Integumentary system
The primary role of the integumentary system is protection
Dermatology: study and treatment of the integumentary system: the skin(integument), hair, nails, and subcutaneous glands.
Skin: largest organ of the body
There are two layers of skin: The epidermis and the dermis
Epidermis: Keratinized stratified squamous epithelium
superficial layer
thicker on acral skin
avascular (nutrients diffused from deeper connective tissue)
sparse nerve endings
cells in the epidermis
Keratinocytes: synthesize keratin (found in many layers)
make up about 90% of cells in the epidermis, arise from the deepest layer and are actively dividing cells, these cells move upward towards the apical surface , they are no longer dividing and are dead, dry, and full of keratin
Stem cells: Divide and produce keratinocytes (Stratum Basale)
Melanocytes: manufacture and secrete a pigment called melanin in response to the skins exposure to the suns harmful UV rays (stratum Basale)
Pigment is stored in melanosomes which move melanin along the melanocyte until the granules are passed onto the neighboring keratinocytes
melanin forms a shield in order to protect keratinocytes from damage response is commonly known as sun tanning.
darker skinned people naturally have more, darker melanin which their keratinocytes can retain longer, compared to lighter skinned people. The excess production of melanin is a direct result of our skins exposure to the sun and why it makes sense that darker skinned people would burn less and experience skin cancer less frequently.
Tactile (merkle) cells: touch receptors that join with nerves (only in stratum basale) (present at epidermal-dermal junction, part of sensory reception function of the skin)
Dendritic (langerhans) cells: cells that work in a protective capacity by activating out immune system and by ingesting any foreign particles that may have penetrated the barrier. (in stratum spinosum and stratum granulosome)
Layers of the epidermis
mnemonic (Before, Signing, Get, Legal, Counsel)
Stratum Basale: is the deepest layer of the epidermis and is attached to the underlying dermis , only one layer thick, has varied cell types)
Stratum Spinosum: several cell layers thick (8-10 cell layers), thickest layer of the epidermis.
Stratum Granulosome: cells have dark granules, (1-5 layers thick, nuclei being to disintegrate and cells begin to die as they move to the layers above)
Stratum lucidum: Only in thick skin, cells lack organelles
Stratum: Corneum: uppermost or apical layer, composed of several layers of dead scaly skin (25-30 layers) filled only with keratin.
these cells continuously shed and are familiar to use as dead skin or flakes and dandruff.
Dermis: second layer of skin found deep to the epidermis
dermis is made of connective tissue
rich in collagen fiber (partly where skin gets it flexibility, loss of collagen causes wrinkles)
contains cutaneous glands, hair follicles, arrector muscles, and nail roots.
The dermis is made up of two layers: Papillary and Reticular layer
Papillary layer: Nipple shaped, superficial (upper) thin layer, made up of areolar connective tissue, it makes up about 20% of the dermis. Like areolar connective tissue the papillary layer contains WBC (macrophages and mast cells) and fibroblast
the wavy finger like projections called dermal papillae anchors the epidermis to the dermis which increases the surface area , it also increases the surface area for gas, nutrients, and waste exchange between the layers.
Reticular layer: About 80% of the dermis, deepest layer, made up on dense irregular tissue, contains blood vessels to nourish it, as well as thick collagen fibers.
Extreme stretching of pregnancy or obsesity can tear collage fibers the result is pink or white scars known as stretch marks (Striae)
Hypodermis: not a true layer if the skin, it is located deep to the dermis and contains adipose (subcutaneous fat) and areolar tissue. Function is energy storage, thermal insulation, and connection to deeper tissue.
Thick skin vs thin skin:
thick skin (acral): palms, front of fingers, soles, plantar toes. hairless, no sebaceous glands, sweats. Adaptive for high friction.
Thin skin: covers most of body. hairy, has both sebacous glands and sweat glands.
Function of the skin:
Waterproof: protects us against water loss
Resistance to trauma and infection:
contains melanocytes which protects us from harmful uv rays
contains thick bands of collagen which protects us from scrapes and external penetration by sharp objects.
Produces secretions which destroy bacteria on surface
Thermoregulation:
when too hot blood vessels dilate allows heat to be carried to blood stream and dissipate through skin.
when too cold blood vessels constrict in order to maintain heat within the body and divert to vital organs.
Synthesis of Vitamin D : When skin is exposed to sunlight Vitamin D precursors is formed, which is sent through the blood stream to the liver and kidney to be converted into vitamin D. Vitamin D plays a role in absorption of calcium which is needed for bone growth and development.
Sensation: sensory receptors in the skin keep us aware of the conditions occurring at our body surface.
Nonverbal communication: conveys emotions, health statuses, and physiological responses without using spoken words. Body language.
Dianostic of skin color:
Cyanosis: Blue; lack of oxygen
Erythema: red; increased blood flow
Pallor: pale or ashen; reduced blood flow
albinism: white genetic lack of melanin
jaundice: yellow; liver and bilirubin
Hematoma: purple; bruised
skin markings
Friction ridges of fingertips: Aid in sensitivity to texture and ability to grasp, cause finger print patterns. Because of the presence of sweat glands along with these ridges we can identify prints on everything we touch.
Flexion lines (creases): Where skin near joint attached to deeper tissue
freckles: flat, melanized patches, vary with heredity and uv exposure
Mole (nevus): Elevated patch of melanized skin, beauty marks.
Hemangiomas (birthmarks): discolored skin, caused by benign tumors of capillaries.
Hair: is an accessory organ of the skin. It is also known as pilus (singular) and pili (plural)
are made of hard keratin which does not allow for the flake off, making the structure more durable .
hair is produced by hair follicles, which is extended deep into the dermis or even hypodermis.
hair grows on most thin skin (exceptions include: lips, nipples, parts of genitals, and distal segments of fingers.)
the hair matrix contains a single row of actively dividing cells as these cells are pushed farther away from the matrix by the production of new cells the cell starts to die and fill with keratin
the hair shaft is the part of the hair where keratinization is complete located just above the hair root and is the part of the hair that is visible through the skin.
split ends are sometimes seen at the end of the shaft which is essentially the splitting of 3 layers from each other due to the wear and tear our hair undergoes daily.
melanocytes also line the dermal papilla within the hair bulb along the hair matrix the pigment produced is filtered into the cortext and depending on the color of melanin produced will impact your hair color.
as we age melanine production declines and is replaced by air bubbles in our hair shaft resulting in hair that is white or gray in color.
Three types of hair
Downy hair (lanugo): fine, downy, unpigmented hair of fetus.
Vellus hair: is the fine body hair found on adult females and children (unpigmented) (not the eyebrows, eyelashes, or scalp)
Terminal hair: is the darker hair comprising our eyebrows, eyelashes and scalp. After puberty the male sex hormone stimulates further growth of terminal hair on our genital region, underarms (axillary region), male facial hair, chest, sme hair on trunk and limbs.
Hair grows in 4 stages: anagen (growth phase), catagen (follicle shrinks and detaches from hair papilla), telogen( hairs are in this stage at any one time), and exogen (har detached and sheds)
Straight hair is round in cross section
curly hair is flatter
Straight hair is round in cross section
curly hair is flatter
Nails: are made up of hard keratin, derivatives of stratum corneum, composed of very thin, dead, scaly cells with parallel rows of keratin, primates have flat nails.
nails are use to grab onto things, scratch things, and pick up things.
there are 3 major parts to a nail: free edge, nail body, and nail root.
extending onto the nail body is the cuticle. the proximal nail fold and cuticle form a seal to prevent bacteria from entering the nail matrix.
nails get nice pink color due to presence of capillaries in underlying dermis, since nails are transparent the crimson color of the blood shows through, color of nail is used to determine quality of blood circulation. by pressing your nail on your nail plate and then releasing you can watch how quickly the color returns if nail does not return to nice pink color this may be indication of poor circulation.
sebaceous glands: are found all over the body except for the palms of hands and soles of feet. Secrete and oily substance called sebum whose function is to collect dirt and kill bacteria on our skin, coat our skin to impede water loss, and lubricate our hair to prevent it from becoming brittle.
usually opens into a hair follicle
these glands are small on most of our body but are quite large on our face, neck, and upper chest regions.
sebaceous glands: are simple branched alveolar glands, however, functionally they are holocrine as once they accumulate so much sebum they burst expelling their contents onto the skin surface occasionally and hair follicle most often.
Acne is a result of inflammation of a sebaceous gland usually caused by a bacterial infection, result pimples, most often seen on face, can range in size and if left untreated can cause permanent scaring.
sweat glands: Also found widely distributed over the body except for the nipples and external genitalia. There are two types of sweat glands eccrine and apocrine.
Aprocrine: are found in the groin, and region, axilla (armpit), areola (colored region surrounding nipple), and beard.
Ducts open to a hair follicle
It is odorless until it combines with bacteria that feed onto the secretion, in which then it takes on an odor which we call body odor. (bacterial metabolism of those fats cause odor)
respond to stress and sexual stimulation
develop in puberty
believed to secrete pheromones
there are two other specialized apocrine glands:
ceruminous gland: found in auditory canal. Its secretion when mixed with sebum and dead skin cells from neighboring sebaceous glands forms cerumen or what we know as ear wax.
mammary glands: glands develop diring pregnancy and lactation otherwise scant, produce milk, you can have breast but not have mammary glands not synonymous
eccrine or merocrine glands: are the most numerous sweat glands and produce what we know as sweat.
widespread but most abundant in palms of hands, soles of our feet and on our forehead
the sweat that is secreted is 99% water with some salts, vitamins, and metabolic wastes (found in urine).
sweat also contains a microbe-killing peptide to help eliminate potentially harmful microorganisms on the surface of the skin.
Simple ducts leads to pores at the skin surface.
Produce watery perspiration to cool body.
sweating begins on forehead and palms of hands then quickly spreads over entire body
sympathetic nervous system kick starts glands into action
Skin cancer: possible one of the most avoidable types of cancer.
Biggest risk factor of developing skin cancer is exposure to sun’s harmful uv rays (natural) or tanning beds
most common to occur in elderly and fair-skinned people
three types:
Basal cell carcinoma: most common type of skin cancer and least malignant.
slow growing, and easily removed with much success
rarely metastasizes
arises in stratum basale and invades dermis
squamos cell carcinoma: 2nd most common type of skin cancer, arises from the keratinocytes in the stratum spinosum. Grows more rapidly and may metastasize if left untreated.
can metastasize to lymph nodes
skin discoloration becomes more apparent and is an indication of cancerous lesions
if caught in time and removed successfully good chance of complete recovery
can be fatal.
malignant melanoma: cancer of melanocytes. Most deadly, but only in 5% of cases. Arises from melanocytes of existing mole (nevus). Metastasizes quickly and often fatal of not treated quickly.
Risks factors: frequent sun exposure, having lighter skin color, family history, and develops from pre-existing moles.
How to recognize melanoma (ABCDE rule)?
A- asymmetry: examining the sides of the mole and whether they match each other
B- boarder: do the boarders of the mole have any indentations or are they smooth
C- color: does the mole contain a variety of colors (black, brown, tan) or the color uniform.
D- diameter: mole larger than 6mm in diameter.
E- evolution: is the mole changing over time.
Burns: is caused by excessive heat, electricity, or certain chemicals, all of which cause cell damage and/or death in the affected area.
leading cause of accidental deaths: luid loss leading to dehydration; Infection leading to sepsis; Toxic effects of eschar (dead tissue).
First and second degree burns are partial thickness burns while third degree burns are considered full thickness burns.
First degree burns are the least sever type of burn, only the epidermis is damaged and healing usually occurs within a few days. A sunburn is the most common type of first degree burn. Redness, pain and swelling are common.
Second degree burn, the epidermis as well as the upper part of the dermis is damaged, often the damage destroys the connection between the two layers. along with localized pain, redness, and swelling, blisters also form (important not to pop blisters as you don’t want to introduce unnecessary bacteria into an already compromised skin wound). May damage hair follicles, nerve endings, and cutaneous glands.healing usually takes longer with a second degree burn approximately 3-4 weeks. Example sever sunburns and scalds
Third degree burns: most sever burn, the burn consumes the entirety of the skin (epidermis and dermis) and possibly the hypodermis and underlying muscle tissue. Bones, muscles, tendons maybe affected. the burned area often looks white, bright red, or blackend and little swelling. Contracture and disfigurement can result in scarring. These burns are often dry and painless due to glands and nerve endings being destroyed. Individuals with third degree burns run risk of infection and fluid loss could lead to sever dehydration. A skin graft is needed in order to stimulate healing.
aging
hair turns grayer thinner
melanocytes stem cells die out
mitosis slows down
dead hairs not replaced
atrophy of sebaceous glands (dryer skin)
skin becomes thinner and more translucent
fewer and more fragile vessels (if blood supply bad there not going to be able to sustain hair on legs)
rosacea: dilated blood vessels that cause reddened areas
increased bruising
thermoregulation: vulnerability to hypothermia and heat stroke
Some disorder of the integumentary system:
acne
dermatitis
eczema
psoriasis
ringworm
rosacea
warts