Chapter 1 Major Themes of Anatomy & Physiology

1. Chapter 1Major Themes of Anatomy & Physiology • Structure and Function • Origins of Biomedical Science • Scientific Method • Human Evolution • Nature of Life • Homeostasis

2. Anatomy - The Study of Form • Observation of surface structure • Cadaver dissection is cutting & separation of tissues 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. 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

4. 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

5. 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 accurately illustrated gross anatomy in 1543 • Harvey realized blood flow out from heart & back in 1628 • Leeuwenhoek invented microscope to look at fabrics (1632-1723) • Hooke and Zeiss (1830)developed & improved compound microscope (wrote Micrographia 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

6. Living in a Revolution • Pioneers in establishing the scientific way of thinking occurred in 19th & 20th centuries • germ theory of disease • mechanisms of heredity & structure of DNA • Now, on threshold of modern biomedical science • Technology enhanced diagnostic ability & life-support strategies • Verge of a genetic revolution due to library of the molecular structure of every human gene

7. 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

8. 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

9. 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 • Falsifiability means that certain evidence would prove something wrong • if nothing could prove it wrong, it is not a scientific belief

10. Proper Experimental Design • Sufficient sample size to prevent chance event • Control group receiving 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

11. Peer Review • Critical evaluation by other experts in the field • Ensures honesty, objectivity & quality in science

12. 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 generalization about the way matter and energy behave -- resulting from inductive reasoning & repeated observations • first law of thermodynamics is that energy can be converted from one form to another but not destroyed • Theory is an explanatory statement that makes predictions and suggests areas for further study • sliding filament theory, fluid-mosaic theory, cell theory

13. Human Evolution • Charles Darwin proposed the theory of natural selection to explain 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

14. 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 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.

15. Evidence of Human Evolution • DNA hybridization suggests a difference of only 1.6% in DNA structure between humans & chimpanzees • Evolutionary developments help explain some aspects of our anatomy • arrector pili 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

16. Life in the Trees • Origin of primates began 60 million years ago • 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 be able to encircle branches with thumb & fingers (prehensile) • forward-facing eyes provide (depth perception) • judge distances accurately to jump & catch prey • color vision to distinguish ripe fruit • larger brains & good memory to remember food sources

17. 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

18. Primate Phylogeny

19. What is Life? • Properties that distinguish from nonliving things: • organization & cellular composition • biochemical composition (DNA, proteins, etc) • metabolism is transformation of molecules into others • responsiveness is ability to sense & react to stimuli • homeostasis is to maintain stable internal environment • development is change over time (growth or differentiation) • reproduction is producing copies of themselves • evolution is genetic change between generations • Clinical death is no brain waves for 24 hours

20. What is a Human? Phylum Chordata Subphylum Vertebrata Class Mammalia Order Primates Family Hominidae Genus Homo Species Homo sapiens Human classification within the kingdom Animalia.

21. Our Chordate Characteristics • Notochord • flexible rod on upper side of body -- replaced by vertebral column during development • Dorsal hollow nerve cord • Gill pouches • bulges in throat region develop into gills in fish & amphibians • Postanal tail • GI tracts end before end of tail • tail in humans visible only in embryo

22. Our Vertebrate Characteristics • Subphylum Vertebrata • Characteristics of all • internal skeleton • jointed vertebral (spinal) column • well developed brain & sense organs • cranium to protect the brain

23. Our Mammalian Characteristics • Class Mammalia • Characteristics of all • mammary glands for nourishment of young • hair to retain body heat • endothermy is ability to generate most of body heat • heterodonty is possession of varied types of teeth • single lower jawbone provides for better chewing • 3 middle ear bones

24. Primate & Hominid Characteristics • Order Primates • Characteristics of all • 4 upper and lower incisors for front cutting • pair of clavicles (collarbones) • only 2 mammary glands • pendulous penis, attached only at base • forward-facing eyes with stereoscopic vision • flat nails in place of claws • opposable thumbs • Family Hominidae are only bipedal primates • Homo sapiens are only surviving species

25. Structure - A Hierarchy of Complexity • Subatomic particles compose atoms • Atoms compose molecules • Molecules compose organelles • Organelles compose cells • Cells compose tissues • Tissues compose organs • Organs compose organ systems • Organ systems compose the organism

26. 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

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

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

29. Human Thermoregulation • Temperature sensing nerve cells in base of brain control shivering, sweating & vasomotor activity • vasodilation & vasoconstriction • Evaporation of water & heat radiation occur

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

31. Positive Feedback Loops • Self-amplifying cycle in which a physiological change leads to an even greater change in the same direction • Normal way of producing changes during birth, blood clotting, protein digestion & generation of nerve signals

32. Fever • If temperature rises above 108 degrees • metabolic rate increases causing body to produce heat faster still • Temperature increases & cycle repeats again • Fatal at 113 degrees

33. 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

34. Noninvasive Medical Imaging • Radiography • x-rays discovered by William Roentgen in 1885 • penetrate soft tissues of body & darken photographic film on other side of the body • Sonography • handheld device produces high-frequency ultrasound waves and receives echoes back from internal organs • obstetrics uses to locate placenta, evaluate fetal age, position and development • used medically in the 1950s but little value until computers could develop differences in echoes

35. Noninvasive 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 from which a three-dimensional image of the body is constructed • 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

36. Noninvasive Medical Imaging • Positron Emission Tomography (PET) • 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 which tissue were using glucose at the moment • extent of damaged heart tissue • activity of brain of neurology patients