Chapter 1 Major Themes of Anatomy & Physiology

1. Chapter 1Major Themes of Anatomy & Physiology • Form and Function • Origins of Biomedical Science • Scientific Method • Human Origins and Adaptations • Human Structure • Human Function • Language of Medicine

2. 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

3. Early Anatomical Drawings

4. 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

5. 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

6. 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 • 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

7. Early Microscopes

8. 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

9. 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

10. 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

11. 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

12. 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

13. Peer Review • Critical evaluation by other experts in the field • prior to funding • verification and repeatability of results • Ensures honesty, objectivity & quality in science

14. 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

15. 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

16. 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.

17. 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

18. 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

19. 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

20. Primate Phylogeny

21. 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

22. 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)

23. Human Function • Characteristics of life • organization • cellular composition • excretion • metabolism • responsiveness and movement • homeostasis • development (growth or differentiation) • reproduction • evolution • Clinical death is no brain waves for 24 hours

24. 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

25. 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

26. Negative Feedback Loops • Mechanism to keep a variable close to its set point • Body senses a change & activates mechanisms to reverse it

27. Negative Feedback, Set Point • Room temperature does not stay at set point of 68 degrees -- it only averages 68 degrees

28. 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

29. 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

30. 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

31. 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

32. 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

33. 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

34. 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 • 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

35. Useful Tables in Textbook

36. 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

37. 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

38. 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

39. 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