Human Anatomy Exam #1

Outermost layer of skin

epidermis

what is the epidermis made of

keratinized stratified squamous epithelium

4 major epidermal cell types

1. Keratinocytes

2. Melanocytes

3. Dendritic Cells (Langerhan cells)

4. Merkel Cells

most abundant epidermal cells (approx. 90%)

keratinocytes

these cells produce keratin

keratinocytes

tough structural protein that helps protect the skin

keratin

this cell type forms a physical barrier against abrasion, pathogens, and water loss

keratinocytes

these type of cells begin near the basal layer and move toward the surface as they mature

keratinocytes

these cells produce melanin

melanocytes

this is the pigment that contributes to skin and hair color

melanin

where are melanocytes primarily located

stratum basale

these cells transfer melanin-containing melanosomes to keratinocytes

melanocytes

this pigment helps protect the DNA of skin cells from UV radiation

melanin

these are immune defense cells

dendritic cells

these cells are found primarily in stratum spinosum

dendritic cells

these cells detect foreign substances and help activate immune responses

dendritic cells

these cells act as an antigen presenting cell, helping other immune cells recognize threats

dendritic cells

these cells are located in the stratum basale

merkel cells

these cells are associated with sensory nerve endings

merkel cells

these cells help detect light touch and fine details, such as texture

merkel cells

This is the process by which epidermal cells accumulate keratin, flatten, lose their nuclei and organelles, and become part of the protective surface

keratinization

5 epidermal strata (deepest to most superficial)

1. stratum basale

2. stratum spinosum

3. stratum granulosum

4. stratum lucidum

5. stratum corneum

single row of cells along the basement membrane

stratum basale

stems cells divide here and new keratinocytes are produced

stratum basale

several rows; cells appear spiny under a microscope

stratum spinosum

cells in these region develop stronger connections through desmosomes and produce keratin

stratum spinosum

this layer has flattened cells with visible granules

stratum granulosum

this is the layer where keratinization intensifies, cells release lipids that help form a water barrier and begin to die

stratum granulosum

thin, clear layer found only in thick skin

stratum lucidum

dead, flattened cells in this layer form an additional protective layer

stratum lucidum

this layer has many layers of flattened, dead, keratin-filled cells

stratum corneum

cells in this layer form the outer protective barrier and eventually shed

stratum corneum

the shedding of dead cells from the stratum corneum

desquamation

what happens to the epidermal cells as they move toward the surface

change in appearance due to maturation, accumulation of keratin, lipid release, flattening, and eventual cell death

found on the palms and soles. contains all 5 strata and particularly thick stratum corneum

thick skin

found over most of the body. lacks a distinct stratum lucidum and is generally associated with hair follicles and sebaceous glands

thin skin

what replaces epidermal cells lost at the surface

basal cell division

does skin have the same thickness and structures everywhere

no, its thickness, pigmentation, hair follicles, glands, and sensitivity vary by location

which structures does thick skin lack

hair follicles and sebaceous glands (does have sweat glands)

eyelid skin type

thin

fingertips skin type

thick skin (many sensory receptors)

scalp skin type

thin skin

does skin heal the same way everywhere

no, healing depends on the depth and size of the injury, blood supply, infection, age, and other factors

how do superficial injuries heal

little to no scarring (epidermis regenerates)

how deep skin injuries heal

produce scar tissue, heal slower, may require skin grafting

why the epidermis is dependent on the dermis for nourishment

epidermis is avascular, the dermis is vascularized and supplies the epidermis by diffusion

structural protein that strengthens the epidermis and helps reduce water loss

keratin

a yellow-orange pigment obtained from the diet that can accumulate in the stratum corneum and subcutaneous fat

carotene

This is the oxygen carrying protein in RBCs (blood color and oxygenation contribute to pink or reddish skin tones)

hemoglobin

why skin color varies

amount, type, distribution and breakdown of melanin

are melanocyte numbers different across human populations

no

are melanin production and melanosome characteristics different across populations

yes

brown-black pigment that provides UV protection

eumelanin

yellow-red pigment that generally provides less UV protection than eumelanin

pheomelanin

other factors that influence skin color:

1. exposure to sunlight

2. genetics

3. blood flow and oxygenation

4. carotene

connective tissue beneath the epidermis. provides structural strength, elasticity, nourishment, and sensory support

dermis

2 layers of the dermis

1. papillary layer

2. reticular layer

superficial, thin layer of the dermis

papillary layer

this part of the dermis is made of loose areolar connective tissue

papillary layer

this part of the dermis contains capillary loops and sensory nerve endings

papillary layer

this layer of the dermis forms dermal papillae that interlock with the epidermis

papillary layer

deeper and thicker layer of the dermis

reticular layer

this layer of the dermis is made mainly of dense irregular connective tissue

reticular layer

this layer of the dermis contains abundant collagen and elastic fibers

reticular layer

this layer of the dermis houses most hair follicles, sebaceous glands, sweat glands, larger blood vessels, and nerves

reticular layer

these fibers resist stretching and provide tensile strength

collagen

these fibers allow skin to stretch and recoil

elastic fibers

these are in the dermis and produce and support hair

hair follicles

in the dermis, small smooth muscles attached to hair follicles. contraction raises hair, producing goosebumps

arrector pili muscles

these are in the dermis, secrete sebum (lubricates and helps protect skin and hair)

sebaceous glands

these are in the dermis, they produce sweat for thermoregulation and other functions

sweat glands

in the dermis, supply nutrients to the dermis and help regulate the body temp

blood vessels

in the dermis, detect touch, pressure, vibration, temperature, and pain

sensory receptors

the boundary between the epidermis and dermis. (includes basement membrane and the interlocking contours of epidermal ridges and dermal papillae)

Dermal-epidermal junction (DEJ)

4 functions of Dermal-epidermal junction

1. anchor epidermis to dermis

2. large SA for attachment

3. resist shearing forces

4. allows nutrients to diffuse from dermal capillaries toward the epidermis

appearance of Dermal-epidermal junction under microscope

wavy (because of the interlocking ridges and papillae)

damage to the DEJ can cause the epidermis to separate from the dermis resulting in

blistering disorders and injuries

why are skin and nails called skin appendages

they develop from the epidermis and are associated with the integumentary system

main protein in hair

keratin

main protein in nails

keratin

functions of hair

protection, sensation, insulation

functions of nails

protect fingertips and toes, assist in grasping and fine manipulation

visible structure on hair

hair shaft

visible structure on nails

nail plate

living part of hair

matrix cells

living part of nails

matrix cells

dead part of hair

shaft

dead part of nail

nail plate

visible, hard part of the nail

nail plate

tissue beneath the nail plate

nail bed

growth region responsible for producing the nail plate

nail matrix

pale crescent near the nail base, where the matrix may be visible

lunula

tissue overlapping the proximal nail plate

eponychium (cuticle)

how does the nail plate grow

as cells produced in the matrix become keratinized, they are pushed forward

3 types of hair

1. lanugo

2. vellus

3. terminal

fine hair that develops on the fetus and is generally shed before or shortly after birth

lanugo

fine, short hair covering much of the body

vellus hair

coarser, usually more pigmented hair found on the scalp, eyebrows, and eyelashes, and developing in certain regions during puberty

terminal hair

part of hair extending above the skin surface

shaft

portion of the hair embedded in the skin

root