Introduction to Anatomy and Physiology: Foundational Concepts and Chemical Principles

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Chapter 1: Introduction to Anatomy and Physiology

Anatomy vs. Physiology

Anatomy and physiology are two closely related disciplines that form the foundation of medical science. Anatomy focuses on the structure of the body, while physiology examines its functions.

Anatomy: Study of structure (what the body is). Example: The heart has four chambers.
Physiology: Study of function (how the body works). Example: The heart pumps blood through circulation.
Relationship: Structure determines function; function reflects structure. Example: Thin alveoli walls in lungs allow efficient gas exchange.

Sub-Disciplines of Anatomy

Anatomy is divided into several subfields based on the scale and method of study.

Gross Anatomy: Study of large, visible structures. Example: The femur (thigh bone) studied in lab.
Microscopic Anatomy: Study of structures too small for the naked eye.
- Cytology: Study of cells. Example: Red blood cell shape relates to oxygen transport.
- Histology: Study of tissues. Example: Muscle tissue under a microscope.

Levels of Organization & Definitions

The human body is organized into hierarchical levels, each with specific definitions.

Atom: Smallest unit of matter (e.g., Hydrogen).
Molecule: Two or more atoms bonded (e.g., H2O).
Organic Molecule: Carbon-based (e.g., Glucose, C6H12O6).
Organelle: Functional structure in a cell (e.g., Mitochondria for ATP production).
Cell: Basic unit of life (e.g., Neuron).
Tissue: Group of similar cells performing a function.
Organ: Structure composed of multiple tissues (e.g., Heart).
Organ System: Multiple organs working together (e.g., Digestive system).
Organism: A complete living being (e.g., Human).

Organ Systems & Functions

Organ systems are groups of organs that perform major functions necessary for life.

Integumentary: Protection, regulates temperature. Example: Skin produces sweat to cool the body.
Skeletal: Support, protection. Example: Skull protects the brain.
Muscular: Movement, heat. Example: Shivering generates heat.
Nervous: Control, rapid responses. Example: Reflex when touching something hot.
Endocrine: Hormonal control. Example: Insulin lowers blood sugar.
Cardiovascular: Transport. Example: Heart pumps oxygenated blood.
Lymphatic/Immune: Defense. Example: Lymph nodes filter pathogens.
Respiratory: Gas exchange. Example: O2 enters body, CO2 exits.
Digestive: Breaks down food. Example: Enzymes in saliva start carbohydrate breakdown.
Urinary: Waste removal. Example: Kidneys filter urea into urine.
Reproductive: Produces offspring.

Homeostasis & Body Systems

Homeostasis is the maintenance of a stable internal environment, essential for survival.

Homeostasis: Stable internal environment. Example: Body temperature ~37°C (98.6°F).
Loss of Homeostasis: Leads to illness or death. Example: Diabetes (failure to regulate blood sugar).
Levels of Organization: Chemical → Cellular → Tissue → Organ → Organ System → Organism.
Feedback Systems:
- Negative Feedback: Reverses change (e.g., body temperature regulation, blood sugar).
- Positive Feedback: Enhances change (e.g., blood clotting, labor contractions).

Basic Anatomical Concepts

Tissue Types

Tissues are groups of similar cells that perform specific functions.

Epithelial: Stomach linings.
Connective: Bone and cartilage.
Muscle: Biceps, quadriceps.
Nervous: Brain.

Anatomical Position

The anatomical position is a standard reference for describing locations and directions on the human body.

Standing upright
Facing forward
Arms at sides
Palms forward
Feet slightly apart

Body Planes

Body planes are imaginary lines used to divide the body for anatomical study.

Sagittal: Divides left/right.
Frontal (Coronal): Divides front/back.
Transverse (Horizontal): Divides top/bottom.
Oblique: Angled cuts.

Anatomical Directions

Directional terms describe the locations of structures relative to other structures or locations in the body.

Superior/Inferior: Above/below
Anterior/Posterior: Front/back
Medial/Lateral: Toward/away from midline
Proximal/Distal: Closer/farther from point of origin
Superficial/Deep: Toward surface/away from surface

Body Cavities

Body cavities are spaces within the body that contain vital organs.

Dorsal: Cranial, vertebral.
Ventral: Thoracic (pleural, mediastinum, pericardial), abdominopelvic.
Boundaries: Diaphragm separates thoracic & abdominopelvic cavities.
Organs per Cavity: Thoracic: heart, lungs Abdominal: digestive organs Pelvic: bladder, reproductive organs

Abdominopelvic Regions/Quadrants

The abdominopelvic cavity is divided for clinical and anatomical reference.

Quadrants: RUQ, LUQ, RLQ, LLQ.
9 Regions: Right/Left hypochondriac, epigastric, right/left lumbar, umbilical, right/left iliac, hypogastric.

Basic Chemical Principles in Anatomy & Physiology

Subatomic Particles

Atoms are composed of subatomic particles that determine their properties and behavior.

Protons: (+), in nucleus, defines element.
Neutrons: Neutral, in nucleus, isotope variation.
Electrons: (–), orbit nucleus, involved in bonding.

Atomic Structure

Atomic structure is defined by the number of protons, neutrons, and electrons.

Atomic Number = Number of protons = Number of electrons.
Mass Number = Protons + Neutrons.
Example: = 6 protons, 6 neutrons.

Electron Shells

Electrons are arranged in shells or orbitals around the nucleus. The outermost shell is called the valence shell and determines chemical bonding.

Valence shell: Outermost shell — determines bonding.

Bond Types

Chemical bonds hold atoms together in molecules. The main types are covalent, ionic, and hydrogen bonds.

Covalent (strongest): Sharing electrons. Example: CO2, H2O
Ionic (medium): Transfer of electrons. Example: NaCl
Hydrogen (weakest): Attraction between partial charges. Example: Occurs between water and ammonia; water forms hydrogen bonds with other water molecules.
Ion: Charged atom (cation = +, anion = –).
Isotope: Atoms of the same element with different numbers of neutrons.

Table: Isotopes of Carbon

Isotope	Number of Protons	Number of Neutrons	Abundance
Carbon-12	6	6	98.9%
Carbon-13	6	7	1.1%
Carbon-14	6	8	<0.0001%

Chemical Reactions

Chemical reactions are processes in which substances are transformed into new products. They are essential for metabolism and cellular function.

Dehydration synthesis: Builds molecules, removes water.
Hydrolysis: Breaks molecules, adds water.
Reaction notation: Reactants → Products
Example: Glucose + Fructose → Sucrose + H2O

Equation:

Reactants: Glucose + Fructose
Products: Sucrose + Water

Water Properties

Water is vital for life due to its unique chemical properties.

Polar molecule: Dissolves charged molecules.
Hydrogen bonds: Form between water molecules.
Cohesion: Water molecules stick together (important for transport in plants and surface tension in lungs).
Adhesion: Water molecules stick to other substances.
Surface tension: Important in lung function.
Solvent properties: Dissolves many substances.
Role in temperature regulation & pH balance.

Dissociation of Water, Acids, Bases, and pH

Water can dissociate into ions, affecting pH and chemical reactions in the body.

Dissociation:
Acid: Releases H+ ions (e.g., HCl, pH 2).
Base: Releases OH- ions (e.g., NaOH, pH 13).
Neutral: pH 7 (e.g., water).
pH Scale: 0–6 acidic, 7 neutral, 8–14 basic.
Conversion:

Buffers

Buffers help maintain stable pH in biological systems by absorbing or releasing H+ ions.

Example: Bicarbonate buffer maintains blood pH at 7.4.
Equation:

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