Introduction to Anatomy & Physiology: Structural Organization and Body Systems

Chapter 1: Introduction to Anatomy & Physiology

What is Anatomy?

Anatomy is the study of the structure of body parts and their relationships to one another. The term comes from the Greek "to cut apart." Anatomy focuses on concrete structures that can be seen, felt, and examined closely.

• Gross or Macroscopic Anatomy: Study of large, visible structures (e.g., organs, muscles).

• Regional Anatomy: Examines all structures in a specific area of the body (e.g., head, chest).

• Systemic Anatomy: Looks at one organ system at a time (e.g., skeletal, muscular, nervous systems).

• Surface Anatomy: Studies internal structures as they relate to the overlying skin (e.g., muscles seen on a bodybuilder).

• Microscopic Anatomy: Deals with structures too small to be seen with the naked eye (e.g., cytology, histology).

What is Physiology?

Physiology is the study of the function of body parts and how they work to carry out life-sustaining activities. Physiology is often explained in terms of underlying anatomy.

• Examples: Neurophysiology (nervous system), Cardiovascular physiology (heart and blood vessels).

Anatomy and Physiology are Inseparable

• Function always reflects structure.

• What a structure can do depends on its specific form.

• Principle of Complementarity: Structure and function are closely related (e.g., bones support because they contain hard minerals).

Levels of Structural Organization

From the smallest chemical level to the whole organism, the body is organized into hierarchical levels:

Level	Description
Chemical	Atoms, molecules, organelles
Cellular	Cells and their organelles
Tissue	Groups of similar cells
Organ	Two or more tissue types working together
Organ System	Organs working closely together
Organismal	All organ systems combined to make the whole organism

Necessary Life Functions

• Maintaining boundaries

• Movement

• Responsiveness

• Digestion

• Metabolism

• Excretion

• Reproduction

• Growth

Maintaining Boundaries

• Separation between internal and external environments must exist.

• Plasma membranes separate cells; skin separates organism from environment.

Movement

• Muscular system allows movement of body parts and substances (e.g., blood, food).

Responsiveness (Excitability)

• Ability to sense and respond to stimuli (e.g., withdrawal reflex, control of breathing rate).

Digestion

• Breakdown of ingested foodstuffs, followed by absorption of simple molecules into the blood.

Metabolism

• All chemical reactions in body cells.

• Includes catabolism (breakdown of molecules) and anabolism (synthesis of molecules).

Excretion

• Removal of wastes from metabolism and digestion (e.g., urea, carbon dioxide, feces).

Reproduction

• Cellular level: division of cells for growth or repair.

• Organismal level: production of offspring.

Growth

• Increase in size of a body part or organism.

Organ System Overview

There are 11 organ systems that work together to maintain life (homeostasis):

System	Main Organs	Functions
Integumentary	Skin, hair, nails	Protection, temperature regulation, vitamin D synthesis, excretion, sensation
Skeletal	Bones, joints	Support, protection, movement, blood cell production, mineral storage
Muscular	Skeletal muscles	Movement, manipulation, facial expression, posture, heat production
Nervous	Brain, spinal cord, nerves	Fast-acting control, response to stimuli
Endocrine	Glands (pituitary, thyroid, etc.)	Slow-acting control, hormone secretion, regulation of growth, reproduction, metabolism
Cardiovascular	Heart, blood vessels	Transport of blood, oxygen, nutrients, wastes, hormones
Lymphatic/Immune	Lymph nodes, vessels, spleen, tonsils	Return of fluid to blood, immunity, debris disposal
Respiratory	Nasal passages, pharynx, larynx, trachea, bronchi, lungs	Gas exchange (O2 in, CO2 out)
Digestive	Mouth, esophagus, stomach, intestines, liver, pancreas	Breakdown and absorption of food, elimination of wastes
Urinary	Kidneys, ureters, bladder, urethra	Elimination of nitrogenous wastes, water/electrolyte/acid-base balance
Reproductive	Male: testes, penis; Female: ovaries, uterus, vagina	Production of offspring

Survival Needs

• Nutrients (carbohydrates, proteins, fats, minerals, vitamins)

• Oxygen (for cellular respiration)

• Water (most abundant chemical in the body)

• Normal body temperature (37°C or 98.6°F)

• Appropriate atmospheric pressure (for gas exchange in lungs)

Homeostasis

Homeostasis is the body's ability to maintain stable internal conditions despite external changes. It is maintained primarily by the nervous and endocrine systems.

• Involves continuous monitoring and regulation of variables (e.g., temperature, pH, blood pressure, glucose).

• Homeostatic control mechanisms involve a receptor (sensor), control center (brain/spinal cord), and effector (muscle/gland).

Feedback Mechanisms

• Negative Feedback: Most common; response reduces or shuts off original stimulus (e.g., regulation of body temperature, blood glucose).

• Positive Feedback: Response enhances or exaggerates original stimulus (e.g., labor contractions, blood clotting).

Language of Anatomy

Anatomical Position

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

Directional Terms

Term	Definition	Example
Superior (cranial)	Above; higher	The heart is superior to the liver
Inferior (caudal)	Below; lower	The liver is inferior to the lungs
Anterior (ventral)	Toward the front	The trachea is anterior to the esophagus
Posterior (dorsal)	Toward the back	The spine is posterior to the esophagus
Medial	Toward the midline	The heart is medial to the lungs
Lateral	Away from the midline	The ears are lateral to the nose
Proximal	Closer to trunk or point of origin	The knee is proximal to the foot
Distal	Farther from trunk or point of origin	The fingers are distal to the elbow
Superficial	Toward the surface	The skin is superficial to the lungs
Deep	Within; interior to	The lungs are deep to the ribs

Body Divisions

• Axial: Head, neck, trunk

• Appendicular: Limbs (arms and legs)

Key Equations

• Cellular Respiration:

$C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + ATP + \text{heat}$

Summary Table: Levels of Organization

Level	Example
Chemical	Atoms, molecules (e.g., water, glucose)
Cellular	Muscle cell, neuron
Tissue	Muscle tissue, nervous tissue
Organ	Heart, liver
Organ System	Cardiovascular system
Organismal	Human being

Additional info: Some explanations and examples have been expanded for clarity and completeness based on standard Anatomy & Physiology curriculum.