HUMAN ANATOMYFifth Edition

Chapter 1 Lecture

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Chapter 4 Lecture

Chapter 4The Integumentary

SystemFrederic Martini

Michael Timmons

Robert Tallitsch

Introduction

The integumentary system or integument is composed of skin, hair, nails, sweat, oil, and mammary glands.

– Skin tells clinicians about the overall health of the body and can be used to detect some internal problems.

Integumentary Structure and Function

– Integument covers the entire surface of the body, including the eyes and eardrum.

– All four tissue types are found in the integument.1- An epithelium covers the surface.

2- Connective tissue provides underlying stability.

Blood vessels are abundant within the CT.

3- Smooth muscle is found in the walls of blood vessels in the integument, and attached to hairs.

4- Neural tissue controls the blood vessels as well as provides sensation.

– Function of the integument includes:• Physical protection

• Regulation of body temperature

• Excretion (secretion)

• Nutrition (synthesis)

• Sensation

• Immune defense

The integument has two major parts:

1- Skin, or the cutaneous membrane has it own

two subdivisions.

A- Epidermis is the stratified squamous epithelium of

the skin.

B- Dermis is the underlying loose CT.

» Deep to the dermis is the subcutaneous layer

(superficial fascia or hypodermis), which is not

part of the skin but will be discussed in this

chapter because of the vast interconnections it

has with the dermis.

2- Accessory structures include hair, nails, and

many multicellular exocrine glands.

The Epidermis p. 87

• The epidermis is a stratified squamous

epithelium that contains four cell types.1- Keratinocytes are the most abundant cells in

the epidermis.

– At least four different cell layers can be found on

most areas of the body.

2- Melanocytes are pigment cells found deep in

the epidermis.

3- Merkel cells are sensory cells.

4- Langerhans cells are fixed macrophages.

Figure 4.1 Functional Organization of the Integumentary System

Integumentary Structure and Function

Integumentary Structure and Function

– Layers of the Epidermis will be considered from the basal lamina toward the surface.

1- Can (Corneum)

2- Lucy ( Lucidum)

3- Give (Granulosum)

4- Some (Spinosum)

5- Blood (Basal) ( Germinativum)

5- Stratum germinativum or stratum basale is the deepest layer of the epidermis and is attached to the basal lamina.

– Basal cells, which are stem cells, divide in this region to replenish the more superficial layers.

– Melanocytes are pigment-producing cells found in this layer that secrete the pigment melanin into other cells.

» Melanocytes are more numerous in the forehead, nipples, and genital regions.

– Merkel cells are sensory cells found in this layer in areas where there is no hair.

1. deepest layer of the epidermis

2. single layer of cuboidal-columnar shaped cells

3. origin of all cells of epidermis through mitosis

4. origin of cells for sweat-oil glands and hair

4- Stratum spinosum is the next most

superficial layer.

– Keratinocytes in this layer take on a spiky

appearance due to the production of interconnecting

proteins called tonofibrils.

» The tonofibrils greatly increase stability in this

layer.

– Langerhans cells account for about 5% of the cells in

this layer.

» These fixed macrophages are the first cells of the

immune system to encounter any foreign object

the tries to penetrate the skin.

» They also play a role in monitoring of cancerous

epidermal cells.

» 1. 8-10 rows of polyhedral shaped cells

» 2. contain spine-like projections ("spinosum")

»3- Stratum granulosum receives its

name because of dense granules found in their

cytoplasm.

– Keratohyalin and keratin are proteins manufactured

by the keratinocytes in this layer.

– Keratohyalin is packaged in granules that surround

the keratin filaments.

– Keratinocytes in this layer also become thinner,

however they become less permeable due to

thickening cell membranes and the keratohyalin.

– 1. cells from lower layers begin to die here

– 2. contain granules with keratohyalin

– 3. keratohyalin is precursor to eleidin and keratin

Integumentary Structure and Function

2- Stratum lucidum is only found in the thick skin of the palms and soles.

– The cells in this layer are very similar to those in the superficial layers of the granulosum, however they do not stain well.

– 1. Present only in thick areas (palms, feet)

– 2. Contain clear substance called eleidin

– 3. Eleidin eventually changes into keratin at surface

1- Stratum corneum is the surface layer of dead cells found on all areas of the skin.

– This layer is usually 15-30 cells thick of interlocked cells.

» The connections between cells cause them to be shed in sheets.

– Keratinized is the term for an epithelium containing a large amount of keratin.

» The relatively dry covering that results is unsuitable for microorganism growth.

» Keratinization occurs everywhere on the surface of the skin except the anterior surface of the eyes.

Figure 4.2 Components of the Integumentary System

Integumentary Structure and Function

Table 4.1 Epidermal Layers Figure 4.3 Structure of the Epidermis

Layers of the Epidermis

The Epidermis

Skin Color is produced by a combination of two factors.– Dermal blood supply

1- Decreased blood flow can cause one to become pale.

» Cyanosis, a bluing coloration, is the result of long term decreased blood flow causing hypoxia in the area.

2- Increased blood flow will cause a pink “blush”.

– Epidermal pigment content

» Carotene is a yellow-orange pigment found in some vegetables that may become trapped in the epidermis.

» Melanin is the dark pigment produced by the melanocytes.

» Vesicles called melanosomes are transferred from melanocytes to keratinocytes.

» If large melanosomes are transferred in the granulosum layer the individual tends to have darker skin.

» If smaller melanosomes are transferred in the spinosum layer the individual will have lighter skin.

Figure 4.4 Thin and Thick Skin

Thick and Thin Skin

Thick and Thin Skin Figure 4.4 p. 89

– The references to thick and thin skin are made relative to the thickness of the epidermis and not the entire thickness of the skin.

– Most of the body is covered with thin skin, having four distinct layers.

– Thick skin contains the stratum lucidum and may have 30 layers of keratinized cells.

• Folds in the stratum germinativum that extend into the dermis form epidermal ridges.

– By contrast the dermis contains folds that fit in between

the epidermal ridges called dermal papillae.

– The interlocking structures increase the stability of the skin.

– In thick skin, on the palms and sole, the ridges and papillae are very pronounced and can be seen and felt on the surface.

» These fingerprints increase the surface area

of the skin covering the digits and therefore help

with gripping objects.

» Ridges and papillae are genetically determined

and are different in everyone, and therefore can

be used to identify individuals

» Ultraviolet radiation triggers melanin production

and can lead to tanning.

» Melanin normally surrounds the nuclei of cells to

protect them from the UV radiation.

» Therefore UV radiation triggers more melanin

production.

Figure 4.2 Components of the Integumentary System

The Dermis and Subcutaneous Layer

The Dermal Organization p. 91

The dermis is deep to the epidermis and is a mixture of areolar CT and dense irregular CT.

1- The superficial papillary layer contains areolar

connective tissue.

- Abundant blood vessels are found in the region.

Neural tissue is also found here.

2- The deeper reticular layer consists of dense irregular CT.– Blood vessels, glands, muscles, hair follicles and nerves are all found in

this layer.

(VAN) ( Vein- Artery- Nerve)

• Collagen fibers in the reticular layer extend into the papillary layer and deeper into the subcutaneous layer to bind everything together.

– The boundaries between layers are very indistinct.

• Wrinkles, Stretch Marks, and Lines of Cleavage– Elastic fibers in the dermis afford a great deal of stretching.

– Excessive stretching can permanently break the elastic fibers resulting in wrinkles and stretch marks.

Figure 4.7 The Structure of the Dermis and the Subcutaneous Layer

Dermal Organization and the

Subcutaneous Layer

Other Dermal Components

– Lines of cleavage are made by patterns of parallel

elastic and collagen fibers in the dermis.

1- Cutting across a line of cleavage results in the

elastic fibers pulling the incision open, resulting

in scarring.

2- Cutting parallel to the lines of cleavage is

favorable to fast healing with minimal scarring.

• The Blood Supply to the Skin

1- Cutaneous plexus is the network of blood vessels

at the border of the reticular layer and the

subcutaneous layer.

2- Papillary plexus is the highly branch network of

blood vessels just deep to the epidermis.

Circulation to both plexi are important due to their

role in thermoregulation and overall blood flow.

• The Nerve Supply to the Skin

– Nerve fibers to the skin are involved in:

» Regulation of blood flow

» Regulation of glands

» Sensations

» Tactile discs form with the union of a Merkel cell and a

sensory nerve ending.

» Free dendrites are sensitive to pain and temperature.

» Other receptor of the skin will be noted in Chapter 18 .

( Pain - Touch)

A- Tactile corpuscles (light touch)

B- Root hair plexus (light touch)

C- Ruffini corpuscles (stretch)

D- Lamellated corpuscles (deep pressure and

vibrations)

Figure 4.9a Accessory Structures of the Skin

Accessory Structures

• Hair follicles and hair:

– Hair is a nonliving keratinized structure that extends beyond the surface of the skin in most areas of the body.

– 98% of the 5 million hairs on the body are not on the head.

– Hair follicles are the organs that form the hairs.

The Subcutaneous Layer p. 93

The subcutaneous layer (hypodermis or superficial fascia) is not technically part of the skin.

– The subcutaneous layer is a mixture of areolar and adipose tissues.

– Adipose tissue distribution is highly individual, however common patterns are seen in males and females.

• Males – neck, upper arms, lower back, and buttocks.

• Females – breasts, buttocks, hips and thighs.

• Both – abdomen.

– Because no vital organs are in this region it is a great location for injection of drugs through a hypodermic needle.

• Accessory Structures p. 93– All accessory structures have a common origin

as invaginations of the epidermis.

Figure 4.12 A Classification of Exocrine Glands in the Skin

Glands in the Skin

Hair Follicles and Hair. F 4.9 p. 93 – Hair is a non-living keratinized structure that extends beyond the surface of the skin in

most areas of the body.

» 98% of the 5 million hairs on the body are not on the head.

– Hair follicles are the organs that form the hairs.

Hair Production comes from growth from a hair follicle.– The hair papilla is an area of CT at the base of the hair follicle.

» The hair bulb is the area of epithelial cells that surround the papilla.

» Hair matrix is the specialized area of epithelium that grows the hair.

» Basal cells divide and push the hair toward the surface.

» Each hair has two major areas.

1- The medulla is the inner portion.

» It contains soft keratin, which allows it to be flexible.

2- Cortex is produced by the outer cells of the hair matrix.

» Hard keratin in the cortex makes it stiff.

» A single outer layer of dead cells forms the cuticle.

– The portion of the hair that is attached to the follicle is the hair root.

– The portion of the hair exposed to the surface is the shaft.

• Follicle Structure involves the layering of cells.1- Internal root sheath is a layer of cells that surrounds the hair root and deeper parts of the

shaft.

2- External root sheath is superficial to the internal root sheath and resemble the layer of the epidermis. It extends the entire length of the follicle.

3- Glassy membrane is the thickened basal lamina of the epidermis.

Functions, Tyapes and Color of Hair

• Functions of Hair– Protection of the scalp from UV light, blows to the head and thermoregulation.

– Trapping of particles in the nasal passageway and external auditory canals.

– The root hair plexus provides sensation.

– Arrector pili allow movement of hairs, as in “goose bumps”.

• Types of Hair

– The first hairs are produced before birth and are called lanugo.» Most lanugo is shed before birth and is replaced by one of three types of adult

hairs, vellus, intermediate, or terminal.

1- Vellus hairs are the fine, colorless “peach fuzz” that covers most of the body.

2- Intermediate hairs are thin, colored hairs common to the limbs and groin.

3- Terminal hairs are the coarse, deepest pigmented hairs found on the head and face.

» Follicles can alter structure for a variety of reasons resulting in different types of hair at different developmental stages.

» Vellus to intermediate at puberty.

» Terminal to intermediate or vellus in balding.

• Hair color is determined by pigment production of the melanocytes in the follicle. – Greater amounts of melanin result in darker hairs.

– Red hair is the result of an altered melanin pigment.

– Hormones and age play roles in hair color as well.

Growth and Replacement of Hair

• The hair growth cycle lasts about 2-5 years.

– Growth occurs with an intact follicle.

– At the end of a growth cycle the follicle become

inactive and the hair is known as a club hair.

» The club hair separates from the follicle and

when a new cycle begins the club hair is push

toward the surface.

– Loss of 50 hairs per day is normal.

– Male pattern baldness is the result of hormonal

changes resulting in a shift to vellus hair

production.

Hirsutism– Excess hair in females and children with an adult

male pattern of distribution. The concept does not

include HYPERTRICHOSIS, which is localized or

generalized excess hair.

• Glands

• A. Sebaceous Glands (oil glands)

• 1. genearlly connected to hair follicles

• 2. simple branched acinar glands

• 3. sebum - mixture fat, protein, cholesterol, salt

• 4. prevent dessication, keep skin soft, anti-bacterial

• a. infected gland - acne, blackheads

• B. Sudoriferous Glands (sweat glands)

• 1. Apocrine Sweat Glands

• a. simple branched tubular glands

• b. only in axilla (arm pit), pubic + areole areas

• c. in dermis, duct opens into a hair follicle

• 2. Eccrine Sweat Glands

• a. simple coiled tubular glands

• b. all over the body

• c. subcutaneous, opens onto epidermal surface

• 3. Perspiration (sweat)

• a. mixture of water, salt, urea, ammonia, acids

• b. eliminates waste and heat

• C. Ceruminous Glands

• 1. simple coiled tubular glands

• 2. in the external auditory meatus (canal)

• 3. cerumen - wax-like substance, prevents entry

Glands in the Skin F 4.12 P. 96

• Sebaceous glands are exocrine glands that discharge oily secretions into hair follicles.

– Lipids are the main component of the secretions that are released by the holocrine mode of secretion.

– The glands may be simple alveolar, or simple branched alveolar glands.

– The glands release the lipids, called sebum, into the open passageway (lumen) of a duct.

» Sebum lubricates hairs and prevents bacterial growth. Sebaceous follicles are large sebaceous glands that do not attach to a hair follicle.

» Locations of sebaceous follicles include the:

» Face

» Back

» Chest

» Nipples

» Male sex organs

» Folliculitis is the inflammation of a sebaceous follicle resulting in a boil, or furuncle.

Sweat glands

• Sweat glands or sudoriferous glands are found throughout the surface of the body.

» Myoepithelial cells are small contractile cells that squeeze the secretion, or sweat, out of a sweat gland.

– Apocrine sweat glands are found in the axillae, around the nipples and in the groin.

» Apocrine sweat glands get their name from the first proposed mode of secretion.

» It is now known that apocrine sweat glands use the merocrine mode of secretion, however the name persists.

» Apocrine glands are large coiled tubular glands that extend very deep into the dermis and even the subcutaneous layer.

» Secretion is a viscous, cloudy, and potentially odorous secretion.

» Bacteria may act on the secretion changing its biochemical makeup, causing an undesirable odor.

» Apocrine secretions also contain pheromones.

Is a Chemical substances which, when secreted by an individual into the environment, cause specific reactions in other individuals, usually of the same species . Sex Activity

Merocrine sweat glands

– Merocrine sweat glands or eccrine sweat glands are far more numerous than

apocrine sweat glands.

» The highest density of these glands is on the palms and soles.

» Merocrine sweat glands are smaller glands than apocrine glands, but are also coiled tubular glands.

» Merocrine sweat glands do not extend as deeply into the dermis as the apocrine glands.

» Sweat or sensible perspiration is released by these glands.

» 99% water

» 1% electrolytes

» Sweat functions in:

» Thermoregulation – sweat cools the surface of the skin and reduces body temperature.

» Excretion – water and electrolytes.

» Protection – dilution of chemicals on skin and bacteriocidal.

• Control of Glandular Secretions

– The autonomic nervous system control glands.

» Sebaceous glands and apocrine glands have not

precise control – just on or off for all of them.

» Merocrine sweat glands have more precise

control. Therefore sometimes only a certain area

may sweat.

• Other Integumentary Glands

– Mammary glands are milk-producing glands found in

the breast that are anatomically related to apocrine

sweat gland.

– Ceruminous glands are modified sweat gland in the

external auditory canal.

» Secretions from these glands mix with those of

nearby sebaceous glands to form cerumen, or

earwax.

Figure 4.15 Structures of a Nail

Nails

Nails F 4.15 P. 101

– Nails are special keratinized structures of the

epidermis that cover the dorsal surfaces of the

distal digits.

• Nail body is the actual nail.

• Nail bed is the epithelium under the nail body.

• Nail root is a fold in the epidermis near the bone of the

digit. The nail body grows from this region outward.

• Nail grooves are the lateral borders of the nail body.

• Nail folds are the upward folds in the epidermis lateral to

the nail grooves.

• Eponychium is the cuticle, an extension of the proximal

nail fold that covers the nail root.

• Lunula is the pale area near the eponychium.

• Hyponychium is the fold of epidermis deep to the distal

nail body.

• VII. Nails

• A. Nail Body - portion resting in the digit itself

• B. Free Edge - extends from the end (part you cut)

• C. Nail Root - extends from the proximal nail groove

• a. lunula - whitish semilunar area

• b. eponychium (cuticle) - extension of epidermis

• c. nail matrix - superficial cells -> nail cells

• VIII. Skin Color

• A. Melanin - pigment made in melanocytes

• 1. in basale and spinosum layers of epidermis

• 2. melanoblasts -> melanocytes in stratum basale

• 3. darkness due to melanin quantity (not cell #)

• 4. albinism - inability to produce melanin

• 5. vitligo - patchy loss of melanocytes

• 6. freckles - patchy concentration of melanocytes

• 7. UV light causes: tyrosine --> melanin production

• B. Carotene

• 1. in stratum corneum and fatty areas of dermis

• 2. melanin + carotene = yellowish color

• C. Other Colors

• 1. pink (Caucasian) - lack of pigment, capillaries

• 2. blue (cyanosis) - lack of oxygen in blood

• 3. yellow (jaundice) - liver disorder, protein release

Embryology Summary P.98-99

– The Development of the Integumentary System At the start of the second month a simple epithelium overlies

the mesenchyma.

• Germinative cells thicken the epithelium in the next few weeks.– Skin formation involves:

» Thickening of the epithelium

» Melanocyte migration

» Differentiation of mesenchyma to dermis.

– Nail formation involves:

» Keratinization of the epidermis of the distal digits.

– Hair follicle formation involves:

» Columns of epidermal cells digging into the dermis.

» Epidermal cells surrounding a hair papilla.

» Sebaceous gland formation.

Local Control of Integumentary Function

Exocrine gland formation involves:

» Columns of epidermal cells digging into the

dermis.

» The column hollows to form a duct.

» Deep cell differentiate into secretory cells.

The integument can respond independently

of the endocrine system and nervous

system.

• Mechanical stress can trigger stem cell

divisions resulting in calluses.

• Regeneration occurs after damage.

– The inability to completely heal after severe

damage may result in acellular scar tissue.

• IX. The Healing Process : How Skin Repairs Itself

• A. Superficial Wound Healing - Epidermal Repair

• 1. epidermal cells of stratum basale migrate over area

• 2. contact inhibition - cells stop when they meet

• 3. dead cells sluff off (scab) as new cells replace

• B. Deep Wound Healing - Dermal Repair

• 1. inflammatory phase - blood clot, fibroblasts

•

• 2. migratory phase - scab forms, epidermal migration

• a. fibroblasts make scar tissue (collagen fibers)

• b. damaged vessels grow into place

• c. granulation tissue - new scar tissue in place

• d. fibroplasia - period of scar fromation

• i. hypertrophic scar - normal

• ii. keloid scar - abnormal

•

• 3. proliferative phase - new growth

• a. epithilium grows beneath scab

• b. fibroblasts make random collagen deposit (scar)

• c. blood vessels continue to grow

•

• 4. maturation phase - final healing process

• a. epidermis is restored

• b. fibroblasts disappear, collagen more organized

• c. blood vessels repaired to normal

Aging and the Integumentary System p. 102

– The epidermis thins as germinative cell activity declines.

– The number of Langerhans cells decreases, affecting the immune system.

– Vitamin D production declines, leading to calcium deficiency.

– Melanocyte activity declines.

– Glandular activity declines, reducing the ability to cool oneself.

– Blood supply to the dermis decreases, further reducing cooling ability.

– Hair follicles stop functioning, or produce thinner hairs.

– The dermis thins and loses elastic fibers, resulting in wrinkles.

– Secondary sex characteristics of the integument fade.

– Skin repair slows.

• X. Skin Cancers

• A. Basal Cell Carcinoma

• 1. Least malignant and most common skin cancer

• 2. Stratum basale cells proliferate and invade the dermis and hypodermis

• 3. Slow growing and do not often metastasize

• 4. Can be cured by surgical excision in 99% of the cases

• B. Squamous Cell Carcinoma

• 1. Arises from keratinocytes of stratum spinosum

• 2. Arise most often on scalp, ears, and lower lip

• 3. Grows rapidly and metastasizes if not removed

• 4. Prognosis is good if treated by radiation therapy or removed surgically

• C. Melanoma (most dangerous type of skin cancer)

• 1. Cancer of melanocytes

• 2. Highly metastatic

• 3. Resistant to chemotherapy

•

• Melanomas have these characteristics (ABCD rule)

• A: Asymmetry; the two sides of the pigmented area do not match

• B: Border is irregular and exhibits indentations

• C: Color (pigmented area) is black, brown, tan, and sometimes red or blue

• D: Diameter is larger than 6 mm (size of a pencil eraser)

• XI. Burns of the Skin

• A. First-degree – only the epidermis is damaged– Symptoms include localized redness, swelling, and pain

• B. Second-degree – epidermis and upper regions of dermis are damaged– Symptoms mimic first degree burns, but blisters also appear

• C. Third-degree – entire thickness of the skin is damaged– Burned area appears gray-white, cherry red, or black; there is no initial edema or pain (since nerve endings are destroyed)

• Burns considered critical if:– Over 25% of the body has second-degree burns

– Over 10% of the body has third-degree burns

– There are third-degree burns on face, hands, or feet

Figure 4.16 The Skin during the Aging Process

Aging and the Integumentary System