2. 2
Introduction:
Organs are body structures
composed of two or more different
tissues.
The skin and its accessory organs
make up the integumentary
system.
3. 3
Skin and Its Tissues
The skin is a large organ responsible for:
temperature regulation
protection of underlying tissues
Slowing the rate of water loss
housing sensory receptors
synthesizing certain chemicals
excreting wastes
4. 4
The skin consists of an outer epidermis and
a dermis, connected to underlying tissue by
the subcutaneous layer (hypodermis).
5. 5
Epidermis
The epidermis is made up of stratified
squamous epithelium and lacks blood
vessels.
The layer of reproducing cells (the stratum
basale), which lies at the base of the
epidermis, is well-nourished by blood
vessels from the deeper dermal layer.
6. 6
Cells are pushed outward as new cells are
formed, and become keratinized as they
die.
Layers of the Epidermis:
Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
stratum basale
7. 7
Skin Color
Specialized cells in the epidermis called
melanocytes produce melanin, a dark pigment
that provides skin color.
Differences in skin color result from differing
amounts of melanin and in the size of melanin
granules.
The amount of melanin
produced is affected by
genetics and
environmental factors.
8. 8
Dermis
The dermis binds the epidermis to underlying
tissues.
It consists of dense connective tissue with tough
collagen and elastic fibers within a gel-like
ground substance.
9. 9
Dermal blood vessels
carry nutrients to
upper layers of skin
and help to regulate
temperature.
The dermis also
contains nerve fibers,
sensory fibers, hair
follicles, sebaceous
glands, and sweat
glands.
10. 10
Subcutaneous Layer
The subcutaneous layer
(hypodermis) is composed
of loose connective tissue
and insulating adipose
tissue.
It binds the skin to
underlying organs and
contains the major blood
vessels that supply the
skin.
11. 11
Accessory Organs of the Skin
Hair Follicles
Hair can be found in nearly all regions of the skin.
Hairs develop from cells at the base of the hair follicle,
an area of the lower epidermis that dips down into the
dermis.
As new cells are formed, old cells are pushed outward,
become keratinized, and die forming the hair shaft.
12. 12
Hair color is determined by genetics; melanin from
melanocytes is responsible for most hair colors;
red hair contains an additional pigment.
A bundle of smooth muscle cells, called the arrector
pili muscle, attaches to each hair follicle. These
muscles cause goose bumps when cold or
frightened.
14. 14
Sebaceous Glands
Associated with hair follicles and secrete an oily
substance that waterproofs and moisturizes
the hair shafts.
Nails
Nails consist of stratified squamous epithelial
cells overlying the nail bed.
As new cells are produced,
older ones are pushed
outward and become
keratinized.
15. 15
Sweat Glands
Each gland consists of a tiny tube that originates
as a ball shaped coil lined with sweat secreting
epithelial cells.
Cells respond to body temperature and stress
Modified Sweat Glands
Modified sweat glands, called secrete wax in the
ear canal.
Mammary glands, another modified type of sweat
glands, secrete milk.
16. 16
Regulation of Body Temperature
The skin plays a key role in the homeostatic mechanism
that regulates body temperature.
Response to increased body temperature
Heat from cellular metabolism or the environment is
transferred to the blood and carried to the
hypothalamus of the brain.
The hypothalamus signals the dermal blood vessels to
dilate and sweat glands to secrete.
Increased blood flow to the skin and evaporation of
sweat results in a release of heat from the body.
17. 17
Response to decreased body temperature
Hypothalamus detects decrease in body temperature
Hypothalamus stimulates dermal blood vessels to
constrict and sweat glands to remain inactive.
Decreased blood flow to the skin and lack of sweat
reduce amount of heat loss.
Skeletal muscles may also be stimulated (shivering)
which increases cellular metabolism and thus, heat
production.
19. 19
Healing of Wounds and Burns
The body’s initial response to skin trauma is
inflammation.
Inflammation-
The dilation of blood vessels in affected area
become more permeable, fluids leave the blood
vessels and enter the damaged tissues. This
provides the tissues with increased nutrients
and oxygen necessary for healing.
21. 21
Healing the wound
Shallow wounds are healed as epithelial cells
along the margin of the wound divide more
rapidly than usual and fill the gap.
Wounds that affect the dermis &/or hypodermis
result in a blood clot and “scab” that cover and
protect the underlying tissues. Fibroblasts form
collagenous fibers that bind the edges of the
wound together.
22. 22
Skin cancer
Squamous cell carcinoma
Basal cell carcinoma
Common, slow growing form of skin cancer,
usually linked to over exposure to sun, usually
curable
Melanoma
develop in melanocytes, lesion becomes
dangerous when it spreads downward into deeper
layers, survival rate low once this type of growth
occurs.
