The Integumentary System
Learning Objectives
• List the components of the integumentary system,
including their physical relationships.
• Specify the functions of the integumentary system.
• Describe the main features and functions of the
epidermis and dermis.
• Discuss individual and racial differences in skin.
• Discuss the effects of UV light on the epidermis.
• Explain the structure and function of the various
accessory organs of the skin.
• Explain how the skin responds to injury and aging.
The integumentary system consists of
• Cutaneous membrane
• Epidermis
• Dermis
• Accessory structures
• Subcutaneous layer
Integumentary system functions:
• Protection
• Excretion
• Temperature maintenance
• Nutrient storage
• Vitamin D3 synthesis
• Sensory detection
Figure 5.1 The Components of the
Integumentary System
Figure 5.1
SECTION 5-2
The Epidermis
Figure 5.2 Thin Skin and Thick Skin
• The epidermis is composed of layers of
keratinocytes
• Thin skin = four layers (strata)
• Thick skin = five layers
Figure 5.2
The epidermis
• Provides mechanical protection
• Prevents fluid loss
• Keeps microorganisms from invading the body
Layers of the epidermis:
• Stratum germinativum
• Stratum spinosum
• Stratum granulosum
• Stratum lucidum
• Stratum corneum
Figure 5.3 The Epidermal Ridges of Thick Skin
Figure 5.3
Epidermal characteristics:
• Cells accumulate keratin and eventually are shed
• Epidermal ridges are interlocked with dermal
papillae
• Fingerprints
• Improve gripping ability
• Langerhans cells (immunity) in s. spinosum
• Merkel cells (sensitivity) in s. germinativum
Figure 5.4 The Structure of the Epidermis
Figure 5.4
Skin color depends on
• Blood supply
• Carotene and melanin
• Melanocytes produce melanin and protect
from UV radiation
• Epidermal pigmentation
• Interrupted blood supply leads to cyanosis
Figure 5.5 Melanocytes
Figure 5.5a, b
Epidermal cells
• Synthesize vitamin D3 (cholecalciferol) when
exposed to UV
• Respond to epidermal growth factor
• Growth
• Division
• Repair
• Secretion
SECTION 5-3
The Dermis
Dermal Organization
• Papillary layer
• Contains blood vessels, lymphatics, sensory
nerves of epidermis
• Reticular layer
• Contains network of collagen and elastic fibers
to resist tension
Figure 5.8 Dermal Circulation
Figure 5.8
Stretch marks
• Caused by excessive stretching of the dermis
• Patterns of collagen and elastic fibers form lines
of cleavage
Figure 5.7 Lines of Cleavage of the Skin
Figure 5.7
Dermal Circulation and innervation
• Cutaneous plexus arteries found in subcutaneous
layer/ papillary dermis
• Cutaneous sensory receptors (light touch,
pressure)
Hypodermis
• Stabilizes skins position against underlying
organs and tissues
SECTION 5-5
Accessory Structures
Hairs
• Originate in hair follicle
• Composed of root and shaft
• Root base (hair papilla) surrounded by hair bulb
and root hair plexus
• Hairs have soft medulla and hard cortex
• Cuticle = superficial dead protective layer
Figure 5.9 the Anatomy of a Single Hair
Figure 5.9
Hair types
• Vellus hairs (peach fuzz)
• Terminal hairs ( heavy)
• Club hair (cessation of growth)
• Shed and grow according to hair growth cycle
Arrector pili muscle attaches to hair
Figure 5.10 Hair Follicles
Figure 5.10a-c
Glands in the skin
• Sebaceous
• Suderiferous
• Mammary
• Ceruminous
Sebaceous glands
• Discharge waxy sebum onto hair shaft when
associated with hairs
• Sebaceous follicles discharge onto epidermal
surface
Figure 5.11 Sebaceous Glands and Follicles
Figure 5.11
Suderiferous glands
• Apocrine sweat glands
• Produce odorous secretion
• Merocrine (eccrine) sweat gland
• Sensible perspiration
Figure 5.12 Sweat Glands
Figure 5.12a, b
Other glands
• Mammary glands
• Structurally similar to apocrine sweat glands
• Ceruminous glands
• In ear, produce waxy cerumen
Nails
• Nail body covers the nail bed
• Nail production occurs at the nail root
• Eponychium (cuticle) overlies root
• Free edge of nail extends over hyponychium
Figure 5.13 The Structure of a Nail
Figure 5.13
SECTION 5-7
Local Control of Integumentary Function
Injury and repair
• Regenerates easily
• Regeneration process includes formation of
• Scab
• Granulation tissue
• Scar tissue
Figure 5.14 Integumentary Repair
Figure 5.14, step 1-2
Figure 5.14 Integumentary Repair
Figure 5.14, step 3-4
SECTION 5-4
The Subcutaneous Layer
You should now be familiar with:
• The components of the integumentary system,
including their physical relationships.
• The functions of the integumentary system.
• The main features and functions of the epidermis
and dermis.
• Individual and racial differences in skin.
• The effects of UV light on the epidermis.
• The structure and function of the various
accessory organs of the skin.
• How the skin responds to aging.
SECTION 5-7
Aging and the Integumentary System
With age
• Integument thins
• Blood flow decreases
• Cellular activity decreases
• Repairs occur more slowly