Integumentary System
Introduction
 The cutaneous membrane (skin) and its
accessory organs make up the
integumentary system
Four Types of Membranes
1.Serous membranes – line body cavities
that lack openings to the outside, such as
the thorax and the abdomen
2.Mucous membranes – line cavities and
tubes that open to the outside, such as
oral and nasal cavities
3.Synovial membranes – form the inner
linings of the joint cavities between the
ends of the bones at freely movable
joints
4.Cutaneous membrane – skin
Function of skin
 Maintains homeostasis
 Protection
 Regulates body temperature
 Excretion
 Secretion
Structure of Skin
 Two main layers – epidermis/dermis
 Epidermis – outer layer (made up of
stratified squamous epithelium)
 Dermis – inner layer – thicker (contains
connective, epithelial, smooth muscle.
and nerve tissue)
 Subcutaneous layer (hypodermis) –
beneath the dermis – made of loose
connective and adipose tissue that binds
skin to underlying organs
Epidermis
 Lacks blood vessels
 Base of epidermis is well nourished by
dermal blood vessels
 Cells are pushed outward as new cells
form and become keratinized as they die
 4 or 5 layers of epidermis
o stratum corneum – dead cells
(increase in friction causes calluses
and corns)
o stratum lucidum – found on palms of
hands and soles of feet
o stratum granulosum – layer where
cells die
o stratum spinosum – irregularly
shaped cells
o stratum germinativum (basal layer) –
where cells divide
Skin Color
 melanocytes in the epidermis produce
melanin (pigment that provides skin color)
 all people have the same amount of
melanocytes but the amount of melanin
produced varies (genetically determined)
 exposure to sunlight darkens skin
because melanin production increases
Dermis
 binds the epidermis to underlying tissues
 contain blood vessels – carries nutrients
to upper layers of skin and helps regulate
temperature
Subcutaneous layer (hypodermis)
 consists of adipose tissue which helps
insulate and conserve body heat
Accessory organs of the skin
Hair Follicles
 Hairs develop from cells at the base of
the hair follicle (an invagination of the
epidermis that dips down into the
dermis)
 Arrector pili muscle attaches to each hair
follicle – nerve impulses stimulate these
muscles to contract causing goose
bumps
Sebaceous glands
 Glands that secrete an oily mixture
called sebum through small ducts into
hair follicles which keeps hair and skin
soft and waterproof
 Acne – infection of the sebaceous gland
Nails
 Consists of nail plate – overlies the nail
bed
 Whitish region is called lunula – most
active growing region
Sweat glands
 Exocrine glands – produce sweat –
composed of water, salt, and urea
Healing of wounds
 Inflammation – blood vessels dilate,
become more permeable, forcing fluids
to leave the blood vessels and enter
damaged tissues
 Injury into the dermis or subcutaneous
layer
o Blood clot forms a scab
o Fibroblasts form new collagenous
fibers that bind edges of the wound
together
o Scab falls off
Skin Cancer
 Cutaneous carcinoma – originate from
epithelial cells
o Develop from hard, dry, scaly
growths (legions) that have reddish
bases
o Typically slow growing – usually
can be cured by surgical removal or
radiation
o May appear in people of any age
o Usually associated with sun exposure
o May arise from normal skin or mole
 Melanoma – originates from
melanocytes
o Usually bumpy and irregularly
shaped
o If not removed before it spreads to
deep tissues it is difficult to treat