Chapter 5- Integumentary System Flashcards
What are the two layers of the skin
- Epidermis
2. Dermis
Epidermis
unvascularized outermost portion of the skin, gets nutrients from diffusion from blood vessels in the dermis
What type of tissue makes up the epidermis
Stratified squamous epithelial tissue
Dermis
Vascularized, has nervous supply, makes up most of integument by mass
What type of tissue makes up the dermis
dense connective tissue
Hypodermis
Composed mostly of adipose tissue. Located below the dermis but superficial to the tough connective tissue wrapping (fascia) of the skeletal muscles
Functions of the hypodermis (4)
- Storage- easy to access energy source for the body
- Protection/shock absorption- prevents physical trauma to internal organs
- Insulation- prevents excessive heat loss
- Anchor- holds skin to underlying skeletal muscle tissue- is still flexible
Keratinocytes
produce keratin, the fibrous protein that helps give the epidermis its protective properties
How are keratinocytes linked
Linked by desmosomes (with some tight junctions) to hinder movement of water between cells
How do keratinocytes reproduce
Reproduce mitotically in stratum basale in response to epidermal growth factor, and from the bottom up- keratinocytes are dead once they approach the skin surface
Persistent friction to the epidermis causes
callus formation, a thickening of the epidermis to prevent excessive skin cell loss. Millions of cells are lost each day- you get a new epidermis every 25-45 days
Keratinocyte function
give the epidermis its protective qualities (tough and dry)
Where are melanocytes located in the epidermis
stratum basale
Melanosomes
Melanin producing organelle in the melanocytes
What happens to melanin after it’s produced by the melanosomes
Melanin is transferred to the keratinocytes and migrates to the superficial side of the keratinocyte to form a pigment shield that protects the nucleus and the nuclear DNA from the damaging effects of UV light. Melanin does not remain in the melanocytes
Dendritic cells (Langerhans cells)
Move to epidermis from bone marrow
Active macrophages- this activates the immune system
Located in the epidermis
Tactile cells (Merkel cells)
Present in epidermal-dermal junction
Associated with sensory nerve endings, resulting in sensory receptor function for 2 types of touch
What types of touch are detected by the tactile cells (2)
- Light touch
2. Vibration
What types of cells are located in the epidermis (4)
- Keratinocytes
- Melanocytes
- Dendritic cells
- Tactile cells
Layers of the epidermis (5)
- Stratum basale
- Stratum spinosum
- Stratum granulosum
- Stratum lucidum
- Stratum corneum
Stratum basale
innermost/deepest epidermal layer
Single layer of stem cells attached to dermis- the many mitotic nuclei in this layer suggests rapid cell division
Cell composition of the stratum basale
Mostly keratinocytes, 10-25% of cells are melanocytes
What happens in the stratum basale when cells divide
Reproduces from the bottom up. When cells divide, When cells divide, one daughter cell is pushed into the cell layer above to begin to specialize into a mature keratinocyte. The other remains in the stratum basale to make sure the layer is replenished
Stratum spinosum
Second deepest (spiny layer) due to spiny extensions of its keratinocytes, several cell layers thick. Contains pre-keratin- thick bundles of filaments that resist tension are are anchored to the desmosomes
Cell composition of the stratum spinosum
Dendritic cells are most abundant here
Stratum granulosum
Third deepest granular layer. Keratinization begins at this layer, has an
accumulation of two granule types (keratohyline and Lammelar granules). Cells here are especially tough and water resistant due to proteins within the keratinocytes and lipids deposited outside them
Keratohyline
One of the granule types that accumulates in the stratum granulosum, helps with formation of keratin in the upper layers of the epidermis
Lammelar granules
One of the granule types that accumulates in the stratum granulosum, ontains water resistant glyco-lipid that’s secreted into the extracellular space, the glycolipid plays a major part in slowing water loss across the epidermis along with tight junctions
Stratum lucidum
Fourth deepest layer. Relatively transparent, not found in thin skin. The cells in this layer are dead.
Stratum corneum
Most superficial “horny layer”, makes up most of the epidermis. These cells are dead.
Glycolipids between cells waterproof layer
Keratin inside cells protects from friction/abrasion and prevents huge amount of skin from being lost at once
These cells are shed regularly as dandruff or flakes from dry skin
Dermis
The “hide” of the body, makes up the bulk of the integument
Strong and flexible connective tissue with a semifluid matrix that is embedded with fibers and binds the entire body together
Fibroblasts and macrophages dominate here
It has 2 layers
What are the 2 layers of the dermis?
- Papillary dermis
2. Reticular dermis
Papillary dermis
Thin areolar connective tissue, fibers are thin- defensive cells wander freely here. Has projections called dermal papillae
Dermal papillae
Projections on the papillary dermis- increases the surface area of the dermis so the epidermis can be better attached to the dermis. Also, the amount of nutrients and oxygen passed on to the epidermis will increase
Can have either pain receptors or tactile corpuscles
The dermal papillae attach to the dermis, pulling it in, so the indents overlying the epidermis forms friction ridges
Fingerprints
Formed by the dermal papillae. Genetically determined feature- identical twins also have different fingerprints due to a combination of factors. These increase your sense of touch and help with grip
Reticular dermis
Lies deep to papillary dermis, dense irregular connective tissue, makes up 80% of dermal mass
Collagen and elastic fibers give the skin strength, resiliency, and stretch and recoil properties. Forms cleavage lines in the skin and flexure lines at/near joints
Cleavage lines
Formed by the reticular dermis. Not visible externally, lines are formed by alternating dense and less dense regions of fibers.
Very important for surgeons. The direction of the cleavage line determines the type of incision. Cutting perpendicular to the cleavage line will cause the fibers to snap and create a gaping hole- infection risk and makes sutures more difficult
Flexure lines
Formed by the reticular dermis. Dermis is tightly anchored here- does not move as easily.
It is forced to fold, forming creases that are externally visible (the lines on fingers and the palm). This gives the skin flexibility. These lines are found at the bottoms of feet, back of knees, front of elbow, fingers, palms
What is a blister?
A fluid filled pocket separating the epidermis and the dermis, caused by short term but acute trauma (like a burn or repeated friction)
Striae
Stretch marks. Extreme stretching of the skin, like during pregnancy, can tear the dermis and leave white scars called striae
What 3 factors help determine skin color?
- Melanin
- Carotene
- Hemoglobin
Melanin
polymer that comes in 2 forms: reddish yellow and brownish black. Skin color is dependent on the amount of melanin produced- the cells in the other 2 layers of the skin are composed of dead cells and don’t need to be protected, so they don’t get melanin. More melanin production= darker skin
Which enzyme synthesizes melanin?
tyrosinase
How does skin get darker?
Exposure to sun- DNA is damaged in the sun, repair is the first “signal” to produce melanin.
Keratinocytes release chemical to “activate” melanocytes
This defensive response causes tanning in individuals without very dark skin
Carotene
yellow orange pigment
Accumulates in stratum corneum and adipose tissue
Can be used by body to produce vitamin A- used for vision, epidermal health, also found in certain plant products (carrots)
Hemoglobin
pink/red pigment
Also found in red blood cells- red when bound to oxygen
Usually only seen in fair skinned individuals- pale skin results when blood moves away from the skin
Oxygenated pigment- color comes from blood supply to dermis (light skin is transparent so the color comes through).
How does a melanin buildup protect the DNA of skin cells?
A melanin buildup helps protect the DNA of skin cells from UV radiation by absorbing the rays and dissipating energy as heat
Jaundice
The liver is not pulling a waste component out of the blood, so it builds up. The blood supply to the skin causes it to turn yellow
Albinism/melanism
Caused by genetic mutations
Albino people don’t produce melanin- very fair skinned and very light (even white) hair, eyes can be red
Melanistic individuals produce large amounts of melanin- dark hair, skin, and eyes
Cyanosis
Blue skin/lips/mucous membranes resulting from a problem in circulation. Hemoglobin isn’t properly saturated or a part of the body isn’t getting blood flow
Cyanotic doesn’t equal necrotic
Argyria
Skin turns bluish if you ingest large amounts of silver over a long period of time. Can eventually turn eyes and nails blue permanently as well as the skin
Skin appendages
Skin appendages are epidermal derivatives (derived from epidermal cells) that extend into the dermis. They include hair and hair follicles, nails, sweat glands, and sebaceous glands.
Hair functions (2)
- Sensory structures: nerves associated with hair follicle
- Protection- scalp (from the sun), eyes (from dirt/debris), nose (hairs trap dirt and debris and prevent it from entering the lungs)
Hair root
part of hair embedded in skin
Hair shaft
part of hair projecting out of skin
What does hair consist of?
Consist of dead, hard keratinized cells- uses a different type of keratin than skin to make it really tough
What are the 3 layers of the hair
- Medulla
- Cortex
- Cuticle
Medulla
central core composed of large cells and air space. Absent in fine hairs of the body (vellus hairs)
Cortex
several layers of flattened cells- less air space, cells are tightly packed together
Cuticle
outermost layer that is most heavily keratinized, cells stacked like roof shingles. Separates individual hairs to prevent mats. Hair conditioners smooth out the rough surface of the cuticle and make hair look shiny
Hair follicle
The structure that hair grows from, results from fold extending from epidermal surface into dermis
What are the 3 layers of the hair follicle?
- Peripheral sheath
- Glassy membrane
- Root sheath
Peripheral sheath
most external layer composed of dermis. Like a follicle wall.
Glassy membrane
“basement membrane” joining the peripheral sheath to the root sheath
Root sheath
most internal layer derived from epidermis. Surrounds and protects the growing hair so cells can be added.
Root hair plexus
found at base (hair bulb). Contains nerve endings, detects when the hair bends/moves
Which structure provides capillaries to the hair follicle?
Dermal papilla- necessary to have blood supply to grow hair
Arrector pili
smooth muscle cells. Contraction pulls hair follicles upright. These muscles cause goosebumps. Attached to peripheral sheath.
Very important for body defense in non-human animals. Doesn’t work for humans because we don’t have enough body hair
What determines hair shape?
Shape is dependent on hair follicle: round= straight hair, oval= wavy/slightly curly, flattened= very curly
What determines hair color?
Color depends on melanin deposition to hair cortex
Heavy deposition to the cortex= darker hair
Gray/white hair results as melanin production decreases with age. The cortex fills with air bubbles instead
Exception- red hair results from pheomelanin
Hair matrix
composed of rapidly dividing cells from hair bulb, involved in hair growth
How does hair growth occur?
New cells push old cells up and out to become the hair shaft- hair growth
Most growth is cyclical- when hair is in the dormant stage it won’t actually grow/cells won’t divide. The hair could also shed.
Not all follicles are in the same stage at the same time
Vellus hair
thin/fine, pale, describes the body hair of children and adult females
Terminal hair
thick/coarse, typically darker in color, found in the eyebrows, eyelashes, and scalp.
At puberty, terminal hairs appear in the axillary and pubic regions of both sexes and typically the face, chest, arms, and legs of males. These hairs grow in response to androgens- the male sex hormones. Testosterone is most important)
Hair thinning
Hair thinning is experienced by most people at older ages- hair loss exceeds hair replacement around age 40
Pattern baldness
True baldness is usually gender influenced and genetically determined. Hair follicles respond to androgen hormones differently with time- hairs become vellus, many are shed before emerging from the follicle, and hair follicles at the top of the head tend to respond to androgens differently than hair follicles on the side. This is an X linked condition- hair growth is tied to the X chromosome, people with XY chromosomes don’t have competing hair growth gene to cancel out the mutation causing pattern baldness
Hirsutism
when women develop coarse terminal hairs in a masculine distribution. Sometimes no problem is found, but sometimes it can indicate a medical issue (polycystic ovarian syndrome- the ovaries secrete larger amounts of androgens)
Telogen effluvium
hair loss for no apparent reason- maybe poor diet or chronic stress or a shock to the system such as surgery or the hormonal changes after childbirth
3 types of alopecia
- Alopecia areata- hair loss in patches especially on the scalp
- Alopecia totalis- complete loss of hair on the scalp (and only the scalp)
- Alopecia universalis- complete loss of hair on the scalp and the rest of the body. Can take shots that help to stimulate the follicles
What substance do nails contain?
Hard keratin
3 components of a nail
- Proximal root- underneath the skin, can’t be seen externally, covered by nail matrix- cells divide rapidly
- Nail plate- part that can be seen externally
- Free edge- most terminal portion of the nail not attached to the skin
Nails function
protect the fingertips, dexterity
Why do nails appear pink?
Nails appear pink because of the bed of capillaries in the underlying dermis
The region that lies over the thick nail matrix appears as a white crescent (called the lunule)
Sweat glands
Distributed over the entire skin surface except the nipples and parts of the external genitalia
Sweating is regulated by a branch of the autonomic (involuntary) nervous system
Gland cells are myoepithelial cells
Myoepithelial cells
The type of cells found in sweat glands, specialized cells that contract when stimulated to push secretion to the surface of the skin
What are the 2 types of sweat glands
- Eccrine
2. Apocrine
Where do sweat components come from?
Secretory cells pull sweat components from blood. Mostly water, but also contain salts, metabolic wastes, etc.
Where you begin to sweat depends on
Where you begin to sweat depends on the circumstance
Can include sweating when nervous/lying- axillary areas, palms of the hands, and upper lip
Eccrine sweat glands
More numerous
Simple tubular glands that open to surface at a pore
Sweat is mostly water, tends to have a high salt content
Where are eccrine sweat glands found?
especially abundant on palms, soles of feet, forehead
Eccrine sweat glands function
body temperature regulation- heat induced sweating begins on the forehead and spreads inferiorly over the remainder of the body
Emotionally induced sweating (nervousness or fright) begins on the palms, soles, and axillae.
Apocrine sweat glands
Larger than eccrine glands
Empty into hair follicles, then released to skin
Same components as sweat from eccrine, plus fatty substances and proteins. It is odorless, but creates an odor when its organic molecules are decomposed by the bacteria on the skin
Where are apocrine sweat glands found?
located in axillary and anogenital areas, function after puberty.
What is the function of apocrine sweat glands?
Function is unclear- could be pheromones as they only function after puberty
Ceruminous glands
A modified version of apocrine sweat glands, produce cerumen (earwax) only found in the external ear canal
Mammary glands
A modified version of apocrine sweat glands, everyone has them, only active in pregnant or breastfeeding individuals
Sebaceous glands
Secretes sebum (oily substance). Simple branched alveolar glands. Sebum is largely lipid based with cell components. Release to skin is dependent on arrector pili Empty into hair follicle, released to skin. Functionally, they are holocrine glands- accumulate oily lipids until they burst
Sebaceous glands functions (3)
- Lubricant for skin/hair
- Slows water loss from epidermal surface
- Kills bacteria
Basal cell carcinoma is a cancer of the
Cells in stratum basale proliferate to invade dermis. Mostly found on the face
Squamous cell carcinoma is a cancer of the
Cancer of keratinocytes of stratum spinosum- found mostly on head (not facial area) and hands
What is the most common cause of skin burn?
Sunburn (1st or 2nd degree). Results after exposure to sun without protection by melanin
Inflammatory reaction- painful to touch, redness due to increased blood supply to skin
Severe sunburn can result in fluid filled pouches- protects underlying skin
Damaged topmost layer(s) will die and eventually peel off. Skin underneath is usually tanner.
When the skin peels off you will have a new functional epidermis underneath it that is usually darker in color
What can cause burns?
Caused by intense heat, radiation, chemical etc
1st degree burns
painful, reddened skin, inflammation. No scarring involved in healing
2nd degree burns
pain, redness, fluid filled pouches (blisters). Takes longer to heal than 1st degree burns, no scarring. New epidermis could have discoloration
3rd degree burns
full thickness burns. Treatment usually requires IV fluids, skin grafts, and heavy antibiotic use
When epidermis and dermis are burned away, so are the free nerve endings that sense pain
Most often die from dehydration (constant water loss if you have no skin in most of the body).
Purpose of cerumen
thought to deter insects and block entry of foreign material
Where are sebaceous glands found?
found everywhere except for the thick skin of the palms and soles. They are small on the body trunk and limbs, but larger on the face, neck, and upper chest
Acne
Acne is an active inflammation of the sebaceous glands accompanied by pustules, cysts, whiteheads, or blackheads on the skin.
If accumulated sebum blocks a sebaceous gland duct, it can cause a whitehead (closed comedone) or blackhead (open comedone)
Acne is associated with infection by propionibacterium acne
Skin functions (6)
- Protection
- Temperature regulation
- Sensation
- Metabolic functions
- Reservoir
- Excretory
What types of protection does the skin provide (3)
- Chemical- Sweat and oily secretions kill bacteria, melanin prevents damage caused by UV light
- Physical- skin prevents entrance of bacteria
- Biological- dendritic cells patrol dermis to stop anything that passes through epidermis
Macrophages destroy large sized (invaders)
Insensible perspiration
unnoticeable sweat loss during the day
Sensible perspiration
noticeable sweat loss that occurs when excess heat needs to be lost by the body
How does the skin regulate temperature?
Sweating when hot. When cold, blood vessels in the skin will constrict- pulls blood away from skin and toward internal organs. This allows the body to retain heat
Exteroreceptors
cutaneous sensory receptors
Respond to stimuli arising outside the body
Includes tactile corpuscles, lamellar corpuscles, hair/hair follicles, free nerve endings
How does the skin contribute to sensation?
Using exteroreceptors
How is the skin involved in metabolic function?
Involved in vitamin D production- calcium cannot be absorbed from digestive tract without this vitamin
How does the skin act as a reservoir?
About 5% of total blood volume can be found in integument
Can be “moved” by central nervous system
How does the skin have excretory function?
Sweat allows for some elimination of certain wastes (urea, ammonia, uric acid)
