• Body membranes– Cover body surfaces– Line body cavities– Form protective sheets around

organs

• Two types of body membranes:

• Epithelial membranes

• Connective tissue membranes

Classification of Body Membranes

• Epithelial membranes:

– cover and lines the internal or external cavities

– Composed of epithelial cells attaching to

• underling tissue with the help of connective tissue layer

– E.g. • Cutaneous membrane• Mucous membrane• Serous membrane

• Cutaneous membrane : skin• Dry membrane• Outermost protective boundary• Superficial epidermis is

composed of – Keratinized stratified

squamous epithelium• Underlying dermis is build from

– dense connective tissue

Epithelial membrane

• Mucous Membranes:• Surface epithelium attached to

the underlying tissue with loose connective tissue

• Lines all body cavities that open to the exterior body surface such as digestive, respiratory, urinary, reproductive tracts

• absorption and secretion

Epithelial membrane

• Serous Membranes:• Surface is a layer of simple

squamous epithelium

• Underlying layer is a thin layer of areolar connective tissue

• Lines open body cavities that are closed to the exterior of the body

• Serous membranes occur in pairs separated by serous fluid

– Visceral layer covers the outside of the organ

– Parietal layer lines a portion of the wall of ventral body cavity

Epithelial membrane

• Specific serous membranes– Peritoneum

• Abdominal cavity

– Pleura• Around the lungs

– Pericardium• Around the heart

Classification of Body Membranes

• Connective tissue membranes:

• Synovial Membranes– composed of areolar

connective tissue layer

– contains no epithelial cells

– Lines fibrous capsules surrounding joints

– Secretes a lubricating fluid to prevent friction

• Consists of skin and accessory structures

• Such as hair, nails, and glands

• Covers the outside of the body

• Forms the boundary between body and external environment

• Protects the body from the outside world

• Protection : Skin protects against abrasion, UV light, reduce water loss, prevent microorganism entry

• Sensation: Has sensory receptors, detect heat, cold, touch, pressure, pain

• Temperature regulation: By control of blood flow through skin, sweat glands

• Vitamin D production: Skin produce Vitamin D – UV light

• Excretion: Excrete through skin

• Covers the entire outer surface of the body • Consists of two layers:• Epidermis• Dermis• Epidermis: Superficial layer of epithelial tissue

– Resists abrasion– Reduces water loss

• Dermis: Deep layer of connective tissue

– Structural strength

• Hypodermis:– Loose connective tissue that connects skin to underlying structures (muscle or bone)– Not part of skin

Skin Structure• Epidermis – outer layer

– Stratified squamous epithelium

– Often keratinized (hardened by keratin)

– Prevents loss of water– Avascular

• Epidermis – 5 layers

• stratum basale: bottom most single layer attached to the dermis– Undergoes mitotic cell division

and replaces top layers as they move up

– Receive nourishment from the underlying dermis that contains capillaries

• Stratum Spinosum• Stratum granulosum

• Epidermis – 5 layers

• Stratum lucidum– Formed from dead cells of the

deeper strata– Occurs only in thick, hairless

skin of the palms of hands and soles of feet

• • stratum corneum

– Top layer exposed to sun is Rich in keratin protein

– Constantly replaced as they get damaged

– Several layers that are Dead cells

Skin Structure• Keratinocytes: Secrete protein

called – keratin that gives toughness to

skin

• Melanocytes : produce melanin

– Found in stratum basale – gives skin different shades of color

• Amount of melanin produced depends upon – genetics and exposure to sunlight

• Melanin is produced in response to – UV light to protect the DNA – Prevent skin cancer

Skin Color• Three pigments contribute to skin color:

• Melanin– Amount and kind of melanin in epidermis

– Yellow, brown or black pigments

• Carotene– Orange-yellow pigment from some vegetables

• Hemoglobin– Red coloring from blood cells in dermis capillaries

– Oxygen content determines the extent of red coloring

• Dermis– Dense connective tissue made of

collagen and elastin fibers

– Decreases with aging leading to wrinkles

– Collagen fibers give skin its toughness

– Elastic fibers give skin elasticity

– Maintains body temperature, – response to stimuli

– Consists of two layers• Papillary layer• Reticular layer

• Dermis

• upper papillary layer : contact with epidermis – Contains fingerlike projections,

called dermal papillae, extend towards epidermis

– In the palms, fingers, soles, and toes papillae forms friction ridges which improves the grip of hand and feet

– Supplied with receptors for various senses

– Unique to each individual

• Dermis

• Lower reticular layer in contact with underlying hypodermis– Carries the blood vessels, glands, nerves,

pressure receptors, phagocytes

• Deep to skin• Not part of skin• Consists of loose connective tissue

with collagen and elastic fibers• Main types of cells in hypodermis

are:– Fibroblasts– Adipose cells– Macrophages

• Hypodermis is also called– Subcutaneous tissue

• Contains about one-half of body’s fat. Functions as– Energy source– Insulation– Padding

Appendages of the Skin

• Skin appendages consists of:

• Cutaneous glands : Are exocrine glands– Sebaceous glands – Sweat glands

• Hair and Hair follicles

• Nails

• Sebaceous glands– Found all over the body except palms

and soles of the feet– They produce oily substance also

known as sebum

• It contains oil and fragmented cells• Lubricant for skin and

protects the skin from dryness• Kills bacteria

– Most have ducts that empty into hair follicles

– Glands are activated at puberty

• Skin during puberty is oily – Acne : overactive sebaceous

glands leading to pimples

• Sweat glands : Widely distributed in skin. Two types

– Eccrine: Open via duct to pore on skin surface

• Found all over the body

• Produce salty sweat that prevents bacterial growth

• Regulate body temperature

– Apocrine: Ducts empty into hair follicles

• Found in axillary and genital areas

• Secretion has fatty acids and proteins in addition to sweat

• Begins working after puberty

• Gives unpleasant odor

Sweat and Its Function

• Composition– Mostly water– Some metabolic waste– Fatty acids and proteins (apocrine only)

• Function– Helps dissipate excess heat– Excretes waste products– Acidic nature inhibits bacteria growth

• Odor is from associated bacteria

– Consists of hard keratinized epithelial cells– Melanocytes provide pigment for hair color– Present all over the skin except: soles, palms, lips, nipples– Size and thickness varies depending on their location– Texture( soft or rough) varies depending on the amount of

keratin protein

HairHair

• Hair is produced by hair follicle

• Hair is divided into • Shaft• Root• Shaft- protrudes above skin

surface• Root- located below skin

surface• Root & shaft of hair are

composed of dead keratinized epithelial cells

• Each hair consists of 3 concentric layers:

– Central medulla

– Cortex surrounds medulla

– Cuticle on outside of cortex• Most heavily keratinized

• Hair follicle: Consists of

– Epithelial root sheath– Dermal root sheath

– Epithelial root sheath:– Composed of epithelial tissue– Forms the hair

– Dermal root sheath:– Composed of dermal connective

tissue– Dermal region supplies blood

vessels to epidermal portion

Associated Hair Structures• Arrector pilli

– Smooth muscle cells – connect each side of the

hair follicle– When this muscle is pulled,

makes the hair stand erect and gives raise to goose bumps

– Protects from loose of heat from the body

Nail is protecting covering of distal part of finger or toe

Tool for pick up small objects, scratching

Nail contains a hard keratin

Each nail has a– free edge– a body (visible portion)– proximal root (embedded in the

skin)

Nail Structures

– Free edge: sharp

– Body: visible and attached to underlying skin

– Root of nail: hidden beneath the skin and rich in stratum basale epithelial cells

– Responsible for nail growth

– Eponychium – proximal nail fold that projects onto the nail body

Skin Homeostatic Imbalances

• Infections– Athletes foot:

• Caused by fungal infection

– Boils and carbuncles• Inflammation of hair follicle

and sebaceous gland• Effects neck and back • Carbuncles result from

multiple boils• Caused by Staphylococcus

aureus bacterial infection

Skin Homeostatic Imbalances

• Infections– Cold sores

• Fluid filled blisters• Around lips and oral cavity• Caused by herpes simplex

virus

• Contact dermatitis• Itching, redness and

swelling leading to blisters• Exposures of chemicals

cause allergic reaction

– Impetigo• Water filled lesion • Caused by contagious

staphylococcus bacterial infection

– Psoriasis• Cause is unknown• Chronic condition due to

overproduction of skin cells leading to epidermal lesions and scaling

• Triggered by trauma, infection, stress

• Burns– Damage to the skin– Tissue damage and cell death

caused by heat, electricity, UV radiation, or chemicals

– Resulting in Dehydration: due to loss of fluids from the surface of the burned skin leading to

• Electrolyte imbalance : due to kidney function shut down

• Circulatory shock : due to low blood volume

Rule of Nines: used to determine extent of burns

• Body is divided into 11 areas for quick estimation– Each area represents

about 9%– In addition to 1% of

genital area

• Burned tissue easily get – bacterial and fungal

infections– Due to impaired

immune system

Severity of Burns

• First-degree burns– Only epidermis is

damaged– Skin is red and swollen– Heal with in few days with

no scars– E.g sun burn

• Second degree burns– Epidermis and upper

dermis are damaged– Skin is red with blisters– Regenerate with in few

weeks and scars are not present

Severity of Burns• Third-degree burns

– Destroys entire skin layer ( epidermis and dermis)

– Burn is gray-white or black

– Nerve ending are also destroyed

– Regeneration is not possible

– Skin grafting is essential

Critical Burns• Burns are considered critical if:

– Over 25% of body has second degree burns

– Over 10% of the body has third degree burns

– third degree burns of the face, hands, or feet

• Face: restricts movement of air through respiratory tract

• Hands and feet: joint tissue repair limits joint mobility

Skin Cancer• Cancer ( neoplasm or

tumors)– abnormal cell mass

• Two types– Benign

• Does not spread (encapsulated)

– Malignant• Metastasized (moves)

to other parts of the body

• Skin cancer is the most common type of cancer

Skin Cancer Types

• Basal cell carcinoma

– Least malignant

– Most common type

– Arises from stratum basale

– Spread into dermis

– Slow growing and does not undergo metastasis

– surgery

Skin Cancer Types

• Squamous cell carcinoma

– Arises from stratum spinosum

– Sun induced commonly seen in areas such as hands, lips, scalp, ears

– Develops into ulcers

– Metastasizes to lymph nodes

– Early removal allows a good chance of cure

– Surgery or radiation

Skin Cancer Types

• Malignant melanoma– Most deadly of skin cancers– Cancer of melanocytes– Appears as a black patch

that seems to be growing– Metastasizes rapidly to

lymph and blood vessels– Detection uses ABCD rule– Early detection helps in

increasing the chances of survival

ABCD Rule• A = Asymmetry

– Two sides of pigmented mole do not match

• B = Border irregularity– Borders of mole are not

smooth

• C = Color– Different colors in

pigmented area

• D = Diameter– Spot is larger then 6 mm

in diameter