The Integumentary
System
Anatomy & Physiology
Chapter 4
Classification
of Body Membranes
cutaneous membranes
1.
◦
skin
mucous membranes
2.
◦
◦
covers body cavities
that open to exterior
mucosa
serous membranes
3.
◦
◦
◦
synovial membrane
1.
◦
◦
◦
no epithelial cells
made of areolar CT
line capsules
surrounding synovial
joints, tendon sheaths
& bursae
serosa
covers ventral cavities
& organs in them
visceral & parietal
peritoneum
Epithelial
Connective Tissue
Integumentary System

Includes:
◦
◦
◦
◦
Skin
Nails
Hair
Sweat & Oil Glands
Integumentary System
Functions:
 protection
 body temperature homeostasis
 excretion of urea& uric acid
 part of vitamin D synthesis
Protection

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
Functions of Skin

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-2


excretory function: sweat contains urea,
uric acid (breakdown products of
proteins)
helps in synthesis of Vitamin D
◦ sunlight on skin activates conversion of previtamin D  vitamin D
Vitamin D
Structure of the Skin
made of 2 kinds of tissues
1. Epidermis
2. Dermis

Epidermis




made of stratified squamous epithelium
some keratinized, some not
avascular
Cells:
◦ Keratinocytes
 majority of cells
 make keratin
◦ Melanocytes
◦ Langerhans Cells
 Immune System
Epidermal Layers
stratum basale
1.
◦
◦
deepest layer
constantly undergoing cell division/ cells
pushed upward
stratum spinosum
stratum granulosum
stratum lucidum (only in thick skin)
2.
3.
4.
◦
clear, flatter, more keratin
stratum corneum (cornified =
keratinized)
5.
◦
outermost layer/ 20-30 dead cells thick
Epidermal Layers
Stratum Corneum

dead cells flake off steadily continually
being replaced by cells gradually pushing
up from the stratum basale
Melanin

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
radiation
freckles & moles: seen where melanin
concentrated in 1 spot
Freckle
Excessive Sun Exposure



causes elastic fibers to clump  leathery
skin
depresses immune system
UV radiation damages DNA  skin cancer
Dermis

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. Papillary
2. Reticular

Dermis: Papillary Layer
upper dermis
 dermal papillae: uneven projections into
lower epidermis that contain:
1. capillaries
2. pain receptors
3. touch receptors: Meissner’sCorpuscles
4. in thick skin: form ridges (fingerprints)
that improve gripping ability

Dermal Papillae
Dermis: Reticular Layer
deepest skin layer
 Contains:
1. sweat & oil glands, hair follicles, blood
vessels
2. Pacinian corpuscles (deep touch receptors)
3. many phagocytes
4. fibers: elastic: give young skin elasticity
collagen: make dermis tough& keep
skin hydrated by binding to water

Reticular Layer
Body Temperature Homeostasis


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
Decubitus Ulcers


aka bedsores
due to extended restriction of normal
blood supply to skin
Skin Color
3 pigments contribute to skin color:
1. Melanin

◦
amount & kind (yellow  black)
Carotene
2.
◦
◦
orange – yellow pigment
stratum corneum & subcutaneous layers
Hemoglobin
3.
◦
◦
amount O2 bound to it in RBCs in dermal
blood vessels
has greater affect in light skinned people
Skin Color
in Sickness & in Health





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)
Appendages of the Skin
Glands:
 all are exocrine glands (secrete product
thru ducts)
 secrete their product to skin
 2 groups:
1. Sebaceous glands
2. Sweat glands

Sebaceous Glands



are oil glands
all over skin except palms& soles
ducts mostly empty onto hair follicle rest
onto skin surface
Sebaceous Glands

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 Gone Bad



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
ACNE
SEBORRHEA
Sweat Glands
also known as sudoriferous glands
 all over skin
 2 types:
1. Eccrine sweat glands
2. Apocrine sweat glands

Eccrine Sweat Glands


all over body
produce sweat
◦ clear
◦ pH 4 – 6 (being acidic  bacteriostatic)
◦ mainly water (+ NaCl, NH3, urea, uric
acid, & lactic acid)
Eccrine Glands
Eccrine Glands

typically sweat
released from duct
thru pore
(different from
facial “pores”;
those are openings
of hair follicles)
Eccrine Sweat 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

Apocrine 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)

Appocrine Glands