integumentary system

the integument is the:

largest organ system

2 parts of integument

cutaneous membrane, accessory structures

2 components of cutaneous membrane

outer epidermis; inner dermis

examples of accessory structures

hair, hair follicles, multicellular exocrine glands (sebaceous and sweat glands), nails

integumentary system is connected to:

cardiovascular system; nervous system

what is not considered part of integumentary system?

hypodermis

hypodermis

located below the dermis; composed of elastic, loose areolar, and adipose tissue; connected to reticular layer by connective tissue fibers; few capillaries and no vital organs; location of subcutaneous injections

five main functions of the skin:

protection, excretion, maintenance, production, detection

Epidermis

avascular stratified squamous epithelium; dominated by keratinocytes

most abundant type of epithelial cells?

keratinocytes

Thin skin

covers most of body; has 4 layers of keratinocytes

Thick skin

covers palm and soles; has 5 layers of keratinocytes

The epidermis layers (from bottom to top)

Stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum

Stratum basale

Many basal/ germinative cells
Attached to basement membranes by hemidesmosomes
Forms strong bonds between epidermis and dermis
Forms epidermal ridges
Dermal papillae

Dermal papillae

projections from the dermis
increase the area of the basement membrane
strengthen the attachment between epidermis and dermis

Basis of fingerprints

epidermal ridges

Specialized cells of stratum basale:

Merkel cells
Melanocytes

Merkel cells

Specialized epithelial tactile cells
Found in hairless skin
Respond to touch (trigger nervous system)

Melanocytes

Contain melanin pigment
Scattered throughout stratum basale

Stratum spinosum "spiny layer"

produced by mitotic division of stratum basale cells
8-10 layers of keratinocytes bound by desmosomes
Cells shrink until cytoskeletons stick out (spiny look)
Continue to divide increasing thickness of epithelium
Contain dendritic (Langerhans) cells that's active in immune response

Stratum Granulosum

cells stop diving
Produce keratin and Keratohyalin
cells dehydrate and die

Keratin (and example)

tough, fibrous protein
Hair and nails

Keratohyalin

protein that forms dense granules; cross-link keratin fibers and dehydrates cells

What happens when keratin accumulates?

cell flatten, plasma membrane thickens, and becomes less permeable

Stratum Lucidum "clear layer"

found only in thick skin
Covers stratum granulosum
Cells are flattened, densely packed with keratin and devoid of organelles

Stratum Corneum "horn layer"

exposed surface
15 to 30 layers of keratinized cells
Water resistant
Shed and replace every two weeks
Undergo keratinization

Keratinization synonym

cornification

keratinization

formation of a layer of dead, protective cells filled with keratin

skin life cycle

takes 7 to 10 days for a cell to move from stratum basale to stratum corneum
Once there, cells remain for an additional 2 weeks before shedding

2 types of perspiration

insensible perspiration, sensible perspiration

Insensible perspiration

interstitial fluid lose by evaporation through stratum corneum

sensible perspiration

water excreted by merocrine sweat glands

dehydration

from damage to stratum corneum
from immersion in hypertonic solution

Hydration

immersion in hypotonic solution
causes swelling of epithelial cells, evident on palms and soles

Skin color influenced by

carotene, melanin, blood circulation

Carotene

orange- yellow pigment
Found orange vegetables
Accumulates in epidermal cells and fatty tissues of dermis
Can be converted to Vitamin A

Carotenemia

overconsumption that can turn skin orangish

Nyctalopia

lack of vitamin A causing night blindness

melanin

Yellow-brown or black pigment
Produced by melanocytes in stratum basale
Stored in melanosomes
Transferred to keratinocytes

Tyrosine

amino acid required to synthesize melanin

Function of Melanocytes

Produce melanin that protects skin from sun damage
melanosomes of keratinocytes concentrate around the cell nucleus to protect DNA

skin color depend on:

melanin production, not number of melanocytes

Ultraviolet radiation

causes DNA mutations and burns that lead to cancer and wrinkles

skin reddens

dilation of blood vessels from heat

skin pales

decreased blood flow

Cyanosis

Bluish skin tint caused by severe reduction of blood flow/oxygenation

Jaundice

yellow skin color caused by build up of bile in blood

Pituitary tumor

extremely bronze tan skin caused by excess melanocyte-stimulating hormone (MSH) production

Addison's disease

extremely bronze tan skin
Disease of pituitary gland
release more adrenocorticotropic hormone (ACTH)

Vitiligo

loss of color due to loss of melanocytes
Appears as patches

Vitamin D3/cholecalciferol

produced by epidermal cells in presence of UV radiation
Liver and kidneys convert it into calcitriol

Calcitriol

hormone that aids in absorption of calcium and phosphorous from food in intestine

Vitamin D3 insufficiency

Rickets - bending of weakened bones under body weight
Caused by insufficient sunlight exposure or dietary intake of vitamin D3

Epidermal Growth Factor (EGF)

Powerful peptide growth factor
Produced by salivary and duodenum glands
Used in labs to grow skin grafts

Epidermal Growth Factor functions

Promotes division of germinative cells
Accelerates keratin production
Stimulates epidermal repair
Stimulate glandular secretions

Dermis

located between epidermis and subcutaneous layer
Anchors epidermal accessory structures

Two components of dermis

outer papillary layer
deep reticular layer

Outer papillary layer

Closer to epidermis
Consists of areolar tissue
Contains small capillaries, lymphatics, and sensory neurons
Has dermal papillae projecting between epidermal ridges

Inner reticular layer

Closer to hypodermis
Consists of dense, irregular connective tissue
Contain larger blood vessels, lymphatic vessels, and nerve fibers
Contain collagen and elastic fibers
Contains connective tissue proper

Dermatitis

Inflammation of papillary layer; rapidly spread across the entire integument

Causes and characteristics of dermatitis

Infection, radiation, mechanical irritation, chemicals
Characterized by itch or pain

Fibers in dermal strength and elasticity

Collagen fibers
Elastic fibers

Collagen fibers

Very strong
Provide limited flexibility and resist stretching

Elastic fibers

Permit stretching and recoiling
Provide flexibility

Skin turgor

caused by H2O content of skin
Provides flexibility and resilience

Cleavage lines

Formed from collagen and elastic fibers in the dermis
Resist force in a specific direction

Cleavage (tension/Langer) lines

Establish important patterns
Parallel cut remains shut, heals well
A cute across pulls open and scars

Causes of sagging and wrinkles

dehydration, age, hormonal changes, UV exposure

Stretch marks

thickened tissue resulting from excessive stretching of skin due to pregnancy and weight gain

Treatment of wrinkles

Retin- A (vitamin A derivative) to stimulate skin repair

Decubitus Ulcers

Bedsores are caused by issues with dermal circulation
Caused by compression of superficial blood vessels
Most common on the skin covering joints or bony prominences

Decubitus Ulcers Affects

epidermis by killing epithelial cells
dermis by eroding dermal tissues

Innervation of the skin

nerve fibers

Controls of nerve fibers

Blood flow
Gland secretions
Sensory receptors (light and deep)

Light touch

tactile (Meissner's) corpuscle
located in dermal papillae

Deep pressure and vibration

lamellated (Pacinian) corpuscle
located in reticular layer

Accessory structures (epidermal derivatives)

derive from the embryonic epidermis
located in dermis
project through skin surface

All parts of human body is covered with hair expect:

Palms
Soles
Lips
Portions of external genitalia

Hair functions

Protection
Insulations
Guards openings against particles and insects
Sensitive to very light touch

Hair follicle

located deep in dermis
Produce nonliving hairs
Wrapped in dense connective tissue sheath

What sensory nerves surrounds base of Hair follicle

root hair plexus

Accessory structures of hair

Arrector pili
Sebaceous glands

Arrector pili

involuntary smooth muscle
Cause hair to stand up "goose bumps"

Sebaceous glands (oil gland)

lubricate hair
control bacteria

Regions of hair

hair root
hair shaft

Hair root

lower part of hair
attached to integument

Hair shaft

upper part of hair
not attached to integument

As hair is _____, it is ______

produced; keratinized

Soft keratin

flexible
In the medulla

hard keratin

stiff
cortex and cuticle

3 Hair shaft structure

medulla - the central core
cortex -middle layer
cuticle- the surface layer

hair production

begins at base of hair follicle, deep in dermis

hair papilla

contains capillaries and nerves
surrounded by hair bulb of hair root

_____ produces hair matrix

hair bulb

Hair matrix

layer of dividing basal cells
produce hair structure
pushes hair up and out of skin

Hair color is

produced by melanocytes at the hair papilla
determined by genes
influenced by hormonal and environment

What causes white hair?

lack of pigment and air bubbles in medullar of hair

Types of hair

vellus hairs
terminal hairs

Vellus hairs "peach fuzz"

soft, fine
covers body surfaces

terminal hairs

heavy, pigmented
On head, eyebrows, and eyelashes
Goes to other parts of body after puberty