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 5-3 The 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 5-5 Accessory 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 5-7 Local 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 5-4 The 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 5-7 Aging and the Integumentary System

Integument thins Blood flow decreases Cellular activity decreases Repairs occur more slowly With age