Skin Tissue
Chapter 33, Section 3
In your textbook
5.5 Multicellular Life
KEY CONCEPT
Cells work together to carry out complex
functions.
5.5 Multicellular Life
Multicellular organisms depend on interactions among
different cell types.
CELL
TISSUE
leaf
stem
vascular
tissue
ORGAN
lateral
roots
primary
root
root system
• Tissues are groups of cells that perform
a similar function.
• Organs are groups of tissues that
perform a specific or related function.
• Organ systems are groups of organs
that carry out similar functions.
shoot system
SYSTEMS
5.5 Multicellular Life
Specialized cells perform specific functions.
• Cells develop into their mature forms through the process
of cell differentiation.
• Cells differ because different combinations of genes are
expressed.
• A cell’s location in an embryo helps determine how it will
differentiate.
Outer: skin cells
Middle: bone cells
Inner: intestines
Parts of the Skin
 Outer covering of
an animal
 Largest organ of
the body (surface
area = 18 ft2)
Parts of Skin, cont’d.
 Accessory
Organs




Hair
Nails
Oil glands
Sweat glands
Layers of Skin
 Epidermis: the outermost skin layer
 Dermis: contains sweat glands, oil glands and
hair follicles
 Subcutaneous layer: protects and cushions
Epidermis
 Outermost layer of skin
 Contains pores for sweat, salts and oils
 The surface of the epidermis is mostly made
of dead cells that continually flake off
At left, the layers of the epidermis. At right, the
epidermis through a scanning electron
microscope.
Epidermis
 Cells produce
protective proteins
(keratin and melanin)
 Below the surface,
living cells are
constantly dividing
and pushing up to
replace dead ones
Dermis
 Thicker layer
beneath the
epidermis
 Cells produce elastin
for flexibility and
collagen for shape
Dermis
 Contains hair follicles -
produce keratin that
forms hair
 Contains sweat and oil
glands


Sweat glands produce
sweat
Oil glands lubricate and
waterproof the skin
Subcutaneous Fat
 Layer beneath the dermis
 Protects and cushions
 Contains blood vessels and neurons
 Insulates muscles and internal organs
Functions of Skin (click for video)





Protection
Sensation
Temperature regulation
Control of evaporation
Synthesis and storage of compounds
(Vitamin D)
 Excretion
 Absorption
 Water resistance
Protection
 Protection from / against
 Damage to internal organs



Microorganisms (bacteria, viruses)


Oil glands release acidic oils that protect from fungi and
bacteria
Dehydration



Elastin in dermis allows flexibility
Subcutaneous fat cushions blood vessels/neurons
Keratin in fingernails and hair helps waterproof
Oil glands lubricate and waterproof skin
UV rays (pigment plays a role)

Melanin in skin absorbs harmful UV radiation and
protects internal organs
Homeostasis
 Nerves in skin cause dilation or contraction of
blood vessels to regulate body temperature
 Sweat removes excess water, salts and oils
from the blood
 Sweat glands cool the body as sweat
evaporates from the skin
Make sure you can label all of the
parts of the skin in the diagram below