1 themes in a&p

Chapter 1Major Themes of Anatomy & Physiology

• Structure and Function• Origins of Biomedical

Science• Scientific Method• Human Evolution• Nature of Life• Homeostasis

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 (with a stethoscope), percussion• Gross anatomy is what is visible with naked eye• Histology is examination of cells with microscope

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

• 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

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

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

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

belief

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

Peer Review

• Critical evaluation by other experts in the field

• 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 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

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

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.

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

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

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

Primate Phylogeny

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

What is a Human?

Phylum ChordataSubphylum Vertebrata

Class MammaliaOrder Primates

Family Hominidae Genus Homo Species Homo sapiens

Human classification within the kingdom Animalia.

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

Our Vertebrate Characteristics

• Subphylum Vertebrata• Characteristics of all

– internal skeleton– jointed vertebral (spinal) column– well developed brain & sense organs– cranium to protect the brain

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

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

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

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

Negative Feedback and Stability• 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

• Temperature sensing nerve cells in base of brain control shivering, sweating & vasomotor activity– vasodilation & vasoconstriction

• Evaporation of water & heat radiation occur

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

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

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

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

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

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

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