Chapter 1

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Chapter 1

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Major Themes of Anatomy and Physiology

• Form and Function

• Origins of Biomedical Science

• Scientific Method

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• Human Origins and Adaptations

• Human Structure• Human Function• Language of

Medicine

Major Themes of Anatomy and Physiology 2

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Anatomy - The Study of Form

• Observation of surface structure• Cadaver dissection – cutting and separation of organs to study

their relationships• Comparative anatomy – study of more than one species to analyze

evolutionary trends

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• Physical examination– palpation, auscultation, percussion

• Gross anatomy – visible with naked eye

• Histology– examination of cells with microscope

Anatomy - The Study of Form

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Early Medical Illustrations

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Physiology - The Study of Function

• Study of bodily functions – using methods of experimental science

• Comparative physiology– study of different species

• Basis for the development of new drugs and medical procedures

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Beginnings of Medicine

• Physicians in Mesopotamia and Egypt – 3000 years ago used herbal drugs, salts and

physical therapy• Greek physician Hippocrates – established a code of ethics– urged physicians to seek causes of disease

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• Aristotle – called causes for disease physiologi– 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

Beginnings of Medicine

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Birth of Modern Medicine• Middle Ages– little advancement– medicine was taught as dogma with no new ideas

• Avicenna from Muslim world– supported free inquiry over dogma– wrote The Canon of Medicine, used in medical

schools until 16th century• Vesalius (1543) – published accurate gross anatomy atlas

• Harvey (1628)– realized blood flow out from heart and back in

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• Leeuwenhoek (1632-1723) – invented a simple microscope (200x) to look at

fabrics• Hooke (1665) and Zeiss (1860) – developed and improved compound microscope– described plant cell walls in 1665

• Schleiden and Schwann (1839)– concluded that all organisms were composed of

cells– 1st tenet of cell theory

Birth of Modern Medicine 2

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Early Compound Microscopes

The first cells seen were plant cell walls in a section of dried cork.

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Living in a Revolution• Early pioneers were important– established scientific way of thinking– replaced superstition with natural laws

• Modern biomedical science– technological enhancement• diagnostic ability and life-support strategies

• Genetic Revolution• human genome is finished• gene therapy is being used to treat disease

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Scientific Method• Bacon (1561-1626) and Descartes

(1596-1650)– new habits of scientific thought

• England and France– academies of science --still exist today

• Science– produces reliable, objective and testable

information about nature

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Inductive Method• Philosopher Francis Bacon– observations, generalizations and predictions– anatomy

• Proof in science – reliable observations– tested repeatedly– not falsified by any credible observation

• In science, all truth is tentative– “proof beyond a reasonable doubt”

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Hypothetico-Deductive Method

• Physiological knowledge • Test your hypothesis (answer) to a

specific question • Good hypothesis– consistent with what is already known– testable and falsifiable with evidence

• Hypotheses are written as If-Then statements

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Proper Experimental Design

• Sample size– sufficient to prevent chance event

• Control group and treatment group– identical treatment except for the variable being

tested• Prevention of psychosomatic effects – use of placebo in control group

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• Experimenter bias – prevented with double-blind study

• Statistical testing – difference between control and test

subjects was not random variation– due to the variable being tested

Proper Experimental Design 2

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Peer Review• Critical evaluation by other

experts in the field– done prior to funding or publication– done by using verification and

repeatability of results• Ensures honesty, objectivity and

quality in science

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Facts, Laws and Theories

• Scientific fact– information independently verified

• Law of nature– description of the way matter and energy behave – results from inductive reasoning and repeated

observations– written as verbal statements or mathematical formulae

• Theory– summary of conclusions drawn from observable facts– it provides explanations and predictions

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Human Origins and Adaptations

• Charles Darwin (1809-1882) – On the Origin of Species by Means of Natural

Selection (1859)– The Descent of Man (1871)

• Theory of natural selection– how species originate and change through

time– changed view of “our origin, our nature and

our place in the universe”– increases understanding of form and function

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Evolution, Selection, and Adaptation

• Evolution– change in genetic composition of population• development of bacterial resistance to antibiotics

• Adaptations– individuals with hereditary advantages– produce more offspring under given selection

pressures (harsh climate, predators)– inheritable characteristics• genetic change in the population (evolution)

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Animal Relations• Closest relative = chimpanzee– difference of only 1.6% in DNA structure – chimpanzees and gorillas differ by 2.3%

• Study of evolutionary relationships– chose animals for biomedical research

(the animal model)– rats and mice used extensively due to

issues involved with using chimpanzees

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Primate Adaptations• Earliest primates– squirrel-sized, arboreal, insect-eating mammals

• due to safety, food supply and lack of competition

• Adaptations for aboreal life style– mobile shoulders– opposable thumbs manipulate small objects– forward-facing eyes (stereoscopic vision)

• depth perception for leaping and catching prey– color vision

• distinguish ripe fruit– larger brains and good memory

• remember food sources

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Walking Upright

• African forest became grassland – millions of years ago

• Bipedalism– standing and walking on 2 legs– spot predators, carry food or infants

• Adaptations for bipedalism– skeletal and muscular modifications

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• Australopithecus – gave rise Homo habilis (2.5mya) • taller, larger brain volume, speech, tool-making

• Homo habilis– gave rise to Homo erectus (1.1mya)

• Homo erectus– gave rise to Homo sapiens (.6 to .2mya?)

• Diseases and imperfections from our evolutionary past

Walking Upright

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Primate Phylogeny

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Hierarchy of complexity

• organism is composed of organ systems

• organ systems composed of organs

• organs composed of tissues

• tissues composed of cells

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Hierarchy of Complexity

• Cells contain organelles

• Organelles composed of molecules

• Molecules composed of atoms

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Anatomical Variation

• No 2 humans are exactly alike– variable number of organs– variation in organ locations (situs inversus,

dextrocardia, situs perversus)

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Characteristics of Life

• Organization • Cellular composition• Excretion• Metabolism and excretion• Responsiveness and movement• Homeostasis • Development• Reproduction• Evolution

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Physiological Variation

• Sex, age, diet, weight, physical activity• Typical values– reference man• 22 years old, 154 lbs, light physical activity• consumes 2800 kcal/day

– reference woman• same as man except 128 lbs and 2000 kcal/day

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Homeostasis

• Claude Bernard (1813-78) – stable internal conditions regardless of

external conditions• Homeostasis –Walter Cannon (1871-1945) coined the term– fluctuates within limited range around a set

point• Loss causes illness or death

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Negative Feedback Loop• Body senses a change and activates

mechanisms to reverse it

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Negative Feedback, Set Point

• Room temperature does not stay at set point of 68 degrees -- it only averages 68 degrees

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Human Thermoregulation

• Brain senses change in blood temperature– if overheating, vessels dilate in the skin and sweating begins– if too cold, vasoconstriction in the skin and shivering begins

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Control of Blood Pressure• Circulatory stretch receptors– detect a rise in BP

• Cardiac center in brainstem– sends out nerve signals

• Heart slowed and BP lowered

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Structure of Feedback Loop• Receptor = senses change• Integrator = control center that

responds• Effector = structures that restore

homeostasis

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Positive Feedback Loops• Self-amplifying change

– leads to change in the same direction• Normal way of producing rapid changes

– occurs with childbirth, blood clotting, protein digestion, and generation of nerve signals

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Life-Threatening Fever

• Temperature > 108 degrees F– increases metabolic rate– body produces heat even faster

• Cycle continues to reinforce itself• Becomes fatal at 113 degrees F

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Anatomical Terminology

• Medical terms from Greek and Latin roots• Naming confusion during the Renaissance– same structures with different names– structures named after people (eponyms)

• Search for uniform international terminology– 1895 Nomina Anatomica (NA) rejected all eponyms

• each structure = unique Latin name– Terminologia Anatomica was codified in 1998

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Analyzing Medical Terms

• Terminology based on word elements– lexicon (Appendix C)

• Scientific terms – one root (stem) with core meaning– combining vowels join roots– prefix modifies core meaning– suffix modifies core meaning – Acronyms• first few letters of series of words

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Useful Tables in Textbook

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Review of Major Themes

• Cell theory– activity of cells determine structure and function

• Homeostasis– maintaining stable internal conditions

• Evolution– our body evolved by natural selection

• Hierarchy of structure– levels of complexity

• Unity of form and function– physiology is inseparable from anatomy

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Medical Imaging • Radiography (x rays)

– William Roentgen - 1885– penetrate soft tissues and

darken photographic film– dense tissue remains white

• Radiopaque substances– injected or swallowed – hollow structures

– blood vessels– intestinal tract

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Medical Imaging• Computed Tomography (CT scan)– low-intensity X rays and computer analysis

• slice type image• increased sharpness

• Magnetic Resonance Imaging (MRI)– slice type image– best for soft tissue– Mechanics

• magnetic field aligns atoms• radio waves realign the atoms• radio turned off• atoms realign to the magnetic field• energy given off depending on tissue type

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Medical Imaging• Positron Emission Tomography

(PET scan)– assesses metabolic state–mechanics• inject labeled glucose

– positrons and electrons collide– gamma rays given off

• analyzed by computer– image glucose usage

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Medical Imaging• Sonography– mechanics

• high-frequency sound waves echo back from internal organs

– avoids harmful x rays– obstetrics– 2nd most commonly

used technique