Integumentary System
Chapter 5
From Essentials of Anatomy & Physiology,
Seeley, Stephens, and Tate, 5th Edition, 2005,
McGraw Hill Companies
Functions
• Protection against abrasion and ultraviolet light
• Protection from entry of microorganisms and dehydration
• Sensation receptors for heat, cold, touch, pressure, and pain
• Production of precursors to Vitamin D when exposed to
ultraviolet light
• Regulation of temperature by controlling blood flow to the skin
and activity of sweat glands
• Excretion of waste products through the skin and the gland
secretions
Facts
• The integumentary system consists of the skin and
the structures derived from it including hair, nails,
and glands.
• The skin is the largest organ of the body, covering
approximately 2 square meters and having a mass of
about 5 kilograms.
• The study of the integument is called dermatology.
Anatomy of Skin
• Epidermis - the five outermost thin layers, mitosis in the
deepest layer produces new cells as the older cells move
towards the most superficial layer where they are sloughed off
• Dermis - the thicker layer below the epidermis containing blood
vessels, nerve endings, hair follicles, smooth muscles,
lymphatic vessels, sweat glands, and sebaceous glands
• Hypodermis - the layer of loose connective tissue under the
dermis and not considered part of the skin, it contains half of
the body’s stored fat which acts as padding and insulation, it
attaches to underlying bones and muscles
• This image shows the
epidermis partially
peeled away
from the dermis.
• Note the numerous
blood vessels extending
into the dermis from the
hypodermis.
• Note the fat in the
hypodermis.
This is a micrograph of actual skin
sliced thinly and stained.
Note the epidermis, dermis, and
hypodermis. The outer cells of the
epidermis are sloughing off.
The dermal papillae are
projections of the dermis which
extend into the epidermis. They
contain tiny blood vessels that
supply the epidermis and aid in
regulation of body temperature.
Fingerprints are projections of the dermal papillae into the epidermis
of the fingertips. They increase friction and help improve grip.
This image shows the
five layers of the
epidermis.
The outermost layer is
called the stratum
corneum:
-25 layers of
dead skin cells
-Keratinized
Keratin is a protein that builds up in cells of the epidermis as they
move from the deepest layer, the stratum basale, towards the skin’s
surface. This process is called keratinization and takes 2-4 weeks.
Epidermal Layers
Composed primarily of keratinized stratified squamous
epithelial cells -- consisting of 4-5 layers:
1. stratum corneum: outermost layer, keratinized dead
epithelium
2. stratum lucidum: layer found in thickest areas of skin
3. stratum granulosum: 3-5 layers of flattened granular
cells, developing keratin fibers
4. stratum spinosum: multiple layers of cells
5. stratum basale: deepest layer of single cuboidal or
columnar cells, also contains melanocytes
- Blisters, Calluses &Psoriasis
Skin Color
- Genetics, Environment & Physiology:
1. # of melanocytes - difference in kind, amount
& size
2. sunlight, UV light, etc.
3. blood in dermis, blood vessels, freckles &
moles
4. other pigments - carotinoids
5. jaundice – liver disorder
Skin, hair, and eye
color are all due to a
molecule called
melanin. This
provides protection
from the sun’s
ultraviolet rays.
Melanin is made by special cells in the stratum basale called
melanocytes which have extensions reaching towards the skin’s
surface. Note the pigment granules in these cell extensions.
Variations in skin color are due to the color, amount, and distribution
of melanin, not to the number of melanocytes present in the
epidermis.
Special Features of the Dermis
• Hair follicles - hair grows from hair bulbs in the follicle, the follicles
are actually extensions of the epidermis deep into the dermis
• Arrector pili (muscles) - an arrector pili muscle is associated with
each hair follicle, when the muscle contracts the hair stands on end,
contraction of these muscles also causes goose bumps
• Sweat glands - sweat is produced in these coiled glands and is
secreted on the skin’s surface through pores, sweat is sometimes
produced due to emotional stress but is usually produced in order to
decrease body temperature by evaporative cooling
• Sebaceous glands - most sebaceous glands are connected to hair
follicles and produce an oily substance called sebum, the sebum
protects against drying of the hair and skin and against some
bacteria
Skin Glands

Sebaceous glands:
- assoc. w/ hair follicles,
secrete sebum - oils hair,
lubricates skin & prevent
water loss
- acne vulgaris
 Sweat glands:
 Eccrine: deep in dermis or subcutaneous layer, odorless
secretions, function in thermoregulation
 Apocrine: found near hair follicles, in axillary regions,
released during pain, fear & stress or sexual arousal
- Ceruminous & mammary glands
Note the extension of the epidermis far into the dermis forming the
hair follicle. Also, note the coiled sweat gland and the sebaceous
gland connected to the hair follicle.
Nails
Wound healing