a&p - integumentary system (chapter 3 - exam 1)

integumentary system consists of:

• skin (integument)

• subcutaneous layer

• accessory structures (hair, nails, sweat glands)

functions of integumentary system

• body’s first defense

• vitamin d synthesis

• sensation

• thermoregulation

what is the integumentum (skin) composed of?

epithelial and connective tissues

epidermis (epithelial)

top layer of skin (mostly dead cells)

dermis (connective)

contains vessels, nerves, and more flexible

middle layer of skin

hypodermis

bottom layer of skin

subcutaneous layer

made up of

• areolar connective tissue

• adipose connective tissue (contains lots)

functions of subcutaneous layer

• anchors skin to underlying tissues

• stores fat/energy

• cushions the body

thermoregulation

adipose tissue acts as insulation

• slows the movement of heat from the body to the environment

structure of epidermis

stratified squamous epithelium (provides physical protection)

• 4 layers = thin skin (most of body)

• 5 layers = thick skin (palms/soles of feet)

what is the epidermis composed of?

keratinocytes (protein that protects)

• avascular (receives nutrients from the dermis)

dendritic cells

protection from infection (first line of defense)

five layers of the epidermis (BSGLC)

• stratum basale

• stratum spinosum

• stratum granulosum

• stratum lucidum

• stratum corneum

stratum basale

deepest layer

• stem cells (constantly divide to make new keratinocytes)

• keratinocytes

• melanocytes

• merkel cells

stratum spinosum

2nd deepest layer

• 8-10 layers of keratinocytes (alive cells)

• contains desmosomes spiny layer (cells beginning to dry out = crenated)

stratum granulosom

3rd deepest layer

• keratinocytes begin to die as they move toward the surface

• important layer for creating the water-resistant barrier

stratum lucidum

only in thick skin

• clear layer

stratum corneum

top layer (15-30 layers)

• dead cells that are making a layer just for protection

  • being worn away constantly

how long is the life cycle from base to surface for new skin?

40 days

where are new cells produced?

stratum basale

why is keratin important?

strong protein that

• protects the skin

• makes the skin more resistant to damage

• helps prevent water loss

4 major cells of the epidermis

• keratinocytes

• melanocytes

• dendritic cells

• merkel cells

keratinocytes

most common epidermal cell

• produces keratin

• form the protective barrier of the skin

melanocytes

produces melanin (primarily located in stratum basale)

• gives skin its color

• helps protect DNA from UV radiation

dendritic cells

• immune defense

• detect pathogens

• helps activate immune responses

merkel cells (tactile)

located in stratum basale

• associated with sensory nerve endings (light touch)

how many layers does the dermis have?

two layers

• papillary layer

• reticular layer

is the dermis avascular?

no it contains

• blood vessels

• nerves

• sensory receptors

• hair follicles

• glands

papillary layer

superficial layer of the dermis

made up of areolar connective tissue (vascular)

functions of the papillary layer

• provides nutrients to the epidermis (blood vessels)

• helps anchor epidermis to dermis

• contains sensory receptors (dermal papillae)

dermal papillae

• assists in temperature regulation

• nerve endings and touch receptors

• improves grip when wet “prune fingers”

reticular layer

deep layer of dermis

made up of dense irregular connective tissue (collagen and elastic fibers)

functions of reticular layer

• strength

• flexibility

• resistance to stretching

• provides structural support

skin pigmentation

color is produced by two pigments in epidermis

• melanin (black)

  • pheomelanin

  • eumelanin

pheomelanin

yellow-brown (red-head)

eumelanin

brown, black

melanin

produced by melanocytes which are found in the stratum basale

how does melanin protect the skin?

protects skin from UV radiation and reduces cancer risk

• melanin production peaks after 10 days of exposure

why is vitamin D3 and calcium important?

low vitamin D3 and calcium can damage the bone matrix

• cause rickets = in children

• cause osteomalacia = in adults

what does too much melanin cause?

block vitamin D3 absorption (block good UV rays and bad)

lines of cleavage

collagen and elastic fibers in the dermis are arranged in patterns

• parallel incision —> heals with less scarring

• perpendicular incision —> more scarring

stretch marks

occur when the skin stretches faster than the connective tissue can accommodate

sensory receptor

detects a stimulus, meaning a change in the environment

free nerve endings

dermal papillae

• senses pain (nociception)

nociception

sense of pain

merkel cells

located at epidermal-dermal junction

• sense of touch (slow - continue responding to a stimulus)

meissner’s corpuscles

dermal papillae

• sense of touch (fast - quick but reduce signaling when stimulus remains constant)

pacinian corpuscles

dermis

• vibration + pressure (fast)

adaptation

occurs when the nervous system reduces it response to a stimulus that remains constant

example of adaptation

sitting in a lecture and eventually zone out because your brain becomes less responsive to the constant stimulus

phasic receptors

fast adaptation (respond quickly to changes but don’t continue signaling strongly over time)

• example: temperature, smell

tonic receptors

slow adaptation (continue responding longer to a stimulus)

• example: pain, merkel cells

somatic (things you are able to feel) senses

• touch

• temperature

• pain

• itch

• proprioception (body awareness)

5 special senses

• olfaction (smell)

• gustation (taste)

• vision (sight)

• equilibrium (balance)

• hearing (sound)

chemoreceptor

detects chemicals

nociceptor

detects pain/damaging stimuli

thermoreceptor

detects temperature

mechanoreceptor

detects pressure, movement, and tension

photoreceptor

detects light

exteroceptors

detect stimuli outside the body

interoceptors

detect stimuli inside the body

proprioceptors

detect

• body position

• body movement

example of proprioceptors

knowing where your leg is while running without looking at it

receptive field

the area monitored by a particular sensory receptor/neuron

small receptive field

more accurate = can determine exactly where you were touch

• example: your hand

large receptive field

harder to determine exactly where you were touched

• example: your back