The skin has three layers - the epidermis, dermis, and subcutaneous tissue. The epidermis is made of stratified squamous epithelium and contains keratinocytes that produce keratin, and melanocytes that produce melanin pigment. The dermis lies below the epidermis and contains collagen, elastic fibers, and sensory receptors. The deepest layer, the subcutaneous tissue, contains fat and connective tissue. Skin has appendages like hair follicles, sebaceous glands, sweat glands, and nails. The skin acts as a barrier and regulates body temperature, and contains sensory receptors for touch, pressure, and temperature.

1. ANATOMY OF
SKIN
& PHYSIOLOGY
OF TOUCH
AY

2. The skin is also known as cutaneous membrane
or in tegument, covers the external surface of the
body
It is a sensory organ which is a largest organ of
the body in both surface area and weight
Integumentary system is composed of skin, hair,
nails, glands pH - 4 to 5.6

3. STRUCTURE OF SKIN

4. Epidermis; - Superficial layer of
the skin - composed of epithelial
tissue
Dermis; - The deeper layer of the
skin - primarily composed of
connective tissue
Subcutaneous tissue Deep to the
dermis is the subcutaneous layer
or hypodermis - It consists of
areolar and adipose tissue
THREE LAYERS OF SKIN

7. Epidermis
The epidermis, the thin
avascular superficial layer
of the skin, is made up of
an outer dead cornified
portion that serves as a
protective barrier and a
deeper, living portion that
folds into the dermis.
Together these layers
measure 0.05 to 0.1 mm in
thickness.
The epidermis regenerates
with new cells every 28
days.

8. Stratum corneum =
many layers of flat,
dead, scale like cells
full of keratin
Stratum lucidum =
one or two layers of
dying cells
Stratum
Granulosum = Three
or four layers of skin;
actively synthesizing
protein keratin
Stratum spinosum =
three or four layers of
cells with some cell
division
Stratum Basale =
Single row of dividing
cells (columnar cells)
Epidermis

10. 1. The two major types of epidermal cells are
melanocytes (5%) and keratinocytes (90%).
2. Melanocytes are contained in the deep, basal
layer (stratum germinativum) of the epidermis.
3. They contain melanin, a pigment that gives
color to the skin and hair and protects the
body from damaging ultraviolet (UV) sunlight.
Cells of Epidermis:

11. • Keratin cutes which produce a large
amount of protein keratin Other cell
types ;
• Melanocytes produce pigment melanin &
transfer it to keratinocytes Langerhans
cells(immune cells) protect against
pathogens and toxins

12. 1. Sunlight and hormones stimulate
the melanosome (within the
melanocyte) to increase the
production of melanin.
2. The wide range of skin color is
caused by the amount of
melanin produced; more melanin
results in darker skin color.

13. 1. Keratinocytes are synthesized from
epidermal cells in the basal layer.
2. As they mature (keratinize), they move
to the surface, where they flatten and die
to form the outer skin layer (stratum
corneum).
3. Keratinocytes produce a fibrous protein,
keratin, which is vital to the skin’s
protective barrier function.

15. Dense irregular connective tissue Separated
from epidermis (stratified squamous
epithelium) by basement membrane
Highly vascular
Highly innervated
Two layers ; Papillary layer just below
epidermis Reticular layer forms deep 80 %
DERMIS

16. Contains many types of sensory receptors for touch , pressure,
vibration, pain , temperature etc .
Papillary layer is folded into ridges which extend into upper
epidermal layer.
The exposed ridges form congenital patterns called finger prints
and foot prints
Reticular layer contains collagen Elastic and reticular fibers
Dermis

18. Lies below the dermis and is not part of skin.
It attaches the skin to underlying tissue such as muscle and bone.
The subcutaneous tissue contains loose fat cells, that provide insulation.
The anatomic distribution of subcutaneous tissue varies according to
gender, hereditary, age, nutritional status.
Thus, layer also stores lipids, regulates temperature, and provides shock
absorption.
SUBCUTANEOUS TISSUE

19. Hair follicle
and Hair
Sweat and
sebaceous
glands
Nails on
fingers and
toes
APPENDAGES OF SKIN

20. Hair is composed primarily of keratin.
The 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.
Lengthening fibers of keratin-filled dead cells, grouped around the semi
hollow medulla, make up the cortex.
HAIR FOLLICLE AND HAIR

21. A living structure called the bulb (visible as a white
lump at the end of a plucked hair) surrounds and
feeds the root, which lies in a pocket of the
epidermis called the follicle.
Each hair follicle also contains the 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.

22. - The color of hair is due to melanin.
- Dark hair contains true melanin like that found in
the skin.
- Blond and red hair result from types of melanin
that contain sulfur and iron.
- Hair goes gray when melanocytes age and lose
the enzyme necessary to produce melanin. White
hair occurs when air bubbles become incorporated
into the growing hair.

23. 1. An adult human has between 1.6 to 4 million
sudoriferous glands, or sweat glands.
2. Most are of a type known as eccrine sweat
glands, which are found almost all over the
surface of the body and are most numerous on
the palms and soles.
3. Eccrine sweat glands begin deep in the dermis
and connect to the surface of the skin by a
coiled duct.
4. In addition, nerve fibers that encircle the
sweat glands stimulate the glands in response
to fear, excitement, or anxiety.
Sweat and Sebaceous Gland

24. 1. Nails on the fingers and toes are made of hard, keratin-
filled epidermal cells.
2. They protect the ends of the digits from injury, help us
grasp small objects, and enable us to scratch.
3. The part of the nail that is visible is called the nail
body or nail plate, and the portion of the nail body that
extends past the end of the digit is called the free edge.
4. The nail groove is the fold on the side and the
eponychium is the skin that holds the nail root.
Nails on fingers and toes

26. Most of the nail body appears pink because of blood flowing in the
tissue underneath.
The pale, semicircular area called the lunula appears white due to an
underlying thick layer of epidermis that does not contain blood
vessels.
The part of the nail that is buried under the skin is called the root.
Nails grow as epidermal cells below the nail root and transform into
hard nail cells that accumulate at the base of the nail, pushing the rest
of the nail forward.

27. 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.

28. Apocrine sweat glands are located mainly in the armpit, genital
area, and around the nipples of the breasts.
Oil, or sebaceous, glands are found all over the body except on
the palms, the soles, and the top of the feet.
They 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.

29. Glands of this type produce an oily substance
called sebum, which keeps the skin and hair from
drying out and inhibits the growth of certain
harmful bacteria.
Wax, or ceruminous, glands are located in the ear
canal. They secrete a waxy substance that helps
prevent foreign particles from entering the ear.
Ceruminous glands are modified sweat glands.

30. Skin controls heat
regulation by
responding to changes
in temperature with
vasoconstriction and
vasodilatation
Helps to maintain
homeostasis through
fluid and electrolyte
balance
Sebum and Sweat are
secreted by skin and
lubricate skin surface
Endogenous synthesis
of vit-D, which is critical
to calcium and
potassium balance,
occurs in epidermis
Functions of skin

31. Vit -D synthesized by action of UV lights in vit -D precursor in
epidermal cells
The aesthetic function of skin include the expression of various
emotions such as anger or embarrassment, as well as displaying the
individual identity of a person
Skin with its nerve endings and special receptor provide s sensory
perception for environmental stimuli.
These highly specialized nerve endings supply information to brain
related to pain, heat and cold, touch, pressure, vibration. .