Chapter 4 Skin and Body Membranes
Classification of Body Membranes
Be Able To
•List the general functions of each
membrane type and location in the body.
•Compare the structure of the major membrane types.
Key Terms : body membranes, epithelial membranes, cutaneous membrane, mucous membrane, serous membrane, serous fluid, peritoneum, pleura, pericardium, and synovial
membrane.
Classification of Body Membranes
• Body membranes cover surfaces, line body cavities, and form protective sheets.
• Tissue makeup
differentiates the two major categories of body
membranes: epithelial membranes and
connective tissue membranes.
• Epithelial membranes
contain a sheet of epithelial tissue and an underlying layer of connective tissue.
• Connective tissue
membranes contain no
epithelial cells.
Epithelial Membranes: Cutaneous
Membranes
• The cutaneous
membrane, or skin, is composed of two distinct regions: the superficial epidermis and the
underlying dermis.
• The epidermis is
composed of epithelial cells and the dermis is a tough leathery layer
composed of dense
fibrous connective tissue.
• Only the dermis is
vascularized.
Epithelial Membranes:
Mucous Membranes
• Mucosa or mucous
membranes line body cavities that are open to the exterior regions of the body, e.g.
digestive or urinary tract.
• They are wet or moist membranes bathed by
secretions, e.g. mucus or urine.
• Most mucous membranes
contain either stratified or simple columnar epithelia.
• All mucous membranes consist of an epithelial sheet under a layer of loose connective tissue called the lamina propria.
• In some cases a third layer of smooth muscle cells exist under the lamina propria.
Epithelial Membranes:
Serous Membranes
• Serous membranes or serosae are moist membranes located in closed ventral body cavities.
• Each serosa consists of a layer of simple squamous epithelium that rests on a thin layer of aerolar connective tissue.
• Serous membranes occur in pairs:
the parietal layer (lines the cavity and the visceral layer (lines the organs).
• Serous fluid lubricates the surfaces of the layers to reduce friction and prevents the organs from sticking to the walls of the cavity.
• The serosae are named by their location: the peritoneum lines the abdominal cavity, the pleura lines the thoracic wall, the pericardium covers the heart.
Connective Tissue Membranes:
Synovial Membranes
• Synovial membranes are composed of soft areolar connective.
• Synovial membranes line the fibrous capsules surrounding synovial joints in the knee, shoulder, or hip.
• They provide a smooth surface and secrete lubricating fluid.
• Synovial membranes also line bursae and tendon sheaths.
• These structures cushion
organs that move against each other during muscular
contraction.
Chapter 4 Skin and Body Membranes
Integumentary System
Be Able To
•List several important functions of the integumentary system.
•Identify the epidermis, dermis, hair and follicles, sebaceous gland, and sweat gland on diagrams.
•Name the layers of the epidermis and dermis and describe the characteristics of each.
•Name the factors that determine skin color and describe the function of melanin.
Key Terms
: integumentary system, integument, epidermis, keratinizing, dermis, hypodermis, keratinocytes, stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum, melanin, melanocytes, papillary layer, dermal papillae, and reticular layer.Integumentary System
Basic Skin Functions
• The integumentary system is comprised of skin and its
associated organs.
• It has a surface area of 1.5 to 2 m2.
• It weighs 4 to 5 kg.
• It accounts for 7% of total body weight.
• Every cm2 has 100 sweat glands, 15 oil glands, 230 sensory
receptors, and a half a million cells that are constantly replaced.
• The integument functions to:
protect, insulate, cushion, regulate body temperature, excrete, and synthesize vitamin D.
• Tiny sensors in the skin collect information from our environment.
Why don’t people become waterlogged after swimming?
Integumentary System
Structure of the Skin
• The skin varies in thickness from 1.5 to 4 mm.
• The integument is comprised of two distinct regions: epidermis and
dermis.
• The epidermis or outer layer of skin is composed of stratified squamous epithelium that is hard and tough.
• The well vascularized dermis is the bulk of the integument and is made of dense fibrous connective tissue that lies beneath the epidermis.
• Subcutaneous tissue or
hypodermis is deep to the dermis.
• The hypodermis composed primarily of areolar and adipose tissue and anchors the skin to underlying
organs, insulates, and absorbs shock.
Where does the hypodermis thicken in men and women?
Scalp
Integumentary System
Epidermal Cells
• The epidermis is a thick keratinized stratified squamous epithelium
consisting of four distinct cell types and five distinct layers.
• The most abundant cells in the
epidermis are the keratin producing keratinocytes.
• Keratinocytes migrate to the surface of the skin where they form dead
scale-like structures.
• The melanin (pigment) producing cells are melanocytes.
• Melanin protects the DNA from UV light on the sunny side of keratinocytes.
• Langerhans’ cells are macrophages that travel from bone marrow to the epidermis.
• Merkel cells associate with sensory nerves to function in touch.
A new epidermis is produced every 25 to 45 days.
Integumentary System
Epidermal Strata (layers)
• The stratum basale is the deepest epidermal layer composed of a single row of rapidly mitotic keratinocytes along with a small amount of
melanocytes.
• The stratum spinosum is several cell layers thick and appears as a weblike system of keratin filaments.
• Melanin granules and Langerhans’ cells are most abundant in this layer.
• The stratum granulosum is three to five cell layers thick.
• Kertatinocytes drastically flatten in this layer and accumulate a glycolipid that waterproofs the flattened cells.
• The stratum lucidum is composed of 3 to 5 layers of clear, flattened, dead
keratinocytes. (present in only thick skin).
• The superficial outer stratum corneum is 20 to 30 cell layers thick and forms the overcoat of the body.
Why don’t men and women bleed profusely during shaving?
Integumentary System
Dermis
• The dermis is composed of two main layers:
papillary and reticlular layers.
• The superficial papillary layer has fingerlike projections called dermal papillae that
house capillaries, pain receptors, and touch receptors (meissner’s corpuscles).
• dermal papillae form genetically determined looped and whorled ridges that along with associated sweat glands form fingerprints.
• the deeper reticular layer accounts for 80%
of the dermis and contains blood vessels, sweat and oil glands, and deep pressure receptors called pacinian corpuscles.
• its extracellular matrix contains thick
bundles of collagen fibers that run parallel to the skin surface.
• collagen not only provides strength to the skin, it also binds water to the skin.
• stretch marks are scars created by extreme stretching of the skin, as in pregnancy.
• A blister is a separation between the epidermis and dermis.
How do blisters form?
Integumentary System
Skin Color
• Three pigments contribute to skin color:melanin, carotene, and hemoglobin.
• Melanin ranges in color from yellow to reddish-brown to black.
• Racial color differences reflect the relative kind and amount of melanin made.
• Carotene is a yellow to orange pigment found in certain plants and tends to
accumulate in the stratum corneum and the hypodermis.
• Hemoglobin creates a pinkish hue in light-skinned people.
• When blood is poorly oxygenated,
light-skin appears blue, a condition called cyanosis.
• Skin color is often influenced by emotional stimuli and certain disease states:
❖ erythema, pallor, jaundice, or bruising.
Erythema multiforme is the name given to a
short-lasting illness
Chapter 4 Skin and Body Membranes
Appendages of the Skin
Be Able To
•Describe the distribution and function of the sebaceous glands, sweat glands, and hair.
Key Terms : skin appendages, exocrine glands,
sebaceous glands, sebum, sweat glands or sudoriferous
glands, eccrine glands, sweat, pore, apocrine sweat glands,
hairs, root, shaft, hair bulb matrix, hair follicles, arrector pili,
and nail.
Appendages of the Integumentary System
Sudoriferous Glands
• Sweat glands are distributed over the entire skin surface, more than 2.5 million per person.
• Eccrine sweat glands are abundant on the palms, soles of feet, and forehead.
• Sweat is hypotonic and its contents depend on both genetics and diet.
• Appocrine sweat glands are found in the armpit and genital area.
• Appocrine sweat is primarily water with some fatty substance and proteins that when decompose by bacteria cause body odor.
• Ceruminous glands are modified
apocrine glands found in the lining of the external ear canal that secrete cerumen or ear wax.
• Mammary glands secrete milk.
Why is the low pH (4 to 6)of sweat important?
secretory ducts
epithelium
Appendages of the Integumentary System
Sebaceous Glands
• Oil glands all found all over the body except on the palms and soles of the feet.
• Sebum is an oily substance secreted into a hair follicle or onto the skin
surface.
• Sebum softens and lubricates the hair and skin, prevents against brittle hair, and slows water loss.
• Sebum secretions are stimulated by hormones, especially androgens.
• Acne is an active inflammation of the sebaceous glands usually caused by bacteria, such as staphlyococcus.
Why does skin become more oily during puberty?
Appendages of the Integumentary System
Hairs
• Hairs or pili are flexible strands produced by hair follicles.
• The keratin of hair is stronger and more durable than
epidermal keratin.
• The root is the part enclosed in the follicle and the shaft projects from the follicle.
• Hair has three layers of keratinized cells: central
medulla, middle cortex, and the outer cuticle.
• The cuticle provides strength, but when the tip wears spilt ends are created.
Did you know that the main purpose of human body hair is to sense stinging insects?
Appendages of the Integumentary System
Hair Follicles
• Hair follicles extend from the
epidermal surface into the dermis.
• Sensory nerve endings wrap around the hair bulb.
• Capillaries protrude into the hair bulb.
• The wall of the hair follicle or
connective tissue root sheath is
created from the dermis and the inner epithelial root sheath from the
epidermis.
• The growth zone or hair matrix is an actively dividing area of the hair bulb.
• Arrector pili are bundles of smooth muscle tissue that when contracted raise hair follicles upright causing goose bumps.
What purpose does “hair raising” serve in our pets?
Appendages of the Integumentary System
Hair Distribution and Thinning
• Fine pale vellus hair is the body hair of children and adult females.
• Coarser, longer, and darker terminal hair comprises the eyebrows and scalp; armpit and genital areas; face, chest, arm, and legs of males.
• Nutrition and hormones influence hair growth and density.
• Hair grows fastest from teen years to the 40s.
• Hair thinning and baldness or alopecia is much less dramatic in women.
• Male pattern baldness is a sex-linked genetic trait that is caused by a gene that changes the way hair follicles respond to testosterone later in life.
There are over 100,000 hairs in the scalp and 30,000 hairs in a man’s beard.
Appendages of the Integumentary System
Nails
• A nail is a scale-like modification of the epidermis that forms a clear protective covering on the dorsal surface of the distal part of the finger or toe.
• Nails contain hard keratin.
• Each nail has a free edge, a body, and a proximal root.
• The deeper layers of the epidermis
extend beneath the nail as the nail bed.
• The nail matrix is the thick proximal
portion of the nail bed and is responsible for nail growth.
• Nails are transparent and colorless, however, their rich blood supply makes them appear pink.
• The white crescent area over the nail matrix is the lunula.
• Skin folds overlap the proximal or cuticle and lateral edges of the nail or
eponychium.
Nails are useful tools and perfect for scratching an itch.
Chapter 4 Skin and Body Membranes
Homeostatic Imbalances of the Skin
Be Able To
•Differentiate between first, second, and third degree burns.
•Explain the importance of the “nines”.
•Summarize the characteristics of basal cell carcinoma, squamous cell carcinoma, and malignant melanoma.
Key Terms : athlete’s foot, carbuncles, cold sores,
dermatitis, impetigo, psoriasis, burn, carcinoma, and
melanoma.
Imbalances of the Integumentary System Infections and Allergies
• The skin can develop more than a 1,000 different ailments!
• Athlete’s foot is caused by a fungal infection.
• carbuncles are boils caused by a bacterial infection of hair follicles and sebaceous glands.
• Cold sores are small fluid-filled blisters caused by viral infection.
• Allergic response to chemicals causes dermatitis, which is a red itchy
swelling of the skin.
• Impetigo is a pink, water filled lesion around the mouth or nose caused by a staphylococcus infection.
• Psoriasis is a chronic red lesion
covered with dry silvery scales.
When athlete’s foot spreads to the soles and toe nails it is called tinea pedis.
Psoriasis is not contagious
Homeostatic Imbalances of the Skin Burns
• A burn is tissue damage inflicted by intense heat, electricity, radiation, or
chemicals, which denature cell proteins and cause cell death in the affected regions.
• Immediate life-threatening effect is loss of body fluids
which can lead to renal failure and circulatory shock.
• Fluid volume loss can be
estimated by computing % of body surface burned using
“rules of nines”.
• Why do burn patients need thousands of extra calories?
• After 24 hours the burned area is very susceptible to infection.
Over 2 million Americans are treated for burns and 12,000 of them die each year.
Homeostatic Imbalances of the Skin Burns
• Burns are classified by their severity.
• First degree burns damage the epidermis only and heal in 2-3 days;
symptoms include localized redness, swelling, and pain, e.g. sunburn
• Second degree burns injure the
epidermis and upper dermis and heal in 3-4 weeks; similar symptoms as with first degree burn along with blistering.
• Third to degree burns injure entire skin region and often require skin grafting to prevent future fluid loss;
symptoms include nerve damage, various colors, and fluid loss.
• Skin grafting includes the removal of the burned skin, application of a
synthetic or organic skin followed by natural regeneration of skin and the degradation of foreign skin.
Critical burns have: (1) greater than 25% body with 2nd degree burns, (2) over 10% with 3rd degree burns, (3) 3rd degree burns of face, hands, feet.
Before skin graft
1 year after skin graft
Homeostatic Imbalances of the Skin Skin Cancer
• Most skin tumors are benign and do not metastasize (spread).
• Malignant or cancerous skin tumors are often caused by overexposure to UV radiation.
• Basal cell carcinoma is the least malignant and most common skin cancer; surgical
excision is used in 90% of the cases.
• Squamous cell carcinoma lesions arise often on scalp, ears, dorsal portion of the hand, and lower lip; surgical excision and radiation treatment may cure if tumor is caught early.
• Malignant melanoma is the most dangerous skin cancer that develops from pigmented moles; 50% chance of being cured if caught early with surgical excision and
immunotherapy.
• American Cancer Society suggests
frequent spot checks of moles or pigmented spots with the ABCD rule.
At age 17 years, a teen-ager has
significant sun damage due to
deliberate tanning on the beach or in
tanning salons