Body Structure and Directional Terminology

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Body Structure and Directional Terminology

ICD-10-CM Example from Tabular

Organization of the Human Body

The human body and its general state of health and disease may be understood by studying the various body systems, such as the digestive and respiratory systems. Each body system is composed of different organs, such as the stomach and lungs. These organs are made up of combinations of tissues, such as epithelial and muscular tissue, which in turn are composed of various cells that have very specialized functions.

All of these levels of organization are involved in a continual process of sensing and responding to conditions in the organism’s environment. A negative change at one level of one system may cause a reaction throughout the entire body. Homeostasis is the normal dynamic process of balance needed to maintain a healthy body. When the body can no longer compensate for trauma or pathogens, disease, disorder, and dysfunction result.


The smallest unit of the human body is the cell. Although there are a number of different types of cells, all of them share certain characteristics, one of them being metabolism. Metabolism is the act of converting energy by continually building up substances by anabolism and breaking down substances by catabolism for use by the body. Metabolism can be described as an equation:

< ?xml:namespace prefix = "mml" />Metabolism=Anabolism+Catabolism


See Fig. 2-1 for an illustration of a cell and the corresponding table below for a brief description of the pictured organelles and their functions.

Cell Parts

Cell Part Word Origin Function
cytoplasm cyt/o cell
-plasm formation
Holds the organelles of the cell.
lysosome lys/o dissolving
-some body
Organelle that serves a digestive function for the cell.
ribosome rib/o ribose
-some body
Site of protein formation; contains RNA.
mitochondrion (pl. mitochondria) mitochondri/o mitochondria
-on structure
Converts nutrients to energy in the presence of oxygen.
nucleus (pl. nuclei) nucle/o nucleus
-us structure
Control center of cell; contains DNA, which carries genetic information.


There are four major categories of tissues. Within each type, the tissue either supports (stromal tissue) or does the actual work (parenchymal tissue) of the organ. For example, parenchymal nerve cells are the neurons that conduct the nervous impulse. Neuroglia are stromal nerve cells that enhance and support the functions of the nervous system. The four types of tissue include the following:

Epithelial: acts as an internal or external covering for organs, for example, the outer layer of the skin or the lining of the digestive tract. Note that the derivation of the term includes a combining form for the nipple (thel/e). Originally the term epithelium was used to describe the membrane covering the nipple. Later, the usage was expanded to include all surface membranes, whether on the skin or mucosal membrane surfaces, that communicate with the outside of the body.

Connective: includes a variety of types, all of which have an internal structural network. Examples include bone, blood, and fat.

Muscular: includes three types: heart muscle, skeletal muscle, and visceral muscle, all of which share the unique property of being able to contract and relax.

Nervous: includes cells that provide transmission of information to regulate a variety of functions, for example, neurons (nerve cells).

When tissue is destroyed by disease or trauma, the possibility of tissue replacement may be an option. Autologous tissue is that which is taken from one part of an individual’s body and is transplanted to another location. Auto- means “self.” An example would be a vein that is used to bypass a blocked coronary artery. If nonautologous tissue is used, it would mean that it is not from one’s self, but from another human. A synonym for nonautologous is allogenic, this time referring to being produced by a different human being. Allo- means “different.” Zooplastic tissue is that which is derived from an animal, for example, a cow or pig heart valve that is used to temporarily replace a structure until human donor tissue is available. Zo/o means “animal.” If tissue is syngeneic, as in the case of identical twins, it refers to a genetically identical individual. Syn- means “together or joined,” as in the sharing of the same DNA. Synonyms for the term syngeneic are isoplastic, isogeneic, and isologous. The combining form is/o means “equal.” Note that the synonyms use all of the previous suffixes: -plastic, -geneic, and -logous.


Organs, also referred to as viscera (sing. viscus), are arrangements of various types of tissue that accomplish specific purposes. The heart, for example, is made up of muscle tissue, called myocardium, and it is lined with epithelial tissue known as endocardium. Organs are grouped within body systems but do have specific terms to describe their parts.

Parts of Organs

Organs can be divided into parts and have a set of terms that describe these various parts.

Parts of Organs

  Term Combining Form Definition

apex apic/o The pointed extremity of a conical structure (pl. apices).

body (corporis) corpor/o,
The largest or most important part of an organ.

fornix fornic/o Any vaultlike or arched structure (pl. fornices).

fundus fund/o The base or deepest part of a hollow organ that is farthest from the mouth of the organ (pl. fundi).

hilum hil/o Recess, exit, or entrance of a duct into a gland, or of a nerve and vessels into an organ (pl. hila).

lumen lumin/o The space within an artery, vein, intestine, or tube (pl. lumina).

sinus sin/o, sinus/o A cavity or channel in bone, a dilated channel for blood, or a cavity that permits the escape of purulent (pus-filled) material (pl. sinuses). Antrum (pl. antra) and sinus are synonyms.

vestibule vestibul/o A small space or cavity at the beginning of a canal.





Body Systems

The organs of the body systems work together to perform certain defined functions. For example, movement is a function of the musculoskeletal system. Although each system has a number of functions, one must remember that the systems interact, and problems with one system can affect the function of other systems. For example, in the condition called secondary hypertension, disease in one body system (usually the lungs) causes a pathologic increase in blood pressure in the cardiovascular system. This hypertensive pressure is secondary to the primary cause (lung disease). Once the disorder of the initial system resolves, the hypertension disappears.

The following table lists each body system and its function.

Body Systems

Body System Functions
musculoskeletal Support, movement, protection
integumentary Cover and protection
gastrointestinal Nutrition
urinary Elimination of nitrogenous waste
reproductive Reproduction
blood/lymphatic/immune Transportation of nutrients/waste, protection
cardiovascular Transportation of blood
respiratory Delivers oxygen to cells and removes carbon dioxide
nervous/behavioral Receive/process information
special senses (eye and ear) Information gathering
endocrine Effects changes through chemical messengers


Combining Forms for Body Organization

Meaning Combining Form
blood hem/o, hemat/o
bone oste/o, osse/o
breakdown, dissolve lys/o
cell cyt/o, cellul/o
epithelium epitheli/o
fat adip/o, lip/o
heart cardi/o
heart muscle myocardi/o
juice chym/o
muscle my/o, muscul/o
nerve neur/o
nipple thel/e
nucleus kary/o, nucle/o
organ, viscera organ/o, viscer/o
same home/o
stroma strom/o
system system/o
to throw, throwing bol/o
tissue hist/o

Prefixes for Body Organization

Prefix Meaning
ana- up, apart, away
cata- down
en- in
endo- within
epi- above, upon
meta- beyond, change
para- near, beside, abnormal

Suffixes for Body Organization

Suffix Meaning
-al, -ous pertaining to
-ia, -ism condition, state of
-on structure
-plasm formation
-some body
-stasis controlling, stopping
-um structure, thing, membrane
-us structure

Specialties/Specialists and General Terms

The levels of organization of the body are accompanied by a number of specialties and their associated specialists.
Term Word Origin Definition
cytology cyt/o cell
-logy study of
The study of the cells. A cytologist specializes in the study of the cell. The suffix -logist means “one who specializes in the study of.”
histology hist/o tissue
-logy study of
The study of tissues. A histologist specializes in the study of tissues.
anatomy ana- up, apart, away
-tomy cutting
To cut apart, the study of the structure of the body. An anatomist specializes in the structure of the body.
physiology physi/o growth
-logy study of
The study of growth; the study of the function of the body. A physiologist specializes in the study of the function of the body.
pathology path/o disease
-logy study of
The study of disease. A pathologist specializes in the study of disease.
biopsy bi/o life, living
-opsy viewing
Process of viewing living tissue that has been removed for the purpose of diagnosis and/or treatment.
necropsy necr/o death, dead
-opsy viewing
Process of viewing dead tissue.
autopsy auto- self
-opsy viewing
Process of viewing by self; term commonly used to describe the examination of a dead body to determine cause(s) of death.



Anatomical Position and Surface Anatomy

Now that you understand the levels of organization of the body, you need the terms that describe locations, positions, and directions on the body. A standard frame of reference, the anatomical position, is the position in which the body stands erect with face forward, arms at the sides, palms forward, with toes pointed forward. This position is used to describe the surface anatomy of the body, both front (ventral) and back (dorsal). Figure 2-2 shows the anatomical position, both front and back, and is labeled with all the surface anatomy labels you will encounter throughout this text.

Ventral Surface Anatomy Terms (Head and Neck)

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