Chapter 5:
The Integumentary
System
 What
are the structures
and functions of the
integumentary system?
Size of the Integument
 The
integument is the largest system of
the body:


16% of body weight
1.5 to 2 m2 in area
Parts of the Integument
 The
integument is made up of
2 parts:
1.
2.
cutaneous membrane (skin)
accessory structures
Parts of the
Integumentary System
Parts of the
Cutaneous Membrane
 Outer

superficial epithelium (epithelial tissues)
 Inner

epidermis:
dermis:
connective tissues
Accessory Structures
 Originate
in the dermis
 Extend through the epidermis to skin
surface:



hair
nails
multicellular exocrine glands
Connections
 Circulatory

blood vessels in the dermis
 Nervous

system:
system:
sensory receptors for pain, touch, and
temperature
The Subcutaneous Layer
 Subcutaneous
layer (superficial fascia or
hypodermis):



loose connective tissue
below the dermis
location of hypodermic injections
Functions of Skin
 Protects
underlying tissues and organs
 Excretes salts, water, and organic wastes
(glands)
 Maintains body temperature (insulation
and evaporation)
Functions of Skin
 Synthesizes
 Stores
vitamin D3
lipids
 Detects touch, pressure, pain, and
temperature
What are the main
structures and functions
of the epidermis?
Cells of the Epidermis
 Keratinocytes:


contain large amounts of keratin
the most abundant cells in the epidermis
Epidermis
 Avascular
stratified squamous epithelium
 Nutrients and oxygen diffuse from
capillaries in the dermis
Thin Skin
 Covers
most of the body
 Has 4 layers of keratinocytes
Layer of skin
 Stratum

germinativum
Epidermal ridges
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 Stratum

spinosum
Spiny layers
P 156
 Stratum

granulosum
Grainy layer
5 layers of skin only
 Stratum

lucidum
Only in palms and soles
p156
 Stratum

corneum
Dead
• 15 – 30 cell layers
• Water resistant – not waterproof
Thick Skin
 Covers
the palms of the hands and soles
of the feet
 Has 5 layers of keratinocytes
Skin Life Cycle
 It
takes 15–30 days for a cell to move
from stratum germinosum to stratum
corneum
What causes different
skin colors?
Skin Color
 Skin


color depends on:
the pigments carotene and melanin
blood circulation (red cells)
Carotene
 Orange-yellow
pigment
 Found in orange vegetables
 Accumulates in epidermal cells and fatty
tissues of the dermis
 Can be converted to vitamin A
Melanin
 Yellow-brown
or black pigment
 Produced by melanocytes in stratum
germinativum
 Stored in transport vesicles
(melanosomes)
 Transferred to keratinocytes
Function of Melanocytes
 Melanin
protects skin from sun damage
 Ultraviolet (UV) radiation:

causes DNA mutations and burns which lead
to cancer and wrinkles
Melanocytes
 Skin
color depends on melanin production,
not number of melanocytes
Capillaries and Skin Color
 Oxygenated
red blood contributes to skin
color:


blood vessels dilate from heat, skin reddens
blood flow decreases, skin pales
Cyanosis
 Bluish
skin tint
 Caused by severe reduction in blood flow
or oxygenation
Illness and Skin Color
 Jaundice:


buildup of bile produced by liver
yellow color
 Addison’s


disease:
and other diseases of pituitary gland
skin darkening
What are the structures and
functions of the dermis?
The Dermis
 Is
located between epidermis and
subcutaneous layer
 Anchors epidermal accessory structures
(hair follicles, sweat glands)
Characteristics of Dermis
 Strong,
due to collagen fibers
 Elastic, due to elastic fibers
 Flexible (skin turgor)
Skin Damage
 Sagging
and wrinkles (reduced skin
elasticity) are caused by:




dehydration
age
hormonal changes
UV exposure
Lines of Cleavage
 Collagen


and elastic fibers in the dermis:
are arranged in parallel bundles
resist force in a specific direction
Clinical Importance
 Lines
of cleavage establish important
patterns:


a parallel cut remains shut, heals well
a cut across (right angle) pulls open and scars
Lines of Cleavage
Dermal Circulation
What are the structures
and functions of the
subcutaneous layer?
The Hypodermis
 The



subcutaneous layer or hypodermis:
lies below the integument
stabilizes the skin
allows separate movement
What are the skin glands
and secretions?
Exocrine Glands
 Sebaceous


holocrine glands
secrete sebum
 Sweat


glands (oil glands):
glands:
merocrine glands
watery secretions
Types of Sebaceous Glands
 Simple

branched alveolar glands:
associated with hair follicles
 Sebaceous

follicles:
discharge directly onto skin surface
Sebaceous Glands
Sebum
 Contains
lipids and other ingredients
 Lubricates and protects the epidermis
 Inhibits bacteria
What are the
functions
of sweat glands?
Types of Sweat Glands
 Apocrine:

found in armpits, around nipples, and groin
 Merocrine:


widely distributed on body surface
especially on palms and soles
Apocrine Sweat Glands
 Merocrine
secretions, not apocrine
 Associated with hair follicles
 Produce sticky, cloudy secretions
 Break down and cause odors
Merocrine Sweat Glands
 Also




called eccrine glands:
coiled, tubular glands
discharge directly onto skin surface
sensible perspiration
water, salts, and organic compounds
Functions of Merocrine Sweat
 Cools
skin
 Excretes water and electrolytes
 Flushes microorganisms and harmful
chemicals from skin