal lamina to free surface
1. Stratum Basale
2. Stratum Spinosum
3. Stratum Granulosum
4. Stratum Lucidum (absent in thin skin)
5. Stratum Corneum

12. Thick skin
EPIDERMISLAYER

13. SKIN STRUCTURE: EPIDERMIS
Stratum Basale
 It is attached to basement membrane by
hemidesmosomes
 Forms a strong bond between epidermis and dermis
 Forms epidermal ridges (e.g., fingerprints)
 Dermal papillae (tiny mounds)
• Increase the area of basement membrane
• Strengthen attachment between epidermis and dermis
 Has many basal cells or germinative cells.

14. Thick skin SEM  25
Epidermal
ridge
Pores of sweat
gland ducts
Epidermal ridges

15. SKIN STRUCTURE: EPIDERMIS
Stratum Spinosum
the ‘spiny layer’
Produced by division of stratum basale
 8-10 layers of keratinocytes bound by desmosomes
 Cells shrink until cytoskeletons stick out (spiny)
 Continue to divide, increasing thickness of epithelium
 Contain dendritic (Langerhans) cells, active in immune
response

16. SKIN STRUCTURE: EPIDERMIS
Stratum Granulosum
The ‘grainular layer’
Stops dividing, starts producing keratin & keratohyalin
• Keratin
a) A tough, fibrous protein
b) Makes up hair and nails
• Keratohyalin
a) Dense granules
b) Cross-link keratin fibers

17. SKIN STRUCTURE: EPIDERMIS
 Stratum Lucidum
 The ‘clear layer’
 Found only in thick skin
 Covers stratum granulosum
 Stratum Corneum
 The ‘horn layer’
 Exposed surface of skin
 15 to 30 layers of keratinized cells
 Water resistant
 Shed and replaced every 2 weeks

18.  Located between
epidermis and
subcutaneous layer
 Anchors epidermal
accessory structures
(hair follicles, sweat
glands)
 Two components
1. Outer papillary layer
2. Deep reticular layer
SKIN STRUCTURE: DERMIS
DERMIS

19. SKIN STRUCTURE: DERMIS
 Papillary Layer
 Consists of areolar tissue
 Contains smaller capillaries, lymphatics, and sensory
neurons
 Has dermal papillae projecting between epidermal ridges
 Reticular Layer
 Consists of dense irregular connective tissue
 Contains larger blood vessels, lymphatic vessels, and
nerve fibers
 Contains collagen and elastic fibers

20. Hair
Papillary
layer
Reticular
layer
Cutaneous
plexus
Papillary
plexus
Epidermal
ridges
Dermal
papillae
Capillary loop
of papillary
plexus
DERMISLAYER

21. SKIN STRUCTURE: HYPODERMIS
 Hypodermis (Subcutaneous Layer)
 Lies below the integument
 Stabilizes the skin
 Allows separate movement
 Made of elastic areolar and adipose tissues
 Connected to the reticular layer of integument by connective
tissue fibers
 Deposits of Subcutaneous Fat
 Distribution patterns determined by hormones
 Reduced by cosmetic liposuction (lipoplasty)

22. SKIN STRUCTURE: HYPODERMIS

23. SKIN APPENDAGES
● HAIR
● NAILS
● GLANDS

24. HAIR
 Mainly composed of keratin.
 Dead keratinocytes fuse together to
form the hair.
 At the base of the follicle is the bulb,
which contains cells that give rise to
the keratinocytes that make up the
hair, as well as blood vessels that
nourish the growing hair.
 Each hair follicle also contains
arrector pili, a muscle that
contracts in response to cold, fright,
and other emotions. When the
muscle contracts, it pulls the hair in
the follicle into a vertical position.
Dermis
Hypodermis

25. This response may help
some mammals keep
warm or look bigger to
frighten or intimidate
their enemies.
But in humans, because
of our sparse coat of
body hair, it merely
produces ‘goose bumps’.

26. STRUCTURE OF HAIR
 Hair Follicle
 Hair follicles are the organs that form the hairs
 Located deep in dermis
 Produces nonliving hairs
 Wrapped in a dense connective tissue sheath
 Base is surrounded by sensory nerves (root hair plexus)
 Control bacteria

27. Exposed
shaft
of hair
Sebaceous
gland
Arrector
pili
muscle
Connective
tissue sheath
Root hair
plexus
 Arrector pili
– Involuntary smooth muscle
– Causes hairs to stand up
– Produces ‘goose bumps’
 Sebaceous glands
– Lubricate the hair
STRUCTURE OF HAIR

28. Regions of Hair
 Hair root
• Lower part of the hair
• Attached to the integument
 Hair shaft
• Upper part of the hair
• Not attached to the
integument
Boundary
between
hair shaft
and
hair root
Hair shaft
Sebaceous
gland
Arrector
pili muscle
Hair root
Connective
tissue sheath
Hair bulb
Hair matrix
Hair papilla
STRUCTURE OF HAIR

29. Hair Shaft Structure
 Medulla
 Core, dead cells contain soft keratin and air to provide flexibility
 Cortex
 Middle layer, dead cells contain hard keratin to provide stiffness
 Cuticle
 Outermost, overlapping dead keratinized cells form shiny surface
STRUCTURE OF HAIR

30. Hair on Head
 UV protection
 Cushion from trauma
 Insulation
Nostrils, Ear canals, Eyelashes
 Prevent entry of foreign material
Body Hair
 Sensory detection
Root Hair Plexus
 Sensory nerves at base of hair follicle that detect slight
movement of hair
Arrector Pili Muscle
 Attached to every hair follicle
 Contract to stand hair perpendicular to skin surface
FUNCTIONS OF HAIR

31. STRUCTURE & FUNCTION OF NAIL
 Nails
 Protect fingers and toes
 Made of dead cells packed with keratin
 Metabolic disorders can change nail
structure
 Nail Production
 Occurs in a deep epidermal fold near
the bone called the nail root
Free edge
of Nail
Body of
Nail
Laternal
Nail fold
Lunula
Eponychium
(cuticle)

32. STRUCTURE & FUNCTION OF NAIL
Nail Structure
 Nail body
 The visible portion of the nail
 Covers the nail bed
 Lunula
 The pale crescent at the base of the nail
 Nails Sides
 Lie in lateral nail grooves
 Surrounded by lateral nail folds

33. NAIL STRUCTURE
Cross-sectional
view
Lateral nail fold
Nail
body
Lateral
nail
groove
Nail
bed
Phalanx
(bone of
fingertip)

34. NAIL STRUCTURE
Longitudinal section
Eponychium
Proximal nail fold
Nail root
Lunula Nail body
Epidermis Dermis Phalanx Hyponychium

35. SKIN GLANDS
 An adult human has between 1.6 to 4
million sudoriferous glands, or sweat
glands.
 Most common type called Eccrine
Sweat Glands, which are found almost
all over the surface of the body and are
most numerous on the palms and soles.
 These glands begin deep in the dermis
and connect to the surface of the skin
by a coiled duct.
 In addition, nerve fibers that encircle the
sweat glands stimulate the glands in
response to fear, excitement, or anxiety.
Sweat Glands

36.  Other sweat glands, known as Apocrine Sweat Glands, are
much less numerous than eccrine sweat glands. They are also
anchored deep in the dermis, but open into hair follicles rather
than onto the surface of the skin.
 Apocrine sweat glands are located mainly in the armpit, genital
area, and around the nipples of the breasts.

37.  Oil or sebaceous glands are found all
over the body except on the palms, the
soles, and the top of the feet.
 These are most numerous on the face
and scalp.
 Most sebaceous glands open into hair
follicles.
 But the glands also occur in some
hairless areas, such as the lips and
inside the mouth.
 It produces an oily substance called
Sebum, which keeps the skin and hair
from drying out and inhibits the growth
of certain harmful bacteria.
Oil Glands

38.  Wax or ceruminous
glands are located in
the ear canal.
 They secrete a waxy
substance that helps
prevent foreign particles
from entering the ear.
 These glands are
modified sweat glands.
Wax Glands

39. SKIN COLOR
(Sub-Saharan African, Indian, Southern European, and Northwest European)
Skin Color Reason: Melanin, Carotene & Hemoglobin
Melanin Pigments
 Eumelanin
 Pheomelanin
High Eumelanin & Low Pheomelanin - Darker skin and hair color
Low Eumelanin & High Pheomelanin - Lighter skin and hair color

40. YOUNG SKIN VS AGED SKIN
 The deepest layer of the epidermis ‘stratum basale’ is mostly
comprised of keratinocytes and is responsible for renewing the
skin every month during young.
 The movement of skin cells from
the basale layer up to top
stratum corneum layer takes
about 28 days, so your skin cells
replace themselves monthly.
 As you age, skin cell turnover
slows. As a result, dead skin
cells build up on the skin’s
surface, making skin look duller.

41.  When you age, collagen
production decreases
and your skin’s ability to
repair collagen and
elastin decreases,
resulting in wrinkles and
loss of elasticity.
 Young skin has thick
bundles of tightly packed
collagen while older skin
has thin, loose bundles
of collagen.
YOUNG SKIN VS AGED SKIN

42.  As you get older, there’s decreased blood flow
through the dermal capillaries.
 Fewer nutrients reach the epidermis, leading to
thinning of the epidermis, slower cell turnover
rate and a reduction in the barrier function of the
epidermis.
 These changes lead to increased water loss
and dry skin. Skin cells have 30 percent less
natural moisture.
YOUNG SKIN VS AGED SKIN

43. Hydration
Elasticity
Firmness
Smoothness
Healthy Skin Color
Dehydration
Wrinkles
Lack of Collagen
Age Spot
Pale Skin Color
YOUNG SKIN VS AGED SKIN