Chapter 6 - Integumentary System Flashcards
Layers of the Skin
Cutaneous Layers of skin:
- Epidermis: stratified squamous tissue
- Basement membrane achors epidermis to dermis
- Dermis: made up of connective tissue including collagen, elastic fibers, smooth muscle tissue, nervous tissue and blood and lymphatic vessels
Subcutaneous Layers: not part of skin
- Hypodermis: composed of areolar and adipose connective tissue which bind skin to underlying organs
No distinct boundary
Layer of Skin: Epidermis
- Lacks blood vessels
○ Cells in stratum basale are nourished by dermal blood vessels- The further cells are pushed away from the basal layer, the poorer their nutrient supply and in time they harden and die; keratinization
○ Cytoplasms fill with strands of tough fibrous waterproof keratin proteins - In healthy skin, production of epidermal cells occurs as frequently as loss of dead cells in stratum corneum occurs
- Rate of cell division will occur faster where skin is rubbed or pressed, as this causes the growth of thickened areas(calluses)
- The further cells are pushed away from the basal layer, the poorer their nutrient supply and in time they harden and die; keratinization
1st Layer of the Epidermis
Stratum Corneum: most superficial layer that has layers of keratinized, dead, flaky and scaly epithelial cells
○ Involved in resisting water loss, absorption, abrasion
2nd Layer of the Epidermis
- Stratum lucidum: only found between stratum corneum and stratum granulosum on soles and palms of thick skin where the cells appear clear
○ 2nd layer in thick skin
3rd Layer of the Epidermis
- Stratum Granulosum: 3-5 layers of flattened granular cells which contain fibers of keratin and shriveled nuclei which is involved in waterproofing and cuts off blood supply
○ 3rd layer in thick skin, 2nd layer in normal skin
4th Layer of the Epidermis
- Stratum Spinosum: found beneath the granulosum where many layers of cells, which become flatter as they get more superficial, with large centrally located nuclei develop fibers of keratin
○ 4th layer in thick skin, 3rd layer in normal skin
5th Layer of the Epidermis
- Stratum Basale: the deepest layer involving a single row of cuboidal or columnar cells which includes melanocytes and frequently divides to send cells into superficial layers.
Cells in the Epidermis
Dendritic/Langerhans cells: phagocytes within stratum spinosum which protect the skin and deeper tissue from pathogen invasion
- Engulf invading microbes within skin, process and display parts of the microbe on their membrane and then migrate to lymphatic tissue to alert other immune cells
Tactile/Merkel cells: oval shaped cells scattered in the stratum basale which correspond to a nerve ending and release chemicals when lightly touched, stimulating the sensory nerve
- Tactile disc is the tactile cell with the sensory nerve ending
Melanocytes: epidermal cells in the stratum basale which produce and store melanin which absorbs UV light in order to protect DNA from mutations in skin cells
- As a result of absorbing UV light it is resposnible for the color of our skin
Types of Melanin to make up skin color
○ Eumelanin: brownish black in the epidermis
- Pheomelanin is the reddish-yellow in certain locations such as lips
Types of Skin Cancers
- Basal cell carcinoma: least malignant where the stratum basale cells proliferate and push down into the dermis
○ 99% cure rate with surgical removal- Squamous cell carcinoma: stratum spinosum cells that divide as they keratinize producing a nodular tumor
○ Sun induced and cure rate is good with surgical removal - Malignant Melanoma: Melanomas arise from melanocytes, usually arising from a preexisting mole which metastasizes to lymph nodes
○ Not always sun induced but often spontaneously
- Squamous cell carcinoma: stratum spinosum cells that divide as they keratinize producing a nodular tumor
Dermal Papillae
- Dermal and epidermal boundary is uneven and causing dermal papillae extend into the dermal spaces between epidermal ridges
- They increase surface area where epidermal cells receive oxygen and nutrients from dermal capillaries
- Most abundant in the hands and feet
- Ridges form a patterned impression; fingerprint
Layers of Dermis
- Papillary layer which is composed of areolar connective tissue
- Reticular layer: composed of dense irregular connective tissue which has lots of tough collagen fibers and elastic fibers, giving skin its toughness
Cells in the Dermis
- Sensory receptors in dermis include:
○ Lamellated corpuscles: reside in the deeper dermis and respond to heavy pressure
○ Tactile corpuscles: reside in the upper dermis and respond to light touch and texture - Sweat Glands
- Hair Follicles
Nails
protective coverings on the ends of fingers and toes
- All of the nail is dead cells except for the lunula, however pain is felt due to it being attached to the bed which is alive
Structure of Nails
- Nail bed is produced from deeper layers of epidermal skin
- Nail plate: visible portion consisting of keratinized cells which overly the nail bed
- Blood vessels under the nail give it a pinkish appearance
- Nail matrix: active growth region not visible and at the proximal end of nail bed
- Lunula is the whitish half-moon region due to the thick nail matrix concealing dermal blood vessels
- Cuticle: a portion of stratum corneum extending over the proximal end of the nail
- Free edge: the nail plate extending beyond the end of the nail bed
Hair Follicles
a tube like depression where epidermal stem cells develop into hair
- Hair cycles through phases of active growth and inactive periods
- 90% of hair at any time is growing
Structure of Hair Follicle
- Hair bulb sits in the base of the follicle
- Hair matrix within the hair bulb contains epithelial cells which allow for division and growth
- Hair papilla: contain blood vessels to nourish the hair and anchor the hair bulb
- hair root extends from the skin surface to the subcutaneous layer
- Hair shaft is composed of keratinized epithelial cells which extend away from skin surface
Alopecia
Baldness occurs when hair sheds and is not replaced which is associated with lower levels of testosterone or estrogen:
Sebaceous Glands
composed of groups of specialized epithelial cells which secrete sebum that is secreted into hair follicles through ducts and helps keep the hairs and skin soft, pliable and waterproof
- Its a holocrine gland meaning it secretes whole cells with fluid
Sweat/Sudoriferous Glands
consist of a tiny tube that originates as a ball shaped coil which is lined with sweat secreting epithelial cells which secrete through pores to the surface
- Sweat is water with small amounts of salts, urea and uric acid
2 Types of Sweat Glands
- Most are merocrine sweat glands which respond to elevated body temperatures, and do not go into hair follicles but release through pores in skin
- Apocrine sweat glands do release into hair follicles and are found in axillary and groin areas
Ceruminous Glands
glands found in the ear canals which secrete cerumen/ear wax which mixes with sebum to make a sticky substance, preventing entry of microbes and foreign substances
Mammary Glands
develops during pregnancy and lactation which secretes milk through a duct to the nipple
Functions of Skin
- Protection: protects against harmful substances, UV radiation, microorganisms and water loss
- Sensation: contains sensory receptors for touch, pressure, temperature change and pain
- Vitamin D synthesis: starts in skin and helps with calcium absorption
- Body temp regulation: helps cool body by sweating and changing blood flow
Function of Skin: Protection
- Keratinization and layering of skin provides a protective barrier against harmful diseases
- Contains dendritic cells which initiate the immune response
- Melanocytes secrete melanin which protects epidermal cells from harmful effects of UV
- Sweat being slightly acidic inhibits growth of microorganisms
- Sebum helps retard water loss
Function of Skin: Sensation
- Skin houses tactile discs which detect touch
- Receptors in hair follicles detect insects crawling, wind blowing or hair pulling
- Othre sensors detect pressure, change in temp and pain
Function of Skin: Vitamin D Production
3 step process which begins in the skin:
- Some skin cells produce dehydrocholesterol(precursor) which when exposed to sunlight changes to an inactive form of vitamin D(cholecalciferol)
- This is then taken to the liver for the 2nd and 3rd steps of making it active
- Vitamin D is necessary for the absorption of calcium from foods
Ways heat is released by the skin
○ Heat is then primary released through radiation where infrared heat rays escape to the cooler surroundings
○ Can also be released through conduction when heat moves from the body to a cooler object or through convection where heat is lost to the cooler air which is taken away and replaced with cooler air again
Thermo receptors take signal to hypothalamus which results in vasodilation of dermal blood vessels and activation of sweat glands
Ways heat is conserved by the skin
- Hypothalamus triggers smooth muscle cells in dermal blood vessels to vasoconstrict and decrease blood flow to the surface, reducing heat loss by radiation, conduction and convection
- Merocrine sweat glands remain inactive
Shivering: Muscle cells may be stimulated to contract forcefully increase cellular respiration
- Merocrine sweat glands remain inactive
Fever
set point in body is elevated by the immune system to fight infection
- Phagocytes release pyrogens in response to presence of bacteria viruses which triggers the hypothalamus to raise body temperature and destroy the pathogens
Inflammation
response to injuries where blood vessels in affected tissues dilate and become permeable, allowing nutrients and oxygen to leak into damaged tissue and aid healing
Epidermal Wounds
- If a break in skin is shallow, epithelial cells are stimulated to divide more rapidly along the border and fill the gap
Dermal Wounds
- Blood vessels will be broken and blood begins to form a clot containing fibrin while tissue fluids seep into the area and begin to dry to form with the fibrin a scab
- Under the scab, epithelial cells proliferate and bridge the wound while fibroblasts migrate into the region and secrete collagen fibers to stitch the edges together
- Blood vessels extend beneath the scab allowing phagocytotic cells to remove debris
- The scab will then fall off
Superficial Partial Thickness(1st degree) burn
burn injuring only the epidermis
- Recovery is a few days to two weeks
- Due to minor sunburns
Deep partial thickness(2nd degree):
burn destroying some epidermis as well as some underlying dermis
- Fluid escapes from damaged dermal capillaries and accumulates under the outer layer of epidermal cells, forming blisters
- Due to exposure to hot objects, liquids, flame or burning clothes
- Full recovery will occur in time unless an infection occurs
Full Thickness(3rd degree)
burn destroying the epidermis, dermis and accessory structures of the skin
- Due to prolonged exposure to hot objects, flames or corrosive chemicals
- Treatment could involve an autograft which involves removing a thin layer of healthy skin from another area and transplanting it into the injured area
- Allograft is needed if extensive damage is done where cadaveric skin is taken from a skin bank and temporarily covers the wound until an autograft can be done
Rule of 9’s for Burns
- Extent of affected body surface in burns is estimated using the rule of nines
- The skin surface region is divided and each region accounts for either 9% or multiples of the total surface area
- Used to estimate replacing body fluid, electrolytes and for covering burned area
Ageing in skin
- Epidermis thins as the decades pass
- As cell cycle slows, they grow larger and more irregular in shape
- Dermis becomes reduced in volume and in function as synthesis of collagen and elastin slows
○ Results in wrinkling and sagging of skin - Wound healing slows due to fewer fibroblasts
Ageing in skin accessory structures
- Slowed melanin production whitens hair as the hair shafts become more transparent
- Hair growth slows, thins and number of follicles decrease
- Sensitivity to pain and pressure diminishes as sensory receptors reduce in quantity
- Due to older people not getting outdoors as much, less vitamin D is formed resulting in weaker bones
- Sweat glands fall reducing the ability to cool themselves down
- Hair follicles shrink resulting in a decreased ability to shiver
