2. INTEGUMENTARY SYSTEM
• The skin or integument & its accessory structures
(hair, glands & nails)constitute the integumentary
system.
• In this system are millions of sensory receptors of the
skin & its extensive vascular network
1. SKIN
2. HAIR
3. NAILS
4. GLANDS
3. SKIN
• SKIN is an organ because it consists of several kinds of tissues that are
structurally arranged to function together.
• It is largest organ of the body covering over 7,600 sq cm in average adult &
accounts for appx 7% of person’s body weight.
• Skin if of variable thickness average 1.5mm.
• Thickest on the part of body exposed to wear & abrasion such as soles of
the feet & palms of the hand (6mm thick)
• It is thinnest on eye lids, external genitalia & tympanic membrane (ear
drum) (0.5mm) thick.
• Even its appearance & texture varies from the rough callous skin covering
the elbows, knuckles to the soft sensitive areas of eyelids, nipples &
genitalia
5. EPIDERMIS
• Superficial protective layer of skin
• Derived from ectoderm
• Composed of stratified squamous epithelium
varies in thickness from 0.007-0.12mm.
• 4 to 5 layers present depending on where the
epidermis is located
• Epidermis of palms & soles have 5 layers because
these areas are exposed to friction
• In all other areas epidermis has 4 layers
8. 1.Stratum Basale
• Consists of single layer of cells in contact with
dermis.
4 types of cells compose the stratum basale
1. Keratinocytes
2. Melanocytes
3. Tactile (merkel cells)
4. Non pigmented granular dendrocytes
(langerhans cells)
9. Stratum Basale
• With exception of tactile cells , all cells are
constantly dividing mitotically & moving outward
to renew the epidermis.
• It takes 6-8 weeks for the cells to move from the
stratum basale to surface of the skin
• Keratinocytes produce keratin
• Melanocytes produce melanin
• Tactile (merkel cells) , sensory receptor cells aid in
tactile (touch) reception
• Non pigmented granular dendrocytes ,protective
macrophagic cells
10.
11. 2.Stratum Spinosum
• Also called spiny layer
• Contains several layers of cells
• Spiny appearance is due to the spine like
extensions that arise from the keratinocytes
when tissue is fixed for microscopic
examination
• Stratum spinosum & stratum basale are
collectively called stratum germinativum
12. 3.Stratum Granulosum
• Also called granular layer
• Consists of 3-4 flattened layers of cell
• These cells contain granules that are filled
with keratohyalin, a chemical precursor to
keratin.
13. 4.Stratum Lucidum
• Also called clear layer
• Nuclei, organelles & cell membranes are no
longer visible in the cells of stratum lucidum &
so histologically this layer appears clear.
• It exists only in the lips & in the thickened skin
of the soles & palms.
14. 5.Stratum Corneum
• Also called horn like layer
• Composed of 25-30 layers of flattened scale like cells
• Thousands of these dead cells shed from the skin surface
each day only to be replaced by the new ones from
deeper layers.
• This surface layer is cornified & actually protects the skin
• Friction at the surface of the skin stimulates additional
mitotic activity in the stratum basale & stratum
spinosum which may result in the formation of a callus
for additional protection .
15. Coloration of skin
• Normal color of skin is the expression of a
combination of 3 pigments
1. Melanin
2. Carotene
3. Hemoglobin
1. MELANIN:
is a brown black pigment produced in the
melanocytes of the stratum basale .all
individuals of similar size have appx same
number of melanocytes but the amount of
melanin produced & distribution of melanin
determines racial variations in skin color e.g
black, brown, yellow , white
16. 2.CAROTENE:
Is a yellowish pigment found in certain plant
products, such as carrots that tends to
accumulate in cells of stratum corneum &
fatty parts of dermis.
3.HEMOGLOBIN:
Is not a pigment of the skin rather it is the
oxygen binding pigment found in the red
blood cells .Oxygenated blood flowing through
dermis gives the skin its pinkish tone.
17. DERMIS
• Deeper & thicker than epidermis
• Elastic & collagenous fibers within the dermis
are arranged in definite pattern producing
lines of tension in the skin & providing skin
tone.
• More elastic fibers in dermis of young person
than in an elderly
• Provides nourishment to epidermis
• Contains sweat glands, oil secreting glands,
nerve ending & hair follicles.
18. Layers of dermis
Composed of 2 layers
1. STRATUM PAPILLAROSUM (papillary layer)
2. STRATUM RETICULAROSUM (reticular layer)
19. • Is in contact with the epidermis & accounts for
the one fifth of the entire dermis.
• Numerous projections called papillae extend
from the upper portion of the dermis into the
epidermis
• Papillae form the base for friction ridges on
the fingers & toes.
STRATUM PAPILLAROSUM
(papillary layer)
20. STRATUM RETICULAROSUM
(reticular layer)
• Deeper & thicker layers of the dermis
• Fibers are more dense & regularly arranged to
form a tough flexible meshwork
• Quite distensible , as it is evident in pregnant
women or obese but it can be stretched too
far causing a tearing of the dermis
• Repair of strained dermal area leaves a white
streak called stretch mark, or linea albicans
(found on buttock,thighs,abdomen & breasts)
21. INNERVATION OF SKIN
• Dermis of skin has extensive innervation
(nerve supply)
• Specialized integumentary effectors consist of
smooth muscles or glands within the dermis
that respond to motor impulses transmitted
from the central nervous system to the skin by
autonomic nerve fibers.
22. HYPODERMIS
• Hypodermis is not actually part of skin but it
binds skin to underlying organs
• Composed of loose connective tissues & adipose
cells interlaced with blood vessels.
• Amount of adipose tissue varies with region of
the body & sex, age , nutritional state of the
individual.
• Females have generally 8% thicker hypodermis
than males
• This layer functions to store lipid,insulate &
cushions the body & regulate temperature.
23. Functions of skin
1. Physical protection
2. Hydroregulation
3. Thermoregulation
4. Cutaneous absorption
5. Sensory reception
6. Communication
24. Glands of skin
• Although they originate in the epidermal
layer,all of the glands of the skin are located in
the dermis,where they are physically
supported & receive nutrients
• Glands of skin are referred to as
exocrine,because they are externally secreting
glands that either release their secretions
directly or through ducts.
25. Type of Skin Glands
• Glands of skin are of 3 basic types
1. Sebaceous Glands
2. Sudoriferous Glands
3. Ceruminous Glands
26. 1.Sebaceous Glands
• Commonly called oil glands
• They r associated with hair follicles , because they
develop from follicular epithelium of hair
• They are holocrine glands that secrete sebum onto the
shaft of the hair.
• Sebum lubricates stratum corneum & prevent hair
from becoming brittle
• If duct blocked,glands become infected & results in
acne.
• Sex hormones regulates production & secretion of
sebum
27. 2.Sudoriferous Glands
• Commonly called sweat glands.
• Excrete perspiration or sweat onto the surface of skin.
• Perspiration composed of salts,urea & uric acid.
• Serves not only for evaporative cooling but also for
excretion of certain wastes
• Sweat glands are most numerous on
palms,soles,axillary & pubic regions & on forehead
• They are coiled & tubular & are of 2 types
1. Eccrine sweat glands
2. Apocrine sweat glands
28. 1. Eccrine Sweat Glands:
• They are widely distributed over the body,
especially on the forehead , back,plams &
soles.
• These glands are formed before birth &
function in evaporative cooling.
2. Apocrine Sweat Glands:
Are much larger than the eccrine gland. They are
found in the axillary & pubic regions where
they secrete into hair follicles.
Apocrine glands are not functional until puberty.
29. Mammary Glands:
• Found within the breasts, are specialized
sudoriferous glands that secrete milk during
lactation.
• The breasts of female reach their greatest
development during the childbearing
years,under the stimulus of pituitary &
ovarian hormones.
30. 3.Ceruminous Glands
• These specialized glands are found in the
external auditory (ear canal) where they
secrete cerumen or ear wax.
• Cerumen is a water & insect repellant , and
also keeps the tympanic membrane pliable
• Excessive amount of cerumen may interfere
with hearing .
