Integumentary System Flashcards
largest system of the body:
integument
16% of body weight
–1.5 to 2 m2 in area
Parts of the Integument
cutaneous membrane (skin)
2.accessory structures
Parts of the
Cutaneous Membrane
•Outer epidermis:
–superficial epithelium (epithelial tissues)
•Inner dermis:
–connective tissues
Accessory Structures
Originate in the dermis
•Extend through the epidermis to skin surface:
–hair
–nails
–multicellular exocrine glands
Connections
•Circulatory system:
–blood vessels in the dermis
•Nervous system:
–sensory receptors for pain, touch, and temperature
The Subcutaneous Layer
(superficial fascia or hypodermis):
–loose connective tissue
–below the dermis
–location of hypodermic injections
Functions of Skin
Protects underlying tissues and organs
•Excretes salts, water, and organic wastes (glands)
•Maintains body temperature (insulation and evaporation)
Synthesizes vitamin D3
•Stores lipids
•Detects touch, pressure, pain, and temperature
Avascular stratified squamous epithelium
•Nutrients and oxygen diffuse from capillaries in the dermis
Epidermis
Cells of the Epidermis
Keratinocytes
Keratinocytes
contain large amounts of keratin
–the most abundant cells in the epidermis
Thin Skin
Covers most of the body
•Has 4 layers of keratinocytes
Thick Skin
Covers the palms of the hands and soles of the feet
•Has 5 layers of keratinocytes
5 strata of keratinocytes in thick skin
From basal lamina to free surface:
–stratum germinativum
–stratum spinosum
–stratum granulosum
–stratum lucidum
–stratum corneum
Stratum Germinativum
has many germinative (stem) cells or basal cells
–is attached to basal lamina by hemidesmosomes
–forms a strong bond between epidermis and dermis
Structures of
Stratum Germinativum
Epidermal ridges (e.g., fingerprints)
•Dermal papillae (tiny mounds):
–increase the area of basal lamina
–strengthen attachment between epidermis and dermis
Cells of Stratum Germinativum
Merkel cells:
–found in hairless skin
–respond to touch (trigger nervous system)
•Melanocytes:
–contain the pigment melanin
–scattered throughout stratum germinativum
Stratum Spinosum
The “spiny layer”:
–produced by division of stratum germinosum
–8–10 layers of keratinocytes bound by desmosomes
–cells shrink until cytoskeletons stick out (spiny)
Cells of Stratum Spinosum
Continue to divide, increasing thickness of epithelium
•Contain Langerhans cells, active in immune response
Stratum Granulosum
The “grainy layer”
•Stops dividing, starts producing:
–keratin:
–keratohyalin
keratin
a tough, fibrous protein
•makes up hair and nails
keratohyalin
dense granules
•cross-link keratin fibers
Cells of Stratum Granulosum
Produce protein fibers
•Dehydrate and die
•Create tightly interlocked layer of keratin surrounded by keratohyalin
Stratum Lucidum
The “clear layer”:
–found only in thick skin
–covers stratum granulosum
Cells of Stratum Lucida
Flat
•Dense
•Filled with keratin
Stratum Corneum
The “horn layer”:
–exposed surface of skin
–15 to 30 layers of keratinized cells
–water resistant
–shed and replaced every 2 weeks
Keratinization
The formation of a layer of dead, protective cells filled with keratin
•Occurs on all exposed skin surfaces except eyes
Skin Life Cycle
It takes 15–30 days for a cell to move from stratum germinosum to stratum corneum
Perspiration
Insensible perspiration:
•Sensible perspiration:
Insensible perspiration
interstitial fluid lost by evaporation through the stratum corneum
Sensible perspiration
water excreted by sweat glands
Dehydration results
from damage to stratum corneum, e.g., burns and blisters (insensible perspiration)
–from immersion in hypertonic solution, e.g., seawater (osmosis)
Hydration
results from immersion in hypotonic solution, e.g., freshwater (osmosis)
–causes stretching and wrinkling skin
Skin color depends on:
the pigments carotene and melanin
–blood circulation (red cells)
Carotene
Orange-yellow pigment
•Found in orange vegetables
•Accumulates in epidermal cells and fatty tissues of the dermis
•Can be converted to vitamin A
Melanin
Yellow-brown or black pigment
•Produced by melanocytes in stratum germinativum
•Stored in transport vesicles (melanosomes)
•Transferred to keratinocytes
melanosomes
transport vesicles
Function of Melanocytes
Melanin protects skin from sun damage
Skin color depends on melanin production, not number of melanocytes
blood vessels dilate from
Heat
Skin turns pale from decreased blood flow
Cyanosis
Bluish skin tint
•Caused by severe reduction in blood flow or oxygenation
Addison’s disease
and other diseases of pituitary gland
–skin darkening
Vitiglio
loss of melanocytes
–loss of color
Epidermal cells produce_________ in the presence of UV
Cholecalciferol (Vitamin D3)
Liver and kidneys convert vitamin D into________
to aid absorption of calcium and phosphorus
Calcitrol
Insufficient vitamin D
rickets
Epidermal Growth Factor (EGF)
powerful peptide growth factor
produced by glands (salivary and duodenum)
Functions of EGF
Promotes division of germinative cells
•Accelerates keratin production
•Stimulates epidermal repair
•Stimulates glandular secretion
Dermis
Is located between epidermis and subcutaneous layer
•Anchors epidermal accessory structures
Papillary Layer
Consists of areolar tissue
•Contains smaller capillaries, lymphatics, and sensory neurons
•Has dermal papillae projecting between epidermal ridges
The Reticular Layer
dense irregular connective tissue
•Contains larger blood vessels, lymph vessels, and nerve fibers
•Contains collagen and elastic fibers
•Contains connective tissue proper
Dermatitis
An inflammation of the papillary layer
•Caused by infection, radiation, mechanical irritation, or chemicals (e.g., poison ivy)
•Characterized by itch or pain
Characteristics of Dermis
Strong, due to collagen fibers
•Elastic, due to elastic fibers
•Flexible (skin turgor)
Lines of Cleavage
Collagen and elastic fibers in the dermis
resist force in a specific direction
Arteries
Cutaneous plexus
Papillary plexus
Cutaneous plexus
a network of arteries along the reticular layer
Papillary plexus
capillary network from small arteries in papillary layer
Veins
Venous plexus
Contusion
Venous plexus:
capillary return deep to the papillary plexus
Contusion
damage to blood vessels resulting in “black and blue” bruising
Nerve fibers in skin control
blood flow
–gland secretions
–sensory receptors
Tactile disks
monitor Merkel cells
subcutaneous layer or hypodermis
lies below the integument
–stabilizes the skin
–allows separate movement
Structure of the Hypodermis
made of elastic areolar and adipose tissues
–connected to the reticular layer of integument by connective tissue fibers
Adipose Tissue
Deposits of subcutaneous fat:
–have distribution pattern determined by hormones
–are reduced by cosmetic liposuction
Integumentary
Accessory Structures
Hair, hair follicles, sebaceous glands, sweat glands, and nails:
Functions of Hair
Protects and insulates
•Guards openings against particles and insects
•Is sensitive to very light touch
The Hair Follicle
Is located deep in dermis
•Produces nonliving hairs
•Is wrapped in a dense connective-tissue sheath
•Base is surrounded by sensory nerves (root hair plexus)
Accessory Structures of Hair
Arrector pili
Sebaceous glands
Arrector pili:
involuntary smooth muscle
–causes hairs to stand up
–produces “goose bumps
Sebaceous glands
lubricate the hair
–control bacteria
As hair is produced, it is
keratinized
Club hair:
is not growing
–is attached to an inactive follicle
hair growth cycle
follicle becomes active
–produces new hair
–club hair is shed
Vellus hairs
soft, fine
–cover body surface
Terminal hairs
heavy, pigmented
–head and eyebrows
–other parts of body after puberty
Hair Color
Produced by melanocytes at the hair papilla
Sebaceous glands (oil glands
holocrine glands
–secrete sebum
Sweat glands
merocrine glands
–watery secretions
Types of Sebaceous Glands
Simple branched alveolar glands:
Sebaceous follicles
Simple branched alveolar glands
associated with hair follicles
Sebaceous follicles:
discharge directly onto skin surface
Sebum
Contains lipids and other ingredients
•Lubricates and protects the epidermis
•Inhibits bacteria
Apocrine
found in armpits, around nipples, and groin
Merocrine
widely distributed on body surface
–especially on palms and soles
Apocrine Sweat Glands
Merocrine secretions, not apocrine
•Associated with hair follicles
•Produce sticky, cloudy secretions
•Break down and cause odors
Merocrine Sweat Glands
Also called eccrine glands:
–coiled, tubular glands
–discharge directly onto skin surface
–sensible perspiration
–water, salts, and organic compounds
Functions of Merocrine Sweat
Cools skin
•Excretes water and electrolytes
•Flushes microorganisms and harmful chemicals from skin
Thermoregulation
is the main function of sensible perspiration
–works with cardiovascular system
–regulates body temperature
Nail
made of dead cells packed with keratin
Repair of Localized Injuries
to the Skin: Step 1
Bleeding occurs
•Mast cells trigger inflammatory response
Repair of Localized Injuries
to the Skin: Step 2
A scab stabilizes and protects the area
The Inflammatory Response
Germinative cells migrate around the wound
•Macrophages clean the area
•Fibroblasts and endothelial cells move in, producing granulation tissue
Repair of Localized Injuries
to the Skin: Step 3
Fibroblasts produce scar tissue
•Inflammation decreases, clot disintegrates
Repair of Localized Injuries
to the Skin: Step 4
Fibroblasts strengthen scar tissue
•A raised keloid forms
