CH1 - INTRO & TERMINOLOGY -

Overview: course purpose and structure

• Anatomy and Physiology I uses a two-part approach: anatomy (structure, memorization) and physiology (function, critical thinking and application).

• The course emphasizes that anatomy determines physiology: to understand how something works, you must understand its structure.

• The lab focuses on anatomy (structures, tissue composition, histology) while the lecture focuses on physiology (how and why things work).

• The DVD is designed to help you review material at your own pace and prepare for upcoming lectures, covering topics in greater detail than a single lecture.

Core concepts: levels of organization in the body

• Begin with the chemical level of organization.

  • Elements (examples given): sodium, potassium, chlorine.

  • Elements combine to form inorganic compounds (e.g., water, sodium chloride) that lack a carbon backbone.

  • Organic compounds (carbohydrates, proteins, fats, etc.) contain carbon.

  • The chemical level is foundational for understanding all higher levels.

• From chemicals to organelles:

  • Organelles are structures inside cells with specific functions (e.g., the nucleus).

  • Organelles and their surrounding environment (the cytoplasm, cytosol) determine cellular function.

• From organelles to cells:

  • Cells are the basic units of living things.

  • Cells contain organelles and chemicals and perform specific functions.

• From cells to tissues:

  • Tissues are cohorts of cells working together to perform a function.

  • Examples of tissue types: muscle tissue, epithelial tissue (covers surfaces), nervous tissue.

• From tissues to organs:

  • Organs are made of multiple tissue types that collaborate to perform a common function.

  • Example: the stomach contains muscle tissue (contracts), nervous tissue (signals), epithelial tissue (surface lining).

• From organs to body systems:

  • Organs organize into body systems (e.g., digestive system includes stomach, intestines, etc.).

• Practical example: humerus as an organ:

  • The humerus is an organ because it contains multiple tissue types (bone tissue, blood vessels/bone marrow, adipose tissue).

• Emphasis for study:

  • Always relate a structure to its place in the levels of organization when studying anatomy.

Regional anatomy, terminology, and anatomy position

• Regional anatomy involves memorization of terms for different body regions.

• Anatomical position: the standard reference position.

  • Feet hip-width apart, arms at sides, palms facing forward, body facing forward.

  • This position ensures consistency in describing locations.

• Practical notes on position:

  • Drawings may omit a silhouette; you must infer orientation (e.g., radial artery is on the thumb side in anatomical position).

• Learn regional terms and practice pronunciation; flashcards are recommended, with terms on one side and meanings on the other.

• Examples of regional terms:

  • Acromial region: shoulder region (adjective form: acromial; noun: acromion).

  • Brachial region: upper arm.

  • Other terms to know include brachial artery, biceps brachii, brachialis (location context ships with the term).

• Why terms matter:

  • These terms will be used repeatedly across anatomy and physiology courses.

  • Pronunciation guides from online medical dictionaries can help with correct usage.

• Key concept: anatomical position relevance in labeling and orientation of structures along the arm (e.g., the lateral side is away from the midline; medial is closer to the midline).

Sections of the body (sectional anatomy)

• Three primary body sections:

  • Sagittal section: divides body into left and right parts.

  • Midsagittal (median) section: a sagittal section that divides the body into equal left and right halves.

  • Frontal (coronal) section: separates anterior (front) and posterior (back) parts.

  • Transverse (cross) section: divides the body into superior (top) and inferior (bottom) parts.

• Why sectional anatomy matters:

  • Many medical images (e.g., CT scans) are cross-sectional; understanding section types helps interpret images.

• Examples:

  • Brain: a midsagittal section cuts the brain into equal right/left parts.

  • Cross section of the brain shows a transverse slice.

  • Frontal section of lungs shows anterior vs posterior portions.

• lab applications:

  • In the lab, you may be asked to imagine or perform a frontal section of an organ (e.g., brain) to identify anterior/posterior relationships.

Directional and positional terms (human-focused; note animal differences)

• Directional terms describe relative locations between two structures (not absolute positions):

  • Superior (cranial) vs. inferior (caudal): above vs. below.

  • Cranial (toward head) vs. caudal (toward tail).

  • Medial vs. lateral: closer to midline vs. farther from midline.

  • Proximal vs. distal: closer to trunk vs. farther from trunk (especially for limbs).

  • Anterior (ventral) vs. posterior (dorsal): toward front vs. toward back in humans; note that ventral/dorsal change meaning in four-legged animals (ventral = belly side; dorsal = back).

• Examples from the skeleton:

  • Medial end of the clavicle is closer to the midline; lateral end is farther from the midline.

  • In the arm, the brachial (upper arm) region is proximal to the carpal (wrist) region; the carpal region is distal to the brachial region.

• Practical takeaway:

  • Depending on arm position, a given end can be described with different terms, but proximal/distal remain consistent with respect to the trunk.

Body cavities and protective coverings

• Dorsal body cavity:

  • Comprises two major areas: cranial cavity (brain) and spinal cavity (spinal cord).

  • The brain and spinal cord are surrounded by meninges (protective connective tissue) and completely enclosed by bone.

  • Meningitis is inflammation of the meninges, which can compress the brain/spinal cord if swelling occurs.

• Ventral body cavity:

  • Divided by the diaphragm into two main compartments: thoracic cavity (superior) and abdominal cavity (inferior).

  • The thoracic cavity is separated from the abdominal cavity by the diaphragm; the abdominal and pelvic regions can be collectively referred to as the abdominopelvic cavity.

• Thoracic cavity subdivisions:

  • Mediastinum: area between the lungs; contains the heart and esophagus.

  • Lungs: each is surrounded by pleura; two layers: visceral pleura (on the lung) and parietal pleura (lines the chest wall/diaphragm and rib cage).

  • Pleura helps reduce friction via serous fluid between the layers.

• Abdominal cavity coverings:

  • Peritoneum: serous membrane around abdominal organs; two layers:

  • Visceral peritoneum: covers organs.

  • Parietal peritoneum: lines the abdominal cavity wall.

  • Visceral peritoneum produces fluid that lubricates organ surfaces to minimize friction during movement (e.g., peristalsis, stomach expansion).

• Clinical relevance of cavities:

  • Peritoneal cavity infections (peritonitis) can spread if gut contents leak, because the visceral and parietal peritoneum create a potential space where bacteria can travel.

  • The appendix is covered by visceral peritoneum; rupture can lead to peritonitis.

• Summary of dorsal vs ventral relevance:

  • Dorsal cavity is bone-protected (brain and spinal cord) and surrounded by meninges.

  • Ventral cavity houses thoracic and abdominal organs, each with protective serous membranes (pleura around lungs; peritoneum around abdominal organs).

Homeostasis and regulatory systems

• Homeostasis: maintaining the body within normal limits (set points) for various parameters.

  • Not just a definition to memorize; understand how regulatory systems keep the body within a normal range.

  • Example as a concept map: temperature and glucose homeostasis rely on feedback systems to return to the normal range.

• Regulatory systems involved:

  • Nervous system: fast responses (neural control), e.g., triggering sweating or shivering to regulate temperature.

  • Endocrine system: slower, hormonal responses that remodel physiology over time (insulin, glucagon, etc.).

• Temperature homeostasis (negative feedback):

  • Normal range conceptually represented by a set point band.

  • If body temperature rises: sweating increases to promote evaporative cooling and bring temperature back toward the set point.

  • If body temperature falls: skeletal muscle contractions (shivering) generate heat to bring temperature back toward the set point.

  • The role of proteins: maintaining temperature within a normal range is crucial for protein structure and function; extremes can denature proteins, potentially causing cell death.

• Glucose homeostasis (endocrine control):

  • Normal fasting blood glucose range is approximately 70 ext{ to } 100 ext{ mg/dL}.

  • High glucose after meals triggers insulin release: insulin promotes glucose uptake into cells, lowering blood glucose (negative feedback).

  • Low glucose triggers glucagon release: glucagon promotes glucose release into blood, raising blood glucose (negative feedback).

  • Brain dependence: the brain requires a constant glucose supply for normal function.

• Negative vs. positive feedback:

  • Negative feedback: deviation from normal range triggers responses to return to normal range (e.g., sweating, shivering, insulin/glucagon balance).

  • Positive feedback: deviation from normal range is amplified by the system; relatively rare in physiology but essential in specific processes:

  • Labor and delivery: stretch of cervix increases oxytocin release, which increases contractions, further stretching the cervix (positive feedback loop).

  • Blood clotting: platelets adhere and release chemicals that attract more platelets, accelerating clot formation.

  • Conceptual example: a student analogy where crowd encouragement amplifies performance can illustrate how positive feedback amplifies a response rather than returning to baseline.

• Practical implications:

  • Mastery of homeostasis requires understanding both nervous and endocrine contributions and recognizing when negative vs. positive feedback are at play.

  • The material underscores the importance of feedback systems for maintaining normal physiological function and the potential consequences if homeostasis is disrupted.

Connecting the concepts: why this matters for clinical understanding

• Understanding the levels of organization helps explain how a structure (e.g., a bone like the humerus) can be considered an organ, composed of tissues and cells, each contributing to its function within a system (musculoskeletal).

• Anatomical position and directional terms are essential for clear communication in clinical settings and when interpreting imaging (CT scans, MRIs) and anatomical diagrams.

• Sectional anatomy and body cavities provide the framework for understanding imaging findings and potential disease processes (e.g., pleural effusion, peritonitis).

• Homeostasis links structure and function by showing how anatomical components (nervous and endocrine organs, receptors, effectors) coordinate to keep internal environments stable, even as external conditions vary.

• Practical study tips emphasized:

  • Use flashcards to memorize regional terms and anatomical positions.

  • Practice interpreting sectional views and labeling regions.

  • Relate structures across levels (bone to tissue to cell) to reinforce understanding.

  • Seek clarification from instructors early if any concept remains unclear.

Key numerical references and formulas (LaTeX)

• Normal fasting blood glucose range (example):
  70 \,\text{mg/dL} \le \,\text{glucose}_{blood} \le 100 \,\text{mg/dL}

• Negative feedback (conceptual differential equation):
  \frac{dX}{dt} = -k \,(X - X_{set})

• Positive feedback (conceptual):
  \frac{dX}{dt} = +k \,(X - X_{set})

• Comparative notation for homeostasis:

  • Temperature regulatory cycle described qualitatively (sweating vs shivering) to maintain $T_{set}$ within a normal range.

  • Glucose homeostasis described with insulin and glucagon balancing blood glucose to keep brain fuel supply adequate.

Quick study tips and recap

• Revisit the levels of organization regularly and map a given structure to its place (chemicals → organelles → cells → tissues → organs → organ systems).

• Practice regional terminology with flashcards; pronounce terms; check pronunciation online if needed.

• Review anatomical position and directional terms until you can reliably describe locations in relation to one another.

• Use sectional anatomy examples (sagittal, midsagittal, transverse, frontal) to interpret images and model explanations.

• Understand the functional relevance of cavities and membranes (meninges, pleura, peritoneum) in protecting organs and enabling movement.

• Grasp homeostasis as a dynamic balance maintained by negative feedback most of the time; recognize clear examples and endpoints where positive feedback is essential.

• Connect theory to clinical implications (e.g., peritonitis from abdominal infection, meningitis from meninges inflammation) to understand why the material matters beyond exams.