Chapter 1
Major Themes of Anatomy & Physiology
• Form and Function
• Origins of Biomedical
Science
• Scientific Method
• Human Origins and
Adaptations
• Human Structure
• Human Function
• Language of Medicine
Anatomy - The Study of Form
• Observation of surface structure
• Cadaver dissection is cutting & separation of
organs to study their relationships
• Comparative anatomy is the study of more than
one species to analyze evolutionary trends
• Physical examination
– palpation, auscultation, percussion
• Gross anatomy is what is visible with naked eye
• Histology is examination of cells with microscope
Early Anatomical Drawings
Physiology - The Study of Function
• Study of bodily functions by use of methods of
experimental science
• Comparative physiology involves the study of
different species
• Basis for the development of new drugs and
medical procedures
Beginnings of Medicine
• Physicians in Mesopotamia & Egypt 3000 years ago
used herbal drugs, salts & physical therapy
• Greek physician Hippocrates established a code of
ethics & urged physicians to seek causes of disease
• Aristotle called causes for disease physiologi & said
that complex structures are built from simpler parts
• Galen, physician to the Roman gladiators, saw science
as a method of discovery
– did animal dissections since use of cadavers banned
– wrote book advising followers to trust their own observation
Birth of Modern Medicine
• Little advancement during the Middle ages since medicine was
taught as dogma with no new ideas
• Avicenna from Muslim world supported free inquiry over authority
– wrote The Canon of Medicine, used in medical schools until 16th century
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Vesalius published accurate gross anatomy atlas (1543)
Harvey realized blood flow out from heart & back in 1628
Leeuwenhoek invented microscope to look at fabrics (1632-1723)
Hooke (1665) and Zeiss (1860) developed & improved compound
microscope (described plant cell walls in 1665)
• Schleiden & Schwann thought that all organisms were composed
of cells -- cell theory of 1839
• Clinical practice was in dismal state
– bleeding patients to remove toxins, operate with dirty hands, no anesthesia
for amputations
Early Microscopes
Living in a Revolution
• Pioneers in 19th & 20th centuries
– established scientific way of thinking
– replaced superstition with natural laws
– momentous discoveries
• germ theory of disease
• heredity & structure of DNA
• Now at threshold of modern biomedical science
– technology enhanced diagnostic ability & life-support strategies
– genetic revolution --library of the molecular structure of every
human gene is finished
• Gene therapy being used to treat disease
Scientific Method
• Bacon (1561-1626) and Descartes (1596-1650)
– were not scientists but did invent new habits of
scientific thought
• scientific method as habits of disciplined creativity, careful
observations, logical thinking & analysis of observations
• way of seeking trends & drawing generalizations
• Convinced governments of England & France to
form academies of science that still exist today
• Scientific way of thinking based on assumptions
& methods that are reliable, objective & testable
Inductive Method
• First described by philosopher Francis Bacon
• Making observations until capable of drawing
generalizations and making predictions
– anatomy is a product of inductive method
• Proof in science can not go past “proved beyond
reasonable doubt”
– reliable methods of observation
– tested and confirmed repeatedly
– not falsified by any credible observation
• In science, all truth is tentative
Hypothetico-Deductive Method
• Physiological knowledge gained by this method
• Ask a question and formulate a hypothesis -- an
educated possible answer
• Good hypothesis
– consistent with what is already known
– capable of being tested and falsified with certain
evidence
• If nothing could prove it wrong, it is not a
scientific belief
• Hypotheses are written as If-Then predictions
– modified and rewritten after testing
Experimental Design
• Sufficient sample size to prevent chance event
• Control group and treatment group receive the same
treatment except for the variable being tested
• Prevention of psychosomatic effects
– use of placebo in control group
• Experimenter bias
– prevented with double-blind study
• Statistical testing to be sure the difference between
groups was not random, but was due to variable
being tested
Peer Review
• Critical evaluation by other experts in the
field
– prior to funding
– verification and repeatability of results
• Ensures honesty, objectivity & quality in
science
Facts, Laws and Theories
• Scientific fact is information that can be
independently verified by any trained person
– iron deficiency leads to anemia
• Law of nature is a description of the way matter
and energy behave
– resulting from inductive reasoning & repeated
observations
– written as verbal statements or mathematical formulae
• Theory is a summary of conclusions drawn from
observable facts
– it provides explanations and predictions
– sliding filament theory of muscle contraction
Human Origins and Adaptations
• Charles Darwin’s theory of natural selection
explains how species originate and change through
time
– On the Origin of Species by Means of Natural Selection
(1859)
– The Descent of Man (1871) discussed human evolution
& our relationships to other animals
• Changed our view of our origin, our nature & our
place in the universe
• Good understanding of our evolutionary history
deepens our understanding of form & function
Evolution, Selection, and Adaptation
• Evolution is change in genetic composition of a
population of organisms
– development of bacterial resistance to antibiotics, new
strains of AIDS virus and emergence of new species
• Theory of natural selection
– some individuals have hereditary advantages
(adaptations) enabling them to produce more offspring
– if they pass these characteristics on it brings about a
genetic change in the population (evolution)
– forces that favor some individuals over others are
called selection pressures -- climate, disease, etc.
Adaptations
• Adaptations are useful features that evolved in response
to selection pressures
• DNA hybridization suggests a difference of only 1.6% in
DNA structure between humans & chimpanzees
• Evolutionary developments help explain some aspects of
our anatomy (vestigial organs)
– piloerector muscle in the skin have no use
– auricularis muscles do not move in most people
• Evolutionary relationships help us chose animals for
biomedical research
– rats & mice used extensively
Primate Adaptations
• Some human features can be traced to the earliest
primates
• Squirrel-sized, insect-eating mammals became
arboreal probably due to safety, food supply & lack
of competition
– shoulder became more mobile (reach any direction)
– thumbs became opposable to encircle branches with
thumb & fingers (prehensile)
– forward-facing eyes provide depth perception
• judge distances accurately for leaping & catching prey
– color vision to distinguish ripe fruit
– larger brains & good memory to remember food sources
Walking Upright
• African forest became grassland 5 million years ago
• Bipedalism (standing & walking on 2 legs) evolved
– spot predators, carry food or infants
• Adaptations for bipedalism
– pelvis, femur, knee, great toe, arch, skull, vertebrae, etc.
• Australopithecus (2.5mya) gave rise Homo habilis
– taller, larger brain volume, speech, tool-making
• Homo erectus (1.1mya) and Homo sapiens (.3mya)
• Homo sapiens include Neanderthal & Cro-Magnon
• Evolutionary medicine traces our diseases to
evolutionary past
Primate Phylogeny
Human Structure
• Hierarchy of complexity
– organism is composed of organ
systems
– organ systems composed of
organs
– organs composed of tissues
– tissues composed of cells
– organelles composed of
molecules
– molecules composed of atoms
– Atoms compose molecules
• Reductionism versus holism
Anatomical Variation
• No 2 humans are exactly alike
• Missing organs
– palmaris longus or plantaris muscles
• More or less organs than normal
– 2 spleens, single kidney, 6 or 4 lumbar vertebrae
• Variation in organ locations (situs inversus,
dextrocardia, situs perversus)
Human Function
• Characteristics of life
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organization
cellular composition
excretion
metabolism
responsiveness and movement
homeostasis
development (growth or differentiation)
reproduction
evolution
• Clinical death is no brain waves for 24 hours
Physiological Variation
• Differs with sex, age, diet, weight, degree of
physical activity
• Typical human values
– reference man
• 22 years old, 154 lbs, light physical activity
• 2800 kcal/day
– reference woman
• same as man except 128 lbs and 2000 kcal/day
Homeostasis
• Hippocrates noted that body normally returns to a
state of equilibrium by itself
– needs to detect the change & oppose it
• Walter Cannon (1871-1945) coined the term
homeostasis indicating stable internal environment
• Internal environment described as dynamic
equilibrium
– fluctuates within a range around a certain set point
• Loss of homeostatic control causes illness or death
Negative Feedback Loops
• Mechanism to keep a variable close to its set point
• Body senses a change & activates mechanisms to
reverse it
Negative Feedback, Set Point
• Room temperature does not stay at set point of 68
degrees -- it only averages 68 degrees
Human Thermoregulation
• Blood temperature sensing nerve cells in base of brain
control shivering, sweating & vasomotor activity
– vasodilation with heat & vasoconstriction with cold
• Evaporation of water & heat radiation occur
Control of Blood Pressure
• Rise in blood pressure detected
– stretch receptors in wall of heart and major
arteries
• Nerve signals travel to cardiac center in
brainstem
• Nerve signals slow heart and lower blood
pressure
Structures Needed for Feedback Loop
• Receptor = structure that senses change
– stretch receptors in heart & large blood vessels send
information of an elevated BP to integrator
• Integrator = control center
– cardiac center in brainstem that signals heart to slow
• Effector = structures that carry out commands of
the control center
– heart slows and BP decreases
– sweating begins and evaporation cools the body
Positive Feedback Loops
• Physiological change that leads to an even greater change
in the same direction (self-amplifying)
• Normal way of producing rapid changes
– birth, blood clotting, protein digestion, generation of nerve
signals
Life-Threatening Fever
• If temperature rises above 108 degrees due to
bacterial infection
– metabolic rate
increases causing
body to produce
heat faster still
• Temperature
increases &
cycle repeats
• Fatal at 113
degrees
History of Anatomical Terminology
• Most medical terms are formed from Greek and Latin
roots
• Fast-paced anatomical discoveries during the
Renaissance resulted in naming confusion
– different countries naming same structures with different names
– structures being named after people (eponyms)
• Anatomy meetings in 1895 began search for uniform
international terminology
– Nomina Anatomica (NA) rejected all eponyms
• gave each structure a unique Latin name to be used worldwide
– Terminologia Anatomica was codified in 1998
Analyzing Medical Terms
• Medical terminology based on word elements
– lexicon of 400 common word elements in back of
book
• Scientific terms are composed of the following
elements
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at least one root (stem) that bears the core meaning
combining vowels that join roots together
prefix that modifies the core meaning of the word
suffix that modifies the core meaning of the word
• acronyms – words composed of the first few
letters of a series of words
Useful Tables in Textbook
Review of Major Themes
• Unifying principles behind all aspects of human
anatomy and physiology
– cell theory: all structure & function result from the
activity of cells
– homeostasis: maintaining stable conditions within the
body
– evolution: the body is a product of evolution, molded
by years of natural selection
– hierarchy of structure: levels of complexity
– unity of form and function: physiology can not be
separated from anatomy
Medical Imaging
• Radiography
– x-rays discovered (William Roentgen) in 1885
– penetrate soft tissues & darken photographic
film on other side of the body
– dense tissue(bone, teeth and tumors) are not
penetrated so photographic film remains white
– radiopaque substances can be either injected
(angiography) or swallowed for examination
of the gastrointestinal tract
• Sonography
– high-frequency ultrasound waves echoes back
from internal organs
– obstetrics uses to locate placenta, evaluate fetal
age, position and development
Medical Imaging
• Computed Tomography (CT scan)
– low-intensity X rays applied to the body
– computer analysis produces an image of a slice
of the body about as thin as a coin
– tumors, aneurysms, hemorrhages, kidney
stones, etc
• Magnetic Resonance Imaging (MRI)
– magnetic field aligns hydrogen atoms; radio
waves realign the atoms; when radio is turned
off the atoms give off energy depending on tissue
type
– computer analysis produces a “slice” type image
– better for soft tissue analysis than CT
Medical Imaging
• Positron Emission Tomography (PET scan)
– assesses the metabolic state of a tissue
– injection of radioactively labeled glucose emits
positrons
– colliding positrons & electrons
give off gamma rays that are
analyzed by computer
– color image of glucose usage at
that moment
• extent of damaged heart tissue
• activity of brain of neurology patients