Outline Summary

Scientific method
A. Science involves logical inquiry based on experimentation and can use a variety of methods (Figure 1-1)

1. Hypothesis—idea or principle to be tested in experiments
2. Experiment—series of tests of a hypothesis; a controlled experiment eliminates biases or outside influences
3. Theory or law—a hypothesis that has been supported by experiments and thus shown to have a high degree of confidence

B. The process of science is active and changing as new experiments add new knowledge

Levels of organization
A. Organization is the most important characteristic of body structure
B. The body as a whole (organism) is a unit constructed of the following smaller units (Figure 1-2):

1. Atoms and molecules—chemical level
2. Cells—the smallest structural units; organizations of various chemicals
3. Tissues—organizations of similar cells
4. Organs—organizations of different kinds of tissues
5. Systems—organizations of many different kinds of organs
6. Organism—organization of all systems together, forming a whole body

C. Microbiome—set of interacting communities of bacteria and other microorganisms that inhabit the human body; influences normal body function

Anatomical position
A. Reference position in which the body is standing erect with the feet slightly apart and arms at the sides with palms turned forward (Figure 1-3)
B. Anatomical position gives meaning to directional terms
C. Terms that describe the body not in anatomical position

1. Supine—lying face upward
2. Prone—lying face downward

Anatomical directions
A. Commonly used directional terms

1. Superior—toward the head, upper, above
2. Inferior—toward the feet, lower, below
3. Anterior—front, in front of (same as ventral in humans)
4. Posterior—back, in back of (same as dorsal in humans)
5. Medial—toward the midline of a structure
6. Lateral—away from the midline or toward the side of a structure
7. Proximal—toward or nearest the trunk, or nearest the point of origin of a structure
8. Distal—away from or farthest from the trunk, or farthest from a structure’s point of origin
9. Superficial—nearer the body surface
10. Deep—farther away from the body surface

B. Anatomical compass rosette—indicator of anatomical directions in an illustration that uses abbreviated directional terms

Planes of the body (figure 1-4)

A. Sagittal plane—lengthwise plane that divides a structure into right and left sections
B. Midsagittal—sagittal plane that divides the body into two equal halves
C. Frontal (coronal) plane—lengthwise plane that divides a structure into anterior and posterior sections
D. Transverse plane—horizontal plane that divides a structure into upper and lower sections
E. Oblique plane—any plane that is not parallel to any of the planes listed above, thus producing a slanted section

Body cavities (figure 1-5, table 1-1)
A. Dorsal cavities

1. Cranial cavity contains brain
2. Spinal cavity contains spinal cord

B. Ventral cavities

1. Thoracic cavity

a. Mediastinum—midportion of thoracic cavity; heart and trachea located in mediastinum
b. Pleural cavities—right lung located in right pleural cavity, left lung in left pleural cavity

2. Abdominopelvic cavity
a. Abdominal cavity contains stomach, intestines, liver, gallbladder, pancreas, and spleen
b. Pelvic cavity contains reproductive organs, urinary bladder, and lowest part of intestine
c. Abdominopelvic subdivisions

(1) Four abdominopelvic quadrants (Figure 1-6)
(2) Nine abdominopelvic regions (Figure 1-7)

C. Organs of the major body cavities can be seen in Figure 1-8 and are also referenced in Table

Body regions (figure 1-9, table 1-2)
A. Axial region—head, neck, and torso or trunk
B. Appendicular region—upper and lower extremities (limbs)
C. Body structure and function vary among individuals and also throughout an individual’s lifespan; atrophy (decrease in size) occurs when an organ is not used

Balance of body functions
A. Survival of the individual and of the genes that make up the body is of the utmost importance
B. Survival depends on the maintenance or restoration of homeostasis (relative constancy of the internal environment)

1. The internal environment is a fluid that must be kept stable by the operation of various organ systems (Figure 1-10)
2. The body uses stabilizing negative feedback loops (Figure 1-11) and, less often, amplifying positive feedback loops (Figure 1-12) to maintain or restore homeostasis
3. Feedback loops involve a sensor, a control center, and an effector
4. Negative feedback loops can turn into positive feedback loops during injury or disease, possibly causing a deadly shift in body function

C. All organs function to maintain homeostasis
D. Ability to maintain balance of body functions is related to age; peak efficiency occurs during young adulthood, diminishing efficiency occurs after young adulthood