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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)
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
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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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
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
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
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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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