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.

• Cutaneous membrane

• Epidermis

• Dermis

• Accessory structures

• Subcutaneous layer

The integumentary system consists of

• Protection

• Excretion

• Temperature maintenance

• Nutrient storage

• Vitamin D3 synthesis

• Sensory detection

Integumentary system functions:

Figure 5.1 The Components of the Integumentary System

Figure 5.1

SECTION 5-2 The Epidermis

• The epidermis is composed of layers of keratinocytes

• Thin skin = four layers (strata)

• Thick skin = five layers

Figure 5.2 Thin Skin and Thick Skin

Figure 5.2

• Provides mechanical protection

• Prevents fluid loss

• Keeps microorganisms from invading the body

The epidermis

• Stratum germinativum

• Stratum spinosum

• Stratum granulosum

• Stratum lucidum

• Stratum corneum

Layers of the epidermis:

Figure 5.3

Figure 5.3 The Epidermal Ridges of Thick Skin

• 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

Epidermal characteristics:

Figure 5.4 The Structure of the Epidermis

Figure 5.4

• Blood supply

• Carotene and melanin

• Melanocytes produce melanin and protect from UV radiation

• Epidermal pigmentation

• Interrupted blood supply leads to cyanosis

Skin color depends on

Figure 5.5 Melanocytes

Figure 5.5a, b

• Synthesize vitamin D3 (cholecalciferol) when exposed to UV

• Respond to epidermal growth factor

• Growth

• Division

• Repair

• Secretion

Epidermal cells

SECTION 5-3The Dermis

• Papillary layer

• Contains blood vessels, lymphatics, sensory nerves of epidermis

• Reticular layer

• Contains network of collagen and elastic fibers to resist tension

Dermal Organization

Figure 5.8 Dermal Circulation

Figure 5.8

• Caused by excessive stretching of the dermis

• Patterns of collagen and elastic fibers form lines of cleavage

Stretch marks

Figure 5.7 Lines of Cleavage of the Skin

Figure 5.7

• Cutaneous plexus arteries found in subcutaneous layer/ papillary dermis

• Cutaneous sensory receptors (light touch, pressure)

Dermal Circulation and innervation

• Stabilizes skins position against underlying organs and tissues

Hypodermis

SECTION 5-5Accessory Structures

• 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

Hairs

Figure 5.9 the Anatomy of a Single Hair

Figure 5.9

• 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

Hair types

Figure 5.10 Hair Follicles

Figure 5.10a-c

• Sebaceous

• Suderiferous

• Mammary

• Ceruminous

Glands in the skin

• Discharge waxy sebum onto hair shaft when associated with hairs

• Sebaceous follicles discharge onto epidermal surface

Sebaceous glands

Figure 5.11 Sebaceous Glands and Follicles

Figure 5.11

• Apocrine sweat glands

• Produce odorous secretion

• Merocrine (eccrine) sweat gland

• Sensible perspiration

Suderiferous glands

Figure 5.12 Sweat Glands

Figure 5.12a, b

• Mammary glands

• Structurally similar to apocrine sweat glands

• Ceruminous glands

• In ear, produce waxy cerumen

Other glands

• Nail body covers the nail bed

• Nail production occurs at the nail root

• Eponychium (cuticle) overlies root

• Free edge of nail extends over hyponychium

Nails

Figure 5.13 The Structure of a Nail

Figure 5.13

SECTION 5-7Local Control of Integumentary Function

• Regenerates easily

• Regeneration process includes formation of

• Scab

• Granulation tissue

• Scar tissue

Injury and repair

Figure 5.14 Integumentary Repair

Figure 5.14, step 1-2

Figure 5.14 Integumentary Repair

Figure 5.14, step 3-4

SECTION 5-4The Subcutaneous Layer

• 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.

You should now be familiar with:

SECTION 5-7Aging and the Integumentary System

• Integument thins

• Blood flow decreases

• Cellular activity decreases

• Repairs occur more slowly

With age