Introduction to Anatomy & Physiology: Foundational Concepts and Terminology

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Anatomy & Physiology: Foundational Concepts

Anatomy

Anatomy is the study of the structure and shape of the body and its parts. It is derived from the Greek and Latin roots meaning "to cut up." Anatomy can be studied at different levels:

Macroscopic Anatomy (Gross Anatomy): Study of large structures visible to the naked eye. Examples include dissection, endoscopy, angiography, X-rays, and MRI.
Microscopic Anatomy: Study of very small structures, such as cells and tissues, which require a microscope to be seen. Examples include histology (study of tissues) and cytology (study of cells).

Additional info: Macroscopic anatomy is essential for understanding organ systems, while microscopic anatomy provides insight into cellular function and pathology.

Physiology

Physiology is the study of how the body and its parts work or function. The term comes from Greek roots meaning "nature" and "study." Physiology explains the mechanisms that keep the body alive and functioning.

Cells

Cells are the smallest unit of life. All living organisms are composed of cells, which carry out essential functions for survival.

Tissues

Tissues are groups of cells similar in shape and function that work together. The four main types of tissues are:

Epithelial
Connective
Muscle
Nervous

Organs and Organ Systems

Organs are made up of tissues. Organ systems are groups of organs that work together for a common purpose. Humans have 11 different organ systems, each with specific functions. Examples include the digestive system, cardiovascular system, and nervous system.

Each organ has a specific function and systems depend on each other (e.g., the digestive system relies on the circulatory system for transport of nutrients).

Integumentary System

The integumentary system forms the external body covering (skin). Its functions include:

Waterproofs and protects deeper tissue from injury
Contains cutaneous receptors (helps regulate temperature)
Excretes salts and urea

Nervous System

The nervous system is a fast-acting control system. The central nervous system (CNS) activates muscles and glands (effectors) in response to stimuli.

Cardiovascular (Circulatory) System

The cardiovascular system transports materials in the body via blood pumped by the heart. Materials transported include:

Oxygen
Carbon dioxide
Hormones
Nutrients
Wastes

Respiratory System

The respiratory system keeps blood supplied with oxygen and removes carbon dioxide. The term "spirare" means "to breathe."

Levels of Organization in the Body

The body is organized in a hierarchy from smallest to largest:

Quarks
Neutrons, Protons, Electrons
Atoms
Compounds and Molecules
Organelles
Cells
Tissues
Organs
Organ Systems
Organism
Population
Community
Ecosystems

Survival Needs

For survival, the body requires several essential needs:

Maintain Boundaries: Separation of internal and external environments.
Movement: Locomotion and movement of substances.
Respond/React: Ability to sense changes (stimuli) and respond.
Digest: Breakdown and delivery of nutrients.
Metabolism: Chemical reactions within the body, including anabolic (building) and catabolic (breaking down) processes.
Eliminate Waste: Removal of waste from metabolic reactions.
Reproduction: Production of future generations.
Growth: Increase in cell size and number.
Nutrients: Food contains chemicals for energy and cell building (carbohydrates, proteins, lipids, vitamins, minerals).
Oxygen: Required for chemical reactions to break down food and create energy.
Water: 60–80% of body weight; provides for metabolic reactions.
Standard Body Temperature: Maintained around 37°C.
Atmospheric Pressure: Necessary for breathing; force exerted by air on the body.

Homeostasis

Homeostasis is the maintenance of a stable internal environment. Imbalance in homeostasis can result in disease. The process involves:

Stimulus: Produces change in variable.
Change detected by receptor.
Input: Information sent along afferent pathway to control center.
Output: Information sent along efferent pathway to activate effector.
Response: Effector feeds back to influence magnitude of stimulus and returns variable to homeostasis.

Additional info: The control center is often the brain, which processes information and sends instructions to effectors (muscles or glands).

Negative Feedback

Negative feedback shuts off the original stimulus or reduces its intensity. Most homeostatic control mechanisms use negative feedback.

Positive Feedback

Positive feedback increases the original stimulus to push the variable farther. Reaction occurs at a faster rate. In the body, positive feedback occurs in blood clotting and childbirth.

Special Terminology and Anatomical Position

Special terminology is used to prevent misunderstanding. Exact terms are used for:

Position
Direction
Regions
Structures

Anatomical Position

Body is standing
Feet are parallel
Arms are hanging at sides
Palms facing forward

Orientation and Directional Terms

Directional terms are used to describe the locations of structures in relation to other structures or locations in the body.

Term	Definition	Example
Superior	Toward the head end or upper part	The forehead is superior to the nose
Inferior	Away from the head end or toward the lower part	The navel is inferior to the breastbone
Anterior	Toward or at the front of the body	The breastbone is anterior to the spine
Posterior	Toward or at the back side; behind	The heart is posterior to the breastbone

Term	Definition	Example
Medial	Toward or at the midline; on inner side	The heart is medial to the arm
Lateral	Away from the midline; on outer side	The arms are lateral to the chest
Intermediate	Between a medial and lateral structure	The armpit is intermediate between the breastbone and shoulder
Proximal	Close to the origin or point of attachment to body trunk	The elbow is proximal to the wrist
Distal	Farther from the origin or point of attachment to trunk	The knee is distal to the thigh