Anatomy- Chp 4

skin

• most visible and largest organ system

• protection from environment

• synthesize D3

• thermoregulation

• excretes some waste products

• lipid storage

• immune response

• sense stimuli: temperature, pressure, touch, pain

epidermis

cell types

1. keratinocytes

2. melanocytes

3. merkel cells

4. langerhans cells

keratinocytes

• most common epidermal cell

• produce keratin

• somewhat waterproof

melanocytes

• pigment cells

• produce melanin

• in stratum basale

• among stem cells

merkel cells

• sensory cells

• touch

• among stratum basale and stem cells

langerhans cells

wandering macrophages; in the epidermis and dermis

thin skin

• thinner stratum corneum

• can be transformed into thick skin under certain mechanical stress

• 4 primary layers (no stratum lucidum)

thick skin

• palms of hands

• soles of feet

• thicker stratum corneum

• 5 primary layers (contains stratum lucidum)

epidermal layers of skin (top → bottom)

1. stratum corneum

2. stratum lucidum

3. stratum granulosum

4. stratum spinosum

5. stratum basale

stratum corneum

• contains multiple layers of flattened, dead, interlocking keratinocytes

• typically is relatively dry

• water resistant but not waterproof

• permits slow water loss by insensible perspiration

• contains melanocytes, merkel cells, and macrophages

stratum lucidum

appears as a glassy layer in thick skin only

stratum granulosum

• keratinocytes produce keratohyalin and keratin

• keratin fibers develop as cells become thinner and flatter

• gradually, the cell membrane thicken, the organelles disintegrate, and the cells die

• 2-3 cell layers thick

stratum spinosum

• keratinocytes are bound together by maculae adherens attached to tonofibrils of the cytoskeleton

• some keratinocytes divide in this layer

• langerhans cells and melanocytes are often present

• 4-6 cell layers thick

stratum basale

• is the deepest, basal layer

• attachment to basal lamina

• contains epidermal basal (stem) cells, melanocytes, and merkel cells

• 1 cell layer thick

• high rates of cell division

• loose connective tissue

epidermal ridges

• formed by dermal papillae

• unique; even between identical twins

skin colors

• thickness of stratum corneum; thick skin is lighter

• dermal blood supply: blushing, overheating (red color hemoglobin); pallor (anemia, drop in BP); bruise (hematoma in skin)

• carotene: yellow-orange; dietary (can be converted into vitamin A)

• melanin: brown, yellow-brown, black

• UV radiation (needed for vitamin D synthesis, can damage cells)

• tanning: exposure to UV will increases melanin production- 10 days

• melanin sheilds nuclei from UV

• freckles: aggregations of melanin

• excessive UV (sunburn, skin cancer, damage to fibrocytes)

  • premature wrinkling

  • abnormal connective tissue; “leathery skin”

dermis

1. papillary layer

2. reticular layer

reticular layer of dermis

• dense irregular connective tissue

• hair follicles

• sweat glands

• sebaceous glands

papillary layer

• loose connective tissue

• dermal papillae

• capillaries

• axons of neurons

• attachment to epidermis

cutaneous membrane

• epidermis

• dermis

  • papillary layer

  • reticular layer

accessory structures of integumentary

• hair follicles

• exocrine glands

• nails

epidermis

• protects dermis from trauma, chemicals

• controls skin permeability, and prevents water loss

• prevents entry of pathogens

• synthesizes vitamin D3

• sensory receptors detect touch, pressure, pain, and temperature

papillary layer of dermis

nourishes and supports epidermis

reticular layer of dermis

• restricts spread of pathogens penetrating epidermis

• stores lipids

• attaches skin to deeper tissues

• sensory receptors detect touch, pressure, pain, vibration, and temperature

• blood vessels assist in thermoregulation

hair follicles

• produces hairs that protect skull

• produce hairs that provide delicate touch sensations on general body surface

exocrine glands

• assist in thermoregulation

• excrete waste

• lubricate epidermis

nails

protect and support tips of fingers and toes

integument

skin (cutaneous membrane) + hair, glands, nails (accessory structures)

functions of integumentary system

protection, temperature regulation, excretion, secretion, vitamin synthesis, sensation, immunity

components of integumentary system

cutaneous membrane, subcutaneous layer, accessory structures, and tissues

cutaneous membrane

epidermis (epithelium) + dermis (connective tissue)

subcutaneous layer

also called the hypodermis; loose connective tissue, not technically part of the integument, but closely associated

accessory structures of integument

hair, nails, exocrine glands (in dermis, protruding through epidermis)

tissues in integument

epithelium, connective, muscle, nervous

tissue of epidermis

stratified squamous epithelium

cell types of epithelium

keratinocytes, melanocytes, merkel cells, langerhans cells

keratinocytes

most numerous cell type in epidermis, produce keratin

melanocytes

produce melanin (pigment); skin color varies due to activity of this cell, no the number of this cell

merkel cells

sensory (touch) cell

langerhans cells

immune response (phagocytic)

layers of skin; deep to superficial

1. stratum basale

2. stratum spinosum

3. stratum granulosum

4. stratum lucidum

5. stratum corneum

stratum basale

deepest, attached to basal lamina. contains basal (stem) cells, melanocytes, merkel cells. mitosis occurs here.

stratum spinosum

several cells thick. keratinocytes with tonofibrils (desmosomes). langerhans cells present.

stratum granulosum

keratohyalin and keratin production. lipid-rich secretion leads to cell death in superficial layers.

stratum lucidum

only in thick skin. clear layer, flattened dead cells filled with keratin.

stratum corneum

most superficial. many layers of dead, keratinized cells. water-resistant, not waterproof. insensible perspiration occurs here.

thick v. thin skin

refers to epidermis thickness. thick skin (5 layers) on palms/toes; thin skin (4 layers- no stratum lucidum) elsewhere.

tissue type of dermis

connective tissue

layers of dermis

papillary layer, reticular layer

papillary layer

superficial, loose connective tissues. dermal papillae interlock with epidermal ridges. contains capillaries, sensory neuron axons.

reticular layer

deep, dense irregular connective tissue. contains blood vessels, hair follicles, nerves, glands. collagen and elastic fibers provide strength and elasticity.

tension lines

also called cleavage lines; orientation of collagen bundles. important for surgical incisions.

other components of dermis

connective tissue cells, fibers, accessory structures, blood vessels (cutaneous and sub-papillary plexus), lymph vessels, nerves.

clinical note; dermis

skin cancer types (basal cell carcinoma, squamous cell carcinoma, malignant melanoma)

tissue type of hypodermis

loose connective tissue with adipocytes

function of hypodermis

stabilizes skin position, energy reserve, insulation, shock absoprtion

hypodermis

also called subcutaneous layer; not technically part of the integument, target for subcutaneous injections

hair production structures

hair pailla, hair bulb, hair matrix (where hair production occurs)

structure of hair follicles/hair

medulla (soft keratin), cortex (hard keratin), cutcile

follicle structure

internal/external root sheath, glassy membrane

functions of hair follicles/hair

protection, insulation, sensation (root hair plexus)

arrector pilli muscle

causes “goosebumps”

types of hair

lanugo (fetal), vellus (peach fuzz), terminal (head, eyebrows)

hair color

based on melanin (density and type)

growth cycle of hair

growth phase, club hair phase (follicle inactive)

sebaceous (oil) glands

holocrine secretion of sebum

structure of nails

nail body, nail bed, nail root, eponychium (cuticle), lunula, hyponcyhium

functions of nails

protects tips of fingers/toes

local control and repair of integument

responds directly to local environment changes (ex: callus formation); scar tissue formation (dense collagen, fewer vessels/accessory structures)

epidermis

in aging; thins (decreased basal cell activity), increased risk of injury/infection, decreased langerhans cells (reduced immune sensitivity), reduced vitamin D production

melanocytes

in aging; activity declines, increased sensitivity to sun

glandular activity

in aging; decreases (dry, scaly skin, impaired perspiration, risk of overheating)

blood supply

in aging; decreases (reduced heat loss)

hair follicles

in aging; stop functioning/produce thinner hairs, decreased melanocyte activity (gray/white hair)

dermis

in aging; thins, less elastic (sagging, wrinkling)

repair

in aging; slower, recurring infections

cutaneous membrane

• epidermis

• dermis

  • papillary layer

  • reticular layer

tension lines

collagen and elastic fibers in parallel pattern

collagen fibers

provide tensile strength

elastic fibers

allow skin to stretch and recoil

stretch marks

reticular fibers break

• due to pregnancy or weight gain

• skin DN recoil, wrinkles, and creases

hypodermis

• also called the subcutaneous layer

• deep to dermis

• not technically considered part of integument

• helps stabilize integument

• location of hypodermic needles and subcutaneous injections

• adipose tissue

• major blood vessels

hair follicles and hair

found everywhere except palms, soles of feet, sides of fingers and toes, lips, are portions of genetalia (glans penis, clitoris, inner surface of labia majora, labia minora)

parts of hair

• hair shaft

• hair root

• hair follicle

• hair papilla

• hair matrix

hair shaft

nonliving, visible portion of hair

• medulla: soft keratin

• cortex: hard keratin

• cuticle: outer layer

hair root

portion of hair in follicle being formed; anchors hair

hair follicle

organs that form hair

hair papilla

nerve and blood supply; supports matrix

hair matrix

basal cells that divide to become hair

fucntions of hair

• protection from UV light

• insulation

• guards entrance to nose and ears

• when touched, sends signal via root hair plexus

• contraction of arrector pili muscles; goose bumps

vellus hair

most of body; lacks a medulla

terminal hair

head, eyebrows, eyelashes

factors regarding hair color

• more melanin creates darker hair

• decreased production results in gray hair

• white hair: lack of melanin in hair shaft

• influences by: genetics/hormones/environmental factors

hair shape

based on follicle shape

• straight- circle

• wavy- oval/circle

• curly- oval

active stage of hair gorwth

• 2-5 years

• hair grows about 0.33 mm a day

• undergoes regression into the next stage (resting)

resting stage of hair growth

• hair loses its attachment to follicle

• hair becomes a club hair

• reactivation occurs

• club hair is lost and a replacement hair is produced

• pattern baldness; changes in sex hormones

sebaceous galnds

make sebum (lipid mixture)

• lubricate epidermis and hair

• antimicrobial properties

• no glands on palms and soles

• high concentration on forehead, face, and upper back

• if ducts become blocked this can cause acne or furnucles

• holocrine secretion

sebaceous follicles

large sebaceous glands; no hair

eccrine (merocrine) sweat glands

• all over body

• high concentrations on palms and toes

• eccrine secretion

function of sweating

• thermoregulation

• some waste excretion (salts, nitrogen waste, some metabolites)

• antimicrobial activity