Anatomy & Physiology: Foundational Concepts, Organ Systems, and Cellular Structure

Getting Started: Scientific Method and Measurement

Scientific Method

The scientific method is a systematic approach used in scientific investigation to ensure objective and reproducible results.

• Observation: Careful focus on the subject of study.

• Hypothesis: An unproven conclusion or educated guess based on facts.

• Data Collection:

  • Qualitative observation: Uses senses to gather information.

  • Quantitative observation: Uses scientific equipment to measure variables (e.g., density, mass).

  • Experiments: Procedures to determine cause-effect relationships under controlled conditions.

  • Independent variable: Factor changed by the experimenter.

  • Dependent variable: Factor that changes in response to the independent variable.

  • Control: Sample or system under normal circumstances for comparison.

• Manipulation and Analysis of Data:

  • Range: Highest value - lowest value

  • Mean: Sum of items divided by number of items

  • Percent: Expressed to two decimal places (e.g., 25% = 0.25)

• Graphs: X-axis represents the independent variable, Y-axis the dependent variable.

• Curve: A line connecting data points on a graph.

• Reporting Conclusion:

  • Theory: Hypothesis validated many times.

  • Biological Principle: Widely verified and used theory.

Metrics and Measurement

The metric system is a standardized, non-varying system of measurement based on tens.

• Length:

  • Meter (m): Metric unit of length

  • Centimeter (cm): Hundredth of a meter

  • Millimeter (mm): Thousandth of a meter

  • Micrometer (μm): Millionth of a meter

• Volume:

  • Liter (L): Metric unit of volume

  • Milliliter (mL): Thousandth of a liter

• Mass:

  • Gram (g): Metric unit of mass

  • Weight: Varies due to gravitational force acting on mass

Temperature Measurements

• To find Celsius: $^\circ F = (95/5) \times ^\circ C + 32$

• To find Fahrenheit: $^\circ C = ( ^\circ F - 32 ) / 1.8$

Organ Systems

Overview of Organ Systems

An organ system is a group of organs working together to perform a specific function. Each system is composed of two or more tissue types.

• Integumentary System: Skin, epidermis, dermis, sense organs. Functions: protection, excretion, body temperature regulation.

• Skeletal System: Bones, ligaments, tendons, joints. Functions: support, protection, movement, blood cell formation.

• Muscular System: Muscles. Functions: movement, heat production.

• Nervous System: Brain, spinal cord, nerves. Functions: body homeostasis, communication, activation of muscles and glands.

• Endocrine System: Glands. Functions: body homeostasis, communication.

• Lymphatic System: Lymph, lymphatic vessels, white blood cells. Functions: immunity, fluid balance.

• Cardiovascular System: Heart, blood, blood vessels. Functions: transport of oxygen, nutrients, carbon dioxide, waste.

• Respiratory System: Nasal cavity, trachea, lungs. Functions: oxygen intake, carbon dioxide removal.

• Digestive System: Stomach, intestines, etc. Functions: ingestion, digestion, excretion of food.

• Urinary System: Bladder, kidneys, ureters, urethra. Functions: excretion of nitrogenous wastes.

• Reproductive System: Genitals. Function: perpetuation of the species.

Key Structures to Know

• Thymus

• Heart

• Lungs

• Trachea

• Esophagus

• Primary bronchi

• Diaphragm

• Stomach

• Pancreas

• Small intestine

• Cecum

• Large intestine

• Rectum

• Anus

• Spleen

• Liver

• Kidneys

• Ureter

• Urinary bladder

• Inferior and superior vena cava

• Descending aorta

• Vagina

• Urethra

• Uterine tube

• Vas/Ductus deferens

• Prostate gland

• Testes

• Vermiform appendix

The Language of Anatomy

Anatomical Position and Body Landmarks

The anatomical position is the universally accepted standard position: standing upright, arms down, palms facing forward.

• Abdominal: Anterior body trunk inferior to the ribs

• Brachial: Arm

• Carpal: Wrist

• Cervical: Neck

• Digital: Fingers

• Femoral: Thigh

• Inguinal: Groin

• Mammary: Breast

• Nasal: Nose

• Oral: Mouth

• Orbital: Eye

• Patellar: Knee cap

• Pelvic: Pelvis

• Pubic: Genital

• Thoracic: Chest

Body Orientation and Directional Terms

• Superior/Inferior: Above/below

• Anterior/Posterior: Front/back

• Medial/Lateral: Toward/away from midline

• Cephalad/Caudal: Head/tail (in four-legged animals)

• Dorsal/Ventral: Back/belly side

• Proximal/Distal: Closer/further from trunk

• Superficial/Deep: Surface/internal

Body Planes and Sections

• Sagittal (Longitudinal) Plane: Cuts body into right and left halves

• Frontal Plane: Cuts body into anterior and posterior (also called Coronal plane)

• Transverse (Cross) Plane: Cuts body into superior and inferior, perpendicular to median section

Body Cavities

• Dorsal Body Cavity:

  • Cranial cavity: Holds the brain

  • Spinal cavity: Holds the spinal cord

• Ventral Body Cavity:

  • Thoracic cavity: Holds heart and lungs

  • Abdominopelvic cavity: Holds digestive organs, pelvic organs

Abdominal Quadrants and Regions

• Quadrants:

  • Right Upper Quadrant (RUQ)

  • Left Upper Quadrant (LUQ)

  • Right Lower Quadrant (RLQ)

  • Left Lower Quadrant (LLQ)

• Regions:

  • Right Hypochondriac, Epigastric, Left Hypochondriac

  • Right Lumbar, Umbilical, Left Lumbar

  • Right Iliac, Hypogastric, Left Iliac

Other Body Cavities

• Oral cavity: Mouth, teeth

• Nasal cavity: Respiratory system

• Orbital cavity: Eyes

• Middle ear cavity: Propagates sound waves

• Synovial cavity: Freely moving joints (e.g., knee)

Serous Membranes of the Ventral Cavity

Serosa is a double-layered membrane covering body cavities and organs. It consists of:

• Parietal layer: Adheres to cavity walls

• Visceral layer: Adheres to organs

Examples:

• Peritoneum: Abdominal cavity

• Pleura: Lungs

• Pericardium: Heart

Mucous Membranes

Mucous membranes are composed of epithelial cells on a loose connective tissue base. They line cavities open to the exterior and secrete mucus.

Microscopy and The Cell

The Microscope

Microscopes are essential tools for viewing cells and tissues at high magnification.

• Compound Microscope:

  • Base, substage light, stage, condenser, iris diaphragm lever, coarse/fine adjustment knobs, head, arm, ocular (eyepiece), objective lenses

  • Magnification: Low power (10x), high power (45x), oil immersion (100x)

• Stereo/Dissecting Microscope: Used for larger specimens, lower magnification

• Resolution: Ability to distinguish two close objects as separate

• Parfocal: Specimens remain in focus when magnification is changed

• Microscopic Field: Area seen at various magnifications; decreases at higher magnification

• Equation for changing microscopic fields: $\text{Size in mm of field at smallest magnification} \times \text{total magnification of smallest magnification} / \text{total magnification of desired field}$

• Depth of field: Depth at which specimen is clearly in focus

The Cell

The cell is the basic structural and functional unit of all living things. It maintains boundaries and performs metabolic functions.

• Nucleus: Contains genetic material (DNA), chromatin (loose DNA), chromosomes (condensed DNA), nucleoli (ribosome production), nuclear membrane (double-layered, with pores).

• Plasma Membrane: Boundary between inside and outside of cell; composed of phospholipid bilayer with embedded proteins. Microvilli are finger-like projections increasing surface area.

• Cytoplasm: Contains organelles and cytosol.

Cell Organelles and Functions

• Ribosome: Site of protein synthesis

• Endoplasmic Reticulum (ER): Tubular system for transport; rough ER (with ribosomes), smooth ER (lipid synthesis)

• Golgi Apparatus: Modifies and packages proteins

• Lysosomes: Contain digestive enzymes

• Peroxisomes: Contain peroxidase, detoxify substances

• Mitochondria: Site of ATP production

• Cytoskeletal Elements:

  • Microtubules: Part of spindle

  • Intermediate Filaments: Resist mechanical forces

  • Microfilaments: Cell movement, plasma membrane stability

  • Centrioles: Direct formation of spindle, basis for cilia/flagella

• Inclusions: Areas where substances are found suspended in cytosol

Cell Division

• Mitosis: Nuclear division

• Cytokinesis: Cytoplasm division

• Both produce two identical daughter cells

• Interphase: Cell grows, performs metabolic activity, DNA replicates

• Phases of Mitosis:

  • Prophase: Chromatin condenses into chromosomes

  • Metaphase: Chromosomes align at the cell's equator

  • Anaphase: Chromatids separate, cytokinesis begins

  • Telophase: Chromosomes diffuse, nucleus reforms, cytokinesis ends

• Cytokinesis: End of cell division; two daughter cells are formed

Table: Comparison of Organ Systems

Organ System	Main Organs	Main Functions
Integumentary	Skin, sense organs	Protection, excretion, temperature regulation
Skeletal	Bones, ligaments, tendons	Support, protection, movement, blood cell formation
Muscular	Muscles	Movement, heat production
Nervous	Brain, spinal cord, nerves	Homeostasis, communication
Endocrine	Glands	Homeostasis, communication
Lymphatic	Lymph, lymphatic vessels, WBCs	Immunity, fluid balance
Cardiovascular	Heart, blood, vessels	Transport of substances
Respiratory	Lungs, trachea, nasal cavity	Oxygen intake, CO2 removal
Digestive	Stomach, intestines	Ingestion, digestion, excretion
Urinary	Bladder, kidneys, ureters, urethra	Excretion of wastes
Reproductive	Genitals	Perpetuation of species

Additional info: Academic context and expanded explanations have been added to ensure completeness and clarity for college-level Anatomy & Physiology students.