Anatomy & Physiology: Foundational Concepts and Systems Overview

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Introduction to Anatomy & Physiology

Definition and Scope

Anatomy and physiology are foundational sciences in understanding the human body. Anatomy focuses on the structure and relationships of body parts, while physiology explores how these parts function and interact to sustain life.

Anatomy: Naming body parts and their relationships.
Physiology: How body parts work and carry out necessary functions.

Levels of organization in the body:

Atoms
Molecules
Cells
Tissues
Organs
Organ systems
Organism

Each level builds upon the previous, forming the complex structure and function of the human body.

Major Organ Systems: Functions and Key Organs

Overview of Body Systems

The human body is organized into systems, each with specific functions and major organs. Understanding these systems is essential for grasping how the body maintains health and responds to challenges.

Skeletal system: Protects and supports organs, provides framework for movement, stores minerals, and produces blood cells.
Muscular system: Facilitates movement, maintains posture, and produces heat.
Nervous system: Controls and coordinates body activities, responds to internal and external changes.
Endocrine system: Regulates processes via hormones (growth, reproduction, nutrient use).
Cardiovascular system: Transports blood, oxygen, nutrients, and waste throughout the body.
Lymphatic/Immunity system: Returns leaked fluids to blood, disposes of debris, and mounts immune responses.
Respiratory system: Supplies oxygen and removes carbon dioxide.
Digestive system: Breaks down food for absorption and eliminates waste.
Urinary system: Regulates water, electrolytes, acid-base balance, and removes waste.
Reproductive system: Produces offspring.

Survival Needs of the Human Body

Essential Requirements

To survive, the human body requires several key elements:

Nutrients: Chemicals for energy and cell building.
Oxygen: Required for energy release from food.
Water: Most abundant chemical, necessary for chemical reactions.
Normal body temperature: Needed for metabolic reactions.
Appropriate atmospheric pressure: Necessary for proper breathing and gas exchange.

Homeostasis

Definition and Mechanisms

Homeostasis is the maintenance of a stable internal environment. Organ systems work together to keep conditions within narrow limits.

Receptors: Monitor changes and send information to the control center.
Control Center: Determines the set point and analyzes input; directs response.
Effectors: Carry out responses to restore balance.

Feedback mechanisms:

Negative feedback: Reduces or shuts off the original stimulus (e.g., body temperature regulation).
Positive feedback: Enhances or exaggerates the original stimulus (e.g., labor contractions, blood clotting).

Example of negative feedback:

Body temperature falls → temperature-sensitive cells in skin → thermoregulatory center in brain → skeletal muscles contract (shiver) → body temperature rises, stimulus ends.

Example of positive feedback:

Labor contractions → oxytocin release → increased contractions until delivery.

Anatomical Position and Directional Terms

Standard Anatomical Position

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

Body erect, feet slightly apart, palms facing forward, thumbs pointing away from body.

Directional Terms

Superior (cranial): Toward the head or upper part of the body.
Inferior (caudal): Away from the head or toward the lower part.
Anterior (ventral): Toward the front of the body.
Posterior (dorsal): Toward the back of the body.
Medial: Toward the midline.
Lateral: Away from the midline.
Proximal: Closer to the origin of a body part.
Distal: Farther from the origin.
Superficial (external): Toward or at the body surface.
Deep (internal): Away from the body surface.

Body Regions, Planes, and Sections

Regional Terms

Axial: Head, neck, trunk.
Appendicular: Limbs (arms and legs).

Body Planes

Sagittal plane: Divides body into right and left parts.
Midsagittal (median) plane: Cut made perfectly on midline.
Parasagittal plane: Cut off-centered, not on midline.
Frontal (coronal) plane: Divides body into anterior and posterior parts.
Transverse (horizontal) plane: Divides body into superior and inferior parts.
Oblique section: Cuts at angles other than 90 degrees to vertical plane.

Body Cavities and Membranes

Major Body Cavities

The body contains several cavities that protect organs and allow for organ movement and growth.

Cavity	Main Organs
Dorsal (cranial & vertebral)	Brain, spinal cord
Thoracic	Lungs, heart, esophagus, trachea
Abdominopelvic	Stomach, intestines, spleen, liver, bladder, reproductive organs

Membranes:

Parietal serosa: Lines cavity walls.
Visceral serosa: Covers internal organs.
Serous fluid: Fills space between layers, reduces friction.

Specific membranes:

Pericardium: Heart
Pleura: Lungs
Peritoneum: Abdominopelvic cavity

Abdominopelvic Quadrants and Regions

Quadrant	Location
RUQ	Right upper quadrant
LUQ	Left upper quadrant
RLQ	Right lower quadrant
LLQ	Left lower quadrant

Regions (used by anatomists):

Right hypochondriac
Epigastric
Left hypochondriac
Right lumbar
Umbilical
Left lumbar
Right iliac (inguinal)
Hypogastric (pubic)
Left iliac (inguinal)

Other Body Cavities

Oral and digestive cavities
Nasal cavities
Orbital cavities
Middle ear cavities
Synovial cavities (joint cavities, not exposed to environment)

Forms of Energy in the Body

Types of Energy

Chemical energy: Stored in chemical bonds.
Electrical energy: Movement of charged particles (e.g., nerve impulses).
Mechanical energy: Directly involved in moving matter (e.g., muscle contraction).
Radiant/Electromagnetic energy: Travels in waves (e.g., light, x-rays).
Kinetic energy: Energy of motion.
Potential energy: Stored energy.

Atomic Structure and Subatomic Particles

Characteristics of Subatomic Particles

Protons: Positive charge (+), mass = 1 amu.
Neutrons: No charge, mass = 1 amu.
Electrons: Negative charge (-), virtually no mass.

Atoms are electrically neutral when the number of protons equals the number of electrons.

Planetary Model: Electrons orbit nucleus in circular paths (simplified illustration).

Common Elements in the Human Body

Key Elements

Na – Sodium
Cl – Chlorine
O2 – Oxygen
K – Potassium
N – Nitrogen
H – Hydrogen
Ca – Calcium

Cations and Anions

Definitions

Anion (negative charge): Atom that gained one or more electrons.
Cation (positive charge): Atom that lost one or more electrons.

Types of Mixtures

Classification and Examples

Solutions: Homogenous, evenly distributed (e.g., air, salt solution).
Colloids: Heterogeneous, not evenly distributed, can undergo sol-gel transformations (e.g., cytosol).
Suspensions: Heterogeneous, large particles settle out (e.g., sand in water).

Solvent: Substance present in greatest amount (usually water in the body).

Solute: Substance dissolved in solvent (e.g., glucose in blood).

Chemical Bonds and Reactions

Bond Formation and Strength

Ionic bonds: Transfer of electrons between atoms.
Covalent bonds: Sharing of electrons between atoms.
Hydrogen bonds: Weak attractions between molecules.

Synthesis vs. Decomposition Reactions

Synthesis: Atoms/molecules combine to form larger, more complex molecules. Used in anabolic (building) processes.
Decomposition: Molecules broken down into smaller molecules or atoms. Used in catabolic (breaking down) processes.

General reaction rate equation:

Properties of Water

Key Properties

High heat capacity: Absorbs and releases heat with little temperature change.
High heat of vaporization: Evaporation requires large amounts of heat.
Polar solvent properties: Dissolves and dissociates ionic substances.
Reactivity: Participates in chemical reactions.
Cushioning: Protects organs from physical trauma.

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