Integumentary System Flashcards
The Integumentary System includes the:
A. Skin aka “cutaneous membrane”: includes epidermis and dermis
B. Accessory Structures- hair, oil & sweat glands, nails and sensory receptors
General Anatomy of the Integumentary System
- A large organ composed of all 4 tissue types
- 22 square feet/ 2 square m.
- 7% of total body weight
- 1-2 mm thick on most of body
- Weight 10 lbs.
Functions of the Integumentary System
- Regulates /maintains body temperature
- Stores blood
- Protects body from external environment
- Detects cutaneous sensations/provides sensory information about the surrounding environment.
- Excretes & absorbs substances
- Synthesizes Vit-D
“CUTANEOUS MEMBRANE” Consists of 2 main sections:
1. Epidermis: • Superficial, thinner section • Contains epithelial tissue • Avascular 2. Dermis * Deep/ thicker section *Contains connective tissue * Vascular Note: Deep to the dermis is the subcutaneous layer or hypodermis which is not a part of the skin. It consists of areolar and adipose tissue; This layer is used for fat storage, an area for blood vessel passage, and an area of pressure-sensing nerve endings.
Epidermis is composed primarily of
stratified squamous epithelium.
4 Principle Cells of the Epidermis
- Keratinocytes -90% of epidermal cells
- Melanocytes - 8% of epidermal cells
- Langerhans cells - a small fraction of epidermal cells
- Merkel cells - the least numerous of epidermal cell
Keratinocytes -90% of epidermal cells
produce the protein keratin, which helps protect the skin and underlying tissue from heat, microbes, and chemicals. Also produce lamellar granules, which act as a waterproof sealant
Melanocytes - 8% of epidermal cells
produce the pigment melanin which contributes to skin color and absorbs damaging ultraviolet (UV) light
Langerhans cells - a small fraction of epidermal cells
(epidermal dendritic cells) are derived from red bone marrow
participate in immune response
Merkel cells - the least numerous of epidermal cell
contact a sensory structure called a tactile (Merkel) disc
detect touch sensations
5 Layers of the Epidermis
• There are 4 or 5 layers of the epidermis, depending upon the degree of friction and mechanical pressure applied to the skin
• From deepest to most superficial the layers of the epidermis are.
deep
1. stratum basale (stratum germinativum)
2. stratum spinosum
3. stratum granulosum
4. stratum lucidum (only in palms and soles)
5. stratum corneum superficial
Stratum Basale aka Stratum Germinativum
- deepest layer; a single row cuboidal or columnar keratinocytes
- contains merkel cells, melanocytes, keratinocytes & stem cells that divide repeatedly to produce keratinocytes
- keratinocytes have a cytoskeleton of “tonofilaments” aka keratin intermediate filaments that form the protein “keratin” in the more superficial layers
- cells attached to each other & to basement membrane by desmosomes & hemi-desmosomes
- when the germinal portion of the epidermis is destroyed, new skin cannot regenerate; a skin graft is required for healing
Stratum Spinosum
- 8 to 10 cell layers held together by desmosomes which provides both strength and flexibility to the skin
- during slide preparation, cells shrink and appear spiny (where attached to other cells by desmosomes.)
- melanin is taken in by keratinocytes (by phagocytosis) from nearby melanocytes
- Langerhans cells and projections of melanocytes are also present
Stratum Granulosum
- 3-5 layers of flat dying cells undergoing “apoptosis” (show nuclear degeneration)
- transition between the deeper, metabolically active strata and the dead cells of the more superficial strata
- keratinocytes contain dark-staining granules of the protein “keratohyalin” that converts tonofilaments (aka keratin intermediate filaments) into keratin
- keratinocytes contain lamellar granules that release lipid which repels water
- Stratum Lucidum
- 4 to 6 layers of clear, flat, dead cells
- present only in the fingers tips, palms of the hands, and soles of the feet
- provides an additional level of “toughness” to thick skin
- Stratum Corneum
• 25 to 30 layers of flat dead cells filled with keratin and surrounded by lipids
– continuously shed
• lamellar granules in this layer make it water-repellent.
• this layer acts as a barrier to light, heat, water, chemicals & bacteria
• constant exposure to friction will cause this layer to increase in depth with the formation of a callus, an abnormal thickening of the epidermis.
Epidermal growth factor (EGF) and other hormone-like proteins play
a role in epidermal growth.
Keratinization is replacement of
cell contents with the protein keratin; occurs as cells move to the skin surface over 4-6 weeks.
Keratinization
- Stem cells divide to produce keratinocytes
* As keratinocytes are pushed up towards the surface, they fill with keratin
The Dermis
Connective tissue layer composed of Dense Irregular Connective Tissue
Thicker than the epidermis; thickness varies, thickest in soles and palms
Dermis contains:
- Fibres
- Cells
- Hair Follicles, Glands, Nerves & Blood Vessels
Fibre types
a. collagen fibers: allow for strength / resist pull but allow for flexibility; commonly found in parallel bunches
b. elastic fibers: strong but can stretch 150%
Cell types;
a. fibroblasts: secrete the fibers and ground substance of the extracellular matrix
b. macrophages: engulf bacteria and cellular debris by phagocytosis
c. fat cells: store triglycerides
In what other type of tissues in the body might you find:
collagen fibres ?:
bone, cartilage, ligaments, tendons
In what other type of tissues in the body might you find:elastic fibres ?
blood vessels, lung tissue
what is elasticity:
what is extensibility:
what is tensile strength:
- the ability to return back to original shape
- the ability to stretch
- resists pulling or stretching forces
Two Major Regions of Dermis
A. papillary region
B. reticular region
Papillary region- Top 20% of dermis
• thin collagen and elastic fibres
• surface area is increased by finger like projections are called dermal papillae (ie. epidermal ridges) which:
– anchors epidermis to dermis
– contain capillaries that feed epidermis
– contains Meissner’s corpuscles (touch) & free nerve endings for sensations of heat, cold, pain, tickle, and itch
The Reticular Region- bottom 80% of dermis
• attached to the subcutaneous layer
• consists of
a. thick collagen fibres: arranged more regularly which allows skin to resist stretching
b. fibroblasts
c. wandering cells such as macrophages
d. some adipose cells in deepest regions
e. blood vessels, nerves, sebaceous glands, suderiferous glands, ducts & hair follicles occupy the spaces between fibers
The combination of collagen and elastic fibers in the reticular region give the skin
strength, extensibility and elasticity
dermal papillae (ie. epidermal ridges)
create a strong bond b/t epidermis and dermis in regions of high mechanical stress
increase surface area
i. which increase friction for better grasping ability/better grip
ii. increase number of Meissner corpuscles which increases tactile sensitivity
iii. create fingerprints which
The wide variety of colors in skin is due to three pigments in the dermis -
melanin, carotene, and hemoglobin (in blood in capillaries)
results vary from yellow to tan to black
Melanin
produced in epidermis by melanocytes
– melanocytes convert tyrosine to melanin
• UV in sunlight increases melanin production
– same number of melanocytes in everyone, but differing amounts of pigment produced
Carotene
in dermis
– yellow-orange pigment (precursor of vitamin A)
– found in stratum corneum & dermis
Hemoglobin
– red, oxygen-carrying pigment in blood cells
– if other pigments are not present, epidermis is translucent so pinkness will be evident
Difference in skin colour:
– d/t amount of pigment that melanocytes produce and transfer to keratinocytes
UV light Exposure
- increases melanin production
* Amount and darkness of melanin increases with exposure
UV Protection
- Melanin gives the body a tanned appearance and protects the body from UV damage
- Melanin absorbs UV radiation preventing damage to DNA of epidermal cells
- Tan is lost when dead keratinocytes are shed from stratum corneum
Callus:
an abnormal thickening of the stratum corneum; the result of constant exposure of skin to friction that stimulates increased cell and keratin production
Dandruff:
an excessive amount of keratinized cells shed from the skin of the scalp
Psoriasis
a chronic skin disorder characterized by a more rapid division and movement of keratinocytes through the epidermal strata
– cells shed in 3 to 5 days
– immature keratinocytes produce abnormal keratin which forms flaky silvery scales- MC at knees, elbows and scalp (dandruff)
tx: topical ointment and UV phototherapy
Skin Grafts 3 types:
- autograft: covering of wound with piece of healthy skin from self
- isograft is from twin
New skin cannot regenerate if stratum basale and its stem cells are destroyed
Striae or Stretch Marks:
small dermal blood vessels rupture when skin is overstretched and lateral bonds between collagen fibers break; scar tissue later develops appearing as silvery white streaks
Tension lines or lines of cleavage:
collagen fibres in reticular region orient in one direction; indicate the predominant direction of the underlying collagen fibers. Knowledge of these lines is especially important to plastic surgeons
• Why? Surgery along direction of fibres decreases scarring
Tattooing:
is a permanent coloration of the skin in which a foreign pigment is injected into the dermis. Pigment injected into dermis because it is more stable
Body Piercing
Potential challenges: • infection/ allergic reactions/ nerve or cartilage damage May interfere with: • Resuscitation masks • Airway management procedures • Urinary catheters • Radiographs • Delivery of baby
Freckles:
- genetic predisposition
* melanin accumulates in patches, reddish brown
Age Spots (Liver Spots)
- flat blemishes, light brown to black (darker than freckles)
- accumulations of melanin over time d/t sunlight
- don’t fade in winter
- MC over 40
Mole (nevus)
- Develops in childhood or adolescence
* Round flat or raised benign over-growth of melanocytes
Albinism
- Inherited inability to produce melanin d/t melanocytes inability to produce tyrosinase
- Melanin not present in hair, eyes and skin
- Affects vision and sunburn easily
Vitiligo
- Complete or partial loss of melanocytes from patches of skin= white spots
- May be d/t an auto-immune response in which antibodies attack melanocytes
Jaundice
•
- yellowish color to skin and whites of eyes
* buildup of yellow bilirubin in blood from liver disease
Cyanosis
- bluish color to nail beds and skin
* hemoglobin depleted of oxygen looks purple-blue
Pallor:
• paleness maybe d/t shock or anemia
Erythema
- redness of skin due to enlargement of capillaries in dermis
- during inflammation, infection, allergy or burns
for dark skinned people look to
nail beds, and gums for circulation issue
Transdermal Drug Administration
• method of drug passage across the epidermis and into the blood vessels of the dermis
– drug absorption is most rapid in areas where skin is thin (scrotum, face and scalp)
Pressure Ulcers
• Pressure ulcers, also known as decubitus ulcers
– caused by a constant deficiency of blood to tissues overlying a bony projection that has been subjected to prolonged pressure
– typically occur between bony projection and hard object such as a bed, cast, or splint
– the deficiency of blood flow results in tissue ulceration.
• Preventable with proper care
Eczema
inflammation of the skin characterized by red, blistering , dry, extremely itchy skin.
Occurs mostly in skin creases of the wrist, backs of the knees and fronts of the elbows
Typically begins in infancy and many children outgrow the condition
Cause unknown own, linked to genetics and allergies