1. The document discusses the structure and functions of skin and hair. It describes the layers of the skin (epidermis and dermis), structures (sweat glands, hair follicles), and functions (protection, temperature regulation, sensation). 2. Hair has a cuticle, cortex and sometimes a medulla. Hair grows from hair follicles, which develop during embryogenesis through interactions between the epidermis and dermis. 3. The hair follicle contains the hair bulb that produces the hair fiber through the hair matrix and is influenced by the dermal papilla.

1. SKIN AND HAIR
COSMETIC SCIENCE
VIII Sem B Pharm
By,
Mr. Maruthi. N
Asst. Professor
(Pharmaceutics)
SJM College of Pharmacy
Chitradurga-577502
Karnataka

2. CONTENTS
• Introduction to skin
• Functions of skin
• Structure of skin
• Anatomy and physiology of skin
• Basic structure, of hair
• Hair growth
• Functions of hair and
• Hair follicle

3. SKIN STRUCTURE & FUNCTIONS
 Basic Knowledge of the skin and its functions are very important in cosmetic
preparations bcz it is to be applied for beautification, protection or other
purpose.
 Skin the heaviest single organ of the body, combines with the mucosal lining
of the respiratory, digestive and urogenital tracts to form a capsule which
separates the internal body structures from the external environment.
 It not only physically protects the internal organs and limits the passage of
substances into and out of the body but also stabilizes temperature and blood
pressure with its circulation and evaporation.

4. SKIN STRUCTURE & FUNCTIONS
 For an average six foot, 70 kg human, the skin surface area is 1.9 m² and
weighs about 2100 gms. A typical square centimeter of skin covers 10 hair
follicles, 12 nerves, 15 sebaceous glands, 100 sweat glands, 3 blood vessels and
92 cm of nerves and 3x10⁶ cells.
 Normally the skin is very smooth. Bcz of environmental impact it becomes
rough and thick.
 pH of the skin varies from 4 to 5.6. Sweat and fatty acids secreted from sebum
influence the pH of the skin surface. It is suggested that acidity of skin helps in
limiting or preventing the growth of pathogens and other organisms.

5. Functions of skin
• Containment of body fluids and tissues
• Protection from external stimuli like chemicals, light, heat, cold and radiation
• Reception of stimuli like pressure, heat, pain
• Biochemical synthesis, (Collagen, Vitamin D) Metabolism and disposal of
biochemical wastes
• Regulation of body temperature
• Controlling of blood pressure

6. Structure of Skin
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7. • Skin contains several chemical substances with specific functions like
keratin, lipids, fatty acids, proteinase etc.
• Keratin produced from polypeptides in the cytoplasm of epidermal cells
by a high energy system at the granular layer of normal human skin.
• Sebum is the product of the sebaceous glands and consists of
triglycerides, free fatty acids, waxes, sterols, sqalene and paraffin's.
Free fatty acids are responsible for bactericidal and fungicidal
activities.

8. • Skin also contains two essential fatty acid, called linoleic acid and
arachidonic acid, which plays an important role in regulating the
barrier functions.
• Skin synthesizes on steroid, Vitamin D3,which converts to Calciferol
required in calcium metabolism.
• A proteinase has been isolated which is believed to play a role in
modulating the inflammatory response to cellular injury.

9. ANATOMYAND PHYSIOLOGY
The human skin comprises of three distinct but mutually dependent tissues, stratified,
avascular, cellular epidermis and an underlying dermis of connective tissue at the
bottom of the dermis lies fatty, subcutaneous layer.
A. Epidermis- this varies in thickness, depending on cell size and the no. of cell layers,
ranging from 0.8 mm on the palms and the soles down to 0.06 mm on the eyelids.
Epidermis comprised of 5 distinct and separate layers.
1. Horny layer (Stratum corneum): Superficial layer of epidermis is stratum
corneum. 10 -15 layers of much flattened, keratinized dead cells, having 10µm thick
when dry, but swells in water to several times this thickness.

10. 2. Stratum Lucidum: In the palm of the hand and the sole of the foot, an
anatomically distinct, poorly staining hyaline zone forms a thin, translucent layer
immediately above the granular layer. This region is stratum lucidum. Cells are
non nuclear.
3. Stratum Granulosum: Above the layer of keratinocytes, which synthesizes the
keratin, by degeneration process.
4. Stratum Spinosum (prickly cell layer): This layer forms by the basal layer as
they moved upward. They are also called polygonal cells, prickle cells, bcz they are
interconnected by fine prickles. These links maintain the integrity of the epidermis.
5. Stratum Germinativum: These basal cells are nucleated, columnar and about
6µm wide, with their long axis. Basal cells include melanocytes which produce and
distribute melanin granules to the keratinocytes required for pigmentation, a
protective measure against radiation.

12. B. Dermis: Lying between the epidermis and subcutaneous fatty region. Consists
of dense network of structural protein fibres i.e. collagen, reticulum and elastin,
embedded in the semi gel matrix of mucopolysaccharideic ‘ground substances’.
It is 0.2 to 0.3 cm thick. Elasticity of skin is due to the network or gel structure
of the cells. Beneath the dermis, the fibrous tissue opens out and merges with the
fat containing subcutaneous tissue.
C. Subcutaneous Tissue: It is a sheet of fat rich areolar tissue, known as
superficial fascia, attaching the dermis to the underlying structures. It is quite
elastic. Large arteries and veins are present only in the superficial region.

13. D. Skin Appendages: Sweat glands, ecrine and apocrine glands, collectively called as
skin appendages.
• Hair follicles are distributed over the entire skin surface except soles of the feet, the
palm of the hand, the red portion of the lips and selected portion of the sex organs.
Hair shaft is formed by a process of cellular division and migration of the cells.
Hairs are thus formed of keratinized cells compacted together into plates and scales.
• Each hair follicle associated with one or more sebaceous gland which are referred as
the acid mantle of the skin. It secretes oily material, sebum, which lubricates the skin
and stratum corneum and also maintains the pH of the skin at 5.

14. a. Ecrine sweat glands: Salty sweat glands are distributed over the surface of the
body. They are simple and coiled tube like structure. Density of 100 to 200 glands
per cm2 of the body surface. Secretion is dilute aqueous solution of salt and some
other minor components and it has a pH of about 5. Principal function of the gland is
heat control, regulates body temperature.
b. Apocrine glands: It present only in selected region of the body viz. axillae
(armpits), anogenital region and around the nipples. These are 10 times larger than
ecrine glands and secretes a milky substance containing protein, lipoprotein, lipids
and diverse proteins. Secretion stimulated due to emotional stress and sexual
stimulation.

15. HAIR
BASIC STRUCTURE, HAIR GROWTH, FUNCTIONS AND
HAIR FOLLICELE

16. BASIC STRUCTURE OFHAIRAND GROWTH CYCLE
 Hair is one of the vital parts of the body. They are also known as epidermal
derivatives as they originate from the epidermis during embryological
development. Hair is an important component of the overall appeal of the
human body.
 Before puberty the hair is mainly present on the scalp, the eyebrows and
eyelashes, irrespective of sex. At puberty hair grows in other place like axillae,
over the pubes in both the sexes and in male as beard on the face. Though all
mammals have hair but hair in man is different from others.

17. STRUCTURE OF HAIR

19.  Hairs can be found nearly all over the surface of the skin except over some
specific sites like the sides and soles of the feet, palms of the hands, sides
of the fingers and toes, the lips, and portions of the external genitalia.
 There are about 50,00,000 hairs on the human body and 98% of them are
on the general body surface and about 10 lakh to 10.20 lakh are on the
head.
 Scalp and chin have highest rate of growth. The rate of growth of scalp
hair is between 0.27-0.40 mm per day. Growth of scalp hair in women is
faster than man.

20. FUNCTIONS OFHAIR
• Hair on the head protect the scalp from UV light, cushion round the head, and
insulate skull.
• Eyebrows protect the eye from small foreign particles and insects. Also it
diverts sweat from eyes.
• Vibrissae the hairs, guarding the entrances to nostrils and external ear canals
filter the air and help prevent the entry of small insects and foreign particles.
• Body hair helps in evaporation of perspiration (sweat) and draining of
external water from the body.
• Hair is also part of sensory function.

21. HAIR MORPHOLOGYAND MORPHOGENESIS
• Hair is an integrated complex system of several morphological components
that act as a unit. The part of the hair seen above the skin is termed the hair
fiber and inside the skin the hair follicle is the live part of hair from which
the hair grows and where the hair fiber is generated.
• Hair follicles initially form in the skin of a human embryo as invaginations
of the epidermis into the dermis between the 8th and 12th week of gestation.
• The key prerequisite for hair follicle development is the interaction between
the epidermis and underlying mesenchyme, which remains in intimate
contact throughout the life of the follicular unit.

22. • Reciprocal interactions occur between the epidermal
keratinocytes, committed to hair follicle and that engage in specific
differentiation and the mesenchyme cells, that form follicular
papilla.
• These interactions are governed by the series of inductive events
or “messages”. Once the distribution of the follicles has been
established, subsequent molecular events in the developing follicle
determine the future phenotype of each hair.

23. • The development and differentiation of hair follicles during embryogenesis is
classically divided into three main stages: induction, organogenesis ( or
progression) and cyto differentiation (or maturation), which are
morphologically characterized as germ, peg and bulbous follicles.
• During the initial events of hair follicle induction, with mediated signal
transduction arises first in mesenchymal cells directing the thickening of
overlying epithelial cells to form a placode. This is followed by hair follicle
organogenesis and cyto differentiation., each phase being characterized by
specific molecular interactions.

24. • The organogenesis comprises a complex interplay of signals.
Epithelial cells direct the underlying dermal cells to proliferate and
form a dermal condensate, which in turn signals the epithelial cells to
proliferate and grow downwards into the dermis. During cyto
differentiation, the dermal condensate is enveloped with follicular
epithelial cells creating a distinct dermal papilla, which instructs the
ectoderm to shape the entire hair follicle through the action of
morphogens and growth factors.

25. HAIR FOLLICLEANATOMY
• Hair follicle is a complex epithelial structure and is enclosed by a outer root
sheath(ORS), which helps to support hair growth, and an inner root sheath
(IRS), and follows the hair fiber up to the opening of the sebaceous gland. The
ORS and IRS are separated by the companion layer.
• The IRS can be subdivided into three distinct cell layers: Henle’s layer,
Huxley’s layer and the cuticle of IRS. Besides these two layers, ORS and IRS,
the hair follicles are composed of four other different epidermal layers: hair
matrix, medulla, cortex and cuticle, as well as two dermal tissues: dermal
papilla and derma sheath.

26. • Among these layers, only the medulla is not always present, given the some
hairs have no medulla and others have a medulla relatively large. Each layer
itself can comprise numerous individualized cell layers characterized by
specific programs of differentiation.
• Within the skin, the terminal region of the hair follicle is called hair bulb, which
is the structure formed by actively growing cells that produce the long, fine and
cylindrically shaped hair fibers. The hair bulb comprises the hair matrix that
will differentiate into the different precursors of the hair fiber, dermal papilla
and surrounding dermal sheath.

27. • Additionally, the hair bulb also contains very specialized cells, the
melanocytes, which produce the pigment melanin that gives color to
the hair fiber. In combination with its associated structures
(sebaceous and apocrine gland, arrector pili muscle), the hair follicle
forms the pilosebaceous unit. The hair follicle primarily acts as a
factory for pigmented, multifunctional and exceptionally durable
proteinaceous fibers-hair.

28. HAIR FIBER STRUCTURE
• Hair fiber has 50-100 µm in diameter, got protective and cosmetic
functions.
• Hair protects the scalp from sunburn and mechanical abrasion, provides
thermoregulation and social communication. The body is covered with
hairs of 2-4 cm in length, under 40 µm in diameter, and often
unpigmented, named vellus hairs. Human hair fibers are divided into
three main morphological constituents, also components of he hair
follicle: cuticle, cortex and, in some cases, medulla

29. • Cuticle- The hair fiber is enclosed in the cuticle, a barrier protecting
the underlying cortex from external environmental damage. It
contains 6-10 layer of overlapping scales, in a way that only
approximately one-sixth of each surface is exposed. The cuticles
proximal end is firmly attached to the cortex and the distal open end
of the overlapping tiles points towards the tip of the fiber. The shape
and orientation of the cuticle cells are responsible for limiting friction
between hair fibers.

30. • The outermost layer of cuticle cells is the epicuticle, a lipid layer that includes 18-
methyl eicosanoid acid and free lipids, providing lubricity to the hair and
consequently constituting the first line of defense against environmental assaults.
Immediately below cysteine content, highly cross-kinked, which confers structural
strength and rigidity to the cuticle. The following layers gradually have less cysteine
content and consequently les rigidity. The B layer contains 15% cysteine content.
The last layer corresponds to the endocuticle, which is mainly composed by
remaining cell organelles contains 3% cysteine. Hence, this layer swells more in
water than the layers richer in cysteine, and it is mechanically softer. Finally, the
cellular membrane complex is the intercellular cement that holds the cuticle cells
together, primarily composed of non-keratinous protein with low content 2%.