INTERGUMENTARY SYSTEM (PART 1)

Other name for skin

cutaneous membrane

Skin

• covers the EXTERNAL SURFACE of the body

• LARGEST ORGAN of the body in weight

Skin of adults

• covers an area of about 2 SQUARE METERS (22 square feet)

• weigh 4.5-5 kg (10-11 lb)

• about 7% of total body weight

Components of integumentary system (skin)

1. superficial epidermis

2. thin epidermis

3. deep thicker dermis

Subcutaneous layer

• deep to the skin

• attaches the dermis to underlying fascia

Epidermis

composed of KERATINIZED STRATIFIED SQUAMOUS EPITHELIUM

Four principal types of cells

• keratinocytes

• melanocytes

• intraepidermal macrophages

• tactile epithelial cells

Keratinocytes

most of the epidermis consists of ___, which produce the protein keratin (protects underlying tissues), and lamellar granules (contains a waterproof sealant)

Other term for stratum basale

stratum germanativum

Stratum Basale 

• deepest layer

• composed of CUBOIDAL or COLUMNAR keratinocytes that contains scattered keratin intermediate filaments

Other term for intermediate filaments

tonofilaments

Cell division

stem cells undergo ____ to produce new keratinocytes

Melanocytes and tactile epithelial cells 

associated with tactile discs are scattered among keratinocytes

Stratum spinosum

• EIGHT TO TEN ROWS of many sided keratinocytes with bundles of keratin intermediate filaments

• contains projections of MELANOCYTES and INTRAEPIDERMAL MACROPHAGES

Stratum granulosum 

• THREE TO FIVE ROWS of FLATTENED keratinocytes, in which organelles are beginning to degenerate

Cell contains the following

• protein keratohyalin

• lamellar granules

Protein keratohyalin

converts keratin intermediate filaments into keratin

Lamellar granules

release lipid-rich, water repellant seretion

Stratum corneum

• THIN layer

• FEW to FIFTY or MORE ROWS of dead

• FLAT keratinocytes that contain mostly KERATIN

Keratinization and growth of the epidermis

newly formed cells in the stratum basale are slowly pushed to the surface

Keratinization

a process where as the cells move from one epidermal layer to the next, they accumulate more and more keratin

Rate of cell division

The ____ in the stratum basale increases when the outer layers of the epidermis are stripped away, as occurs in abrasions and burns

Epidermal growth factor (EGF)

the mechanisms that regulate this remarkable growth are not well understood, but hormone like proteins such as _____ play a role

Dandruff

an excessive amount of keratinized cells shed from the skin of the skin of the scalp

Dermis

• second deeper part of the skin

• composed of DENSE IRREGULAR CONNECTIVE TISSUE containing collagen and elastic fibers

• also has the ability to stretch and recoil easily

Woven network of fibers

this ______ has great tensile strength (resists pulling or stretching forces)

Papillary

• superficial portion of dermis (about one-fifth)

• consists of areolar connective tissue with thin collagen and fine elastic fibers

• contains dermal ridges that house blood capillaries, corpuscles of touch, and free nerve endings

Reticular

• deeper portion of dermis (about four-fifths)

• consists of dense irregular connective tissue with bundles of thick collagen and some coarse elastic fibers

Spaces between fibers contain the following:

• adipose cells

• hair follicles

• nerves

• sebaceous glands

• sudoriferous glands

Combination of collagen and elastic fibers

provides the skin with

• strength

• extensibility

• ability to stretch

• elasticity

• the ability to return to original shape after stretching

Skin color as diagnostic clue

• cyanotic

• jaundice

• erythema

• pallor

• albinism

• vitiligo

Embryonic epidermis

the hair, skin glands, and nails develop from this

Accessory structure of the skin

• they have a host of important functions

• for example, hair and nails protect the body, and sweat glands help regulate body temperature

Other term for hair

“pili”

Hair 

present on most skin surfaces

Parts of the body that don’t have hair

• palms

• palmar surfaces of the fingers

• soles

• plantar surfaces of the feet

Parts of a hair

• shaft

• root

• hair follicle

• epithelial root sheath

• dermal root sheath

• bulb

• papilla of the hair

• hair matrix

• hair root plexus

• arrector pili

Hair growth

• growth stage

• regression stage

• resting stage

Clinical connection

• hirsutism

• androgenic alopecia

Types of hair

• lanugo

• terminal hairs

• vellus hairs

Male

• 95% terminal

• 5% vellus

Female

• 65% terminal

• 35% vellus

Skin glands

• sebaceous glands-sebum

• sudoriferous glands-eccrine glands, apocrine sweat glands

• ceruminous glands-cerumen

Sebaceous Glands

Sebum

Sudoriferous Glands

• eccrine glands

• apocrine sweat glands

Ceruminous Glands

cerumen

Eccrine glands

• thermoregulatory sweating

• insensible perspiration

• sensible perspiration

• emotional sweating or a cold sweat

Nails

are plates of tightly packed, hard, dead, keratinized epidermal cells that form a clear, solid covering over the dorsal surfaces of the distal portions of digits

Parts of Nails

• nail body (plate)

• free edge

• nail root

• lunula

• hyponychium

• nail bed

• eponychium or cuticle

• nail matrix

Nail root

the portion of the nail that is not visible

Eponychium (cuticle)

the stratum corneum of the epidermis

Lunula

thick, white part of the nail

Nail bed

the skin below the nail plate

Nail body

the visible portion of the nail

Free edge

extends past the finger or toe

Hyponychium

secures nail to the fingertip

Nail matrix

• the epithelium proximal to the nail root

• contains dividing cells, which produce new nail cells

Eccrine glands

• sweat glands all over the body from birth

• for thermoregulation

Apocrine glands

• sweat glands active during puberty

• stress response and scent

Functions of Nails

1. protects the distal end of the digits

2. provides support and counterpressure to the palmar surface of the fingers to enhance touch perception and manipulation

3. allows us to grasp and manipulate small objects, and they can be used to scratch and groom the body in various ways

Functions of the Integumentary system

1. regulates body temperature

2. stores blood

3. protects body from external environment

4. detects cutaneous sensations

5. excretes and absorbs substances

6. synthesizes vitamin D

Deep wound healing

• inflammatory phase

• migratory phase

• granulation phase

• proliferative phase

• maturation phase

General senses includes the following

• somatic senses (tactile, thermal, pain, and proprioceptive)

• visceral sensation

Olfaction: sense of smell

• olfactory epithelium

• olfactory receptor cells-first-order neurons of the olfactory pathway

• olfactory cilia

• odorants

Odorants

chemicals that have an odor that bind to and stimulate the olfactory receptors in the olfactory cilia

Gustation: sense of taste

• taste or gustation is a chemical sense

• simpler than olfaction

Five primary tastes that can be distinguished

• sour

• sweet

• bitter

• salty

• umami

Anatomy of Taste buds and papillae

most of the nearly 10,000 taste buds of a young adult are on the tongue

Other location of taste buds

• soft palate (posterior portion of the roof of the mouth)

• pharynx (throat)

• epiglottis (cartilage lid over voice box)

Papillae

taste buds are found in elevations on the tongue called ___

Circular vallate (papillae wall-like) or circumvallate papillae

• about 12 very large

• form an inverted V-shaped row at the back of the tongue 

• each of these papillae house 100-300 taste buds

Fungiform papillae

are mushroom-shaped elevations scattered over the entire surface of the tongue that contain above five taste buds each

Foliate papillae

are located in small trenches on the lateral margins of the tongue, but most of their taste buds degenerate in early childhod

Filiform papillae

• the entire surface of the tongue has this

• these pointed, threadlike structures contain tactile receptors but no taste buds

• they increase friction between the tongue and food, making it easier for the tongue to move food in the oral cavity

Tastants

chemicals that stimulate gustatory receptor cells

Vision

• the act of seeing

• extremely important to human survival

• more than half the sensory receptors in the human body are located in the eyes

• large part of cerebral cortex is devoted to processing visual information

Accessory structures of the eye

• eyelids

• eyelashes and eyebrows

• the lacrimal apparatus

• extrinsic eye muscles