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Chapter 1Chapter 1

An Introduction to the Structure and

Function of the Body

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ObjectivesObjectives

• 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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ObjectivesObjectives

• List and define the principal directional

terms and sections (planes) used in

describing the body and the relationshipof body parts to one another 

• List the nine abdominopelvic regions

and the abdominopelvic quadrants

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ObjectivesObjectives

• 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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ObjectivesObjectives

• Explain the meaning of the term

homeostasis and give an example of a

typical homeostatic mechanism

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Structural Levels of OrganizationStructural Levels of Organization

• Organization is the most importantcharacteristic 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 PositionAnatomical Position

• Reference position in which the body is

standing erect with the feet slightly

apart and arms at the sides with palmsturned forward

• Anatomical position gives meaning to

directional terms

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Anatomical DirectionsAnatomical Directions

• Superior—toward the head, upper,

above

• Inferior—toward the feet, lower, below

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Anatomical DirectionsAnatomical Directions

• Anterior—front, in front of (same as

ventral in humans)

• Posterior—back, in back of (same asdorsal in humans)

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Anatomical DirectionsAnatomical 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 DirectionsAnatomical 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 DirectionsAnatomical Directions

• Superficial—nearer the body surface

• Deep—farther away from the body

surface

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Planes or Body SectionsPlanes or Body Sections

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

• Midsagittal—sagittal plane that divides thebody into two equal halves• Frontal (coronal) plane—lengthwise plane

that divides a structure into anterior andposterior sections

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

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Body CavitiesBody 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 CavitiesBody 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 RegionsBody Regions

• Axial region—head, neck, and torso or 

trunk

• Appendicular region—upper and lower extremities

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The Balance of Body FunctionsThe Balance of Body Functions

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

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

often, positive feedback loops to maintain or restorehomeostasis

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

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The Balance of Body FunctionsThe Balance of Body Functions

• All organs function to maintain

homeostasis

• Ability to maintain balance of bodyfunctions is related to age: peak

efficiency occurs during young

adulthood; diminishing efficiency occursafter young adulthood