Introduction to Anatomy & Physiology

Overview

Anatomy and physiology are foundational sciences in understanding the human body. Anatomy focuses on the structure and form of body parts, while physiology explores the chemical and physical processes that enable body functions.

• Anatomy: The scientific study of the body's structures. This includes both internal and external features.

• Physiology: The study of the chemistry and physics of the body, focusing on how structures work together to support life.

Example: Measuring blood pressure involves understanding both the anatomical location of arteries and the physiological process of blood flow.

Major Subdivisions of Anatomy

Types of Anatomy

Anatomy can be divided into several specialized fields, each focusing on different aspects of body structure.

• Gross Anatomy: Study of structures visible without a microscope.

• Microscopic Anatomy: Study of structures requiring magnification, including:

  • Cytology: Study of cells.

  • Histology: Study of tissues.

• Regional Anatomy: Study of structures within a specific area (e.g., head and neck).

• Systemic Anatomy: Study of structures within a specific organ system (e.g., digestive system).

Example: An ENT (Ear, Nose, and Throat) doctor specializes in regional anatomy of the head and neck.

Major Subdivisions of Physiology

Types of Physiology

Physiology is often divided by organ systems or specific functions.

• Organ Physiology: Study of individual organs.

• Systemic Physiology: Study of organ systems.

• Homeostasis: The body's ability to maintain internal stability despite external changes.

Example: Studying how the heart pumps blood (cardiac physiology) and how the body regulates temperature (thermoregulation).

Levels of Structural Organization

Six Levels of Organization

The human body is organized into six levels, from the smallest chemical building blocks to the complete organism.

1. Chemical Level: Atoms (e.g., hydrogen, oxygen, carbon) and molecules (e.g., H2O).

2. Cellular Level: Organelles (e.g., nucleus, mitochondria) and cells, the smallest independently functional units.

3. Tissue Level: Groups of similar cells performing specific functions.

4. Organ Level: Anatomically distinct structures composed of two or more tissue types.

5. Organ System Level: Groups of organs working together to perform major functions.

6. Organism Level: The complete living human being.

Example: Muscle tissue (tissue level) forms the heart (organ level), which is part of the cardiovascular system (organ system level).

Major Organ Systems of the Human Body

Overview of Eleven Organ Systems

The human body contains eleven major organ systems, each with specific functions and associated organs.

Functions of Human Life

Organization

Organization is essential for proper function. Compartments and membranes keep body parts separate, protected, moist, and nourished.

• Example: The digestive tract is considered an external environment, separated from internal tissues.

Metabolism, Anabolism, and Catabolism

Metabolism refers to all chemical reactions in the body. It includes:

• Anabolism: Building larger molecules from smaller ones; requires energy.

• Catabolism: Breaking down large molecules into smaller ones; releases energy.

Example: Breaking down starch into glucose (catabolism); synthesizing proteins from amino acids (anabolism).

Key Equation:

Additional info: ATP (adenosine triphosphate) stores energy for cellular processes.

Responsiveness and Movement

Responsiveness is the ability to sense and react to stimuli. Movement includes both voluntary and involuntary actions.

• Example: Lifting your foot after stepping on a tack (responsiveness); running (movement).

Growth, Differentiation, and Reproduction

• Growth: Increase in body size and number of cells.

• Differentiation: Unspecialized cells become specialized (e.g., stem cells to red blood cells).

• Reproduction: Formation of new organisms from parent organisms.

Requirements for Human Life

Oxygen and Nutrients

Oxygen is required for cellular respiration and ATP production. Nutrients include water, carbohydrates, lipids, vitamins, and minerals.

• Water: Largest component of cells and fluids (about 70% of body mass).

• Energy-yielding nutrients: Carbohydrates and lipids.

• Micronutrients: Vitamins and minerals (fat-soluble are stored, water-soluble are not).

Temperature Regulation

Human survival depends on maintaining a narrow temperature range. Proteins control chemical reactions, and temperature affects their function.

• Heat: Sweating cools the body but requires water.

• Cold: Shivering generates heat; blood flow decreases to extremities to preserve core temperature.

• Extreme temperatures: Can cause irreversible protein changes (e.g., cooking an egg), frostbite, or heat stroke.

Atmospheric Pressure

Atmospheric pressure is necessary to keep gases in the body in the correct state and to ensure proper blood flow.

• Too little pressure: Impairs oxygen delivery.

• Too much pressure: Can damage blood vessels.

Homeostasis

Role in Healthy Functioning

Homeostasis is the steady state maintained by body systems. It involves keeping physiological values within a normal range.

• Set point: The ideal physiological value.

• Normal range: The range of values best for health.

Feedback Mechanisms

• Negative Feedback: Reverses deviations from the set point. Example: Regulation of body temperature.

• Positive Feedback: Intensifies a change until an endpoint is reached. Example: Childbirth, blood clotting.

Negative Feedback Loop Steps:

1. Stimulus: Event outside normal range

2. Sensor (receptor): Monitors value

3. Control Center: Compares to normal range, activates effector

4. Effector: Causes change to return to normal

Anatomical Terminology

Anatomical Position

The standard anatomical position is used for consistency in describing body parts.

• Standing upright (or lying face up)

• Feet shoulder-width apart, toes forward

• Upper limbs at sides, palms facing forward

Directional Terms

Directional terms describe locations and relationships of body parts.

• Anterior (ventral): Toward the front

• Posterior (dorsal): Toward the back

• Superior: Above or higher

• Inferior: Below or lower

• Lateral: Toward the side

• Medial: Toward the middle

• Proximal: Nearest to point of attachment

• Distal: Farther from point of attachment

• Superficial: Closer to surface

• Deep: Farther from surface

Body Planes

Three planes are commonly used in anatomy and medical imaging:

• Sagittal Plane: Divides body into right and left sides. Midsagittal is exactly in the middle; parasagittal is off-center.

• Frontal (Coronal) Plane: Divides body into anterior (front) and posterior (back) parts.

• Transverse Plane: Divides body horizontally into upper and lower portions; produces cross sections.

Serous Membranes

Serous membranes (serosa) line the walls and organs of the thoracic and abdominopelvic cavities.

• Parietal layer: Lines the cavity wall.

• Visceral layer: Covers the organ.

• Serous space: Thin, fluid-filled cavity between layers.

• Function: Cushions and reduces friction on internal organs during movement (e.g., lungs inflating, heart beating).