RG

Anatomy and Physiology: Major Themes

Chapter 01 Major Themes of Anatomy and Physiology

Course Administration and Policies

  • Exam/Quiz Dates: Students are responsible for checking the syllabus and BrightSpace for dates and covered chapters. Direct inquiries via email/text about these details will not be answered.
  • Missing an Exam: A documented reason is required (e.g., doctor's note, tow truck receipt). "Not feeling well" via M.E. will not suffice.
  • Study Tips (Bio 137/1238):
    • Print out slides before class as they are "fair game."
    • Study each slide, finding personal ways to remember names and locations.
    • Study in silence to avoid distractions impacting memory.
    • Study briefly every day, then dedicate in-depth study to one lecture per day starting a few days before a quiz/exam.
    • The day before a test, briefly review all lectures, and quiz oneself by covering labeled parts on printed notes and vocalizing their names and spellings.
  • Academic Dishonesty: Strongest condemnation. Consequences range from a zero on the assignment to course failure, or recommendation for suspension/expulsion from the university.

1.1 Introduction: Anatomy and Physiology

  • Anatomy: The study of body structure.
  • Physiology: The study of body function.
  • Relationship: Anatomy and physiology are complementary and inseparable.
    • Physiology provides meaning to anatomy.
    • Anatomy makes physiology possible.

1.1a Anatomy—The Study of Form

  • Methods for Examining Human Body Structure:
    • Inspection: Looking at appearance.
    • Palpation: Feeling a structure with the hands.
    • Auscultation: Listening to sounds produced by the body (e.g., heart, lung sounds).
    • Percussion: Tapping on the body, feeling for resistance, and listening to emitted sounds for abnormalities.
    • Dissection: Cutting and separating human body tissues to reveal tissue relationships, often performed on a cadaver (a dead human body).
    • Comparative Anatomy: Studying multiple species (e.g., through dissection) to understand form, function, and evolution across different organisms.
    • Exploratory Surgery: Opening the living body to diagnose and treat internal problems. This method has largely been replaced by less invasive medical imaging techniques.
    • Radiology: A branch of medicine specializing in medical imaging to view the inside of the body without surgery.

1.2a The Greek and Roman Legacy

  • Hippocrates (Greek physician):
    • Known as the "Father of Medicine."
    • Established a code of ethics, famously known as the Hippocratic Oath.
    • Advocated for seeking natural causes of disease rather than attributing them to supernatural acts of gods and demons.
  • Aristotle (Greek philosopher):
    • Believed diseases could have supernatural (theologi) or physical (physiologi) causes.
    • His distinction between these causes gave rise to the terms physician and physiology.
    • Held the belief that complex structures are built from simpler parts—a foundational concept in biology.
  • Metrodora (Greek physician):
    • The first known woman to publish a medical textbook.
  • Claudius Galen (Roman physician):
    • Served as a physician to Roman gladiators.
    • Performed animal dissections extensively due to a ban on human cadavers, leading to some inaccuracies when extrapolating to humans.
    • Viewed science as a method of discovery.
    • His teachings became widely adopted as medical dogma in Europe throughout the Middle Ages, influencing medical practice for centuries.

The Birth of Modern Medicine

  • Andreas Vesalius (1514–1564):
    • Considered a pivotal figure in the beginning of modern Western medicine.
    • His work coincided with the Catholic Church relaxing its restrictions on the dissection of cadavers.
    • Performed his own dissections, unlike his predecessors who often relied on barber-surgeons.
    • Published the first comprehensive atlas of anatomy, De Humani Corporis Fabrica (On the Structure of the Human Body) in 1543. This work meticulously depicted human anatomy based on direct observation.
  • William Harvey (1578–1657):
    • An early physiologist whose contributions are seen as the birth of experimental physiology.
    • Published De Motu Cordis (On the Motion of the Heart and Blood in Animals) in 1628 which described the complete circulation of blood.
    • Realized that blood flows out from the heart and returns to it again, proposing a circulatory system rather than blood being consumed by tissues.
    • Credit also given to Michael Servetus for earlier, partial insights into pulmonary circulation.
  • Robert Hooke (1635–1703):
    • Made significant improvements to the compound microscope.
    • Invented key components such as the specimen stage, illuminator, and coarse and fine focus controls.
    • His microscopes could magnify objects up to 30X.
    • Was the first to observe and name "cells" after viewing cork tissue under his microscope.
    • Published the first comprehensive book of microscopy, Micrographia, in 1665, detailing his observations.
  • Antony van Leeuwenhoek (1632–1723):
    • Invented a simple (single-lens) microscope renowned for its great magnification, initially developed to examine fabrics.
    • Achieved superior magnification (up to 200X) compared to Hooke's compound microscope due to his exceptional lens-making skills.
    • Published detailed observations of various microscopic entities, including blood cells, lake water microorganisms, sperm, and bacteria from tooth scrapings.
  • Matthias Schleiden (1804–1881) and Theodor Schwann (1810–1882):
    • Examined a wide variety of biological specimens.
    • Co-formulated the Cell Theory, concluding that "all organisms were composed of cells." This is considered the first tenet of the cell theory.
    • The Cell Theory is regarded as perhaps the most important breakthrough in biomedical history, providing a unifying principle for all life.
    • It posits that all functions of the body can be interpreted as effects of cellular activity.

1.3 Introduction to the Scientific Method

  • Scientific Method: The systematic process of performing science, which includes:
    • Careful observation.
    • Logical thinking.
    • Proper analysis of observations and conclusions.
  • Science and scientific methods establish reliable standards for truth and knowledge.

1.3b The Hypothetico–Deductive Method

  • Primary Method: Most physiological knowledge is gained through this method.
  • Hypothesis Formulation: An investigator formulates a hypothesis, which is an educated speculation or a possible answer to a question.
  • Characteristics of a Good Hypothesis:
    • It must be consistent with what is already known.
    • It must be testable through experimentation.
  • Falsifiability: A key principle stating that if a claim is scientifically true, it must be possible to specify what evidence would be required to prove it wrong.

1.3c Experimental Design Elements

  • Sample Size: Refers to the number of subjects included in a study. A larger sample size generally increases the reliability of the results.
  • Controls: A crucial aspect where a control group is used, which closely resembles the treatment group but does not receive the experimental treatment (e.g., medicine, intervention).
  • Psychosomatic Effects: The influence of a subject's state of mind (expectations, beliefs) on their physiology.
    • These effects are often tested by administering a placebo (an inactive substance) to the control group.
  • Experimenter Bias: To avoid this, the double-blind method is employed.
    • In a double-blind study, neither the subject nor the experimenter knows whether the subject is part of the control group or the treatment group.
  • Statistical Testing: Utilized to analyze experimental data and provide a statement of probability regarding the effectiveness of the treatment, helping to determine if observed differences are significant or due to chance.

1.3d Peer Review

  • Definition: A critical evaluation process conducted by other experts in the same field.
  • Timing: Peer review typically takes place prior to the funding of research or the publication of research findings.
  • Process: It involves the verification and repeatability of results by other researchers.
  • Purpose: Ensures honesty, objectivity, and quality in scientific research and publications.

1.3e Facts, Laws, and Theories

  • Scientific Fact: Information that can be independently verified and is generally accepted as true.
  • Law of Nature: A generalization describing the consistent behavior of matter and energy.
    • It results from inductive reasoning and numerous repeated observations.
    • Can be expressed as a verbal statement or a mathematical formula (e.g., F = ma).
  • Theory: An explanatory statement or a set of statements derived from confirmed facts, laws, and hypotheses.
    • A theory summarizes what is currently known about a phenomenon.
    • It suggests directions for further scientific study and research.

1.4 Introduction: Evolution and the Human Body

  • Theory of Natural Selection: Provides an explanation for how species originate and change over time, offering a crucial framework for understanding the human body.
  • Charles Darwin: An influential biologist who presented the first well-supported theory of how evolution works.
    • Published On the Origin of Species by Means of Natural Selection in 1859, a book that profoundly impacted scientific thought and public perception.
    • Followed with The Descent of Man in 1871, which explored human evolution and humanity's relationship to other animals.

1.4a Evolution, Selection, and Adaptation

  • Evolution: Defined as a change in the genetic composition of a population of organisms over generations. An example is the development of bacterial resistance to antibiotics.
  • Natural Selection: The mechanism by which evolution works.
    • Selection Pressures: Forces within the environment that favor the reproductive success of some individuals over others (e.g., presence of predators, scarcity of food).
    • Adaptations: Inherited features of anatomy and physiology that have evolved in response to selection pressures and enhance an organism's ability to survive and reproduce successfully in its environment (e.g., better camouflage for prey animals).

1.4c Walking Upright (Bipedalism)

  • Bipedalism: The ability to stand and walk on two legs.
  • Advantages and Adaptations:
    • Spotting Predators: Standing upright allows for a wider field of vision, helping to detect threats earlier.
    • Carrying: Frees the upper limbs to carry food, tools, and infants, which was crucial for survival and social development.
    • Environmental Context: An adaptation suited to living on the savanna (grassland) as Africa became progressively hotter and drier.
    • Anatomical Modifications: Required significant skeletal and muscular modifications in the spine, pelvis, and lower limbs.
    • Family Structure Changes: Contributed to changes in social and family structures, possibly promoting pair-bonding and division of labor.
  • Genetic Divergence: Humans and chimpanzees differ by approximately 1.6\% of their DNA, highlighting our close evolutionary relationship while accounting for significant phenotypic differences.
  • Impact on Human Intelligence: "Powerful selective forces were at work to evolve organisms with grace and agility, accurate binocular vision, versatile manipulative abilities, superb eye-hand coordination, and an intuitive grasp of Newtonian gravitation. But each of these skills required significant advances in the evolution of brains and particularly the neocortices of our ancestors. Human intelligence is fundamentally indebted to the millions of years our ancestors spent aloft in the trees." (p.83)

1.5a The Hierarchy of Complexity

  • Human organization follows a successive hierarchy, with each level composed of simpler parts and contributing to the complexity of the next level:
    • Organism: A single, complete individual (e.g., a human being).
    • Organ System: A group of organs that work together to perform a unique collective function (e.g., the circulatory system, respiratory system, digestive system).
    • Organ: A structure composed of two or more different tissue types that work together to carry out a specific function. Organs have defined anatomical boundaries and can sometimes contain smaller organs within them (e.g., the stomach, heart).
    • Tissue: A mass of similar cells and cell products that forms a discrete region within an organ and performs a specific function (e.g., muscle tissue, nervous tissue).
    • Cell: The smallest unit capable of carrying out all the basic functions of life. It is the fundamental unit of structure and function in living organisms.
    • Organelle: A structure within a cell that carries out specific functions necessary for the cell's survival (e.g., mitochondria, nucleus).
    • Molecule: A particle composed of two or more atoms chemically bonded together.
      • Macromolecules: The largest and most complex molecules, essential for life, including proteins, fats (lipids), and DNA.
    • Atom: The smallest particle of an element that retains its unique chemical identity.

1.6a Characteristics of Life

  • Life is defined by a collection of properties that differentiate living things from nonliving things:
    • Organization: Living things exhibit a higher level of structural and functional organization than nonliving things, with precise arrangements of parts.
    • Cellular Composition: All living matter is compartmentalized into one or more cells, the basic units of life.
    • Metabolism: The sum of all internal chemical changes that occur in an organism, including anabolism (synthesis) and catabolism (breakdown).
    • Responsiveness (Excitability): The ability of living organisms to sense and react to changes (stimuli) in their environment, allowing them to adapt and survive.
    • Movement: The ability to change location either of the entire organism or of substances within the organism (e.g., blood flow, cellular transport).

1.6c Negative Feedback and Homeostasis

  • Homeostasis: The ability of an organism to detect changes, activate mechanisms that oppose these changes, and thereby maintain relatively stable internal conditions.
    • Walter Cannon (1871–1945): Coined the term "homeostasis."
  • Negative Feedback: The primary mechanism for maintaining homeostasis.
    • It allows for a dynamic equilibrium within a limited range around a set point.
    • The body senses a change (deviation from the set point) and "negates" or reverses it, bringing the variable back towards the set point.
    • Loss of homeostatic control can lead to illness or death.
    • Feedback Loops: Mechanisms that alter the original changes that triggered them.
  • Examples of Homeostasis:
    • Body Temperature Regulation:
      • If too warm: Skin blood vessels dilate (vasodilation) to increase blood flow near the surface, and sweating begins. These are heat-losing mechanisms.
      • If too cold: Skin blood vessels constrict (vasoconstriction) to reduce blood flow near the surface, and shivering begins (muscle contractions generate heat). These are heat-gaining mechanisms.
    • Blood Pressure Regulation (Baroreflex):
      • When rising from bed, blood drains from the head, causing blood pressure to fall in that region.
      • This drop is detected by baroreceptors (stretch receptors in arteries near the heart and neck) that transmit signals to the cardiac center of the brainstem.
      • The cardiac center then transmits signals to the heart to increase heart rate, which in turn raises blood pressure, restoring homeostasis.
  • Common Components of a Feedback Loop:
    • Receptor: A structure that senses a change in the body (e.g., baroreceptors monitoring blood pressure).
    • Integrating (Control) Center: A control center (often in the brain or endocrine gland) that processes the sensory information, "makes a decision" by comparing it to a set point, and directs a response (e.g., the cardiac center of the brainstem).
    • Effector: A cell or organ that carries out the final corrective action to restore homeostasis (e.g., the heart increasing its rate).

1.6d Positive Feedback and Rapid Change

  • Positive Feedback: A self-amplifying cycle that leads to greater change in the same direction, further accelerating the initial stimulus, rather than correcting it as in negative feedback.
  • Purpose: It is a normal way of producing rapid and significant changes in the body.
  • Examples:
    • Childbirth: Uterine contractions stimulate oxytocin release, which in turn increases contractions, pushing the fetus toward the cervix, amplifying the process until birth.
    • Blood Clotting: Platelets release chemicals that attract more platelets to the injury site, forming a plug that grows rapidly.
    • Protein Digestion: Enzymes activate other enzymes, leading to a cascade of digestion.
    • Generation of Nerve Signals: A small depolarization leads to greater depolarization, propagating the signal.
  • Potential Danger: Positive feedback can sometimes be dangerous, such as during a vicious circle of runaway fever, where increasing body temperature further accelerates metabolic rate, generating more heat and potentially causing tissue damage.

1.6e Gradients and Flow

  • Fundamental Principle: Matter and energy in the body tend to flow down gradients.
  • Gradient: A difference in chemical concentration, electrical charge, temperature, or pressure between two points.
  • Types of Gradients and Flow:
    • Pressure Gradient: Blood flows from a region of higher pressure to a region of lower pressure (e.g., from the heart to peripheral tissues).
    • Concentration Gradient: Chemicals flow from an area of higher concentration to an area of lower concentration (e.g., dietary glucose moving into intestinal cells).
    • Electrical Gradient: Charged particles flow from an area of higher electrical charge to an area of lower electrical charge (e.g., sodium ions moving across a cell membrane channel).
    • Electrochemical Gradient: A combination of both concentration and electrical gradients, influencing the movement of ions.
    • Thermal Gradient: Heat flows from a region of higher temperature to a region of lower temperature (e.g., heat moving from warm blood to cooler skin and then to cool air).
  • Movement Up the Gradient: Movement in the opposite direction (against the gradient) requires the expenditure of metabolic energy (e.g., active transport pumps).

1.7b Analyzing Medical Terms

  • Anatomical Terminology: Largely based on specific word elements:
    • Roots (Stems): Carry the core meaning of the term.
    • Combining Vowels: Often used to join roots together to form a complete word.
    • Prefixes and/or Suffixes: May be added to modify the meaning of the root word.
  • Acronyms: Pronounceable words formed from the first letter, or the first few letters, of a series of words (e.g., PET scan – Positron Emission Tomography).

1.7c Plurals, Adjectives, and Possessive Forms

  • Plural Forms: Anatomical terms often have varied plural forms, much like Latin or Greek origins.
    • Examples: cortex (singular) vs. cortices (plural); corpus (singular) vs. corpora (plural).
  • Adjectives: An adjective modifying a noun in anatomical terminology often follows the noun it modifies.
    • Example: Biceps brachii (the two-headed muscle of the arm).
  • Adjectival vs. Noun Forms: The adjectival form of a term can look different from its noun form.
    • Example: brachium (noun, referring to the arm) vs. brachii (adjective, meaning "of the arm").

Medical Imaging

Radiography (X-rays)

  • Usage: Accounts for over half of all medical imaging procedures.
  • Mechanism: X-rays penetrate tissues to darken photographic film or digital sensors beneath the body. Dense tissues (e.g., bone) absorb more X-rays and appear white, while less dense tissues (e.g., muscle, fat) appear darker.
  • Radiopaque Substances: Can be injected or swallowed to fill hollow structures.
    • Used to visualize internal lumens, such as blood vessels (angiography) or the intestinal tract (barium studies).
  • Digital Subtraction Angiography (DSA): A specialized X-ray technique useful for highlighting blockages and blood flow patterns by subtracting a pre-contrast image from a post-contrast image.

Computed Tomography (CT scan)

  • Former Name: Previously known as a CAT scan.
  • Mechanism: Uses low-intensity X-rays emitted from multiple angles and computer analysis to create cross-sectional, "slice-type" images of the body.
  • Image Quality: Offers increased sharpness of internal structures compared to conventional X-rays, providing detailed views of soft tissues and bone.

Magnetic Resonance Imaging (MRI)

  • Advantages: Provides superior image quality for soft tissues compared to CT scans and involves no exposure to X-rays (ionizing radiation).
  • Mechanism: Utilizes strong magnetic fields and radio waves to generate detailed images of internal organs and soft tissues by detecting the behavior of hydrogen atoms in the body.
  • Best for Soft Tissue: Excellent for visualizing the brain, spinal cord, ligaments, and cartilage.
  • Functional MRI (fMRI): A specialized MRI technique that shows real-time changes in brain activity by detecting changes in blood flow.

Positron Emission Tomography (PET)

  • Purpose: Primarily assesses the metabolic state of tissues, indicating how active they are.
  • Mechanism: A radioactively labeled glucose analogue (e.g., fluorodeoxyglucose, F.D.G.) is injected into the patient. Tissues that are metabolically active (and thus use more glucose) will absorb more of the tracer.
  • Image Interpretation: The image color shows which tissues are using the most glucose at that moment. Damaged or less active tissues (e.g., in a stroke or certain cancers) appear dark or show reduced uptake.

Sonography

  • Historical Context: The second oldest and second most widely used form of medical imaging.
  • Mechanism: Uses high-frequency sound waves that echo back from internal organs. A transducer emits sound waves, and the echoes are converted into an image.
  • Safety: Avoids harmful X-rays, making it particularly safe and suitable for obstetrics (imaging during pregnancy).
  • Image Quality: While safe, the image resolution is generally not as sharp or detailed as CT or MRI.