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Chapter 20
UNIFYING CONCEPTS OF
ANIMAL STRUCTURE AND
FUNCTION
I. Life is based on many structural levels
Levels of animal structure:
 Atoms
and molecules
 Cells
 Tissues
 Organs
 Organ
systems
 Organism: May consist of a single cell or a
complex multicellular organism.
Levels of Structural Organization in an Animal
TISSUES:
 Most
animal cells are organized into tissues.
 Cooperative
unit of very similar cells that perform
a specific function.
 Tissue
 Cells
comes from Latin word meaning “weave”.
of tissues may be held together by:
 Fibers
 Glue-like
 Plasma
 Tissue
substance
membrane structures
structure is related to its function.
TISSUES:
There are four main types of animal
tissue:
1. Epithelial
2. Connective
3. Muscle
4. Nervous
1. Epithelial Tissue
 Cells
are tightly fitted together in continuous
layers or sheets.
 Cover outside of body (skin), line organs and
internal body cavities (Mucous membranes of
digestive, respiratory, and reproductive systems).
 Tight packaging allows tissue to act as a barrier
to protect against mechanical injury, infection,
and fluid loss.
 Two surfaces:
 Free
surface: Exposed to air or fluid.
 Bottom surface: Attached to underlying tissues by a
basement membrane, a dense layer of protein and
polysaccharides.
1. Epithelial Tissue
Can be classified based on two criteria:
A. Number of layers:
 Simple:
One layer.
 Stratified: Several layers
B. Shape of cells:
 Squamous:
Flat cells.
 Cuboidal: Cube shaped cells
 Columnar: Column shaped cells
Example:
 Simple
squamous epithelium
 Stratified columnar epithelium
Epithelial Tissue Covers and Lines the Body and its Parts
A. Simple squamous
(Lung air sacs)
D. Statified squamous
(Lining esophagus)
B. Simple cuboidal
(Kidney tubes)
C. Statified columnar
(Lining intestine)
1. Epithelial Tissue
Some epithelial tissues, such as mucous membranes,
absorb and secrete chemical solutions.
 Mucous membranes:
 Digestive
tract epithelium (mucous membranes)
secretes mucus and digestive enzymes.
 Respiratory tract epithelium secretes mucous that
helps trap dust particles before they reach the lungs.
2. Connective Tissue
 Relatively
few cells surrounded by large amounts
of nonliving material (matrix).
 Cells secrete the matrix, which can be solid,
liquid, or gelatinous.
 Diverse functions. Mainly bind, support, and
connect other tissues.
 Six types of connective tissue in humans:
1. Loose Connective Tissue: Most widespread connective
tissue in vertebrates. Loose matrix with fibers,
packing material. Attaches skin to muscles, binds and
holds tissues and organs in place.
2. Adipose (fat): Pads and insulates body. Energy
storage.
Connective Tissue Binds and Provides Support
A. Loose Connective Tissue
B. Adipose Tissue
C. Blood
D. Fibrous Connective Tissue
E. Cartilage
F. Bone
Types of connective tissue in humans (Continued):
C. Blood: Fluid matrix (plasma) has water, salts, and
proteins. Red and white blood cells.
D. Fibrous Connective Tissue: Matrix of densely packed
collagen fibers. Strong and nonelastic. Found in:
• Tendons: Attach muscles to bones.
• Ligaments: Attach bone to bone.
E. Cartilage: Rubbery matrix with collagen fibers.
Found on end of bones, nose, ears, and between
vertebra.
F. Bone: Supports the body of most vertebrates. Solid
matrix of collagen fibers and calcium, phosphate, and
magnesium salts. Bone is harder than cartilage, but not
brittle because of collagen.
3. Muscle Tissue
 Most
abundant type of tissue in most animals.
Accounts for two-thirds (2/3) of human weight.
 Specialized for contraction. Made up of long cells
that contract when stimulated by nerve impulses.
 Muscle cells have many microfilaments made up
of actin and myosin.
 Muscle contraction accounts for much of energy
consuming work in animals.
 Adults have a fixed number of muscle cells.
Weight lifting doesn’t increase number of muscle
cells, only their size.
3. Muscle Tissue
There are three types of muscle tissue:
A. Skeletal (striated) muscle : Attached to bones by
tendons.
Responsible for voluntary movements.
B. Cardiac muscle: Forms contractile tissue of heart.
Not under voluntary control.
C. Smooth muscle: Found in walls of digestive tract,
bladder, arteries, uterus, and many internal organs.
Responsible for peristalsis and labor contractions.
Contract more slowly than skeletal muscle, but can
remain contracted longer.
Not under voluntary control.
Three Types of Muscle
B. Cardiac muscle
A. Skeletal muscle
C. Smooth muscle
4. Nervous Tissue
 Senses
stimuli and transmits signals from one
part of the animal to another.
 Controls the activity of muscles and glands, and
allows the animal to respond to its environment.
 Neuron: Nerve cell. Structural and functional
unit of nervous tissue. Consists of:
body : Contains cell’s nucleus.
 Dendrite: Extension that conveys signals towards the
cell body.
 Axon: Extension that transmits signals away from the
cell body.
 Cell
 Supporting
neurons.
cells: Nourish, protect, and insulate
Nervous Tissue Forms a Communication Network
Organs are made up of different tissues
Organ:
Several tissues that act as a unit
and together perform one or more
biological functions.
 Perform
functions that component tissues can’t
carry out alone.
Example: The heart is an organ made up of:
• Muscle Tissue: Contraction
• Epithelial Tissue: Lines heart chambers to prevent
leakage and provide a smooth surface.
• Connective Tissue: Makes heart elastic and
strengthens its walls and valves.
• Nervous Tissue: Direct heart contractions.
Organs are Made of Several Different Tissues
Animals Regulate their Internal
Environment
Homeostasis:
 Internal
“Steady state”.
environment of animal remains fairly
constant despite changes in the external
environment.
 Control systems maintain internal conditions
within a range in which life’s metabolic
activities can occur.
 Homeostasis is a dynamic state resulting from
changes in the outside environment and
internal control mechanisms that oppose such
changes.
Homeostatic Mechanisms Counteract Changes
in External Conditions
Animals Regulate their Internal
Environment
Homeostasis:
 Maintained
by negative feedback mechanisms.
 A change in one condition (e.g.: low body
temperature), results is a response that
counteracts that change (e.g.: shivering, etc.).
 Internal conditions regulated by negative
feedback:
•
•
•
•
Body temperature (Normal range: 97 - 100oF)
Salt concentration
pH
Blood levels of sugar, calcium, oxygen, etc.
Negative Feedback as Homeostatic Mechanism
Body Temperature is Regulated by Homeostasis
Major Organ Systems in Mammals
 Digestive
system
 Respiratory system
 Circulatory system
 Cardiovascular
 Lymphatic
 Excretory
and Immune system
system
 Endocrine system
 Reproductive system
 Nervous system
 Muscular system
 Skeletal system
 Integumentary
1. Digestive System
Components: Mouth, salivary glands, throat,
esophagus, stomach, intestines, liver, gallbladder,
pancreas, rectum, and anus.
Functions:
 Ingest
and mechanically break down food.
 Digest food: Stomach and small intestine mainly.
 Absorb nutrients and water.
 Eliminate waste.
Homeostatic Roles:
 Supplies
energy for life’s activities.
 Supplies building blocks for macromolecules
Human Digestive System
2. Respiratory System
Components: Nose, throat, larynx, trachea,
bronchi, and lungs.
Functions:
 Exchange


gases with the environment:
Supplies blood with oxygen.
Disposes of carbon dioxide (waste product from cellular
respiration).
Homeostatic Roles:
 Regulates
blood pH.
 Regulates blood oxygen and carbon dioxide levels.
Human Respiratory System
3. Cardiovascular System
Components: Blood, heart, arteries, veins, and
capillaries.
Functions:
 Exchange


gases with the respiratory system.
Supplies tissues with oxygen.
Removes carbon dioxide from tissues.
 Transports
materials (nutrients, hormones, etc.) inside
body.
 Defends against infection.
Homeostatic Roles:
 Provides
nutrients and removes waste materials from
tissues.
 Regulates body temperature, water and ion balance.
Human Cardiovascular System
4. Lymphatic and Immune System
Components: Lymph, lymphatic vessels, bone
marrow, thymus, spleen, and lymph nodes.
Functions:
 Defends
against infection: bacteria, fungi, viruses, etc.
 Destruction of cancer and foreign cells.
 Synthesis of antibodies and other immune molecules.
 Synthesis of white blood cells.
Homeostatic Role:
 Returns
fluid and proteins that have leaked from
blood capillaries into tissues.


Up to 4 liters of fluid every day.
Fluid returned near heart/venae cavae.
Lymphatic and Immune Systems
5. Excretory (Urinary) System
Components: Kidneys, bladder, urethra, and
associated ducts.
Functions:
 Kidneys
remove nitrogen containing waste from blood.
 Urine with waste is temporarily stored in bladder.
 Excretion of urine.
Homeostatic Role:
 Regulates
water levels in body.

Removes excess water

Helps conserve water
Human Excretory System
6. Endocrine System
Components: Pituitary, adrenal, thyroid, thymus,
pancreas, ovaries, testes, and other ductless
glands.
Functions:
 Produce





hormones that regulate:
Blood chemistry: Levels of sugars, minerals, etc.
Reproduction
Growth
Metabolism
Digestion
Homeostatic Role:
 With
nervous system, regulates metabolism and blood
chemistry.
Human Endocrine System
7. Reproductive System
Components:
Female: Ovaries, oviduct, uterus, vagina, and
associated structures
Male: Testes, seminal vesicles, prostate, urethra,
penis, and associated structures.
Functions:
 Only
organ system that is not essential for individual
survival.
 Continuation of species.
 Gamete formation (eggs and sperm cells).
Homeostatic Role:
 Maintains
secondary sexual characteristics.
Male Reproductive System
Female Reproductive System
Gamete Formation Occurs in Testis
8. Nervous System
Components: Brain, spinal cord, nerves, sense
organs, and associated structures.
Functions:
 Works
with endocrine system to coordinate body
activities.
 Integrates and processes information from sense
organs.
 Sends signals (instructions) to muscles and glands.
 Responds to internal stimuli.
Homeostatic Role:
 Regulates
system.
most organ activities along with endocrine
Human Nervous System
Nervous System Allows Us to Respond to Our Environment
9. Muscular System
Components: Skeletal muscles.
Functions:
Skeletal muscle contraction allows for voluntary
movement:
 Movement
and locomotion.
 Mechanical work: Lifting, pulling, pushing objects.
 Communication: Body language and facial expression.
Homeostatic Role:
 Allows
animals to respond to and control their
environment.
Muscular System: Skeletal Muscle Allows
Voluntary Movement
10. Skeletal System
Components: Bones, ligaments, and cartilage.
Functions:
 Along


with muscular system:
Movement and locomotion.
Mechanical work: Lifting, pulling, pushing objects.
 Body
support.
 Protection of delicate internal organs (brain, heart,
lungs, etc.)
 Calcium storage
Homeostatic Role:
 Helps
maintain constant blood calcium levels.
Skeletal System: Protection, Movement, & Support
11. Integumentary System
Components: Hair, skin, and nails.
Functions:
 Protects the body from:
 Infection:
Barrier to microbes.
 Mechanical injury
 Excessive heat or cold: Thermoregulation
 Water loss

Communication:
 Receives
stimuli from environment
 Gives out subtle signals (blushing, etc.).
Homeostatic Role:
 Helps
maintain constant body temperature.
Integumentary System: Skin, Nails, & Hair
Organ systems must be coordinated for
animal to survive
 Organ
systems interact with one another in
order to maintain fairly stable conditions
(homeostasis) that are required for life.
 Example: Interactions between:
• Respiratory
• Circulatory
• Digestive
Relationships Between Several Major Organ Systems