The Integumentary System

Anatomy & PhysiologyChapter 4

Classification of Body Membranes

Epithelial Connective Tissue

1. cutaneous membranes

◦ skin

2. mucous membranes◦ covers body cavities

that open to exterior◦ mucosa

3. serous membranes◦ serosa◦ covers ventral

cavities & organs in them

◦ visceral & parietal peritoneum

1. synovial membrane

◦ no epithelial cells◦ made of areolar CT◦ line capsules

surrounding synovial joints, tendon sheaths & bursae

Includes:◦ Skin◦ Nails◦ Hair◦ Sweat & Oil Glands

Integumentary System

Functions: protection body temperature homeostasis excretion of urea& uric acid part of vitamin D synthesis

Integumentary System

of deep tissues from mechanical damage◦ physical barrier by keratin (toughens skin)◦ contains pressure receptors: send sensory

message to CNS; heat & cold receptors CNS

from chemical damage◦ skin is relatively impermeable (keratin)◦ contains pain receptors CNS

from bacterial invasion◦ skin secretions are acidic so inhibit bacterial

growth; phagocytes in skin ingest invaders from UV radiation

◦ melanin made by melanocytes in skin protects nuclei

Protection

dessication◦ keratin & other substances provide

waterproofing body temperature homeostasis

◦ when body overheated blood flow to skin increases & some heat radiates off body, sweating

◦ when body cold less blood flows to skin, more to trunk, goose bumps

Functions of Skin

excretory function: sweat contains urea, uric acid (breakdown products of proteins)

helps in synthesis of Vitamin D◦ sunlight on skin activates conversion of

pre-vitamin D vitamin D

Functions of Skin-2

Vitamin D

made of 2 kinds of tissues1. Epidermis2. Dermis

Structure of the Skin

made of stratified squamous epithelium

some keratinized, some not avascular Cells:

◦Keratinocytes majority of cells make keratin

◦Melanocytes◦Langerhans Cells Immune System

Epidermis

1. stratum basale◦ deepest layer◦ constantly undergoing cell division/ cells

pushed upward2. stratum spinosum3. stratum granulosum4. stratum lucidum (only in thick skin)

◦ clear, flatter, more keratin5. stratum corneum (cornified =

keratinized)◦ outermost layer/ 20-30 dead cells thick

Epidermal Layers

Epidermal Layers

dead cells flake off steadily continually being replaced by cells gradually pushing up from the stratum basale

Stratum Corneum

pigment◦ (yellow to brown to black)

produced by melanocytes◦ most are in stratum basale

cells stimulated to make more melanin when skin exposed to sunlight◦ shields DNA from damaging effects of UV

radiationfreckles & moles: seen where melanin

concentrated in 1 spot

Melanin

Freckle

causes elastic fibers to clump leathery skin

depresses immune system UV radiation damages DNA skin

cancer

Excessive Sun Exposure

a strong, stretchy envelope that helps to hold the body together◦ leather is the dermis of whatever animal it

was made from made of dense CT 2 regions:1. Papillary2. Reticular

Dermis

upper dermis dermal papillae: uneven projections

into lower epidermis that contain:1. capillaries2. pain receptors3. touch receptors:

Meissner’sCorpuscles4. in thick skin: form ridges

(fingerprints) that improve gripping ability

Dermis: Papillary Layer

Dermal Papillae

deepest skin layer Contains:1. sweat & oil glands, hair follicles, blood

vessels2. Pacinian corpuscles (deep touch

receptors)3. many phagocytes4. fibers: elastic: give young skin elasticity collagen: make dermis tough&

keep skin hydrated by binding to water

Dermis: Reticular Layer

Reticular Layer

Skin plays major role in maintaining homeostasis of temperature:

Overheated:◦ Blood vessels in dermis dilate increases

blood flow to skin heat radiates off body Hypothermic:

◦ Blood vessels in skin constrict decreases blood flow to skin less heat loss thru skin

Body Temperature Homeostasis

aka bedsores due to extended restriction of normal

blood supply to skin

Decubitus Ulcers

3 pigments contribute to skin color:1. Melanin

◦ amount & kind (yellow black)

2. Carotene◦ orange – yellow pigment◦ stratum corneum & subcutaneous layers

3. Hemoglobin◦ amount O2 bound to it in RBCs in dermal

blood vessels◦ has greater affect in light skinned people

Skin Color

cyanosis: blue hue to skin; due to poorly oxygenated blood

erythema: redness, due to increased blood flow (infection, inflammation); burn, HT, blushing

pallor: paleness, due to emotions, anemia, low BP, decreased blood flow

jaundice: yellow; usually from liver disease (not clearing bilirubin)

hematomas: bruising (bleeding under skin)

Skin Color in Sickness & in Health

Glands: all are exocrine glands (secrete

product thru ducts) secrete their product to skin 2 groups:1. Sebaceous glands2. Sweat glands

Appendages of the Skin

are oil glands all over skin except palms& soles ducts mostly empty onto hair follicle

rest onto skin surface

Sebaceous Glands

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sebum: product secreted by sebaceous gland◦ made of oils & fragmented cells and

antibacterials◦ function: lubricant’ keeps skin soft & keeps

hair from getting brittle◦ increase activity during puberty (reason

skin becomes oilier)

Sebaceous Glands

if ducts become blocked whitehead forms material in it oxidizes & dries blackhead

Acne: active infection of sebaceous glands, mild to severe causing permanent scarring

Seborrhea: cradle cap; overactivity of sebaceous glands pink raised lesions yellow to brown crust

Sebaceous Glands Gone Bad

SEBACEOUS GLANDS

ACNE SEBORRHEA

also known as sudoriferous glands all over skin 2 types:1. Eccrine sweat glands2. Apocrine sweat glands

Sweat Glands

all over body produce sweat

◦clear ◦pH 4 – 6 (being acidic bacteriostatic)

◦mainly water (+ NaCl, NH3, urea, uric acid, & lactic acid)

Eccrine Sweat Glands

Eccrine Glands

typically sweat released from duct thru pore (different from facial “pores”; those are openings of hair follicles)

Eccrine Glands

important part of body’s heat-regulating equipment

+ nerve endings to cause sweat to be released whenever external temperature or body temperature is high

when water in sweat evaporates it cools body

important to keep body temperature w/in few degrees of 37 ◦C or it malfunctions

Eccrine Sweat Glands

mostly in axilla & genital areas ducts empty onto hair follicles secretions: fatty acids, proteins, +what is in eccrine sweat

if colonized with bacteria will have odor, otherwise odorless

begin to function during puberty (stimulated by androgens)

Apocrine Sweat Glands

Appocrine Glands