Integumentary
Unit 3: The Integumentary System - Introduction and Skin (Chapter 6)
The Integumentary System
Includes the skin and its accessory structures (hair, nails, glands).
Integument is the largest organ.
Appearance can be indicator of internal problems in the body.
Functions of the Integumentary System:
Protection (from UV, abrasion, dehydration and microorganisms)
Sensation
Vitamin D Production
Temperature Regulation
Excretion (through sweat glands)
Skin Layers
Skin is made of two layers:
Superficial = Epidermis = stratified squamous epithelial ET
Deep = Dermis = dense irregular CT
Hypodermis
Skin lies on the Hypodermis, also called subcutaneous tissue. (Not actually considered a layer of skin!)
Made up of: Areolar CT which attaches skin to underlying bone, muscle, and organs. Adipose CT which helps with the body's insulation.
Hypodermis can be measured to estimate total body fat.
Contains major blood vessels. This makes it the site of subcutaneous injections.
Epidermis (The Stratified Squamous ET)
Avascular.
Composed of several layers of cells called strata.
Thin skin has 4 layers. The stratum that is missing is the stratum lucidum.
Thick skin has 5 layers. Found on the palms of hands and soles of feet.
The primary cell of the epidermis is the keratinocyte.
Epidermal layers (deep to superficial):
Stratum Basale: deepest layer; cells undergoing mitosis.
Stratum Spinosum
Stratum Granulosum: cells start to die/fill with keratin.
Stratum Lucidum: present only in thick skin.
Stratum Corneum: most superficial layer; cells are dead and keratinized.
Dermis
Found beneath/deep to the basement membrane.
Contains Hair follicles, glands, smooth muscle, and nerve endings.
Fibers give skin its flexibility and strength.
The orientation of collagenous fibers creates cleavage or tension lines. Surgeons cut parallel to tension lines to reduce scarring.
If the skin is overstretched/stretched too quickly, the dermis becomes damaged, leaving lines called striae or stretch marks.
The upper part of the dermis has extensions called dermal papillae which form fingerprints and footprints.
Unit 3: The Integumentary System - Skin Pigmentation (Chapter 6)
What gives skin its color?
In one person, changes in skin coloration can occur for a variety of reasons. Some examples:
Erythema: fast blood flow; gives skin a reddish hue (AKA: blushing).
Pallor: decrease in blood flow; skin looks pale.
Thicker stratum corneum: masks underlying blood vessels; skin is less pink.
Cyanosis: poor circulation of blood; skin looks blue.
Blue Bruises and Blood Vessels
Why do bruises and some blood vessels look blue if they contain red blood?
Blue light reflects off of dark pigments in the dermis or hypodermis.
Light is then scattered by the collagen fibers and overlying tissue giving it a blue/green hue on the surface.
Blood is ALWAYS red.
Skin Pigmentation
Melanin: pigmented polymer responsible for skin, hair, and eye color.
The production of melanin/pigments is actually protective: it absorbs UV radiation/light.
Melanin is made by melanocytes (cells) in the stratum basale of the epidermis.
Melanosomes are vesicles that package and move melanin.
Melanin as Protection
When exposed to UV light, melanocytes are stimulated to make more melanin to absorb more light.
This excess melanin darkens your skin (tanning).
Excess UV light exposure damages the DNA in melanocytes, which can result in skin cancer.
Types of Skin Cancer
Squamous cell carcinoma: develops from cells superficial to stratum basale. If it extends down into the dermis, it can metastasize and be fatal.
Basal cell carcinoma: begins in the stratum basale and extends into the dermis. Most common type.
Malignant melanoma: arises from melanocytes. Most rare but most deadly.
Unit 3: The Integumentary System - Accessory Skin Structures (Chapter 6)
Nails
Thin plate consisting of layers of dead stratum corneum with a very hard type of keratin.
Eponychium (cuticle): stratum corneum that extends into nail plate.
Hyponychium: part under your nail at the distal end; prevents infections.
The nail matrix is where the nail grows.
Part of the nail matrix, the lunula (whitish, crescent-shaped area) is where the most nail growth occurs.
Nail appearance may mirror health: Bluish nails = circulatory problems.
Skin Glands
Sebaceous Glands
Associated with hair follicles.
Produce sebum, an oily, white substance that keeps hair and skin soft, pliable and waterproof.
Sudoriferous Glands (= sweat glands)
Eccrine Sweat Glands (Also called merocrine glands)
Most numerous.
Function in thermoregulation/cooling.
Apocrine Sweat Glands
Found in the armpits/axilla, genitals, and areola.
Secretion contains organic compounds/proteins/fats. Odor comes from bacterial decomposition.
Ceruminous Glands
Modified sweat glands located in the external ear canal.
Secrete cerumen (earwax).Physicians use the Rule of Nines to determine how to treat a burn victim.
Skin surfaces are divided into regions accounting fo
Hair
Anatomy of Hair
Inner, soft center: Medulla.
Cortex surrounds medulla.
Hair shaft: protrudes above the surface of skin.
Hair follicle: tube-like depression in the dermis that contains the hair root.
Smooth muscle cells called arrector pili muscle are associated with each hair follicle.
Upon contraction, hair stands up and produces a raised area of skin called goosebumps.
Hair grows longer as more cells are added to the hair bulb.
When a new hair does not replace the old, it leads to alopecia/balding.
Unit 3: The Integumentary System - Functions of the Integumentary System (Chapter 6)
Vitamin D Production
Why do we need Vitamin D?
Maintains bone density/mass and healthy bone development.
Stimulates calcium and phosphate uptake.
How does the skin make Vitamin D?
When exposed to UV radiation/sunlight, a precursor molecule of Vitamin D is produced in the skin/epidermis.
This molecule is carried to the liver and kidneys where it is modified into active Vitamin D.
Regulation of Body Temperature
If body temperature rises ABOVE the set point:
Vasodilation: blood vessels dilate/widen to bring heat to the surface of the body.
Radiation: heat escapes from warmer surfaces to cooler surroundings.
Conduction: heat moves from body directly into molecules of cooler objects that are in contact with body's surface.
Convection: heat is lost to air and is replaced by cooler air moving toward the body.
Evaporation: eccrine glands release sweat/water; as fluid changes from liquid to gas/vapor, it carries away the heat.
If these methods do not work, hyperthermia/fever results.
If body temperature drops BELOW the set point:
1.) Vasoconstriction: blood vessels constrict to reduce heat loss.
Sweat glands are inactive/inhibited.
Shivering: muscle contraction generates ATP and body heat.
Prolonged exposure to cold leads to hypothermia.
Unit 3: The Integumentary System - Burns (Chapter 6)
How do you classify a burn?
Based on depth of damage.
Partial-Thickness Burns
Superficial Partial-Thickness Burn (First degree burn)
Injures only the epidermis.
Red, painful, slight edema/swelling.
Healing: No scarring.
Deep Partial-Thickness Burn (Second degree burn)
Damage epidermis and minimal damage to dermis.
Redness, blisters, edema, and pain.
Healing: May scar (depends on how deep into dermis burn penetrated).
Full-Thickness Burn
Full-Thickness Burn (Third degree burns)
Epidermis, dermis, and underlying tissue are completely destroyed.
Skin will look dry and leathery; red, black, or even white in color.
Are usually painless because sensory receptors/nerves in dermis have been destroyed.
Healing: Extremely slow healing time. Usually results in scarring.
Treatments for 3rd degree burns:
Autograft: removing a thin layer of skin from unburned region and transplanting to injured area.
Homograft/Allograft: skin from a cadaver is transplanted as a temporary cover.
Tissue engineering: growing new skin in a lab.
Physicians use the Rule of Nines to determine howr 9% (or a multiple of 9%) of the total surface area.
The rule of nines accounts for variations in age and size between different individuals.