Transcript Skin and Body Membranes

Membranes and the Integumentary
System
Chapter 3
Body membranes
 Cover surfaces
 Line body cavities
 Form protective sheets around organs
 Two major groups (classified by tissue makeup)
 Epithelial membranes
 Connective tissue membranes
Epithelial membranes
 Include:
 Cutaneous membrane (skin)
 Mucous membranes
 Serous membranes
 All include a layer of epithelium but it is connected to a layer of
connective tissue
 These are actually organs!
Cutaneous membrane
 Skin
 Superficial epidermis
 Made of keratinizing stratified squamous epithelium
 Exposed to air
 A dry membrane
 (more info to come later)
Mucous Membranes
 Called mucosa
 Epithelium resting on loose connective tissue membrane
(lamina propria)
 Lines all body cavities that open to the exterior (respiratory,
digestive, urinary, reproductive)
 Most contain stratified squamous or simple columnar
epithelial cells
 These are “wet” membranes continuously bathed in secretions
Serous membranes
 Called serosa
 Simple squamous epithelium resting on areolar connective tissue
 Line body cavities closed to the exterior (except the dorsal body
cavity and joint cavities)
 Occur in pairs
 Parietal layer lines a part of the ventral body cavity
 Visceral layer covers the outside of the organs in the cavity
 Layers are separated by serous fluid (that prevents friction)
 Named for their locations
 Peritoneum – lines the abdominal cavity
 Pleura – surrounds the lungs
 Pericardium – surrounds the heart
Connective tissue membranes
 Called synovial membranes
 Soft areolar connective tissue and have NO epithelial cells
 Line fibrous capsules around joints
 Provide a smooth surface and secrete lubricating fluid
 Line the bursae and tendon sheaths
 Cushion organs moving against each other during muscle
activity
Integumentary system
 Made of sweat and oil glands, hairs, nails, skin
 Mostly a protective organ
Skin functions
 Controls homeostasis (in part) because it keeps things inside







the body but also keeps things outside the body
Insulation and cushioning for deeper organs
Protects body from mechanical, chemical, and thermal
damage, UV radiation, and bacteria
Upper layer is full of keratin to prevent water loss
Rich capillary network and sweat glands control temperature
Excretes urea, salts, and water in perspiration
Manufactures vitamins (Vitamin D)
Cutaneous sensory receptors help detect touch, pressure,
pain, and temperature
Structure of skin
 Two kinds of tissue
 Epidermis – stratified squamous epithelium can keratinize or
become tough
 Dermis – dense connective tissue
 Subcutaneous tissue (hypodermis)
 Adipose tissue (not part of the skin) anchors the skin to
underlying organs
 Shock absorber
 Insulates
Epidermis
 Five layers or strata
 Stratum basale (deepest)
 Stratum Spinosum
 Stratum Granulosum
 Stratum Lucidum
 Stratum corneum (outermost layer)
 Avascular – no blood supply
 Most cells are keratinocytes (produce keratin) that make the
skin tough and protective
Stratum basale
 Deepest layer of the epidermis
 Lies closest to the dermis
 Cells receive nutrition by diffusion from dermal cells
 Cells constantly undergo mitosis
 Daughter cells pushed upward away from the dermis and
eventually become part of the stratum spinosum, then the
stratum granulosum
 They become flatter and full of keratin, and die to become
part of the stratum lucidum (only in areas with no hair:
palms and feet)
Stratum corneum
 Outermost layer of epidermis
 20-30 cells thick
 Makes up about 75% of epidermal thickness
 These are dead, shingle-like cell remnants that are cornified
(full of keratin and very tough)
 Most protective layer, but shed cells constantly
 Produce a new stratum corneum every 25-45 days
Melanin
 Skin pigment
 Ranges from yellow to brown to black
 Produced by melanocytes (stratum basale cells)
 Exposure to sun stimulates cells to produce more melanin
 Stratum basale cells phagocytize the pigment
 Melanin makes a “umbrella” on the sunny side of the nucleus
to protect DNA from UV radiation
 Freckles and moles appear where melanin is concentrated
Sun exposure
 Excessive exposure to the sun damages skin
 Elastic fibers clump (making skin leathery)
 Depresses the immune system
 Can alter DNA in skin cells leading to skin cancer
 Black people rarely have skin cancer due to the protective effects of
melanin
Dermis
 Strong, stretchy
 Holds the body together
 Dense fibrous connective tissue has 2 regions
 Papillary
 reticular
 Varies in thickness
 Very thick on palms and soles of feet
 Very thin on eyelids
Papillary layer
 Upper dermal region
 Uneven with fingerlike projections (dermal papillae)
 May contain capillary loops to provide nutrients to the




epidermis
May have pain receptors and touch receptors (Meissner’s
corpuscles)
On palms and soles, form loops and whorled ridges to
provide grip
On fingertips, ridges have sweat pores (provide the
fingerprints)
Dermal papillae are genetically determined
Reticular layer
 Deepest skin layer
 Contains blood vessels, sweat and oil glands, and pressure




receptors (Pacinian corpuscles)
Have lots of phagocytes to get rid of bacteria
Collagen and elastin fibers give toughness
Collagen also binds water to keep the skin hydrated
Blood vessels help maintain body temperature
 Dilate to release heat
 Constrict to retain heat
Restriction of dermal blood supply
 Restriction of blood supply results in cell death
 Prolonged = decubitus ulcers
 Loss of blood supply results in cracks and permanent damage
 Degeneration and ulcers occur
Skin color
 Three pigments contribute to skin color
 Amount and kind of melanin in epidermis
 Amount of carotene deposited in stratum corneum (carotene is
a yellow-orange pigment found in orange, deep yellow, and
leafy green vegetables)
 Amount of oxygen bound to hemoglobin (pigment in red blood
cells) in the dermal blood vessels
 High melanin production produces brown-toned skin
 Caucasians have less melanin so the pink-rosy color from
hemoglobin shows through transparent cells
Skin color
 Low oxygen in hemoglobin makes caucasians appear bluish
(cyanosis)
 Common during heart failure and breathing disorders
 Doesn’t show in dark-skinned people but will be obvious in
fingernails and mucous membranes
 Skin color can be influenced by emotional stimuli
Skin color
 Skin color changes can sometimes indicate disease states
 Redness (erythema) can be due to embarrassment, fever,
hypertension, inflammation, or allergy
 Pallor (blanching): emotional stress (fear, anger), anemia, low
blood pressure, impaired blood flow
 Jaundice (yellowing): liver disorder causing bile pigments to be
absorbed in blood and deposited in tissues
 Bruises: blood has left circulation and clotted in tissues; unusual
bruising can indicate vitamin C deficiency or hemophelia
Skin appendages
 Cutaneous glands
 Exocrine glands that release secretions into the skin surface by
ducts
 Found in the dermis
 Include sebaceous glands and sweat glands
 Hairs and hair follicles
 Nails
Sebaceous (oil) glands
 Found all over skin (except palms and soles)
 Ducts empty into hair follicles, some open to the skin
surface
 Produce sebum (oil and fragmented cells)
 Keeps skin soft and moist
 Kills bacteria
 Become very active when male sex hormones are produced
(highly productive during puberty)
Problems with sebaceous glands
 Blocked ducts result in “whiteheads”
 Blockage that oxidizes and dries results in “blackhead”
 Acne is an active infection of the sebaceous glands or
“pimples”.
 Seborrhea (cradle cap) common in infants is the result of
over-active sebaceous glands
 Pink, raised lesions that become brown and crusty
 Sloughs off as oily dandruff
 Careful washing helps remove it
Sweat glands (sudoriferous)
 Widely distributed in skin
 Two types
 Eccrine
 More numerous
 Produce sweat (water, salts, and metabolic wastes) which is acidic
 Releases sweat to the skin via pores
 Aprocrine
 Found in axillary (under arms) and genital areas
 Ducts empty into hair follicles
 Secretion contains fatty acids, proteins, and sweat
Eccrine glands
 Sweat produced is used for
 Killing bacteria and preventing them from entering the body
(low pH inhibits bacterial growth)
 Controlling body temperature
 Evaporative cooling of the skin surface (sweat evaporates off the skin)
helps keep body temperature within a normal range)
Apocrine glands
 Secretions may appear milky or yellowish, are odorless
 Bacteria on the skin may use the proteins as a food producing
an unpleasant musky odor
 Glands begin to function during puberty, influenced by
androgens (hormone that controls male, secondary sex
characterisitcs)
 Minimal role in thermoregulation
 Activated by nerve fibers during pain, stress, and sexual
foreplay
Hairs and hair follicles
 Hair has minimal functions for humans
 Guards the top of the head
 Prevents debris from getting in eyes
 Keeps foreign particles out of respiratory tract
 In early humans (and mammals) hair is insulation and a means of
controlling body temperature.
Hairs and hair follicles
 Hairs produced by hair follicles
 Root is enclosed by the follicle
 Shaft projects from the skin surface
 Hair produced by division of stratum basale epithelial cells in
growth zone (hair bulb matrix)
 As hair grows, it becomes keratinized and dies (shaft is
mostly dead material and protein)
Hair
 Hair has 3 regions
 Medulla (central region)
 Cortex (bulky area around the medulla)
 Cuticle (surrounds the cortex)
 Keeps hairs separated and prevents matting
 Provides strength
 Wears away at the tip resulting in “split ends”
Hair
 Pigment
 Produced by melanocytes in hair bulb
 Varying amounts and types of melanin
Hair
 Sizes and shapes vary
 Depends on shape of the hair shaft
 Shaft is oval – hair is wavy
 Shaft is flat – hair is curly or kinky
 Shaft is round – hair is straight and coarse
 Born with all the follicles you will ever have
 Hair is everywhere EXCEPT palms, soles, nipples, lips
 Hormones produce hair as secondary sex characteristics
Hair follicles
 Arrector pili (smooth muscles) connect follicle to the dermal
tissue; if contracted make hair stand up (goose bumps)
 Has two areas
 Epidermal sheath
 Epithelial tissue and forms hair
 Dermal sheath
 Dermal connective tissue
 Supplies blood vessels and reinforcement
Nails
 Scale-like modification of the epidermis
 Three parts
 Free edge
 Body (visible attached portion)
 Root (embedded in the skin).
 Nail fold – skin folds that border / overlap the nail
 Cuticle – thick proximal nail fold
Nails
 Stratum basale
 Extends beneath the nail as the nail bed
 Thickened are is the nail matrix (makes nails grow)
 Nails become keratinized and die
N ails - mostly nonliving materials
- nearly transparent (appear pink due to blood supply)
- thickened nail matrix looks white (crescent at end) is the
lunula
Injuries to the skin
 Minor injuries (cuts, abrasions, blisters) heal quickly
 Skin regenerates epidermal cells every 25-45 days
 Infection is always a concern
Decubitus ulcers
 Pressure ulcers (bed sores)
 Caused by localized pressure that restricts blood flow causing
cells to die
 Most common over bony areas (lower back, coccyx, hips,
elbows, ankles) but can occur everywhere
 Most often seen in people undergoing prolonged bed rest or
those that are bed ridden
 Treatment includes oral antibiotics and removal of dead
tissue
 Tissue removal can be surgical or vacuum-assisted
Burns
 Due to exposure to excessive heat, corrosive chemicals,
electricity, or UV radiation
 Cause tissue damage and cell death
 First degree
 Only on epidermal layer
 Reddening of the skin and mild pain; heal within 1 week (sunburn)
 Second degree
 Damage to epidermis and upper dermis
 Blisters; intense pain, longer healing times
 Third degree
 Destroy entire thickness of skin
 Damages nerve endings (so initially no pain)
 Scarring and severe pain come later; must be treated with grafting
Burns
 Rule of nines- used to estimate the extent of the burned
tissue
 9% -for both anterior and posterior head and neck
 18% -for anterior and 18% for posterior of torso
 9% -for both anterior and posterior of each arm
 18% -for both anterior and posterior of each leg
 1% -for genital region
Infections
 Herpes infections causes small, painful, blister-like sores
 Herpes will stay with the person for a life time but is usually
dormant
 Flare-ups accompany periods of stress or illness
 Herpes varicella (chickenpox)- childhood disease; highly
infectious
 Herpes zoster (shingles)- caused by herpes varicella taking a
different form; extremely painful blisters/rash with headache,
fever, chronic nerve pain
Infections
 Herpes simplex 1 – (cold sores or fever blisters) occur
around the mouth
 Herpes simplex 2 – genital herpes
 Both forms are highly contagious and can be transmitted to
the mouth or genital areas
Infections
 Human papillomavirus (HPV)-(warts)
 On hands and fingers generally disappear without treatment
 Plantar warts grow inward on the feet and can be painful
 Genital warts are the most common STD in the U.S.; can be
spread by direct contact during vaginal, anal, or oral sex
 Two categories


Low risk – cause warts on skin around the genital area and anus but do
not cause cancer
High risk – cause cervical cancers, most anal cancers, and 50% of all
vaginal, vulvar, and penile cancers
o Cause cancers of soft palate, base of tongue, tonsils
Fungal infections
 Occur in areas of the body that are moist
 More prevalent in warm weather
 More common in people that have frequent periods of
sweating
Fungal infections
 Athlete’s foot (Tinea pedis)-most common; cracked, flaky skin
between toes on sides of foot, can be red and itchy; highly
contagious
 Jock itch (Tinea cruris)-in males around the groin and
scrotum; caused by sweating and friction from clothing;
spread through direct contact with skin or unwashed clothes
 Ringworm (Tinea corporis)-red, ring-shaped rash with pale
center; highly contagious, common in children
 Toenail fungus (Tinea unguium)-fungal infection under the
nails of the fingers or toes; discoloration and thickening;
needs a prescription
Bacterial infections
 Impetigo – highly contagious staph infection; common in
elementary children; pink, blister-like bumps on face around
mouth that develop a yellow crust
 Cellulitis – staph infection, inflamed area of the skin; red,
swollen, and painful
Inflammation of the skin
 General response to tissue injury or disease
 Increases blood flow, and sends WBCs to attack infectious
agents and destroy dead tissue
 Causes pain and swelling
Inflammatory conditions
 Pleurisy – inflammation of the pleura (membrane) that lines
the thoracic cavity and lungs; produce “friction rub” with
each breath; painful, can lead to a bluish color, shortness of
breath, coughing
 Psoriasis – redness and irritation; areas of thick, red skin
with flaky white patches (scales) that itch, burn, crack, bleed;
autoimmune disorder or inappropriate immune response to a
substance in the skin; NOT contagious but may be
hereditary; most common on elbows, knees, and trunk but
may occur anywhere
Skin cancers
 Most common cancers in U. S.
 Over exposre to the sun or UV radiation is a major risk
 Basal cell carcinoma – most common, least malignant; can be
surgically removed before they spread
 Squamous cell carcinoma – seen mostly on scalp, ears, lower
lip, backs of hands in fair-skinned people; grow rapidly and
can spread to lymph nodes; surgically removed and treated
with radiation to cure
 Malignant melanoma – most serious; typically dark colored
and irregular in shape