PowerLecture:
Chapter 4
Tissues, Organs, and
Organ Systems
Learning Objectives



Understand the various levels of animal
organization (cells, tissues, organs, and
organ systems).
Know the characteristics of the various
types of tissues. Know the types of cells
that compose each tissue type and cite
some examples of organs that contain
significant amounts of each tissue type.
Describe how the four principal tissue types
are organized into an organ such as the
skin.
Learning Objectives (cont’d)

Explain how the human body maintains a
rather constant internal environment despite
changing external conditions.
Impacts/Issues
Stem Cells
Stem Cells
Stem cells are the first to form when a
fertilized egg starts dividing.



Adults have stem cells in some tissues such as
bone marrow and fat; these cells have shown
some promise as therapy.
Embryonic stem cells can be coaxed
to differentiate into many different
types of cells, which can replace
damaged or worn out body cells
perhaps to an extent greater than
adult stem cells.
Stem Cells
The human body is an orderly assembly of
parts (anatomy).





A tissue is an aggregation of cells and
intracellular substances functioning for a
specialized activity.
Various types of tissues can combine to form
organs, such as the heart.
Organs may interact to form organ systems
such as the digestive system.
Homeostasis allows for the stable functioning
(physiology) of all our combined parts.
Video: New Nerves
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
From ABC News, Biology in the Headlines, 2005 DVD.
How Would You Vote?
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 Should
researchers be allowed to start
embryonic stem cell lines from human
embryos that are not used for in vitro
fertilization?


a. Yes, most unimplanted embryos are destroyed
anyway; the potential of stem cells is too great to
ignore.
b. No, any human embryo has the potential to
become a human and so deserves protection
from destruction.
Section 1
Epithelium: The Body’s
Covering and Linings
Epithelium
Epithelial tissue covers the surface of the
body and lines its cavities and tubes.



One surface is free and faces either the
environment or a body fluid; the other adheres
to a basement membrane, a densely packed
layer of proteins and polysaccharides.
Cells are linked tightly together; there may be
one or more layers.
free surface
of epithelium
simple
squamous
epithelium
basement
membrane
connective
tissue
Fig. 4.1a, p. 69
Animation: Structure of Epithelium
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Epithelium
There are two basic types of epithelia.


Simple epithelium is a single layer of cells
functioning as a lining for body cavities, ducts,
and tubes.
•
•

Simple epithelium functions in diffusion, secretion,
absorption, or filtering of substances across the cell
layer.
Pseudostratified epithelium is a single layer of cells
that looks like a double layer; most of the cells are
ciliated; examples are found in the respiratory
passages and reproductive tracts.
Stratified epithelium has many layers—as in
human skin.
Animation: Types of Simple Epithelium
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Table 4.1, p. 68
Epithelium

Both simple and stratified epithelium can be
subdivided into groups based on shape at the
tissue surface:
• Squamous epithelium consists of flattened cells;
examples are found in the lining of the blood vessels.
• Cuboidal epithelium has cube-shaped cells; examples
are found in glands.
• Columnar epithelium has elongated cells; examples
are found in the intestine.
cilia
columnar
cells
basement
membrane
TYPE: Simple squamous
TYPE: Simple cuboidal
DESCRIPTION: FrictionDESCRIPTION: Single layer
reducing slick, single layer of of squarish cells
flattened cells
COMMON LOCATIONS:
COMMON LOCATIONS:
Ducts, secretory part of
Lining of blood and lymph
small glands; retina; kidney
vessels, heart; air sacs of
tubules; ovaries, testes;
lungs; peritoneum
bronchioles
FUNCTION: Diffusion;
filtration; secretion of
lubricants
FUNCTION: Secretion;
absorption
TYPE: Simple columnar
DESCRIPTION: Single layer of tall
cells; free surface may have cilia,
mucus-secreting glandular cells,
microvilli
COMMON LOCATIONS: Glands,
ducts; gut; parts of uterus; small
bronchi
FUNCTION: Secretion; absorption;
ciliated types move substances
Fig. 4.2b-d, p. 70
Epithelium
Glands develop from epithelium.
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

Glands are secretory structures derived from
epithelium that make and release specific
substances, such as mucus.
Glands are classified according to how their
products reach the site where they are used.
•
•
Exocrine glands often secrete through ducts to free
surfaces; they secrete mucus, saliva, earwax, milk,
oil, and digestive enzymes for example.
Endocrine glands have no ducts but distribute their
hormones via the blood.
Section 2
Connective Tissue:
Binding, Support, and
Other Roles
Connective Tissue
Connective tissue binds together,
supports, and anchors body parts; it is the
most abundant tissue in the body.



Fibrous connective tissues and specialized
connective tissues are both found in the body.
Fiber-like structural proteins and
polysaccharides secreted by the cells make up
a matrix (ground substance) around the cells
that can range from hard to liquid.
Connective Tissue
Fibrous connective tissues are strong and
stretchy.


Fibrous connective tissue takes different
forms depending on cell type and the
fibers/matrix produced.
Loose connective
tissue
collagenous
fiber
fibroblast
elastic fiber
Dense, irregular
connective tissue
collagenous
fibers
Dense, regular
connective tissue
collagenous
fibers
Cartilage
ground
substance
with collagen
fibers
fibroblast
cartilage cell
(chondrocyte)
Fig. 4.2a-d, p. 70
Connective Tissue

Types and examples of fibrous connective tissue:
• Loose connective tissue supports epithelia and
organs, and surrounds blood vessels and nerves; it
contains few cells and loosely arrayed thin fibers.
• Dense, irregular connective tissue has fewer cells
and more fibers, which are thick; it forms protective
capsules around organs.
• Dense, regular connective tissue has bundled
collagen fibers lying in parallel; such arrangements are
found in ligaments (binding bone to bone) and tendons
(binding muscle to bone).
• Elastic connective tissue contains fibers of elastin;
this tissue is found in organs that must stretch, like the
lungs.
Animation: Soft Connective Tissues
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Connective Tissue
Cartilage, bone, adipose tissue, and blood
are specialized connective tissues.


Cartilage contains a dense array of fibers in a
rubbery ground substance; cartilage can
withstand great stress but heals slowly when
damaged.
•
•
•
Hyaline cartilage has many small fibers; it is found
at the ends of bones, in the nose, ribs, and windpipe.
Elastic cartilage, because of its elastin component,
is able to bend yet maintain its shape, such as in the
external ear.
Fibrocartilage is a sturdy and resilient form that can
withstand tremendous pressure such as in the disks
that separate the vertebrae.
Connective Tissue


Bone tissue is composed of collagen, ground
substance, and calcium salts; minerals harden
bone so it is capable of supporting and protecting
body tissues and organs.
Adipose tissue cells are specialized for the
storage of fat; most adipose tissue lies just
beneath the skin.
compact
bone tissue
blood vessel
bone cell
(osteocyte)
nucleus
cell bulging
with fat
droplet
TYPE: Bone tissue
TYPE: Adipose tissue
DESCRIPTION: Collagen fibers,
matrix hardened with calcium
DESCRIPTION: Large, tightly packed
fat cells occupying most of matrix
COMMON LOCATIONS: Bones of
skeleton
COMMON LOCATIONS: Under skin,
around heart, kidneys
FUNCTION: Movement, support,
protection
FUNCTION: Energy reserves,
insulation, padding
Fig. 4.2ef, p. 71
Animation: Specialized
Connective Tissues
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Connective Tissue

Blood is a fluid connective tissue involved in
transport; plasma forms the fluid “matrix” and
blood proteins, blood cells, and platelets
compose the “fiber” portion of the tissue.
Figure 4.3
Table 4.2, p. 71
Section 3
Muscle Tissue:
Movement
Figure 4.4
Muscle Tissue: Movement
Muscle tissue contracts in response to
stimulation, then passively lengthens;
movement is a highly coordinated action.
There are three types of muscle: skeletal muscle



Skeletal muscle tissue
attaches to bones for
voluntary movement; long
muscle cells are bundled
together in parallel arrays,
which are enclosed in a
sheath of dense connective tissue.
Figure 4.4a
Muscle Tissue: Movement


Smooth muscle tissue contains
tapered, bundled cells that function
in involuntary movement; it lines
the gut, blood vessels, and glands.
Cardiac muscle is composed of
short cells that can function in units
due to the signals that pass through
special junctions that fuse the cells
together; cardiac muscle is only
found in the wall of the heart.
cardiac
muscle
smooth muscle
Figure 4.4b-c
Animation: Muscle Tissues
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Section 4
Nervous Tissue:
Communication
Nervous Tissue: Communication
Nervous tissue consists mainly of cells,
including neurons (nerve cells) and support
cells; nervous tissue forms the body’s
communication network.
Neurons carry messages.



Neurons have two types
of cell processes (extensions):
branched dendrites pick up
chemical messages and pass
them to an outgoing axon.
Figure 4.5a
Nervous Tissue: Communication


A cluster of processes from different neurons is
called a nerve.
Nerves move messages throughout the body.
 Neuroglia


are support cells.
Glial cells (neuroglia) make
up 90 percent of the nervous
system. Neuroglia provide
physical support for neurons.
Other glial cells provide
nutrition (astrocytes), clean-up,
and insulation services (Schwann cells).
Figure 4.5b
Table 4.4, p. 85
Section 5
Cell Junctions: Holding
Tissues Together
Cell Junctions
Epithelial cells tend to adhere to one
another by means of specialized attachment
sites.




Tight junctions link cells of epithelial tissues to
form seals that keep molecules from freely
crossing the epithelium.
Adhering junctions are like spot welds in
tissues subject to stretching.
Gap junctions link the cytoplasm of adjacent
cells; they form communication channels.
Cell Junctions

Sites of cell-to-cell contact are especially
profuse when substances must not leak
from one body compartment to another.
cell
basement
membrane
intermediate
filaments
plaques
TIGHT JUNCTION ADHERING JUNCTION
protein
channel
GAP JUNCTION
Fig. 4.6, p. 74
Animation: Cell Junctions
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Section 6
Tissue Membranes:
Thin, Sheetlike Covers
Tissue Membranes
Epithelium membranes pair with connective
tissue.




Mucous membranes line the tubes and
cavities of the digestive, respiratory, and
reproductive systems where embedded glands
secrete mucus.
Serous membranes such as those that line the
thoracic cavity occur in paired sheets and do
not contain glands.
Cutaneous membranes are hardy and dry—
and better known as skin.
Tissue Membranes
Membranes in joints consist only of
connective tissue.



Synovial membranes line the sheaths of
tendons and the capsule-like cavities around
certain joints.
Their cells secrete fluid that lubricates the ends
of the moving bones.
mucous
membrane
serous
membrane
cutaneous
membrane
(skin)
synovial
membrane
Fig. 4.7, p. 75
Section 7
Organs and Organ
Systems
Organs and Organ Systems


An organ is a composite of two or more
tissue types that act together to perform one
or more functions; two or more organs that
work in concert form an organ system.
The major cavities of the human body are:
cranial, spinal, thoracic, abdominal, and
pelvic.
cranial cavity
spinal cavity
thoracic cavity
abdominal cavity
pelvic cavity
Fig. 4.8a, p. 76
Animation: Major Body Cavities
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Animation: Directional Terms
and Planes of Symmetry
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SUPERIOR (of two body parts, the one closer to head)
distal (farthest from trunk or
from point of origin of a body
part)
frontal plane
(aqua)
midsagittal
plane
(green)
ANTERIOR
(at or near front of body)
INFERIOR
(of two body parts,
the one farthest from head)
proximal (closest to
trunk or to point of
origin of a body part)
POSTERIOR
(at or near back of body)
transverse
plane
(yellow)
Fig. 4.8b, p. 76
Organs and Organ Systems
 Eleven
organ systems (integumentary,
nervous, muscular, skeletal, circulatory,
endocrine, lymphatic, respiratory, digestive,
urinary, and reproductive) contribute to the
survival of the living cells of the body.
Animation: Organ Systems
of the Human Body
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Section 8
The Integument –
Example of an Organ
System
The Integument
Humans have an outer covering called the
integument, which includes the skin and
the structures derived from epidermal cells
including oil and sweat glands, hair, and
nails.
The skin performs several functions:



The skin covers and protects the body from
abrasion, bacterial attack, ultraviolet radiation,
and dehydration.
The Integument




It helps control internal temperature.
Its receptors are essential in detecting
environmental stimuli.
The skin produces vitamin D.
Epidermis and dermis—the two layers of
skin.
outer
epidermal
layer (all
dead cells)
keratinized
cells being
flattened
rapidly
dividing
cells of
epidermis
dermis
Fig. 4.10b, p. 79
The Integument

Epidermis refers to the thin, outermost layers
of cells consisting of stratified, squamous
epithelium.
•
•
•
Keratinocytes produce keratin; when the cells are
finally pushed to the skin surface, they have died, but
the keratin fibers remain to make the outermost layer
of skin (the stratum corneum) tough and waterproof.
Deep in the epidermis are melanin-producing cells
(melanocytes); melanin, along with carotene and
hemoglobin, contribute to the natural coloration of
skin.
Langerhans cells and Granstein cells are two
important cells in skin that contribute to immune
function.
The Integument

The dermis is the thicker portion of the skin
that underlies the epidermis.
•
•

The dermis is mostly dense connective tissue,
consisting of elastin and collagen fibers.
Blood vessels, hair follicles, nerve endings, and
glands are located here.
The hypodermis is a subcutaneous layer that
anchors the skin; fat is also stored here.
smooth muscle
melanocyte
sweat pore
sebaceous gland
Langerhans cell
keratinized layer
living layer
hair shaft
EPIDERMIS
keratinocyte
Granstein cell
DERMIS
HYPODERMIS
adipose cells
nerve fiber
hair follicle
pressure receptor
sweat gland
Fig. 4.10a, p. 78
Animation: Structure of Human Skin
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The Integument
Sweat glands and other structures are
derived from epidermis.
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

Sweat glands secrete a fluid (mostly water with
a little dissolved salt) that is useful in regulating
the temperature of the body.
Oil (sebaceous) glands function to soften and
lubricate the hair and skin; acne is a condition
in which the ducts become infected by bacteria.
The Integument

Hairs are flexible, keratinized structures rooted in
the skin and projecting above the surface; growth
is influenced by genes, nutrition, and hormones.
Figure 4.11
The Integument
Sunlight permanently damages the skin.




Ultraviolet (UV) radiation and the light from
tanning beds stimulate melanin production in
skin, resulting in a tan; too much UV exposure,
however, can damage the skin.
UV light can activate protooncogenes in skin cells, leading
to cancer.
Rates of skin cancer are on the
rise due to continued destruction
of the atmospheric ozone layer that normally
protects the Earth from too much UV light.
Section 9
Homeostasis: The Body
in Balance
Homeostasis: The Body in Balance
The internal environment: A pool of
extracellular fluid.



The trillions of cells in our bodies are
continuously bathed in an extracellular fluid that
supplies nutrients and carries away metabolic
wastes.
The extracellular fluid consists of interstitial
fluid (between the cells and tissues) and
plasma (blood fluid).
Cell
Interstitial
(tissue) fluid
Blood
Blood
vessel
Extracellular fluid
In-text Fig., p. 80
Homeostasis: The Body in Balance

The component parts of an animal work
together to maintain the stable fluid
environment (homeostasis) required for life.
Homeostasis requires the interaction of
sensors, integrators, and effectors.


Homeostatic mechanisms operate to maintain
chemical and physical environments within
tolerable limits and to keep the body close to
specific set points of function.
Homeostasis: The Body in Balance

Homeostatic control mechanisms require three
components:
•
•
•
Sensory receptor cells detect specific changes
(stimuli) in the environment.
Integrators (brain and spinal cord) act to direct
impulses to the place where a response can be
made.
Effectors (muscles and glands) perform the
appropriate response.
STIMULUS (input into the system)
receptor
integrator
effector
(such as a
nerve ending
in the skin)
(such as
the brain or
spinal cord)
(a muscle
or gland)
RESPONSE to stimulus causes change. The change is “fed back”
to receptor. In negative feedback, the system’s response cancels
or counters the effect of the original stimulus.
Fig. 4.12, p. 80
Homeostasis: The Body in Balance
Feedback mechanisms are important
homeostatic controls.


A common homeostatic mechanism is negative
feedback.
•
•

It works by detecting a change in the internal
environment that brings about a response that tends
to return conditions to the original state.
It is similar to the functioning of a thermostat in a
heating/cooling system.
Positive feedback mechanisms may intensify
the original signal; childbirth is an example.
Animation: Negative Feedback at the
Organ Level
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Animation: Homeostatic Control of
Temperature
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dead, flattened skin cells
sweat gland pore
Fig. 4.13a, p. 81
STIMULUS
After
overexertion
on a hot, dry
day, surface
temperature
of body rises.
RESPONSE
Body temperature
falls,receptors
initiate shifts
in effector output.
receptors
In skin and
elsewhere;
detect the
temperature
change.
effectors
integrator
Pituitary gland
& thyroid gland
trigger
widespread
adjustments in
many body
organs.
The hypothalamus,
a brain region,
compares input
from the receptors
against the set
point for the body.
Effectors
These carry out specific responses, including:
Skeletal
muscles in
chest wall
work to get
additional
oxygen into
lungs.
Smooth muscle in
blood vessels
dilates; blood
transporting
metabolic heat
shunted to skin;
some heat lost to
surroundings.
Sweat
glands
secrete
more,
with cooling
effect on
the brain
especially.
Overall slowing of activity results in
less metabolically generated heat.
Fig. 4.13b, p. 81
Section 10
How Homeostatic
Feedback Maintains the
Body’s Core
Temperature
How Homeostatic Feedback Maintains the
Body’s Core Temperature
Humans are endotherms, heated from
within by metabolic processes.



Core temperature of the head and torso is
roughly 37C (98.6F).
Above this temperature (~41C) proteins begin
to denature; below this temperature (35C and
below) the body stops functioning.
Animation: Human Thermoregulation
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Fig. 4.14a, p. 82
Fig. 4.14b, p. 82
Animation: Heat Denaturation of Enzymes
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How Homeostatic Feedback Maintains the
Body’s Core Temperature
Responses to cold stress.



Cold responses are controlled by an area of the
brain called the hypothalamus.
Several things happen when the outdoor
temperature drops:
•
•
Peripheral vasoconstriction occurs when the
hypothalamus commands the muscles around blood
vessels to contract; this diverts blood flow away from
the body surface.
The pilomotor response causes your body hair to
stand on end to trap air around the body to prevent
heat loss.
How Homeostatic Feedback Maintains the
Body’s Core Temperature
•
•

Skeletal muscle contractions cause you to shiver in
an attempt to generate heat.
In babies, who can’t shiver, hormones raise the rate
of metabolism in a nonshivering heat production
response; this response occurs in a special type of
adipose tissue called brown fat.
If body temperature cannot be maintained,
damage to the body occurs.
•
•
Hypothermia is characterized by mental confusion,
coma, and possibly death.
Physical freezing can lead to frostbite and death of
the affected tissues.
How Homeostatic Feedback Maintains the
Body’s Core Temperature
Responses to heat stress.


Heat responses are also controlled by the
hypothalamus.
•
•
Peripheral vasodilation causes blood vessels to
expand in the skin, allowing excess body heat to
dissipate.
Heat is also dissipated in sweat from sweat glands;
water and salts both are lost to cool the body.
How Homeostatic Feedback Maintains the
Body’s Core Temperature

Various levels of heat stress (hyperthermia)
can be experienced:
•
•

Heat exhaustion occurs under mild heat stress;
blood pressure drops as fluid is lost and the person
can collapse.
Heat stroke occurs when the body ceases to be
able to control temperature; death is one possible
outcome.
A fever is a natural rise in core temperature
used to fight off disease; severe fevers,
however, should be controlled to avoid serious
damage to the body.
Table 4.3, p. 83