Unit 2: Body Structures

For all your body's needs!


The body is made up of many levels of both function and structure. Each level contributes to the one higher than its own level. These levels are as follows from the most basic to the most complex:


Cells are the most basic unit of life and can complete all the activities of life. They can make and store energy, remove waste, and reproduce. The are made of a membrane, a nucleus, and cytoplasm. The study of cells is called cytology.

Cell Membrane and Cytoplasm

The cell membrane is a thin barrier that completely surrounds the cell. It is semipermeable, which allows for somethings to pass freely through it, while effectively blocking others. It also has the job of holding in the cytoplasm or a goo-like substance that is made of water and other various solvents. It holds the structures that make up the cell.


The nucleus is the part of the cell that carries DNA. DNA makes up genes which control unique characteristics . The nucleus also controls metabolism, growth, and reproduction.


Groups of cells that perform the same type of job are called tissues. There are over 200 cell types, but only 4 main tissue types. The four types are as follows
Epithelial: Covers and lines things, made of layers or sheets of overlapping cells

Connective: Connects and supports other tissues and organs

Muscle: Just as it sounds, it makes up muscle

Nervous: Sends receives, and intakes electrical signals.


Organs perform specialized functions and are made of at least two different types of tissues. They are all over the body and have very different jobs.


A system is made up of organs and other elements that all work together, or are similar in function. All parts of the system have their own duty, but they come together in some way to achieve the overall goal of the system.


The highest level of organization, organism, is a living thing. It is made of all other things in levels of organization and is capable of independent existence.

Body Planes

Midsagittal (Median): Right and left halves

Coronal (Frontal): Anterior (ventral) and posterior (dorsal) aspects

Transverse (Horizontal): Superior (upper) and inferior (lower) aspects

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Directional Terms

Abduction: Movement away from the midline of the body

Adduction: Movement toward the midline of the body

Medial: Pertaining to the midline of the body

Lateral: Pertaining to the side

Superior: Toward the head or upper portion

Inferior: Away from the head, or toward the lower portion

Proximal: Nearer to the center or origin

Distal: Further from the center or origin

Anterior: Near the front of the body

Posterior: Near the back of the body

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Common Combining Forms

Cyt/o: Cell

Hist/o: Tissue

Kary/o: Nucleus

Anter/o: Anterior

Caud/o: Tail

Crani/o: Skull

Dist/o: Far

Dors/o: Back

Lumb/o: Loins

Gastr/o: Stomach

Leuk/o: White

Xanth/o: Yellow

Common Suffixes

-logy: Study of

-genisis: Forming

-gnosis: Knowing

-gram: Record

-graph: Instrument for recording

-pathy: Disease

-metry: Act of measuring

Common Prefixes

Ab-: Away from

Ad-: Toward

Infra-: Below

Hetero-: Different

Homeo-: Same

Peri-: Around


Trans-: Across

Ultra-: Excess