a&p lecture chap 5 Integumentary System

1.1-2.2 square meters

4-5kg

7%total body mass

"technically" not part of the skin

mostly adipose tissue (Stores fat)

superficial to the tough connective tissue

Anchors the skin to underlying structures (mostly muscle), but loosly enough that the skin can slide relatively freely over those structures

shock absorber

insulator

keratinized stratified squamous epithelium

• 1. Keratinocytes
• 2. Melanocytes
• 3. Epidermal dendritic cells (Langhans Cells)
• 4. Tactile/Merkel Cells

-produce keratin

-keratin is a fibrous protien which gives the skin its protective qualities

-tightly connected, arise and push to the top from the stratum basale

-cells are dead by the time they reach the surface and rub off

-total new epidermis every 25-45 days

-make melanin

-found in the stratum basale

-melanin accumulates in membrane-bound melanosome

-melanin granules accumulate on the superficial side of the keratinocyte nucleus to form a pigment shield protecting against damaging rays

Also called Langerhans Cells

-arise from bone marrow and migrate to the spidermis

-ingest foreign substances

-key activator of our immune system

-form a continous network around keratinocytes

Also called Tactile Cells

-sometimes present at the spidermal junction

-shaped like a spikey hemisphere

-imtimately associated with disc-like sensory nerve endings

-tactile/merkel discs act as a sensory receptor for touch

-attached to the dermis by wavy layer

-mostly contains a simple layer of stem cells (stratum germinativum)

-rapid division and location of youngest kertiniocytes

-each time a basale cell divides, one moves to the top to become a mature keratinocyte

-10-25% of cells are melanocytes

-occasional tactile cells

Also called the Prickly layer

-several layers thick

• -these cells contain a weblike system of intermediate filaments
• -mostly pre-keratin

-these look like little spikey balls, and these spines on keratinocytes is why its called the prickly layer

-melanin granules scattered throughout

-peridemal dendtric cells are most abundant here

Also called the granual layer

-thin layer, 3-5 cell layers

-process of keratinization begins

• Two types of gradules:
• 1. Keratohyaline Granules- help to form keratin in the upper layers
• 2. lamellated Granuels- slow water loss across epidermis

-nutrients diffused from the connective tissue do not go past this layer

-kertinocytes become tougher

• *absent in thin skin
• Also called the clear layer

-2-3 layers of clear, flat, dead kertinocytes with indistinct boundaries

-only visible in thick skin

Also called the horny layer

-20 to 30 cells thick, makes up to 3/4 of the epidermal thickness

- kertain and thickened plasma membranes protect from abrasion

-glycolipids between cells make it waterproof

-dead cells

-major protection from the enviornment

-shingle-like remnant of this layer are called cornified/horny cells (like dandruff)

• -flexible connective tissues with cells like:
• fibroblasts, macrophages, and occassional mast cells and white blood cells

-equivilent to the animal hide

-rich in nerve fibers, blood vessels, and lymphatic vessels

-hair follicles and oil and sweat glands reside here

-2 layers: papillary and reticular

-thin, superficial to the reticular layer

• -areolar connective tissue
• -looseness allows defense cells to wander and look for intruding bacteria

• -peglike projections called the dermal papillae indent into the superifical epidermis
• -may contain cappilary loops, free nerve endings, and touch receptors called Meissner's capsules

• -in the hands and feet, the dermal papillae lay on top of other mounds, which create epidemal ridges (called friction ridges)
• -sweat pores along crests

-80% of the thickness of the Dermis

-course, irregularly arranged, dense fibrous tissue

-network of blood vessels nourishing this layer, cutaneous plexus, lies beterrn this layer and the hypodermis

• -extracellular matrix contains some adipose cells and thick bundles of interlacing collagen fibers
• -most fibers run parallell to the surface

• -less dense regions (separations) form cleavage/tension lines
• -externally invisible
• - surgeons cut along these lines to decrease gaping and enhance healing

-collagen fibers give strength and bond water

-elastic fibers provide stretch-recoil properties

-Flexure lines are dermal folds that occue near joints where the dermis is tightly secured to a deeper structure (lines on palms and soles)

• 3 Pigments contribute
• -Melanin
• -Carotene
• -Hemoglobin

Only melanin is made in the skin

• -all humans have relatively the same number of melanocytes
• -darker people produce and retain more and darker melanosomes

-freckles and moles are local accumulations of melanin

-range from yellow to tan and from reddish brown to dark brown

-melanin pigment is found only in the deeper layers of the epidermis

• -melanocytes are stimulated to greater activity by chemicals secreated by the surrounding keratinocytes when we expose ourselves to sunlight
• -this melanin activity leads to a tan

Yellowish/Orange Pigment

most obvious in palms and soles, where stratum corneum is the thickest

Pinkish hue reflects this oxygenated pigment in red blood cells

Redness or Erythema: embarrassment, fever, hypertension, inflammation, or allergy

Pallor or blanching: fear, anger, emotional stress, anemia or low blood pressure

Jaundice: yellowing of the skin indicates liver problem

Bronzing: Addison's disease

Black and Blue marks or bruises: clotting under skin

-derivitives of the epidermis

Include: hair, hair follicles, nails, oil glands, sweat glands

-distributed over the entire body except for nipples and parts of the external genetalia

2 kinds: eccrine and aprocrine

Also called Mecrocrine Sweat Gland

-more numerous

-particuarly abundant on palms, soles, and forehead

-simple, coiled, tubular gland

-secretory part lies coiled in the dermis while duct extends to open in a funnel shaped pore at skin surface

-secretion called true sweat: 99% water, pH between 4-6

-regulated by symphatic division of the automic nervous system (mostly involuntary)

-prevents over heating of body

-overheated sweating starts at the forehead and moves to the rest of the body

-"cold sweat" starts at palms, soles, and armpits and then spreads

-largely confined to the auxillary and anogential areas

-larger than eccrine glands

-tend to lie deeper in the dermis or the hypodermis

-ducts empty into hair follicles

-same component as sweat, plus fatty substances and protience

-secretion itself has no odor, but its organic compounds decompose due to bacteria on the skin. this makes body odor

-activated during puberty

-function not completely known, but are activated by the symphatic nerve fibers during pain, stress, and pleasure

• Ceruminous Glands: modified aprocrine glands dount in the lining of the external ear
• -secretions mix with sebum from near by sebaceous glands to form ear wax

Mammery Glands: are specialized sweat glands that secrete milk

-simple branced alveolar glands

-found all over body except thick skin of palms and soles

-small on trunk and limbs, quite large on face, neck, and upper chest

-secrete sebum

-alveoli become engorged with oily lips until they burst (holocrine glands)

-most sebaceous glands develop from the hair follicle and the sebum is secreted into the hair follicle or occassionally to a pore on the skin surface

-softens and lubricates the hair and skin

-prevents hair from becoming brittle

-slows water loss from skin

-antibacterial

-secretion is stimulated by hormones called androgen

-arrector pili contractions force sebum our of the hair follicles onto the skins surface

-help sense bugs on the skin

-hair on scalp insulates and protects from injury

-eyelashes shield eyes

-nostril hairs help filter particles and bugs

-Only absent on palms, soles, lips, and external genetalia

Hair are flexible strands produced by hair follicles

• Consist largely of dead, keratinized cells
• -hard keratinized cells which are tougher and individual cells do not flake off

• chief regions are:
• -shaft
• -root

Projects from the Skin

Extends about halfway down the portion of the hair embedded in skin

*shape of shaft determines kind of hair

Root is the remainder of the hair deep in the follicle

• 1. Medulla: central core
• - large cells and air spaces
• -only part of the hair containing soft keratin
• -absent in fine hairs

• 2. Cortex: bulky layer surrounding medulla
• -several layers of flattened cells

• 3. Cuticle: outter-most layer
• -single layer of cells
• -like shingles on a roof
• -most heavily keratinized
• -provides strength
• -keeps inner layer compacted
• -cuticles wear away at ends creating split ends

-Folds down from epidermis to dermis, and sometimes to hypodermis

-Deep end of follicle is expanded to form a hair bulb

-a knot of sensory nerve receptors called a hair follicle receptor or root hair plexus wraps around each hair bulb as a touch receptor

-Hair papilla contains a knot of capillaries that supplies nutrients

Connective Tissue Rooth Sheath: Outter layers, derived from dermis

Glassy Membrane: thickened basement membrane

• Epithelial rooth Sheath: derived mainly from the invagination of the epidermis
• -thins as it approaches the hair bulb

• Hair Matrix: the activly dividing area of the hair bulb
• -originates in the hair bulge, just above the hair bulb
• -as new cells are produced by the matrix, older part is pushed up

Arrector Pili: bundle of smooth muscle cells attached to the follicle and the skin (responsible for good bumps)

Vellus: body hair of children and adult women which are thinner and fairer

• Terminal: courser hair of the eyebrows and scalp
• -grows at puberty on body due to androgen hormones

*growth is determined by nutrients and hormones

about 2.5mm/week

• Active Phase (weeks to Years)
• Regressive Phase
• -hair matrix cells die
• -follicle base and bulb shrivel somehwat
• -hair papilla push upward
• Resting Phase

*hair is limited to a certain amount of cycles in its lifetime

Alopecia: baldness due to thinning

Male Pattern Baldness: genetically predisposed. Hair sheds before it leaves the follicle

Hirsutism: excessive hairiness

-Scalelike modification of the erpidermis tha tforms a clear protective covering

-contains hard keratin

-free edge body, nail plate, and root (embedded in skin)

• -deeper layers of the erpidermis in the nail bed thicken in the digit creating a nail matrix
• -matrix is responsible for nail growth

-nails appear pink because of the capillaries underneath

-whitish crescent at proximal end called Lunule lies over the matrix

-skin folds at the lateral and proximal ends called the nail fold

-nail fold projects on the nail as the cuticle or the eponychium

-dirt accumulates in the hyonychium

• 1. Protection
• 2. Body Temperature Regulation
• 3. Cutaneous sensation
• 4. Metabolic Function
• 5. Blood Resevoir
• 6. Excretion

-acts as a chemical barrier

-acid mantle prevents population of bacteria (low pH)

-natural antibiotics (defensins)

-melanin prevents UV rays

-water resistance prevents diffusion

-epidermic dendritic cells are active in the immune system

• -Skin surface loses heat
• -routine sweating called insensible perspiration
• - visible output called sensible perspiration

-When cold, heat loss is slowed by the constriction of dermal blood vessels, allowing warm blood to other parts of the body.

Cutaneous sensory receptors are actually part of the nervous system (exteroceptors)

-different kinds help us feel

-skin is like a chemical factory

-sun exposure creates Vit D.

-creates important protiens and enzymes

-"disarm" carcinogens trying to enter

-convert chemicals into carcinogens

-activate steroid hormones

-can hold up to 5% of the body's blood

-when other organs need more blood, dermal vessels constrict

Sweating releases salt and small amounts of Nitrogen containing waste

• -least malignant and most common (80%)
• -stratum basal cells proliferate and invade dermis and hypodermis
• -most often on sun exposed areas of the face
• -bulbish
• -removal by surgery, survival rates good

• -2nd most common
• -arises from the keratinocytes of th stratum spinosum
• -scaly and round, normally on head
• -grows rapidly and metastizes quickly

• -Cancer of the Melanocytes
• -highly metastic
• -resilient to chemo
• -accounts for only 2-3% of skin cancer, but rates rising
• -early detection is key for surgical removal

• A ssymetry
• B order irregularity
• C olor
• D iameter
• E levation

• -Loss of body fluid = rapid dehydration
• -renal shutdown and circulatory shock

-loss of protiens = need more food and nutrients for repair

-infection and sepsis are MAJOR threats

-Rule of 9s determines the estimate of fluid loss

-only epidermis is damanged

-symptoms include pain, redness, and swelling of site

ex: regular sunburn

-injures epidermis and upper layer of dermis

-symptoms include same as 1stm but blisters appear

full thickness burn

-skin totally damaged

-nerves gone = no pain

-loss of fluids is extreme

-skin grafting is necessary

• 1. over 10% of body is 3rd degree
• 2. Over 25% of body is 2nd Degree
• 3. 3rd degree burns on hands, feet, or face
• -face can cause complication with nasal passageways or other

• 4 mo after conception
• -skin is fairly well formed

• 5-6 mo after conception
• -downy coat of colorless hairs called lanungo coat

• 7mo
• -lanungo coat shed and replaced by vellus hairs

• Birth
• -skin covered in vernix caseosa- cheesy like sebum protecting fetus' skin in the amnion
• -skin very thin
• -accumulation of sebacious glands on nose and forehead called milia will disappear in about 3 weeks

• -skin thickens
• -more subcutaneous fat deposited
• -climate determines amount of sweat glands that will activate

• Adolescence
• -skin and hair become oilier as sebaceous glands are activated

• 20-30's
• -acne subsides
• -skin reaches optimal appearance

• -scaling
• -skins shows effects of enviornment
• -dermititis becomes more common
• -epidermal cell replacement slows
• -deficient lubricating substances
• -subcutaneous fat diminishes
• -decreasing elasticity=wrinkles
• -enhanced risk of skin cancer
• -hair thins and active hair follicles decline
• -graying