Chapter 6 Flashcards
What does the integumentary system consist of?
The skin and its accessory organs; hair, nails, and cutaneous glands
Inspection of the skin, hair, and nails is significant part of a physical exam
What is the skin vulnerable to?
Radiation, trauma, infection, and injurious chemicals
What is dermatology?
Scientific study and medical treatment of the integumentary system
What are the two layers of the skin?
Epidermis: stratified squamous epithelium
Dermis: connective tissue layer
What is the hypodermis and is it part of the integumentary system?
Another connective tissue layer below the dermis
Not part of integumentary system
Where is thick skin found and what are its characteristics?
On palms and sole, has sweat glands but no hair follicles or sebaceous glands
Epidermis from 0.4 to 0.6 mm thick
Where is thin skin found and what are its characteristics?
Covers rest of the body, possesses hair follicles, sebaceous glands, and sweat glands
Epidermis from 0.075 to 0.150 mm thick
What is the epidermis composed of?
Keratinized stratified squamous epithelium
What are the five types of cells of the epidermis?
Stem cells, Keratinocytes, Melanocytes, Tactile (Merkel) cells, Dendritic (Langerhans) cells
What is the function of stem cells in the epidermis?
Undifferentiated cells that give rise to keratinocytes
In deepest layer of epidermis (stratum basale)
What is the function of melanocytes in the epidermis?
Synthesize pigment melanin that shields DNA from ultraviolet radiation
What is the function of tactile (Merkel) cells in the epidermis?
Touch receptor cells associated with dermal nerve fibers
What is the function of dendritic (Langerhans) cells in the epidermis?
Macrophages originating in bone marrow that guard against pathogens
What is the composition of stratum basale?
A single layer of cuboidal to low columnar stem cells and keratinocytes resting on the basement membrane
Melanocytes and tactile cells are scattered among the stem cells and keratinocytes
What is the composition of stratum spinosum?
Produce more and more keratin filaments which causes cell to flatten; the higher up in this stratum, the flatter the cells appear
Consists of 8-10 layers of keratinocytes
What is the composition of stratum granulosum?
Consists of three to five layers of flat keratinocytes
Contains coarse dark-staining keratohyalin granules
What is the name of the layer found throughout the stratum?
Stratum spinosum
Named for artificial appearance created in histological section; involved in immune responses, arise from red bone marrow
Numerous desmosomes and cell shrinkage produces spiny appearance
What is the name of the layer consisting of three to five layers of flat keratinocytes?
Stratum granulosum
Consists of three to five layers of flat keratinocytes
Contains coarse dark-staining keratohyalin granules
In which layer are keratinocytes densely packed with eleidin?
Stratum lucidum
Seen only in thick skin
Keratinocytes are densely packed with eleidin
Eleidin intermediate product in keratin maturation; UV light protection
Cells have no nucleus or other organelles
Zone has a pale, featureless appearance with indistinct boundaries
Which layer consists of up to 30 layers of dead, scaly, keratinized cells?
Stratum corneum
Up to 30 layers of dead, scaly, keratinized cells
Dry thickened surface
Form durable surface layer
Surface cells flake off (exfoliate)
Resistant to abrasion, penetration, and water loss
How long does it take for newly formed keratinocytes to push the older ones toward the surface?
The Life History of a Keratinocyte
Newly formed keratinocytes push the older ones toward the surface
In 30 to 40 days a keratinocyte makes its way to the skin surface and flakes off
Slower in old age
Faster in injured or stressed skin
Calluses or corns—thick accumulations of dead keratinocytes on the hands or feet
Dandruff: clumps of dander stuck together by sebum (oil)
It takes 15–30 days for a cell to move from stratum basale to stratum corneum
What are the three important developments that occur in the stratum granulosum?
In stratum granulosum three important developments occur
Keratinocyte nucleus and other organelles degenerate; cells die
Keratohyalin granules release a protein filaggrin
Binds the keratin filaments together into coarse, tough bundles
Membrane-coating vesicles release lipid mixture that spreads out over cell surface and waterproofs it
Epidermal water barrier—forms between stratum granulosum and stratum spinosum
Lipids secreted by keratinocytes
Tight junctions between keratinocytes
Thick layer of insoluble protein on the inner surfaces of the keratinocyte plasma membranes
What is the name of the connective tissue layer beneath the epidermis?
The Dermis
Dermis—connective tissue layer beneath the epidermis
Ranges from 0.2 mm (eyelids) to 4 mm (palms, soles)
Composed mainly of collagen with elastic fibers, reticular fibers, and fibroblasts
Well supplied with blood vessels, sweat glands, sebaceous glands, and nerve endings
What are the upward fingerlike extensions of the dermis?
The Dermis
Hair follicles and nail roots are embedded in dermis
Smooth muscle (piloerector muscles) associated with hair follicles
Contract in response to stimuli such as cold, fear, and touch—goose bumps
Dermal papillae—upward fingerlike extensions of the dermis
Friction ridges on fingertips that leave fingerprints
What is the name of the layer that is a superficial zone of dermis?
Papillary layer—superficial zone of dermis
Thin zone of areolar tissue in and near the dermal papilla
Allows for mobility of leukocytes and other defense cells should epidermis become broken
Rich in small blood vessels
What is the name of the subcutaneous tissue layer?
The Hypodermis
Hypodermis—Subcutaneous tissue
More areolar and adipose than in dermis
Pads body
Binds skin to underlying tissues
Drugs introduced by injection
Highly vascular and absorbs them quickly
Subcutaneous fat
Energy reservoir
Thermal insulation
8% thicker in women
What is the most significant factor in skin color?
Skin Color
Melanin—most significant factor in skin color
Produced by melanocytes
Skin color depends on melanin production, not number of melanocytes
Eumelanin—brownish black
gives skin and hair black and brown coloring.
Pheomelanin—a reddish yellow sulfur-containing pigment
may become carcinogenic when exposed to UV rays
Hemoglobin—red pigment of red blood cells
Adds reddish to pinkish hue to skin
Carotene—yellow pigment acquired from egg yolks and yellow/orange vegetables
Concentrates in stratum corneum and subcutaneous fat
What is the condition characterized by blueness of the skin from deficiency of oxygen in the circulating blood?
Skin Color
Cyanosis—blueness of the skin from deficiency of oxygen in the circulating
Melanin
A reddish yellow sulfur-containing pigment
May become carcinogenic when exposed to UV rays
Hemoglobin
Red pigment of red blood cells
Adds reddish to pinkish hue to skin
Carotene
Yellow pigment acquired from egg yolks and yellow/orange vegetables
Concentrates in stratum corneum and subcutaneous fat
Cyanosis
Blueness of the skin from deficiency of oxygen in the circulating blood
Airway obstruction (drowning or choking)
Lung diseases (emphysema or respiratory arrest)
Cold weather or cardiac arrest
Erythema
Abnormal redness of the skin due to dilated cutaneous vessels
Exercise, hot weather, sunburn, anger, or embarrassment
Albinism
Genetic lack of melanin that results in white hair, pale skin, and pink eyes
Inherited recessive condition
Jaundice
Yellowing of skin and sclera due to excess of bilirubin in blood
Cancer, hepatitis, cirrhosis, other compromised liver function
Hematoma (bruise)
Mass of clotted blood showing through skin
Pallor
Pale or ashen color when there is so little blood flow through the skin that the white color of dermal collagen is visible
Emotional stress, low blood pressure, circulatory shock, cold, anemia
Evolution of Skin Color
Results from combination of evolutionary selection pressures
Especially differences in exposure to ultraviolet radiation (UVR)
UVR has two adverse effects
Causes skin cancer
Breaks down folic acid needed for normal cell division, fertility, and fetal development
UVR has one desirable effect
Stimulates synthesis of vitamin D necessary for dietary calcium absorption
Freckles and moles
Tan to black aggregations of melanocytes
Freckles are flat, melanized patches
Moles (nevus) are elevated melanized patches often with hair
Moles should be watched for changes in color, diameter, or contour
May suggest malignancy (skin cancer)
Hemangiomas (birthmarks)
Patches of discolored skin caused by benign tumors of dermal blood capillaries
Some disappear in childhood, others last for life
What are hair, nails, and cutaneous glands considered as?
Accessory organs of the skin
Source: Hair and Nails
What makes up the stratum corneum of the skin?
Pliable soft keratin
Source: Hair and Nails
What makes up hair and nails?
Compact hard keratin
Source: Hair and Nails
What are the three kinds of hair that grow over the course of our lives?
Lanugo, Vellus, Terminal
Source: Hair
What are the functions of hair?
Protection, Facial expression, Heat retention, Sensory reception, Visual identification, Chemical signal dispersal
Source: Functions of Hair
What are nails composed of?
Very thin, dead cells packed with hard keratin
Source: Nails
What is the nail matrix responsible for?
Nail growth
Source: Nails
What are the two kinds of sweat glands?
Merocrine (eccrine) sweat glands, Apocrine sweat glands
Source: Sweat Glands
What is produced by the sebaceous glands?
Sebum
Source: Sebaceous Glands
Ducts lead to nearby hair follicles
Produce sweat that is thicker, milky, and contains fatty acids
Scent glands that respond to stress and sexual stimulation
Develop at puberty
Pheromones—chemicals that influence the physiology of behavior of other members of the species
Bromhidrosis—disagreeable body odor produced by bacterial action on fatty acids
Sebaceous Glands
Sebum—oily secretion produced by sebaceous glands
Flask-shaped glands with short ducts opening into hair follicle
Holocrine gland—secretion consists of broken-down cells
Replaced by mitosis at base of gland
Keeps skin and hair from becoming dry, brittle, and cracked
Secretion stimulated by hormones, especially androgens
Other integumentary glands
Ceruminous glands
Modified apocrine sweat glands
Located only in external ear canal
Secretions of waterproof earwax, cerumen
Traps foreign material
Lubricates acoustic meatus and eardrum
Mammary glands
Modified apocrine sweat glands of breast
Only function in pregnant and lactating females
Produce milk
Tissue Repair
Damaged tissues can be repaired in two ways:
Regeneration: replacement of dead or damaged cells by the same type of cell as before
Restores normal function
Skin injuries and liver regenerate
Fibrosis: replacement of damaged cells with scar tissue
Holds organs together
Gap filled with scar tissue
Does not restore normal function
Severe cuts and burns, healing of muscle injuries, scarring of lungs in tuberculosis
Bleeding into the wound
(1) Cut blood vessels bleed into wound:
Severed blood vessels bleed into cut
Mast cells and damaged cells release histamine
Dilates blood vessels
Increases blood flow to area
Makes capillaries more permeable
Blood plasma seeps into the wound carrying:
Antibodies
Clotting proteins
Blood cells
Scab
(2) Blood clot forms in the tissue
Loosely knitting edges of cut together
Inhibits spread of pathogens from injury site to healthy tissue
Forms scab that temporarily seals wound and blocks infection
Macrophages phagocytize and digest tissue debris
Formation of granulation tissue
(3) New capillaries sprout from nearby vessels and grow into wound
Deeper portions become infiltrated by capillaries and fibroblasts
Transform into soft mass called granulation tissue
Macrophages remove the blood clot
Fibroblasts deposit new collagen
Begins 3–4 days after injury and lasts up to 2 weeks
Epithelial regeneration and connective tissue fibrosis
(4) Epithelium regenerates
Connective tissue undergoes fibrosis
Scar tissue may or may not show through epithelium
Remodeling (maturation) phase begins several weeks after injury and may last up to 2 years
Skin Cancer
Skin cancer—induced by the UV rays of the sun
Most often on the head and neck
Most common in fair-skinned people and the elderly
One of the most common cancer
One of the easiest to treat
Has one of the highest survival rates if detected and treated early
Three types of skin cancer named for the epidermal cells in which they originate
Basal cell carcinoma, squamous cell carcinoma, and malignant melanoma
Burns
Classified according to the depth of tissue involvement
First-degree burn: partial-thickness burn; involves only the epidermis
Marked by redness, slight edema, and pain
Heals in a few days
Most sunburns are first-degree burns
Second-degree burn: partial-thickness burn; involves the epidermis and part of the dermis
Leaves part of the dermis intact
Red, tan, or white
Two weeks to several months to heal and may leave scars
First-degree burn
Partial-thickness burn; involves only the epidermis
Most sunburns are first-degree burns
Second-degree burn
Partial-thickness burn; involves the epidermis and part of the dermis
Two weeks to several months to heal and may leave scars
Third-degree burn
Full-thickness burn; the epidermis and all of the dermis, and often some deeper tissues (muscles or bones) are destroyed
Often requires skin grafts
Needs fluid replacement and infection control
Epidermis Layers from deep to superficial
Stratum basale
2.Stratum spinosum
3.Stratum granulosum
4.Stratum lucidum
5.Stratum corneum
