The integumentary system consists of the skin and its accessory structures. The skin is the largest organ of the body and has several layers, including the epidermis and dermis. The epidermis is made of stratified squamous epithelium with keratinocytes that produce keratin. The dermis contains collagen, fibers and structures like hair follicles. Accessory structures include hair, nails, and glands. Hair provides protection while glands like sebaceous glands secrete oils to moisturize the skin. The integumentary system acts as a barrier and helps regulate body temperature.

1. INTEGUMENTARY
SYSTEM

2. INTRODUCTION
• The integumentary system is composed of the
skin and its accessory structures including
hair, nails, oil and sweat glands and sensory
receptors as well as blood vessels and nerves.
• Contributes to homeostasis by helping
regulate body temperature.
• Dermatology the medical science that deals
with the diagnosis and treatment of
integumentary system disorders.

3. INTRODUCTION
• It is a largest organ system of the body in both
surface area and weight.
• Contain about 10 % of total body weight.
• In adults, the skin covers an area of about 2
square meters (22 square feet).
• Average thickness is 1-2 mm

4. STRUCTURE OF THE SKIN
• The skin consists of two main parts-
• 1. Cutaneous membrane-
• The superficial thinner portion, which is composed
of epithelial tissue, is the epidermis.
• The deeper, thicker connective tissue portion is the
dermis.
• 2. Accessory structures – Hair, nails, exocrine glands
• Deep to the dermis, but not part of the skin, is the
subcutaneous layer. Also called the hypodermis this
layer consists of areolae and adipose tissues.

6. Epidermis
• Composed of keratinized stratified squamous
epithelium.
• It contains four types of cells: keratinocytes,
melanocytes, Langerhans cells, and Merkel cells.
• About 90% of epidermal cells are keratinocytes
which are arranged in four or five layers and produce
the protein keratin.
• Keratin is a tough, fibrous protein that helps protect
the skin and underlying tissues from abrasions, heat,
microbes, and chemicals.
• Keratinocytes also produce lamellar granules, which
release a water-repellent sealant that decreases
water entry , loss and inhibits the entry of foreign
materials.

8. • About 8% of the epidermal cells are melanocytes,
which produce the pigment melanin
• Melanin is a yellowed or brown-black pigment
that contributes to skin color and absorbs
damaging ultraviolet (UV) light.
• Langerhans cells, also called epidermal dendritic
cells, arise from red bone marrow and migrate to
the epidermis. They participate in immune
responses.
• Merkel cells are located in the deepest layer of
the epidermis, where they contact the sensory
neuron, a structure called a Merkel (tactile) disc.
Merkel cells and their associated Merkel discs
detect touch sensations.

9. • In most regions of the body the epidermis has
four strata or layers— stratum basale,
stratum spinosum, stratum granulosum, and
a thin stratum corneum. This is called thin
skin.
• Where exposure to friction is greatest, such as
in the fingertips, palms, and soles, the
epidermis has five layers— stratum basale,
stratum spinosum, stratum granulosum,
stratum lucidum, and a thick stratum
corneum. This is called thick skin.

11. • Stratum Basale- The deepest layer of the
epidermis, composed of a single row of cuboidal
or columnar keratinocytes.
• Some cells in this layer are stem cells that
undergo cell division to continually produce new
keratinocytes
• keratinocytes of the stratum basale includes
scattered intermediate filaments, called keratin
intermediate filaments.
• The keratin intermediate filaments form the
tough protein keratin.
• Melanocytes and Merkel cells with their
associated Merkel discs are scattered among the
keratinocytes of the basal layer.

12. • Stratum Spinosum- Superficial to the stratum
basale is the stratum spinosum.
• Consists of numerous keratinocytes arranged
in 8–10 layers.
• The keratinocytes of this layer produce
bundles of keratin in intermediate filaments
• Contains armlike projections of melanocytes
and Langerhans cells.

13. • Stratum Granulosum- consists of three to five
layers of flattened keratinocytes that are
undergoing apoptosis.
• In which nuclei and other organelles of these
cells begin to degenerate, become dead.
• cells contain the protein keratohyalin (cross
linking of keratin filaments which creates the
tight barrier which protects the body from
foreign particles) and lamellar granules
(release lipid-rich, water-repellent secretion).

14. • Stratum Lucidum- The stratum lucidum is
present only in the thick skin of areas such as
the fingertips, palms, and soles.
• It consists of four to six layers of flattened
clear, dead keratinocytes that contain large
amounts of keratin.
• Provides an additional level of toughness in
this region of thick skin.

15. • Stratum Corneum- consists on average of 25
to 30 layers of flattened dead keratinocytes
• The cells are extremely thin, flat, plasma
membrane–enclosed packages of keratin that
no longer contain a nucleus or any internal
organelles.
• In this outer stratum of the epidermis, cells
are continuously replaced by cells from the
deeper strata.

16. Dermis
• The second, deeper part of the skin, the dermis,
is composed of dense irregular connective tissue.
• The dermis also has the ability to stretch and
recoil easily.
• Cells present few fibroblasts, macrophages and
adipocytes.
• Blood vessels, nerves, glands, and hair follicles
are embedded in the dermal layer.
• Based on its tissue structure, the dermis can be
divided into a thin superficial papillary region and
a thick deeper reticular region.

17. • The papillary region consists of thin collagen and
fine elastic fibers.
• Contain Dermal papillae small structures that
project into the undersurface of the epidermis.
All dermal papillae contain capillary loops (blood
vessels).
• Some also contain tactile receptors called
Meissner corpuscles or corpuscles of touch, nerve
endings that are sensitive to touch.
• Dermal papillae also contain free nerve endings,
initiate signals that give rise to sensations of
warmth, coolness, pain, tickling, and itching.

18. • The reticular region which is attached to the subcutaneous
layer, consists of bundles of thick collagen fibers, scattered
fibroblasts, and macrophages.
• Some adipose cells can be present in the deepest part of the
layer, along with some coarse elastic fibers.
• The collagen fibers in the reticular region are arranged in a
netlike manner and have a more regular arrangement than
those in the papillary region, which helps the skin resist
stretching.
• Blood vessels, nerves, hair follicles, sebaceous (oil) glands,
and sudoriferous (sweat) glands occupy the spaces between
fibers.
• The combination of collagen and elastic fibers in the reticular
region provides the skin with strength, extensibility and
elasticity.

20. ACCESSORY STRUCTURES OF
THE SKIN
• Accessory structures of the skin—
• Hair, skin glands, and nails
• Develop from the embryonic epidermis.
• They have a host of important functions.
• For example, hair and nails protect the body,
and sweat glands help regulate body
temperature.

21. Hair
• Hairs, or pili, are present on most skin surfaces
except the palms, fingers, the soles, and feet.
• In adults, hair is most heavily distributed
across the scalp, in the eyebrows, in the
axillae (armpits), and around the external
genitalia.
• Genetic and hormonal influences largely
determine the thickness and the pattern of
hair distribution.

22. • Functions of Hair-
• Hair on the head guards the scalp from injury and
the sun’s rays. It also decreases heat loss from the
scalp.
• Eyebrows and eyelashes protect the eyes from
foreign particles, similar to the way hair in the
nostrils and in the external ear canal defends
those structures.
• Touch receptors associated with hair follicles are
activated whenever a hair is moved even slightly.
Thus, hairs also function in sensing light touch.

23. Structure of a Hair
• Each hair is composed of columns of dead, keratinized
epidermal cells bonded together by extracellular proteins.
• The shaft is the superficial portion of the hair, which
projects above the surface of the skin.
• The root is the portion of the hair deep to the shaft that
penetrates into the dermis, and sometimes into the
subcutaneous layer.
• The shaft and root of the hair both consist of three
concentric layers of cells: medulla, cortex, and cuticle of the
hair.
• The inner medulla, is composed of two or three rows of
irregularly shaped cells that contain pigment granules.

24. • The middle cortex forms the major part of the
shaft and consists of elongated cells.
• The cuticle of the hair, the outermost layer,
consists of a single layer of thin, flat cells that are
the most heavily keratinized.
• Surrounding the root of the hair is the hair
follicle which is made up of an external root
sheath and an internal root sheath, together
referred to as an epithelial root sheath.
• The dense dermis layer surrounding the hair
follicle is called the dermal root sheath.
• The base of each hair follicle and its surrounding
dermal root sheath is an onion-shaped structure,
called the bulb.

26. • Centre of bulb called the papilla of the hair,
which contains areolar connective tissue and
many blood vessels that nourish the growing
hair follicle.
• The bulb also contains a germinal layer of cells
called the hair matrix.
• Hair matrix cells are responsible for the
growth of existing hairs, and they produce
new hairs when old hairs are fall.
• This replacement process occurs within the
same follicle.

27. • Sebaceous (oil) glands and a bundle of smooth
muscle cells are also associated with hairs.
• The smooth muscle is the arrector pili. It extends
from the superficial dermis of the skin to the
dermal root sheath around the side of the hair
follicle.
• Under physiological or emotional stress, such as
cold or fright, autonomic nerves stimulate the
arrector pili muscles to contract, which pulls the
hair shafts perpendicular to the skin surface
• Surrounding each hair follicle are dendrites of
neurons that form a hair root plexus, which is
sensitive to touch.

29. Skin Glands
• Several kinds of exocrine glands are associated
with the skin:
• Sebaceous (oil) glands,
• Sudoriferous (sweat) glands, and
• Ceruminous glands.
• Mammary glands, which are specialized
sudoriferous glands that secrete milk.

30. Sebaceous Glands
• Sebaceous glands or oil glands are simple, branched rounded glands.
• With few exceptions, they are connected to hair follicles.
• The secreting portion of a sebaceous gland lies in the dermis and usually
opens into the neck of a hair follicle.
• In some locations, such as the lips, glans penis, labia minora, and tarsal
glands of the eyelids, sebaceous glands open directly onto the surface of
the skin.
• Absent in the palms and soles, sebaceous glands are small in most areas of
the trunk and limbs, but large in the skin of the breasts, face, neck, and
superior chest.
• Sebaceous glands secrete an oily substance called sebum, a mixture of
triglycerides, cholesterol, proteins, and inorganic salts.
• Sebum coats the surface of hairs and helps keep them from drying.
• Sebum also prevents excessive evaporation of water from the skin, keeps
the skin soft and inhibits the growth of some bacteria.

31. Sudoriferous Glands
• There are three million to four million sweat
glands, or sudoriferous glands in the body.
• The cells of these glands release sweat, or
perspiration, into hair follicles or onto the skin
surface through pores.
• Sweat glands are divided into two main types,
eccrine and apocrine, based on their structure
and type of secretion.

32. • Eccrine sweat glands are simple, coiled tubular glands that are
much more common than apocrine sweat glands.
• They are distributed throughout the skin of most regions of the
body, especially in the skin of the forehead, palms, and soles.
• Eccrine sweat glands are not present, in the margins of the lips, nail
beds of the fingers and toes, glans penis, glans clitoris, labia minora.
• The secretory portion of eccrine sweat glands is located mostly in
the dermis. The excretory duct open as a pore at the surface of the
epidermis.
• The sweat produced by eccrine sweat glands (about 600 mL per
day) consists of water, ions (mostly Na and Cl–), urea, uric
• acid, ammonia, amino acids, glucose, and lactic acid.
• The main function of eccrine sweat glands are- is to help regulate
body temperature through evaporation.
• The sweat produced by eccrine sweat glands also plays a small role
in eliminating wastes such as urea, uric acid, and ammonia etc.

33. • Apocrine sweat glands are also simple, coiled tubular
glands.
• They are found mainly in the skin of the axilla (armpit),
groin, breasts, and bearded regions of the face in adult
males.
• These glands release their secretions in an apocrine
manner.
• The secretory portion of these sweat glands is located
in the lower dermis and the excretory duct opens into
hair follicles.
• Apocrine sweat contains the same components as
eccrine sweat plus lipids and proteins.
• Eccrine sweat glands start to function soon after birth,
but apocrine sweat glands do not begin to function
until puberty.

34. Ceruminous Glands
• Modified sweat glands in the external ear, called
ceruminous glands, produce a waxy lubricating secretion.
• The secretory portions of ceruminous glands lie in the
subcutaneous layer, deep to sebaceous glands.
• Their excretory ducts open either directly onto the surface
of the external auditory canal (ear canal) or into ducts of
sebaceous glands.
• The combined secretion of the ceruminous and sebaceous
glands is a yellowish material called cerumen, or earwax.
• Cerumen, together with hairs in the external auditory
canal, provides a sticky barrier that prevent the entrance of
foreign bodies and insects.
• Cerumen also waterproofs the canal and prevents bacteria
and fungi from entering cells.

35. FEATURE SEBACEOUS (OIL)
GLANDS
ECCRINE SWEAT
GLANDS
APOCRINE SWEAT
GLANDS
CERUMINOUS GLANDS
Distribution Largely in lips, glans
penis, labia minora, and
tarsal glands; small in
trunk and limbs; absent
in palms and soles.
Throughout skin of
most regions of body,
especially skin of
forehead, palms, and
soles.
Skin of axillae, groin,
bearded regions of face,
clitoris, and labia
minora.
External auditory canal.
Location of secretary
portion
Dermis. Mostly in deep dermis
(sometimes in upper
subcutaneous layer).
Mostly in deep dermis
and upper
subcutaneous layer.
Subcutaneous layer.
Termination of
excretory duct
Mostly connected to
hair follicles.
Surface of epidermis. Hair follicle. Surface of external
auditory canal or into
ducts of sebaceous
glands.
Secretion Sebum (mixture of
triglycerides,
cholesterol, proteins,
and inorganic salts).
Perspiration, which
consists of water, ions
(Na, Cl), urea, uric acid,
ammonia, amino acids,
glucose, and lactic acid.
Perspiration, which
consists of same
components as eccrine
sweat glands plus lipids
and proteins.
Cerumen, a waxy
material.
Functions Prevent hairs from
drying out, prevent
water loss from skin,
keep skin soft, inhibit
growth of some
bacteria.
Regulation of body
temperature, waste
removal, stimulated
during emotional stress.
Stimulated during
emotional stress and
sexual excitement.
Prevent entrance of
foreign bodies and
insects into external ear
canal, waterproof canal,
prevent microbes from
entering cells.
Onset of function Relatively inactive
during childhood;
Soon after birth. Puberty. Soon after birth.

36. Nails
• Nails are plates of tightly packed, hard, dead,
keratinized epidermal cells that form a clear,
solid covering over distal portion of
(Phalanges).
• Each nail consists of a nail body, a free edge,
and a nail root.
• The nail body (plate) is the visible portion of
the nail. It consists of flattened, keratinized
cells fill with a harder type of keratin.
• Below the nail body is a region of epithelium
and a deeper layer of dermis.
• Most of the nail body appears pink because
of blood flowing through the capillaries in the
underlying dermis.
• The free edge is the part of the nail body that
may extend past the distal end of the digit.
• The free edge is white because there are no
underlying capillaries.

37. • The nail root is the portion of the nail that is placed in a
fold of skin.
• The whitish, crescent-shaped area of the proximal end of
the nail body is called the lunula.
• It appears whitish because the vascular tissue
underneath does not show through due to a thickened
region of epithelium in the area.
• Beneath the free edge is a thickened region of stratum
corneum called the hyponychium, or nail bed, which
secures the nail to the fingertip.
• The eponychium or cuticle is a narrow band of epidermis
that extends from and adheres to the margin (lateral
border) of the nail wall. It occupies the proximal border
of the nail and consists of stratum corneum.
• Deep to the nail root is the nail matrix. The nail matrix
cells divide mitotically to produce new nail cells.

39. Functions:
• They protect the distal end of the digits.
• Enhance touch perception of the fingers
• They allow us to grasp and manipulate small
objects

40. FUNCTIONS OF THE SKIN
• Thermoregulation- thermoregulation is the homeostatic
regulation of body temperature. The skin contributes to
thermoregulation in two ways: by liberating sweat at its
surface and by adjusting the flow of blood in the dermis.
• Blood Reservoir- The dermis houses an extensive
network of blood vessels that carry 8–10% of the total
blood flow in a resting adult.
• Cutaneous Sensations- Cutaneous sensations are
sensations that arise in the skin, including tactile
sensations—touch, pressure, vibration, and tickling—as
well as thermal sensations such as warmth and coolness.
Another cutaneous sensation, pain, usually is an
indication of tissue damage.

41. • Protection- The skin provides protection to the body in
various ways.
• Keratin protects underlying tissues from microbes,
abrasion, heat, and chemicals.
• Lipids released by lamellar granules inhibit evaporation
of water from the skin surface, thus guarding against
dehydration.
• The oily sebum from the sebaceous glands keeps skin
and hairs from drying out and contains bactericidal
chemicals.
• The acidic pH of perspiration retards the growth of some
microbes.
• The pigment melanin helps shield against the damaging
effects of ultraviolet light.
• Langerhans cells and macrophages carry immunological
functions.

42. • Excretion and Absorption- The skin normally
has a small role in excretion and absorption.
• Through sweating removing water and heat
from the body, sweat also is the vehicle for
excretion of small amounts of salts, CO2, and
organic molecules like ammonia and urea.
• Certain lipid-soluble materials do penetrate
the skin. These include fat-soluble vitamins (A,
D, E, and K), certain drugs, and the gases O2
and CO2. Some toxic material also absorb
from skin.

43. • Synthesis of Vitamin D- Synthesis of vitamin D
requires activation of a precursor molecule in
the skin by ultraviolet (UV) rays in sunlight.
• Enzymes in the liver and kidneys then modify
the activated molecule, finally producing
calcitriol, the most active form of vitamin D.
• Calcitriol is a hormone that aids in the
absorption of calcium from foods in the
gastrointestinal tract into the blood.
• Only a small amount of exposure to UV light is
required for vitamin D synthesis.

44. QUESTION BANK
• 2 Marks
1. Define integumentary system and dermatology
2. Enlist structure of skin.
3. Enlist different types of cells present in epidermis layer
4. Draw a structure of different types of layers present in skin/epidermis.
5. Draw a neat and label diagram of dermis.
6. List out function of skin
7. Write function of papilla of hair and hair matrix
8. Give 2 functions of hairs.
9. Draw a label diagram of hair follicles
10. List down different types of glands present in skin.
11. What do you mean by sebaceous gland.
12. Write down components of sweat secreted by apocrine & eccrine gland.
13. Where the apocrine and eccrine glands present in the skin?

45. Cont..
14. Write any 2 functions of sweat glands.
15. What do you mean by ceruminous gland and they secrete?
16. Define nails and enlist its parts.
17. Why lunula appears whitish in color?
18. Give 2 functions of nails?
10 MARKS :
1. Write structure and functions of skin?
2. Explain in brief about Sebaceous gland ,Sweat glands and Ceruminous gland?
5 Marks :
1. Discuss Epidermis with neat and label diagram.
2. Explain structure of Skin with suitable diagram.
3. Explain structure and function of Hair with label diagram.
4. Write a short note on Nails.
5. Discuss different types of Sweat Glands present in Skin?
6. Exlain function of Skin