DEPARTMENT OF PHARMACEUTICS
KARPAGAM COLLEGE OF PHARMACY
COIMBATORE - 32
SKIN AND HAIR
Structure of Skin and Hair, Hair growth,
Problems in skin
I M.PHARM II SEMESTER
The human skin is the outer covering of the body and is the largest organ of the integumentary
Human skin is similar to most of the other mammals skin, and it is very similar to pig skin
Skin is the largest organ in the body and covers the body's entire external surface.
Though nearly all human skin is covered with hair follicles, it can appear hairless. There are two
general types of skin, hairy and glabrous skin (hairless)
In humans, skin pigmentation varies among populations, and skin type can range from dry to oily.
Such skin variety provides a rich and diverse habitat for bacteria that number roughly 1000
species from 19 phyla, present on the human skin
For the average adult human, the skin has a surface area of between 1.5-2.0 square metres
The average square inch (6.5 cm²) of skin holds 650 sweat glands, 20 blood vessels, 60,000
melanocytes, and more than 1,000 nerve endings.
The average human skin cell is about 30 micrometres in diameter, but there are variants. A skin
cell usually ranges from 25-40 micrometres (squared), depending on a variety of factors.
It is made up of three primary layers,
All three of which vary significantly in their anatomy and function.
The skin's structure is made up of an intricate network which serves as the body’s initial barrier
against pathogens, UV light, and chemicals, and mechanical injury.
It also regulates temperature and the amount of water released into the environment.
The skin’s color is created by special cells called melanocytes, which produce the pigment melanin.
Melanocytes are located in the epidermis.
Epidermis and Its Layer
"epi" coming from the Greek meaning "over" or "upon", is the outermost layer of the skin. It
forms the waterproof, protective wrap over the body's surface which also serves as a barrier to
infection and is made up of stratified squamous epithelium with an underlying basal lamina.
The epidermis contains no blood vessels, and cells in the deepest layers are nourished almost
exclusively by diffused oxygen from the surrounding air and to a far lesser degree by blood
capillaries extending to the outer layers of the dermis.
The main type of cells which make up the epidermis are Merkel cells, keratinocytes, with
melanocytes and Langerhans cells also present.
The epidermis can be further subdivided into the following
Stratum basale, also known as stratum germinativum, is the deepest layer, separated from the
dermis by the basement membrane (basal lamina) and attached to the basement membrane by
The cells found in this layer are cuboidal to columnar mitotically active stem cells that are
constantly producing keratinocytes. This layer also contains melanocytes.
Stratum spinosum, 8-10 cell layers, also known as the prickle cell layer contains irregular,
polyhedral cells with cytoplasmic processes, sometimes called “spines”, that extend outward and
contact neighboring cells by desmosomes. Dendritic cells can be found in this layer.
Stratum granulosum, 3-5 cell layers, contains diamond shaped cells with keratohyalin granules
and lamellar granules. Keratohyalin granules contain keratin precursors that eventually aggregate,
crosslink, and form bundles.
The lamellar granules contain the glycolipids that get secreted to the surface of the cells and function
as a glue, keeping the cells stuck together.
Stratum lucidum, 2-3 cell layers, present in thicker skin found in the palms and soles, is a thin clear
layer consisting of eleidin which is a transformation product of keratohyalin.
Stratum corneum, 20-30 cell layers, is the uppermost layer, made up of keratin and horny scales made
up of dead keratinocytes, known as anucleate squamous cells.
This is the layer which varies most in thickness, especially in callused skin. Within this layer, the dead
keratinocytes secrete defensins which are part of our first immune defence.
The dermis or corium is a layer of skin between the epidermis (with which it makes up the cutis)
and subcutaneous tissues.
That primarily consists of dense irregular connective tissue and cushions the body from stress and
strain. It is divided into two layers, the superficial area adjacent to the epidermis called the
papillary region and a deep thicker area known as the reticular dermis.
The papillary layer is the upper layer, thinner, composed of loose connective tissue and contacts
The reticular layer is the deeper layer, thicker, less cellular, and consists of dense connective
tissue/ bundles of collagen fibres. The dermis houses the sweat glands, hair, hair follicles,
muscles, sensory neurons, and blood vessels.
The dermis is tightly connected to the epidermis through a basement membrane. Structural
components of the dermis are collagen, elastic fibres, and extrafibrillar matrix.
It also contains mechanoreceptors that provide the sense of touch and thermo receptors that
provide the sense of heat. In addition, hair follicles, sweat glands, sebaceous glands (oil glands),
apocrine glands, lymphatic vessels, nerves and blood vessels are present in the dermis.
Those blood vessels provide nourishment and waste removal for both dermal and epidermal cells.
1. The subcutaneous tissue (also hypodermis and sub cutis) is not part of the skin, and lies below the
dermis of the cutis.
2. Its purpose is to attach the skin to underlying bone and muscle as well as supplying it with blood
vessels and nerves.
3. It consists of loose connective tissue, adipose tissue and elastin. The main cell types are
fibroblasts, macrophages and adipocytes (subcutaneous tissue contains 50% of body fat).
4. Fat serves as padding and insulation for the body.
Functions of Skin
Skin performs the following functions:
1. Protection: an anatomical barrier from pathogens and damage between the internal and external
environment in bodily defence; Langerhans cells in the skin are part of the adaptive immune
2. Perspiration contains lysozyme that break the bonds within the cell walls of bacteria.
3. Sensation: contains a variety of nerve endings that react to heat and cold, touch, pressure,
vibration, and tissue injury; see somatosensory system and haptics.
4. Heat regulation: the skin contains a blood supply far greater than its requirements which allows
precise control of energy loss by radiation, convection and conduction. Dilated blood vessels
increase perfusion and heat loss, while constricted vessels greatly reduce cutaneous blood flow
and conserve heat.
5. Control of evaporation: the skin provides a relatively dry and semi-impermeable barrier to fluid
loss. Loss of this function contributes to the massive fluid loss in burns.
6. Aesthetics and communication: others see our skin and can assess our mood, physical state and
7. Storage and synthesis: acts as a storage centre for lipids and water,as well as a means of synthesis
of vitamin D by action of UV on certain parts of the skin.
8. Excretion: sweat contains urea, however its concentration is 1/130th that of urine, hence excretion
by sweating is at most a secondary function to temperature regulation.
9. Absorption: the cells comprising the outermost 0.25–0.40 mm of the skin are "almost exclusively
supplied by external oxygen", although the "contribution to total respiration is negligible". In
addition, medicine can be administered through the skin, by ointments or by means of adhesive
patch, such as the nicotine patch or iontophoresis. The skin is an important site of transport in
many other organisms.
10. Water resistance: The skin acts as a water-resistant barrier so essential nutrients are not washed
out of the body.
Problems In Skin
Also called xerosis
Dry skin is common. It can occur at any age and for many reasons. Using a moisturizer often
helps repair dry skin.
Sometimes people need a dermatologist's help to get relief from dry skin. Extremely dry skin can
be a warning sign of a skin problem called dermatitis (derm-muh-TIE-tis).
Dermatitis means inflammation of the skin. It can cause an itchy rash or patches of dry irritated
skin. The earlier dermatitis is diagnosed and treated the better. Without treatment, dermatitis often
Your doctor may call dry skin xerosis.
SIGNS AND SYMPTOMS
The signs (what you see) and symptoms (what you feel) of dry skin are:
Rough, scaly, or flaking skin
Gray, ashy skin in people with dark skin
Cracks in the skin, which may bleed if severe
Chapped or cracked lips
When dry skin cracks, germs can get in through the skin. Once inside, germs can cause an
infection. Red, sore spots on the skin may be an early sign of an infection.
Anyone can get dry skin. Skin becomes dry when it loses too much water or oil. Some people are
more likely to have dry skin. Some causes of dry skin are:
Age: As we age, our skin becomes thinner and drier. By our 40s, many people need to use a good
moisturizer every day.
Climate: Living in a dry climate such as a desert.
Skin disease: People who had atopic dermatitis (also called eczema) as a child tend to have dry
skin as adults. Psoriasis also causes very dry skin.
Job: Nurses, hair stylists, and people in other occupations often immerse their skin in water
throughout the day. This can cause the skin to become dry, raw, and cracked.
Swimming: Some pools have high levels of chlorine, which can dry the skin.
Moisturizer: Applying a moisturizer frequently throughout the day can help. It can make the skin
softer, smoother, and less likely to crack. Body moisturizers come in a few forms — ointments,
creams, lotions, and oils. Your dermatologist can tell you which is recommended for you.
For very dry skin, a moisturizer that contains urea or lactic acid may be helpful. These ingredients
help the skin hold water. You can find these ingredients in both prescription moisturizers and
those that you can buy without a prescription. A drawback is that these ingredients can sting if
you have eczema or cracked skin.
Medicine: When skin is extremely dry, your dermatologist may prescribe a medicine that you can
apply to your skin. This may be a corticosteroid (cortisone-like) or an immune modulator
(tacrolimus, pimecrolimus). These medicines tend to be quite good at relieving the itch, redness,
and swelling. You also may need to use a moisturizer several times a day.
Changes to your day: If your dry skin is caused by something that you are doing, such as
immersing your hands in water all day, you may need to stop doing this for a few days. When you
start up again, you may need to wear gloves or apply a special moisturizer throughout the day.
1. Acne,also known as acne vulgaris, is a long-term skin disease that occurs when hair follicles are
clogged with dead skin cells and oil from the skin.
2. It is characterized by blackheads or whiteheads, pimples, oily skin, and possible scarring.
3. It primarily affects areas of the skin with a relatively high number of oil glands, including the
face,upper part of the chest,and back.
4. The resulting appearance can lead to anxiety, reduced self-esteem and, in extreme
cases, depression or thoughts of suicide.
Acne signs and symptoms vary depending on the severity
of your condition:
Whiteheads (closed plugged pores)
Blackheads (open plugged pores)
Small red, tender bumps (papules)
Pimples (pustules), which are papules with pus at their
Large, solid, painful lumps beneath the surface of the skin
Painful, pus-filled lumps beneath the surface of the skin
Anti-inflammatory - in joints and tissues.
Topical clindamycin and erythromycin are antibiotics that are also anti inflammatory drugs and
are effective against a number of bacteria. They should always be combined with benzoyl
peroxide or a topical retinoid and applied directly to the skin.
Vitamin A derivative Unplugs blocked hair follicles and helps prevent new blockages from
forming. Slows skin cell growth.
Antibiotics - Stops the growth of or kills bacteria. For moderate to severe acne, you may need
oral antibiotics to reduce bacteria and fight inflammation. Usually the first choice for
treatingacne is tetracycline — such as minocycline or doxycycline — or a macrolide.
Oral antibiotics should be used for the shortest time possible to prevent antibiotic resistance.
Topical antiseptic-Destroys or prevents the growth of microorganisms on the skin that may cause
Pigmentation or Hyperpigmentation
Hyperpigmentation is the darkening of an area of skin or nails caused by increased melanin.
Hyperpigmentation can be caused by sun damage, inflammation, or other skin injuries, including
those related to acne vulgaris.
People with darker skin tones are more prone to hyperpigmentation,
especially with excess sun exposure.
Many forms of hyperpigmentation are caused by an excess production of
Melanin is produced by melanocytes at the lower layer of the epidermis.
Melanin is a class of pigment responsible for producing colour in the body in
places such as the eyes, skin, and hair. As the body ages, melanocyte
distribution becomes less diffuse and its regulation less controlled by the
Most often treatment of hyperpigmentation caused by melanin overproduction (such as melasma,
acne scarring, liver spots) includes the use of topical depigmenting agents, which vary in their
efficacy and safety, as well as in prescription rules.
Several are prescription only in the US, especially in high doses, such as hydroquinone, azelaic
acid, and koijic acid.
Some are available without prescription, such as niacinamide, or cysteamine hydrochloride.
Hydroquinone was the most commonly prescribed hyperpigmentation treatment before the long-
term safety concerns were raised,and the use of it became more regulated in several countries and
discouraged in general by WHO
Oral medication with procyanidin plus vitamins A, C, and E also shows promise as safe and
effective for epidermal melasma.
Prickly Heat ( Heat Rash)
A skin condition caused by blocked sweat ducts and trapped sweat beneath the skin. Heat rash is
common during hot, humid weather
Skin: blister, bumps, rashes, or red rashes
Also common: flushing or itching
1. calamine lotion
2. antihistamine tablets
3. hydrocortisone cream – though not for children under 10 or pregnant women as they need to get
advice from a doctor before using this treatment
A wrinkle, also known as a rhytide, is a fold, ridge or crease in smooth surface, such as on skin or
Skin wrinkles typically appear as a result of aging processes such as glycation, habitual sleeping
positions, loss of body mass, sun damage, or temporarily, as the result of prolonged immersion in
In humans, it can also be prevented to some degree by avoiding excessive solar exposure and
through diet (in particular through consumption of carotenoids, tocophenols and flavonoids,
vitamins (A, C, D and E), essential omega-3-fatty acids, certain proteins and lactobacilli.
Topical retinoids. Derived from vitamin A, retinoids —
such as tretinoin (Renova, Retin-A) and tazarotene
(Avage, Tazorac) — that you apply to your skin may
reduce fine wrinkles, splotches and skin roughness
Because retinoids can make your skin burn more easily, you'll need to use a broad-spectrum
sunscreen and wear protective clothing daily. Retinoids may cause redness, dryness, itching, and a
burning or tingling sensation.
Surgical procedures and other techniques
Laser,light source and radiofrequency treatments
Botulinum toxin type A (Botox)
Odour caused by the combination of sweat and bacteria normally found on the skin.
Common causes of this symptom
Body odour can have causes that aren't due to underlying disease. Examples include poor hygiene,
hot and humid weather, recent exercise or eating certain foods such as onions and garlic
Using antiperspirant, deodorant and regular bathing with antibacterial soap may help to reduce
body odour. Avoiding spicy foods and caffeinated beverages may also help.
The hair follicle is one of the characteristic features of mammals serves as a unique
In humans, hair has various functions such as protection against external factors, sebum,
apocrine sweat and pheromones production and thermoregulation.
The hair also plays important roles for the individual’s social and sexual interaction.
The hair follicle serves as a reservoir for epithelial and melanocyte stem cells and it is
capable of being one of the few immune privileged sites of human body.
Hair follicle development is related to the interactions between epithelial and
Many genes play substantial role in this interaction and also in hair follicle cycling.
Classification of the hair
Nearly whole body surface is coated with the hairs except a few areas like palms, soles
and mucosal regions of lips and external genitalia.
Most of these are tiny, colourless vellus hairs.
The ones located in several areas like scalp, eyebrows and eyelashes are thicker, longer
and pigmented and are called terminal hairs.
Humans have approximately 5 million hair follicles and 100,000 of them are located on
1. Total count Almost 5,000,000
2. Scalp hair count 80,000–150,000
3. Hair cycle ratios of scalp hair Anagen: 85–90%
4. Duration of hair cycle phase
Anagen: 2–6 years
Catagen: 2–3 weeks
Telogen: 3 months
Physiologic hair shedding rate
6. Hair shaft production rate (scalp) ~0.35 mm/day, 1 cm/month
7. Hair shaft diameter and length Vellus: 0.06 mm; 1–2 mm
8. Hair patterns
Terminal: >0.06 mm; 1–50 cm
Pubic and axillary hair
9. Hair shaft pigmentation
Dark hair: predominance of eumelanin
Blond/red hair: predominance of pheomelanin
Structure of the hair
Hair is consisted of two distinct structures:
1. Hair Follicle—the living part located under the skin
2. Hair shaft—fully keratinized nonliving part above the skin surface.
Hair shaft is consisted of three layers:
Flat and square-shaped cuticle cells are adhered tightly to the cortex cells proximally.
By interlocking with the cuticle cells of inner root sheath, they contribute to the follicular
anchorage of the growing hair.
Cuticle has also important protective properties and barrier functions against physical and
The follicle is the essential growth structure of the hair and basically has two distinct parts:
1. upper part consisting of infundibulum and isthmus
2. lower part comprising of hair bulb and suprabulbar region.
The upper follicle remains constant, while the lower part has continuous cycles of
Molecular structure of Hair
Keratin proteins can be divided into two major families:
The type I (acidic) keratins
The type II (basic-neutral) keratins.
About 54 functional keratin genes (28 type I and 26 type II keratins) have been identified
There are 11 type I hair keratins, designated K31–K40, and 6 type II hair keratins,
designated K81–K86, and the remainder are epithelial keratins.
The keratin-associated proteins (KAP), is a large group of proteins which constitutes the
matrix of the keratin.
The matrix proteins are separated to three major subgroups according to their amino acid
Different hair and epithelial keratins are expressed in the various concentric layers of the
hair follicle, with hair keratins found primarily in the cortex and hair cuticle.
Hair growth cycle
Hair development is a continuous cyclic process and all mature follicles go through a
growth cycle consisting of
1. Growth (Anagen),
2. Regression (Catagen),
3. Rest (Telogen)
4. Shedding (Exogen) Phases.
The duration of the phases changes based on the location of the hair and also personal
nutritional and hormonal status and age
The anagen is the active growth phase in which the follicle enlarges and takes the original
shape and the hair fiber is produced.
Almost 85–90% of all scalp hairs are in anagen.
This phase can last up to 6–8 years in hair follicles
Catagen lasts approximately 2 weeks in humans, regardless of the site and follicle type.
During catagen the proximal of the hair shaft is keratinized and forms the club hair,
whereas the distal part of the follicle is involuted by apoptosis
Catagen phase is consisted of eight different stages. The first sign of catagen is the
termination of melanogenesis in the hair bulb.
However, any apoptosis is occurred in dermal papilla due to the expression of suppressor
The telogen stage is defined as the duration between the completion of follicular
regression and the onset of the next anagen phase.
Telogen stage lasts for 2–3 months.
Approximately 10–15% of all hair is in telogen stage. During the telogen stage, the hair
shaft is transformed to club hair and finally shed.
The follicle remains in this stage until the hair germ which is responsive to anagen
initiating signals from the dermal papilla, starts to show enhanced proliferative and
transcriptional activity in late telogen, leading to the initiation of anagen
There is less interest for the mechanism of the hair shedding but from the patient’s
perspective it is probably the most important part of the hair growth.
It is not unusual for human telogen hairs to be retained from more than one follicular
cycle and this suggests that anagen and exogen phases are independent.
The shedding period is believed to be an active process and independent of telogen and
anagen thus this distinct shedding phase is named exogen.
1. Yousef H, Alhajj M, Sharma S. Anatomy, Skin (Integument), Epidermis. [Updated 2019 Jun 12].
In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from:
6. Martel JL, Badri T. Anatomy, Hair Follicle. [Updated 2019 Jan 30]. In: StatPearls [Internet].
Treasure Island (FL): StatPearls Publishing; 2019 Jan.
8. Bilgen Erdoğan (May 3rd 2017). Anatomy and Physiology of Hair, Hair and Scalp Disorders,
Zekayi Kutlubay and Server Serdaroglu, IntechOpen, DOI: 10.5772/67269. Available from: