ch. 4 skin and body membranes

Skin and Body MembranesSkin and Body Membranes

Human Anatomy and Physiology

Mr. McCammon

I. Classification of Body I. Classification of Body MembranesMembranes

Epithelial Membranes include the cutaneous membrane (skin) and the mucus membranes, and the serous membranes.

Always combined with an underlying layer of connective tissue.

That’s why it is considered an organ.


Cutaneous Membrane– This is your skin.– Composed of keratinizing stratified squamous

epithelium.– Underlying dermis is dense (fibrous)

connective tissue.– Exposed to air and is dry.


Mucous membranes (or mucosa) – composed of epithelium (the type varies from

site to site) resting on a loose connective tusse membrane called a lamina propria.

– Lines all the cavities that open to the exterior such as respiratory, digestive, urinary, and reproductive tracts.

– Always moist because they are continually bathed in secretions.


Serous Membranes (serosa)– Layer of simple squamous epithelium resting

on a thin layer of areolar connective tissue.– Line the body cavities that are closed to the

exterior (except for the dorsal body cavities and joint cavities)

– Occur in pairs – parietal layer lines a specific portion of the wall of the ventral body cavity and folds in on itself to form the viseral layer with covers the outside of the organs in that cavity.


The serous layers are separated by a clear fluid called serous fluid.

Important to decrease friction by moving organs (heart, stomach)

Some serous membranes– Peritoneum – abdominal cavity– Pleura – around the lungs– Pericardium – around the heart


Synovial membranes are composed of connective tissue and contain no epithelial cells at all.

Line the fibrous capsules surrounding joints where they provide a smooth surface and secrete a lubricating fluid.

Contain small sacs of connective tissue called bursae and tubelike tendon sheaths – both cushion organs moving against each other during muscle activity.

II. The Integumentary SystemII. The Integumentary System

The Skin– Includes cutaneous membrane, sweat and oil

glands, hairs, and nails– External body covering– Keeps water and other molecules in the body.– Keeps and other things out– Pliable yet tough

II. The Integumentary SystemII. The Integumentary SystemStudy chart on page 95.The structure of the skin.

– EpidermisStratified epithelium – becomes keratinizing

(hard and tough)– Dermis

Dense connective tissueBoth connected tightly until a burn or

friction causes a blister.


Deep down in the skin is the subcutaneous tissue or hypodermis – Basically adipose tissue– Not considered part of this skin, but does

anchor the skin to the underlying organs.– Shock absorber and protected from temperature

changes.– Makes you ‘curvy’

II. The Integumentary SystemII. The Integumentary SystemKNOW THE DIAGRAM ON PAGE 96.The Epidermis in Detail

– 5 zones (layers) called strata In order, basale, spinosum, granulosum, lucidum,

corneum.They are avascularMost cells are keratinocytes (produce fibrous

protein that makes the epidermis tough.Deepest layer is stratum basale lies closes to the

dermis and contains the only cells that receive adequate nourishment via diffusion from the dermis.


Cells from the stratum basale are constantly dividing and pushed up to become part of the epidermis.

Stratum lucidum only occurs where the skin is hairless and extra thick (palms, feet)

Stratum corneum makes up ¾ of our body.Constant replaced – New epidermis every

25-45 days.

II. The Integumentary SystemII. The Integumentary SystemMelanin – yellow to brown pigment is

produced by cells called melanocytes found in the stratum basale.

Sunlight stimulates melanin production causes tanning.

Melanin forms a protective shield from sunlight so it doesn’t affect genetic material.

Freckles and moles are where melanin is concentrated in one spot.

II. Integumentary SystemII. Integumentary System

Excessive exposure can lead to skin cancer.It can cause the elastic fibers to clump and

lead to leathery skin.Black people seldom have skin cancer

because melanin is an effective shield against it.


The Dermis– Your ‘hide’ – strong, stretchy envelope

that helps to hold the body together. Leather goods are just treated dermis of animals.

– Two regionsPapillary layer reticular layer


The Papillary Layer is the upper dermal region– Uneven with finger like projections called

dermal papillae– Contain capillary loops which nourish the

epidermis– Pain receptors touch Meissner’s corpuscles.– On hands and feet papillae are arranged in

patterns to enhance gripping ability.


Reticular layer– Deepest layer– Contains seat, blood vessels, sweat and oil

glands, deep pressure sensors called Pacinian corpuscles

– Collagen and elastic fibers make it tough– Restrictions of blood in the dermis results in

cell death and causes Decubitus ulcers (bedsores)


Skin Color– The amount and kind of melanin in the dermis– The amount of carotene deposited in the

stratum corneum (carotene is an orange yellow pigment

– The amount of oxygen bound to hemoglobin (pigment in red blood cells)


People with lots of melanin have brown-toned skin.

Light skinned people (caucasian) people have less melanin and have a crimson color due to oxygen-rich blood.

Then hemoglobin is poorly oxygenated the skin can become blue (cyanosis) – common during heart failure and breathing disorders

II. The Integumentary SystemII. The Integumentary SystemSkin color

– Redness or erythema – may indicate embarrassment (blushing), fever, hypertension, inflammation, or allergy.

– Pallor or blanching – becoming pale – fear, anger, stress, anemia, low blood pressure, impaired blood flow

– Jaundice or yellow cast – liver problems– Bruises or black-and-blue marks – sites where

blood has escaped from circulation and has clotted in the tissue spaces – called hematomas

III. The Appendages of the III. The Appendages of the SkinSkin

Cutaneous glands – all exocrine glands that release their secretions to the skin surface via ducts.

Two groups– Sebaceous glands– Sweat glands

Form in Stratum basale but push lower into the dermis

III. Appendages of the SkinIII. Appendages of the Skin

Sebaceous (oil) glands – found all over the body except palms of hands and feet.

Most open onto a hair follicle, but some open directly onto the skin.

Sebum is the name of the oil – mixture of oil and fragmented cells that keep the hair and skin moist. Kills bacteria

Increase in male hormones increase sebum during adolescence.


If a sebaceous gland’s duct becomes blocked by sebum a whitehead forms. If the whitehead dries it becomes a blackhead.

Acne is an active infection of the sebaceous glands

Severe acne results in scarring of the skin.


Sweat Glands – Sudoriferous glandsCan be as many as 2.5 million per personTwo types

– Eccrine– Apocrine


Eccrine glands– More numerous– Produce seat

Water, salt, vitamin C, ammonia, urea, uric acid, and lactic acid (which attracts mosquitoes)

Sweat is acidic (ph 4-6) which kills bacteria Reaches the skin by a funnel-shaped pore. They secrete sweat when the external or body

temperature is high.


When the sweat evaporates, it carries heat with it, cooling the body.

On a hot day the body can lose 7 liters of water per day.

A few degrees change in body temperature can radically alter body chemistry. Maintaining body temp. is very important to homeostasis.


Apocrine sweat glands are confined to the axillary and genital areas

Larger than eccrine glandsDucts empty into hair folliclesSecretions contain fatty acids, proteins, as

well as all the other stuff secreted by the eccrine glands.

III. Appendages of the SkinIII. Appendages of the SkinThe secretions can have a milky or

yellowish color.Odorless until bacterial that live on the skin

use the proteins and fats as nutrients. Then it produces a musky unpleasant odor.

Begin to function during puberty.A lot is unknown about these. They have

almost no thermoregulatory function.Become more active during stress or sexual

foreplay.


There are millions of hairs scatterd all over the body.

Only a few serve an important functionHair on head to protect brain from bumps.Eyelashes shielding the eyesNose hairs keep particles from the

respiratory tract.


Hairs original purpose was to keep the body warm.

Hair is produced by a hair follicleRoot hair is enclosed in the follicle.The hair shaft extends out of the follicle.Hair is formed by a division of the stratum

basale called hair bulb matrix.


KNOW THE DIAGRAM OF A HAIR ON PAGE 100

Arrector pili muscles are part of the hair follicle that make the hair stand up and makes “goose bumps”


Nails are scalelike modifications of the epidermis that corresponds to the hoof or claw of other animals.

Each nail has a free edge, a body (visible portion), and a root (embedded in the skin)

Each nail has overlapping edges called nail folds.

Proximal nail fold is called the cuticle.


Stratum basale of the epidermis extends beneath the nail as the nail bed.

Nail matrix is responsible for nail growth. The white cresent is called the lunula. Nail is normally clear. Pink color is due to blood

supply to the stratum basale. When blood supply is low, nail becomes cyanotic. KNOW THE DIAGRAM ON PAGE 102.

IV. HomeostasisIV. HomeostasisThe skin has more than 1000 different

ailments.Athlete’s foot – itchy, red, peeling

condition of the skin between the toes resulting from a fungal infection; tinea pedis

Boils and carbuncles – inflamation of the hair follicles and sebaceous glands, common on the dorsal neck. Carbuncles are caused by bacterial infection (usually Staphlococcus aureus)

IV. HomeostatisIV. Homeostatis

Cold Sores – fever blisters – small fluid-filled blisters that itch and sting, caused by a herpes simplex infection. Localized in a cutaneous nerve, where it remains inactive until emotional upset – usually around the lips and oral mucosa

Contact dermatitis – itching, redness, and swelling of the skin, progressing to blistering. Exposure of the skin to chemicals the provokes an allergic response.

IV. HomeostatisIV. HomeostatisImpetigo – pink, water-filled, raised lesions

of the mouth and nose that develops a yellow crust and eventually rupture. Very contagious – common in elementary school children.

Psoriasis – chronic condition, characterized by reddened epidermal lesions, covered with dry, silvery scales. Can be disfiguring. Cause is unknown .

ch. 4 skin and body membranes

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