Human Body
Chapter 4Skin and Body Membranes
Classification of Body Membranes
Membranes cover surfaces, line body cavities, and forms protective sheets around organs
Two Major Groups
Epithelial Tissue Membranes- include cutaneous, mucous, and serous membranesConnective Tissue Membranes- include synovial membranes
Epithelial Membranes
These membranes contain and epithelial sheet with an underlying layer of connective tissue.These membranes are actually simple organs.
Cutaneous Membranes
This is your skin!The upper layer is keratinizing stratified squamous epithelium.The lower layer is dense fibrous connective tissue.The membrane is exposed to air and is a dry membrane
Cutaneous Membrane
Mucous Membranes
Composed of various types of epithelium resting on loose connective tissue calledlamina propria.This membrane type lines all body cavities that open to the exterior, such as those hollow organs of the respiratory, digestive, urinary, and reproductive tract.
Mucous Membranes
Wet, moist that are almost continuously bathed in secretions or in the case of urine mucosae, urine.Function: absorption and secretion with the exception of mucosae of the respiratory and digestive system that secretes large amounts of protective, lubricating mucus.
Mucous Membranes
Serous Membranes
Composed of simple squamous epithelium resting on a thin layer of areolar connective tissue.Lines cavities that are closed to the exterior.Occur in pairs:Parietal Layer-lines a specific portion of the ventral cavityVisceral Layer- covers the outside of the organs
Serous Membranes
The layers are separated by a thin layer of fluid called serous fluid.The serous fluid allows the organs to slide against each other and the walls without friction.The name of specific serous membranes depends in location
Serous membranes
Peritoneum:Pleura:Pericardium:
Connective Tissue Membranes
Synovial MembranesComposed of connective tissue and no epithelial tissueLine the fibrous capsules surrounding jointsProvide a smooth surface and secrete a lubricating fluidLine small sacs of connective tissue called bursae and the tube-like tendon sheathsCushion organs moving against each other
Integumentary System (Skin)
Cutaneous membraneSkin, Sweat Glands, Oil Glands, Hair, and NailsFunction is mostly protective
Basic Skin Functions
Protects:entire body from mechanical damage (bumps and cuts)chemical damage (acids and bases)Thermal damage (hot and cold)Ultraviolet radiationBacteria** also insulates and cushions deeper body organs**
Basic Skin Functions
Outer layer is hardened to prevent water loss.Capillaries and Sweat Glands regulate heat loss.Mini excretory system ( urea, salts, and H20)Manufactures several proteins for immunity and Vitamin D synthesis.Sensory Receptors ( pain, pressure, temperature, and touch)
Structure of the Skin
Composed of two kinds of tissue:The Epidermis- composed of stratified squamous epithelium that is capable of keratinizing.The Dermis- made up of dense connective tissue**The epidermis and dermis are firmly connected****A burn or friction can cause them to separate causing a blister**
Structure of the Skin
Hypodermis:located deep to the dermisEssentially Adipose TissueAnchors the skin to underlying organsShock absorber and insulatorResponsible for curves (female)
Epidermis
Composed of 5 zones or layers called strataStratum BasaleSpinosumGranulosumLucidumCorneum**Epidermis is avascular****most cells are keratinocytes**
Melanin
A pigment that ranges from yellow to brown to black-produced by melanocytesFound in stratum basaleWhen skin is exposed to sunlight it stimulates the melanocytes to produce more melanin pigment=tanning.Freckles and moles are melanin concentrated in one spot.
Melanin
Excessive UV exposure can damage the skinElastic fibers clump causing leathery skin.Depresses the immune systemCan alter the DNA of skin cells leading to skin cancerMelanin can act like a natural sunscreen
Dermis
“Hide” strong, stretchy, envelope that helps hold the body together.Two major regions:Papillary RegionReticular Region
Skin Color
Three pigments contribute to skin color:The amount and kindThe amount of carotene deposited in the stratum corneum and subcutaneous layerThe amount of O2 bound to the hemoglobin in the dermal blood vessel
Skin Color
Carotene- orange-yellow pigment found in abundant amounts in carrotsPeople who produce a lot of melanin have darker colored skinCrimson color of O2-rich hemoglobin flushes through the transparent layer to give rosy color
Skin Color
Skin takes on a yellow-orange cast when large amounts of carotene are eatenCyanosis-turning blue from a lack of O2In black people skin does not appear cyanotic-masked by melanin-nail beds and mucous membranes
Skin Color
Redness or ErythemaEmbarrassment, fever, hypertension, inflammation or allergy
Skin Color
Pallor or BlanchingEmotional stress, anemia, low blood pressure, impaired blood flow to an area
Skin Color
Jaundice or Yellow CastLiver disorder-excess bile pigments are absorbed in the blood, circulated through the body and deposited in body tissues
Skin Color
Bruises or Black and Blue MarksReveal sites where blood has escaped circulation and has clotted in tissue spacesHematomasVitamin C deficiency or Hemophilia
Appendages of the Skin
Arise from the epidermisPlay a role in maintaining homeostasisInclude Cutaneous glands, Hairs, Hair follicles, and Nails
Cutaneous Glands
Exocrine glands that release their secretions to the skin surface via ducts.Two Types1. Sebaceous Glands2. Sweat Glands* Located in the dermis, deep tissue layer
Sebaceous Gland
Oil GlandsFound all over the skin except the palms of hands and soles of feet.The ducts usually deposit into the hair follicle but some will empty on the surface of the skinSebum(grease)-mixture of oily substances and fragmented cells
Sebaceous Glands
Sebum:Keeps skin soft and moistPrevents hair from becoming too brittleContains chemicals that kill bacteria, prevents the bacteria on skin from invading deeper tissue layersBecome very active when make sex hormones are produced(adolescence)
Sebaceous Glands
If gland’s duct gets blocked by sebum “whitehead” occurs. If material oxidizes, it forms a “blackhead”Acne=active infection of the sebaceous gland.Seborrhea=cradle cap in infants is caused by over activity of the sebaceous glands
Sweat Glands
Also called Sudoriferous GlandsWidely distributed throughout the skin2.5 million per personTwo types: eccrine and apocrine
Eccrine Glands
Numerous and found all over the bodyProduce Sweat(clear mostly H2O, salts, vitamin C, trace amounts of metabolic wastes, lactic acid)Sweat is acidic-prevents bacteria growthSweat reaches skin’s surface through pores.
Eccrine Glands
Highly efficient part of body’s heat regulating equipment.Supplied with nerve endings that are sensitive to external temps.Hot day possible to lose up to 7 liters of body H2O
Apocrine Sweat Glands
Confined to axillary and genital areasLarger than eccrine glands and their ducts empty into hair follicles.Secretions contain fatty acids and proteins as well as those secreted by the eccrine glandsSecretions take on a milky or yellowish color.Bacteria that live on the skin will use the proteins and fatty acids causing smell.
Apocrine Glands
Begin to function around puberty under the influence of androgens.Minimal role in thermoregulation.Activated by nerve fibers during pain, stress, and sexual foreplay
Hairs and Hair Follicles
Millions of hairs scattered all over the body.Serve several functions: guarding head against bumps, shielding the eyes, preventing foreign particles from getting into the respiratory tract.Lost ancient function
Hair
See pictures on pg. 100Come in a variety of sizes and shapesThe shape of the hair shaft will determine the look of the hairArrector pili muscle
Nails
Scale-like modification of the epidermis that corresponds to the hoof or claw in other animalsConsists of: Free edge, body, root, nail folds, nail bed, nail matrixTransparent or nearly colorless but look pink because of the oxygen rich blood supply under the dermis.
Homeostatic Imbalances of the Skin
Loss of homeostasis in the body cells and organs can reveal itself in the skinThe skin can develop more than 1000 different types of aliments.The most common types of skin disorders result from allergies, bacterial, viral, or fungal infections.
Infections and Allergies
Athlete’s Foot-Itchy, red, peeling condition between the toes of the feet. Fungal infection
Infections and Allergies
Boils and Carbuncles- Inflammation of the hair follicles and sebaceous glands, common on dorsal neckCarbuncles are composite boils caused by Staphylococcus Aureus- Staph Infection
Infections and Allergies
Cold Sores- small fluid filled blisters that sting and itch.Caused by Herpes Simplex InfectionVirus localizes in cutaneous nerve where it will remain dormant until emotional upset, fever, UV radiation
Infections and allergies
Contact Dermatitis- Itching, redness, swelling of the skin, progressing to blisteringCaused by exposure to chemicals that provoke allergic reactions (poison ivy)
Infections and Allergies
Impetigo-pink, water-filled raised lesions that develop a yellow crust and eventually ruptureHighly contagious staphylococcus infectionCommon in elementary school children
Infections and Allergies
Psoriasis- Chronic condition characterized by reddened epidermal lesions covered by dry, silvery scales.Severe cases can be disfiguringCause is unknown-hereditary, triggered by trauma, infection, hormonal changes, and stress
Burns
Skin is about as thick as a sheet of paper towelWhen severely damaged it affects all other systems in the body.Burn=tissue damage and cell death caused by intense heat, electricity, UV radiation, or certain chemicals
Burns
There are few threats to skin more serious then burns.Two life threatening events:Body loses precious supply of fluids containing proteins and electrolytes as they seep from burned surfaces.Dehydration and electrolyte imbalance follow leading to kidney failure and circulatory shock
Burns
In order to save a patient the lost fluids must be replaced.Apply the Rule of Nines:Divides body into 11 areas each accounting for 9% of the total body surface plus additional area surrounding the genitals representing 1% of body surface
Burns
Later infection becomes most important threat and is leading cause of death.Burned skin is sterile for 24hrs after that pathogens like bacteria and fungi invade area.Immune system becomes depressed within one to two days.
Burns
Burns are classified according to their severity.First Degree- epidermis is damaged, area becomes red and swollen, not serious and heal in two to three days. (sunburn)Second Degree- Injury to the epidermis and upper dermis, skin is red and painful, blisters appear, regeneration can occur, ordinarily no permanent scars result* referred to as Partial-Thickness Burns
Burns
Third- Degree Burns-destroys the entire thickness of the skin=full thickness burnsBurned area appears blanched or blackened, nerve endings are destroyed so it is not painful, regeneration is not possible.
Critical Burns
Burns are considered critical when:Over 25% of the body has 2nddegree burnsOver 10% of the body has 3rddegree burns3rddegree burns on the face, hands, or feet
Skin Cancer
Skin cancer is the single most common type of cancer in humansMost important risk factor is over-exposure to UV radiation in sunlightFrequent irritation of the skin by infections, chemicals, or physical traumas also seem to be predisposing factors
Skin Cancer
http://video.about.com/dermatology/Skin-Cancer.htm
Skin Cancer
Basal Cell CarcinomaLeast malignant and most commonCells are altered so that they can not form keratin no longer honor the boundary between epidermis and dermis.Occur on sun exposed areasFull cure is the rule 99%percent of cases where lesion is removed surgically.
Skin Cancer
Squamous Cell CarcinomaAppears as a scaly, reddened elevation that gradually forms a shallow ulcer with a firm raised border.Scalp, ears, hands, and lower lipGrows rapidly and metastasizes to adjacent lymph nodes if not removedSun-induced cure is good when removed surgically or by radiation therapy
Skin Cancer
Malignant MelanomaCancer of melanocytes5% of skin cancer but incidence is rising and is often deadlyCan begin wherever there is pigment-appears as a spreading brown to black patch that metastasizes quickly to surrounding lymph and blood vesselsSurvival=50% early detection is important
Skin Cancer
Sun worshippers should examine skin for new moles or pigmented spots and apply ABCD rule.A=Symmetry-two sides of the pigmented spot or mole do not matchB=Border Irregularity-the borders of the lesion are not smooth but exhibit indentations
Skin Cancer
C=Color-the pigmented spot contains areas of different colors (blacks, browns, tans, and sometimes blues and redsD=Diameter-the spot is larger than 6mm in diameter (the size of a pencil eraser)
Developmental Aspects of Skin and Body Membranes
During the 5thand 6thmonths of fetal development the fetus is covered in LanugoVernix Caseosa- white, cheesy-looking substance produced by the sebaceous glands. Protects the babies skin while it is in the amniotic fluidMilia-white spots that appear on the baby’s nose and forehead
Development cont.
During adolescence skin and hair become more oilySkin reaches its peak in our 20s and 30s then changes occur as it is assaulted by abrasion, chemicals, wind, sun and other irritants and as pores become blocked with air pollutants and bacteria
Development cont.
During old age subcutaneous tissue decreases leading to an intolerance to coldSkin gets drier can become itchy and bothersomeThinning of the skin cause bruisingDecreasing elasticity causes sagging skin-sped up by sunlight
Development cont.
Hair-loses luster as we age# of hair follicles reduced by 1/3 by 50 and continues to declineGraying hair results from a decrease or absence of the melanin deposited in the hair.
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