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Chapter 1

An Introduction to the Structure and

Function of the Body

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Objectives

• Define the terms anatomy and

physiology

• List and discuss in order of increasing

complexity the levels of organization of

the body

• Define the term anatomical position

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Objectives

• List and define the principal directional

terms and sections (planes) used in

describing the body and the relationship

of body parts to one another

• List the nine abdominopelvic regions

and the abdominopelvic quadrants

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Objectives

• List the major cavities of the body and

the subdivision of each

• Discuss and contrast the axial and the

appendicular subdivisions of the body.

Identify a number of specific anatomical

regions in each area.

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Objectives

• Explain the meaning of the term

homeostasis and give an example of a

typical homeostatic mechanism

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Structural Levels of Organization

• Organization is the most important characteristic of body structure

• The body as a whole is a unit constructed of the following smaller units:– Atoms and molecules—chemical level

– Cells—the smallest structural units; organizations of various chemicals

– Tissues—organizations of similar cells

– Organs—organizations of different kinds of tissues

– Systems—organizations of many different kinds of organs

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Anatomical Position

• Reference position in which the body is

standing erect with the feet slightly apart

and arms at the sides with palms turned

forward

• Anatomical position gives meaning to

directional terms

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Anatomical Directions

• Superior—toward the head, upper,

above

• Inferior—toward the feet, lower, below

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Anatomical Directions

• Anterior—front, in front of (same as

ventral in humans)

• Posterior—back, in back of (same as

dorsal in humans)

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Anatomical Directions

• Medial—toward the midline of a

structure

• Lateral—away from the midline or

toward the side of a structure

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Anatomical Directions

• Proximal—toward or nearest the trunk,

or nearest the point of origin of a

structure

• Distal—away from or farthest from the

trunk, or farthest from a structure’s point

of origin

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Anatomical Directions

• Superficial—nearer the body surface

• Deep—farther away from the body

surface

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Planes or Body Sections

• Sagittal plane—lengthwise plane that divides a structure into right and left sections

• Midsagittal—sagittal plane that divides the body into two equal halves

• Frontal (coronal) plane—lengthwise plane that divides a structure into anterior and posterior sections

• Transverse plane—horizontal plane that divides a structure into upper and lower sections

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Body Cavities

• Ventral cavity

– Thoracic cavity

• Mediastinum—midportion of thoracic cavity;

heart and trachea located in mediastinum

• Pleural cavities—right lung located in right

pleural cavity; left lung in left pleural cavity

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Body Cavities

• Ventral cavity

– Abdominopelvic cavity

• Abdominal cavity contains stomach, intestines,

liver, gallbladder, pancreas, and spleen

• Pelvic cavity contains reproductive organs,

urinary bladder, and lowest part of intestine

• Abdominopelvic regions

– Nine regions

– Four quadrants

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Body Cavities

• Dorsal cavity

– Cranial cavity contains brain

– Spinal cavity contains spinal cord

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Body Regions

• Axial region—head, neck, and torso or

trunk

• Appendicular region—upper and lower

extremities

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The Balance of Body Functions

• Survival of the individual and of the genes that make up the body is of the utmost importance

• Survival depends on the maintenance or restoration of homeostasis (relative constancy of the internal environment)– The body uses negative feedback loops and, less

often, positive feedback loops to maintain or restore homeostasis

– Feedback loops involve a sensor, a control center, and an effector

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The Balance of Body Functions

• All organs function to maintain

homeostasis

• Ability to maintain balance of body

functions is related to age: peak

efficiency occurs during young

adulthood; diminishing efficiency occurs

after young adulthood