Human Biology (BIOL 104)
Talk Four:
Tissues, Organs, and Organ
Systems
Chapter 4
Tissues, Organs, and Organ Systems
• Every year tens of thousands of people develop a disease
or suffer an injury that severely damages an organ or
tissue.
•
If only it were possible to replace those body parts!
• All body cells come from “stem cells” (more in later talks).
– Ah, back to the ethics stuff!!!!!
• Adults also have stem cells (less controversial)
– Adult stem cells are more limited than embryonic cells
– Active types show promise for regenerating cartilage and heart
muscle damaged by a heart attack
• We will focus on the basic types of cells and tissues that
make up the Human Body.
• Tissue:
Tissues
– Similarly specialized cells that perform a
common function in the body.
• 4 main tissue types in the human body:
– 1. Epithelial: covers body surface and lines body
cavities.
– 2. Connective: binds and supports body parts.
– 3. Muscular: Moves body parts
– 4. Nervous: Receives, interprets and sends
signals.
1. Epithelial Tissue
• This covers the whole surface of the body.
• It is made up of cells closely packed and ranged in one or more layers.
– This tissue is specialized to form the covering or lining of all internal
and external body surfaces.
• Epithelial tissue that occurs on surfaces on the interior of the body is
known as endothelium.
• Epithelial cells are packed tightly together, with almost no intercellular
spaces and only a small amount of intercellular substance.
• Epithelial tissue, regardless of the type, is usually separated from the
underlying tissue by a thin sheet of connective tissue; basement
membrane.
• The basement membrane provides structural support for the
epithelium and also binds it to neighboring structures.
1. Epithelial Tissue
• 5 types:
• A: Squamous-flat-lungs
and blood.
• B: Cuboidal-cube-kidney
tubes.
• C: Columnar-pillarsDigestive tract.
• D: Pseudostratified
ciliated columnarRespiratory tract.
• E: Stratified squamous
epithelium - esophagus
Used with permission from imgarcade.com
Functions of Epithelial Tissue
• Protection
– Epithelial cells from the skin protect underlying tissue from
mechanical injury, harmful chemicals, invading bacteria and
from excessive loss of water.
• Sensation
– Sensory stimuli penetrate specialised epithelial cells.
Specialised epithelial tissue containing sensory nerve endings
is found in the skin, eyes, ears, nose and on the tongue.
• Secretion
– In glands, epithelial tissue is specialised to secrete specific
chemical substances such as enzymes, hormones and
lubricating fluids.
• Absorption
– Certain epithelial cells lining the small intestine absorb
nutrients from the digestion of food.
Functions of Epithelial Tissue
• Excretion
– Epithelial tissues in the kidney excrete waste products from the
body and reabsorb needed materials from the urine. Sweat is also
excreted from the body by epithelial cells in the sweat glands.
• Diffusion
– Simple epithelium promotes the diffusion of gases, liquids and
nutrients. Because they form such a thin lining, they are ideal for
the diffusion of gases (eg. walls of capillaries and lungs).
• Cleaning
– Ciliated epithelium assists in removing dust particles and foreign
bodies which have entered the air passages.
• Reduces Friction
– The smooth, tightly-interlocking, epithelial cells that line the
entire circulatory system reduce friction between the blood and
the walls of the blood vessels.
Cleaning, an extended example the Trachea
• Windpipe – connects
larynx to primary
bronchi.
• Held open by cartilage
• Goblet cell
– Makes mucus
• Mucosa contains layer of
pseudostratified ciliated
epithelium
– Sweep dirt and excess
mucus upwards
Basement Membrane
• Why doesn't our skin fall completely off our bodies?
• The results of gravity's constant downward pull on our
faces, shoulders, backs, necks, chests, organs, legs and feet
are obvious to most of us, especially as we age.
• Nowhere is this more obvious than our skin. Millions of
dollars are spent every year to tighten that sagging,
drooping skin.
• The occasional face-lift, a little Botox, creams, serums, and
muscle exercises are part of this nations obsession.
• Meet the basement membrane.
– Epithelial Tissue is held to the body via a Basement membrane
Basement Membrane
• The basement membrane serves as the
anchor for the epithelium, attaching it to
the connective tissue below.
• Your skin has three layers. The outer
layer, called the epidermis, is composed
of epithelial cells.
• The middle layer is the dermis, and is
composed of connective tissue such as
– blood vessels, sweat glands, sebaceous glands,
and temperature sensors.
– The third layer is the subcutaneous, and is the
lowest layer.
• The basement membrane lies between the
epidermis and the dermis, keeping the
outside layer tightly connected to the
inside layer.
From the wikimedia free licensed
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Basement Membrane
• Not even the effects of gravity can
destroy this anchoring system.
– While skin may droop and sag, it will never
completely fall off.
• Basement membrane is not found just in
the skin.
– It has important functions all over the body.
• Any place you find epithelium and
endothelium, the basement membrane will
be sandwiched in between to hold the
layers together.
• Basement membrane is composed of:
– glycoproteins-sticky sugary proteins and
protein fibers:
• Collagen:
– strong, elastic-stretchy
From the wikimedia free licensed
media file repository
2. Connective Tissue
• Supports, connects, or separates different types of
tissues and organs of the body.
• Contains high quantities of a protein called collagen
• Connective tissue proper consists of loose connective
tissue and dense connective tissue (which is further
subdivided into dense regular and dense irregular
connective tissues.)
• Special connective tissue consists of reticular connective
tissue, adipose tissue, cartilage, bone, and blood.
• Other kinds of connective tissues include fibrous, elastic,
and lymphoid connective tissues.
2. Connective Tissue
• Dense connective tissue
– In skin and capsules around organs
– used as a support structure
• Adipose connective tissue
– Mainly cells filled with fat- under
skin and kidneys
– Energy reserve, insolation, and
padding
• Areolar connective tissue
– Found under the skin – Elasticity
and diffusions of solutes
• Compact bone
– Movement, support, and protection
• Blood
– Fluid blood plasma
From the wikimedia free licensed
media file repository
Functions of connective tissue
• Storage of energy
• Protection of organs
• Provision of structural framework for the body
• Connection of body tissues
• Connection of epithelial tissues to muscle fiber.
• Supply of hormones all over the body
• Nutritional support to epithelium
• Site of defense reactions
• Repair of body tissues
Diseases of connective tissue
•
Scurvy – problems with sea voyages,
lack of food other than salted meats.
– Symptoms include, swollen gums,
loose teeth, small black-and-blue
spots on the skin, and bleeding from
small blood vessels are among the
characteristic signs of scurvy.
– Caused when vitamin C (ascorbic
acid) is lost from diet
– Vitamin C is needed to keep Iron
reduced in blood cells to carry
oxygen
– In 1795, the British Royal Navy
provided a daily ration of lime or
lemon juice to all its men. English
sailors to this day are called
"limeys", for lime was the term used
at the time for both lemons and
limes.
From the wikimedia free licensed media
file repository
Diseases of connective tissue

Several heritable diseases result from mutations in
the collagen
Marfan’s Syndrom and
Ehler’s-Danlos syndromes inherited disorder of
connective tissue which
affects many organ systems,
including the skeleton, lungs,
eyes, heart and blood vessels.
All resulting from various
mutation in collagen and
other fibril associated
proteins, ultimately affecting
the structure and molecular
interaction of connective
tissue.
3. Muscle tissue
• Is a soft tissue that composes muscles in bodies, and gives
rise to muscles' ability to contract. This is opposed to
other components or tissues in muscle such as tendons
• Muscle tissue varies with function and location in the body.
In mammals the three types are:
• skeletal or striated muscle
• smooth or non-striated muscle
• cardiac muscle, which is sometimes known as semistriated
• Smooth and cardiac muscle contracts involuntarily,
without conscious intervention.
Skeletal or striated muscle
• Striated in structure and under
voluntary control, is anchored
by tendons to bone and is used to
effect skeletal movement such as
locomotion and to maintain
posture.
• An average adult male is made up
of 42% of skeletal muscle and an
average adult female is made up
of 36% (as a percentage of body
mass).
From the wikimedia free licensed media file
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Smooth or non-striated muscle
• Smooth muscle, neither striated
in structure nor under voluntary
control, is found within the walls
of organs and structures such as
the:
•
•
•
•
•
•
•
•
•
esophagus
stomach
intestines
bronchi
uterus
urethra
bladder
blood vessels
arrector pili in the skin (in which
it controls erection of body
hair).
From the wikimedia free licensed media file
repository
Cardiac Muscle
• Cardiac muscle (myocardium),
found only in the heart, not
subject to voluntary control.
• Cardiac "striated" in that they
contain sarcomeres and are
packed into highly regular
arrangements of bundles; smooth
muscle has neither.
• While skeletal muscles are
arranged in regular, parallel
bundles, cardiac muscle connects
at branching, irregular angles
(called intercalated discs).
• Heart cells must beat in unison.
Intercalated Disks allow calcium
to regulate united beating
From the wikimedia free licensed media file
repository
4. Nervous Tissue
• The main component of the two
parts of the nervous system;
the brain and spinal cord of the
central nervous system (CNS),
and the branching peripheral
nerves of the peripheral nervous
system (PNS)
• Both regulate and control bodily
functions and activity.
• It is composed of
– neurons, or nerve cells, which
receive and transmit impulses
– neuroglia, also known as glial
cells or more commonly as just
glia.
From the wikimedia free licensed media file
repository
4. Nervous Tissue
• Glia assist the propagation of
the nerve impulse as well as
providing nutrients to the
neuron.
• Nervous tissue is made up of
different types of nerve cells,
all of which having an axon, the
long stem-like part of the cell
that sends action potential
signals to the next cell.
• Functions of the nervous system
are sensory input, integration,
control of muscles and glands,
homeostasis, and mental
activity.
From the wikimedia free licensed media file
repository
4. Nervous Tissue
Tissues require cell junctions
• Type of structure that exists within the tissue of some
multicellular organisms, such as Humans.
• Consist of multiprotein complexes that provide contact
between neighbouring cells or between a cell and the
extracellular matrix.
• They also build up the paracellular barrier of epithelia and
control the transport of solutes. Cell junctions are
especially abundant in epithelial tissues.
• Cell junctions are especially important in enabling
communication between neighboring cells via specialized
proteins called communicating junctions. Cell junctions are
also important in reducing stress placed upon cells.
Three types
• A: Adhesion junction
• Cells within tissues and organs
must be anchored to one
another and attached to
components of the
extracellular matrix.
• Anchoring proteins extend
through the plasma membrane
to link cytoskeletal proteins in
one cell to cytoskeletal
proteins in neighboring cells
as well as to proteins in the
extracellular matrix
Three types
• B: Tight junction
• Found in epithelia, they act as
barriers that regulate the
movement of water and solutes
between epithelial layers.
• There is evidence to suggest
that the structures in which
solutes pass through are
somewhat like pores.
• Prevent the highly acidic gastric
fluid in your stomach from
leaking out and digesting
proteins of your own body
instead of those you consume as
food.
Three types
• C: Communicating (GAP)
junctions
•
Allow for direct chemical
communication between adjacent
cellular cytoplasm through diffusion
without contact of the extra cellular
fluid.
•
Protrudes across the cell membrane,
and when 2 adjacent cells interact,
they form the gap junction channel.
•
Play vital roles in the human body,
including their role in the uniform
contractile of the heart muscle.
•
They are also relevant in signal
transfers in the brain, and their
absence shows a decreased cell density
in the brain.
•
Retinal and skin cells are also
dependent on gap junctions in cell
differentiation and proliferation.
Organs and Organ
Systems
•
An organ is a collection of tissues
joined in a structural unit to serve a
common function
•
Organs are composed of main tissue,
parenchyma, and "sporadic" tissues,
stroma.
•
The main tissue is that which is unique
for the specific organ, such as the
specialized cells of the stomach,
•
Sporadic tissues include the nerves,
blood vessels, and connective tissues.
•
Functionally related organs often
cooperate to form whole organ systems.
•
A hollow organ is a visceral organ that
forms a hollow tube or pouch, such as
the stomach or intestine, or that
includes a cavity, like the heart or
urinary bladder
Used with permission from imgarcade.com
Organ Systems
•
1. Circulatory System: The main function of
this system is to transport nutrients and
gasses to cells and tissues throughout body.
This is accomplished by the circulation of
blood.
•
Cardiovascular: comprised of the heart,
blood, and blood vessels. The beating of the
heart drives the cardiac cycle which pumps
blood throughout body.
•
Cardiovascular organs:
– heart, blood vessels, blood
•
Lymphatic: This system is a vascular
network of tubules and ducts that collect,
filter, and return lymph to blood circulation.
•
As a component of the immune system, the
lymphatic system produces and circulates
immune cells called lymphocytes.
•
Lymphatic organs:
– lymph vessels, lymph nodes, thymus,
spleen, tonsils
From the wikimedia free licensed media
file repository
•
2. Digestive System: This system breaks
down food polymers into smaller molecules to
provide energy for the body.
•
Digestive juices and enzymes are secreted
to break down the carbohydrates, fat, and
protein in food.
•
Primary organs:
– mouth, stomach, intestines, rectum
•
Accessory organs:
– teeth, tongue, liver, pancreas
•
3. Endocrine System: This system regulates
vital processes in the body including growth,
homeostasis, metabolism, and sexual
development. Endocrine organs secrete
hormones to regulate body processes.
•
Endocrine structures:
– pituitary gland, pineal gland, thymus,
ovaries, testes, thyroid gland
Organ Systems
From the wikimedia free licensed media file repository
Organ Systems
• 4. Integumentary System: This
system protects the internal
structures of the body from
damage, prevents dehydration,
stores fat and produces vitamins
and hormones.
• Integumentary structures:
– skin, nails, hair, sweat glands
• 5. Muscular System: This system
enables movement through the
contraction of muscles.
• Structures:
– muscles
Organ Systems
•
6. Nervous System: This system
monitors and coordinates internal organ
function and responds to changes in the
external environment
•
Structures:
•
7. Reproductive System: This system
enables the production of offspring
through sexual reproduction.
•
It is comprised of male and female
reproductive organs and structures
which produce sex cells and ensure the
growth and development of offspring.
•
Male organs:
•
Female organs:
– brain, spinal cord, nerves
– testes, scrotum, penis, vas
deferens, prostate
– ovaries, uterus, vagina,
mammary glands
Organ Systems
• 8. Respiratory System: This
system provides the body with
oxygen via gas exchange between
air from the outside environment
and gases in the blood.
• Respiratory organs:
– lungs, nose, trachea, bronchi
• 9. Skeletal System: This system
supports and protects the body
while giving it shape and form.
• Structures:
– bones, joints, ligaments,
tendons, cartilage
Both diagrams used with permission
from imgarcade.com
•
10. Urinary/Excretory Systems:
consists of the kidneys, ureters,
urinary bladder, and urethra.
•
The kidneys filter the blood to
remove wastes and produce urine.
•
The ureters, urinary bladder, and
urethra together form the urinary
tract, which acts as a plumbing
system to drain urine from the
kidneys, store it, and then release
it during urination.
•
Besides filtering and eliminating
wastes from the body, the urinary
system also maintains the
homeostasis of water, ions, pH,
blood pressure, calcium and red
blood cells
•
Structures:
Organ Systems
– kidneys, urinary bladder,
urethra, ureters
Used with permission from imgarcade.com
Organs and
Organ Systems
• It is important to keep in
mind that these organ
systems don't just exist as
individual units.
• The final product of these
cooperating systems is one
unit called the body.
• Each system depends on the
others, either directly or
indirectly, to keep the body
functioning normally.
Used with permission from imgarcade.com
The Skin: an example of an organ system
• The skin is the largest organ
in the human body.
• For the average adult human, the
skin has a surface area of between
1.5-2.0 square meters (16.1-21.5 sq
ft.), most of it between 2–3 mm
(0.10 inch) thick.
• On average it weighs about 9 pound
• The average square inch (6.5 cm²)
of skin holds:
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650 sweat glands
20 blood vessels
60,000 melanocytes
more than 1,000 nerve endings
The Skin: an example of an organ system
• Skin performs the following
functions:
• Protection: an anatomical barrier
from pathogens and damage
between the internal and external
environment in bodily defense;
• Sensation: contains a variety of
nerve endings that react to heat
and cold, touch, pressure, vibration,
and tissue injury
• Heat regulation: Dilated blood
vessels increase perfusion and heat
loss, while constricted vessels
greatly reduce cutaneous blood flow
and conserve heat.
The Skin: an example of an organ system
• Control of evaporation: the skin
provides a relatively dry and semiimpermeable barrier to fluid loss.
– Loss of this function contributes to the
massive fluid loss in burns.
• Aesthetics and communication:
Some trained professionals see our
skin and can assess our mood,
physical state and attractiveness.
• Storage and synthesis: acts as a
storage center for lipids and water,
as well as a means of synthesis of
vitamin D by action of UV on certain
parts of the skin.
The Skin: an example of an organ system
• Excretion: sweat contains urea,
however its concentration is
1/130th that of urine, hence
excretion by sweating is at most a
secondary function to temperature
regulation.
• Absorption: the cells comprising
the outermost 0.25–0.40 mm of the
skin are "almost exclusively supplied
by external oxygen", although the
"contribution to total respiration is
negligible".
• Water resistance: The skin acts as
a water resistant barrier so
essential nutrients aren't washed
out of the body.
Homeostasis
• Homeostasis is the property of
a system in which variables are
regulated so that internal
conditions remain stable and
relatively constant.
•
Examples of homeostasis
include the regulation of:
– temperature
– balance between acidity and
alkalinity (pH).
• It is a process that maintains
the stability of the human
body's internal environment in
response to changes in
external conditions.
From the wikimedia free licensed media file
repository