1

Chapter 5 The Integumentary System

2/19/2009

2

Introduction

The organs of the integumentary system include the skin and its accessory structures including hair, nails, and glands, as well as blood vessels, muscles and nerves

Dermatology is the medical specialty for the diagnosis and treatment of disorders of the integumentary system.

2/19/2009

3

Structure of the Skin: Objectives

Describe the layers of the epidermis and the cells that compose them.

Compare the composition of the papillary and reticular regions of the dermis.

Name the tissue types composing the epidermis and dermis. List the major layers of each and describe their functions.

Explain the basis for different skin colors. Briefly describe how changes in skin color

may be used as clinical signs of certain disease states.

2/19/2009

4

Structure of the Skin

The skin (cutaneous membrane) covers the body and is the largest organ of the body by surface area and weight

Its area is about 2 square meters (22 square feet) and weighs 4.5-5kg (10-11 lb), about 16% of body weight

It is 0.5 – 4 mm thick, thinnest on the eyelids, thickest on the heels; the average thickness is 1 – 2 mm

2/19/2009

5

Structure of the Skin

It consists of two major layers: outer, thinner layer called the epidermis,

consists of epithelial tissue inner, thicker layer called the dermis Beneath the dermis is a subcutaneous

(subQ) layer (also called hypodermis) which attaches the skin to the underlying tissues and organs.

2/19/2009

6

Components of the Integumentary System

2/19/2009

7

Structure of the Skin

The epidermis has a number of important characteristics:

the epidermis is composed of keratinized stratified squamous epithelium

it contains four major types of cells: see next slide

2/19/2009

8

Structure of the Skin1. Keratinocytes (90% of the cells) produce

keratin which is a tough fibrous protein that provides protection

2. Melanocytes: which produce the pigment melanin that protects against damage by ultraviolet radiation

3. Langerhans cells: involved in immune responses, arise from red bone marrow

4. Merkel cells: which function in the sensation of touch along with the adjacent tactile discs

2/19/2009

9

Types of Cells in the Epidermis

2/19/2009

10

Epidermis The epidermis contains four major layers (thin

skin) or five major layers (thick skin)1. Stratum basale (deepest layer) or stratum

germinativum, where continuous cell division occurs which produces all the other layers

2. Stratum spinosum, 8-10 layers of keratinocytes

3. Stratum granulosum, which includes keratohyalin and lamellar granules

2/19/2009

11

Epidermis5. Stratum lucidum is present only in thick skin (the

skin of the fingertips, palms, and soles)6. Stratum corneum: composed of many sub layers of

flat, dead keratinocytes called or squames that are continuously shed and replaced by cells from deeper strata; constant friction can stimulate formation of a callus.

Keratinization, the accumulation of more and more protective keratin, occurs as cells move from the deepest layer to the surface layer

2/19/2009

12

Layers of the Epidermis

2/19/2009

13

Dermis The dermis has several important

characteristics: is composed of connective tissue collagen and

elastic fibers contains two layers

1. papillary region (upper layer immediately beneath epidermis) consists of areolar connective tissue containing thin collagen and elastic fibers, dermal papillae (including capillary loops), corpuscles of touch and free nerve endings

2/19/2009

14

Dermis

2. reticular region, the deep layer, consists of dense irregular connective tissue containing collagen and elastic fibers adipose cells, hair follicles, nerves, sebaceous (oil) glands, and sudoriferous (sweat) glands

2/19/2009

15

Dermis

Lines of cleavage - “tension lines” in the skin indicate the predominant direction of underlying collagen fibers

Epidermal ridges reflect contours of the underlying dermal papillae and form the basis for fingerprints (and footprints); their function is to increase firmness of grip by increasing friction.

2/19/2009

05_01bc

17

Basis of Skin Color Variations in skin color arise from variations in

the amounts of three pigments: melanin, carotene, and hemoglobin

Melanin - a yellow-red or brown-black pigment produced by melanocytes (located mostly in the epidermis, where it absorbs UV radiation)

The amount of melanin causes the skin’s color to vary from pale yellow to tan to black

The number of melanocytes are about the same in all people; differences in skin color is due to the amount of pigment produced

2/19/2009

18

Basis of Skin Color

A benign localized overgrowth of melanocytes is a nevus or mole

Albinism is an inherited inability to produce melanin - vitiligo is a condition in which there is a partial or complete loss of melanocytes in patches of skin

Carotene - yellow-orange pigment (found in the stratum corneum, dermis, and subcutaneous layer)

Hemoglobin - red color (located in erythrocytes flowing through dermal capillaries)

2/19/2009

A, B, C ’ s of Melanoma

A. Asymmetry

B. Borders

C. Color

D. Diameter

E. Elevation

2/19/2009 19

05_08

21

Subcutaneous Layer

Subcutaneous layer (hypodermis) is not part of the skin but, among its functions, it attaches the skin to the underlying tissues and organs; this layer (and sometimes the dermis) contains lamellated (pacinian) corpuscles which detect external pressure applied to the skin.

2/19/2009

Accessory Structures of the Skin: Objectives Compare the structure and locations of

sweat (sudoriferous), oil (sebaceous), ceruminous, and mammary glands. Also compare the composition and functions of their secretions.

Compare and contrast eccrine and apocrine glands.

List the functions of hair. Describe the cause of acne and its

treatments.

2/19/2009 22

23

Accessory Structures of the Skin include hair, skin glands, and nails Hairs (pili) have a number of important

functions: protection reduction of heat loss sensing light touch

Sebaceous (oil) glands are connected to hair follicles

2/19/2009

24

Skin Glands

Sebaceous glands secrete an oily substance called sebum which prevents dehydration of hair and skin, and inhibits growth of certain bacteria

Sudoriferous (sweat) glands – 2 types: Eccrine sweat glands Apocrine sweat glands

2/19/2009

05_table_03

Acne

Inflammation of sebaceous glands Usually begins at puberty when sebaceous glands

grow and increase production Androgens play the greatest role Due to colonization of glands by bacteria that grow

and thrive in lipid-rich sebum May cause a cyst of sac of connective tissue cells

that can destroy and displace normal tissue with a scar

Treatment c/o benzoyl peroxide or tretinoin, antibiotics (tetracycline or erythromycin) and isotretinoin (accutane).

2/19/2009 26

27

Ceruminous and Mammary Glands Modified sudoriferous (apocrine) sweat

glands located in the ear canal and breast, respectively

Along with nearby sebaceous glands, ceruminous glands are involved in producing a waxy secretion called cerumen (earwax) which provides a sticky barrier that prevents entry of foreign bodies into the ear canal.

Mammary glands produce milk

2/19/2009

Types of Skin: Objectives

Compare and contrast structural and functional differences of thick and thin skin.

2/19/2009 28

05_table_04

30

Functions of the Skin: Objectives Describe how skin contributes to:

regulation of body temperature blood reservoir protection cutaneous sensations excretion and absorption synthesis of vitamin D

2/19/2009

31

Functions of the Skin

regulation of body temperature: liberating sweat on its surface and adjusting flow of blood in the dermis.

blood reservoir: 8-10% of total blood flow in a resting adult

Protection: keratin barrier, lipids serve as barrier and resist dehydration, acid pH, pigment blocks UV, immunologic barrier

2/19/2009

32

Functions of the Skin

cutaneous sensations: touch, pressure, vibration, and tickling; pain

excretion and absorption: small role in excretion of wastes – ammonia and urea; absorption of water soluble substances is negligible, but some lipid soluble materials such as drugs and vitamins K, E, D, and A; steroids

synthesis of vitamin D: requires UV activation then converted to calcitriol in the kidneys

2/19/2009

Skin Wound Healing: Objectives Explain epidermal and deep wound healing.

2/19/2009 33

34

Epidermal Wound Healing: superficial

2/19/2009

Deep wound healing: four phases1. Inflammatory

2. Migratory

3. Proliferative

4. Maturation

Fibrosis – scar Hypertrophic scar - keloid

2/19/2009 35

36

Deep Wound Healing

2/19/2009

37

Aging and the Integumentary System Effects begins in late 40’s:

• Wrinkling, loss of collagen and elastic tissue• decrease of skin’s immune responsiveness: Langerhans cells

decrease and macrophages less effective• dehydration and cracking of the skin: decreased size of

sebaceous glands• decreased sweat production• decreased numbers of functional melanocytes resulting in gray

hair and atypical skin pigmentation• loss of subcutaneous fat• a general decrease in skin thickness• an increased susceptibility to pathological conditions: skin heals

poorly, increased risk skin cancer and pressure sores develop more readily

• growth of hair and nails decreases; nails may also become more brittle with age.

2/19/2009

Burns Tissue damage from excessive heat, electricity,

radioactivity, or corrosive chemicals that destroys (denatures) proteins in the exposed cells is called a burn.

Generally, the systemic effects of a burn are a greater threat to life than are the local effects.

Depending on the depth of damage, skin burns are classified as first-degree and second-degree (partial-thickness) and third-degree (full-thickness) (Figure 5.9)

The seriousness of a burn is determined by its depth, extent, and area involved, as well as the person’s age and general health. When the burn area exceeds 70%, over half of the victims die.

A method for determining the extent of a burn is the rule of nines method (Figure 5.10).

2/19/2009 38

Burns

The injury of skin tissues results in severe systemic effects:

1. Large loss of water, plasma, and plasma proteins may result in shock

2. Risks of bacterial infections markedly increased

3. Reduced circulation of blood results4. Decreased urine output5. Markedly diminished immune responses

2/19/2009 39

05_09

05_10

42

End of Chapter 5

Copyright 2009 John Wiley & Sons, Inc.All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permission Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publishers assumes no responsibility for errors, omissions, or damages caused by the use of theses programs or from the use of the information herein.

2/19/2009