CHAPTER 4

Skin and Body Membranes

Function of Body Membranes

Line or cover body surfaces Protect body surfaces Lubricate body surfaces

Classification of Body Membranes Epithelial Membranes – are simple

organs– Cutaneous membranes– Mucous membrane– Serous membrane

Connective Tissue Membranes

Cutaneous Membrane Cutaneous

Membrane = skin– A dry membrane

because it is exposed to air

– Outermost protective boundary

Superficial Epidermis– Keratinized stratified

squamous epithelium Underlying Dermis

– Mostly dense connective tissue

Mucous Membranes “Wet” or moist

membranes Surface Epithelium

– Type of epithelium depends on its location

Has a layer of underlying loose connective tissue called the lamina propria

Lines all body cavities that open to the exterior body surface– Respiratory, Digestive, and

Reproductive organs Adapted for absorption or

secretion

Serous Membranes Serous Membranes = “Serosa” Surface simple squamous epithelium

with underlying areolar connective tissue

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

Serous membranes occur in pairs:– Parietal = lines the cavity wall– Visceral = covers the outside of the organ

contained in the cavity

Serous Membranes

Serous layers are separated by serous fluid which helps to reduce friction between organs.

Specific Serous Membranes:– Peritoneum = covers the abdominal cavity– Pleura = surrounds the lungs– Pericardium = surrounds the heart

Connective Tissue Membrane

Synovial Membrane– Made of connective tissue only– Lines fibrous capsules surrounding joints

Synovial Membrane

Integumentary System

Components include:– Skin = cutaneous membrane– Sweat glands– Oil glands– Hairs– Nails

Integumentary System

Protects deeper tissues from:– Mechanical Damage– Chemical Damage– Bacterial Damage– Thermal Damage– UV Radiation– Drying Out

Integumentary System

The skin aids in:– Heat Regulation– Excretion of urea and uric acid– Synthesizing vitamin D

Skin Structure Has 3 layers:

– Epidermis = outermost layer• Stratified squamous epithelium• Often keratinized (hardened by keratin)

– Dermis = middle layer• Dense connective tissue• Firmly connected to epidermis

– Hypodermis = aka “subcutaneous” tissue; deep to the dermis

• Not part of the skin• Anchors skin to underlying organs• Composed mostly of adipose tissue

Skin Structure

Layers of the Epidermis Stratum Basale

– Layer lying next to the dermis and is undergoing mitosis

Stratum Spinosum Stratum Granulosum Stratum Lucidum

– Occurs only in thick skin Stratum Corneum

– 20 to 30 cell layers thick– Shingle-like dead cells– Have a totally “new” epidermis every 25-45 days

Melanin

Pigment produced by melanocytes Color is yellow to brown to black Found mostly in the stratum basale Amount produced depends upon

genetics and the exposure to sunlight

Layers of the Dermis

Papillary Layer– Have projections called dermal papillae– Contain pain receptors (Meissner’s

corpuscles) and capillary loops Reticular Layer

– Deepest skin layer– Contains blood vessels, glands, and

pressure receptors (Pacinian corpuscles)

Normal Skin Color Determinants

Melanin = yellow, brown, or black pigments

Carotene = orange-yellow pigment from some vegetables

Hemoglobin = red coloring from blood cells in the dermis capillaries; oxygen content determines the extent of red coloring

Accessory Organs of the Skin

Sebaceous Glands = produce oil– Acts as a lubricant for skin and kills

bacteria– Most have ducts that empty into hair

follicles– Glands are activated at puberty

Accessory Organs of the Skin Sweat Glands = widely distributed in

skin– 2 types:

• Eccrine = open via duct to pore on skin surface

• Apocrine = ducts empty into hair follicles– Composition of sweat:

• Mostly water, some metabolic waste• Only in apocrine glands – fatty acids &

proteins

– Function:• Helps get rid of excessive heat• Excretes waste products• Its acidic nature inhibits bacteria growth

– Odor is from associated bacteria

Accessory Organs of the Skin

Hair – produced by hair follicle– Consists of hard

keratinized epithelial cells

– Melanocytes provide pigment for hair color

Hair

– Has a central medulla, a cortex that surrounds it, and a heavily keratinized cuticle on the outside of the cortex

Hair

– Arrector Pili = muscle that contracts when we are cool to give the appearance of “goose bumps” because it is attached to the hair follicle

Accessory Organs of the Skin

Nails = scale-like modifications of the epidermis that are heavily keratinized– Have a lack of pigment that makes them

colorless– Stratum basale extends beneath the nail

bed so that the nail grows

Nails

Skin Homeostatic Imbalances

Infections (page 107):– Athlete’s Foot = caused by fungal infection– Boils & Carbuncles = caused by bacterial

infection– Cold Sores = caused by a virus– Contact Dermatitis = exposures cause an

allergic reaction– Impetigo = caused by bacterial infection– Psoriasis = cause is unknown but is

triggered by trauma, infection, and stress

Burns (pages 108 – 109) Tissue damage and cell death caused

by heat, electricity, UV radiation, or chemicals

Dangers of burns include dehydration, electrolyte imbalance, and circulatory shock

“Rule of Nines” is a way to determine the extent of burns– Body is divided into 11 areas for quick

estimation and each area represents about 9%

Severity of Burns 1st Degree Burns = only epidermis is

damaged– Skin is red and swollen

2nd Degree Burns = epidermis and upper dermis are damaged– Skin is red with blisters

3rd Degree Burns = destroys entire skin layer– Burn is gray-white or black

Burns

Burns are considered critical if:– Over 25% of the body has 2nd degree burns– Over 10% of the body has 3rd degree burns– There are 3rd degree burns of the face,

hands, or feet

Skin Cancer

Skin Cancer = most common type of cancer; abnormal cell mass; 2 types:– Benign – does not spread– Malignant – metastasized (moves) to other

parts of the body

Basal Cell Carcinoma

Least malignant Most common type arises from stratum

basale

Squamous Cell Carcinoma

Early removal allows a good chance of cure

Arises from stratum spinosum Metastasizes to lymph nodes

Malignant Melanoma

Most deadly of skin cancers Cancer of melanocytes Metastasizes rapidly to lymph and blood

vessels

Detection of Skin Cancer

Uses ABCD rule:– A = Asymmetry

• 2 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 than 6mm in diameter