The document discusses the structure and function of the skin. It describes the three main layers of the skin - the epidermis, dermis, and hypodermis. The epidermis is made of epithelial cells and protects the body. The dermis contains connective tissue, hair follicles, and sweat and sebaceous glands. The hypodermis contains fat and cushions internal organs. It also discusses common skin conditions like acne, eczema, seborrheic dermatitis, and skin cancers.

1. BARKHA SARMA
B.PHARM 3rd year
16HPH012
PHARMA CEUTICS VI

2.  Skin is the soft outer covering and is one of the largest organ
of the body.
 It is made up of different tissues that are joined to perform a
specific function.
 It covers the surface area of 20-22 sq. ft.
 Thickness varies from 3-3.5mm.
 CLASSIFICATION-
 Skin is broadly divided into three types-
1)Epidermis which is made up of
epithelial cells.
2)Dermis which is made up of
connective tissues.
3)Hypodermis which is a subcutaneous
tissue.

3.  Skin contains subcutaneous tissue which is essentially
fat which helps in the storage of fat and participates in
thermal regulation.
 There are blood vessels inside the layers of skin.
 Hair follicles are also present which is connected to the
sebaceous gland.
 Sebaceous gland is present all over the body except for
palms of hands and soles of feet and it secretes sebum
which lubricates our hair.
 It also acts as defence mechanism against pathogens.
 Within the sebaceous gland or residing around the hair
follicle there is commensal pathogen of hair follicle and
sebaceous gland.

4.  These are rod shaped bacteria called Propionii
bacterium, which is a gram positive.
 It is stimulated by some hormones like Androgens and
Testosterone which helps in the secretion of sebum and
hypertrophy of sebaceous gland.
 Connected to the hair follicle there is a erector pilli
muscle, this muscle pulls the hair follicle.
 The phenomenon called goose bumps is due to the
erector pilli contracting our hair follicle to stick
upwards.

5.  Another important gland is the sweat gland which
secretes sweat.
 Sweat gland is of two types-
 1) Eccrine gland- it is found in the palms of
hands and soles of feet.
 2) Apocrine gland- it is found in the
auxiliary and endogenital area which functions only after
puberty.

6.  The skin is the largest organ in our body. The skin
provides-
 Protection from environment (Abrasion, fluid loss)
 Containment from bodies structures and vital organs.
 Heat Regulation – sweat, dilation and constriction of
blood vessels.
 Sensation
 Synthesis and storage of vitamin D
 Blood reservoir
 Excretion of unwanted substances through sweat.

7. EPIDERMIS
 In epidermis layer there is a basement membrane
which in the upward direction is connected to epithelial
cells and in the downward direction is connected to the
connective tissues of the dermis.
 The very first layer of the epidermis closest to the dermis
is the stratum basili where we have epithelial cells that
are dividing and some of these new cells will move
upwards and these cells are able to divide because they are
receiving blood vessels from the dermis and so as they
divide some of the cells will migrate up to the top of the
epidermis.
 To the top of stratum basili is the stratum spinosum
where the epithelial cells are becoming keratinized
because they are not receiving any blood vessels or blood
supply. There are also other cells found in this area

8. called the melanocytes, which produces a substance
called melanin which is responsible for skin colour.
Other cells found in this area is the dendritic cells
which helps in the capturing of the foreign particles.
 Next layer is the stratum granulosum where the cells
began to die or they start becoming flattened and the
organelles within the cells are being destroyed.
 The fourth layer is the stratum lucidum where all the
dead cells are present and are more flattened.
 The fifth layer is stratum corneum where the old cells
are being shed off and they are super thin. Eg- if you are
rubbing your arm you are actually shedding off your
stratum corneum.

9. DERMIS
 The reticular dermis is the deeper and thicker layer of the
dermis, which lies above the subcutaneous layer of the skin.
 It contains dense connective tissue, which includes blood
vessels.
 It is the thickest layer of the skin, and is made up of fibrous
and elastic tissue. Thus it provides strength and flexibility to
the skin.
 The dermis is comprised of two layers – 1)Papillary dermis
2)Reticular dermis
 The primary role of the dermis is to support the epidermis
and enable the skin to thrive. It also plays a number of other
roles due to the presence of nerve endings, sweat glands,
sebaceous glands, hair follicles and blood vessels

11. HYPODERMIS
 The innermost layer of the skin, which helps to insulate
the body and cushion internal organs.
 The hypodermis consists of well- vascularized, loose,
areolar connective tissue and adipose tissue, which
functions as a mode of fat storage.
 The hypodermis is home to most of the fat that concerns
people when they are trying to keep their weight under
control.
 Adipose tissue present in the hypodermis consists of fat
storing cells called adipocytes.

13. DISEASE RELATED TO SKIN
1)Acne-
 Acne is a skin disorder that causes pimples when the
passageway that connects the skins pores to the oil
glands become clogged.
 Acne, which appears most often on the face, neck,
shoulders, chest and back, can come in many forms.
 Whiteheads and blackheads are the most commonly
known, nodular and cystic acne are more severe because
they from deep in the skin and cause scars.

15. 2) Eczema-
 Eczema is a “grab-bag term” , which comes from the
Greek word for “boils over”.
 There are three common forms of eczema:
Atopic dermatitis is the most common and is seen most
often in children. It is a genetic disease, which causes
itchy rashes in the crux of the elbows and behind the
knees.
Allergic contact dermatitis begins to show in adulthood
and is caused by environmental factors such as cosmetic
agents, fragrances and the metals in jewellery.
Nummular dermatitis looks like red and flaky coin
shaped patches of skin and is due to dry skin. This can be
very itchy.

16. 3)Seborrheic Dermatitis-
 Seborrheic dermatitis, which causes oily, waxy patches to
develop on the scalp, is distinct from other forms of
dermatitis.
 It can affect babies, typically in the first six months of their
lives in the form of “cradle cap” – a flakey, dandruff like
condition on the scalp. After the symptoms clear up, it rarely
appears again until puberty.
4)Skin Cancer-
 Skin cancer is the most common type of cancer in the United
States.
 Basal cell carcinoma and squamous cell carcinoma are the
most common types of skin cancer.
 But 75% of skin cancer deaths are from melanoma, the third
most common form.