1122 Integumentary System

Integumentary system consists of:

• Skin

• Hair

• Nails

• Sweat glands

• Sebaceous (oil) glands

2 layers of Intergumentary System

Epidermis and Dermis

Epidermis

• Epithelial tissue

• Outermost protective shield

• Avascular (receive nutrients by

way of diffusion from

surrounding tissue)

Dermis

• Connective Tissue

• Underlies epidermis

• Makes up bulk of skin

• Vascular

Subcutaneous

Tissue

Hypodermis (superficial fascia)

• Subcutaneous layer deep to skin

• Not part of skin but shares some

functions

• Mostly adipose (shock absorption

& insulation)

• Anchors skin to underlying

structures: mostly muscles

4 types of cells populating the

epidermis

1. Keratinocytes

2. Melanocytes

3. Dendritic cells

4. Tactile epithelial cells

Where is epidermis thick

in areas of abrasion:

fingertips, soles of feet, stratifed sqamous

1. Stratum Basale

(Basal Layer)

• Deepest epidermal layer

• Attaches to the underlying dermis

• Consists of a single row of stem cells

= constantly renewing cell

population (youngest keratinocytes)

• Many nuclei = constant state of

mitosis

• New daughter cells are pushed

upward

2. Stratum spinosum (prickly layer)

• Several cell layers thick

• This layer has weblike filaments attached to

desmosomes

• Allows them to resist tension and pulling

• Scattered among keratinocytes are abundant

melanosomes and dendritic cells

3. Stratum granulosum (granular layer)

• Thin layer

• Cell appearance changes

• Cells flatten, nuclei and organelles disintegrate

• Keratinization begins

• Cells accumulate keratohyaline granules

that help form keratin fibers in upper

layers

• Cells also accumulate lamellar granules, a

water-resistant glycolipid that slows water loss

• Cells above this layer die

• Too far from dermal capillaries to survive

4. Stratum lucidum (clear layer)

• Found only in thick skin

• Consists of thin, translucent band of two to three

rows of clear, flat, dead keratinocytes

5. Stratum corneum

• 20–30 rows of flat, anucleated, keratinized dead

cells

• Accounts for 3/4 of epidermal thickness

• Though dead, cells still function to:

• Protect deeper cells from the environment

• Prevent water loss

• Protect from abrasion and penetration

• Act as a barrier

Skin memonic top to bottom

Come lets get sun burned

apoptosis

how cells change, controllled cell death, dandruff and dander, shed 50k a minute

Keratinocytes

Chief role is to produce keratin, main cells of epidermis

keratin

protein that gives skin its protective properties

Melanocytes

Found in deepest epidermis

• Gives hair and skin its color

• Synthesize the pigment melanin,

which is packaged into

melanosomes, protect from uv damage

Skin cancer that arise from keratinocytes

Basal cell carcinoma & Squamous cell carcinoma

Skin cancer that arise from melanocytes

Melanoma, most dangerous

uneven borders in melanoma

malignancy (cancer)

Dendritic

Cells

Star-shaped macrophages that

patrol deep epidermis

• Are key activators of immune

system

Tactile Epithelial Cells

(Merkel Cells)

Sensory receptors that sense touch, Especially abundant on the surfaces

of the hands and feet

Dermis 2 layers

•Papillary

•Reticular

Papillary Layer

Thin, superficial layer of areolar CT

• Interlacing collagen & elastic fibers with many tiny

blood vessels

• Looseness allows for phagocytes to wander freely

(patrol for bacteria)

Dermal papillae

superficial region of dermis that

sends fingerlike projections up into epidermis

• Projections contains capillary loops, free nerve

endings, and touch receptors

friction ridges

Enhance gripping ability

• Contribute to sense of touch

• Sweat pores in ridges leave unique fingerprint

pattern

Reticular Layer

Makes up ~80% of dermal thickness

• Coarse, dense fibrous connective tissue

• Many elastic fibers provide stretch-recoil properties

• Collagen fibers provide strength and resiliency

• Bind water, keeping skin hydrated

Cleavage (tension) lines in reticular layer are caused by

many collagen

fibers running parallel to skin surface

• Externally invisible

• Important to surgeons because incisions parallel to cleavage lines

heal more readily

Flexure Lines of

Reticula Layer

are dermal

folds at or near joints

Carotene

• Found in certain plants, like carrots

• In the body, can be converted to vitamin A

Hemoglobin

iron-rich protein found inside red blood cells, Light skinned people have less melanin, so the epidermis is more transparent

• See the hemoglobin hue – appears rosy

Cyanosis

Blue skin color: low oxygenation of hemoglobin

Pallor

(blanching or pale color)

• Anemia, low blood pressure, fear, anger

Erythema

(redness)

• Fever, hypertension, inflammation, allergy, infection

Jaundice

(yellow cast)

• Liver disorders

Bruises

(black-and-blue marks)

• Also referred to as ecchymoses or hematomas, are a

result of clotted blood beneath skin

• As clot is broken down, color of bruise changes

Brown or black “necklace” or bruises

• Hyperpigmented dark areas in axillae and around neck

may be a sign of insulin resistance and elevated blood

glucose levels

Hairs

flexible strands of dead,

keratinized cells

• None located on palms, soles, lips, nipples, and

portions of external genitalia

Red hair has

additional pheomelanin

pigment

Hair bulb:

expanded area at deep end of

follicle

Hair matrix

actively dividing area of bulb that

produces hair cells (As matrix makes new

cells, it pushes older ones upward)

Arrector pili

small band of smooth muscle

attached to follicle

• Responsible for “goose bumps”

Hair papilla

Dermal tissue containing a knot of

capillaries that supplies nutrients to

growing hair

Vellus hair

pale, fine body hair of children

and adult females

Terminal hair

coarse, long hair

• Found on scalp and eyebrows

• At puberty

• Appear in axillary and pubic regions

of both sexes

• Also on face and neck of males

Alopecia

hair thinning in both sexes after age 4

True (frank) baldness

Genetically determined and sex-influenced condition

Male pattern baldness

caused by follicular response to DHT

(dihydrotestosterone)

Telogen effluvium (TE)

abrupt hair thinning caused by an

abundance of hair follicles entering resting phase at same time

Nails

Scale-like modifications of epidermis that contain

hard keratin

Nail matrix

thickened portion of bed

responsible for nail growth

Nail folds

skin folds that overlap border of nail

Eponychium (cuticle)

nail fold that projects onto

surface of nail body

Hyponychium

area under free edge of plate that

accumulates dirt

Eccrine (Merocrine) Sweat Glands

Secrete sweat, • Most numerous type

• Abundant on palms, soles, and forehead

• Ducts connect to pores

• Function in thermoregulation

Apocrine Sweat Glands

“”P” for

puberty onset, onfined to axillary and anogenital areas

• Secrete viscous milky or yellowish sweat that contains fatty substances and proteins

• Bacteria break down sweat, leading to body odor

• Larger than eccrine sweat glands with ducts emptying into hair follicles

• Ceruminous glands

lining of external ear canal; secrete cerumen (earwax)

Mammary glands

secrete milk

Sebaceous (Oil) Glands

Secrete sebum, • Widely distributed, except for thick skin of

palms and soles

• Most develop from hair follicles and

secrete into hair follicles

• Relatively inactive until puberty

Functions of

the Skin:

• Protection

• Body temperature regulation

• Cutaneous sensations

• Metabolic functions

• Blood reservoir

• Excretion of wastes

Skin protection barriers

• Chemical barrier

• Physical barrier

• Biological barrier

Skin Protection: Chemical Barrier

Skin secretes many chemicals, such as:

• Sweat, which contains antimicrobial proteins

• Sebum and defensins, which kill bacteria

• Cells also secrete antimicrobial defensin

Acid mantle

low pH of skin inhibits bacterial multiplication

Skin Protection: Physical Barrier

block most water and water-soluble substances

• Some chemicals have limited penetration of skin

Skin Protection: Biological Barrier

Epidermis contains phagocytic cells

• Dendritic cells of epidermis engulf foreign antigens (invaders) and

present to white blood cells, activating the immune response

• Dermis contains macrophages

• Macrophages also activate immune system by presenting foreign

antigens to white blood cells

insensible perspiration

Under normal, resting body temperature, sweat glands produce about 500

ml/day of unnoticeable sweat

sensible perspiration

designed to cool body, If body temperature rises, dilation of dermal vessels can increase sweat gland

activity to produce 12 L (3 gallons) of noticeable sweat

Cutaneous sensory receptors

part of the nervous system

• Exteroceptors respond to stimuli outside body, such as temperature, touch and painful

stimuli

• Immediate threat of burns

dehydration and electrolyte

imbalance

• Leads to renal shutdown and circulatory shock

First-degree burns

Epidermal damage only

• Localized redness, edema (swelling), and

pain

Second-degree burns

Epidermal and upper dermal damage

• Blisters appear

• First- and second-degree burns are referred

to as partial-thickness burns because only

the epidermis and upper dermis are

involved

Third-degree burns

• Entire thickness of skin involved (referred to as

full-thickness burns)

• Skin color turns gray-white, cherry red, or

blackened

• No edema is seen and area is not painful

because nerve endings are destroyed

• Skin grafting usually necessary