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Chapter 1
The Study of Body Function
Remon Wahba, MD
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Chapter 1 Outline
Introduction
to Physiology
Scientific Method
Homeostasis
Tissues:
Muscle Tissue
Nervous Tissue
Epithelial Tissue
Connective Tissue
Organs & Systems
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Human Physiology
Physiology:
Study
of the function of the body
How the body works to Maintain Life
Cell & Tissue
Organs
Systems
Pathophysiology:
How physiological processes are altered in
disease or injury
1-3
Scientific Method
1-4
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Scientific Method
Four
Steps:
 Observation
 Hypothesis
 Experiment
 Conclusion
Theory
 General
statement explaining natural
phenomena that is based on proven
hypotheses (Experiments)
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Testing of Hypotheses
Involves:
Experimental
Quantitative
Analysis
& control groups
measurements performed blindly
of data
1-6
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Using Scientific Method to
Develop New Drugs
When a new drug is suggested by experiments:
 First
step
Test Its effectiveness & toxicity in:
 Tissue culture
 Experimental animals
Rats
 Mice
1-7
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Using Scientific Method to
Develop New Drugs
 Clinical
Trials performed
Phase I Trials: Toxicity & metabolism tested in
healthy human volunteers
Phase II Trials: Effectiveness & toxicity tested in
target population
Phase III Trials: Widespread test of drug in diverse
population
Phase IV Trials: Drug is tested for other uses
1-8
Homeostasis
1-9
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Homeostasis

Maintenance of the internal environment Constant
Dynamic Constancy
Around physiological set points
Failure of Homeostasis leads to illness or death
Maintained mainly by Negative Feedback Loops
1-10
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Homeostasis
 Two
Regulatory Mechanisms:
Intrinsic
Control is built-in the organ being regulated
Extrinsic
Control
comes from outside of organ by
Nervous System
Nervous control of Body Temperature
Endocrine system
Hormonal control of Blood Glucose level
1-12
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Homeostasis
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Homeostasis
Negative
The
Feed Back
response opposes the stimulus
To
counteract further changes and bring
Homeostasis
Positive
The
To
Feed Back
response enhances the original stimulus
speed up the change
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Negative Feedback Loops
Sensor:
Detects
deviation
from set point
Integrating
center:
Determines response
Effector:
Produces
response
Fig 1.1
1-11
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Negative Feedback:
The Control of Body Temperature
Figure 1.5
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Negative Feedback:
The Control of Blood Pressure
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Negative Feedback
Hormonal Control of Blood Glucose
Fig 1.6
1-13
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Positive Feedback Loops
Self-Amplifying
change
The response enhances the original
stimulus
Normal
way of producing rapid changes
Occurs with childbirth, blood clotting,
protein digestion, and generation of nerve
signals
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Positive Feedback Loops
“Childbirth”
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Positive Feedback Loops
“Blood Clotting”
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Tissues
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Tissues
Tissues:
Groups
of specialized cells organized to
perform a limited number of functions
Histology
= study of tissues
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Tissues
The

Four primary types of tissue are:
Epithelial
 Connective
 Muscular
 Nervous
Epithelial Tissue
1-14
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Epithelial Tissue
Covers
body surfaces & Lines body cavities
Separated
from underlying tissue by Basement
Membrane
Consists
of cells that form:
 Membranes
 Glands
Does
not contain Blood Vessels (Avascular)
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Epithelial Tissue (cont)
Cells
Cells
are Regularly
Replaced
are Tightly Joined together with small
amount of matrix (intercellular substances)
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Epithelial Tissue
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Classification of Epithelial tissue
According to:
Number of Layers of Cells
Simple (one layer)
Stratified (more than one layer)
Shape of Apical Cells
Squamous epithelial cells are flattened
Cuboidal epithelial cells are cube-shaped
Columnar epithelial cells are taller than wide
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Stratified Squamous Epithelial Tissue
Non-keratinized
Stratified
Squamous consists of living cells
Mouth Cavity, Vagina…
Keratinized
Stratified
Squamous has outer layer of dead
cells contain water-resistant keratin
Skin.
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Stratified Squamous Epithelial Tissue
Non-keratinized
Stratified
Squamous consists of living cells
Mouth Cavity, Vagina…
Keratinized
Stratified
Squamous has outer layer of dead
cells contain water-resistant keratin
Skin.
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Keratinized
Stratified Squamous Epithelial Tissue
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Simple Cuboidal Epithelium
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Simple Columnar Epithelium
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Pseudo-Stratified
Columnar Epithelium
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Stratified
Columnar Epithelium
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Transitional Epithelium
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Exocrine Glands
Derived
from epithelial cells
Secrete via ducts
Can be simple tubes or clusters called acini
Connective Tissue
1-30
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Connective Tissue
 Has
lots of Extra cellular Material deposited in
spaces between its cells
 Includes
Connective Tissue Proper
Loose & Dense
Fluid Connective Tissue
Blood & Lymph
Supportive Connective Tissue
Cartilage & Bone
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Areolar Connective Tissue
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Adipose Connective Tissue
Specialized
for fat synthesis, breakdown & storage
Fig 1.18
1-33
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Adipose and Reticular Tissues
Figure 4.11
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Dense Connective Tissue
 Dense
Fibrous Connective Tissue
 packed with fibers of collagen
 Two
Types:
Dense Regular
As in Tendons
Dense
Irregular
Capsules, Dermis
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Dense Regular Connective Tissue
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Dense Irregular Connective Tissue
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Fluid Connective Tissue, Blood
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Fluid Connective Tissue, Blood
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Supporting Connective Tissue
(Cartilage)
Specialized
Made
for Support, Protection
of Chondrocytes & Elastic extracellular material
Serves
Forms
as precursor for bone
Articular Surfaces for Joints
1-34
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Cartilage
Three
Types:
Hyaline
Elastic
Fibro
Cartilage
Cartilage
Cartilage
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Hyaline Cartilage
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Elastic Cartilage
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Fibrocartilage
Figure 4.15d
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Supporting Connective Tissue
(Bone)
 Formed
as concentric
layers of calcified
material
 Contains 3 cell types:
Osteoblasts:
bone-forming cells
Osteocytes:
trapped, inactive
osteoblasts
Osteoclasts:
bone resorbing cells
Fig 1.19
1-35
Muscle Tissue
1-23
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Muscle Tissue
Specialized
3



Types:
Skeletal
Cardiac
Smooth
for contraction
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Skeletal Muscles
Striated
 Voluntary
 Attached to the skeleton
 Muscle fibers:
 Formed by fusion of Embryonic Myoblasts
 Large & Multinucleated
 Individually controlled
 Lined-up in parallel to form bundles

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Skeletal Muscles
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Cardiac Muscle
Striated;
Involuntary; in the Heart only
Branched
to form continuous fabric
Intercalated
discs between cells provide
mechanical & electrical interconnections
Fibers
not individually controlled
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Cardiac Muscle
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Smooth Muscle
Unstriated
Involuntary
Found
in the walls of all Hollow Organs
Intestine, Blood Vessels..etc)
Controlled
by ANS
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Smooth Muscle
Nervous Tissue
1-20
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Nervous Tissue
 Consists
of:
Neurons
Supporting or glial cells (Neuroglia)
 Neurons are specialized for conducting electrical
signals
Have 3 basic components:
 Cell body
 Dendrites
 Axon
1-21
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Neurons
 Cell
body
Contains nucleus; is metabolic center
 Dendrites:
Highly
branched extensions off cell body
Receive inputs from other neurons
Conduct impulses to cell body
 Axon:
Single,
long extension off cell body
Conducts nerve impulses to other cells
1-22
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Neurons
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Supporting Cells
Supporting/Glial
cells
Provide physical & functional support for
neurons
Perform Phagocytosis
5X
more abundant than neurons
Organs & Systems
1-36
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Organs & Systems
Organs:
Are
anatomical & functional units made up of
2 or more primary tissues grouped together
to perform a specific function
Systems:
Are
groups of organs working together to
perform certain function / functions to
maintain Homeostasis
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Stem Cells
Most
cells in organs are highly specialized or
differentiated
Many organs retain small populations of adult
stem cells (Undifferentiated Cells)
Can become many cell types
E.g. bone marrow stem cells can give rise
to all of the different blood cell types
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Skin
The
Largest Organ
Has Three layers
Epidermis for protection
Dermis
Contains connective tissue, glands, blood
vessels, nerve receptors
Hypodermis
Contains fatty (Adipose) tissue
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Skin
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Skin
Other
structures:
Hair Follicles
Sweat
Glands
Sebaceous
Glands
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Body-Fluid Compartments

The Body has 2 Fluid Compartments:
Intracellular; inside the cells
Extracellular; outside the cells
Separated by cell’s outer membrane
Extracellular
is composed of
Blood Plasma
The fluid component of blood
Interstitial fluid
Fluid in between body cells
1-39