The integumentary system consists of the skin and its appendages. The skin is made up of two layers - the epidermis and dermis. The epidermis is avascular and composed of stratified squamous epithelium in five layers. The dermis lies below and contains blood vessels, hair follicles, and glands. Functions of the skin include protection, regulation of temperature and moisture, synthesis of vitamin D, and sensation. Sweat glands and sebaceous glands are important appendages that aid temperature regulation and protect the skin surface.

1. INTEGUMENTARY SYSTEM
BY
SONI KUMARI SHAH

2. Integumentary System
Integumentary system is an organ of our body which protects the body
from damage.
It consists of skin and its appendages which are nails, hair, sweat gland
and sebaceous gland.

3. Functions Of Integumentary System
It protects the underlying structures from injury and from invasion by microbes.
It contains sensory nerve endings that enable discrimination of pain,
temperature and touch
It is involved in the regulation of body temperature.
It is also a source of vitamin D synthesis.
It excretes wastes.

4. Skin
The skin completely covers the body and is
continuous with the membranes lining the body
orifices.
Largest organ
Constitutes 15-20% of total body mass
Total area of body surface covered by
skin is about 2 m2
Thickness of skin varies from 0.3 mm to 3mm

5. Skin Receptors
Nociceptors- physical, mechanical or chemical stimulus
Merkle’s disc- light touch
Pacinian corpuscles-pressure or fast vibration
ruffini’s end bulb-heat
Krause end bulb-cold

6. Pigmentation of Skin:
Determined by five pigments present at different level and place of skin
1. Melanin (brown)
2. Melanoid (brown)
3. Carotene (yellow to orange)
4. Haemoglobin (purple)
5. Oxyhaemoglobin (red)

7. Functions Of Skin:
1. Protection
2. Sensory
3. Regulation of body temperature
4. Absorption
5. Secretion
6. Excretion
7. Regulation of pH
8. Synthesis

8. The main functions of the skin include:
A. support, nourishment, and sensation.
B. protection, sensory perception, and temperature regulation.
C. fluid transport, sensory perception, and aging regulation.
D. protection, motor response, and filtration.
Which of the following is NOT a sensory receptor of the skin?
A. Meissner corpuscle
B. Apocrine gland
C. Root hair plexus
D. Nociceptor
Which one of the following cell types is responsible for forming the skin’s ability to tan on
exposure to sunlight?
A. Melanocytes.
B. Keratinocytes.
C. Dendrocytes.
D. Lymphocytes.

9. Structure of Skin:
Two layers
a. Superficial layer, the epidermis
b. Deeper layer, the dermis
Below the dermis lies subcutaneous layer or hypodermis

11. The Epidermis:
It is the outer layer of skin formed by
stratified squamous keratinized epithelium.
It does not have blood vessels so nutrition
is provided by capillaries of dermis.
Five layers:
1. Stratum Basale
2. Stratum spinosum
3. Stratum granulosum
4. Stratum lucidum
5. Stratum corneum

12. 1. Stratum Basale: It is the thickest layer made up of superficially polygonal cells
and in deeper parts columnar cells. The skin color depends on the cells of this
layer which contain melanin pigment.
2. Stratum Spinosum: It is also known as prickle cell layer as cells of this layer
possess spine like cytoplasmic projections.
3. Stratum Granulosum: It is a thin layer with 2-5 row of flattened rhomboidal
cells.
4. Stratum Lucidum: It is made up of flattened epithelial cells. Many cells have
degenerated nucleus and in some cells the nucleus are absent. These cells
exhibit shiny appearance.
5. Stratum Corneum: It is known as horny layer. It is the outermost layer and
consists of dead cells known as keratin cells.

13. Cells of Epidermis:
• Keratinocytes
• Melanocytes
• Dendritic cells of Langerhans
• Cells of Merkel

14. Healthy epidermis depends upon three processes being synchronized:
Desquamation (shedding) of the keratinized cells from the surface.
Effective keratinization of cells approaching the surface.
Continual cell division in the deeper layers with newly formed cells
being pushed upwards to the surface.

15. The Dermis
It is the inner vascular layer of skin made
up of connective tissue and collagen fibers
Two layers:
Papillary layer(outer layer): It projects
into epidermis and contains blood vessels,
lymph vessels and nerve fibers.
Reticular layer(inner layer): It is made
up of elastic and reticular fibers and
consists of mast cells, nerve fibers, lymph
vessels, epidermal appendages and
fibroblast.

16. Subcutaneous Layer Or Hypodermis
It lies below the dermis.
It is a loose connective tissue which
connects skin with internal structures of
the body.
It serves as an insulator to protect the
body from excessive heat or cold of the
environment.

17. Differences Between Epidermis And Dermis
SN Epidermis Dermis
1. It is the outer layer of skin. It is the inner layer of skin.
2. It is avascular. It is vascular.
3. It is formed by keratinized
stratified squamous epithelium.
It is formed by connective tissue
and collagen fibers.
4. It is made up of five layers:
stratum corneum, stratum
lucidum, stratum granulosum,
stratum spinosum and stratum
basale.
It is made up of two layer:
papillary layer and reticular layer.

18. Types of Skin
1. Thin Hairy skin
2. Thick Glabrous Skin

19. Thin Hairy Skin
Epidermis is very thin.
It contains hair.
Found in all other parts
except palms and sole

20. Thick Glabrous Skin
Epidermis is very thick.
It has thick layer of Stratum corneum.
It has no hair.
Found in palms of hand and soles of foot.

21. Histology of skin

22. The outermost layer of the skin is the:
A. epidermis.
B. dermis.
C. hypodermis.
D. papillary dermis.
Which of the following layer of skin does not contain blood vessels?
A. Dermis
B. Cutis
C. Epidermis
D. All of above
The layer of epidermis that sheds keratin cells that are constantly replaced is
A. Stratum lucidum
B. Stratum corneum
C. Stratum mucosum
D. Stratum granulosum

23. Stratum corneum is composed of
A. Melanin
B. Granules
C. Keratin cells
D. Squamous cells
In human body, the thickest skin is located on
A. Thigh
B. Buttocks
C. Abdomen
D. Palm and soles
Which part of the skin is often referred as true skin?
A. Stratum corneum
B. Stratum spinosum
C. Dermis
D. Epidermis

24. Regulation Of Body Temperature By Skin
Nervous Control
The temperature regulating center in the hypothalamus is sensitive to the
temperature of circulating blood. The vasomotor center in the medulla
oblongata controls the diameter of small arteries and arterioles. The
vasomotor center is influenced by the temperature of its blood supply and
by nerve impulses from the hypothalamus.
Activity Of The Sweat Glands
When body temperature is increased by 0.25 to 0.5°C the sweat glands
secrete sweat onto the skin surface. Evaporation of sweat cools the body.

25. Effects Of Vasoconstriction And Vasodilation
As body temperature rises, the arterioles dilate and more blood enters
the capillary network in the skin. The skin is warm and pink in color. In
addition to increasing the amount of sweat produced, the temperature of
the skin rises and more heat is lost by radiation, conduction and
convection.
If the environmental temperature is low or if heat production is
decreased, the arterioles in the dermis are constricted. This reduces blood
flow to the body surface, conserving heat. The skin appears paler and feels
cool.

26. Regulation of Increase in Body Temperature
Body temperature increased
Stimulation of heat loss center (anterior hypothalamus)
No shivering Inhibition of sympathetic activity
Decreased adrenal secretion and metabolic rate Vasodilation of blood vessels suppling skin
Increase in blood flow to skin
Stimulate sweat gland
Increase in sweat production
Evaporation of sweat from skin takes the heat away from the body
Decrease in heat production
Decrease body temperature
Body temperature becomes normal

27. Regulation of Decrease in Body Temperature
Body temperature decreased
Stimulation of heat gain center (posterior hypothalamus)
Shivering Increased sympathetic activity
Increased adrenal secretion and metabolic rate Vasoconstriction of blood vessels suppling skin
Decrease in blood flow to skin
Sweat gland is inactive
Decrease in sweat production
Body heat is conserved
Increase in heat production
Increase body temperature
Body temperature becomes normal

28. Formation of Vitamin D
7-Dehydrocholesterol is a lipid-based substance in the skin and is
converted to vitamin D by sunlight.
This vitamin is used with calcium and phosphate in the formation and
maintenance of bone.

29. The skin begins the production of vitamin D in which of the following
situations? When
A. Exposed to ultraviolet radiation.
B. Signaled to by the hormone PTH.
C. Calcium is present.
D. It adds an hydroxyl group to a cholesterol molecule.

30. Appendages of Skin
Hairs
Sebaceous glands
Sweat glands
Nails

31. Hairs
Hairs grow from hair follicles, downgrowths of epidermal cells into the dermis or
subcutaneous tissue.
At the base of the follicle is a cluster of cells called the hair papilla or bulb.
The part of the hair above the skin is the shaft and the remainder, the root.
Hair color is genetically determined and depends on the amount and type of
melanin present.
White hair is the result of the replacement of melanin by tiny air bubbles.

32. Hair

33. Arrector pili
These are little bundles of smooth muscle fibers attached to the hair
follicles.
Contraction makes the hair stand erect and raises the skin around the
hair, causing ‘goose flesh’ or ‘goose bumps’.
The muscles are stimulated by sympathetic nerve fibers in response to
fear and cold.

34. Sebaceous Glands
These consist of secretory epithelial cells derived from the same tissue as
the hair follicles.
They secrete an oily antimicrobial substance, sebum, a mixture of keratin,
fat, and cellulose debris into the hair follicles and are present in the skin of
all parts of the body except the palms of the hands and the soles of the feet.
Sebum keeps the hair soft and pliable and gives it a shiny appearance. It also
prevents drying and cracking of skin, especially on exposure to heat and
sunlight.

35. Sebaceous Gland
The activity of these glands increases at puberty and is less at the extremes
of age, rendering the skin of infants and older adults prone to the effects of
excessive moisture (maceration).
Composition Of Sebum
Free fatty acids, Triglycerides, Squalene, Sterol, waxes and paraffin.

36. Sebaceous Glands

37. Sweat Glands
Sweat glands are widely distributed throughout the skin and are most
numerous in the palms of the hands, soles of the feet, axillae and groins.
They are formed from epithelial cells.
The bodies of the glands lie coiled in the subcutaneous tissue.
There are two types of sweat gland:
Eccrine sweat gland
Apocrine sweat gland

38. Types Of Sweat Glands
Eccrine sweat glands are the more common type and open onto the skin
surface through tiny pores, and the sweat produced here is a clear, watery
fluid important in regulating body temperature.
Apocrine sweat glands open into hair follicles and become active at
puberty. They may play a role in sexual arousal. These glands are found, for
example, in the axilla.
Bacterial decomposition of their secretions causes an unpleasant odor. A
specialized example of this type of gland is the ceruminous gland of the
outer ear, which secretes earwax

39. Sweat Glands

40. Sweat Gland continued…..
The most important function of sweat is in the regulation of body
temperature.
Excessive sweating may lead to dehydration and serious depletion of
sodium chloride unless intake of water and salt is appropriately
increased.
Composition Of Sweat
Water, sodium chloride, urea and lactic acid.

41. Nails
Human nails are equivalent to the claws, horns and hooves of animals.
Derived from the same cells as epidermis and hair these are hard, horny keratin
plates that protect the tips of the fingers and toes.
The root of the nail is embedded in the skin and covered by the cuticle, which
forms the hemispherical pale area called the lunula.
The nail plate is the exposed part that has grown out from the nail bed, the
germinative zone of the epidermis.
Finger nails grow more quickly than toe nails and growth is faster when the
environmental temperature is high.

42. Nails

43. Which integumentary system structure is considered an epidermal appendage?
A. Blood vessel
B. Nerve
C. Stratum basale
D. Hair
Sebum is a mixture of:
A. cellulose debris, fat, and keratin.
B. collagen and elastin.
C. watery fluid and sodium.
D. protein, water, and electrolytes.
The sweat glands that are widely distributed throughout the body are:
A. apocrine.
B. eccrine.
C. adipose.
D. sebaceous.

44. Which glands secrete “oil” into a hair follicle?
A. apocrine
B. eccrine
C. ceruminous
D. Sebaceous
What do the apocrine glands of the skin secrete?
A. apocrine
B. ceruminous
C. milk
D. sweat

46. Wound Healing
Conditions required for wound healing
Systemic factors
These include good nutritional status and general health. Infection, impaired
immunity, poor blood supply and systemic conditions, e.g. diabetes mellitus
and cancer, reduce the rate of wound healing.
Local factors
Local factors that facilitate wound healing include a good blood supply to
provide oxygen and nutrients and remove waste products, and freedom
from contamination by, e.g., microbes, foreign bodies or toxic chemicals.

47. Primary Healing (Healing By First Intention)
This type of healing follows minimal destruction of tissue when the
damaged edges of a wound are in close apposition, e.g. a surgical
incision.
There are several overlapping stages in the repair process.

49. Secondary Healing (Healing By Second Intention)
This type of healing follows extensive tissue destruction or when the
edges of a wound cannot be brought into apposition, e.g. varicose ulcers
and pressure (decubitus) ulcers.
The stages of secondary healing are the same as in primary healing;
healing time depends on effective removal of the cause and the size of
the wound.

50. Burns
These may be caused by many types of trauma including: heat, cold,
electricity, ionizing radiation and corrosive chemicals, including strong
acids or alkalis (bases).
Local damage occurs disrupting the structure and functions of the skin.

51. Types Of Burn
First degree when only the epidermis is involved, the surface is moist and there
are signs of inflammation including redness, swelling and pain. There are no
blisters and tissue damage is minimal.
Second degree when the epidermis and upper dermis are affected. In addition
to the signs and symptoms above, blistering is usually present.
Third degree (deep or full thickness) when the epidermis and dermis are
destroyed. These burns are usually relatively painless as the sensory nerve
endings in the dermis are destroyed. After a few days the destroyed tissue
coagulates and forms an eschar, or thick scab, which sloughs off after 2 to 3
weeks.

52. Burns
In circumferential burns, which encircle any area of the body, complications
may arise from constriction of the part by eschar, e.g. respiratory
impairment may follow circumferential burns of the chest, or the circulation
to the distal part of an affected limb may be seriously impaired.
Skin grafting is required except for small injuries.
Healing, which is prolonged, occurs by secondary intention and there is no
regeneration of sweat glands, hair follicles or sebaceous glands.
Resultant scar tissue often limits movement of affected joints.

53. Burns
The extent of burns in adults is roughly estimated using the ‘rule of nines’.
In adults, hypovolaemic shock usually develops when 15% of the surface
area is affected.
Fatality is likely in adults with third degree burns if the surface area affected
is added to the patient’s age and the total is greater than 80.

54. Complications Of Burns
Although burns affect the skin, when extensive, their systemic consequences
can also be life-threatening or fatal.
Dehydration and Hypovolemia
These may occur in extensive burns when there is excessive leakage of water
and plasma proteins from the damaged skin surface.
Shock
This may accompany severe hypovolemia.
Hypothermia
This develops when excessive heat is lost in leakage from burns.

55. Complications Of Burns
Infection
This occurs easily when subcutaneous tissue is exposed to the environment
and may result in septicaemia.
Renal failure
This occurs when the kidney tubules cannot deal with the large amount of
waste from haemolyzed erythrocytes and damaged tissue.
Contractures
These may develop later as fibrous scar tissue contracts distorting joints,
e.g. the hands, restricting their range of motion.

56. Management Of Burns
First Aid
Stop the burning process
Remove the person from source of burn
Removal of cloth
Ensure adequate airway
Remove from smoke
Cover the burn surface with clean dresses as quicklyS as possible
Transfer to hospital for definite treatment

57. People with full thickness burns to more than 20 % of their body are in a life
threatening situation. This is due to which of the following?
A. The body’s inability to thermoregulate.
B. The loss of the ability to produce vitamin D.
C. The buildup of urea and uric acid which would otherwise have been
excreted by the skin.
D. The body’s inability to prevent water loss