Integumentary System

• Your skin is the largest organ of your body, and protects what lies beneath it

• Also referred to as the cutaneous layer

The “integumentary system” consists of the skin and its derivatives (nails, hair, and skin glands)

The skin is our interface with the outside world

The skin provides protection from the environment

The skin aids in communication

We modify our skin for social reasons

The skin accounts for approximately 7-8% of the body’s weight. It varies in thickness and sensitivity in different regions of the body.

The two principal layers of the skin are the epidermis and dermis. The hypodermis is deeper and connects the dermis to underlying organs

IN PERSONS WHO ARE OBESE, WHERE IS THE MAJORITY OF THEIR FAT LOCATED?

A INSIDE THE PERITONEAL CAVITY

B INSIDE THE DORSAL BODY CAVITY

C BETWEEN THE DERMIS AND MUSCLES

D INSIDE THE VENTRAL BODY CAVITY

E EXTERNAL TO THE EPIDERMIS

Wear protective gloves when handling damaging chemicals that you don’t want absorbed into your body.

When hands are soaked in water, they swell up as water moves by osmosis from an area of high water concentration (the water in the sink) into an area of low water concentration (the skin cells of the hand).

Dermal blood vessels supply nutrients to the dermis and to the overlying epidermis. They also help regulate body temperature.

When body is hot

When body is cold

Vitamin D is synthesized by some epidermal cells when they are exposed to ultraviolet (UV) light. Vitamin D is essential for the process of absorbing calcium and phosphorus from the small intestine for the synthesis of healthy bones.

Rickets is caused by a lack of UV light necessary for the synthesis of Vitamin D or by a dietary lack of Vitamin D

Siberian children getting exposed to essential UV light

Small amounts of UV light are necessary for synthesis of Vitamin D

There is NO good reason for full-body sunbathing!

Excessive UV light has many damaging effects.

Wrinkles in the skin are associated with age and excessive exposure to damaging ultraviolet (UV) light

ACCORDING TO YOUR SUPPLEMENTAL READING, WHY ARE WOMEN IN THE NETHERLANDS MORE LIKELY TO DEVELOP HUMAN PAPILLOMA VIRUS INFECTIONS IN THE MONTH OF AUGUST?

A EXPOSURE TO THE PERINEUM TO UV LIGHT RAYS

B SUPPRESSION OF THE IMMUNE SYSTEM

C INCREASED SEXUAL ACTIVITY AT THE SEASHORE

D LACK OF VITAMIN D

E INCREASED INTESTINAL ABSORPTION OF CALCIUM

There are millions of sensory receptors and numerous blood vessels in the integumentary system.

The skin, through the process of perspiration, eliminates waste products such as water, salts, and urea.

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There are five layers to the epidermis on the palms, soles, and lips

The outermost layer, the epidermis, is 30-50 cell layers in thickness. All but the deepest layers of the epidermis are dead.

The stratum basale only a single cell layer in thickness. These mitotically active cells obtain their nutrients from blood vessels in the underlying dermis. Pigmented melanocytes (which contribute to skin color) are a part of the stratum basale.

Note keratinocytes, tactile (Merkel) cells, and epidermal dendritic cells. Melanocytes, which are found in the stratum basale, are not shown in this photograph.

We are very aware of skin color, even though it is relatively trivial relative to the entire activity and structure of the human body.

The stratum spinosum consists of several layers of cells that have numerous spine-like projections. There is still a limited amount of mitotic activity in this layer, so this layer, and the underlying stratum basale layer, are sometimes collectively referred to as the stratum germinativum.

The stratum granulosum consists of 3-5 layers of flattened cells containing dark staining granules. The process of keratinization begins in this layer.

The stratum lucidum consists of 2-3 rows of clear, flat, dead cells. This layer ONLY exists in the thickened skin of the palms, soles, and in the lips (areas that deal with greater friction).

Fuller lips in women typically occur under the stimulus of increased estrogen released during puberty.

The stratum corneum consists of 20-30 layers of flattened, dead, scale-like cells (cornified cells). These dead cells flake off continuously as we travel through our day.

Chin with beard

Hairy chest

Cornification is brought on by keratinization and the hardening, flattening process that takes place as the cells migrate to the surface.

WHAT LAYER IS ABSENT IN A MALE’S CERVICAL REGION?

A STRATUM LUCIDUM

B STRATUM GERMINATIVUM

C STRATUM GRANULOSUM

D SUBCUTANEOUS

E STRATUM CORNEUM

Friction on the skin stimulates increased mitotic activity in the stratum basale

A callus is the result of stimulation of the stratum basale cells

The colored dye must go below the stratum basale into the dermis in order to stay permanently.

Read about transdermal patches in the clinical view in the text.

Thick epidermis is found on the palms of the hands and soles of the feet. All five epidermal layers are present, but no hair follicles or sebaceous (oil) glands.

Thin epidermis covers most of the body and only has four epidermal layers (lacks stratum lucidum). It also has hair follicles and sebaceous (oil) glands.

Normal skin color is caused mainly by the expression of a combination of two pigments: melanin in the epidermis and hemoglobin in the dermal blood vessels. Carotene is the weakest contributor.

Melanin is believed to help protect the DNA of epidermal cells from damage by harmful UV light.

Read in the clinical view in the text how sunscreens protect against UV radiation.

Red blood cells in capillaries

Hemoglobin, the iron containing pigment found inside red blood cells, gives the skin its pinkish tones.

The role of blood (hemoglobin) in skin color can be demonstrated by pressing on the nails. The blanching (whitening) occurs because the capillaries are compressed, which forces the blood out.

Carrots and many other vegetables contain carotene, which may influence skin color.

View of a man’s back before, and after, eating several large carrots with each meal for four weeks. Notice orange skin color as a result of accumulated carotene. However, for most persons, carotene is not that significant a contributor to skin color.

before after

WHICH OF THE FOLLOWING IS ASSOCIATED WITH ALBINISM AND VITILIGO?

A LACK OF VITAMIN D

B DEFECTIVE CELLS IN STRATUM BASALE

C LACK OF CAROTENE

D ANEMIA

E EXPOSURE TO UV LIGHT

Blueness (cyanosis) is a sign of poor oxygenation of the blood

Acrocyanosis is blueness of the extremities (fingers and toes) caused by poor oxygenation of hemoglobin (formation of deoxyhemoglobin, which has a bluish tint).

Hand of person with anemia. Note pallor.

Normal hand

Pallor (paleness) is an indication of a lack of hemoglobin, a lack of red blood cells, or both.

Jaundice, caused by excess bilirubin

Postmortem lividity (livor mortis)

Postmortem lividity (livor mortis). Note blanching caused by the examiner pressing on back with his fingers.

Mole (nevus)

A more famous nevus!

Freckles are genetically-determined (but triggered by sunlight) aggregated patches of melanocytes. The gene is dominant.

Hemangioma, which is a congenital abnormality that results in skin discoloration due to blood vessels that proliferate. Hemangiomas are the most common childhood tumor, occurring in approximately ten percent of Caucasians (more likely in females). They are benign and most disappear by age 10.

Epidermal friction ridges (fingerprints) caused by underlying dermal papillae.

Read about dermatoglyphics in the clinical view in the text

The dermis is deep to the epidermis and superficial to the hypodermis.

Note blood vessels

The outermost layer of the dermis is the stratum papillarosum

Note interlocking epidermal ridges and dermal papillae

Nerve endings in dermis

Stratum reticularosum

Striae (linea albicantes)

A decrease in skin elasticity leads to wrinkles and skin sagging as a person ages. Excessive exposure to UV light can accelerate this process.

Elastic fibers in the dermis are responsible for lines of cleavage

Dermal nerve endings are very sensitive

Dermal blood vessels vasoconstrict to reduce the loss of heat to the outer environment. This typically causes the skin to whiten as may occur on very cold days.

Skin typically becomes pale in cold environment as dermal blood vessels constrict.

Dermal blood vessels vasodilate to allow the elimination of heat to the outer environment. This typically occurs during exercise when the body is hot and may cause the skin to redden.

Skin typically becomes flushed and reddish as dermal blood vessels dilate to eliminate excess heat.

BLUSHING, A REDDING OF THE FACE SEEN IN PERSONS WHO ARE EMBARASSED, IS CAUSED BY WHICH OF THE FOLLOWING?

A ALTERED DERMATOGLYPHIC SKIN PATTERNS IN RESPONSE TO NERVE STIMULATION

B EPIDERMAL BLOOD VESSELS

C VASOCONSTRICTION

D FLATTENING OF DERMAL PAPILLAE

E LOCALIZED INCREASE IN CIRCULATING BLOOD CELLS

Decubitus ulcers (bed sores) occur whenever there is continuous pressure on a body part or region.

Common locations where blood flow is compromised (which results in cell death) when continuous pressure is applied.

Continuous pressure, and lack of blood flow, will lead to cell death

Decubitus ulcers on sacrum and upper thigh of an elderly bed-ridden female.

All of these bed sores communicate under the skin of this elderly male

Christopher Reeve, a very famous quadriplegic, died from an infection that originated in a decubitus ulcer.

Decubitus ulcers (bed sores) can be prevented by turning a patient every two hours if they are unable to move themselves.

Hypodermis (subcutaneous layer) is the deepest layer

The hypodermis consists of loose fibrous connective tissue, blood vessels, and fat (adipose tissue). It binds the dermis to underlying organs.

Proven method of developing a thick hypodermis (subcutaneous layer)

Summary of skin layers

Hypodermis

This man does NOT have an enlarged abdominal cavity. He does have a very thick hypodermal layer, much like a whale.

Large intestine

Thick hypodermis

Opened peritoneal cavity

Liposuction is a brutal surgery done with a large blunt needle hooked up to a vacuum system.

Newspaper ad from 2003

Nails are found on the distal dorsum of the digits. The nails are protective and help in grasping small objects.

Nails are an epidermal derivative.

Read about nail disorders in the clinical view of your text

ACCORDING TO YOUR NOTES AND ASSIGNED READING OF CLINICAL VIEWS IN YOUR TEXT, WHICH OF THE FOLLOWING CAN CAUSE BOTH PALLOR OF THE SKIN AND SPOON NAILS?

A CHRONIC BRONCHITIS

B IRON DEFICIENCY

C UREMIA

D FUNGAL INFECTIONS

E TESTOSTERONE

Hair (pili) distribution varies

When you look closely, hair (pili) are found over most of the body in both males and females. Its primary function is protection.

Shedding epidermal cells and shaft of hair. All that is shown is dead.

The hair follicle and its enclosed hair shaft are products of the epidermis

The sebaceous glands (highlighted in blue) lubricate and waterproof the hair

Magnified view of human hair shafts.

The arrector pili muscle pulls the hair so it takes on a more straight up position

Contraction of arrector pili muscles fluffs the fur so to appear larger to enemies and to increase thickness of insulation when cold.

Note effect of arrector pili muscles contracting in skin of cat’s tail.

Contraction of arrector pili muscles in a human’s arm (goose bumps). This achieves neither increased size to frighten enemies nor does it provide additional insulation when cold.

Hair aids in protection, heat retention, facial expression, sensory reception, visual identification and chemical signal dispersal

The skin sends important information to sensory endings (vomeronasal organ) in the nose.

Pheromones appear to affect both fertility and behavior

ACCORDING TO YOUR SUPPLEMENTAL READING, WHICH OF THE FOLLOWING BEST EXPLAINS WHY WOMEN LIVING IN COLLEGE DORMITORIES OFTEN HAVE SYNCHRONIZED MENSTRUAL PERIODS?

A SIMILAR WAKING AND SLEEP CYCLES

B UNIFORM ENCOUNTERS WITH MALE STUDENTS AND THEIR SHED SKIN CELLS ON CAMPUS

DURING PORLONGED CLASSES

C ISOPROPHYL ALCOHOL IN COSMETICS

D AXILLARY SECRETIONS

E ESTROGENIC EFFECTS OF LANOLIN IN BODY LOTIONS

White hair is caused by a lack of melanin in the stratum basale of the base of the hair follicle when the hair is being formed.

Hair loss can be caused by dietary deficiencies, high fever, radiation, drugs, genetics, changes in hormonal levels, or aging

Sudoriferous glands typically produce sweat to help regulate body temperature.

Sudoriferous glands in use to help with temperature regulation

Note numerous sweat gland openings on friction ridges of finger

Mammary glands inside the breasts of males and females are specialized sudoriferous glands that can secrete milk.

Ceruminous glands are only found within the ear canal. They produce ear wax (cerumin).

External ear

Cerumin (ear wax) on hairs in ear canal

Sebaceous glands (oil glands) make sebum to keep hair supple

Sebum, produced by sebaceous glands, keeps the hair and skin supple

Read about acne and its treatments in the clinical view in your text

WHICH OF THE FOLLOWING IS MOST IMPORTANT IN MAINTAINING HOMEOSTASIS OF THE HUMAN BODY DURING THE MONTHS OF JUNE AND JULY IN LOGAN?

A SUDORIFEROUS GLANDS

B ARRECTOR PILI MUSCLES

C ANTEBRACHIAL PILI

D SEBACEOUS GLANDS

E. HARDENED TRANSPARENT STRATUM CORNEUM AT DISTAL ENDS OF DIGITS

Burns can be caused by heat, radiation, chemicals, or by electricity. Read about types of burns and grafts in the clinical view in your text.

Skin grafts needed

Healthy skin

Donor site

Recipient site

Completed skin grafts

Superficial scratch on hand will heal by inward migration of stratum basale cells from the margins (epithelial regeneration)

Epithelial regeneration

Deeper wounds may heal with formation of granulation tissue that fills in the gap.

Fibrosis

Fibrosis

Microscopic view of Staphylococcus aureus

Impetigo is often caused by the bacterium Staphylococcus aureus

Scalded Skin Syndrome, occasionally confused with intentionally caused burns, is actually caused by the bacterium Staphylococcus aureus.

Aging causes the skin to thin, sag, wrinkle, more susceptible to infection, become drier, more susceptible to skin cancer, and hairs loose their pigmentation.

Aging of the skin

Liver spots, that occur with aging, are benign growths of melanocytes

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