PHYSIOLOGY INTRO:
The Integumentary System
Honors Biology
Unit 8 – Powerpoint #1
Chapter 35 /36
What is Physiology?
• Physiology is the study of the functions of living
organisms and their parts
What is Homeostasis
• The ability to maintain a constant internal environment
Eleven Organ Systems
For example the Skeletal System which
includes your bones, cartilage,
ligaments and tendons.
Try to think of as many organ systems
as you can. Write them on the lines
provided.
The Eleven Organ Systems
• Skeletal
• Reproductive
• Muscular
• Excretory
• Circulatory
• Lymphatic/Immune
• Respiratory
• Endocrine
• Digestive
• Integumentary
• Nervous
Today: Integumentary System
• Structures: skin, hair, nails, sweat
glands and oil glands.
• Functions:
• Barrier against infection and injury (including UV
protection)
• Helps regulate body temperature
• Prevents H2O loss
• Waste excretion
• Vitamin D synthesis
Fun Facts
• Where is your thinnest skin located? Thickest?
• Eye lids (thinnest) soles of feet (thickest)
• How many skin cells do you shed in a minute?
• About 30,000-50,000 dead cells
• How many pounds of skin do you loose per year?
• 8-10 lbs
• How much of the dust in your home is dead skin cells?
• 50% (Globally, dead skin accounts for about a billion tons of
dust in the atmosphere)
• Does sweat smell?
• No, it’s the bacteria 
• How much bacteria is on your body?
• 1,000 different species AND 1,000,000,000,000 individual
bacteria
The Largest Organ
• Skin is 12-15% of body weight
• 15-20 sq. ft ( 1.5-2.0 sq. meters)
• Some organisms, such as insects, and
some amphibians, use the
integumentary system for respiration
2 Layers
• The skin is made of 2 main layers
1) Epidermis
2) Dermis
Below the dermis is subcutaneous fat
(hypodermis) that insulates body
Skin: The Layers
Epidermis: First layer
Structure
• Outer layer are flattened, dead cells, inner layer
living
• As lower cells do mitosis they move and push
others to surface of skin
• As move up, become flattened and make keratin
(tough, fibrous protein)
• Takes 30-45 days for new cells to reach the top
• Contain nerve endings but no blood vessels
Epidermis
Epidermis: First layer
Function
1) Water resistance (keratin filled dead cells)
2) Protective layer against biological/ chemical
assault
3) Contains MELANOCYTES (Produce pigment
MELANIN which protects from UV) (will talk more about later)
4) Contains Merkel cells – attached to nerves and
detect touch
5) Contains Langerhans cells –guard against
toxins, microbes and other pathogens that
penetrate the skin. If detected, alerts immune
system
Epidermis
Skin: Dermis
Found beneath the
Epidermis
Dermis: Second layer
Structure
Made of strong, flexible connective tissue
Contains:
Collagen
Nerves
Blood vessels
Lymph vessels
Hair follicles
Sweat glands
Muscles (attached to hair follicles)
Dermis: Second layer
Function
1) Contains Sweat glands (3000/ in2) these:
-maintain homeostasis- regulates body temp
-Release various wastes from bloodstream
-Mammary glands and ear wax glands are modified
sweat glands
2) Contains Sebaceous (oil) glands (2 per hair)
These glands release SEBUM keeping the epidermis
and hair flexible and waterproof
3) Contains many sensory cells
4) Gives skin its elasticity and strength (collagen)
Skin color
• Skin color is due mainly
to the pigment
MELANIN (made by
melanocytes in the
epidermis)
• 2 types of melanin
• Eumelanin (comes in
brown and black)
• Phomelanin (pinkishred)
Skin Color
• Darker skin is due to kind and amount of melanin
produced (everyone has relatively similar
numbers of melanocytes)
• UV rays stimulate melanocytes to make more
melanin (causing tanning)
• Melanin protects skin cells under it from harmful
UV B rays
Melanoctyes
Skin Markings
Skin Markings:
Freckles: Flat, melanized patches
Varies with heredity or sun exposure
Moles: Elevated patches of
melanized skin, with hair
This is your hair, and yes
that is bacteria 
Hair
• Made of Keratin
• Hair covers almost every exposed surface.
• Hair growth is determined by hormones
• You are born with as many hair follicles as you
will ever have
• Hair is used for protection. From the sun, or dirt
• Hair color
• Depends on kind (red, brown, black) and amount of
melanin
• Hair Texture
• Related to difference in shape of hair
• Straight = round, Wavy = oval, Tightly curly = flat
Hair differences
• Scanning electron
micrograph of a hair fiber
from a Caucasian blonde
female (above) and an
Asian male (below). The
overlapping cells of the
cuticle are readily apparent
on both fibers.
Nails
• Scale-like modification of the epidermis
• Made of thin, dead, scaly cells, packed
together
• Protect the ends of the fingers and toes
• Produced by the nail root: an area of rapid
mitosis
• Fingernails grow 1mm/week, toenails
slower
Disorders
• Skin Cancer
• Basal Cell Carcinoma
• Most Common – 99% fully cured
• Squamous Cell Carcinoma
• Lower layer of epidermis
• Induced by the sun
• Malignant Melanoma
• Cancer of pigment cells = melanocytes
• Rare – 1% of skin cancers
• Poor chance of cure
• Often begins with moles
What not to do:
Burns: 1st Degree
• Inflamed, red skin – surface of epidermis is
shed
2nd Degree
• Blisters form as fluid builds beneath epidermis
• Burns epidermis and part of dermis
3rd Degree
• Epidermis & Dermis is
destroyed
• Catastrophic loss of fluids
(dehydration)
• Highly susceptible to
infection
• Look up photos online if you
would like (they can be pretty
graphic)
Aging
• Hair
• Thin and gray as melanocytes die, and mitosis slows
• Oil Glands
• Sebaceous glands atrophy (shrink) = Skin and hair become
drier
• Skin Layers
• Mitosis slows, Collagen lost from dermis = Skin becomes
thin and translucent,
• Loose and sagging as elastic fibers are lost in dermis
• Fewer blood vessels = More bruising, slower healing
• Age Spots – accumulation of pigment cells
Interesting Websites on Integumentary
system
• Interesting Facts
• http://visual.ly/50-incredible-facts-about-skin
• Skin Anatomy and Effects of Aging
• http://science.nationalgeographic.com/science/health-and-humanbody/human-body/skin-article/
• Skin Cancer Investigation
• http://sciencenetlinks.com/interactives/skindeep/interactive/base.ht
ml