BIOL 2312.003
Introduction to Modern Biology II
Dr. Mazambani
Spring 2024
Lecture 1 – Chapter 38
Introduction to Animal Organization and
Physiology
Understanding organisms
• Anatomy is the study of the structures of
organisms
– What does it look like?
– What is it made of?
• Physiology is the study of the functions of
organisms
– What does it do?
– How does it do it?
– What is its purpose?
 Homeostasis
Cells
•
Cells are the basic structural
and functional units of all living
organisms
•
Cells carry out the essential
processes of life.
• Movement
• Reproduction
• Sensitivity
• Nutrition
• Excretion
• Repiration
• Growth
Multicellular Organisms
• Can create an internal environment
– fluid that supplies all the needs of individual cells:
• nutrient supply
• waste removal and
• osmotic balance
– allows occupation of diverse external environments that would be lethal to
single cells
• can become relatively large
– because their individual cells are small enough to exchange materials with the
internal environment
• major life functions to be subdivided among specialized groups of cells
– with each group concentrating on a single activity
Question
Multicellularity allows major functions to be subdivided among
specialized groups of cells. Why is this beneficial?
Requirements of individual animal cells
Must be surrounded by an aqueous solution containing ions and molecules in concentrations that maintain osmotic
balance
Organic molecules as an energy source
Oxygen for oxidative reactions
Removal of waste molecules and other by-products
Environmental conditions within tolerable limits
Levels of organization
A tissue is a group of cells with the same
structure and function, working together as a
unit to carry out one or more specialized
activities
An organ integrates two or more different
tissues into a structure that carries out a
specific function (e.g., eye, liver)
An organ system (body system) coordinates
the activities of two or more organs to carry
out a major body function such as
movement, digestion, or reproduction
Animal Tissues
• The structure and function of a tissue is
determined by:
– Properties of the individual cells that
make up the tissue
– Structure and organization of the
cytoskeleton
– Type and organization of the
extracellular matrix (ECM) surrounding
the cell
– The junctions holding cells together
Types of Cell Junctions
• Anchoring junctions form buttonlike spots or
belts that weld cells together – most abundant
in tissues subject to stretching, such as skin
and heart muscle
• Tight junctions seal spaces between cells,
keeping molecules and ions from leaking
between cells – e.g. in tissue lining the urinary
bladder
• Gap junctions open channels between cells in
the same tissue, allowing ions and small
molecules to flow freely from one to another –
e.g., between muscle cells
Animals have four basic
tissue types:
Animal Tissues
• epithelial
• connective
• muscle
• nervous
Question
There are 4 primary tissue types, based on structure and function
Cell Functions
Organ system:
A set of organs that
interacts to carry out a
major body function
Organ:
Body structure that integrates different
tissues and carries out a specific
function
Stomach
Epithelial tissue:
Protection, secretion,
and absorption
Connective tissue:
Structural support
Muscle tissue:
Movement
Nervous tissue:
Communication,
coordination,
and control
Stepped Art
Epithelial Tissues
• Consist of sheet-like layers of cells,
usually connected by tight junctions
with little extra cellular matrix (ECM)
between them
• Cover body surfaces and the
surfaces of internal organs, and line
cavities and ducts within the body
Epithelial Tissue Organization
The epithelium’s outer, apical surface may be
exposed to water, air, or fluids within the body
The inner, basal surface adheres to a layer of
ECM secreted by epithelial cells called the basal
lamina, which fixes the epithelium to
underlying connective tissues
Epithelial Tissue Apical Features
• In internal cavities and ducts, the apical surface
is often covered with cilia, which move fluids
through the cavity or duct (e.g., epithelium
lining the oviducts in mammals)
• In some epithelia, including the lining of the
small intestine, the free surface is covered with
microvilli – fingerlike extensions of the plasma
membrane that increase the area available for
secretion or absorption
Types of Epithelium
Epithelia are classified as
• simple (formed by a
single layer of cells) or
• stratified (formed by
multiple cell layers)
Cell shapes within an
epithelium may be
• squamous (flattened)
• cuboidal (cube-shaped)
• columnar (elongated)
Four principal types of
epithelium are found in
the body:
• simple squamous
epithelium
• stratified squamous
epithelium
• cuboidal epithelium
• columnar epithelium
Simple Squamous Epithelium
• Description: Layer of flattened cells
• Common locations: Blood vessel walls; air sacs of
lungs
• Function: Diffusion
Stratified Squamous Epithelium
• Description: Several layers of flattened cells
• Common locations: Skin and other surfaces subject to abrasion, such
as the mouth, esophagus, and vagina
• Function: Protection against abrasion; typically not involved in
secretion or absorption
Cuboidal Epithelium
• Description: Layer of cube-like cells; free surface
may have microvilli
• Common locations: Glands and tubular parts of
nephrons in kidneys
• Function: Secretion, absorption
Columnar Epithelium
• Description: Layer of tall, slender cells;
free surface may have microvilli
• Common locations: Lining of gut and
respiratory tract
• Function: Secretion, absorption
Epithelial Stem Cells
Some epithelial cells divide constantly –
new cells are produced by division of
stem cells in the basal layer of the skin
Stem cells are undifferentiated cells that
divide to produce more stem cells or
differentiating cells that become
specialized body cells
Stem cells are found in adults and
embryos – adult stem cells are also found
in the brain, bone marrow, blood vessels,
skeletal muscle, and liver
Glands
• Epithelia give rise to cells specialized
for secretion – some are scattered
among nonsecretory cells within the
epithelium, others form glands
• Endocrine glands are ductless – they
release hormones which are
distributed by the circulatory system
(e.g., pituitary gland, adrenal gland,
and thyroid gland)
• Exocrine glands are connected to the
epithelium by a duct, which empties
their secretion at the epithelial
surface (e.g., mucus, saliva, sweat,
earwax, oils, and milk)
Question
Identify the different types of squamous epithelia below
Connective Tissue
• Connective tissues consist of cells that form networks or
layers in and around body structures.
• Functions: provide support, protection, connecting
structures, storage of fats, producing blood cells, aiding
tissue repair.
• Mechanical properties depend on type and quantity of
extracellular matrix (ECM) present in the tissue.
• Many forms of connective tissue have more ECM (by
weight and volume) than cellular material
• Connective tissues contain several cell types. Most
common cell type is the fibroblast which secretes proteins
in the ECM. These proteins assemble into fibers
Six Types of Connective Tissues
Extra-Cellular Matrix (ECM)
Mechanical properties of a connective tissue depend on the type and quantity of its ECM
Consistency of ECM ranges from fluid (blood and lymph), through firm gels (tendons), to hard
and crystalline (bone)
Extracellular Matrix proteins
• ECM in most connective tissues consists primarily of the
fibrous glycoprotein collagen embedded in a network of
proteoglycans
• In bone, the glycoprotein network is impregnated with
mineral deposits that produce a hard, somewhat elastic
structure
• Another family of glycoproteins, fibronectin, aids in
attachment of cells to ECM and helps hold cells in position
• Elastin fibers help some connective tissues return to their
original shape when pulled or stretched (e.g., skin, lungs)
• The protein resilin, found only in insects and some
crustaceans, is the most elastic material known
Loose Connective Tissue
• Loose connective tissue consists of
sparsely distributed fibroblast cells
surrounded by an open network of
collagen and other glycoprotein fibers
• Loose connective tissues support
epithelia and form a band around
blood vessels, nerves, and some
internal organs – they also reinforce
deeper layers of the skin
• Sheets of loose connective tissue form
mesenteries, which hold abdominal
organs in place and provide lubricated,
smooth surfaces that prevent chafing
or abrasion
Dense Connective Tissue
• Fibroblasts are sparsely distributed among
dense masses of collagen and elastin fibers that
are lined up in highly ordered, parallel bundles
• The parallel arrangement produces maximum
tensile strength and elasticity
• Examples: tendons, ligaments, cornea of the
eye
• Function: Strength, elasticity
Cartilage
• Cartilage consists of sparsely distributed chondrocytes surrounded by
networks of collagen fibers embedded in a tough elastic matrix of the
glycoprotein chondroitin sulfate
• Elastin is also present in some forms of cartilage – elasticity allows
cartilage to resist compression and stay resilient
• In humans, cartilage is found in the ears, nose, larynx, trachea,
intervertebral disks, and ends of bones in joints
• Cartilage also serves as a precursor to bone during embryonic
development
• Common locations: Ends of long bones, ears, nose, parts of airways,
skeleton of vertebrate embryos
• Function: Support, flexibility, low-friction surface for joint movement
Bone
Bone forms the skeleton, which supports and
protects the body and contributes to body
movements
Mature bone consists primarily of osteocytes
embedded in an ECM containing collagen fibers and
glycoproteins impregnated with hydroxyapatite
Bone is reshaped continuously by osteoblasts, which
produce collagen and minerals, and osteoclasts,
which remove minerals and recycle them through the
bloodstream
This Photo by Unknown Author is licensed under CC BY-SA-NC
Bone Anatomy
• The structural unit of bone, the osteon, consists
of a minute central canal surrounded by
osteocytes embedded in concentric layers of
mineral matter
• Blood vessels and extensions of nerve cells run
through the central canal, which is connected to
the spaces containing cells by radiating canals
filled with interstitial fluid
• Blood vessels supply nutrients to cells that build
bone, and nerve cells connect bone cells to the
body’s nervous system
Adipose Tissue
• Adipose tissue contains large, densely
clustered adipocytes that are specialized
for fat storage – it has little ECM
• Excess carbohydrates are converted into
fats and stored in adipocytes
• Adipose tissue is richly supplied with
blood vessels, which move fats or their
components to and from adipocytes
• Adipose tissue also cushions the body
and, in mammals, forms an insulating
layer under the skin
Blood
Blood is the major transport vehicle of the body:
• Carries oxygen and nutrients to body cells
• Removes wastes and byproducts such as
carbon dioxide
• Maintains the internal fluid environment,
including the osmotic balance between cells
and interstitial fluid
• Transports hormones and other signal
molecules that coordinate body responses
Blood
Blood cells are suspended in a fluid ECM –
plasma – a solution of proteins, nutrient
molecules, ions, and gases
Erythrocytes (red blood cells) are packed
with hemoglobin that binds and transports
oxygen
Leukocytes (white blood cells) protect the
body against invading viruses, bacteria, and
other pathogens
Platelets (membrane-bound fragments of
specialized blood cells) participate in blood
clotting
Muscle Tissue
• Muscle tissue consists of cells that have the ability to
contract (shorten)
• Contractions are produced by the interaction of two
proteins:
– actin
– myosin
• Muscles move body limbs and other structures, pump blood,
and produce a squeezing pressure in internal organs
• Vertebrates have three types of muscle tissue:
– Skeletal
– Cardiac
– Smooth
Skeletal Muscle
Attached by tendons to the skeleton and helps move body
parts and maintain posture
Cells (muscle fibers) are multinucleate and striated (actin
and myosin molecules are arranged in parallel units that
give the tissue a banded appearance)
Contracts voluntarily in response to signals carried by the
nervous system
Contractions release heat that helps mammals, birds, and
some other vertebrates maintain their body temperatures
Cardiac Muscle
• Striated muscle that contracts spontaneously
(involuntary)
• Cells are short and branched, with each cell
connected to neighboring cells at intercalated
disks
• Cells form an interlinked network, stabilized by
anchoring junctions and gap junctions, which
enables heart muscle to contract in all directions
Smooth Muscle
• Found in the walls of tubes and cavities, including
blood vessels, stomach, intestine, and bladder
• Cells are small and spindle-shaped, and their actin
and myosin molecules are arranged in a loose
network (smooth rather than striated)
• Cells are connected by gap junctions that allow
them to contract as a unit – contractions can be
maintained at steady levels for a long time
Question
Identify the different muscle types
Nervous Tissue
• Contains nerve cells (neurons) that serve as lines
of communication and control between body
parts and glial cells
• Glial cells physically support and provide
nutrients to neurons, provide electrical insulation
between them, and scavenge cellular debris and
foreign matter
• A neuron consists of a:
– cell body
– dendrites (highly branched extensions that
receive signals)
– axons (longer extensions that send signals)
Coordination of Tissues in Organs and Organ Systems
• In tissues, organs, and organ systems, each cell engages in basic metabolic activities for its
own survival, and performs one or more functions for the system to which it belongs
• All vertebrates (and most invertebrates) have eleven major organ systems whose functions
are coordinated and integrated to accomplish vital tasks in the organism
• Together these tasks maintain homeostasis, preserving the internal environment required
for survival of the body
Functions of Organ Systems
Integrated functions of organ systems:
• Acquiring, processing, and distributing required substances, and
disposing of wastes
• Synthesizing protein, carbohydrate, lipid, and nucleic acid molecules
required for body structure and function
• Sensing and responding to changes in the environment (e.g., temp.,
pH, ion concentrations)
• Protecting the body against injury or attack from other animals, and
from disease-causing agents
• Reproducing, nourishing and protecting offspring through their early
growth and development
ECF and ICF
• Each cell in a multicellular organism receives
nutrients and O2, and eliminates wastes, via the
extracellular fluid (ECF)
• The ECF has two components:
– Plasma, the fluid portion of blood
– Interstitial fluid, the fluid that surrounds the cells
• The ECF is the transitional zone connecting the
intracellular fluid (ICF) to the external environment
• Nutrients and O2 in the plasma reach the interstitial
fluid through capillaries – waste moves in the
opposite direction
Question
Which of these is responsible for bone resorption?
a.
b.
c.
d.
Osteocytes
Osteclasts
Osteoblasts
Osteons
Homeostasis
• The composition of ECF and other aspects of the
internal environment (such as temperature) must
be regulated within a narrow range
• Maintenance of the internal environment in a
relatively stable state is homeostasis – a dynamic
process in which internal adjustments are made
continuously to compensate for external changes in
order to maintain a steady state
• The factors controlled by homeostatic mechanisms
all require energy that must be acquired from the
external environment
Homeostatic Control Systems
Humans and other mammals maintain a consistent
internal environment, but many other animals are
more variable in their internal environments
Regulators maintain factors of the internal
environment in a relatively constant state (e.g.,
mammals and birds are thermoregulators)
Conformers have internal environments that match
the external environment (e.g., fishes, reptiles, and
insects are thermoconformers)
Factors of the Internal Environment
Nutrient
concentration
Concentration of
O2
Concentration of
CO2
Concentration of
waste chemicals
Concentration of
water and NaCl
pH
Volume and
pressure of
plasma
Temperature (of
warm-blooded
animals)
Local and Systemic Controls
Local homeostatic controls operate only within an organ where a change in internal environment
needs to be addressed (e.g., increased blood flow to a working muscle)
Systemic homeostatic controls are initiated outside of an organ or organ system to control that
organ’s or organ system’s activity (e.g., maintaining blood pressure) and controlled through
nervous system
endocrine system
Negative Feedback Control
Tissue or organ
that detects a
change
A change in
in factors subject
the environment to
triggering a
homeostatic
response
control,
that compensates such as pH or
for the change
temperature
Stimulus
Sensor
A control
center that
receives information
from the sensor
and initiates steps
to correct
the environmental
change by comparing
the detected change
with a set point, the
level at which the
condition controlled by
the pathway is
to be maintained.
Integrator
A system or systems
activated by the
integrator to
return the
condition to
the set point.
Effectors
may include
The physiological
parts of
actions that return
essentially
the condition to
any body
tissue or organ. the set point
Effector (s)
Compensatory
response
Environmental
condition
returned
to set point
Negative feedback
cancels the system
responsible for the
response.
Stepped Art
Temperature Control in
Mammals
• Humans maintain body temperature near a
set point by negative feedback mechanisms
• If blood temperature falls, the
hypothalamus activates effectors that
constrict blood vessels, reducing heat loss
from the skin – other effectors induce
shivering to generate heat
• If blood temperature rises, the
hypothalamus activates effectors that dilate
blood vessels, increasing heat loss – other
effectors induce sweating, which cools the
skin
Stimulus
The husky is active
on a hot, dry day,
and its body surface
temperature rises.
Sensors
Response
Neurons in the
hypothalamus
detect the increase
in brain and body
temperature.
Integrator
The network of
neurons compares
brain and body
temperature against
a set point.
Temperature of brain
and body decreases.
Many Effectors carry out specific responses:
Salivary glands
Skeletal muscles Smooth muscle
in blood vessels
Husky starts to
pant, increasing
heat loss by
evaporation of
water from lungs,
throat, mouth, and
tongue.
Blood carrying
metabolically
generated heat
circulates through
lungs, throat,
mouth, and
tongue.
Secretions from
glands increase
evaporation of
water from
tongue, mouth,
and throat.
Temperature Control in
Other Animals
• While mammals and birds regulate their internal
body temperature within a narrow range around a
set point; other vertebrates regulate over a broader
range
• Snakes and lizards respond behaviorally to
variations in environmental temperatures – they
bask in the sun on cool days, and move to shady
spots when it is hot
• Dragonflies, moths, and butterflies use muscular
contractions equivalent to shivering when their
body temperature falls below the level required for
flight
Positive Feedback Mechanisms
• Under certain circumstances, animals respond to a
change in the internal or external environment by a
positive feedback mechanism that intensifies or adds to
the change
– Example: Childbirth contractions trigger stretch
sensors that signal the hypothalamus to release
oxytocin from the pituitary gland – oxytocin then
increases the uterine contractions
• Because positive feedback mechanisms do not result in
homeostasis, they are not as common as negative
feedback
Set Points Can Change
• Some regulated factors change in predictable and cycling
patterns called biological rhythms or biorhythms
• Many biorhythms correlate with regular environmental
changes
– Example: In mammals, many physiological processes
have a 24-hour rhythm called a circadian rhythm
• When a set point changes naturally because of an alteration
in environmental conditions, it is called acclimatization
• Acclimatization is a temporary change in a physiological
process that occurs during the life of an animal, whereas
evolutionary adaptation is a change that occurs at the
genetic level over many generations
• When a set point changes artificially in a laboratory setting,
it is called acclimation