Chapter 1 Major Themes of Anatomy

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Chapter 1Major Themes of Anatomy Physiology

• Structure and Function
• Origins of Biomedical Science
• Scientific Method
• Human Evolution
• Nature of Life
• Homeostasis

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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

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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

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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

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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

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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

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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

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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

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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

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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

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Peer Review

• Critical evaluation by other experts in the field
• Ensures honesty, objectivity quality in science

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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

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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

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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.

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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

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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

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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

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Primate Phylogeny
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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

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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.
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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

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Our Vertebrate Characteristics

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

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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

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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

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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

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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

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Negative Feedback and Stability

• Mechanism to keep a variable close to its set
  point
• Body senses a change 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

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

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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

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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

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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

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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

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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

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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

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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