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1. Integumentary system (skin)
INTEGUMENTARY SYSTEM

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• Integumentary system
• Consist of :
• Skin Epidermal derivatives
 Hair
 Nail
 Glands
• sebaceous glands
• sweat glands

3. 1. THE SKIN
• Called the integument or covering, its function is primarily
protective
• Skin (integument) is the largest “organ” of the body
• Forms the boundary between our internal and the external
environment
• It is a pliable, tough, organ that is constantly regenerating
• It accounts 15% of total body weight
• Without skin we would succumb to infection, water loss, or
heat loss
• Two main types of skin, hairy and glabrous(free from hair)

4. Integumentary System roles
 Protection
 Chemical barrier
 Physical or Mechanical barrier
 Biological barrier
 BodyTemperature Regulation
 Cutaneous Sensation
 Metabolic Functions
 Blood Reservoir
 Excretion

5. …roles: : Protection
 Chemical barrier
 Skin secretions like sebum from sebaceous
glands is bactericidal
• Sweat create an acid environment that retard
bacteria reproduction
 Skin color code which is Melanin shields the
skin from UV radiation

6. …roles: Protection
 Physical or mechanical barrier
 Hard keratinized cells provide a continuous
barrier
 Biological barrier
 Langerhans’ cells of the epidermis “present”
foreign substances (antigens) to the white
blood cells (lymphocytes) which in tern activate
our immune system
 Macrophages of the dermis dispose of viruses
and bacteria that have penetrate the epidermis
but they also work as presenters

7. …roles: Body Temperature
Regulation
 The body works best when its temperature
remains within homeostatic limits
 Cooling occurs through radiation of heat and
evaporation of water from the surface of the
skin
 Heating occurs from metabolism, activity and
shivering

8. …roles: Cutaneous Sensation
 The skin is richly supplied with cutaneous
receptors
 Cutaneous receptors are classified as
exteroreceptors because they respond to
external stimuli
 Cutaneous receptors include
 Meissner’s corpuscles (light touch)
 Pacinian corpuscle(deep pressure)
 Root hair plexuses (displacement of hair shaft)
 Free nerve endings (pain)

9. Excretion
 Limited amount of nitrogen-containing
wastes (ammonia, urea, and uric acid) are
eliminated from the body in sweat
 Sweating also excretes water and salt

10.  Skin layers :
 Epidermis
 Dermis
 Hypodermis /Superficial fascia

11.  Outermost protective shield of the body
 1.5 - 4.0 mm in thickness depending on location
 Composed of epithelial cells, stratified
squamous(????)
 Avascular receives nutrients that diffuse from
dermis
 Consists of four distinct cell types
 Arranged in four/five distinct cell layers
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12. 12
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13. Layers of epidermis
Stratum Basale Stratum Spinosum
 Lowest epidermal
layer, near dermis
 Good nutrient supply
 Reproduces by mitosis
 Cuboidal, columnar in
shape
 Moves to upper
epidermis in 27 days
 Living cells
 Dividing
 8-10 cells thick
 Polygonal in
appearance

14. Cont…
Stratus Granulosum, Stratus Lucidum
 Poor nutrient supply.
 Flatten layer of cells.
 3-5 cells thick.
 No cell division.
 Keratin accumulates
 Release of glycolipid
slows water loss
 Found only in very
thick skin.
 Translucent.
 Highly keratinized.
 Dead cells

15. Stratum Corneum
 25-30 cells thick.
 Cells are filled with keratin and hardened.
 Dead cells
 Outer most layer of epidermis
 Contain Keratinocytes cells

16. Cells of the Epidermis
Keratinocytes
Melanocytes
Merkel cells
Langerhans’ cells

17. 17
Cells of the Epidermis
 Keratinocytes
 Melanocytes
 Merkel cells
 Langerhans’
cells

18. Keratinocyte
• Principal cell of the epidermis
• Arise from constant cell mitosis at the deepest layer of the
epidermis, (stratum basale )
• Its chief role is to produce keratin, the tough fibrous
protein that gives the epidermis its protective qualities
 Every minute skin sheds over 30,000 dead cells.
• A totally new epidermis every 25-45 days

19. Melanocytes
• Specialized epithelial cells that synthesize the
pigment melanin
• Melanin granules form a pigment shield that protects
the nucleus from ultraviolet (UV) radiation in
sunlight
• All humans have the same amount of melanocytes
• Racial differences in skin coloring is thought to
reflect the kind and amount of melanin made and
retained.

20. Langerhans's Cells
• Cells arise from bone marrow and migrate to the
epidermis
• The cells are macrophages that help to activate the
immune system
• Their cell processes extend among surrounding
keratinocytes

21. Merkel Cells
• Each Merkel cell is associated with a disc shaped
sensory nerve ending
• The combined structure is called a Merkel disc
• Merkel discs function as a sensory nerve receptor
for touch

22. Dermis
 The dermis is the second major skin region
 Layer of strong, flexible connective tissue
 Cells of dermis are typical of connective tissue cells
• Fibroblasts,
• macrophages,
• mast cells, and
• White blood cells
 Semifluid matrix is heavily embedded with protien
fibers: collagen, elastin, and reticular
Dermis

23. Dermis
 Dermis is richly supplied with nerve endings, blood
vessels, and lymphatic vessels
 Hair follicles, oil and sweat glands, are located in
the dermis
 Dermis has two main layers
– Papillary layer
– Reticular layer
Dermis

24. Papillary layer
 Composed of loose areolar connective tissue.
 Fingerlike projections called papillae, that extend
toward the epidermis.
 The papillae provide the dermis with a "bumpy"
surface that interdigitates with the epidermis,
strengthening the connection between the two
layers of skin.

25. Reticular layer
 This layer accounts for 80% of the dermis
 The reticular region lies deep in the papillary region and is
usually much thicker contains the skin appendages
 Collagen fibers of the dermis give the skin its strength and
resiliency
 Collagen binds water helping to maintain hydration
 Elastin provides stretch-recoil properties
Reticular layer

26. Dermal stretching
 During pregnancy dermal tearing may occur
indicated by silvery white scars or “stretch marks”
 Blisters are the separation of the epidermal and
dermal layers with the resulting development of a
fluid filled pocket

27. Hypodermis or superficial fascia
 A subcutaneous tissue deep to the skin
 Not considered a part of the skin, but it shares
some of the skins protective functions
 Consists mostly of adipose tissue and areolar
connective tissue
 It functions to store fat, anchor the skin to the
underlying muscles, allowing for movement
 Hypodermis thickens markedly when one gains
weight

28. Hypodermis/ superficial fascia

29. Hypodermis Fat Deposition
 Female
 Breasts
 Thighs
 Saddle bags
 Male
 Anterior abdomen
 Beer belly
 Waist
 Spare tire
 Fat is absent in eyelids, pinna of ear, scrotum
 Muscle fibers are present in the
subcutaneous tissue of scalp, face and
scrotum

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31. 2. Epidermal derivatives:
• Glands
- sebaceous glands
- sweat glands/ Sudoriferous
• Hair
• Nail
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32. Sweat Glands:Sweat
 Sweat is a hypotonic filtrate of the blood that passes
through the secretory cells of the sweat glands
 It is 99% water with some:
 (NaCl),
 vitamin C,
 antibodies,
 traces of metabolic wastes and lactic acid
 Normally sweat is acidic with a pH between 4 and 6
 Composition depends on heredity and diet

33. Sweating
 Sweating is regulated by the sympathetic
divisions of the autonomic nervous system
 Its major role is to assist in thermoregulation
and prevent overheating of the body
 Heat induced sweating begins on the
forehead and spreads inferiorly
 Emotional sweating “cold sweat” is brought
on by fright, embarrassment, or nervousness
and begins on the palms, soles, and axillae
and then spreads over the body

34. Sweat Glands
 Sweat glands are distributed over the
entire body surface except the nipples and
parts of the external genitalia
 Approximately 2.5 million per individual
 Two major types
 Eccrine sweat glands
 Apocrine sweat glands

35. Eccrine sweat glands
 The most numerous sweat gland
 Particularly abundant on the palms, soles
of the feet, and forehead
 Eccrine sweat glands duct directly to the
surface
 Non smelly

36. Apocrine sweat glands
 Largely confined to the axillary and
anogenital areas
 Apocrine sweat glands are larger than
eccrine sweat glands and their ducts
empty into hair follicles
 Sweat in nature is odorless but bacteria
upon our skin decompose these
substances and produce body odor
 Apocrine sweat glands duct into the hair
follicle,
 Smell sweat

37. Ceruminous glands
 Ceruminous glands are modified apocrine
glands found in the lining of the external
ear
 These glands secrete cerumen, or earwax,
which because of its sticky texture deters
insects and foreign material from entering
the ear

38. Mammary glands
 Mammary glands are another variety of
specialized sweat gland that secretes milk
 Lobules within the breast produce milk
when a woman is lactating
 Compound alveolar glands pass the milk
into the lactiferous ducts which open to
the outside of the nipple

39. Sebaceous (oil) Glands
 Sebaceous glands are simple alveolar
glands found all over the body except on
the palms and soles
 The glands are small on the body trunk
and limbs, but quite large on the face, neck
and upper chest
 These glands secrete an oil called sebum

40. Sebaceous Glands (con’t)
 Sebum softens and lubricates the hair and
skin, prevents hair from becoming brittle,
and slows water loss from the skin
 Sebum is bactericidal and reduces the
number of bacteria residing on the surface
of the skin
 The glands are regulated by hormones and
while relatively inactive in childhood
become activated in both sexes during
puberty
– NB. Acne = blocked sebaceous gland

41. Hairs and Hair Follicles
 The main function of our:
 sparse body hair is to sense insects on
the skin before they sting
Hair on the scalp protects against
trauma, heat loss, and sunlight
Eyelashes shield the eyes, and nose
hairs filter large particles like lint and
insects from the air

42. Structure of a Hair
 Hairs, or pili, are flexible strands produced
by hair follicles that consist of largely
keratinized cells
 Hard keratin found in hair is tougher and
more durable than that found in epidermal
layers and does not flake

43. Structure of a Hair(cont’d)
 Each hair made of a shaft, root and bulb
 Shaft is what you see (dead cells)
 Root is below the skin
 Bulb located at the base of the root within the
follicle
 Follicle is the sheath of epidermal cells around
the root
 Cells divide in the bulb, push their way up
 This is how hair grows in length…cells
growing roughly 1mm every 3 days
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44. Structure of a Hair Follicle
 Associated with
each hair follicle is
a bundle of smooth
muscle fiber called
arrector pili muscle
 The muscle fibers
pull the hair shaft
into an upright
position

46. Nails
• Composed of a compressed layer of stratum corneum cells
• Hardness derived from dense keratin deposits.
• Key parts:
– Body (what usually gets painted),
– Free border (tip of the nail),
– Nail bed (what the nail rests on (stratus spinosum of the
dermis)
– Eponychium = cuticle (covers the hidden border…the
hangnail area)
–Lunula (semi-circle at the base of the nail) is all that
you can see of the nail matrix
The nail matrix lies deep to the lunula and is the site
where nail growth is occurring
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47. Nails
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